Journal articles: 'Aero engine casings'

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Zhou, Nan, and Xu Liu. "Feature-based automatic NC programming for aero-engine casings." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 233, no. 4 (April 28, 2018): 1289–301. http://dx.doi.org/10.1177/0954405418769949.

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Traditional numerical control (NC) programming methods based on commercial computer-aided manufacturing systems usually require a large number of manual interactions with high-skilled experience, which not only results in low efficiency but also unstable machining quality. Especially since the structural complexity and machining requirements keep increasing, the NC programming is becoming a bottleneck problem in machining complex parts like aero-engine casings. This article proposes a feature-based automatic NC programming approach for aero-engine casings. A machining feature classification towards the geometric and machining characteristics of aero-engine casings is given. Then, a feature-based method to extract machining regions by considering the alternatives in selecting turning or milling operations is discussed. After the construction of machining operations, an undercut region detection method is also presented to evaluate the interim machining effects reasoned by each individual machining operation for excessive cutting avoidance. By implementing the proposed approach, a feature-based NC programming system is developed on a commercial computer-aided manufacturing platform and a real aero-engine casing is chosen to demonstrate the feasibility of the proposed approach.

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Beaudoin, Marc-Antoine, and Kamran Behdinan. "Analytical lump model for the nonlinear dynamic response of bolted flanges in aero-engine casings." Mechanical Systems and Signal Processing 115 (January 2019): 14–28. http://dx.doi.org/10.1016/j.ymssp.2018.05.056.

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Zhou, Xu, Dinghua Zhang, Ming Luo, and Baohai Wu. "Chatter stability prediction in four-axis milling of aero-engine casings with bull-nose end mill." Chinese Journal of Aeronautics 28, no. 6 (December 2015): 1766–73. http://dx.doi.org/10.1016/j.cja.2015.06.001.

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Djilali, Kaid-Ameur, and Mohamed Serrier. "Experimental Method of Tribological Modelling of Different Coatings of Stainless Steel." Mechanics and Mechanical Engineering 22, no. 4 (September 2, 2020): 1273–86. http://dx.doi.org/10.2478/mme-2018-0098.

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AbstractFretting wear is a unique form of material degradation caused by small amplitude oscillatory relative motion of two surfaces in contact. Fretting wear is typically encountered at relative displacements of less than 300 μm and occurs in either a gross slip regime [1] (where there is slip displacement across the whole contact), or a partial slip regime (where there are parts of the contact where no slip displacement occurs). Fretting wear is experienced within a wide range of industrial sectors, [2] including aero engine couplings, locomotive axles and nuclear fuel casings [3]. Under higher loads and smaller displacement amplitudes, the contact will be within the partial slip regime, often resulting in fretting fatigue where the dominant damage mode is a reduction in fatigue life [4]. Friction is a very common phenomenon in daily life and industry, which is governed by the processes occurring in the thin surfaces layers of bodies in moving contact. The simple and fruitful idea used in studies of friction is that there are two main non-interacting components of friction, namely, adhesion and deformation [5, 6].

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Fois, N., M. Watson, and MB Marshall. "The influence of material properties on the wear of abradable materials." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 231, no. 2 (August 5, 2016): 240–53. http://dx.doi.org/10.1177/1350650116649528.

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In aero-engines it is possible for the blades of the compressor, turbine or fan to incur into their casings. At these interfaces a lining of composite abradable material is used to limit damage to components and thereby sustain the efficiency and longevity of the engine as a whole. These composite materials must have good abradability and erosion resistance. Previously, the wear mechanisms at the contact between the blade and the coating have been characterised using stroboscopic imaging and force measurement on a scaled test-rig platform. This work is focused on the characterisation of the wear mechanism for two different hardnesses of abradable lining. The established stroboscopic imaging technique and contact force measurements are combined with sectioning of the abradable material in order to analyse the material’s response during the tests. A measure of the thermal properties and the resulting temperature of the linings during the test have also been made to further understand the effect of coating hardness. The wear mechanism, material response, contact force and thermal properties of the coating have been used to characterise the different material behaviour with different hardness. At low incursion rates, with a soft coating, the blade tip becomes worn after an initial adhesive transfer from the coating. Post-test sectioning showed blade material and significant compaction present in the coating. The harder coating produced adhesion on the blade tip with solidification observed in the coating. Thermal diffusivity measurements and modelling indicated that thermally driven wear observed was as a consequence of the increased number of boundaries between the metal and hBN phases present interrupting heat flow, leading to a concentration of surface heat. At higher incursion rates, the wear mechanism is more similar between the coatings and a cutting mechanism dominates producing negligible adhesion and blade wear.

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Dong, Ting Jian, Jin Chen, and Hua Peng Ding. "High-Speed Cutting Machining Simulation of Aero Engine Casing Hole." Advanced Materials Research 915-916 (April 2014): 1014–17. http://dx.doi.org/10.4028/www.scientific.net/amr.915-916.1014.

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For the high-speed machining aero engine casing hole, according to the principle of metal forming and the characteristic of metal cutting plane strain, with selecting some key physical factors of the cutter - chip contact friction and abrasion model, the Cartesian orthogonal cutting model of aero engine casing hole was established by using the Deform, a sort of finite element analysis software. With taking cutting temperature for preferred aim of the cutting parameters, select the appropriate cutting parameters, the aim of aero-engine casing high-speed (cutting speed up to 700m/min) cutting has been achieved by simulation, and the feasibility of the cutting process was researched and confirmed in theoretically by analyzing the cutting force, cutting temperature and tool wear condition.

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Dhopade, Priyanka, Benjamin Kirollos, Peter Ireland, and Leo Lewis. "A Comparison of Single-Entry and Multiple-Entry Casing Impingement Manifolds for Active Thermal Tip Clearance Control." International Journal of Turbomachinery, Propulsion and Power 6, no. 2 (May 14, 2021): 10. http://dx.doi.org/10.3390/ijtpp6020010.

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In this paper, we compare using computational fluid dynamics the aero-thermal performance of two candidate casing manifolds for supplying an impingement-actuated active tip clearance control system for an aero-engine high-pressure turbine. The two geometries are (a) single-entry: an annular manifold fed at one circumferential location; (b) multiple-entry: a casing manifold split into four annular sectors, with each sector supplied separately from an annular ring main. Both the single-entry and multiple-entry systems analysed in this paper are idealised versions of active clearance control systems in current production engines. Aero-thermal performance is quantitatively assessed on the basis of the heat transfer coefficient distribution, driving temperature difference for heat transfer between the jet and casing wall and total pressure loss within the high-pressure turbine active clearance control system. We predict that the mean heat transfer coefficient (defined with respect to the inlet temperature and local wall temperature) of the single-entry active clearance control system is 77% greater than the multiple-entry system, primarily because the coolant in the multiple-entry case picks up approximately 40 K of temperature from the ring main walls, and secondarily because the average jet Reynolds number of impingement holes in the single-entry system is 1.2 times greater than in the multiple-entry system. The multiple-entry system exhibits many local hot and cold spots, depending on the position of the transfer boxes, while the single-entry case has a more predictable aero-thermal field across the system. The multiple-entry feed system uses an average of 20% of the total available pressure drop, while the feed system for the single-entry geometry uses only 2% of the total available pressure drop. From the aero-thermal results of this computational study, and in consideration of holistic aero-engine design factors, we conclude that a single-entry system is closer to an optimal solution than a multiple-entry system.

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Ma, Yingqun, Qingjun Zhao, Kai Zhang, Meng Xu, and Wei Zhao. "Effects of mount positions on vibrational energy flow transmission characteristics in aero-engine casing structures." Journal of Low Frequency Noise, Vibration and Active Control 39, no. 2 (May 17, 2019): 313–26. http://dx.doi.org/10.1177/1461348419845506.

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The main goal of the study is to apply the structural intensity method to analyze the effects of positions of the main-mount and the sub-mount on the vibrational energy flow transmission characteristics in aero-engine casing structures, so as to attenuate the vibration of the casing and the whole aero-engine. Structural intensity method, indicating magnitude and direction of the vibrational energy flow, is a powerful tool to study vibration problems from the perspective of energy. In this paper, a casing-support-rotor coupling model subjected to the rotor unbalanced forces is established by the finite element method. Formulations of the structural intensity of a shell element and the structural intensity streamline are given. A simulation system consisting of the finite element tool and the in-house program is developed to carry out forced vibration analysis and structural intensity calculation. The structural intensity field of the casing is visualized in the forms of vector diagram and streamline representation. The vibrational energy flow behaviors of the casing at the rotor design rotating speed are analyzed, and the vibrational energy flow transmission characteristics of the casing with different axial positions of the main-mount and the sub-mount are investigated. Moreover, some measures to attenuate the vibration of the casing are obtained from the numerical results, and their effectiveness is verified in the frequency domain and the time domain. The results shed new light on the effects of the mount positions on the vibration energy transmission behaviors of the casing structure. The structural intensity method is a more advanced tool for solving vibration problems in engineering. Furthermore, it may provide some guidance for the vibration attenuation of the casing and the whole aero-engine.

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SUN, Xiaofeng, Xu DONG, and Dakun SUN. "Recent development of casing treatments for aero-engine compressors." Chinese Journal of Aeronautics 32, no. 1 (January 2019): 1–36. http://dx.doi.org/10.1016/j.cja.2018.11.005.

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Wang, Nanfei, Chao Liu, and Dongxiang Jiang. "Prediction of transient vibration response of dual-rotor-blade-casing system with blade off." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 14 (April 4, 2019): 5164–76. http://dx.doi.org/10.1177/0954410019839884.

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Fan blade off occurring in a running rotor of the turbofan engine dual-rotor system will cause a sudden unbalance and inertia asymmetry, which results in large impact load and consequently induces the rubbing between blade and casing. In order to reveal the transient dynamic response characteristics of actual aero-engine when fan blade off event occurs, the dynamic model of dual-rotor-blade-casing system is developed, in which the distribution characteristics of the stiffness and mass, the load transfer, and the coupling effects of dual-rotor and casing are included. Considering several excitations caused by blade off, the physical process and mechanical characteristics of the fan blade off event are described qualitatively. Considering that only the casing acceleration signal can be used for condition monitoring in actual aero-engine, the transient response including rotor vibration displacement and casing vibration acceleration during the instantaneous status are obtained. Due to the time-varying and highly nonlinear characteristics of vibration responses, frequency slice wavelet transform is employed to isolate the vibration signal features. The results show that the impact load induced by the sudden imbalance causes significant increase of vibration amplitude. The rubbing action between blade and rotor will impose constraint effects on the rotor, which decreases the transient vibration amplitude. The inertia asymmetry has a big impact on the transient response. The vibration characteristics of casing acceleration under blade off are similar to those of rotor displacement, while casing acceleration response attenuates to stable value faster and is more sensitive to high-frequency components of vibration.

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Kang, Hehe, and Zhi-Min Li. "Assembly research of aero-engine casing involving bolted connection based on rigid-compliant coupling assembly deviation modeling." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 234, no. 14 (March 4, 2020): 2803–20. http://dx.doi.org/10.1177/0954406220910455.

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Assembly analysis is necessary for mechanical product to optimize design and improve the product quality since assembly deviation is the key factor affecting the assembly quality. In this paper, the rigid-compliant assembly of thin-walled aero-engine casing is studied to evaluate the assembly quality at the design stage. First, the Jacobian–Torsor model is proposed to construct multistage casing assembly owing to its effectiveness to express assembly deviation. The torsor expression is modified and expanded to present the rigid-compliant coupling tolerance. Then, the partial parallel chain is addressed via combination operation. By using extremum and statistical method, the tolerance zone and the distribution of the objective deviation are obtained. Furthermore, to study the effect of specified compliant deviation on statistical distribution, the bolt looseness and positional deformation are investigated to provide an effective means for geometric deviation and connecting joints of aero-engine casing components of precision assembly. The presented method can address compliant deformation tolerance and geometrical manufacturing tolerance together, and is reliable for casing assembly to predict assembly quality at the design stage. In addition, it also has a great significance to guide tolerance design and product optimization.

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Huang, Zi, Chaoping Zang, Yuying Jiang, and Xiaowei Wang. "Dynamic finite element model validation of an assembled aero-engine casing." Journal of Physics: Conference Series 744 (September 2016): 012139. http://dx.doi.org/10.1088/1742-6596/744/1/012139.

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He, Qing, Haijun Xuan, Lulu Liu, Weirong Hong, and Rongren Wu. "Perforation of aero-engine fan casing by a single rotating blade." Aerospace Science and Technology 25, no. 1 (March 2013): 234–41. http://dx.doi.org/10.1016/j.ast.2012.01.010.

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14

Xiao, Guijian, Youdong Zhang, Yi He, Yun Huang, Shui He, and Kangkang Song. "Bionic Structure on Complex Surface with Belt Grinding for Electron Beam Welding Seam of Titanium Alloy." Applied Sciences 10, no. 7 (March 30, 2020): 2370. http://dx.doi.org/10.3390/app10072370.

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Electron beam welding (EBW) is widely used to weld titanium alloy parts such as aero-engine casing and blades. The surface quality after EBW has a significant influence on the aero-engine performance of those parts. We propose a surface treatment method with grinding on a titanium alloy electron beam weld. We analyze the influence of grinding parameters on the characteristics of the grinding surface. The experiment shows the applicability of ground surface by belt grinding on EBW and its impact on aero-engine performance. After belt grinding, both the welded surface and the surface connected with the substrate are smooth. The extra height of the seam was less than 0.2 mm, and the surface roughness (Ra) of the weld after grinding can be less than 0.98 μm. The microstructure of the weld after grinding was analyzed. Two types of bionic shapes were obtained, a sawtooth shape with a width of 40 μm and a height of 10 μm and a wavy shape with a width of 20 μm and a height of 3 μm. From the analysis above, the bionic surface can be obtained by grinding on the weld with an abrasive belt.

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Yu, Mingyue, Zhigang Feng, Jiajing Huang, and Linlin Zhu. "Aero-engine rotor-stator rubbing position identification based on casing velocity signal." Journal of Vibroengineering 18, no. 4 (June 30, 2016): 2123–34. http://dx.doi.org/10.21595/jve.2016.16644.

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Kang, Hehe, Zhi-Min Li, Tao Liu, and Pizhong Qiao. "Tolerance Design of Multistage Aero-Engine Casing Assembly by Vibration Characteristic Evaluation." Journal of Aerospace Engineering 34, no. 5 (September 2021): 04021064. http://dx.doi.org/10.1061/(asce)as.1943-5525.0001323.

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Song, Huiying, Shaohui Wang, and Kai Sun. "Rotordynamic Characteristics Analysis for an aero-engine Low Pressure Rotor Rig Test Model." MATEC Web of Conferences 179 (2018): 03012. http://dx.doi.org/10.1051/matecconf/201817903012.

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3D whole engine finite element model of a low pressure rotor rig test model is established in this paper. Rotorynamic characteristics are mainly analysed with three models, which include rotor model with static stiffness, rotor model with dynamic stiffness, and whole engine model. The calculation results were compared and discussed deeply. Rotordynamic characteristics of rotor model with static stiffness are similar with the rotor model with dynamic stiffness, but the latter may have additional resonance peaks caused by dynamic stiffness. Whole engine model, which can capture the modes of casing and coupling vibration between stator and rotor, may have more critical speeds than rotor model only. The unbalance response amplitude and phase angle of the whole engine model are different with the only rotor model, in the values and distributions of the peaks. The result of rotor model with dynamic stiffness is closed to the whole engine model than the rotor model with static stiffness. The peak values of the whole engine model are smaller than the only rotor model. Rotordynamic characteristics with whole engine model are more accurate than rotor model only, so it necessary to analyse rotordynamic characteristics with whole engine model in detail design stage.

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Guo, Chen. "Study on the recognition of aero-engine blade-casing rubbing fault based on the casing vibration acceleration." Measurement 65 (April 2015): 71–80. http://dx.doi.org/10.1016/j.measurement.2014.12.038.

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Schmidt, T., V. Gümmer, and M. Konle. "Potential of surrogate modelling in compressor casing design focussing on rapid tip clearance assessments." Aeronautical Journal 125, no. 1291 (September 2021): 1587–610. http://dx.doi.org/10.1017/aer.2021.39.

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ABSTRACTLosses induced by tip clearance limit decisive improvements in the system efficiency and aerodynamic operational stability of aero-engine axial compressors. The tendency towards even lower blade heights to compensate for higher fluid densities aggravates their influence. Generally, it is emphasised that the tip clearance should be minimised but remain large enough to prevent collisions between the blade tip and the casing throughout the entire mission. The present work concentrates on the development of a preliminary aero-engine axial compressor casing design methodology involving meta-modelling techniques. Previous research work at the Institute for Turbomachinery and Flight Propulsion resulted in a Two-Dimensional (2D) axisymmetric finite element model for a generic multi-stage high-pressure axial compressor casing. Subsequent sensitivity studies led to the identification of significant parameters that are important for fine-tuning the tip clearance via specific flange design. This work is devoted to an exploration of the potential of surrogate modelling in preliminary compressor casing design with respect to rapid tip clearance assessments and its corresponding precision in comparison with finite element results. Reputed as data-driven mathematical approximation models and conceived for inexpensive numerical simulation result reproduction, surrogate models show even greater capacity when linked with extensive design space exploration and optimisation algorithms.Compared with high-fidelity finite element simulations, the reductions obtained in computational time when using surrogate models amount to 99.9%. Validated via statistical methods and dependent on the size of the training database, the precision of surrogate models can reach down to the range of manufacturing tolerances. Subsequent inclusion of such surrogate models in a parametric optimisation process for tip clearance minimisation rapidly returned adaptions of the geometric design variables.

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Liu, Lulu, Haijun Xuan, Zekan He, Dandan Niu, Jun Xing, and Weirong Hong. "Containment capability of 2D triaxial braided tape wound composite casing for aero-engine." Polymer Composites 37, no. 7 (April 23, 2015): 2227–42. http://dx.doi.org/10.1002/pc.23401.

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Chana, Kam S., and Terry V. Jones. "An Investigation on Turbine Tip and Shroud Heat Transfer." Journal of Turbomachinery 125, no. 3 (July 1, 2003): 513–20. http://dx.doi.org/10.1115/1.1575253.

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Detailed experimental investigations have been performed to measure the heat transfer and static pressure distributions on the rotor tip and rotor casing of a gas turbine stage with a shroudless rotor blade. The turbine stage was a modern high pressure Rolls-Royce aero-engine design with stage pressure ratio of 3.2 and nozzle guide vane (ngv) Reynolds number of 2.54E6. Measurements have been taken with and without inlet temperature distortion to the stage. The measurements were taken in the QinetiQ Isentropic Light Piston Facility and aerodynamic and heat transfer measurements are presented from the rotor tip and casing region. A simple two-dimensional model is presented to estimate the heat transfer rate to the rotor tip and casing region as a function of Reynolds number along the gap.

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Chen, Bing, Ting Yang, and Jun De Qi. "Fault Forecast Technology of Machine Based on Grey Theory for Aero-Engine Product Line." Advanced Materials Research 338 (September 2011): 718–22. http://dx.doi.org/10.4028/www.scientific.net/amr.338.718.

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Facing to the dynamic process of machine running, grey theory is introduced to increase the accuracy of forecast on machine fault. Firstly the mathematical model of the machine fault is constructed according to the life cycle of machine. Mean time between failures is defined as a tool to describe the fault on the machine. Moreover the fault is predicted respectively according to amount of data sample. And the produce to build the grey information model is given in this paper in detail. Finally an actual aero-engine casing production line is presented as an example to validate the algorithms in this paper. The results show that the fault forecast based on grey theory has high accuracy.

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Yao, Xingyu, Jianjun Wang, and Xue Zhai. "Research and application of improved thin-layer element method of aero-engine bolted joints." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 231, no. 5 (May 9, 2016): 823–39. http://dx.doi.org/10.1177/0954410016643978.

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A new dynamic modeling method called the improved thin-layer element method is proposed to apply to the aero-engine bolted joints. The thin-layer elements are partitioned based on the interface contact stress distribution. In addition, the material parameters of the partitioned thin-layer elements are determined by the bolted joints stiffness technique and the fractal contact theory without the experimental results, which allows the engineer to estimate the dynamic characteristics of whole structure before the physical prototype is available. First, the modeling principles of the improved thin-layer element method are studied and the bolted joints stiffness is analyzed. Next, the material parameters of the partitioned thin-layer elements are determined on the basis of the interface contact stress distribution characteristics of the bolted joints. Finally, this method is applied to the simulative casing bolted joints structure and the results are compared with the experimental results in order to verify the proposed method. The results indicate that the improved thin-layer element method is more accurate than the thin-layer elements method, and the material parameters of the partitioned thin-layer elements can be expressed by the structural parameters of the aero-engine bolted joints without updating based on the experiment.

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Raisson, Gérard, Jean Yves Guédou, Didier Guichard, and Jean Marc Rongvaux. "Production of Net-Shape Static Parts by Direct HIPing of Nickel Base Superalloy Prealloyed Powders." Advanced Materials Research 278 (July 2011): 277–82. http://dx.doi.org/10.4028/www.scientific.net/amr.278.277.

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In order to reduce costs and increase the operating temperatures in aero-turboengines and space propulsion systems, net-shape or near net-shape production processes have been developed for static parts through HIPing (Hot Isostatic Pressing) of nickel base superalloys prealloyed powders. The presented results hereafter are related to the manufacturing processes and the mechanical properties (tensile, creep and LCF) characterisation. The effects of net shape surfaces and of surface conditioning have been investigated too. Examples of actual parts (CFM56 turbine casing and Vulcain rocket engine gas generator) illustrate the presentation. This study has confirmed the interest of this production route and future potential for development.

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Hou, Lanlan, Shuqian Cao, Tian Gao, and Shiyu Wang. "Vibration signal model of an aero-engine rotor-casing system with a transfer path effect and rubbing." Measurement 141 (July 2019): 429–41. http://dx.doi.org/10.1016/j.measurement.2019.02.049.

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Smith, E. O., A. J. Neely, and H. Palfrey-Sneddon. "The impact of gas turbine compressor rotor bow on aircraft operations." Aeronautical Journal 121, no. 1246 (December 2017): 1808–32. http://dx.doi.org/10.1017/aer.2017.117.

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ABSTRACTWhen a gas turbine engine is shut down it will develop a circumferential thermal gradient vertically across the compressor due to hot air rising from the cooling metal components and pooling at the top. As the hot compressor rotor drum and casing cool and contract in the presence of this thermal gradient, they do so non-uniformly and therefore will bend slightly, in a phenomenon known as rotor bow. Starting an engine under bowed conditions can result in damage, representing a risk to both airworthiness and operational capability. This study consolidates some preliminary findings by the authors relating to the drivers for rotor bow, such as engine geometry, aircraft-engine integration and rotor temperature on shutdown. The commercial and military operational considerations associated with rotor bow are also discussed, including limitations which may result from a bowed rotor; the influence of operations including the final flight and descent profiles, taxi procedures and rapid turnaround requirements; as well as some practical solutions which may be implemented to reduce the impact of rotor bow.

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Xu, Qingzong, Pei Wang, Qiang Du, Jun Liu, and Guang Liu. "Effects of axial length and integrated design on the aggressive intermediate turbine duct." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 233, no. 4 (September 4, 2018): 443–56. http://dx.doi.org/10.1177/0957650918797450.

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With the increasing demand of high bypass ratio and thrust-to-weight ratio in civil aero-engine, the intermediate turbine duct between the high pressure and low pressure turbines of a modern gas turbine tends to shorter axial length, larger outlet-to-inlet area ratio and high pressure-to-low pressure radial offset. This paper experimentally and numerically investigated the three-dimensional flow characteristics of traditional (ITD1) and aggressive intermediate turbine duct (ITD2) at low Reynolds number. The baseline case of ITD1 is representative of a traditional intermediate turbine duct of aero-engine design with non-dimensional length of L/dR = 2.79 and middle angle of 20.12°. The detailed flow fields inside ITD1 and flow visualization were measured. Results showed the migration of boundary layer and a pair of counter-rotating vortexes were formed due to the radial migration of low momentum fluid. With the decreasing axial length of intermediate turbine duct, the radial and streamwise reverse pressure gradient in aggressive intermediate turbine duct (ITD2) were increased resulting in severe three-dimensional separation of boundary layer near casing surface and higher total pressure loss. The secondary flow and separation of boundary layer near the endwall were deeply analyzed to figure out the main source of high total pressure loss in the aggressive intermediate turbine duct (ITD2). Based on that, employing wide-chord guide vane to substitute “strut + guide vane”, this paper designed the super-aggressive intermediate turbine duct and realized the suppression of the three-dimensional separation and secondary flow.

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Behera, Bikram, Priyabrata Mallick, Swadhin Kumar Patel, Asit Behera, Deepak Sahoo, and Ajit Behera. "Splat analysis of plasma sprayed (Al + Ni + h(BN)) homogenized mixture for improvement of abradable resistance on aero-engine inner casing surface." Materials Today: Proceedings 33 (2020): 5698–702. http://dx.doi.org/10.1016/j.matpr.2020.03.836.

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Papadakis, Loucas, and Carl Hauser. "Experimental and computational appraisal of the shape accuracy of a thin-walled virole aero-engine casing manufactured by means of laser metal deposition." Production Engineering 11, no. 4-5 (June 6, 2017): 389–99. http://dx.doi.org/10.1007/s11740-017-0746-3.

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Xiao, Denghong, Tian He, Xiandong Liu, and Yingchun Shan. "Novel Dispersion Curves Extraction Method for Waveguides Affected by Nonuniform Transient Temperature Field." Journal of Computational Acoustics 23, no. 02 (May 7, 2015): 1550007. http://dx.doi.org/10.1142/s0218396x15500071.

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Guided waves sensitivity to environmental and operational conditions, especially temperature fluctuations, is one of the major problems when the method is considered for real engineering applications. The aim of this paper is to propose a novel dispersion curves extraction method for waveguides affected by nonuniform transient temperature field. Essentially, the method is based on a simple and robust approach, consisting in a few series of modal analyses for a representative part of the inspected structure. To consider the effect of temperature, a thermal stress calculation based on finite element method is presented. In this way, for different wave lengths, the mode shapes and corresponding natural frequencies can be obtained by solving some thermal-eigenvalue problems. To test the theoretical thermal effect of the dispersion curves a experiment on an isotropic plate is conducted. Those theoretical dispersion curves, consisting of only dominant modes, are compared with dispersion curves obtained from experiment. Finally, this method is used to extract the dispersion curves of the aero-engine casing considering the nonuniform temperature field. The results not only give us insight to how temperature affects Lamb wave velocities in different frequency ranges but also will help those extracting dispersion curves for waveguides affected by nonuniform transient temperature field.

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Zhang, Yong, Yan Zhao, Yunyun Lu, and Huajiang Ouyang. "Bayesian identification of bolted-joint parameters using measured power spectral density." Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability 234, no. 2 (November 29, 2019): 260–74. http://dx.doi.org/10.1177/1748006x19889146.

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A Bayesian method for the optimal estimation of parameters that characterize a bolted joint based on measured power spectral density is proposed in this article. Due to uncertainties such as measurement noise and modelling errors, it is difficult to identify joint parameters of a bolted structure accurately with incomplete measured response data. In this article, using the Bayesian probability framework to describe the uncertainty of the joint parameters and using the power spectrum of the structural response of the single-point/multi-point excitation as measurements, the conditional probability density function of the joint parameters is established. Then, the Bayesian maximum posterior estimation is performed by an optimization method. Two simplified bolted-joint models are built in the numerical examples. First, the feasibility of the proposed method in the undamped model is proved. Then, taking advantage of multi-point excitation, the identification accuracy of the proposed method in the damped model is improved. The numerical results show that the proposed method can accurately identify the stiffness and damping characteristics of joint parameters with good robustness to noise. Finally, the joint parameters of the finite element model for an aero-engine casing are identified by the proposed method with satisfactory accuracy.

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Liu, Lulu, Shikai Yin, Gang Luo, Zhenhua Zhao, and Wei Chen. "The Influences of Projectile Material and Environmental Temperature on the High Velocity Impact Behavior of Triaxial Braided Composites." Applied Sciences 11, no. 8 (April 13, 2021): 3466. http://dx.doi.org/10.3390/app11083466.

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Two-dimensional (2D) triaxial braided composites with braiding angle (± 60°/0°) have been used as aero-engine containing casing material. In the current paper, three types of projectile with the same mass and equivalent diameter, including cylinder gelatin projectile, carbon fiber-reinforced plastics (CFRP), and titanium alloy blade-like projectile, were employed to impact on triaxial braided composites panels with thickness of 4.3 mm at room temperature (20 °C) to figure out the influences of projectile materials on the damage pattern and energy absorption behavior. Furthermore, the influences of environmental temperature were also discussed considering the aviation service condition by conducting ballistic impact tests using CFRP projectile at cryogenic temperature (−50 °C) and high temperature (150 °C). The triaxial braided target panel were pre-heated or cooled in a low-temperature chamber before mounted. It is found that soft gelatin project mainly causes global deformation of the target and therefore absorb much more energy. The triaxial braided composite absorb 77.59% more energy when impacted with CFRP projectile than that with titanium alloy projectile, which mainly results in shear fracture. The environmental temperature has influences on the damage pattern and energy absorption of triaxial braided composites. The cryogenic temperature deteriorates the impact resistance of the triaxial braided composite material with matrix cracking damage pattern, while high temperature condition improves its impact resistance with shearing fracture damage pattern.

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Torres Cedillo, Sergio G., and Philip Bonello. "Empirical identification of the inverse model of a squeeze-film damper bearing using neural networks and its application to a nonlinear inverse problem." Journal of Vibration and Control 24, no. 2 (April 7, 2016): 357–78. http://dx.doi.org/10.1177/1077546316640985.

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The identification of nonlinear squeeze-film damper (SFD) bearings, typically used in aero-engines, has so far focused on their forward model (i.e. displacement input/force output). The contributions of this paper are the non-parametric identification of the inverse model of the SFD bearing (force input/displacement output) from empirical data, and its application to a nonlinear inverse rotor-bearing problem. This work is motivated by the need for a reliable substitute for internal instrumentation, to enable the identification of rotor unbalance using vibration data from externally mounted sensors, in applications where the rotor is inaccessible under operating conditions and there is no adequate linear connection between rotor and casing. The identification of the inverse model is fundamentally different from that of the forward model due to the need to account for system memory. A suitably trained Recurrent Neural network (RNN) is shown to be capable of identifying the inverse model of an actual SFD through two validation studies. In the first study, the RNN model satisfactorily predicted the SFD journal’s displacement time histories for given periodic time histories of the Cartesian SFD forces, although it could not predict the user-applied static offset in the SFD since it was not trained to do so. This was no limitation for the second study where, for both centred and non-centred SFD conditions, the RNN proved to be a reliable substitute for actual instrumentation as part of the inverse problem solution process for identifying the amplitudes and phases of the external excitation forces on a simple test rig.

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Xiao, Jiaguangyi, Yong Chen, Jie Tian, Hua Ouyang, and Anjenq Wang. "Analysis of Composite Blade/Casing Rub Stability Through Delayed Differential Equations." Journal of Engineering for Gas Turbines and Power 142, no. 1 (November 28, 2019). http://dx.doi.org/10.1115/1.4044570.

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Abstract To improve aerodynamic efficiencies, the clearances between blades and casings are becoming smaller and smaller in the aero-engine industry, which might lead to the interactions between these components. These unexpected interactions are known as the so-called blade/casing rubs. Abradable materials are implemented on the inner surface of the casings to reduce the potential damages caused by it. However, failures may still arise from blade/casing rubs according to experimental investigations and actual accidents. In this paper, a reduced-order delayed differential equations (DDEs) are used to simplify the rubbing process between composite blade and casing. It is assumed that the removal of the abradable material in blade/casing rubbing process shares a resemblance with machine tool chatters encountered in machining. The DDEs are established with centrifugal stiffness and the impacts of stacking sequences on the blade damping taking into consideration. Semidiscretization method (SDM) is used to study the stabilities of the simplified system, which is verified by cluster treatment of characteristic roots (CTCR) and direct integrations. The results show that the stacking sequences, rub positions, blade damping, and stiffness could have much impact on the relatively dangerous interaction regimes. With the help of this method, one can assist the design processes of the composite blade-casing interface in initial aero-engine structural designs.

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Chen, G., T. F. Hao, H. F. Wang, B. Zhao, J. Wang, and X. Y. Cheng. "Sensitivity Analysis and Experimental Research on Ball Bearing Early Fault Diagnosis Based on Testing Signal From Casing." Journal of Dynamic Systems, Measurement, and Control 136, no. 6 (August 8, 2014). http://dx.doi.org/10.1115/1.4027926.

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The ball bearings of an aero-engine are key parts that frequently fail, and it is very important to effectively carry out fault diagnosis of the ball bearings. However, in the present research work, the ball bearing faults characteristics are extracted mainly from the bearing house signals, it is well known that usually only the casing signals can be measured in practical aero-engine test, and the ball bearing faults characteristics will greatly weaken after transmitting to the casing from the bearing house, therefore, it is very important to extract the fault characteristics of ball bearings from casing vibration signals for the ball bearing fault diagnosis in the practical aero-engine. In this study, simulation experiments for ball bearing faults are conducted using two rotor experimental rigs with casings. In addition, by means of the impulse response method, the transfer characteristics from the ball bearings to casing measuring points are measured, and a sensitivity analysis is performed. Faults are created on the inner ring, outer ring, and ball of the ball bearings in the two experimental rigs. The ball bearing experiments are carried out, and the fault features are extracted by means of a wavelet envelope analysis. The experimental results indicate that, with high connection stiffness between the bearing house and the casing, there is little vibration attenuation. However, with low connection stiffness, the vibration attenuation is great. After the impulse vibrations caused by the ball bearing faults are transmitted to the casing, the casing vibration is very weak and is often submerged in other signals. However, the ball bearing fault characteristic frequencies can still be effectively extracted from the weak casing vibration signals by using a wavelet envelope analysis. The research results in this study provide an experimental basis for a ball bearing fault diagnosis based on a casing test signal from a practical aero-engine.

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CAO, Zhenzhong, Fan ZHANG, Dingguo ZHANG, Yi YU, Liang LI, and Xian GUO. "Failure mechanisms of bolted flanges in aero-engine casings subjected to impact loading." Chinese Journal of Aeronautics, May 2021. http://dx.doi.org/10.1016/j.cja.2021.04.004.

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C, Mukundhan, Sivaraj P, Balasubramanian V, and Vijay Petley. "MICROSTRUCTURAL AND MECHANICAL ASPECTS OF FRICTION WELDED DISSIMILAR JOINTS FOR AERO ENGINE APPLICATION." Journal of Manufacturing Engineering 14, no. 2 (June 2019). http://dx.doi.org/10.37255/jme.v4i2pp101-105.

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Gas turbine engines demand material with unique properties like high-temperature oxidation and corrosion resistance, high specific strength, etc. All over the world material development to meet these requirements has led to the development of novel alloys. While Titanium base alloys are used in the low-temperature regime of the gas turbine engine, Nickel-basedsuperalloys are used for hot end components of the engine. With the increase in the temperature requirement for the turbine parts, the form of the Ni-based superalloys changed from wrought to cast superalloys. As an inherent process of investment cast superalloy blades and vanes which has serpentine passages for air cooling, these passages are required to be closed after casting. The numerous adapters also need to be joined on the cast superalloy casings for various instrumentation, lube oil ports. These cast superalloys are nonweldable and joining these pose a challenge. In this present investigation, the joining of the Nibasedsuperalloy BZL12Y and martensitic stainless steel AE961W using rotary friction welding process. The mechanical properties of the dissimilar joints were evaluated as per the ASTM standards. Microstructural features of various regions of welded joints using optical microscopy (OM) and scanning electron microscopy (SEM). The material is welded in different condition to obtain the maximum tensile strength of the weld joint. From this investigation, it was found that the combination of aging and h & t condition weld joint gives good strength and a stable hardness value. Correlation between tensile properties and microstructural features were analyzed and reported in this paper.

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"Assessment of Mechanical Design Parameters for an Aero Gas Turbine Engine Jet Pipe Casing using Finite Element Analysis." International Journal of Engineering and Advanced Technology 9, no. 5 (June 30, 2020): 1197–201. http://dx.doi.org/10.35940/ijeat.e1072.069520.

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Aero Gas Turbine engines power aircrafts for civil transport application as well as for military fighter jets. Jet pipe casing assembly is one of the critical components of such an Aero Gas Turbine engine. The objective of the casing is to carry out the required aerodynamic performance with a simultaneous structural performance. The Jet pipe casing assembly located in the rear end of the engine would, in case of fighter jet, consist of an After Burner also called as reheater which is used for thrust augmentation to meet the critical additional thrust requirement as demanded by the combat environment in the war field. The combustion volume for the After burner operation together with the aerodynamic conditions in terms of pressure, temperature and optimum air velocity is provided by the Jet pipe casing. While meeting the aerodynamic requirements, the casing is also expected to meet the structural requirements. The casing carries a Convergent-Divergent Nozzle in the downstream side (at the rear end) and in the upstream side the casing is attached with a rear mount ring which is an interface between engine and the airframe. The mechanical design parameters involving Strength reserve factors, Fatigue Life, Natural Frequencies along with buckling strength margins are assessed while the Jet pipe casing delivers the aerodynamic outputs during the engine operation. A three dimensional non linear Finite Element analysis of the Jet pipe casing assembly is carried out, considering the up & down stream aerodynamics together with the mechanical boundary conditions in order to assess the Mechanical design parameters.

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Ma, Yingqun, Qingjun Zhao, Kai Zhang, Meng Xu, and Wei Zhao. "Analysis of Instantaneous Vibrational Energy Flow for an Aero-Engine Dual-Rotor–Support–Casing Coupling System." Journal of Engineering for Gas Turbines and Power 142, no. 5 (April 29, 2020). http://dx.doi.org/10.1115/1.4046418.

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Abstract The aero-engine casing is a key component for carrying loads. With the purpose of improving the thrust-weight ratio of the aero-engine, the casing is required to be designed to be as thin as possible. Therefore, the vibration of aero-engine's rotor, support, and casing will be easily coupled causing the whole engine's vibration to be more serious. Considering the structural vibration propagation is essentially the vibration energy transmission, the structural intensity (SI) method is popular and widely used to investigate the transmission phenomena of vibration energy in vibrating structures. This method combines forces with velocities to quantify the vibrational energy flow (VEF) transmitted in the structures by its directions and magnitude. Therefore, the SI fields are quantified by the developed computation system which combines the finite element design language and the in-house code. And a model of dual-rotor–support–casing coupling system subjected to the unbalanced forces of the rotors is established in this paper. The scalar and vector diagrams of instantaneous SI fields are visualized to show the main vibration energy transmission paths among these three parts. Moreover, the relationship between the SI and the mechanical energy is derived from the kinetic equation. According to this relationship, the phenomenon that the vibration energy and the strain energy are always converted to each other in the middle part of the rotor shaft with the first-order bending mode is discussed, which reveals the cause of the first-order bending mode of the rotor from a microscopic point of view.

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Qu, M. J., and G. Chen. "Effect of the Aero-Engine Mounting Stiffness on the Whole Engine Coupling Vibration." Journal of Engineering for Gas Turbines and Power 140, no. 7 (April 10, 2018). http://dx.doi.org/10.1115/1.4038542.

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A finite element (FE) model of the rotor tester of an aero-engine, having a thin-walled casing structure, mounted with the way of an actual engine, is developed to simulate the intrinsic vibration characteristics under actual engine-mounting condition. First, a modal experiment of the rotor tester for the whole aero-engine is conducted, and the FE model is modified and validated based on the modal experimental results. Second, the first three orders of natural frequencies and the modal shapes are evaluated using the modified FE model under three different types of mounting stiffness, namely, a fixed mounting boundary, a free mounting boundary, and a flexible mounting boundary. Subsequently, the influences of the mounting stiffness on the coupling vibration of the rotor and stator are studied via a new rotor–stator coupling factor, which is proposed in this study. The results show that the higher the rotor–stator coupling degree of the modal shape, the greater the influence of the mounting condition on the modal shape. Moreover, the influence of the mounting stiffness on the rotor–stator coupling degree is nonlinear. The coupling phenomena of the rotor and stator exist in many modal shapes of actual large turbofan engines, and the effect of mounting stiffness on the rotor–stator coupling cannot be ignored. Hence, the mounting stiffness needs to be considered carefully while modeling the whole aero-engine and simulating the dynamic characteristics of the whole aero-engine.

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Li, Baoxu. "Performance Simulation for the Supporting Structure of Aero-Engine Rotor in Wide Frequency Domain." International Journal of Vehicle Structures and Systems 11, no. 5 (December 31, 2019). http://dx.doi.org/10.4273/ijvss.11.5.14.

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The inertia load of aero-engine indeterminate rotor support is calculated by the finite element method coupled with plane stress element and Fourier ring element. Without considering the dynamic characteristics of rotor’s supporting structure, the test results are error-prone and inefficient. A new method for testing the supporting structure performance of aero-engine rotor in wide frequency domain is proposed. On this basis, the structural model of the casing-support and the structural model of aero-engine rotor are constructed by substructure modelling method. Combining the two sub-models, the semi-physical simulation model of the vibration of the engine rotor’s supporting structure is obtained. By superimposing the additional dynamic stiffness matrix of the casing-supporting structure at the designated DOF position in the overall stiffness matrix of the finite element model of the rotor structure, the overall stiffness matrix of the aero-engine rotor supporting structure is obtained. The effective stiffness matrix can be used to calculate the structural dynamic characteristics of aero-engine rotor supporting structure. Experiments show that the average error of the proposed method is 0.0023 and the number of units is 7.98 e4. The calculation time and storage space are reduced by 310 minutes and 166 GB respectively compared with the performance test method of rotor support based on finite element analysis, which shows that the proposed method is more efficient and accurate.

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Marn, Andreas, Dominik Broszat, Thorsten Selic, Florian Schönleitner, and Franz Heitmeir. "Comparison of the Aerodynamics of Acoustically Designed Exit Guide Vanes and a State-of-the-Art Exit Guide Vane." Journal of Turbomachinery 137, no. 4 (October 28, 2014). http://dx.doi.org/10.1115/1.4028457.

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Within previous EU projects, possible modifications to the engine architecture have been investigated, which would allow for an optimized aerodynamic or acoustic design of the exit guide vanes (EGVs) of the turbine exit casing (TEC). However, the engine weight should not be increased and the aerodynamic performance must be at least the same. This paper compares a state-of-the art TEC (reference TEC) with typical EGVs with an acoustically optimized TEC configuration for the engine operating point approach. It is shown that a reduction in sound power level for the fundamental tone (one blade passing frequency (BPF)) for this acoustically important operating point can be achieved. It is also shown that the weight of the acoustically optimized EGVs (only bladings considered) is almost equal to the reference TEC, but a reduction in engine length can be achieved. Measurements were conducted in the subsonic test turbine facility (STTF) at the Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology. The inlet guide vanes (IGVs), the low pressure turbine (LPT) stage, and the EGVs have been designed by MTU Aero Engines.

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Chen, G. "A New Rotor-Ball Bearing-Stator Coupling Dynamics Model for Whole Aero-Engine Vibration." Journal of Vibration and Acoustics 131, no. 6 (November 19, 2009). http://dx.doi.org/10.1115/1.4000475.

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In this paper, a new rotor-ball bearing-stator coupling system dynamics model is established for simulating the practical whole aero-engine vibration. The main characteristics of the new model are as follows: (1) the coupling effect between rotor, ball bearing, and stator is fully considered; (2) the elastic support and the squeeze film damper are considered; (3) the rotor is considered as an Euler free beam of equal-section model, and its vibration is analyzed through truncating limited modes; (4) nonlinear factors of ball bearing such as the clearance of bearing, nonlinear Hertzian contact force, and the varying compliance vibration are modeled; and (5) rubbing fault between rotor and stator is considered. The Zhai method, which is a new explicit fast numerical integration method, is employed to obtain system’s responses, and the whole aero-engine vibration characteristics are studied. Finally, aero-engine tester including casing is established to carry out rubbing fault experiment, the simulation results from rotor-ball bearing-stator coupling model are compared with the experiment results, and the correctness of the new model is verified to some extent.

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Wang, H. F., G. Chen, and P. P. Song. "Simulation Analysis of Casing Vibration Response and Its Verification Under Blade–Casing Rubbing Fault." Journal of Vibration and Acoustics 138, no. 3 (March 21, 2016). http://dx.doi.org/10.1115/1.4032512.

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A new rotor–stator rubbing model considering the blade–casing rubbing fault is put forward in this paper. The model couples the rotor together with its suspension (ball or roller bearings), the disk, the (multiple) blades, and the casing. In addition, the influence of the rotor–stator clearance on rubbing forces was considered. It can simulate rubbing faults for single-point rubbing on the casing and complete-cycle rubbing on the rotor. The new rubbing model was applied to the rotor–support–casing coupling model, and the casing acceleration response under rubbing faults was obtained by the time-integration approach. The casing acceleration response, blade tip response, and rubbing force were analyzed. An aero-engine rotor tester, including casing, was used to carry out the rubbing experiment for single-point rubbing on the casing and for whole-cycle rubbing on the rotor. The simulation results were found in highly consistent with the experimental results, which fully verified the effectiveness of the new blade–casing rubbing model.

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Coull, John D., and Nicholas R. Atkins. "The Influence of Boundary Conditions on Tip Leakage Flow." Journal of Turbomachinery 137, no. 6 (June 1, 2015). http://dx.doi.org/10.1115/1.4028796.

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Much of the current understanding of tip leakage flow has been derived from detailed cascade studies. Such experiments are inherently approximate since it is difficult to simulate the boundary conditions that are present in a real machine, particularly the secondary flows convecting from the upstream stator row and the relative motion of the casing and blade. The problem is further complicated when considering the high pressure turbine rotors of aero engines, where the high Mach numbers must also be matched in order to correctly model the aerodynamics and heat transfer of the leakage flow. More engine-representative tests can be performed on high-speed rotating turbines, but the experimental resolution achievable in such setups is limited. In order to examine the differences between cascade and engine boundary conditions, this paper presents a numerical investigation into the impact of inlet conditions and relative casing motion (RCM) on the leakage flow of a high-pressure turbine rotor. The baseline calculation uses a simplified inlet condition and no relative endwall motion, in typical cascade fashion. Only minor changes to the leakage flow are induced by introducing either a more realistic inlet condition or RCM. However, when both of these conditions are applied simultaneously, the pattern of leakage flow is significantly altered, with ingestion of flow over much of the early suction surface. The paper explores the physical processes driving the changes, the impact on performance and the implications for future experimental investigations.

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Wang, H. F., G. Chen, and P. P. Song. "Asynchronous Vibration Response Characteristics of Aero-Engine With Support Looseness Fault." Journal of Computational and Nonlinear Dynamics 11, no. 3 (October 23, 2015). http://dx.doi.org/10.1115/1.4031245.

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In this paper, the mechanism of the asynchronous vibration response phenomenon caused by the looseness fault in the aero-engine whole vibration system is investigated by numerical integration methods. A single degree-of-freedom (DOF) lumped mass model and a rotor-casing whole vibration model of a real engine are established, and two looseness fault models are introduced. The response of these two systems is obtained by numerical integration methods, and the asynchronous response characteristics are analyzed. By comparing the response of a single DOF lumped mass model with the response of multiple DOF model, the reason leading to the asynchronous response characteristics is the relationship between the changing period of stiffness and the changing period of the rotational speed. When the changing period of stiffness is equivalent to the changing period of the rotational speed, frequency multiplication will appear and the natural frequency will be excited at specific speeds. When the changing period of stiffness is equivalent to n (n = 2, 3,…) times the changing period of the rotating speed, 1/n (n = 2, 3,…) frequency division and frequency multiplication will appear and the natural frequency will be excited at specific speeds.

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Li, Bingqiang, Honggen Zhou, Jinfeng Liu, and Chao Kang. "Modeling and dynamic characteristic analysis of dual rotor-casing coupling system with rubbing fault." Journal of Low Frequency Noise, Vibration and Active Control, September 7, 2021, 146134842110393. http://dx.doi.org/10.1177/14613484211039322.

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With the rapid development of aero-engine manufacturing technology, the dual-rotor system has been employed in part of turbofan engine in order to improve the working performance of aircraft more efficiently. In this study, taking the counter-rotation dual-rotor as the research object, the dynamic model of dual rotor-casing coupling system is established by the aid of MATLAB. The dynamic frequency curves are in good agreement with the results in references and calculated by FEM method, that shows the validity and feasibility of the model. The local rub-impact dynamic model of dual rotor-casing coupling system is established, and rubbing analysis is carried out using Newmark- β method. The effects of rotating speed and speed ratio on local rub-impact response are deeply discussed. The results show that with the increase of rotating speed, combined frequencies and frequency multiplication components are more significant. In addition, speed ratio has a great influence on the periodic motion of the system. With the increase of the absolute value of the speed ratio, the whirl radius of the outer rotor and the normal rubbing force increase dramatically.

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48

Da Soghe, Riccardo, Lorenzo Mazzei, Lorenzo Tarchi, Lorenzo Cocchi, Alessio Picchi, Bruno Facchini, Laurent Descamps, Julian Girardeau, and Matthieu Simon. "Development of Experimental and Numerical Methods for the Analysis of Active Clearance Control Systems." Journal of Engineering for Gas Turbines and Power, December 17, 2020. http://dx.doi.org/10.1115/1.4049354.

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Abstract To increase the performance of modern aero-engines, the control of blade tip leakages in mandatory. In the last decades, this task was performed by Active Clearance Control (ACC) systems, which manage the casing thermal deformations and the associated losses via cooling jets impinging on the casing outer surface. The current trend of increasing the engine by-pass ratio pushes the limits of ACC traditional design, since a lower pressure head is available for the generation of the jets. Therefore, denser jet patterns and lower jet-to-target distances are required to compensate the reduction of the jets' Reynolds number. Literature correlations for the estimation of impingement heat transfer are then out of their confidence range, and also RANS numerical approaches appear not to be suitable. In this work, methodologies for the development of accurate and reliable tools to determine the heat transfer characteristics of low pressure ACC systems are presented. More precisely, this paper describes a custom designed finite difference procedure capable of solving the inverse conduction problem on the target plate of a test sample. The methodology was successfully applied to an experimental setup for the measurement of the heat transfer features of a representative low pressure ACC system. The experimental data was then used to validate a suitable numerical approach. Results show that RANS is not able to mimic the experimental trends, while scale-resolving turbulence models provide a good reconstruction of the experimental evidences, thus allowing to obtain a correct interpretation of flow and thermal phenomena.

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Guru, Siddhartha S., S. Shylaja, Sunil Kumar, and Ramesh Murthy. "Pre-emptive Rotor Blade Damage Identification by Blade Tip Timing Method." Journal of Engineering for Gas Turbines and Power 136, no. 7 (February 27, 2014). http://dx.doi.org/10.1115/1.4026802.

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The blade tip timing (BTT) method uses the differential arrival timings of the blades at case-mounted sensors to effectively characterize the vibrations of all blades in a rotor. This paper studies the use of the BTT method for pre-emptive prediction of rotor blade damage; through a careful monitoring of blade natural frequencies in conjunction with the blade tip position during an engine test. In the current study, the low pressure turbine stage of a developmental aero engine is instrumented with a combination of eddy current and optical sensors located circumferentially on the casing. This instrumentation effectively captures the engine order resonances of interest for the blade bending mode. During one of the normal engine tests, one of the blades in the LPT stage suddenly showed a drop in natural frequency beyond the allowable scatter and an abrupt change in the blade tip position. As the engine test was continued further, this drop in blade natural frequency and change in blade tip position progressively increased towards blade failure limits. Suspecting a propagating crack in the particular blade, the test was aborted and the engine was withdrawn for detailed inspection. Inspection of the rotor blades confirmed the presence of significant aerofoil crack in the suspect blade.

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Bauinger, Sabine, Emil Goettlich, Franz Heitmeir, and Franz Malzacher. "Influence of Backward- and Forward-Facing Steps on the Flow Through a Turning Mid Turbine Frame." Journal of Turbomachinery 139, no. 12 (September 26, 2017). http://dx.doi.org/10.1115/1.4037859.

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For this work, reality effects, more precisely backward-facing steps (BFSs) and forward-facing steps (FFSs), and their influence on the flow through a two-stage two-spool turbine rig under engine-relevant conditions were experimentally investigated. The test rig consists of an high pressure (HP) and an low pressure (LP) stage, with the two rotors rotating in opposite direction with two different rotational speeds. An S-shaped transition duct, which is equipped with turning struts (so-called turning mid turbine frame (TMTF)) and making therefore a LP stator redundant, connects both stages and leads the flow from a smaller to a larger diameter. This test setup allows the investigation of a TMTF deformation, which occurs in a real aero-engine due to non-uniform warming of the duct during operation—especially during run up—and causes BFSs and FFSs in the flow path. This happens for nonsegmented ducts, which are predominantly part of smaller engines. In the case of the test rig, steps were not generated by varying temperature but by shifting the TMTF in horizontal direction while the rotor and its casing were kept in the same position. In this way, both BFSs and FFSs between duct endwalls and rotor casing could be created. In order to avoid steps further downstream of the interface between HP rotor and TMTF, the complete aft rig was moved laterally too. In this case, the aft rig incorporates among others the LP rotor, the LP rotor casing, and the deswirler downstream of the LP stage. In order to catch the influence of the steps on the whole flow field, 360 deg rake traverses were performed downstream of the HP rotor, downstream of the duct, and downstream of the LP rotor with newly designed, laser-sintered combi-rakes for the measurement of total pressure and total temperature. Only the compact design of the rakes, which can be easily realized by additive manufacturing, makes the aforementioned 360 deg traverses in this test rig possible and allows a number of radial measurements positions, which is comparable to those of a five-hole probe. To get a more detailed information about the flow, also five-hole probe measurements were carried out in three measurement planes and compared to the results of the combi-rakes.

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Journal articles on the topic 'Aero engine casings'

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