The Three-dimensional Design And Performance Investigation On High Bypass Ratio Fan And Booster

The single stage transnoic fan and the booster is main aerodynamic component of twin-spool high bypass ratio turbofan engines.The fan produces about 75% total thrust of the engines both at take-off and curise condition,and therefore the performance of the fan always determine the whole engine's performance directly.The strong shock wave located on the outer part of span of the transnoic fan always lead to a high shock loss,separarion loss and secondary flow loss.Although the pressure ratio is relatively low in the twin-spool engines' booster,the blade loading is still relatively high due to the low blade tip speed,which will result in the hub-corner stall and separation,causing the high loss of total pressure.In order to solve the issues above,the blade of modern advanced high bypass ratio fan and booster always apply three-dimensional design,and to know the influence of three-dimensional blade to the performance of high bypass ratio fan and high loading booster,this thesis has carried on the related research.Firstly,this thesis use the one-dimensional procedure,S2 procedure,blade model procedure to design and modify a high bypass ratio fan(bypass ratio is 12.5 and the mass flow is 248.4kg/s)as well as a booster(pressure ratio is 1.45 and mass flow is 18.4kg/s).Finally,the efficiency of fan and booster get to 91% and 89% separately.Based on this fan and booster,the CFD method was applied to investigate how the variation of sweep influence on the performance,stall margin and tip leakage of fan as well as how the variation of lean influence on the performance and hub-corner stall of booster.In the study of fan-swept,it is found that the forward sweep design of fan can effectively increase the fan stall margin,and the increase magnitude of stall margin will increase as the swept angle.Specifically,when the swept angle is 25° the stall margin will increase by 4% and when the swept angle is 50° the stall margin will increase by 10%.In addition,the influence of swept design to the fan peak efficiency is extremely small,but the forward sweep fan can increase the high efficiency operating range of the fan.While the effect of swept design on the tip leakage is mainly reflected in the fact that the swept blade can reduce the thickness of the tip boundary layer of the blade,contributing to the reduction of low-energy fluid entrained by the leakage vortex and thus reducing the tip leakage loss.In the study of lean stators,it is found that the BLB(Bezier Curve-Straight line-Bezier Curve)stators with high lean height and can effectively restrain the accumulation of low-energy fluid in the corner area and suppress the low energy fluid leaps up,which increases the operating range of the booster.Besides,the BLB stators can all increase the efficiency of booser near the design point,and increase the peak efficiency by about 1%.Moreover,a larger scale separation vortex is generated at the near-stall near the leading edge of the BLB stator with large lean angle and the leading edge of the SBC stators.This separation vortex should be the main reason causing the stall of the booster with the above static stators.