Study And Control Method Of Aerodynamic Loss On High Hub Ratio Micro-axial Flow Turbine

As small-scale combat weapons such as unmanned reconnaissance aircraft,drone aircraft and cruise missile are widely used,the turbine engine as its power unit tends to miniaturize its size.Micro-axial turbine is one of the key components of the engine,Output power,high speed,high efficiency and so on.Especially in the small flow,speed and the overall size of the case is also limited to high power,making the blade becomes low,the hub ratio increases,resulting in reduced Reynolds number channel,the role of gas viscosity increased,the relative leaves tip clearance increases,tip tip leakage loss and secondary flow loss increase.Therefore,in this paper,a high hub ratio turbine is compared with a small-scale single-stage impulse turbine for missiles to carry out the tip clearance leakage and secondary flow loss of the end wall,the analysis of small-scale lower wings and winglet flow control method and its influence on flow field parameters and turbine aerodynamic performance.The main contents of this paper are as follows:1.The research on the flow characteristics of the high hub ratio-MTE is carried out,the results show that the secondary flow loss is 2.91 times and the secondary flow loss is 5.34% higher than that of the conventional axial turbine,the leakage loss of the tip clearance is 3.6 times,the leakage loss Up to 6.6%,turbo miniaturization and increase of the ratio of the hub makes the cascade channel loss increase.2.The comparison of the technology of high hub ratio turbine winglet with micro-axial turbine rotor is compared and analyzed.The effect of winglets on vortex separation,interstitial leakage flow and interstitial leakage vorticity varies with different types of structures.The effects of the width of the combined winglets and the height of the gap on the tip clearance flow in the rotor are discussed emphatically.The results show that both the small winglet and the combined winglet reduce the tip leakage loss and the channel loss by reducing the lateral pressure difference of the tip surface.In addition,the winglet of the suction winglet is weakened by weakening the leakage vortex,The pressure surface is small by reducing the average kinetic energy of the leakage fluid in the tip clearance area,and the combined winglet can reduce the mean tip kinetic energy by increasing the separation vortex of the tip surface to clog the gap flow path and weaken the leakage fluid,Loss and channel loss,thereby enhancing the efficiency of the turbine stage.The pressure surface is superior to the suction surface in reducing tip leakage,but because of the pressure winglets strengthen the mixing of loss of leakage fluid in the tip clearance area,the suction winglet is superior to the pressure winglet in terms of lifting efficiency,The combined winglets combine the advantages of a single winglet and are superior to a single winglet in suppressing gap leaks and improving turbine efficiency.When the gap is small,the combined winglet does not play a significant role in suppressing the leakage loss.As the gap increases,the effect of the winglet gradually becomes apparent,and the efficiency of the turbine is improved obviously.The efficiency is increased by 0.464% when the gap is 5.5% H.Although the combined winglet width increase can reduce the leakage flow,the additional increased frictional losses and interstitial zone blending losses make the turbine stage efficiency substantially unchanged.3.The effect of the circumferential position,height and length on the secondary flow of the endwall fence is studied.The calculation shows that the endwall fences with the circumferential position θ = 3/4 can effectively reduce the accumulation of low energy fluid in the tail of the suction surface and weaken the mixing of the low energy fluid with the wake by hindering the lateral migration of the low energy fluid at the end wall.And the secondary kinetic energy coefficient decreased by 17.5%.When the height was 1/3 of the thickness of the endwall,the lateral wing blade could weaken the lateral migration of the low energy fluid,which could reduce the mass average total pressure loss coefficient by 14.4% The length of the wing blade is 1/2 of the axial chord length.When the length of the blade is 1/4 of the axial chord,the lateral flow of the low energy fluid can be hindered and the additional loss caused by the wing blade can be reduced.The effect is better than other length Program of the wing knife.In general,the endwall fences can block the convergence of the horseshoe vortex pressure surface branch and the channel vortex and suppress the lateral migration of the wall subsurface flow,resulting in the decrease of the low energy fluid in the corner of the suction face,weakening the mixing of the tail low energy fluid and wake.