Investigation On Optimization Design Of Compressor Tandem Blade And Flow Control Mechanism Combined With Endwall Suction

Aero-engine is the "heart" of aircraft,compressor is the core component of aero-engine,compressor performance has a decisive effect on the thrust-to-weight ratio and fuel consumption rate of aero-engine.With the continuous development of aero-engine,compressor is required to have the characteristics of high load,high efficiency and wide stability margin.However,the raise of load will significantly increase the flow loss of compressor and affect the efficiency and stability margin of compressor.Therefore,with the raise of compressor load,it is of great significance to use flow control technology to eliminate or weaken the flow loss of compressor to improve the performance of engine compression system.In this paper,an in-depth research on tandem blade technology,a common flow control technology in compressors,is carried out.At the same time,in order to solve the complex flow structure of the corner separation and the tip leakage loss in tandem blade,the tandem blade technology was combined with the endwall suction technology,and the control strategies and relavent mechanisms about the endwall suction technology in controlling the phenomena of corner separation and tip leakage flow in tandem blade is studied in detail.In order to improve the design quality of high-load tandem blades,this paper studies the coupling optimization design method of tandem blade configuration parameters and airfoil shape.Aiming at the characteristics of tandem blades with more configuration parameters and airfoil control parameters,this article established a new intelligent optimization system for compressor tandem blades,which is mainly composed of modified particle swarm algorithm and Kriging hybrid parallel multi-point sampling strategy.In order to improve the defect that the particle swarm optimization algorithm may fall into the local optimal solution,a modified particle swarm algorithm is firstly proposed based on the adaptive selection method of particle roles and the strategy of population diversity control.The main idea of the modified algorithm is to assign different roles to particles at different positions and different fitness levels.At the same time,according to the evolutionary state of the optimization algorithm,some particles are controlled to learn from other excellent particles,and the diversity of particle swarm optimization is increased.In order to solve the problem of single sample structure and sample repetition in the parallel multipoint sampling criterion of Kriging,a hybrid parallel multipoint sampling strategy for Kriging is proposed for the first time in this paper.Its main idea is to use multiple sampling criteria to obtain multiple sample points in parallel multipoint sampling,so the hybrid parallel multi-sampling strategy has the advantages of multiple sampling criteria at the same time.The optimization algorithm test functions and CFD optimization examples are used to study the optimization ability of the modified algorithm.The results prove that the convergence speed of the modified algorithm has obvious advantages over other improved algorithms on the basis of ensuring the convergence accuracy and robustness of the algorithm.The intelligent optimization system is used to accomplish the coupling optimization design about the configuration parameters and the airfoil shape of a high-load tandem blade and a supersonic tandem rotor.At inlet Mach number of 0.7,when incidence angle is-5° and 5°,the total pressure loss coefficient of the optimized tandem blade is respectively decreased by 21%and 35%,which significantly improved the performance of the initial tandem blade at all incidence angle.The isentropic efficiency and surge margin of the optimized supersonic tandem rotor is respectively increased by 1.6% and 2.75%.This paper systematically studies the influence of endwall suction on the secondary flow and corner separation of tandem blades.The study found that the streamwise long slot near the suction surface of the blade can effectively reduce the angular separation of the suction surface,and the streamwise long slot suction scheme in the cascade passage is more helpful to reduce the influence range of the passage vortex.In the studies of the streamwise short slot suction scheme on the endwall,the short slot suction scheme at the trailing edge of the front blade and the leading edge of the rear blade has better control effect.The axial position change of the circumferential long slot on the endwall of front blade has a small effect on the total pressure loss in the endwall region,and the axial position change of the circumferential long slot on the endwall of rear blade has a significant effect on the total pressure loss coefficient in the endwall region.The circumferential position change of the circumferential short slot on the endwall of front blade has a particularly significant effect on the suction result,while the circumferential position change of the circumferential short slot in the endwall of rear blade has a small influence on the suction effect.The circumferential short slot suction scheme near the suction surface on the endwall of front and rear blade provides the best control effect.When the suction intensity of the streamwise or circumferential short slot and long slot is the same,the suction effect of the short slot is poor.However,the control effect of the short slot combination suction scheme on the endwall of the front and rear blade is superior to the streamwise and circumferential long slot suction schemes.This article also deeply analyzes the influence laws of endwall suction schemes on the tip leakage flow of tandem blade.The results show that the long slot scheme above the tip of the front blade and the long slot positioned 10% pitch from the suction surface can effectively reduce the strength of the tip leakage vortex and the passage vortex.The long slot scheme positioned 30% pitch from the suction surface of the rear blade also significantly decreases the strength and influence range of the passage vortex and tip leakage vortex and improves total pressure loss in the tip area.The circumferential long slot located at 50% axial chord length of the front blade significantly reduces the intensity and influence range of the passage vortex and tip leakage vortex.When the streamwise or circumferential short slot and long slot respectively obtain their maximum suction flow,the suction effect of the long slot scheme on the blade tip flow field is much higher than that of the short slot scheme.The axial position of the streamwise short slot on the endwall of rear blade has less influence on the control effect of the short slot combined suction scheme.The optimal streamwise and circumferential short slot combined suction scheme has the same control effect on the complex flow field in the blade tip area as the optimal long-slot suction scheme.In order to explore the engineering applicability of the new flow control technology combined endwall suction and tandem blade,this paper applies the cascade experiment method to study the flow field structure of tandem blade and control mechanism of endwall suction on flow field in the endwall area.The experimental results show that the flow field structure in the endwall area is more complicated,and the change of the incidence angle and the inlet Mach number significantly affects the strength and range of the endwall secondary flow of tandem blade.When the suction flow rate is the same,the suction effect of the long and short slot suction scheme on the endwall of the rear blade is better than the suction scheme of the front blade.The long slot suction scheme is sensitive to the suction flow rate,and the suction earnings of the long slot suction scheme is nonlinear to the suction flow rate.The short slot suction scheme is not sensitive to the suction flow rate,and the suction earnings of the short slot suction scheme is linear with the suction flow rate.The front blade and rear blade endwall combination suction scheme significantly reduced the total pressure loss on the endwall region of tandem blade,with the increase of suction flow,the earnings of combined suction scheme do not significantly increase,and when the suction flow rate further increases,the earnings of combined suction scheme may even increase the average total pressure loss of blade.