Numerical Investigation Of Flow Control Using Undulating Blade In Compressor Cascade

Severe flow separation of compressor cascade might cause flow blocking and increased loss.To provide a new idea to suppress flow control,this paper performs investigation on undulating cascade performance,flow field characteristics and unsteady flow mechanism.Undulations are added to a straight blade and steady simulations were performed to study the effect and control rule of geometry parameter of undulating blades,including stacking methods,wavelength and enlarge factor.Furthermore,unsteady simulations were conducted to further discuss about the flow field detail and the evolution mechanism of streamwise vorticity.The results show that undulating blade is a gentle passive flow control mechanics,suppressing flow separation at large incidence angle while keeping the designed angle performance.The design parameters of undulating blade show great impact on cascade performance.Thus,{k~m/W}is firstly introduced as a new parameter to evaluate the undulating geometry to reach the importance balance between enlarge factor k and wavelength W.The results show that at 0 deg incidence angle,total pressure loss coefficient increases as{k~m/W}increases.While at 8 deg incidence angle,there might be a critical value,which the total pressure loss coefficient increases rapidly once it is greater than.Moreover,the unsteady flow analysis shows that the streamwise vorticities induced by undulations play an important role in the flow control process.The interaction between streamwise vorticities contribute to the redistribution of flow separation,which is clear in the crest section and worse in the trough section.Besides,vorticities shedding from leading edge blend with the vortex system near trailing edge periodically also allow the boundary layer reenergize and enhance the ability to resist flow separation.