Artykuły w czasopismach: „COMPRESSOR BLADES DETERIORATION”

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Gilge, Philipp, Andreas Kellersmann, Jens Friedrichs i Jörg R. Seume. "Surface roughness of real operationally used compressor blade and blisk". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, nr 14 (9.05.2019): 5321–30. http://dx.doi.org/10.1177/0954410019843438.

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Deterioration of axial compressors is in general a major concern in aircraft engine maintenance. Among other effects, roughness in high-pressure compressor reduces the pressure rise and thus efficiency, thereby increasing the specific fuel consumption of an engine. Therefore, it is important to improve the understanding of roughness on compressor blading and their impact on compressor performance. To investigate the surface roughness of rotor blades of a compressors, different stages of an axial high-pressure compressor and a first-stage blisk (BLade–Integrated–dISK) of a regional aircraft engine is measured by a three-dimensional laser scanning microscope. Fundamental types of roughness structures can be identified: impacts in different sizes, depositions as isotropically distributed single elements with steep flanks and anisotropic roughness structures direct approximately normal to the flow direction. To characterise and quantify the roughness structures in more detail, roughness parameters were determined from the measured surfaces. The quantification showed that the roughness height varies through the compressor depending on the stage, position and the blade side. Overall complex roughness structures of different shape, height and size are detected regardless of the type of the blades.

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Li, Yan-Ling, i Abdulnaser I. Sayma. "Computational fluid dynamics simulations of blade damage effect on the performance of a transonic axial compressor near stall". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, nr 12 (10.10.2014): 2242–60. http://dx.doi.org/10.1177/0954406214553828.

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Gas turbine axial compressor blades may encounter damage during service for various reasons such as damage by debris from casing or foreign objects impacting the blades, typically near the rotor’s tip. This may lead to deterioration of performance and reduction in the surge margin. The damage breaks the cyclic symmetry of the rotor assembly; thus, computational fluid dynamics simulations have to be performed using full annulus compressor assembly. Moreover, downstream boundary conditions are unknown during rotating stall or surge, and simulations become difficult. This paper presents unsteady computational fluid dynamics analyses of compressor performance with tip curl damage. Computations were performed near the stall boundary. The primary objectives are to understand the effect of the damage on the flow behaviour and compressor stability. Computations for the undamaged rotor assembly were also performed as a reference case. A transonic axial compressor rotor was used for the time-accurate numerical unsteady flow simulations, with a variable area nozzle downstream simulating an experimental throttle. Computations were performed at 60% of the rotor design speed. Two different degrees of damage for one blade and multiple damaged blades were investigated. Rotating stall characteristics differ including the number of stall cells, propagation speed and rotating stall cell characteristics. Contrary to expectations, damaged blades with typical degrees of damage do not show noticeable effects on the global compressor performance near stall.

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Ghenaiet, A., S. C. Tan i R. L. Elder. "Prediction of an axial turbomachine performance degradation due to sand ingestion". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 219, nr 4 (1.06.2005): 273–87. http://dx.doi.org/10.1243/095765005x7592.

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Erosion of compressor blades due to operation in particulate environments is a serious problem for the manufacturers and users of industrial and aeronautical gas turbines, because of drastic degradations in performance, mostly through blunting of blade leading edges, reduction of chord and increase of tip clearance and surface roughness. This paper presents a numerical study to assess the effects of erosion by sand ingestion on blade geometry deterioration and the subsequent performance degradation. These computations were carried out for an axial turbomachine in steps; first, calculations of particle trajectories and erosion resulting from cumulative impacts by sand particles (MIL-E 5007E, 0–1000 μm) were carried out, then, the required data were used in the estimation of performance degradation based on a mean-line method that included Lieblein and Koch-Smith loss correlations, in addition to an erosion fault model derived from blade geometry deterioration. This global procedure was successfully validated upon an axial fan stage, and can be generalized easily to other axial compressor designs.

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Ma, Shuai, Jun Hu, Xuegao Wang i Jiajia Ji. "Effect of Non-Uniformity of Rotor Stagger Angle on the Stability of a Low-Speed Axial Compressor". Energies 15, nr 8 (7.04.2022): 2714. http://dx.doi.org/10.3390/en15082714.

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It is well known that variations in stagger angle between rotor blades affect compressor performance. In this paper, the stagger angle of blade No. 8 is increased or decreased by six degrees for non-uniformity, and the influence of rotor non-uniformity caused by the change in only one blade stagger angle on the performance and stability of the compressor is investigated. The experimental results show that whether the local rotor stagger angle increases or decreases, the compressor stability will deteriorate. If the stagger angle of blade No. 8 is reduced by six degrees, the flow coefficient at the stall point increases by 8.5%. If the stagger angle of blade No. 8 is increased by six degrees, the flow coefficient at the stall point increases by 1.5%. The reason for the deterioration of compressor stability caused by the local non-uniform rotor stagger angle is explored. When the stagger angle of rotor blade No. 8 deviates from the designed state, the load of blade No. 8 and the surrounding blades will change. The load on rotor blade No. 8 increases when the stagger angle decreases. In the near-stall condition, blade No. 8 becomes the “dangerous blade” that triggers the stall. As the stagger angle of rotor blade No. 8 increases, the load on blade No. 8 decreases. However, the load on blade No. 9 increases due to flow redistribution and blade No. 9 becomes a “dangerous blade” that triggers stall. The “dangerous blade” caused by the non-uniformity of stagger angle is the direct reason for the advance of the compressor rotating stall.

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Ngoret, Joshua K., i Venkata P. Kommula. "Role of Aluminide coating degradation on Inconel 713 LC used for Compressor Turbines (CT) of Short-haul Aircrafts". MRS Advances 3, nr 38 (2018): 2281–96. http://dx.doi.org/10.1557/adv.2018.207.

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ABSTRACTThis paper investigates the role degradation of protective diffusion aluminide coating on Inconel 713LC used for CT blades of short-haul aircraft fleet played in having the blades prematurely retired from service at 6378 hours, as opposed to their pre-set service time of 10000 hours. The blade samples were subjected to various examinations; X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyse at the; tips, airfoil, as well as the base, transverse and longitudinal, sectioned and unsectioned. As affirmed by both the transverse and longitudinal sections examinations, it was established that thermal attack leading to deterioration of the coating was greater at the tip and airfoils of the blades (the hotter zones) and lesser towards the bases (colder zones). As a result, severe degradation of the core material at the tips and airfoils compared to the bases and more prevalent at the leading edges than trailing edges at the tips. The results further suggest that both active outward Ni diffusion and inward Al diffusion can coexist during exploitation of the blades in service. The study illustrates the role played by the aluminide coating in early failure of CT blades with the aim of bettering the surface coatings and enhancing coating technologies, managing CT blade material monitoring as well as to give insights on advancing CT blades maintenance practices.

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Rendu, Quentin, i Loic Salles. "Development of a surrogate model for uncertainty quantification of compressor performance due to manufacturing tolerance". Journal of the Global Power and Propulsion Society 7 (4.08.2023): 257–68. http://dx.doi.org/10.33737/jgpps/168293.

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In gas turbines and jet engines, stagger angle and tip gap variations between adjacent blades lead to the deterioration of performance. To evaluate the effect of manufacturing tolerance on performance, a CFD-based uncertainty quantification analysis is performed in this work. However, evaluating dozens of thousands of rotor assembly through CFD simulations would be computationally prohibitive. A surrogate model is thus developed to predict compressor performance given an ordered set of manufactured blades. The model is used to predict the influence of tip gap and stagger angle variations on maximum isentropic efficiency. The results confirm that the best arrangement is obtained by minimizing the stagger angle variation between adjacent blades, and by maximizing the tip gap variation. Another finding is that the best arrangement yields the lowest variability, the range of maximum efficiency being 4 times sharper (resp. 2 times) than worst arrangement for stagger angle variations (resp. tip gap variations). Not measuring manufacturing tolerance, or not specifying any strategy for the blade arrangement, lead to variability as large as the worst arrangement.

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Hönen, Herwart, i Matthias Panten. "Recontouring of Jet Engine Compressor Blades by Flow Simulation". International Journal of Rotating Machinery 7, nr 5 (2001): 365–74. http://dx.doi.org/10.1155/s1023621x01000306.

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In modern jet propulsion systems the core engine has an essential influence on the total engine performance. Especially the high pressure compressor plays an important role in this scheme. Substantial factors here are losses due to tip clearance effects and aerodynamic airfoil quality. During flight operation the airfoils are subject to wear and tear on the leading edge. These effects cause a shortening of the chord length and the leading edge profiles become deformed. This results in a deterioration of the engine efficiency performance level and a reduced stall margin.The paper deals with the re-contouring of the leading edges of compressor airfoils by application of a new developed method for the profile definition. The common procedure of smoothing out the leading edges manually on a wheel grinding machine can not provide a defined contour nor a reproducible result of the overhaul process. In order to achieve optimized flow conditions in the compressor blade rows, suitable leading edge contours have to be defined for the worn airfoils. In an iterative process the flow behavior of these redesigned profiles is checked by numerical flow simulations and the shape of the profiles is improved. The following machining of the new defined leading edge contours is achieved on a grinding station handled by an appropriately programmed robot.

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Suder, K. L., R. V. Chima, A. J. Strazisar i W. B. Roberts. "The Effect of Adding Roughness and Thickness to a Transonic Axial Compressor Rotor". Journal of Turbomachinery 117, nr 4 (1.10.1995): 491–505. http://dx.doi.org/10.1115/1.2836561.

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The performance deterioration of a high-speed axial compressor rotor due to surface roughness and airfoil thickness variations is reported. A 0.025 mm (0.001 in.) thick rough coating with a surface finish of 2.54–3.18 rms μm (100–125 rms μin.) is applied to the pressure and suction surface of the rotor blades. Coating both surfaces increases the leading edge thickness by 10 percent at the hub and 20 percent at the tip. Application of this coating results in a loss in efficiency of 6 points and a 9 percent reduction in the pressure ratio across the rotor at an operating condition near the design point. To separate the effects of thickness and roughness, a smooth coating of equal thickness is also applied to the blade. The smooth coating surface finish is 0.254–0.508 rms μm (10–20 rms μin.), compared to the bare metal blade surface finish of 0.508 rms pm (20 rms μin.). The smooth coating results in approximately half of the performance deterioration found from the rough coating. Both coatings are then applied to different portions of the blade surface to determine which portions of the airfoil are most sensitive to thickness/roughness variations. Aerodynamic performance measurements are presented for a number of coating configurations at 60, 80, and 100 percent of design speed. The results indicate that thickness/roughness over the first 2 percent of blade chord accounts for virtually all of the observed performance degradation for the smooth coating, compared to about 70 percent of the observed performance degradation for the rough coating. The performance deterioration is investigated in more detail at design speed using laser anemometer measurements as well as predictions generated by a quasi-three-dimensional Navier–Stokes flow solver, which includes a surface roughness model. Measurements and analysis are performed on the baseline blade and the full-coverage smooth and rough coatings. The results indicate that adding roughness at the blade leading edge causes a thickening of the blade boundary layers. The interaction between the rotor passage shock and the thickened suction surface boundary layer then results in an increase in blockage, which reduces the diffusion level in the rear half of the blade passage, thus reducing the aerodynamic performance of the rotor.

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Huang, Song, Jinxin Cheng, Chengwu Yang, Chuangxin Zhou, Shengfeng Zhao i Xingen Lu. "Optimization Design of a 2.5 Stage Highly Loaded Axial Compressor with a Bezier Surface Modeling Method". Applied Sciences 10, nr 11 (1.06.2020): 3860. http://dx.doi.org/10.3390/app10113860.

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Due to the complexity of the internal flow field of compressors, the aerodynamic design and optimization of a highly loaded axial compressor with high performance still have three problems, which are rich engineering design experience, high dimensions, and time-consuming calculations. To overcome these three problems, this paper takes an engineering-designed 2.5-stage highly loaded axial flow compressor as an example to introduce the design process and the adopted design philosophies. Then, this paper verifies the numerical method of computational fluid dynamics. A new Bezier surface modeling method for the entire suction surface and pressure surface of blades is developed, and the multi-island genetic algorithm is directly used for further optimization. Only 32 optimization variables are used to optimize the rotors and stators of the compressor, which greatly overcome the problem of high dimensions, time-consuming calculations, and smooth blade surfaces. After optimization, compared with the original compressor, the peak efficiency is still improved by 0.12%, and the stall margin is increased by 2.69%. The increase in peak efficiency is mainly due to the rotors. Compared with the original compressor, for the second-stage rotor, the adiabatic efficiency is improved by about 0.4%, which is mainly due to the decreases of total pressure losses in the range of above 30% of the span height and 10%–30% of the chord length. Besides, for the original compressor, due to deterioration of the flow field near the tip region of the second-stage stator, the large low-speed region eventually evolves from corner separation into corner stall with three-dimensional space spiral backflow. For the optimized compressor, the main reason for the increased stall margin is that the flow field of the second-stage stator with a span height above 50% is improved, and the separation area and three-dimensional space spiral backflow are reduced.

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Kachan, O., i S. Ulanov. "Features of the process of hot extrusion of blanks of the rotor blades of a GTE compressor". Innovative Materials and Technologies in Metallurgy and Mechanical Engineering, nr 1 (14.09.2021): 41–46. http://dx.doi.org/10.15588/1607-6885-2021-2-7.

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Purpose. Improving the quality of manufacturing of blanks for compressor rotor blades by hot extrusion. Research methods and equipment. The research was carried out using a crank press with a force of 1000 kN, in split dies in accordance with a serial technological process. The dies were heated up to 150 ... 200 °С, to improve the work when extruding the blanks of the rotor blades made from the titanium alloy ВT8. The thickness of the copper coating was measured with an ИTMП-3 magnetic induction device with an error of ± 2 μm. X-ray spectral microanalysis was performed on an ISM-6360ALA scanning microscope. The billets were heated in an MП-2В furnace. Results. It has been established that the quality of blade blanks made of ВT8 titanium alloy obtained by hot extrusion is influenced by the state of the copper coating, which is preliminarily applied to the surface of the original blank. When the initial blanks are heated, copper is oxidized and in the temperature range of 250…700 °С the oxidation rate proceeds according to a linear pattern, and after 700…750 °С – according to a parabolic pattern. Oxidation of the copper coating occurs unevenly not only within one workpiece, but also within the batch, which leads to a decrease in durability and deterioration of the surface quality of the blade workpieces obtained by hot extrusion. Research carried out by X-ray spectral microanalysis of the copper coating revealed the presence of aluminum oxides of varying degrees of dispersion. The source of this material in the copper coating is caricature of corundum used in blowing into the surface of the billet, which is the reason for the appearance of scoring on the blade blank. It was also found that longitudinal marks on the blade are a consequence of the appearance of a matrix of tubercles (sagging) on the working surface of the die, caused by the adhesion of the deformable material of the blade to the base metal of the tool. Scientific novelty. The regularity of the influence of the heating temperature of the initial blank of the blade on the oxidation rate of the copper coating has been established. The mechanism of the influence of the oxidation of the copper coating and the adhesion of contacting materials during hot extrusion on the surface condition of the resulting blanks is disclosed. Practical value. The results obtained make it possible to improve the quality of the manufactured blanks of the compressor rotor blades by hot extrusion.

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Fu, Xi, Chao Ma, Jiewei Lin i Junhong Zhang. "Numerical Study on Vibration Response and Fatigue Damage of Axial Compressor Blade Considering Aerodynamic Excitation". Metals 11, nr 11 (15.11.2021): 1835. http://dx.doi.org/10.3390/met11111835.

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Axial compressor blades with a deformed initial torsion angle caused by aerodynamic excitation resonated at the working speed and changed the rule of fatigue damage accumulation. The fatigue life of a blade has a prediction error, even causing serious flight accidents if the effect of torque causing damage deterioration of the blade fatigue life is neglected. Therefore, in this paper, a uniaxial non-linear fatigue damage model was modified using the equivalent stress with torsional shear stress, and the proposed fatigue model including the torsional moment was used to study the compressor blade fatigue life. Then, the blade numerical simulation model was established to calculate the vibration characteristics under complex loads of airflow excitation and a rotating centrifugal force. Finally, the blade fatigue life under actual working conditions was predicted using the modified fatigue model. The results show that the interaction between centrifugal and aerodynamic loads affects the natural frequency, as the frequencies in modes dominated by bending deformation decreased whereas those dominated by torsional deformation increased. Furthermore, the blade root of the suction surface showed stress concentration, but there is an obvious difference of stress distribution and amplitude between the normal stress and the equivalent stress including torsional shear stress. The additional consideration of the torsional shear stress decreased the predicted fatigue life by 4.5%. The damage accumulation rate changes with the loading cycle, and it accelerates fast for the last 25% of the cycle, when the blade fracture may occur at any time. Thus, the aerodynamic excitation increased the safety factor of blade fatigue life prediction.

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Batcho, P. F., J. C. Moller, C. Padova i M. G. Dunn. "Interpretation of Gas Turbine Response Due to Dust Ingestion". Journal of Engineering for Gas Turbines and Power 109, nr 3 (1.07.1987): 344–52. http://dx.doi.org/10.1115/1.3240046.

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A measurement program currently underway at Arvin/Calspan Advanced Technology Center has been used in the evaluation of observed engine behavior during dust ingestion. The Pratt and Whitney TF33 turbofan and J57 turbojet were used in the investigation. Solid particle ingestion was found to erode the compressor blades and result in substantial performance deterioration. The engines were found to have increased susceptibility to surge at low power settings. The roles that anti-ice and intercompressor bleed airplay in surge avoidance are discussed. A discussion of the fuel controller behavior in a deteriorated engine and its effect during steady-state engine operation is also presented. Experimental data obtained during testing were compared to a predictive capability developed to describe deteriorated engine response. The effects of tip clearance, blade profile, and secondary flows were taken into account. The results show good agreement with experimentally observed engine behavior.

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Goeing, Jan, Hendrik Seehausen, Vladislav Pak, Sebastian Lueck, Joerg R. Seume i Jens Friedrichs. "Influence of combined compressor and turbine deterioration on the overall performance of a jet engine using RANS simulation and Pseudo Bond Graph approach". Journal of the Global Power and Propulsion Society 4 (22.12.2020): 296–308. http://dx.doi.org/10.33737/jgpps/131109.

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In this study, numerical models are used to analyse the influence of isolated component deterioration as well as the combination of miscellaneous deteriorated components on the transient performance of a high-bypass jet engine. For this purpose, the aerodynamic impact of major degradation effects in a high-pressure compressor (HPC) and turbine (HPT) is modelled and simulated by using 3D CFD (Computational Fluid Dynamics). The impact on overall jet engine performance is then modelled using an 1D Reduced Order Model (ROM). Initially, the HPC performance is investigated with a typical level of roughness on vanes and blades and the HPT performance with an increasing tip clearance. Subsequently, the overall performance of the jet engines with the isolated and combined deteriorated domains is computed by the in-house 1D performance tool ASTOR (AircraftEngine Simulation for Transient Operation Research). Degradations have a significant influence on the system stability and transient effects. In ASTOR, a system of differential equations including the equations of motion and further ordinary differential equations is solved. Compared to common ROMs, this enables a higher degree of accuracy. The results of temperature downstream of the high-pressure compressor and low-pressure turbine as well as the specific fuel composition and the HP rotational speed are used to estimate the degree and type of engine deterioration. However, the consideration of the system stability is necessary to analyse the characterisation in more detail. Finally, a simplified model which merges two engines with individual deteriorated domains into one combined deteriorated engine, is proposed. The simplified model predicts the performance of an engine which has been simulated with combined deteriorated components.

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Qi, Gong W., i X. Hong Zhang. "Effect of a volute on the unsteady flow in the vane diffuser of a centrifugal compressor". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 230, nr 8 (17.10.2016): 773–91. http://dx.doi.org/10.1177/0957650916673935.

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A volute is the only circumferential asymmetric component in a centrifugal compressor, and thus, it should account for the circumferential asymmetry of the flow in a vane diffuser. This study performs a transient numerical analysis to investigate the effect of a volute on the flow in the vane diffuser of a centrifugal compressor under three operating conditions (near-stall, middle, and high mass flow). We compare numerical and experimental performance of the compressor, including polytropic efficiency, total pressure ratio, and unsteady pressure on a diffuser vane. The numerical scheme is proven valid owing to the fact that the numerical and experimental results considerably agree well with each other. Under middle and high mass flow conditions, the time-averaged static pressure recovery and the total pressure loss coefficients for all the diffuser passages indicate that the performance of the passages near and upstream of the volute tongue is affected negatively by the volute, whereas that of the passages downstream of the volute tongue is less affected. Under near-stall condition, the performance of all the passages is disturbed, and the diffuser passage marked as DP 3 demonstrates the worst performance. Investigation on the time-averaged aerodynamic forces, loading, and pressure on the vanes yields results that are consistent with those of the investigation on the performance of the passages. The harmonics with 0.5 fb and fb, which are included in the unsteady loading and pressure on the pressure and suction sides of the vanes, are dominant, where fb is the impeller main and splitter blades passing frequency. Their amplitude values increase as mass flow deviates from the middle mass flow condition. Under middle and high mass flow conditions, the harmonic with 0.5 fb is affected more negatively because of the larger amplitude on the vanes near and upstream of the volute tongue than those downstream, whereas the harmonic with fb is less affected by the volute. Under the near-stall condition, the transient vorticity fields along with the harmonics of 0.5 fb and fb are investigated to evaluate the performance of the diffuser passages. DP 3, which is located at approximately 90° downstream of the volute tongue, suffers the strongest flow deterioration and is inferred to stall first. Further researches for designing more matching diffuser/volute combination will be performed by referring this study.

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Hamed, A., W. Tabakoff i D. Singh. "Modeling of Compressor Performance Deterioration Due to Erosion". International Journal of Rotating Machinery 4, nr 4 (1998): 243–48. http://dx.doi.org/10.1155/s1023621x98000207.

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This paper presents the results of a simulation of compressor performance deterioration due to blade erosion. The simulation at both design and off-design conditions is based on a mean line row by row model, which incorporates the effects of blade roughness and tip clearance. The results indicate a pronounced effect of blade erosion on the compressor adiabatic efficiency and a lesser effect on the pressure ratio. The loss in performance is mainly caused by the increased blade surface roughness and was highest at 100% speed.

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Tabakoff, W. "Compressor Erosion and Performance Deterioration". Journal of Fluids Engineering 109, nr 3 (1.09.1987): 297–306. http://dx.doi.org/10.1115/1.3242664.

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Aircraft engines operating in areas where the atmosphere is polluted by small solid particles are typical examples of jet engines operating under hostile atmospheric environment. The particles may be different kinds of sand, volcanic ashes or others. Under these conditions, the gas and particles experience different degrees of turning as they flow through the engine. This is mainly due to the difference in their inertia. This paper presents the results of an investigation of the solid particle dynamics through a helicopter engine with inlet particle separator. The particle trajectories are computed in the inlet separator which is characterized by considerable hub and tip contouring and radial variation in the swirling vane shape. The nonseparated particle trajectories are determined through the deswirling vanes and the five stage axial flow compressor. The results from this study include the frequency of particle impacts and the erosion distribution on the blade surfaces.

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Kellersmann, Andreas, Gerald Reitz i Jens Friedrichs. "Deterioration effects of coupled blisk blades". Journal of the Global Power and Propulsion Society 2 (10.10.2018): CKB8N6. http://dx.doi.org/10.22261/jgpps.ckb8n6.

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Performance degradation due to wear of high pressure compressors (HPC) is a major concern in aero-engine operation and maintenance. Among other effects especially erosion of airfoils leads to changed aerodynamic behavior and therefore to deterioration. These affects engine performance parameter like thrust specific fuel consumption (TSFC) and exhaust gas temperature (EGT). Reaching EGT-limit, the engine typically has to be overhauled during a shop visit to restore safety standards and performance. During state of the art shop visits, engines are repaired based on EGT-specifications. To further enhance the maintenance, tailored repairs for each jet engine based on engine history and operation conditions are necessary to take TSFC into account. To ensure such an effective maintenance, the aerodynamic behavior of deteriorated and repaired airfoils is the key factors. Therefore, geometric properties with high influence on aerodynamic performance have to be known. For blisks (BLade-Integrated-diSK) the approach of tailored maintenance will be even more complicated because the airfoil arrangement cannot be changed or individual airfoils cannot be replaced. Thus, the effects of coupled misshaped airfoils have a high significance. This study will present a Design of Experiments (DoE) for circumferential coupled HPC-airfoils to identify the geometric properties which lead to a reduction of performance. To focus on geometric variations, quasi3D (Q3D) simulations are taken out. Based on a sensitivity analysis, the thickness related parameters, the stagger angle as well as the max. profile camber thickness are identified as the most important parameters which are influencing adjacent airfoils and reduce the aerodynamic performance.

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Mao, Xiaochen, Bo Liu i Tianquan Tang. "Effect of casing aspiration on the tip leakage flow in the axial flow compressor cascade". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 232, nr 3 (3.08.2017): 225–39. http://dx.doi.org/10.1177/0957650917724598.

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Tip leakage flow is usually responsible for the deterioration of compressor performance and stability. The current paper conducts numerical simulations on the impact of casing aspiration on the axial compressor cascade performance. Three aspiration schemes with different chordwise coverage are studied and analyzed. It is found that the cascade performance can be effectively improved by the appropriate casing aspiration, and the optimum aspiration scheme should cover the area including the onset point of tip leakage vortex and its vicinity. The control mechanisms are different for the aspiration schemes located at different blade chord ranges. For the aspiration scheme covering the onset point of tip leakage vortex, the improvement of the cascade performance is mainly due to that the starting point of the tip leakage vortex is shifted downstream. The original tip leakage vortex structure is divided into two parts if the aspiration scheme is located behind the onset point of tip leakage vortex and the final control effect is the combination of the influence from the two different parts of tip leakage vortex. Additionally, the casing aspiration redistributes the blade loading along the chord near blade tip. The results of these investigations may offer guidance for the appropriate design of aspiration scheme in the future updated compressors and the overall total pressure loss coefficient caused by aspiration slot should be considered in the design process.

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Naeem, M. "Impacts of low-pressure (LP) compressor’s deterioration upon an aero-engine’s high-pressure (HP) turbine blade’s life consumption". Aeronautical Journal 110, nr 1106 (kwiecień 2006): 227–38. http://dx.doi.org/10.1017/s0001924000001202.

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AbstractSome in-service deterioration in any mechanical device, such as an aero-engine, is inevitable. As a result of experiencing a deterioration of efficiency and/or mass flow, an aero-engine will automatically adjust to a different set of operating characteristics; thereby frequently resulting in changes of rpm and/or turbine entry temperature in order to provide the same thrust. Rises in the turbine entry-temperatures and the high-pressure turbine’s rotational speed result in greater rates of creep and fatigue damage being incurred by the hot-end components and thereby higher engine’s life cycle costs. Possessing a better knowledge of the effects of engine deterioration upon the aircraft’s performance, as well as fuel and life usages, helps the users to take wiser management decisions and hence achieve improved engine utilisation. For a military aircraft, using a computer performance simulation, the consequences of low-pressure (LP) compressor’s deterioration upon an aero-engine high-pressure (HP) turbine blade’s life-consumption have been predicted.

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Liang, Dong, Donghai Jin i Xingmin Gui. "Investigation of Seal Cavity Leakage Flow Effect on Multistage Axial Compressor Aerodynamic Performance with a Circumferentially Averaged Method". Applied Sciences 11, nr 9 (27.04.2021): 3937. http://dx.doi.org/10.3390/app11093937.

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The seal cavity leakage flow has a considerable impact on the performance of the aeroengine, especially on the multistage compressor. Thus, a quasi-three-dimensional simulation program named CAM is developed basing on circumferentially averaged throughflow method. The program enables a rapid diagnosis for the performance degradation of multistage compressor caused by labyrinth wear. The coupling flow field between the seal cavity leakage flow and the main flow field at the root of the shrouded stator of a high-loading three-stage compressor with inlet guide vanes (IGV) was simulated by CAM and the results indicate that seal cavity leakage flow has a significant impact on the overall performance of the compressor. That is, for a 1% increase in the seal-tooth clearance-to-span ratio, the decrease in total pressure ratio was 2.6%, and the reduction in efficiency was 0.6%. Stage performance shows that the seal cavity leakage flow reduces the pressurization capacity of the current stator and the work capacity of the downstream rotor, but has little effect on the upstream blade row. Spanwise distribution of blade element performance shows that the leakage flow leads to an increased flow blockage near the hub, resulting in spanwise migration. The incidence of the stator and rear rotor then change through the entire span. The leakage flow leads to the flow blockage and migration and hence changes the incidence angle, which results in the deterioration of compressor performance.

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Sohail, Muhammad Umer, Hossein Raza Hamdani, Asad Islam, Khalid Parvez, Abdul Munem Khan, Usman Allauddin, Muhammad Khurram i Hassan Elahi. "Prediction of Non-Uniform Distorted Flows, Effects on Transonic Compressor Using CFD, Regression Analysis and Artificial Neural Networks". Applied Sciences 11, nr 8 (20.04.2021): 3706. http://dx.doi.org/10.3390/app11083706.

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Non-uniform inlet flows frequently occur in aircrafts and result in chronological distortions of total temperature and total pressure at the engine inlet. Distorted inlet flow operation of the axial compressor deteriorates aerodynamic performance, which reduces the stall margin and increases blade stress levels, which in turn causes compressor failure. Deep learning is an efficient approach to predict catastrophic compressor failure, and its stability for better performance at minimum computational cost and time. The current research focuses on the development of a transonic compressor instability prediction tool for the comprehensive modeling of axial compressor dynamics. A novel predictive approach founded by an extensive CFD-based dataset for supervised learning has been implemented to predict compressor performance and behavior at different ambient temperatures and flow conditions. Artificial Neural Network-based results accurately predict compressor performance parameters by minimizing the Root Mean Square Error (RMSE) loss function. Computational results show that, as compared to the tip radial pressure distortion, hub radial pressure distortion has improved the stability range of the compressor. Furthermore, the combined effect of pressure distortion with the bulk flow has a qualitative and deteriorator effect on the compressor.

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Shi, Yan, Wenguo Xiang i Shiyi Chen. "Research on Metal Supervision and Inspection Standards for Gas-steam Combined Cycle Units". E3S Web of Conferences 228 (2021): 01011. http://dx.doi.org/10.1051/e3sconf/202122801011.

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Domestic gas-steam combined cycle units start and stop frequently, and the load changes greatly, which accelerate the expansion of defects, such as fatigue, cracks, and organizational deterioration of metal components. In view of the problems caused by the material selection characteristics of gas-steam combined cycle units and the daily shutdown mode, several common typical cases of gas-steam combined cycle units are analyzed, such as compressor blade fatigue fracture, main steam combined valve body fatigue cracks, pipeline and pressure vessel weld fatigue cracks. As well, the gas-steam combined cycle unit metal supervision content and inspection emphasis are studied and supplemented.

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Shenouda, Emad F., Ian W. Nelson i Richard J. Nelson. "Anterior transvertebral transposition of the spinal cord for the relief of paraplegia associated with congenital cervicothoracic kyphoscoliosis". Journal of Neurosurgery: Spine 5, nr 4 (październik 2006): 374–79. http://dx.doi.org/10.3171/spi.2006.5.4.374.

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✓The authors describe a technique for the relief of spinal cord compression associated with congenital kyphoscoliosis. A 13-year-old girl with congenital cervicothoracic kyphoscoliosis had undergone in situ fusion; spastic paraparesis and bladder disturbance developed postoperatively. Spinal cord detethering and posterolateral decompression temporarily arrested the neurological deterioration; however, the patient’s condition then progressed to paraplegia with a partial sensory level at L-1. Imaging demonstrated persisting cord compression at the apex of the kyphotic curve. Transvertebral transposition of the spinal cord was performed using sagittal vertebrotomies, preserving the lateral aspects of the vertebral bodies, pedicles, and fusion mass. By 2 years postoperatively she had recovered normal sensation and good bladder function and was walking unaided. Transposition of the spinal cord may be used to relieve spinal cord compression associated with complex spinal deformities.

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MacLeod, J. D., V. Taylor i J. C. G. Laflamme. "Implanted Component Faults and Their Effects on Gas Turbine Engine Performance". Journal of Engineering for Gas Turbines and Power 114, nr 2 (1.04.1992): 174–79. http://dx.doi.org/10.1115/1.2906567.

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Under the sponsorship of the Canadian Department of National Defence, the Engine Laboratory of the National Research Council of Canada (NRCC) has established a program for the evaluation of component deterioration on gas turbine engine performance. The effect is aimed at investigating the effects of typical in-service faults on the performance characteristics of each individual engine component. The objective of the program is the development of a generalized fault library, which will be used with fault identification techniques in the field, to reduce unscheduled maintenance. To evaluate the effects of implanted faults on the performance of a single spool engine, such as an Allison T56 turboprop engine, a series of faulted parts were installed. For this paper the following faults were analyzed: (a) first-stage turbine nozzle erosion damage; (b) first-stage turbine rotor blade untwist; (c) compressor seal wear; (d) first and second-stage compressor blade tip clearance increase. This paper describes the project objectives, the experimental installation, and the results of the fault implantation on engine performance. Discussed are performance variations on both engine and component characteristics. As the performance changes were significant, a rigorous measurement uncertainty analysis is included.

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Wang, Ming-Yang, Zi-Liang Li, Sheng-Feng Zhao, Yan-Feng Zhang i Xin-Gen Lu. "Effects of Reynolds number and loading distribution on the aerodynamic performance of a high subsonic compressor airfoil". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 234, nr 8 (13.01.2020): 1069–83. http://dx.doi.org/10.1177/0957650919899541.

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The laminar-turbulent transition process on the compressor blade surface is often induced by the laminar separation flow at low Reynolds number ( Re). In the present study, numerical simulations were conducted to investigate the structure of the laminar separation bubble and its effects on the profile loss of a high subsonic compressor airfoil under different Re conditions, and the mechanism for the performance deterioration of compressor airfoil at low Re was clarified. Besides, the airfoil was redesigned to obtain a series of airfoils with different loading distributions, and the aerodynamic performance of these airfoils was compared and analyzed in detail. According to the simulation results, the laminar separation bubble mainly determined the loss generation process of a compressor airfoil. When Re decreased from 12 × 105 to 1.5 × 105, the laminar separation bubble on the suction surface grew thicker and the length was increased by 11.2% of the axial chord. As such, the reversed flow inside the laminar separation bubble became more obvious and the turbulence level downstream of the maximum thickness of laminar separation bubble was increased. Also, the growth in the turbulent boundary layer was enhanced, causing more serious flow blockage and wake mixing. According to the Denton's profile loss model, the larger trailing edge loss caused by the stronger displacement effect of laminar separation bubble was supposed to be the main reason for the performance deterioration of compressor airfoil under low Re conditions. The ultra-front loading distribution for airfoil has the possibility to suppress or even eliminate the negative effect of laminar separation bubble, and the profile loss was decreased by 26.7% at Re = 1.5 × 105; however, the less significant performance improvement was observed at some higher Re. Moreover, the ultra-front loaded airfoil was less sensitive to the inlet turbulence level and the superiority still holds even at some supercritical conditions.

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Bashir, Khurram, Christopher Y. Cai, Thomas A. Moore, John N. Whitaker i Mark N. Hadley. "Surgery for Cervical Spinal Cord Compression in Patients with Multiple Sclerosis". Neurosurgery 47, nr 3 (1.09.2000): 637–43. http://dx.doi.org/10.1097/00006123-200009000-00022.

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ABSTRACT OBJECTIVE The goal of this study was to investigate the clinical and paraclinical features, treatment, and outcomes of patients with multiple sclerosis (MS) and coexisting spinal cord compression secondary to either cervical spondylosis or cervical disc disease. Patients with MS commonly experience neurological disabilities that present as myelopathy associated with bladder dysfunction. For some patients with MS, however, this neurological deterioration may result from coexisting spinal cord compression attributable to either spondylosis or a herniated disc. Overlapping symptoms of the two conditions do not allow clear clinical determination of the underlying cause of worsening. METHODS Patients with MS who underwent cervical decompression surgery were selected. Medical records were retrospectively reviewed, to collect data on their pre- and postoperative clinical courses. RESULTS Nine women and five men with definite MS were selected for cervical decompression surgery to treat neurological deterioration considered to be at least partially attributable to spinal cord compression. The most common symptoms were progressive myelopathy (n = 13), neck pain (n = 11), and cervical radiculopathy (n = 10). Bladder dysfunction was notably absent among these patients with MS with moderate disabilities. Surgical intervention was frequently delayed because the neurological deterioration was initially thought to be attributable to MS. The majority of patients experienced either improvement or stabilization of their preoperative symptoms in the immediate postoperative period; three subjects (21%) maintained this improvement after a mean follow-up period of 3.8 years. No MS relapses, permanent neurological worsening, or serious complications resulting from surgery or general anesthesia were noted. CONCLUSION Carefully selected patients with MS and cervical spinal cord compression secondary to either spondylosis or disc disease may benefit from surgical decompression, with minimal associated morbidity. Clinical features (especially neck pain and cervical radiculopathy) and magnetic resonance imaging may assist clinicians in differentiating between the two conditions and may guide appropriate treatment without undue delay.

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Kleopa, Kleopas A., Leslie N. Sutton, Joseph Ong, Gihan Tennekoon i Albert E. Telfeian. "Conus medulla—cauda compression from nerve root hypertrophy in a child with Dejerine—Sottas syndrome: improvement with laminectomy and duraplasty". Journal of Neurosurgery: Spine 97, nr 2 (wrzesień 2002): 244–47. http://dx.doi.org/10.3171/spi.2002.97.2.0244.

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✓ This 7-year-old boy with Dejerine—Sottas syndrome caused by a mutation in the myelin protein zero gene began to suffer rapid deterioration with increasing leg weakness, loss of the ability to ambulate, and bowel and bladder incontinence. Magnetic resonance imaging of the spine revealed nerve root hypertrophy resulting in compression of the conus medullaris and cauda equina. Decompressive surgery was successful in reversing some of his deficits.

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Kurz, R., i K. Brun. "Degradation in Gas Turbine Systems". Journal of Engineering for Gas Turbines and Power 123, nr 1 (1.11.2000): 70–77. http://dx.doi.org/10.1115/1.1340629.

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Any prime mover exhibits the effects of wear and tear over time. The problem of predicting the effects of wear and tear on the performance of any engine is still a matter of discussion. Because the function of a gas turbine is the result of the fine-tuned cooperation of many different components, the emphasis of this paper is on the gas turbine and its driven equipment (compressor or pump) as a system, rather than on isolated components. We will discuss the effect of degradation on the package as part of a complex system (e.g., a pipeline, a reinjection station, etc.). Treating the gas turbine package as a system reveals the effects of degradation on the match of the components as well as on the match with the driven equipment. This article will contribute insights into the problem of gas turbine system degradation. Based on some detailed studies on the mechanisms that cause engine degradation, namely, changes in blade surfaces due to erosion or fouling, and the effect on the blade aerodynamics; changes in seal geometries and clearances, and the effect on parasitic flows; and changes in the combustion system (e.g., which result in different pattern factors), the effects of degradation will be discussed. The study includes a methodology to simulate the effects of engine and driven equipment degradation. With a relatively simple set of equations that describe the engine behavior, and a number of linear deviation factors which can easily be obtained from engine maps or test data, the equipment behavior for various degrees of degradation will be studied. A second model, using a stage by stage model for the engine compressor, is used to model the compressor deterioration. The authors have avoided to present figures about the speed of degradation, because it is subject to a variety of operational and design factors that typically cannot be controlled entirely.

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Datsenko, Vadym, i Ludmila Boyko. "Determining the influence of compressor flow path abrasive wear on the gas turbine engine characteristics". Eastern-European Journal of Enterprise Technologies 2, nr 1 (122) (28.04.2023): 12–24. http://dx.doi.org/10.15587/1729-4061.2023.275546.

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The operation of a gas turbine engine (GTE) in a dusty atmosphere leads to wear of the elements of the flowing part and, as a result, to a deterioration in its parameters and characteristics. Helicopter and tank gas turbine engines operating in a dusty atmosphere, as well as gas turbine units of compressor stations operated in areas with high dust concentrations, are subjected to the greatest wear. When operating GTE under such conditions, the compressor is subjected to stronger wear. In this regard, the task addressed in this paper is determining the effect of abrasive wear of the compressor on GTE parameters. To this end, a method for calculating the GTE characteristics is built, making it possible to take into account the effect of abrasive wear of the flow path and blade crowns of the compressor. Underlying the calculation method is a nonlinear mathematical model that makes it possible to describe the processes occurring in individual nodes and in the engine as a whole under stationary modes. A feature of this method is the two-dimensional description of the compressor in the engine system. The method reported here makes it possible to quickly estimate the effect of deviation of the geometric parameters of the flow path from the rated values on the characteristics of the compressor and engine as a whole. The geometric parameters of the degraded-out axial compressor were simulated on the basis of wear data. The parameters and characteristics of the degraded-out compressor, as well as the gas turbine engine as a whole, were calculated. It was found that with a given wear of the flow path of the compressor, the specific power of the engine decreased by 7.5 % while specific fuel consumption increased by 6.4 %, and the stability margin decreased by 11.1 % compared to the original ones. The results could be used to analyze and predict the operational efficiency of engines when they operate under conditions of high dustiness.

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Jhaveri, Subir N., Shivam K. Kiri i Sharan S. Jhaveri. "Anterior Placement of Cemented Fenestrated Screws in Conjunction with Anterior Reconstruction in Elderly Patients with Severe Vertebral Collapse and Paraparesis". Back Bone Journal 3, nr 1 (2022): 20–23. http://dx.doi.org/10.13107/bbj.2022.v03i01.035.

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Background: Elderly patients with severe osteoporosis are prone to sustain osteoporotic vertebral compression fractures (OVCF’s). Sometimes, they undergo significant vertebral collapse and kyphosis, leading to significant canal compromise and neurological deterioration. Case Description: We present a case series of three patients, of which two had OVCF’s of L1 and L3, respectively, while one patient had Koch’s spine D12 and L1. All three cases had severe vertebral collapse leading to kyphosis, severe pain, and canal compromise, neurological deterioration with paraparesis, and bowel bladder involvement. Surgery warranted total corpectomy of fractured vertebrae (anterior vertebral column resection) and reconstruction of the anterior column. Due to the significant degree of osteoporosis, fenestrated screws with bone cement (poly methyl acrylate) were used anteriorly along with vertebral body reconstruction with cage, through a purely anterior approach. This is the first instance of fenestrated screws being used anteriorly to reduce screw pull-out. In view of the strong anterior construct, a posterior surgery to supplement the fixation could be avoided in these thoracolumbar junctional cases. Results: No patient experienced loosening of implants, nor did any patient experience cement-related complications. Although the present follow-up of these patients is short (12 months), the patients are pain free and independently ambulatory. Conclusion: Using fenestrated screws in an anterior location allow vertebral reconstruction with a single surgery in elderly patients with severe osteoporosis, reducing chances of screw pull-out. Bone plugs at the tip to help prevent cement extravasation from the vertebral body. Keywords: Anterior fenestrated screws, Bone cement, Corpectomy, Osteoporotic vertebral compression fracture, Koch’s spine, Screw pull-out.

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Kokieva, Galia, Martha Ivanova i Varvara Trofimova. "The study of reducing soil mechanical deformation in tilling". E3S Web of Conferences 273 (2021): 05006. http://dx.doi.org/10.1051/e3sconf/202127305006.

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Due to the use of heavy machines, mechanical deformation with the inevitable deterioration in its physico-biological properties is undergoing in agriculture of heavy machines and subfall layers of the soil. The density of the arable and subframe horizons increases, decreases, due to the moisture in the soil. The productivity of cultural plants is influenced by effective fertility not only arable layer, but also subfectant, so it is necessary to take into account the effects on them of agricultural machinery and tractors. At the first stage, the soil particles in close proximity to the paw are shifted forward, forcing the lying layers in front to shrink, when the voltages in the soil reaches the limit values, at some distance from the sock of the paw blades, its shift occurs. At the second stage, the soil begins to intensively shifted forward and move along the surface of the worker. In this regard, the soil resistance to the movement of individual parts of the working body will be different. At the moment when there is an intensive compression of the soil and its shift, the most loaded elements will be the cutting edge and the nose part of the paw, the least - wings of the paws and racks.

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Goeing, Jan, Hendrik Seehausen, Lennart Stania, Nicolas Nuebel, Julian Salomon, Panagiotis Ignatidis, Friedrich Dinkelacker i in. "Virtual process for evaluating the influence of real combined module variations on the overall performance of an aircraft engine". Journal of the Global Power and Propulsion Society 7 (13.03.2023): 95–112. http://dx.doi.org/10.33737/jgpps/160055.

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The effects of real combined variances in components and modules of aero engines, due to production tolerances or deterioration, on the performance of an aircraft engine are analysed in a knowledge-based process. For this purpose, an aero-thermodynamic virtual evaluation process that combines physical and probabilistic models to determine the sensitivities in the local module aerodynamics and the global overall performance is developed. Therefore, an automatic process that digitises, parameterises, reconstructs and analyses the geometry automatically using the example of a real turbofan high-pressure turbine blade is developed. The influence on the local aerodynamics of the reconstructed blade is investigated via a computational fluid dynamics (CFD) simulations. The results of the high-pressure turbine (HPT) CFD as well as of a Gas-Path-Analysis for further modules, such as the compressors and the low-pressure turbine, are transferred into a simulation of the performance of the whole aircraft engine to evaluate the overall performance. All results are used to train, validate and test several deep learning architectures. These metamodels are utilised for a global sensitivity analysis that is able to evaluate the sensitivities and interactions. On the one hand, the results show that the aerodynamics (especially the efficiency <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:msub><mml:mi>η</mml:mi><mml:mrow><mml:mi>H</mml:mi><mml:mi>P</mml:mi><mml:mi>T</mml:mi></mml:mrow></mml:msub></mml:math></inline-formula> and capacity <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:msub><mml:mrow><mml:mover><mml:mi>m</mml:mi><mml:mo>˙</mml:mo></mml:mover></mml:mrow><mml:mrow><mml:mi>H</mml:mi><mml:mi>P</mml:mi><mml:mi>T</mml:mi></mml:mrow></mml:msub></mml:math></inline-formula>) are particularly driven by the variation of the stagger angle. On the other hand, <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:msub><mml:mi>η</mml:mi><mml:mrow><mml:mi>H</mml:mi><mml:mi>P</mml:mi><mml:mi>T</mml:mi></mml:mrow></mml:msub></mml:math></inline-formula> is significantly related to exhaust gas temperature (Tt5), while specific fuel consumption (SFC) and mass flow <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:msub><mml:mrow><mml:mover><mml:mi>m</mml:mi><mml:mo>˙</mml:mo></mml:mover></mml:mrow><mml:mrow><mml:mi>H</mml:mi><mml:mi>P</mml:mi><mml:mi>T</mml:mi></mml:mrow></mml:msub></mml:math></inline-formula> are related to HPC exit temperature (Tt3). However, it can be seen that the high-pressure compressor has the most significant impact on the overall performance. This novel knowledge-based approach can accurately determine the impact of component variances on overall performance and complement experience-based approaches.

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Kim, Beom Su, So Young Lee, Jun Hwan Choi, Mina Seok, Su yeon Ko i Hyun Jung Lee. "Rapidly Progressing Dysphagia After Thoracic Spinal Cord Injury in a Patient With Ankylosing Spondylitis: A Case Report". Geriatric Orthopaedic Surgery & Rehabilitation 14 (2.03.2023): 215145932311593. http://dx.doi.org/10.1177/21514593231159353.

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Introduction Ankylosing spondylitis (AS) is a chronic systemic inflammatory disease affecting the axial skeleton, including the sacroiliac joint, which causes vertebral fusion in the advanced stage. However, reports of anterior cervical osteophytes compressing the esophagus and causing dysphagia in patients with AS are rare. Here, we present the case of a patient with AS and anterior cervical osteophytes who exhibited rapidly progressing dysphagia after thoracic spinal cord injury (SCI). Case Presentation The patient, a 79-year-old man, was previously diagnosed with AS and had syndesmophytes at C2-C7 without dysphagia for several years. In 2020, he began to experience paraplegia, hypesthesia, and bladder and bowel dysfunction after a fall. He also had T9 SCI American Spinal Injury Association Impairment Scale grade A due to a T10 transverse fracture. Four months after SCI, he developed aspiration pneumonia, and a videofluoroscopic swallowing study indicated dysphagia with epiglottic closing problems due to syndesmophytes at the C2-C3 and C3-C4 levels. He received treatment for dysphagia and VitalStim therapy thrice (once daily); however, the recurrent pneumonia and fever continued. He further underwent bedside physical therapy and functional electrical stimulation once daily. However, he died from atelectasis and exacerbation of sepsis. Discussion and Conclusion General deterioration of the patient’s physical condition due to SCI, sarcopenic dysphagia, and compression of cervical osteophytes seemed to be involved in rapid exacerbation following SCI. Early screening for dysphagia is vital in bedridden patients with AS or SCI. Additionally, assessment and follow-up are important if the number of rehabilitation treatments or the out-of-bed movement activity decreases because of pressure ulcers.

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Siegal, Tzony, i Tali Siegal. "Surgical Decompression of Anterior and Posterior Malignant Epidural Tumors Compressing the Spinal Cord: A Prospective Study". Neurosurgery 17, nr 3 (1.09.1985): 424–32. http://dx.doi.org/10.1227/00006123-198509000-00005.

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Abstract Of 167 episodes of spinal epidural neoplastic compression, 86 were treated by operation. The surgical approach was prospectively selected according to the location of the tumor in the spinal canal. Decompression was achieved by 61 vertebral body resections (VBRs) and by 25 laminectomies. The indications for operation were: (a) neurological relapse after previous radiotherapy, (b) the need to make a tissue diagnosis, (c) a radioresistant tumor, and (d) neurological deterioration during radiotherapy. Before VBR, 28% (17 of 61) were still able to walk, 51% (31 of 61) were pareparetic, and 21% (13 of 61) were paraplegic. Bowel and bladder dysfunction was present in 49% (30 of 61). After VBR, the outcome of only 57 procedures was available for evaluation because of the postoperative death of 4 patients. Eighty per cent (46 of 57) were able to walk, 18% (10 of 57) were paraparetic, and 2% (1 of 57) were paraplegic. Ninety-three per cent had normal sphincter control. Before laminectomy, 8% (2 of 25) were ambulatory, 84% (21 of 25) were paraparetic, and 8% (2 of 25) were paraplegic. Bowel and bladder dysfunction was present in 76% (19 of 25). After laminectomy, only 23 procedures were evaluated because of the postoperative death of 2 patients. Thirty-nine per cent (9 of 23) were ambulatory, 35% (8 of 23) were paraparetic, and 26% (6 of 23) were paraplegic. Fifty-seven per cent regained normal sphincter control. The operative mortality was 7% (4 of 61) in VBR and 8% (2 of 25) in laminectomy. The surgical morbidity was 11% (7 of 61) in VBR and 28% (7 of 25) in laminectomy, mainly delayed wound healing. Neurological worsening as a result of laminectomy occurred in 20% (5 of 25) and was transient after 1 VBR (2%). Dislodgement of the vertebral body replacement construct occurred in 3 patients, but has not occurred since the introduction of an improved instrumentation technique. In view of the encouraging results with anterior decompression of the spine, the role of surgical decompression as the primary treatment for ventrally located tumors should be reconsidered. The role of laminectomy in posterior compartment tumors deserves further study.

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Cearns, Michael D., Samantha Hettige, Paolo De Coppi i Dominic N. P. Thompson. "Currarino syndrome: repair of the dysraphic anomalies and resection of the presacral mass in a combined neurosurgical and general surgical approach". Journal of Neurosurgery: Pediatrics 22, nr 5 (listopad 2018): 584–90. http://dx.doi.org/10.3171/2018.5.peds17582.

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OBJECTIVEIt is well established that Currarino syndrome (CS) may be associated with spinal dysraphism. Here, the authors report on 10 CS patients with dysraphic anomalies who had undergone a combined neurosurgical and general surgical approach to repair the dysraphic anomalies and resect the presacral mass in a single operation. They discuss the spectrum of spinal dysraphism that may coexist in CS in the context of its developmental etiology.METHODSChildren with a confirmed CS diagnosis who had undergone the combined operative approach were identified from a departmental database. Presenting features were recorded and preoperative imaging was analyzed to record features of the presacral mass and the dysraphic anomalies. The histopathological nature of the resected presacral mass and the outcomes postoperatively and at the last follow-up were reviewed.RESULTSBetween 2008 and 2015, 10 patients presented with CS, 9 with constipation. Median age at the time of surgery was 1.3 years. Six of the 10 patients had anorectal malformation consisting of anal stenosis, rectal stenosis, or imperforate anus. Spinal anomalies included anterior meningocele (5 cases), low-lying conus (8), terminal syrinx (4), fatty filum (5), caudal lipoma (3), and intraspinal cyst (1). In all cases, the lumbosacral spinal canal was accessed via a midline approach with laminoplasty, allowing spinal cord untethering and repair of the dysraphic anomalies. Following dural closure, the incision was extended inferiorly to incorporate a posterior sagittal approach to resect the presacral mass. The histopathological nature of the mass was mature teratoma (8 cases), complex hamartomatous malformation (1), or neurenteric cyst (1). There were no new instances of neurological deterioration, with most instances of persisting morbidity related to constipation (6 cases) or neurogenic bladder dysfunction (8). There were no infective complications, no instances of cerebrospinal fluid fistula, no recurrences of the presacral mass, and no cases of retethering of the spinal cord.CONCLUSIONSAlthough not part of the original triad, spinal dysraphic anomalies are common in CS and in keeping with a disorder of secondary neurulation. Lumbosacral MRI is an essential investigation when CS is suspected. Children are at risk of sphincter impairment due to the anorectal malformation; however, both spinal cord tethering and compression from the presacral mass may further compromise long-term continence. A combined operative approach to repair the dysraphic anomalies and resect the presacral mass is described with good postoperative and long-term outcomes.

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Morini, Mirko, Michele Pinelli, Pier Ruggero Spina i Mauro Venturini. "Numerical Analysis of the Effects of Nonuniform Surface Roughness on Compressor Stage Performance". Journal of Engineering for Gas Turbines and Power 133, nr 7 (24.03.2011). http://dx.doi.org/10.1115/1.4002350.

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Gas turbine performance degradation over time is mainly due to the deterioration of compressor and turbine blades, which, in turn, causes a modification of the compressor and turbine performance maps. Since the detailed information about the actual modification of the compressor and turbine performance maps is usually unavailable, the component performance can be modeled and investigated by the following: scaling the overall performance map, using stage-by-stage models of the compressor and turbine, and scaling each single stage performance map to account for each stage deterioration, or performing 3D numerical simulations, which allow to both highlight the fluid-dynamic phenomena occurring in the faulty component and grasp the effect on the overall performance of each affected component. In this paper, the authors address the most common and experienced source of loss for a gas turbine, i.e., compressor fouling. With respect to the traditional approach, which mainly aims at the identification of the overall effects of fouling, authors investigate a microscale representation of compressor fouling (i.e., blade surface deterioration and flow deviation). This allows (i) a more detailed investigation of the fouling effects (e.g., mechanism, location along blade height, etc.), (ii) a more extensive analysis of the causes of performance deterioration, and (iii) the assessment of the effect of fouling on stage performance coefficients and on stage performance maps. In this paper, the effect of nonuniform surface roughness on both rotor and stator blades of an axial compressor stage is investigated by using a commercial CFD code. The NASA Stage 37 test case is considered as the baseline geometry and a numerical model already validated against experimental data available in literature is used for the simulations. Different nonuniform combinations of surface roughness levels are imposed on rotor and stator blades. This makes it possible to highlight how the localization of fouling on compressor blades affects compressor performance both at an overall and at a fluid-dynamic level.

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Goodhand, Martin N., Robert J. Miller i Hang W. Lung. "The Impact of Geometric Variation on Compressor Two-Dimensional Incidence Range". Journal of Turbomachinery 137, nr 2 (24.09.2014). http://dx.doi.org/10.1115/1.4028355.

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An important question for a designer is how, in the design process, to deal with the small geometric variations which result from either the manufacture process or in-service deterioration. For some blade designs geometric variations will have little or no effect on the performance of a row of blades, while in others their effects can be significant. This paper shows that blade designs which are most sensitive are those which are susceptible to a distinct switch in the fluid mechanisms responsible for limiting blade performance. To demonstrate this principle, the sensitivity of compressor 2D incidence range to manufacture variations is considered. Only one switch in mechanisms was observed, the onset of flow separation at the leading edge. This switch is only sensitive to geometric variations around the leading edge, 0–3% of the suction surface. The consequence for these manufacture variations was a 10% reduction in the blade's positive incidence range. For this switch, the boundary in the design space is best defined in terms of the blade pressure distribution. Blade designs where the acceleration exceeds a critical value just downstream of the leading edge are shown to be robust to geometric variation. Two historic designs, supercritical blades and blades with sharp leading edges, though superior in design intent, are shown to sit outside this robust region and thus, in practice, perform worse. The improved understanding of the robust, region of the design space is then used to design a blade capable of a robust, 5% increase in operating incidence range.

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Abdelwahid, Mohammed Balla, Eimad Eldin Elhadi Musa, Hazim Mohammed Taha, Sohaib Osman Hamed i Esra Abdulrahman Mohamed Alhassan. "Performance Analysis of Eroded Compressor Stage". Journal of Karary University for Engineering and Science, 21.12.2021. http://dx.doi.org/10.54388/jkues.v1i2.94.

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Erosion of compressor blades due to operation in dusty environments is a serious problem for the manufacturers and users of gas turbine engines, because of significant degradations in performance. This study has been devoted to estimating the change of performance parameters of an axial compressor stage due to erosive deterioration. The influence of erosion considered as consequences of a reduction of rotor blade airfoils, and an increase of tip clearance. The results of this study obtained using the CFD code “NUMECA Fine/Turbo”. This CFD code is a steady, quasi-three-dimensional Reynolds Averaged Navier-Stokes (RANS) solver. A Spalart-Allmaras turbulence model is used. The compressor stage parameters presented for three rotational speeds. Proposed a new approach to consider the changes of geometric parameters of blades due to erosion. Presented an analysis of the effect of erosion and its individual consequences on the pressure ratio, isentropic efficiency and stability margin of the stage. The obtained results verified using an existing experimental data.

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Lorenz, Max, Markus Klein, Jan Hartmann, Christian Koch i Stephan Staudacher. "Prediction of Compressor Blade Erosion Experiments in a Cascade Based on Flat Plate Specimen". Frontiers in Mechanical Engineering 8 (25.07.2022). http://dx.doi.org/10.3389/fmech.2022.925395.

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Erosion is an essential deterioration mechanism in compressors of jet engines. Erosion damage predictions require the determination of erosion rates through flat plate experiments. The applicability of the erosion rates is limited to conditions that are comparable to the prevailing boundary conditions of the flat plate experiment. A performed dimensional analysis enables the correct transfer of the flat plate erosion rates to the presented physical calculation model through limits in spatial and time resolution. This efficient approach avoids computationally intensive single-impact computations. The approach features a re-meshing procedure that adheres to the limits derived by the dimensional analysis. The computation approach is capable of describing local geometry changes on cascade compressor blades which are exposed to erosive particles. A linear erosion cascade experiment performed on NASA Rotor 37 provides validation data for the calculated erosion-induced shape change. Arizona Road Dust particles are used to deteriorate Ti-Al6-4V compressor blades. The experiment is performed at an incidence of i = 7°and Ma = 0.76 representing ground idle conditions. The presented parametric study for element size and time step revealed preferable values for the presented computation. Calculations performed with the determined values showed that the erosion prediction is within the measurement tolerance of the experiment and, therefore, high accordance between the computation and the experiment is achieved. To extend the current state of the art, it is demonstrated that the derived discretization is decisive for the correct reproduction of the eroded geometries and fitting parameters are no longer needed. The good agreement between the experimental measurements and the calculated results confirms the correct application of the physical model to the phenomenology of erosion. Thus, the presented physical model offers a novel approach to adapting deterioration mechanisms caused by erosion to any compressor blade geometry.

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40

Ishaque, Ghulam, Qun Zheng, Naseem Ahmad, Mingcong Luo i Sanaullah Khushak. "Evaluation of non-uniform water film behavior on the performance of an axial aeroengine compressor". International Journal of Turbo & Jet-Engines, 10.03.2022. http://dx.doi.org/10.1515/tjj-2021-0080.

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Abstract Two-phase flow CFD simulations are conducted to investigate the performance characteristics of an axial flow compressor operating under an excessive amount of water intrusion exposed to a rainy atmosphere. In order to obtain a certain compressor behavior under the water film irregularities, the blade surfaces are divided into a small number of regions depending on the film thickness. In addition, to examine the droplets interaction with rotating blades and splashing process, a self-compiled FORTRAN code has been used. The results showed that uneven roughening of blade surfaces is the effective technique to identify the deterioration in performance with irregular wall film thickness. The overall adiabatic efficiency and pressure ratio are decreased by 6% and 0.88 at a 5% water injection rate using an irregular rough wall model. Moreover, the increased wall film has adversely influenced the internal flow mechanism, which resulted the increase of passage shock intensity, entropy level within the main flow zone as well as the blade surface temperature.

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41

Kurz, Rainer, Grant Musgrove i Klaus Brun. "Experimental Evaluation of Compressor Blade Fouling". Journal of Engineering for Gas Turbines and Power 139, nr 3 (4.10.2016). http://dx.doi.org/10.1115/1.4034501.

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Fouling of compressor blades is an important mechanism leading to performance deterioration in gas turbines over time. Experimental and simulation data are available for the impact of specified amounts of fouling on the performance as well as the amount of foulants entering the engine for defined air filtration systems and ambient conditions. This study provides experimental data on the amount of foulants in the air that actually stick to a blade surface for different conditions. Quantitative results both indicate the amount of dust as well as the distribution of dust on the airfoil, for a dry airfoil, and also the airfoils that were wet from ingested water, in addition to, different types of oil. The retention patterns are correlated with the boundary layer shear stress. The tests show the higher dust retention from wet surfaces compared to dry surfaces. They also provide information about the behavior of the particles after they impact on the blade surface, showing for a certain amount of wet film thickness, the shear forces actually wash the dust downstream and off the airfoil. Further, the effect of particle agglomeration of particles to form larger clusters was observed, which would explain the disproportional impact of very small particles on boundary layer losses.

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42

Tabakoff, Widen, i Robert Mason. "Dust-Induced Deterioration of Compressor First Stage Blades in Supersonic Cascade Erosion Wind Tunnel". International Journal of Turbo and Jet Engines 24, nr 2 (styczeń 2007). http://dx.doi.org/10.1515/tjj.2007.24.2.85.

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Kurz, Rainer, i Klaus Brun. "Fouling Mechanisms in Axial Compressors". Journal of Engineering for Gas Turbines and Power 134, nr 3 (3.01.2012). http://dx.doi.org/10.1115/1.4004403.

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Fouling of compressor blades is an important mechanism leading to performance deterioration in gas turbines over time. Fouling is caused by the adherence of particles to airfoils and annulus surfaces. Particles that cause fouling are typically smaller than 2 to 10 microns. Smoke, oil mists, carbon, and sea salts are common examples. Fouling can be controlled by appropriate air filtration systems, and can often be reversed to some degree by detergent washing of components. The adherence of particles is impacted by oil or water mists. The result is a build up of material that causes increased surface roughness and to some degree changes the shape of the airfoil (if the material build up forms thicker layers of deposits), with subsequent deterioration in performance. Fouling mechanisms are evaluated based on observed data, and a discussion on fouling susceptibility is provided. A particular emphasis will be on the capabilities of modern air filtration systems.

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44

Богоявленский, А., i A. Bogoyavlenskiy. "Metrological aspects of pre-flight anti-icing procedures for civil aircraft". World of measurement, 25.09.2019, 22–26. http://dx.doi.org/10.35400/1813-8667-2019-3-22-26.

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Snow-ice deposits formed on the outer surfaces of aircrafts on the ground during parking can have a negative impact during take-off due to the deterioration of aerodynamic and flight performance, a significant and even critical decrease in lift, increased drag, blocking controls, difficulty or blocking of landing gear retraction, damage to the blades of inlet guide vanes and/or the blades of an engine compressor. To exclude the influence of snow and ice deposits, anti-icing treatment is performed, including their removal and/or protection from subsequent formation. For this purpose, special anti-icing machines (deicers), equipped with such means of instrumental control as counters of anti-icing fluid pumps, measuring scales of anti-icing fluid tanks, thermometers and pressure gauges for temperature and pressure measuring at the outlet of a spray nozzle, are used. The article deals with the metrological aspects of civil aircrafts anti-icing prior to flight.

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45

Богоявленский, А., i A. Bogoyavlenskiy. "Metrological aspects of pre-flight anti-icing procedures for civil aircraft". World of measurement, 21.11.2019, 26–31. http://dx.doi.org/10.35400/1813-8667-2019-4-26-31.

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Snow-ice deposits formed on the outer surfaces of aircrafts on the ground during parking can have a negative impact during take-off due to the deterioration of aerodynamic and flight performance, a significant and even critical decrease in lift, increased drag, blocking controls, difficulty or blocking of landing gear retraction, damage to the blades of inlet guide vanes and/or the blades of an engine compressor. To exclude the influence of snow and ice deposits, anti-icing treatment is performed, including their removal and/or protection from subsequent formation. For this purpose, special anti-icing machines (deicers), equipped with such means of instrumental control as counters of anti-icing fluid pumps, measuring scales of anti-icing fluid tanks, thermometers and pressure gauges for temperature and pressure measuring at the outlet of a spray nozzle, are used. The article deals with the metrological aspects of civil aircrafts anti-icing prior to flight.

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46

Morini, M., M. Pinelli, P. R. Spina i M. Venturini. "Influence of Blade Deterioration on Compressor and Turbine Performance". Journal of Engineering for Gas Turbines and Power 132, nr 3 (24.11.2009). http://dx.doi.org/10.1115/1.4000248.

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Gas turbine operating state determination consists of the assessment of the modification due to deterioration and fault of performance and geometric data characterizing machine components. One of the main effects of deterioration and fault is the modification of compressor and turbine performance maps. Since detailed information about actual modification of component maps is usually unavailable, many authors simulate the effects of deterioration and fault by a simple scaling of the map itself. In this paper, stage-by-stage models of the compressor and the turbine are used in order to assess the actual modification of compressor and turbine performance maps due to blade deterioration. The compressor is modeled by using generalized performance curves of each stage matched by means of a stage-stacking procedure. Each turbine stage is instead modeled as two nozzles, a fixed one (stator) and a moving one (rotor). The results obtained by simulating some of the most common causes of blade deterioration (i.e., compressor fouling, compressor mechanical damage, turbine fouling, and turbine erosion), occurring in one or more stages simultaneously, are reported in this paper. Moreover, compressor and turbine maps obtained through the stage-by-stage procedure are compared with the ones obtained by means of map scaling. The results show that the values of the scaling factors depend on the corrected rotational speed and on the load. However, since the variation in the scaling factors in the operating region close to the design corrected rotational speed is small, the use of the scaling factor as health indices can be considered acceptable for gas turbine health state determination at full load. Moreover, also the use of scaled maps in order to represent compressor and turbine behavior in deteriorated conditions close to the design corrected rotational speed can be considered acceptable.

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Rao, P. Naga Srinivasa, i V. N. Achutha Naikan. "An Optimal Maintenance Policy for Compressor of a Gas Turbine Power Plant". Journal of Engineering for Gas Turbines and Power 130, nr 2 (22.01.2008). http://dx.doi.org/10.1115/1.2795762.

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This paper proposes a condition based maintenance policy for compressors of industrial gas turbine. Compressor blade fouling contributes a major performance loss in the operation of gas turbine. Water washing is usually done for recovery of the blade fouling problem. There exist two different washing methods, namely, online and offline washings. Many researchers suggested that performing a combined program of regular online washing plus periodic offline washing would give fruitful results with respect to economy. However, such studies are of empirical nature or have considered only deterministic treatment. Considering the rate of fouling as discrete state random process, we propose a condition based maintenance policy with periodic online washing and inspection directed offline washing. According to this policy, the compressor undergoes regular online washes for every 1∕λm operating hours, and also undergoes inspections at constant rate λI. If the observed condition at an inspection is worse than threshold deterioration state, then perform offline washing. Otherwise, continue with online washing. The proposed algorithm gives optimum schedules for both online washing and inspections considering minimization of total cost per operating hour as objective. It also gives optimum threshold deterioration level for performing offline washing. A comparison of the results for a hypothetical gas turbine compressor is presented as illustration.

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Döring, Felix, Stephan Staudacher, Christian Koch i Matthias Weißschuh. "Modeling Particle Deposition Effects in Aircraft Engine Compressors". Journal of Turbomachinery 139, nr 5 (24.01.2017). http://dx.doi.org/10.1115/1.4035072.

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Airborne particles ingested in aircraft engines deposit on compressor blading and end walls. Aerodynamic surfaces degrade on a microscopic and macroscopic scale. Blade row, compressor, and engine performance deteriorate. Optimization of maintenance scheduling to mitigate these effects requires modeling of the deterioration process. This work provides a deterioration model on blade row level and the experimental validation of this model in a newly designed deposition test rig. When reviewing previously published work, a clear focus on deposition effects in industrial gas turbines becomes evident. The present work focuses on quantifying magnitudes and timescales of deposition effects in aircraft engines and the adaptation of the generalized Kern and Seaton deposition model for application in axial compressor blade rows. The test rig's cascade was designed to be representative of aircraft engine compressor blading. The cascade was exposed to an accelerated deposition process. Reproducible deposition patterns were identified. Results showed an asymptotic progression of blade row performance deterioration. A significant increase in total pressure loss and decrease in static pressure rise were measured. Application of the validated model using existing particle concentration and flight cycle data showed that more than 95% of the performance deterioration due to deposition occurs within the first 1000 flight cycles.

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Ghenaiet, Adel. "Study of Sand Particle Trajectories and Erosion Into the First Compression Stage of a Turbofan". Journal of Turbomachinery 134, nr 5 (24.05.2012). http://dx.doi.org/10.1115/1.4004750.

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Aero-engines operating in dusty environments are subject to ingestion of erodent particles leading to erosion damage of blades and a permanent drop in performance. This work concerns the study of particle dynamics and erosion of the front compression stage of a commercial turbofan. Particle trajectories simulations used a stochastic Lagrangian tracking code that solves the equations of motion separately from the airflow in a stepwise manner, while the tracking of particles in different cells is based on the finite element method. As the locations of impacts and rates of erosion were predicted, the subsequent geometry deteriorations were assessed. The number of particles, sizes, and initial positions were specified conformed to sand particle distribution (MIL-E5007E, 0-1000 micrometers) and concentrations 50–700 mg/m3. The results show that the IGV blade is mainly eroded over the leading edge and near hub and shroud; also the rotor blade has a noticeable erosion of the leading and trailing edges and a rounding of the blade tip corners, whereas in the diffuser, erosion is shown to spread over the blade surfaces in addition to the leading edge and trailing edge.

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Malhotra, Ashima, Shraman Goswami i Pradeep Amboor Madathil. "Performance deterioration of axial compressor rotor due to uniform and non-uniform surface roughness". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, 14.03.2022, 095441002110689. http://dx.doi.org/10.1177/09544100211068912.

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Surface roughness is a significant source of performance loss in gas turbine engines. The fan and compressor, being the initial components of the gas turbine engine, are more prone to surface roughness effects due to the ingestion of debris at low atmospheric conditions. This paper attempts to numerically study the impact of uniform and non-uniform surface roughness on axial compressor rotor performance. NASA rotor 37 is used as the validation test case for the numerical methodology, and the results show a good match between the experimental and computational fluid dynamics data. Detailed flow field analysis indicates that there is a reduction in rough blade performance and the overall flow turning that reduces the work done by the rotor. The location sensitivity studies shock location is the major contributor to the overall loss in the performance. Also, the study of non-uniform roughness on blade performance shows that roughness on the leading edge is the major contributor to the loss as compared to the trailing edge and so does roughness on the shroud as compared to the roughness on the hub. An interesting observation is that for the given configuration and roughness height, near the shroud, the role of the tip vortex is more pronounced than the role of surface roughness on the performance.

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