Aerodynamic Design And Noise Analysis Of High Bypass Ratio Fan

The maturity of the geared turbofan technology drives the development of turbofan engine to the direction of high bypass ratio.The principle is to add a gearbox between the fan and the booster stage.The deceleration ratio is obtained through the gearbox,so that the fan and the booster stage can work independently at different speeds,thus reducing the fan speed and enhancing the fan load.Because of the larger fan radius,the reduction of the speed of the geared turbofan engine can effectively reduce the loss of blade tip shock wave and reduce the rotation noise.In addition,for high load and low speed fan,we apply high load large camber low loss diffusion blade to fan rotor aerodynamic design and stator matching,combined with multi-point optimization method.This method can inhibit the separation of the trailing edge and reduce the broadband noise of turbulent pulsation.Based on the above design concept,this paper has completed the aerodynamic design of the high bypass ration fan(load coefficient is 0.6).These work are also based on the study of high load and low speed fan in research team.Flow field characteristics and acoustic characteristics analysis are performed after make this one and another two fans(load coefficient are 0.6 and 0.88)in comparison.The numerical simulation of flow field shows that compared with other two fan stages(load coefficient are 0.6 and 0.88),when reaching the design pressure ration and mass flow rate,the ultra-highly loaded fan stage(load coefficient is 0.88)has the highest stage efficiency which is 0.9002,the surge margin is also the maximum which is 46.19%.The acoustic numerical simulation shows that whether for single rotor or fan stage,the noise will reduce gradually with the increase of load coefficient.Compared with the normal load rotor(load coefficient is 0.3),the noise of the ultra-highly loaded rotor(load coefficient is 0.88),is reduced by 25.34 dB.The noise of the fan stage was reduced by 11.71 dB when the stator was matched.Finally,we explore the effect of the back and forward sweep and the distance between rotor and stator.The results of acoustic numerical simulation show that the increase of the interstitial clearance can effectively reduce the interference effect between rotor and stator which can reduce the noise.The forward sweep has no obvious effect on fan level noise reduction,while the back sweep can effectively reduce the noise.