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Artykuły w czasopismach na temat "BLADE ROUGHNESS"
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Chen, Yan, Chunxiang Gao i Wuli Chu. "Effect and Mechanism of Roughness on the Performance of a Five-Stage Axial Flow Compressor". Aerospace 9, nr 8 (4.08.2022): 428. http://dx.doi.org/10.3390/aerospace9080428.
Pełny tekst źródłaStreszczenie:
In order to prolong the service life of multistage axial compressors, it is increasingly important to study the influence of blade surface roughness on the compressor performance. In this paper, a five-stage axial compressor of a real aero-engine was selected as the research object, and an equivalent gravel roughness model was used to model the roughness based on measured blade surface roughness data. Furthermore, the impact of blade surface roughness on the performance at design rotational speed was studied by full three-dimensional numerical simulation, and the mechanism of performance variation caused by the roughness was discussed combined with quantitative and flow field analyses. The results show that, when the blade surface roughness of all blades increases, the peak total efficiency decreases by approximately 0.4%, the blocking mass-flow decreases by approximately 0.3%, and the stable working range changes little. When the surface roughness of all rotor blades increases, the performance decline is close to that of all rotor and stator blades, and the variation in stator blade roughness has little effect on the compressor performance. Regarding the variation in roughness, the performance of the latter stage is more sensitive than that of the previous stage, and the decline in the performance of the fifth stage contributes the most to the total performance degradation of the compressor. Once the surface roughness of the fifth-stage rotor blade increases, the flow in the middle of the rotor blade deteriorates and the stage performance decreases obviously, which is the main reason for the decline in the overall performance.
2
Yun, Yong Il, Il Young Park i Seung Jin Song. "Performance Degradation due to Blade Surface Roughness in a Single-Stage Axial Turbine". Journal of Turbomachinery 127, nr 1 (1.01.2005): 137–43. http://dx.doi.org/10.1115/1.1811097.
Pełny tekst źródłaStreszczenie:
Turbine blades experience significant surface degradation with service. Previous studies indicate that an order-of-magnitude or greater increase in roughness height is typical, and these elevated levels of surface roughness significantly influence turbine efficiency and heat transfer. This paper presents measurement and a mean-line analysis of turbine efficiency reduction due to blade surface roughness. Performance tests have been conducted in a low-speed, single-stage, axial flow turbine with roughened blades. Sheets of sandpaper with equivalent sandgrain roughnesses of 106 and 400 μm have been used to roughen the blades. The roughness heights correspond to foreign deposits on real turbine blades measured by Bons et al. [1]. In the transitionally rough regime (106 μm), normalized efficiency decreases by approximately 4% with either roughened stator or roughened rotor and by 8% with roughness on both the stator and rotor blades. In the fully rough regime (400 μm), normalized efficiency decreases by 2% with roughness on the pressure side and by 6% with roughness on the suction side. Also, the normalized efficiency decreases by 11% with roughness only on stator vanes, 8% with roughness only on rotor blades, and 19% with roughness on both the stator and rotor blades.
3
Liu, Chen, Yipeng Cao, Sihui Ding, Wenping Zhang, Yuhang Cai i Aqiang Lin. "Effects of blade surface roughness on compressor performance and tonal noise emission in a marine diesel engine turbocharger". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 234, nr 14 (9.06.2020): 3476–90. http://dx.doi.org/10.1177/0954407020927637.
Pełny tekst źródłaStreszczenie:
A numerical study was conducted to investigate the effects of blade surface roughness on compressor performance and tonal noise emission. The equivalent sand-grain roughness model was used to account for blade surface roughness, and a hybrid method that combines computational fluid dynamics and boundary element method was used to predict compressor performance and tonal noise. The numerical approach was validated against experimental data for a baseline compressor. Nine different cases with different blade surface roughness were studied in this paper, the global performance was analyzed under compressor design speed, and the tonal noise level was predicted under the design condition. The results indicate that compressor total-to-total pressure ratio and isentropic efficiency were gradually decreased with the increasing blade surface roughness. Besides, the blade total pressure loss coefficient and the efficiency loss coefficient were also increased. It was found that the reverse flow at the leading edge of compressor rotor blades reduced blade loading. The pressure fluctuation at the leading edge showed that the peak of pressure fluctuations increased as the blade surface roughness was increased. The sound pressure level at blade-passing frequency shows a significant change with variation in blade surface roughness, which results in an increased total noise level. Furthermore, it was shown that the blade surface roughness had nearly no influence on acoustic directivity, but the sound pressure level increased with the increase in roughness, especially at blade-passing frequency.
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Tangler, J. L. "Influence of Pitch, Twist, and Taper on a Blade’s Performance Loss due to Roughness". Journal of Solar Energy Engineering 119, nr 3 (1.08.1997): 248–52. http://dx.doi.org/10.1115/1.2888027.
Pełny tekst źródłaStreszczenie:
The purpose of this study was to determine the influence of blade geometric parameters such as pitch, twist, and taper on a blade’s sensitivity to leading edge roughness. The approach began with an evaluation of available test data of performance degradation due to roughness effects for several rotors. In addition to airfoil geometry, this evaluation suggested that a rotor’s sensitivity to roughness was also influenced by the blade geometric parameters. Parametric studies were conducted using the PROP93 computer code with wind tunnel airfoil characteristics for smooth and rough surface conditions to quantify the performance loss due to roughness for tapered and twisted blades relative to a constant-chord nontwisted blade at several blade pitch angles. The results indicate that a constant-chord nontwisted blade pitched toward stall will have the greatest losses due to roughness. The use of twist, taper, and positive blade-pitch angles all help reduce the angle-of-attack distribution along the blade for a given wind speed and the associated performance degradation due to roughness.
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Özgen, Serkan, Eda Bahar Sarıbel i Ali Rıza Yaman. "Effect of blade contamination on power production of wind turbines". Journal of Physics: Conference Series 2265, nr 3 (1.05.2022): 032012. http://dx.doi.org/10.1088/1742-6596/2265/3/032012.
Pełny tekst źródłaStreszczenie:
Abstract Wind turbines suffer from considerable power losses because of contamination on their blades, that can be due to erosion, wear, smog, insect, sand and dust particle impact. Blade contamination, its effects on the flows over the wind turbine blades and consequent power production losses form the main focus of the present study. These effects are mainly due to increased roughness on the blades leading to earlier laminar-turbulent transition and consequently, thicker boundary-layers on the blades. Early laminar-turbulent transition leads to a larger part of the flow over a blade being turbulent, thus increasing skin friction drag. Thicker boundary-layer on a blade results in blade profile being effectively modified, rendering the flow over the blade depart from ideal. In the present study, the effects of blade contamination on power output of contaminated wind turbine blades is investigated numerically using an in-house computational tool. Blade Element Momentum Method (BEM) combined with the Panel Method is used to calculate the local velocity and angle of attack at the blade sections, together with the power produced by the blade. Trajectories of particles causing contamination are calculated using Lagrangian approach, also yielding the impingement pattern of the particles on the blade surface, i.e. particle collection efficiency distribution. The effects of roughness on the boundary-layer flow are investigated by using an Integral Boundary-Layer Method, which yields the characteristics of the boundary-layer, i.e. laminar-turbulent transition location, increased skin-friction and thickening of the boundary-layer. The blade shape is modified due contamination thickness, the local height of which is assumed to be proportional to the local collection efficiency. Also, the roughness height distribution used in the boundary-layer calculations is assumed to be equal to the contamination thickness distribution on the blades. Power production and consequent losses of wind turbines with contaminated wind turbine blades are studied with respect to variations in particle size, wind speed and roughness height.
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Mulleners, K., P. Gilge i S. Hohenstein. "Impact of Surface Roughness on the Turbulent Wake Flow of a Turbine Blade". Journal of Aerodynamics 2014 (30.12.2014): 1–9. http://dx.doi.org/10.1155/2014/458757.
Pełny tekst źródłaStreszczenie:
Roughened aeroengine blade surfaces lead to increased friction losses and reduced efficiency of the individual blades. The surface roughness also affects the wake flow of the blade and thus the inflow conditions for the subsequent compressor or turbine stage. To investigate the impact of surface roughness on a turbulent blade wake, we conducted velocity field measurements by means of stereo particle image velocimetry in the wake of a roughened turbine blade in a linear cascade wind tunnel. The turbine blade was roughened at different chordwise locations. The influence of the chordwise location of the added surface roughness was examined by comparing their impact on the width and depth of the wake and, the positions and distribution of vortical structures in the wake. Additionally, the friction loss coefficients for different surface roughness positions were estimated directly from the velocity field.
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Gutiérrez, R., E. Llorente i D. Ragni. "Induced stalled flow due to roughness sensitivity for thick airfoils in modern wind turbines". Journal of Physics: Conference Series 2151, nr 1 (1.01.2022): 012001. http://dx.doi.org/10.1088/1742-6596/2151/1/012001.
Pełny tekst źródłaStreszczenie:
Abstract The mid-span region of wind turbine blades can be thickened to fulfil the structural requirements of the blade. Hence, thick airfoils, that were designed to operate at the root region of the blade, are moved to the mid-span region. This could not imply remarkable variations of the blade performance once its surface is smooth. However, the sensitivity of thick airfoils to roughness could cause significant aerodynamic impacts such as flow separation. This research aims to quantify the impact of the blade thickness, under smooth and rough conditions, in the annual energy production and the fatigue loads of the blade. Ten blade designs, linearly interpolated in thickness, are studied employing aero-elastic computations. The results reveal that the thickest blade increases the annual energy production by 5% with respect to the thinnest blade under rough conditions. Whereas this increase is less than 1% under smooth conditions. The loss of annual energy production varies with the blade thickness linearly for thin blades while it varies exponentially for thick blades up to 22%. Fatigue loads assessment confirmed a reduction of the damage equivalent load under smooth conditions, whereas the thickest blade increased it 28% under rough conditions.
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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.
Pełny tekst źródłaStreszczenie:
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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Caccia, Francesco, i Alberto Guardone. "Numerical simulations of ice accretion on wind turbine blades: are performance losses due to ice shape or surface roughness?" Wind Energy Science 8, nr 3 (15.03.2023): 341–62. http://dx.doi.org/10.5194/wes-8-341-2023.
Pełny tekst źródłaStreszczenie:
Abstract. Ice accretion on wind turbine blades causes both a change in the shape of its sections and an increase in surface roughness. These lead to degraded aerodynamic performances and lower power output. Here, a high-fidelity multi-step method is presented and applied to simulate a 3 h rime icing event on the National Renewable Energy Laboratory 5 MW wind turbine blade. Five sections belonging to the outer half of the blade were considered. Independent time steps were applied to each blade section to obtain detailed ice shapes. The roughness effect on airfoil performance was included in computational fluid dynamics simulations using an equivalent sand-grain approach. The aerodynamic coefficients of the iced sections were computed considering two different roughness heights and extensions along the blade surface. The power curve before and after the icing event was computed according to the Design Load Case 1.1 of the International Electrotechnical Commission. In the icing event under analysis, the decrease in power output strongly depended on wind speed and, in fact, tip speed ratio. Regarding the different roughness heights and extensions along the blade, power losses were qualitatively similar but significantly different in magnitude despite the well-developed ice shapes. It was found that extended roughness regions in the chordwise direction of the blade can become as detrimental as the ice shape itself.
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Hamed, Awatef A., Widen Tabakoff, Richard B. Rivir, Kaushik Das i Puneet Arora. "Turbine Blade Surface Deterioration by Erosion". Journal of Turbomachinery 127, nr 3 (1.03.2004): 445–52. http://dx.doi.org/10.1115/1.1860376.
Pełny tekst źródłaStreszczenie:
This paper presents the results of a combined experimental and computational research program to investigate turbine vane and blade material surface deterioration caused by solid particle impacts. Tests are conducted in the erosion wind tunnel for coated and uncoated blade materials at various impact conditions. Surface roughness measurements obtained prior and subsequent to the erosion tests are used to characterize the change in roughness caused by erosion. Numerical simulations for the three-dimensional flow field and particle trajectories through a low-pressure gas turbine are employed to determine the particle impact conditions with stator vanes and rotor blades using experimentally based particle restitution models. Experimental results are presented for the measured blade material/coating erosion and surface roughness. The measurements indicate that both erosion and surface roughness increase with impact angle and particle size. Computational results are presented for the particle trajectories through the first stage of a low-pressure turbine of a high bypass turbofan engine. The trajectories indicate that the particles impact the vane pressure surface and the aft part of the suction surface. The impacts reduce the particle momentum through the stator but increase it through the rotor. Vane and blade surface erosion patterns are predicted based on the computed trajectories and the experimentally measured blade coating erosion characteristics.
Rozprawy doktorskie na temat "BLADE ROUGHNESS"
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Vigueras, Zuniga Marco Osvaldo. "Analysis of gas turbine compressor fouling and washing on line". Thesis, Cranfield University, 2007. http://hdl.handle.net/1826/2448.
Pełny tekst źródłaStreszczenie:
This work presents a model of the fouling mechanism and the evaluation of compressor
washing on line. The results of this research were obtained from experimental and
computational models.
The experimental model analyzed the localization of the particle deposition on the blade
surface and the change of the surface roughness condition. The design of the test rig was
based on the cascade blade arrangement and blade aerodynamics. The results of the
experiment demonstrated that fouling occurred on both surfaces of the blade. This
mechanism mainly affected the leading edge region of the blade. The increment of the
surface roughness on this region was 1.0 μm. This result was used to create the CFD
model (FLUENT). According to the results of the CFD, fouling reduced the thickness of
the boundary layer region and increased the drag force of the blade.
The model of fouling was created based on the experiment and CFD results and was
used to calculate the engine performance in the simulation code (TURBOMATCH).
The engine performance results demonstrated that in five days fouling can affect the
overall efficiency by 3.5%. The evaluation of the compressor washing on line was based
on the experimental tests and simulation of the engine performance. This system
demonstrated that it could recover 99% of the original blade surface. In addition, this
system was evaluated in a study case of a Power Plant, where it proved itself to be a
techno-economic way to recover the power of the engine due to fouling.
The model of the fouling mechanism presented in this work was validated by
experimental tests, CFD models and information from real engines. However, for
further applications of the model, it would be necessary to consider the specific
conditions of fouling in each new environment.
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Wammack, James Edward. "Evolution of Turbine Blade Deposits in an Accelerated Deposition Facility: Roughness and Thermal Analysis". Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd1067.pdf.
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Fritzsche, Jörg. "Haftkräfte zwischen technisch rauen Oberflächen". Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2017. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-217698.
Pełny tekst źródłaStreszczenie:
Die eingereichte Dissertation beschäftigt sich mit der messtechnischen Erfassung sowie der Modellierung von Haftkräften zwischen rauen Oberflächen. Dabei wurden durch Variation von Flüssigkeiten sowie dem Nutzen beschichteter Oberflächen verschiedene Benetzungseigenschaften eingestellt und untersucht. Zusätzlich wurden neben dem Kontaktwinkel der untersuchten Systeme die freien Ober- und Grenzflächenenergien bestimmt und mit den Kräften korreliert. Es zeigte sich, dass Haftkräfte auf rauen Oberflächen stets über mehrere Größenordnungen verteilt vorliegen. Die Beschreibung der ermittelten Verteilungen ist dabei entweder durch statistischer Funktionen oder zumindest teils auch durch eine im Rahmen der Arbeit entwickelten Modellierung möglich. Weiterhin zeigte sich, dass eine Unterteilung in verschiedene Haftmechanismen (durch Kapillarbrücken oder van der Waals- sowie polare Wechselwirkungen) vorgenommen werden kann. Kapillarbrücken bilden dabei die größten Kräfte aus. Sie entstehen auf Grund nanoskaliger Blasen (Nanobubbles), welche vor allem auf schlecht benetzenden Oberflächen existieren.
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"Effect of blade surface roughness on profile loss and exit angle in a rectilinear steam turbine cascade". Thesis, 2002. http://localhost:8080/iit/handle/2074/5137.
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Wu, Jhih-Wei, i 吳志偉. "Numerical Study on the Aerodynamic Characteristics and Performance of the Roughness Applied on Blade in the Vertical Axis Wind Turbine". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/36nh42.
Pełny tekst źródłaStreszczenie:
碩士國立虎尾科技大學
航空與電子科技研究所
102
The vertical axis wind turbines have an advantage over the horizontal axis wind turbines such as easy installation, less susceptibility to wind shift and low noise. They are very suitable to be installed in urban and suburban region. The vertical axis-wind turbine has great potential for promoting green energy in residential life. Since the stall angle can be enhanced by increasing the roughness appropriately on blade surface. This study integrated the SST k-ω turbulence module into the computational fluid finite volume method to explore the aerodynamic characteristic of a three blade vertical axis wind turbine (VAWT) in different tip speed ratio and different roughness height (RH). It’s intended to find the optimal roughness height, to increase the efficiency of wind energy capture, and enhance the performance of the wind turbines. In the 2D VAWT ,increase λ the maximum average torque coefficient (Cq) is occurred at λ=2.5; The Cq is increase with λ as λ<2.5, and then decrease with λ as λ>2.5. The average Cq are larger than the smooth blade case as λ≦2. The average Cq are lower than the smooth blade case as λ≧2.5. Compare the smooth blade case, adding roughness on top and bottom surface of blade, the best roughness height is at RH=1x10-3m obtained average Cq enhance 67.86%、25.55% and 20.38% as λ=1、1.5 and 2 respectively. Compare the smooth blade case, adding roughness on top surface of blade, the best roughness height is at RH=1x10-4m obtained average Cq enhance 76.48%、49.11% and 26.60% as λ=1、1.5 and 2 respectively. Compare the smooth blade case, adding roughness RH=1x10-4m on front surface of blade, obtained average Cqenhance 60.59%、40.73% and 23.24% as λ=1、1.5 and 2 respectively. In the 3D VAWT ,increase λ the maximum average CQ is occurred at λ=2; The CQ is increase with λ as λ<2, and then decrease with λ as λ>2. The average CQ are larger than the smooth blade case as λ≦1.5. The average CQ are lower than the smooth blade case as λ≧2. Compare the smooth blade case, adding roughness on top and bottom surface of blade, the best roughness height is at RH=1x10-3m obtained average CQ enhance 39.40% as λ=0.5. The best roughness height is at RH=5x10-4m obtained average CQ enhance 48.90% and 10.20% as λ=1.5 and 2 respectively. Compare the smooth blade case, adding roughness on top surface of blade, the best roughness height is at RH=1x10-3m obtained average CQ enhance17.75%、30.88% and 30.76% as λ=0.5、1 and 1.5 respectively. Compare the smooth blade case, adding roughness on front 1/3 c surface of blade, the best roughness height is at RH=1x10-3m obtained average CQ enhance 41.87%、59.93% and 19.97% as λ=0.5、1 and 1.5 respectively. Compare the smooth blade case, adding roughness on top front 1/3 c surface of blade, the best roughness height is at RH=1x10-3m obtained average CQ enhance 35.42% and 3.79% as λ=1.5 and 2 respectively. In each of these cases, adding roughness RH=1x10-3m on top front 1/3 c surface of blade in VAWT is the best, the maximum average CQ is occurred at λ=2, but also improve performance.
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Chen, Yi-Hsiang, i 陳益祥. "The Effect of Blade Type and Roughness of Rear Wall on the Performance and the Acoustic Noise of the Cross Flow Fan". Thesis, 2005. http://ndltd.ncl.edu.tw/handle/269nvk.
Pełny tekst źródłaStreszczenie:
碩士國立臺北科技大學
冷凍空調工程系所
93
In order to improve the noise characteristics in the flow field of the cross flow fan (CFF), the present study adopted the CFD software-FLUENT to simulate the internal flow field of CFF and the sound pressure level by changing the blade type and wall roughness. Under the same of the rotational speed, the effects of different blade type and roughness on the fan performance and the characteristics of eccentric vortex were investigated. From the numerical results, it is found that: (1) the blade frequency tone for the fan can be significantly reduced by using the random pitch rotor instead of regular pitch rotor; (2) the fan performance decreases with the increase in the blade chord; (3) both blade frequency tone and volume flow rate decrease with the decrease in the blade angle; (4) changing the roughness has no apparent influence on the fan performance and the acoustic noise.
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Fritzsche, Jörg. "Haftkräfte zwischen technisch rauen Oberflächen". Doctoral thesis, 2016. https://tubaf.qucosa.de/id/qucosa%3A23101.
Pełny tekst źródłaStreszczenie:
Die eingereichte Dissertation beschäftigt sich mit der messtechnischen Erfassung sowie der Modellierung von Haftkräften zwischen rauen Oberflächen. Dabei wurden durch Variation von Flüssigkeiten sowie dem Nutzen beschichteter Oberflächen verschiedene Benetzungseigenschaften eingestellt und untersucht. Zusätzlich wurden neben dem Kontaktwinkel der untersuchten Systeme die freien Ober- und Grenzflächenenergien bestimmt und mit den Kräften korreliert. Es zeigte sich, dass Haftkräfte auf rauen Oberflächen stets über mehrere Größenordnungen verteilt vorliegen. Die Beschreibung der ermittelten Verteilungen ist dabei entweder durch statistischer Funktionen oder zumindest teils auch durch eine im Rahmen der Arbeit entwickelten Modellierung möglich. Weiterhin zeigte sich, dass eine Unterteilung in verschiedene Haftmechanismen (durch Kapillarbrücken oder van der Waals- sowie polare Wechselwirkungen) vorgenommen werden kann. Kapillarbrücken bilden dabei die größten Kräfte aus. Sie entstehen auf Grund nanoskaliger Blasen (Nanobubbles), welche vor allem auf schlecht benetzenden Oberflächen existieren.
Książki na temat "BLADE ROUGHNESS"
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Turbine Blade Surface Roughness Effects on Shear Drag and Heat Transfer. Storming Media, 2001.
Znajdź pełny tekst źródłaCzęści książek na temat "BLADE ROUGHNESS"
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Undreiner, S., i E. Dueymes. "Influence of the Blade Roughness on the Hydraulic Performance of a Mixed-Flow Pump. A Viscous Analysis". W Hydraulic Machinery and Cavitation, 428–37. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-010-9385-9_43.
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Ky, Le Hong, i Tran Vinh Hung. "The Effects of Technological Parameters on the Accuracy and Surface Roughness of Turbine Blades When Machining on CNC Milling Machines". W Lecture Notes in Mechanical Engineering, 276–84. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-99666-6_42.
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"The Mechanisms and Manifestations of Friction". W Tribomaterials, 13–46. ASM International, 2021. http://dx.doi.org/10.31399/asm.tb.tpsfwea.t59300013.
Pełny tekst źródłaStreszczenie:
Abstract This chapter reviews the types of friction that are of concern in tribological systems along with their associated causes and effects. It discusses some of the early discoveries that led to the development of friction laws and the understanding that friction is a system effect that can be analyzed based on energy dissipation. It describes the stick-slip behavior observed in wiper blades, the concept of asperities, and the significance of the shape, lay, roughness, and waviness of surfaces in sliding contact. It explains how friction forces are measured and how they are influenced by speed, load, and operating environment. It also covers rolling contact and fluid friction and the effect of lubrication.
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Antolin, William P., Aurélien Costes, Mélanie C. Rochoux i Patrick Le Moigne. "Accounting for the canopy drag effects on wildland fire spread in coupled atmosphere/fire simulations". W Advances in Forest Fire Research 2022, 959–64. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_145.
Pełny tekst źródłaStreszczenie:
While near-surface wind is the main influential parameter governing the fire rate of spread (ROS), its characterization remains key to simulate wildland fire behavior. The correct repre- sentation of the intensity and variability of the near-surface wind under complex terrain and vegetation remains an open problem but is essential to make a coupled atmosphere-fire model applicable to actual wildfires. In this work, we study the impact of canopy drag effects on the near-surface flow and the fire behavior simulated by the coupled Meso-NH/BLAZE model in the context of the FireFlux I experimental grass fire for which trees were located upstream and on the flanks. Drag effects can be activated in Meso-NH running in large-eddy simulation mode following work by Aumond et al. (2013). The drag approach formulation consists of adding drag terms to the momentum equation and subgrid turbulent kinetic energy dissipation as a function of the foliage density. This approach is compared to the standard roughness approach and to the homogeneous case considered in Costes et al. (2021) where homogeneous grass was considered over the whole computational domain. Results show the dynamical influence of the surrounding vegetation. Results also indicate that the choice of parameterization, due to the difference in the represented physics, induces differences on the fire front propagation. This encourages us to explore different options to accurately represent the surface boundary layer in presence of complex vegetation for coupled atmosphere-fire modeling in future work.
Streszczenia konferencji na temat "BLADE ROUGHNESS"
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Hummel, Frank, Michael Lo¨tzerich, Pasquale Cardamone i Leonhard Fottner. "Surface Roughness Effects on Turbine Blade Aerodynamics". W ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-53314.
Pełny tekst źródłaStreszczenie:
The aerodynamic performance of a turbine blade was evaluated via total pressure loss measurements on a linear cascade. The Reynolds number was varied from 600,000 to 1,200,000 to capture the operating regime for heavy-duty gas turbines. Four different types of surface roughness on the same profile were tested in the High Speed Cascade Wind Tunnel of the University of the German Armed Forces Munich and evaluated against a hydraulically smooth reference blade. The ratios of surface roughness to chord length for the test blade surfaces are in the range of Ra/c = 7.6×10−06 – 7.9×10−05. The total pressure losses were evaluated from wake traverse measurements. The loss increase due to surface roughness was found to increase with increasing Reynolds number. For the maximum tested Reynolds number of Re = 1,200,000 the increase in total pressure loss for the highest analysed surface roughness value of Ra = 11.8 μm was found to be 40% compared to a hydraulically smooth surface. The results of the measurements were compared to a correlation from literature as well as to well-documented measurements in literature. Good agreement was found for high Reynolds numbers between the correlation and the test results presented in this paper and the data available from literature.
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Back, Seung Chul, In Cheol Jeong, Jeong Lak Sohn i Seung Jin Song. "Influence of Surface Roughness on the Performance of a Compressor Blade in a Linear Cascade: Experiment and Modeling". W ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59703.
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Compressor blades experience significant surface degradation with service. Elevated levels of surface roughness reduce compressor efficiency and mass flow rate. This paper presents measurement and a new model of compressor blade performance degradation due to blade surface roughness. Performance tests have been conducted in a low-speed, linear cascade with roughened compressor blades. Equivalent sandgrain roughnesses of 12, 180, 300, 425, and 850 microns have been tested. These roughness values are representative of compressor blade roughnesses found in actual gas turbines in service. Flow angle, flow rate, and loss have been measured. For the tested roughnesses of 180, 300, 425, and 850 microns, the axial velocity ratio decreases by 0.1, 2.1, 2.5, and 5.4%, respectively. For the same cases, the deviation increases by 24, 38, 51, and 70%, respectively. Finally, the loss increases by 12, 44, 132, and 217%, respectively. Thus, among the three parameters, the loss responds most sensitively to changes in compressor blade roughness. Furthermore, a new mean-line model based on the assumption of 50% reaction stages has been developed to estimate the effects of roughness on the performance of a multi-stage compressor. The data from the cascade data are used as input to predict the performance of a single compressor stage. Subsequently, a stage-stacking method is used to enable prediction for a multi-stage compressor. According to the model, the pressure ratio, and mass flow rate are significantly influenced by the blade surface roughness.
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Yun, Yong Il, Il Young Park i Seung Jin Song. "Performance Degradation Due to Blade Surface Roughness in a Single-Stage Axial Turbine". W ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-53094.
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Turbine blades experience significant surface degradation with service. Previous studies indicate that an order of magnitude or greater increase in roughness height is typical, and these elevated levels of surface roughness significantly influence turbine efficiency and heat transfer. This paper presents measurement and a mean line analysis of turbine efficiency reduction due to blade surface roughness. Performance tests have been conducted in a low speed, single-stage, axial flow turbine with roughened blades. Sheets of sandpaper with equivalent sandgrain roughnesses of 106 and 400 μm have been used to roughen the blades. The roughness heights correspond to foreign deposits on real turbine blades measured by Bons et al. [1]. In the transitionally rough regime (106 μm), normalized efficiency decreases by approximately 4 percent with either roughened stator or roughened rotor and 8 percent with roughness on both the stator and rotor blades. In the fully rough regime (400 μm), normalized efficiency decreases by 2 percent with roughness on the pressure side and by 6 percent with roughness on the suction side. Also, the normalized efficiency decreases by 11 percent with roughness only on stator vanes; 8 percent with roughness only on rotor blades; and 19 percent with roughness on both the stator and rotor blades.
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Rooij, R. P. J. O. M., i W. A. Timmer. "Roughness Sensitivity Considerations for Thick Rotor Blade Airfoils". W 41st Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2003. http://dx.doi.org/10.2514/6.2003-350.
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van Rooij, R. P. J. O. M., i W. A. Timmer. "Roughness Sensitivity Considerations for Thick Rotor Blade Airfoils". W ASME 2003 Wind Energy Symposium. ASMEDC, 2003. http://dx.doi.org/10.1115/wind2003-350.
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In modern wind turbine blades airfoils of more than 25% thickness can be found at mid-span and inboard locations. In particular at mid-span aerodynamic requirements dominate, demanding a high lift-to-drag ratio, moderate to high lift and low roughness sensitivity. Towards the root srtuctural requirements become more important. In this paper the performance for the airfoil series DU, FFA, S8xx, AH, Riso̸ and NACA are reviewed. For the 25% and 30% thick airfoils the best performing airfoils can be recognized by a restricted upper surface thickness and a S-shaped lower surface for aft-loading. Differences in performance of the DU 91-W2-250 (25%), S814 (24%) and Riso̸-A1-24 (24%) airfoil are small. For a 30% thickness the DU 97-W-300 meets the requirements best. At inboard locations the influence of rotation can be significant and 2d wind tunnel tests do not represent the characteristics well. The RFOIL code is believed to be capable of approximating the rotational effect. In particular the change in lift characteristics in the case of leading edge roughness for the 35% and 40% thick DU airfoils, respectively DU 00-W-350 and DU 00-W–401, is remarkable. Due to the strong reduction of roughness sensitivity the design for inboard airfoils could primarily focus on high lift and structural demands.
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McIlroy, Hugh M., Ralph S. Budwig i Donald M. McEligot. "Scaling of Turbine Blade Roughness for Model Studies". W ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-42167.
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The purpose of this note is to provide an approach to scaling turbine blade roughness so a large-scale experiment will yield useful results despite lack of detailed knowledge about the application. In the process, an apparently new approach for scaling of actual turbine blade roughness on an experimental model of a rough turbine blade is presented. Rough surface data from a first-stage high-pressure turbine rotor, estimates of engine operating conditions representative of high-performance aircraft, and assumed matches of the Reynolds number and acceleration parameter ranges are used. A scaling factor is determined by estimating and matching the nondimensional roughness (in wall coordinates) of a typical airfoil for a model.
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Gregg, Jason R., i Kenneth W. Van Treuren. "Experimental Testing of Periodic Roughness Elements on a Small Scale Wind Turbine Blade". W ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-38863.
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When studied in large wind turbines, roughness on wind turbine blades has been shown to decrease wind turbine performance by up to 50%. However, during wind turbine testing in the Baylor University Subsonic Wind Tunnel, roughness effects that were an artifact of the blade manufacturing process led to a significant power increase over smooth blades at the design wind speed of 10 mph. These results have led to an investigation of the effects of roughness on wind turbine performance under a flow condition with local Reynolds numbers ranging from 14,200 to 58,800. It was found that under these flow conditions the roughness can improve measured power output by up to 126% when compared with a smooth blade. This paper examines the conditions where roughness can positively affect the operation of a wind turbine by testing a 500 mm diameter, horizontal axis, three blade, fixed pitch wind turbine system in a wind tunnel. The experiments have been carried out on a single direct-drive wind turbine model and a single blade design using the NREL designed S818 airfoil. The design point for the blades tested is 10 miles per hour, with a tip speed ratio of 7. Roughness can be an effective treatment when used at or near the stall speed of the wind turbine blade for lower Reynolds number conditions. The roughness elements tested were both perpendicular to and along the flow lines. These blades were then compared to a blade configuration without roughness elements.
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Boynton, J. L., R. Tabibzadeh i S. T. Hudson. "Investigation of Rotor Blade Roughness Effects on Turbine Performance". W ASME 1992 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1992. http://dx.doi.org/10.1115/92-gt-297.
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The cold air test program was completed on the SSME (Space Shuttle Main Engine) HPFTP (High Pressure Fuel Turbopump) turbine with production nozzle vane rings and polished coated rotor blades with a smooth surface finish of 30 microinch (0.76 micrometer) RMS (Root Mean Square). The smooth blades were polished by an abrasive flow machining process. The test results were compared with the air test results from production rough coated rotor blades with a surface finish of up to 400 microinch (10.16 micrometer) RMS. Turbine efficiency was higher for the smooth blades over the entire range tested. Efficiency increased 2.1 percentage points at the SSME 104 percent RPL (Rated Power Level) condition. This efficiency improvement could reduce the SSME HPFTP turbine inlet temperature by 57 degrees Rankine (32 degrees Kelvin) increasing turbine durability. The turbine flow parameter increased and the mid-span outlet swirl angle became more axial with the smooth rotor blades.
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Joseph, Liselle A., Julien Fenouil, Aurelien Borgoltz i William J. Devenport. "Aerodynamic Effects of Roughness on Wind Turbine Blade Sections". W 33rd AIAA Applied Aerodynamics Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2015. http://dx.doi.org/10.2514/6.2015-3384.
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Hamed, Awatef A., Widen Tabakoff, Richard B. Rivir, Kaushik Das i Puneet Arora. "Turbine Blade Surface Deterioration by Erosion". W ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-54328.
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This paper presents the results of a combined experimental and computational research program to investigate turbine vane and blade material surface deterioration caused by solid particle impacts. Tests are conducted in the erosion wind tunnel for coated and uncoated blade materials at various impact conditions. Surface roughness measurements obtained prior and subsequent to the erosion tests are used to characterize the change in roughness caused by erosion. Numerical simulations for the three dimensional flow field and particle trajectories through a low pressure gas turbine are employed to determine the particle impact conditions with stator vanes and rotor blades using experimentally-based particle restitution models. Experimental results are presented for the measured blade material/coating erosion and surface roughness. The measurements indicate that both erosion and surface roughness increase with impact angle and particle size. Computational results are presented for the particle trajectories though the first stage of a low-pressure turbine of a high bypass turbofan engine. The trajectories indicate that the particles impact the vane pressure surface and the aft part of the suction surface. The impacts reduce the particle momentum through the stator but increase it through the rotor. Vane and blade surface erosion patterns are predicted based on the computed trajectories and the experimentally measured blade coating erosion characteristics.
Raporty organizacyjne na temat "BLADE ROUGHNESS"
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Wilcox, Benjamin J., Edward B. White i David Charles Maniaci. Roughness Sensitivity Comparisons of Wind Turbine Blade Sections. Office of Scientific and Technical Information (OSTI), październik 2017. http://dx.doi.org/10.2172/1404826.
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Raben, Sam, Pavlos Vlachos i Wing Ng. Effects of Leading Edge Film-Cooling and Surface Roughness on the Downstream Film-Cooling Along a Transonic Turbine Blade for Low and High Free-Stream Turbulence. Fort Belvoir, VA: Defense Technical Information Center, luty 2008. http://dx.doi.org/10.21236/ada479415.
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