Numerical Investigation Of Boundary Layer Suction In A Highly-loaded Sectorial Compressor Cascade

The rapid development of aviation industry has put forward more and more stringent performance requirements for aero-engines.As one of the three core engines of gas turbines,the compressor increasingly pursues a higher single-stage pressure ratio and single-stage efficiency,so that it can achieve a higher pressure ratio at less stages and keep a considerable economical efficiency at the same time.Adopting a highly-loaded diffuser profile is the most direct and effective scheme to realize a high pressure ratio,but it will also aggravate the secondary flow and the coener separation in cascades,which will result in serious mixing loss and even inducing stall and surge.This characteristic greatly inhibits the majorization of compressor performance.The study shows that it is a very effective way to improve the pressure ratio and efficiency of compressors by using a highly-loaded diffuser profile with the support of proper boundary layer suction,which plays a role in weakening the flow separation of the boundary layer on the wall.The subsonic highly-loaded sectorial compressor cascade NACA0065-K48 was studied in this research.It firstly investigated the loss mechanism and characteristics of sectorial compressor cascades and the performance of varying incidences by numerical simulation.On the basis of it,the boundary layer suction which mainly includes the streamwise groove suction on the lower endwall and the radial groove suction on the suction surface was studied systematically.It aimed to reveal the action mechanism of boundary layer suction inhibiting flow separation and reducing loss.The results show that there are five main vortex structures in the flow channel of highly-loaded compressor cascades:horseshoe vortex,passage vortex,wall vortex,corner vortex and concentrated corner vortex.The separation and secondary flow of the endwall boundary layer are the main courses of the complex vortices and the serious loss in corner.Because of the existence of the radial centrifugal force in sectorial cascades,the separation degree in the lower corner is greater than that in the upper corner,and the increase of incidence will aggravate this unbalanced flow phenomenon.The stall margin of the cascade is-10° to +6°,and the aerodynamic performance is better under the condition of small negative incidences(-6°to-3°).The suction on the lower endwall and the suction surface can both improve the performance of the cascade,but the suction on the suction surface away from the tailing edge cannot fundamentally weaken the profile loss,and it is not the best way to actualize the performance optimization.The two basically improve the flow field and reduce the loss in corner by absorbing the endwall boundary layer,especially in the lower corner.The suction effect of the separated helical point on the lower endwall is the key to improve the lower corner separation.The comparison indicates that the half-blade-height scheme performs better than the whole-blade-height scheme of the radial groove suction on the suction surface,but the lower endwall suction has better effect overall.EW2 is optimal when absorbing 0.50%mass flow of incoming flow,the overall total pressure loss is reduced by 27.65%,the static pressure ratio is raised by 8.69%,and the positive stall margin is extended to +12°.