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Journal of Thermal Science 2018年第6期27卷 505-515页

作者： LIU Hanru YUE Shaoyuan WANG Yangang ZHANG Jun School of Power & Energy Northwestern Polyteclmical University Xi'an 710129 China Shaanxi Key Laboratory of Internal Aerodynamics in Acro-Engine Xi'an 710129 China

To investigate the effects of matching characteristics of tandem cascade on the performance and flow at large angle of attack, the unsteady numerical simulation has been implemented. The influences of different turning angle ratio(TR) and chord length ratio(CR) of two blades and the relative angle of attack of rear blade(Delta) are analyzed. The numerical results indicated that the tandem cascade can obtain overall performance improvement including higher static pressure ratio and lower total pressure loss with the matching parameters in the range of TR=3～5, CR=0.5～1.2, and Delta=-15°～-5°. The separation on the front blade has more prominent impact than that on the rear blade, so the performance improvement of tandem cascade is significantly dependent on the reduction of front-blade separation and loss. Regarding the rear blade, the gap injection effect can periodically control the separation. Temporal and spatial analysis of the flow field shows that the optimal-performance cases generally have much smaller wake loss for both two blades, but the unsteady characteristics of the wake loss is more apparent than that of the poor performance cases.

关键词： tandem cascade unsteady simulation matching parameters aerodynamics performance flow loss

Stall Behaviour in a Mixed-flow Compressor with Axial Slot Casing Treatment

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Journal of Thermal Science 2022年第1期31卷 13-24页

作者： QIU Jiahui ZHANG Qianfeng ZHANG Min DU Juan ZHANG Wenqiang MAROLDT Niklas SEUME Joerg R. Advanced Gas Turbine Laboratory Institute of Engineering ThermophysicsChinese Academy of SciencesBeijing 100190China Key Laboratory of Advanced Energy and Power Chinese Academy of SciencesBeijing 100190China Innovation Academy for Light-Duty Gas Turbine Chinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China China Aerodynamics Research and Development Center Beijing 100029China University of Nottingham Nottingham NG72RDEngland Institute of Turbomachinery and Fluid Dynamics Leibniz University HannoverGarbsen 30823Germany

Casing treatment is an effective technique in extending stall margin of axial and centrifugal ***,its impacts on the stall behaviour of mixed-flow compressor are still not completely understood until *** conquer this issue,unsteady full-annulus simulations were conducted to investigate the stall mechanism of a mixed-flow compressor with and without axial slot casing treatment(ASCT).The circumferential propagating speed of spike inception resolved by the numerical approach is 87.1%of the shaft speed,which is identical to the test *** numerical results confirmed that the mixed-flow compressor fell into rotating stall via spike-type with and without *** flow structure of the spike inception was investigated at 50%design rotational *** static pressure traces extracted upstream of the leading edge had shown a classic spiky ***,it was found that with and without ASCT,the mixed-flow compressor stalled through spike with the characteristic of tip leakage spillage at leading edge and tip leakage backflow from trailing edge,which is different from a fraction of the centrifugal *** resultant phenomenon provides conoborating evidence for that unlike in axial-flow compressor,the addition of ASCT does not change the stall characteristics of the mixed-flow *** flow structure that induced spike inception with ASCT is similar to the case with smooth *** the throttling process,tip leakage flow vortex had been involved in the formation of tornado vortices,with one end at the suction side,and the other end at the *** low-pressure region relevant to the downward spike is caused by leading-edge separation vortex or tornado *** high-pressure region relevant to the upward spike is induced by blockage from the passage *** results not only can provide guidance for the design of casing treatment in mixed-flow compressor,but also can pave the way for the stall waring in the highly-l

关键词： mixed-flow compressor casing treatment spike-type stall inception unsteady simulation tornado vortex

Influence of Reynolds Number on the unsteady Aerodynamics of Integrated Aggressive Intermediate Turbine Duct

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Journal of Thermal Science 2018年第3期27卷 294-303页

作者： LIU Hongrui LIU Jun JI Lucheng DU Qiang LIU Guang WANG Pei School of Aerospace Engineering Beijing Institute of Technology Beijing 100081 China Key Laboratory of Light-Duty Gas-Turbine Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190 China University of Chinese Academy of Sciences Beijing 100049 China

The ultra-high bypass ratio turbofan engine attracts more and more attention in modern commercial engine due to advantages of high efficiency and low Specific Fuel Consumption(SFC). One of the characteristics of ultra-high bypass ratio turbofan is the intermediate turbine duct which guides the flow leaving high pressure turbine(HPT) to low pressure turbine(LPT) at a larger diameter, and this kind of design will lead to aggressive intermediate turbine duct(AITD) design concept. Thus, it is important to design the AITD without any severe loss. From the unsteady flow's point of view, in actual operating conditions, the incoming wake generated by HPT is unsteady which will take influence on boundary layer's transition within the ITD and LPT. In this paper, the three-dimensional unsteady aerodynamics of an AITD taken from a real engine is studied. The results of fully unsteady three-dimensional numerical simulations, performed with ANSYS-CFX(RANS simulation with transitional model), are critically evaluated against experimental data. After validation of the numerical model, the physical mechanisms inside the flow channel are analyzed, with an aim to quantify the sensitivities of different Reynolds number effect on both the ITD and LPT nozzle. Some general physical mechanisms can be recognized in the unsteady environment. It is recognized that wake characteristics plays a crucial role on the loss within both the ITD and LPT nozzle section, determining both time-averaged and time-resolved characteristics of the flow field. Meanwhile, particular attention needs to be paid to the unsteady effect on the boundary layer of LPT nozzle's suction side surface.

关键词： Intermediate Turbine Duct unsteady simulation Reynolds Number Flow Field Analysis

The effects of the rotor-stator interaction on unsteady pressure pulsation and radial force in a centrifugal pump

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Journal of Hydrodynamics 2018年第4期30卷 672-681页

作者： Issa Chalghoum Sami Elaoud Hatem Kanfoudi Mohsen Akrout Research Laboratory "Applied Fluid Mechanics Process and Environment Engineering" National Engineering School of Sfax Sfax Tunisia Research Laboratory "Laboratory of Hydraulics and Environment Modeling" National Engineering School of Tunis ENIT Hydraulic Engineering Tunis Tunisia

An unsteady numerical analysis has been conducted to study the strong interaction between impeller blade and volute tongue of a centrifugal pump. The 3-D-URANS equations were solved with the shear stress transport turbulence model for a wide range of flow rates. These unsteady interactions are mostly related to the unsteady radial force due to an imbalance in the pressure field at the impeller periphery. This force represents dynamic load that are one of the most important sources of vibration and hydraulic noise. Based on this phenomenon, this work analyzes and gives a more realistic prediction of the pressure fluctuation and the radial force during steady and unsteady calculation by considering the effect of the change in the pump operating point. Actually, the pressure fluctuations in the impeller and the volute were recorded by mounting nine monitoring points on the impeller and volute casing. The results of the existing analysis has proven that the pressure fluctuation is periodic due to the relative position of impeller blade to volute tongue. The characteristics of the time domain and frequency domain of the pressure pulsation were analyzed under different coupling conditions. Fast Fourier transform was performed to obtain the spectra of pressure pulsation. Besides, the steady and unsteady forces were calculated around the impeller periphery to fully characterize the pump behavior. The obtained pump performance curves were numerically compared with the experimental ones, and the outcome have shown an acceptable agreement between both curves.

关键词： unsteady simulation blade-tongue interaction unsteady pressure distribution blade-passing frequency

Numerical Investigations of the Influence of unsteady Vane Trailing Edge Shock Wave on Film Cooling Effectiveness of Rotor Blade Leading Edge

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Journal of Thermal Science 2018年第2期27卷 135-145页

作者： WANG Yufeng CAI Le WANG Songtao ZHOU Xun Engine Aerodynamics Research Centre Harbin Institute of Technology Harbin 150001 China

unsteady numerical simulations of a high-load transonic turbine stage have been carried out to study the influences of vane trailing edge outer-extending shockwave on rotor blade leading edge film cooling performance. The turbine stage used in this paper is composed of a vane section and a rotor one which are both near the root section of a transonic high-load turbine stage. The Mach number is 0.94 at vane outlet, and the relative Mach number is above 1.10 at rotor outlet. Various positions and oblique angles of film cooling holes were investigated in this research. Results show that the cooling efficiency on the blade surface of rotor near leading edge is significantly affected by vane trailing edge outer-extending shockwave in some cases. In the cases that film holes are close to leading edge, cooling performance suffers more from the sweeping vane trailing edge outer-extending *** addition, coolant flow ejected from oblique film holes is harder to separate from the blade surface of rotor, and can cover more blade area even under the effects of sweeping vane trailing edge shockwave. As a result, oblique film holes can provide better film cooling performance than vertical film holes do near the leading edge on turbine blade which is swept by shockwaves.

关键词： transonic turbine trailing edge shock wave ftlm cooling unsteady simulation