The Numerical Research On The Modification Of Tandem Cascade Using Aspiration Cascade

High Thrust-Weight-Ratio has always been one of main goals for modern aero-engine design.And one of the key techniques is to design the compressor blades with high loading and less loss,which means it not only has high isentropic efficiency and wide oprating range,but also has higher pressure ratio and less number of stages.To meet the above-mentioned requirements,the flow control techniques are often used in the aero-engine design.As one of the passive control strategies,tandem cascade had widely been used in the last stator design, such as Alouette,TurmoⅢc,J85,Viper522,J69,AЛ—31Φengines and so on.But tandem cascade has some insurmountable disadvantages.For example,it has complex structure,and it could just be suitable to use in the case with high hub tip ratio and low mass flux.Meanwhile, the tandem cascade also increase the axial length of the last stage,which cause the aero-engine weight to increase.In contrast,the boundary layer aspiration technique not only can suppress the boundary layer separation,increase the pressure ratio effectively,but also can decrease the axial length and weight of the compressor.Therefore,the boundary layer suction would be used in the highly loaded stator in this thesis to replace the tandem cascade often to appear in the modern aero-engine.Firstly,the tandem cascade based on the high loading design requirement and two aspirated single row cascades with the different blade chord length are designed by using direct and inverse design method according to the criterion with the same diffusion factor and the turning angle under the specific inlet condition and back pressure at outlet.And then the flow field and aerodynamic characteristics of both tandem cascade and aspirated cascade are analysed by the Fine/Turbo software code of NUMECA Co.At last,the design and off-design performance of aspirated cascades with different suction mass-flow,suction slot locations and suction slot widths are compared to build the design method of the aspirated cascade.The results based on the large number of numerical experiments indicate that under the condition of same inlet math number,outlet pressure,and the same diffusion factor,the total pressure loss for the single row aspirated cascade would be less than the tandem cascade's,and the outlet static pressure be higher than the tandem cascade's.It should be feasible to use aspirated cascade to replace the tandem cascade in the design of high loading compressor blade.With these primary work,this thesis put forward an innovation thinking in the design of high loading compressor blade.This should be usable technique support for designing the high trust-weight-ratio aero-engine.