Effect Of Tandem Cascade On Performance Of Transonic Fan

With the rapid development of aviation industry, large thrust-weight ratio ofaero-turbine engine has put a further demand on the aerodynamic performance ofcompressor. To minimize the number of compressor stages, lower the engine size andweight under improving total pressure ratio and efficiency as much as possible, theinvestigation of highly loaded and high performance cascade has important significanceat the increasing of compressor aerodynamic performance. Tandem cascade is morehighly loaded and has a stronger ability of averting flow separation and better off-designperformance characteristics. Based on the understanding above, the paper investigatesthe effects of tandem cascade on the performance of fan systematically.The paper took tandem cascade in a certain fan stage as research subject, andinvestigated the effect of rear blade peripheral and axial displacement in tandem cascadeconfiguration on the performance of tandem cascade and fan stage under designcondition,and explored the possibility that variable camber mode in tandem cascadeimproves the performance of fan stage at off-design conditions. During the studiesnumerical simulation, pre-processing and post-processing were proceeded by usingFINE/TURBO suite of softwares.The result shows that the numerical results of fan stage agree well with those ofexperiments, which verifies its reliability. And the reasons of difference are given.Through the comparison between different cases operated on the fan stage under designrotating speed differing in peripheral and axial displacement of the rear blade followingthe tandem cascade, the conclusion comes as follows. The rear differs in peripheraldisplacement could adjust the distribution of low energy fluid effectively. Theappropriate peripheral displacement could suppress flow separation on blade suctionside. The best peripheral displacement case is that rear blade is front blade pressuresurface about twenty to percent of pitch，of which isentropic efficiency increase1.6percent and mass flow increase2.1percent. Axial displacement of rear blade has effecton the condition of flow separation on rear blade suction surface and the ability of staticpressure diffusing on a certain level. The prototype has the applicable axialdisplacement of rear blade. At89.3%design rotating speed, comparing to the original，isentropic efficiency, surge margin and mass flow in the project with the optimum rearblade peripheral all increase significantly. There is no obvious difference between the two cases at112.5%design rotating speed. By adjusting installation angle of rear bladeaccording to different rotating speed, suitable attack angle is assured and then flowseparation is weakened. The performance of fan stage improves in varying degrees atthree different rotating speed，which verifies the possibility that variable camber modein tandem cascade could enhances the performance of fan stage at off-design conditions.