D. Liu, X. Miao, Z. Zhang, J. Yang, T. Yuan, R. Song
The interior noise caused by the pantograph area is greater than that caused by other areas, and the impact of this pantograph area becomes more significant as the speed of high-speed trains increases, especially above 350 km/h. This study proposes an active jet method for pantograph cavities to control noise at the source. First, a predictive model for the interior noise of pantograph carriages was established by jointly adopting large eddy simulation–statistical energy analysis methods. Then, numerical simulations were conducted to determine the external noise sources and interior sound pressure level at different speeds (300, 350, 400, and 450 km/h). Finally, active jets at different speeds (97.2, 111.1, 125, and 140 m/s) were used to analyze the reduction in interior noise. Results showed that the active jet method decreased the average overall sound pressure level of the acoustic cavity in the horizontal plane. When the train speed reached 450 km/h, the optimal reduction in interior noise was approximately 7.5 dB in the horizontal plane for both the standing and sitting postures. The proposed method can efficiently reduce interior noise in the pantograph area.
{"title":"Interior Noise Reduction Method of Pantograph Areas for High-speed Trains Based on Active Jet Technology","authors":"D. Liu, X. Miao, Z. Zhang, J. Yang, T. Yuan, R. Song","doi":"10.47176/jafm.17.7.2472","DOIUrl":"https://doi.org/10.47176/jafm.17.7.2472","url":null,"abstract":"The interior noise caused by the pantograph area is greater than that caused by other areas, and the impact of this pantograph area becomes more significant as the speed of high-speed trains increases, especially above 350 km/h. This study proposes an active jet method for pantograph cavities to control noise at the source. First, a predictive model for the interior noise of pantograph carriages was established by jointly adopting large eddy simulation–statistical energy analysis methods. Then, numerical simulations were conducted to determine the external noise sources and interior sound pressure level at different speeds (300, 350, 400, and 450 km/h). Finally, active jets at different speeds (97.2, 111.1, 125, and 140 m/s) were used to analyze the reduction in interior noise. Results showed that the active jet method decreased the average overall sound pressure level of the acoustic cavity in the horizontal plane. When the train speed reached 450 km/h, the optimal reduction in interior noise was approximately 7.5 dB in the horizontal plane for both the standing and sitting postures. The proposed method can efficiently reduce interior noise in the pantograph area.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141694953","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Huang, B. D. Zhang, †. Z.W.Li, J. P. Zhao, W. J. Peng, J. R. Lin
The pantograph is a critical instrument that significantly affects the aerodynamics of high-speed trains, posing a considerable challenge to the energy conservation and environmental protection of trains. This study explores the feasibility and efficiency of a jet-flow control technique in optimising the aerodynamic characteristics of the pantograph. A numerical method was adopted to investigate the effects of various jet-flow parameters, such as the jet positions, velocities and jet-slot widths, on the flow changes around the pantograph and subsequent reduction in aerodynamic drag of the pantograph. The results show that the impact of the jet position is negligible when the jet velocity is lower than the train speed. The aerodynamic drag reduction rate decreased with increasing distance from the pantograph as the jet velocity increased. When the distance between the jet slot and pantograph is less than 0.6 times the height of the pantograph, the aerodynamic drag reduction rate continuously increased with the jet velocity. As the jet slot moved away from the pantograph, the aerodynamic drag reduction rate initially increased rapidly with the jet velocity and then gradually decreased when the velocity surpassed 1.2 times the train speed. In addition, the aerodynamic drag of the pantograph decreased as the width of the jet slot decreased. However, the energy of the whole train can be only saved when the jet velocity is below 0.6 times the train speed. Findings in this study verified the effectiveness of the jet-flow method in reducing the aerodynamic drag of pantographs and
{"title":"Aerodynamic Characteristics of High-speed Train Pantographs Based on Jet Flow Control","authors":"S. Huang, B. D. Zhang, †. Z.W.Li, J. P. Zhao, W. J. Peng, J. R. Lin","doi":"10.47176/jafm.17.7.2316","DOIUrl":"https://doi.org/10.47176/jafm.17.7.2316","url":null,"abstract":"The pantograph is a critical instrument that significantly affects the aerodynamics of high-speed trains, posing a considerable challenge to the energy conservation and environmental protection of trains. This study explores the feasibility and efficiency of a jet-flow control technique in optimising the aerodynamic characteristics of the pantograph. A numerical method was adopted to investigate the effects of various jet-flow parameters, such as the jet positions, velocities and jet-slot widths, on the flow changes around the pantograph and subsequent reduction in aerodynamic drag of the pantograph. The results show that the impact of the jet position is negligible when the jet velocity is lower than the train speed. The aerodynamic drag reduction rate decreased with increasing distance from the pantograph as the jet velocity increased. When the distance between the jet slot and pantograph is less than 0.6 times the height of the pantograph, the aerodynamic drag reduction rate continuously increased with the jet velocity. As the jet slot moved away from the pantograph, the aerodynamic drag reduction rate initially increased rapidly with the jet velocity and then gradually decreased when the velocity surpassed 1.2 times the train speed. In addition, the aerodynamic drag of the pantograph decreased as the width of the jet slot decreased. However, the energy of the whole train can be only saved when the jet velocity is below 0.6 times the train speed. Findings in this study verified the effectiveness of the jet-flow method in reducing the aerodynamic drag of pantographs and","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141704733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Today, due to advances in computing power, Reynolds Averaged Navier-Stokes (RANS) solvers are widely preferred for quasi-three-dimensional (Q3D) blade-to-blade analysis. This study investigates the performance of different flux calculation methods and turbulence models with a density-based RANS solver (Numeca®) in blade-to-blade analysis. A block-structured mesh topology is used to create a solution grid around the airfoil. Spatial discretization is performed in the pitchwise direction to represent the quasi three-dimensional flow, while only one computational cell is used in the radial direction to simulate the flow through the Q3D cascade. The computational grid around the airfoil is created with the Autogrid® tool using the block mesh topology. For the convective flow calculations, both the central and upwind methods available in Numeca® are applied separately. The Baldwin Lomax (BL), Spalart Allmaras (SA), Shear Stress Transport (SST), Explicit Algebraic Reynolds Stress Model (EARSM) and k-ε (KEPS) turbulence models are used for the turbulent shear stress calculations. In order to evaluate the aerodynamic performance of the spatial discretization methods and turbulence models, the isentropic Mach distribution on the airfoil surface, the total pressure loss and the exit flow angle behind the blade are compared with the experimental data of six test cases. In the compressor cases
{"title":"Assessment of Effect of Flux Scheme and Turbulence Model on Blade-to-blade Calculations","authors":"M. Bilgiç, Ö. U. Baran, M. Aksel","doi":"10.47176/jafm.17.7.2234","DOIUrl":"https://doi.org/10.47176/jafm.17.7.2234","url":null,"abstract":"Today, due to advances in computing power, Reynolds Averaged Navier-Stokes (RANS) solvers are widely preferred for quasi-three-dimensional (Q3D) blade-to-blade analysis. This study investigates the performance of different flux calculation methods and turbulence models with a density-based RANS solver (Numeca®) in blade-to-blade analysis. A block-structured mesh topology is used to create a solution grid around the airfoil. Spatial discretization is performed in the pitchwise direction to represent the quasi three-dimensional flow, while only one computational cell is used in the radial direction to simulate the flow through the Q3D cascade. The computational grid around the airfoil is created with the Autogrid® tool using the block mesh topology. For the convective flow calculations, both the central and upwind methods available in Numeca® are applied separately. The Baldwin Lomax (BL), Spalart Allmaras (SA), Shear Stress Transport (SST), Explicit Algebraic Reynolds Stress Model (EARSM) and k-ε (KEPS) turbulence models are used for the turbulent shear stress calculations. In order to evaluate the aerodynamic performance of the spatial discretization methods and turbulence models, the isentropic Mach distribution on the airfoil surface, the total pressure loss and the exit flow angle behind the blade are compared with the experimental data of six test cases. In the compressor cases","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141710563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Zhou, S. Y. Zhao, S. J. Zhang, Y. Zhang, S. C. Fu, S. Q. Yu
This paper presents a comprehensive investigation of flow-induced noise characteristics in ethylene cracking furnace tubes, covering both pre-and post-coking conditions. Large-eddy simulation (LES) was employed in conjunction with a generalized Lighthill’s acoustic analogy model. The results indicate that noise sources can be classified as dipole acoustic sources, with energy primarily concentrated ranged from 300 to 1500 Hz, in comparison to standard conditions. The primary location of the acoustic source was identified in the region commonly referred to as the “necking” of the furnace tube, demonstrating a strong correlation with turbulence intensity near the tube wall. As the coke layer thickness in the furnace tube increased from 5 mm to 15 mm, both the sound power level and turbulence intensity exhibited significant growth. Specifically, the sound power level increased by 60.5% while the turbulence intensity increased by 58.5%. Variations in the overall sound pressure level (OASPL) curve measured within the tube could be utilized to assess coking levels. Significant peaks in the OASPL curve were observed as the furnace tube underwent substantial coking, with coke layer thicknesses of 10 mm and 15 mm.
{"title":"Analysis of Flow-induced Noise Characteristics of Ethylene Cracking Furnace Tubes before and after Coking","authors":"F. Zhou, S. Y. Zhao, S. J. Zhang, Y. Zhang, S. C. Fu, S. Q. Yu","doi":"10.47176/jafm.17.7.2424","DOIUrl":"https://doi.org/10.47176/jafm.17.7.2424","url":null,"abstract":"This paper presents a comprehensive investigation of flow-induced noise characteristics in ethylene cracking furnace tubes, covering both pre-and post-coking conditions. Large-eddy simulation (LES) was employed in conjunction with a generalized Lighthill’s acoustic analogy model. The results indicate that noise sources can be classified as dipole acoustic sources, with energy primarily concentrated ranged from 300 to 1500 Hz, in comparison to standard conditions. The primary location of the acoustic source was identified in the region commonly referred to as the “necking” of the furnace tube, demonstrating a strong correlation with turbulence intensity near the tube wall. As the coke layer thickness in the furnace tube increased from 5 mm to 15 mm, both the sound power level and turbulence intensity exhibited significant growth. Specifically, the sound power level increased by 60.5% while the turbulence intensity increased by 58.5%. Variations in the overall sound pressure level (OASPL) curve measured within the tube could be utilized to assess coking levels. Significant peaks in the OASPL curve were observed as the furnace tube underwent substantial coking, with coke layer thicknesses of 10 mm and 15 mm.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141715743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
With regard to the pronounced pressure pulsation and cyclic thrust oscillation observed in the tail flow field of an underwater vehicle operating under over-expanded conditions, and drawing inspiration from flow control techniques involving porous media structures like submarine coral reefs and breakwaters, this paper presents an innovative proposition to incorporate a porous media layer on the tail wall of the nozzle in order to regulate the structure of the tail gaseous jets. To optimize the flow control of underwater vehicles, the utilization of porous media layers with varying degrees of porosity is employed to establish a model for underwater supersonic gaseous jets. This model scrutinizes the intricate structure of the tail gaseous jets, as well as the consequential wall pressure and thrust engendered by the nozzle. The findings eloquently demonstrate that the porous media model, boasting a porosity of 0.34, exerts a diminished influence on the morphological characteristics of the tail gaseous jets, while concurrently yielding a superior flow control effect on the pulsation of tail wall pressure and attenuating the differential thrust generated by the underwater vehicle. Consequently, this innovative approach effectively mitigates overall thrust oscillation, thereby enhancing the stability of the underwater vehicle throughout its submerged operations.
{"title":"Numerical Simulation of Underwater Supersonic Gaseous Jets of Underwater Vehicle with Porous Media Layer","authors":"Y. Shen, J. Luo, B. Yang, J. Xia, Y. Wang, S. Li","doi":"10.47176/jafm.17.6.2155","DOIUrl":"https://doi.org/10.47176/jafm.17.6.2155","url":null,"abstract":"With regard to the pronounced pressure pulsation and cyclic thrust oscillation observed in the tail flow field of an underwater vehicle operating under over-expanded conditions, and drawing inspiration from flow control techniques involving porous media structures like submarine coral reefs and breakwaters, this paper presents an innovative proposition to incorporate a porous media layer on the tail wall of the nozzle in order to regulate the structure of the tail gaseous jets. To optimize the flow control of underwater vehicles, the utilization of porous media layers with varying degrees of porosity is employed to establish a model for underwater supersonic gaseous jets. This model scrutinizes the intricate structure of the tail gaseous jets, as well as the consequential wall pressure and thrust engendered by the nozzle. The findings eloquently demonstrate that the porous media model, boasting a porosity of 0.34, exerts a diminished influence on the morphological characteristics of the tail gaseous jets, while concurrently yielding a superior flow control effect on the pulsation of tail wall pressure and attenuating the differential thrust generated by the underwater vehicle. Consequently, this innovative approach effectively mitigates overall thrust oscillation, thereby enhancing the stability of the underwater vehicle throughout its submerged operations.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141232591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Traveling wave is an innovative active flow control technique that can remarkably mitigate flow separation. This paper employs numerical simulation to examine how traveling wave structures affect the NACA0012 airfoil. The traveling wave structure is situated at 0.5% c from the leading edge. In the chord direction, its projection length is 0.1 c . Through numerical simulation, the impacts of dimensionless length-width ratio and velocity of traveling wave on flow separation are investigated, and the relationship between the traveling wave's optimal parameters and angle of attack is explored. The outcomes demonstrate that traveling waves with suitable length-width ratios and velocities can effectively suppress flow separation. When AoA =16°, traveling wave airfoil with dimensionless velocity U =1.1 and length-width ratio A =1 achieves the best performance, and its lift-drag ratio is 9.24 times that of the original NACA0012 airfoil. The optimal dimensionless length-width ratio and velocity of the traveling wave airfoil are associated with the angle of attack, and different parameters need to be chosen at various angles of attack to attain optimum effect.
行波是一种创新的主动气流控制技术，可以显著缓解气流分离。本文通过数值模拟来研究行波结构如何影响 NACA0012 机翼。行波结构位于前缘 0.5% c 处。在弦向，其投影长度为 0.1 c。通过数值模拟，研究了无量纲长宽比和行波速度对气流分离的影响，并探讨了行波最佳参数与攻角之间的关系。结果表明，具有合适长宽比和速度的行波能有效抑制流体分离。当攻角 =16° 时，无量纲速度 U =1.1、长宽比 A =1 的行波翼面性能最佳，其升阻比是原始 NACA0012 翼面的 9.24 倍。行波翼面的最佳无量纲长宽比和速度与攻角有关，在不同的攻角下需要选择不同的参数才能达到最佳效果。
{"title":"Research on Active Flow Control Method of NACA0012 Airfoil with Traveling Wave Structure","authors":"Q. Dai, E. Qi, S. Huang, Z. Zhou, Y. Wang","doi":"10.47176/jafm.17.6.2301","DOIUrl":"https://doi.org/10.47176/jafm.17.6.2301","url":null,"abstract":"Traveling wave is an innovative active flow control technique that can remarkably mitigate flow separation. This paper employs numerical simulation to examine how traveling wave structures affect the NACA0012 airfoil. The traveling wave structure is situated at 0.5% c from the leading edge. In the chord direction, its projection length is 0.1 c . Through numerical simulation, the impacts of dimensionless length-width ratio and velocity of traveling wave on flow separation are investigated, and the relationship between the traveling wave's optimal parameters and angle of attack is explored. The outcomes demonstrate that traveling waves with suitable length-width ratios and velocities can effectively suppress flow separation. When AoA =16°, traveling wave airfoil with dimensionless velocity U =1.1 and length-width ratio A =1 achieves the best performance, and its lift-drag ratio is 9.24 times that of the original NACA0012 airfoil. The optimal dimensionless length-width ratio and velocity of the traveling wave airfoil are associated with the angle of attack, and different parameters need to be chosen at various angles of attack to attain optimum effect.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141234002","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To enhance the aerodynamic performance of an ultra-compact S-shaped convergent-divergent nozzle and mitigate flow separation, numerical simulations were conducted using FLUENT software. The study employed the k-ω shear stress transport turbulent model to investigate a flow control method involving blowing. Detailed analysis was performed on the impact of blowing position, angle, and pressure ratio on controlling flow separation. The findings indicate that as the blowing position moves backward, the flow separation area diminishes. Additionally, downstream flow separation ceases at smaller blowing angles within the separation zone. However, excessively large blowing angles tend to create an “aerodynamic wall,” causing significant upstream flow loss and nozzle performance degradation. Enhancing the blowing pressure ratio, given proper mixing with low-energy fluid and no interference with the main flow, can improve the nozzle's aerodynamic performance. Under the optimal blowing scheme, the total pressure recovery coefficient and thrust coefficient are increased by approximately 0.52% and 3.75%, respectively, when compared with those of the reference nozzle.
{"title":"Flow Separation Control of an Ultra-compact S-shaped Convergent-divergent Nozzle Using the Blowing Method","authors":"J. W. Shi, †. Z.H.Hui, L. Zhou, Z. Wang","doi":"10.47176/jafm.17.6.2398","DOIUrl":"https://doi.org/10.47176/jafm.17.6.2398","url":null,"abstract":"To enhance the aerodynamic performance of an ultra-compact S-shaped convergent-divergent nozzle and mitigate flow separation, numerical simulations were conducted using FLUENT software. The study employed the k-ω shear stress transport turbulent model to investigate a flow control method involving blowing. Detailed analysis was performed on the impact of blowing position, angle, and pressure ratio on controlling flow separation. The findings indicate that as the blowing position moves backward, the flow separation area diminishes. Additionally, downstream flow separation ceases at smaller blowing angles within the separation zone. However, excessively large blowing angles tend to create an “aerodynamic wall,” causing significant upstream flow loss and nozzle performance degradation. Enhancing the blowing pressure ratio, given proper mixing with low-energy fluid and no interference with the main flow, can improve the nozzle's aerodynamic performance. Under the optimal blowing scheme, the total pressure recovery coefficient and thrust coefficient are increased by approximately 0.52% and 3.75%, respectively, when compared with those of the reference nozzle.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141229813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Film cooling protects high-temperature components and generates complex vortex structures through the interaction between the mainstream flow and the injected coolant. Additionally, the process of applying thermal barrier coatings introduces imperfect cooling holes. A numerical simulation study is conducted on two geometric configurations: inclined perfect and imperfect holes arranged in a single row on a flat plate to investigate the effects of flow field vortex structures and hole imperfections. The k-epsilon turbulent model is employed to analyse the impact of varying blowing ratios and defect positions on flow field structure and cooling efficiency, with vortex dynamics providing explanatory insights. As the blowing ratio increases, the kidney vortex associated with the perfect holes progressively detaches from the wall, reducing film cooling efficiency. The kidney vortex originates from the shear interaction between the mainstream and the impinging jet, predominantly influenced by the vortex stretching component. Imperfect holes influence the distribution state of the kidney vortex, with weakened roll-up phenomena observed at the IT4 defect location. Consequently, a noticeable enhancement in film cooling effectiveness is achieved near the proximal end of the hole.
{"title":"Numerical Analysis of Film Cooling Flow Dynamics and Thermodynamics for Perfect and Imperfect Cooling Holes","authors":"S. Liang, †. R.L.Dong, W. W. Xu, Y. Q. Wei","doi":"10.47176/jafm.17.6.2251","DOIUrl":"https://doi.org/10.47176/jafm.17.6.2251","url":null,"abstract":"Film cooling protects high-temperature components and generates complex vortex structures through the interaction between the mainstream flow and the injected coolant. Additionally, the process of applying thermal barrier coatings introduces imperfect cooling holes. A numerical simulation study is conducted on two geometric configurations: inclined perfect and imperfect holes arranged in a single row on a flat plate to investigate the effects of flow field vortex structures and hole imperfections. The k-epsilon turbulent model is employed to analyse the impact of varying blowing ratios and defect positions on flow field structure and cooling efficiency, with vortex dynamics providing explanatory insights. As the blowing ratio increases, the kidney vortex associated with the perfect holes progressively detaches from the wall, reducing film cooling efficiency. The kidney vortex originates from the shear interaction between the mainstream and the impinging jet, predominantly influenced by the vortex stretching component. Imperfect holes influence the distribution state of the kidney vortex, with weakened roll-up phenomena observed at the IT4 defect location. Consequently, a noticeable enhancement in film cooling effectiveness is achieved near the proximal end of the hole.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141235227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
†. E.Zhou, P. Lei, C. Fan, W. Zhang, K. Liu, S. Cheng
The Reynolds number ( R e) is an important parameter that can affect compressor performance. This study experimentally and numerically investigated the effect of R e variations on the efficiency and stall mechanisms for a three-stage axial flow compressor. In the experiment, the total pressure ratio, polytropic efficiency, and stalling mass flow rate were measured in a R e range varying from 1,100,000 to 55,000 to elucidate the R e effects. Unsteady three-dimensional numerical simulations were implemented to understand the stall mechanisms. The results indicate that the compressor efficiency and stall– pressure ratio begin to decrease remarkably as R e is reduced below a critical value, which is 220,000 in the case of the compressor studied. At a low R e, losses caused by the secondary flow near the hub and shroud increase remarkably, and the extended boundary layer separations at the blade suction surface further decrease the efficiency. The variation in R e changes the stall-initiated location. At higher Reynolds numbers, the interaction between the corner separation at the hub of stator 1 and the leakage flow through the blade tip gap induces a large vortex, which seriously blocks the blade passage. The blocking effect spreads to the aft stage and extends to higher spans, which results in the stall of the whole compressor. However, the blocking effect at the hub disappears at R e =55,000, and the interaction of the blade boundary layer separation near the shroud of rotor 1 and the tip leakage vortex causes a large blockage and then induces stall. The R e variation
雷诺数（R e）是影响压缩机性能的一个重要参数。本研究通过实验和数值方法研究了 R e 变化对三级轴流压缩机效率和失速机制的影响。在实验中，测量了 R e 在 1,100,000 至 55,000 范围内的总压比、多效效率和失速质量流量，以阐明 R e 的影响。为了解失速机制，还进行了非稳态三维数值模拟。结果表明，当 R e 降低到临界值以下时，压缩机的效率和失速压力比开始显著下降。在 R e 较低时，轮毂和护罩附近的二次流造成的损失显著增加，而叶片吸气面上扩展的边界层分离进一步降低了效率。R e 的变化会改变失速的起始位置。在较高的雷诺数下，定子 1 轮毂处的角分离与通过叶片尖端间隙的泄漏流之间的相互作用会诱发大涡流，严重阻塞叶片通道。阻塞效应扩散到尾级，并延伸到更高的跨度，从而导致整个压缩机失速。然而，在 R e =55,000 时，轮毂处的阻塞效应消失，转子 1 护罩附近的叶片边界层分离与叶尖泄漏涡流的相互作用导致了大面积阻塞，进而引发失速。R e 的变化
{"title":"Effects of the Reynolds Number on the Efficiency and Stall Mechanisms in a Three-stage Axial Compressor","authors":"†. E.Zhou, P. Lei, C. Fan, W. Zhang, K. Liu, S. Cheng","doi":"10.47176/jafm.17.6.2309","DOIUrl":"https://doi.org/10.47176/jafm.17.6.2309","url":null,"abstract":"The Reynolds number ( R e) is an important parameter that can affect compressor performance. This study experimentally and numerically investigated the effect of R e variations on the efficiency and stall mechanisms for a three-stage axial flow compressor. In the experiment, the total pressure ratio, polytropic efficiency, and stalling mass flow rate were measured in a R e range varying from 1,100,000 to 55,000 to elucidate the R e effects. Unsteady three-dimensional numerical simulations were implemented to understand the stall mechanisms. The results indicate that the compressor efficiency and stall– pressure ratio begin to decrease remarkably as R e is reduced below a critical value, which is 220,000 in the case of the compressor studied. At a low R e, losses caused by the secondary flow near the hub and shroud increase remarkably, and the extended boundary layer separations at the blade suction surface further decrease the efficiency. The variation in R e changes the stall-initiated location. At higher Reynolds numbers, the interaction between the corner separation at the hub of stator 1 and the leakage flow through the blade tip gap induces a large vortex, which seriously blocks the blade passage. The blocking effect spreads to the aft stage and extends to higher spans, which results in the stall of the whole compressor. However, the blocking effect at the hub disappears at R e =55,000, and the interaction of the blade boundary layer separation near the shroud of rotor 1 and the tip leakage vortex causes a large blockage and then induces stall. The R e variation","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141235377","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Present research study analyses the suitability of baffled reactor vessels with large diameter agitated using the Rushton Turbine (RT) impeller maintained at standard clearance condition for the solid-liquid suspension process. The mean and turbulent flow fields associated with reactor vessels of various diameter were simulated using Computational Fluid Dynamics (CFD) approach. The impeller rotation was modelled using Multiple Reference Frame (MRF) technique and entrainment of air was simulated using Volume of Fluid (VOF) method respectively. The increase in the diameter of reactor vessel keeping impeller at standard clearance condition lead to the transition from double to single loop pattern with considerable decrease in the power number. In large reactor vessels, a low pressure zone is developed below the impeller which deflects the discharge streams and trailing vortices towards bottom surface of the reactor vessel causing the formation of single loop down-pumping pattern. The downward propagation of trailing vortices weaken the flow separation region behind the impeller blades which in turn decreases the form drag and power number of the impeller. The development of single loop down-pumping pattern, high magnitudes of axial velocity, vortex and turbulence fields near vessel bottom and inferior entrainment of air makes the large reactor vessels suitable for the solid-liquid suspension process. The high magnitudes of axial velocity developed below the impeller of large reactor vessel with same power consumption as compared to low clearance vessel makes the former vessel configuration more suitable for the solid-liquid suspension process.
{"title":"Effect of Tank Diameter on Solid Suspension in Industrial Reactor Vessels","authors":"D. K. Iyer, †. A.K.Patel","doi":"10.47176/jafm.17.6.2273","DOIUrl":"https://doi.org/10.47176/jafm.17.6.2273","url":null,"abstract":"Present research study analyses the suitability of baffled reactor vessels with large diameter agitated using the Rushton Turbine (RT) impeller maintained at standard clearance condition for the solid-liquid suspension process. The mean and turbulent flow fields associated with reactor vessels of various diameter were simulated using Computational Fluid Dynamics (CFD) approach. The impeller rotation was modelled using Multiple Reference Frame (MRF) technique and entrainment of air was simulated using Volume of Fluid (VOF) method respectively. The increase in the diameter of reactor vessel keeping impeller at standard clearance condition lead to the transition from double to single loop pattern with considerable decrease in the power number. In large reactor vessels, a low pressure zone is developed below the impeller which deflects the discharge streams and trailing vortices towards bottom surface of the reactor vessel causing the formation of single loop down-pumping pattern. The downward propagation of trailing vortices weaken the flow separation region behind the impeller blades which in turn decreases the form drag and power number of the impeller. The development of single loop down-pumping pattern, high magnitudes of axial velocity, vortex and turbulence fields near vessel bottom and inferior entrainment of air makes the large reactor vessels suitable for the solid-liquid suspension process. The high magnitudes of axial velocity developed below the impeller of large reactor vessel with same power consumption as compared to low clearance vessel makes the former vessel configuration more suitable for the solid-liquid suspension process.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141232255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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