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| 1 | Reduced order model for unsteady aerodynamic performance of compressor cascade based on recursive RBF显示文摘Based on Recursive Radial Basis Function(RRBF)neural network,the Reduced Order Model(ROM)of compressor cascade was established to meet the urgent demand of highly efficient prediction of unsteady aerodynamics performance of turbomachinery.One novel ROM called ASA-RRBF model based on Adaptive Simulated Annealing(ASA)algorithm was developed to enhance the generalization ability of the unsteady ROM.The ROM was verified by predicting the unsteady aerodynamics performance of a highly-loaded compressor cascade.The results show that the RRBF model has higher accuracy in identification of the dimensionless total pressure and dimensionless static pressure of compressor cascade under nonlinear and unsteady conditions,and the model behaves higher stability and computational efficiency.However,for the strong nonlinear characteristics of aerodynamic parameters,the RRBF model presents lower accuracy.Additionally,the RRBF model predicts with a large error in the identification of aerodynamic parameters under linear and unsteady conditions.For ASA-RRBF,by introducing a small-amplitude and highfrequency sinusoidal signal as validation sample,the width of the basis function of the RRBF model is optimized to improve the generalization ability of the ROM under linear unsteady conditions.Besides,this model improves the predicting accuracy of dimensionless static pressure which has strong nonlinear characteristics.The ASA-RRBF model has higher prediction accuracy than RRBF model without significantly increasing the total time consumption.This novel model can predict the linear hysteresis of dimensionless static pressure happened in the harmonic condition,but it cannot accurately predict the beat frequency of dimensionless total pressure. | Jiawei HU Hanru LIU Yan'gang WANG Weixiong CHEN Yan MA | 2021 | Chinese Journal of Aeronautics2021，34，4： | 7 |
| 2 | Unsteady Study on the Effects of Matching Characteristic of Tandem Cascade on the Performance and Flow at Large Angle of Attack显示文摘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. | LIU Hanru YUE Shaoyuan WANG Yangang ZHANG Jun | 2018 | Journal of Thermal Science2018，27，6： | 5 |
| 3 | Modification of Flow Structure and Sound Source by Hybrid Porous-serrated Trailing Edge显示文摘The effects of hybrid porous-serrated trailing edge on flow structure and sound source of NACA65(12)-10 at moderate Reynolds number(Rec=5×1O^5)have been investigated by Delayed Detached Eddy Simulation(DDES).Compared with conventional serrated trailing edge,the pressure fluctuation in the vicinity of hybrid porous-serrated trailing edge is further decreased significantly.The typical necklace vortex structures stretching across adjacent serrations are suppressed by the porous additive.It is found that porous media changes the shear stress distribution along the serration edge and inside the serration gap,which consequently eliminates the generation of necklace vortex.Therefore,the deformation of vortex tube caused by velocity vector is weakened.The underlying mechanisms associated to the sound source modification are analyzed based on vortex sound theory.The magnitude of Lamb vector and the angle between vorticity and velocity vectors are synchronously reduced by the porous additive,which implies that the present hybrid porous-serrated trailing edge has important influence on the further attenuation of far-field aerodynamic noise. | Hanru Liu Nanshu Chen Yangang Wang Zhijie Hu | 2020 | Journal of Bionic Engineering2020，17，3： | 1 |
| 4 | Multi-scale nature of non-blade-order propagating flow disturbances in axial compressors显示文摘Non-blade-order flow disturbances, also referred to as pre-stall disturbances or tip flow unsteadiness, are closely related with compressor instabilities. The present work provides a comprehensive investigation on multi-scale nature of non-blade-order disturbances and the underlying flow physics in axial compressors. By applying full-annulus Unsteady Reynolds-Averaged Navier-Stokes(URANS) simulations, along with space–time correlation and spatial Fourier decomposition, to the disturbed pressure, the propagating feature of the non-blade-order disturbances is obtained. Further, a bridge between non-blade-order disturbances and the evolution of unsteady vortex has been set up. The results show that non-blade-order disturbances, featured as short-length-scale(35 modes across annulus), first appear as the occurrence of tip leakage vortex fluctuation, while the compressor still operates far from stall. Leading-edge radial vortex appears at near stall condition, and its movement induces a circumferential propagating disturbance overlaying on the one induced by oscillating tip leakage vortex. The interaction of the short-scale disturbances with a lowamplitude long-scale(of circumference) disturbance is observed, which results in disturbances with multiple scales of consecutive spatial modes, along with multiple frequency peaks in spectra. The compressor falls into stall as the circumferential nonuniform scattering of the leading-edge vortexes occurs. The densely-and sparsely-scattered leading-edge radial vortexes induce a high-amplitude long-scale(of circumference) disturbance , i.e. stall disturbance. | Hao WANG Yan’gang WANG Hanru LIU Fei XUE Zhongnan WANG | 2022 | Chinese Journal of Aeronautics2022，35，9： | 0 |
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