The Aerodynamic Analysis And The Optimization Design Of A Micro Axial Turbine

Micro turbojet engine has many advantages,such as high thrust weight ratio,high energy utilization rate and low cost,as the core power components of micro turbine.It need to have many advantages,such as,high efficiency,high flow ability,light quality and so on.But with the reduction of size,the effect of miniaturization of micro caused axial flow turbine loss increased significantly,loss proportion structure has obvious changes,making micro turbine efficiency is much lower than the conventional turbine,the secondary flow loss increased significantly and occupy a dominate position of the total losses.Therefore,this article in order to reduce the micro axial flow turbine secondary flow loss as the main purpose,on the basis of a turbine unit of micro turbojet engine,full three-dimensional simulation of the turbine flow distribution was conducted by the CFD(computational fluid dynamics)software CFX 14.0.Three-dimensional Reynolds averaged N-S(Navier-Stokes)equations with SST(shear stress transport)turbulence model were used to predict the micro axial turbine internal flow.And carry out micro axial flow turbine curved blade,swept blade profile design of technology research at the same time,also did explore the combination design method of it,finally determines the optimization scheme of the turbine.The main content of this paper can be described as:1.The paper carried on research of the micro axial flow turbine stator blades curved blade designing technology.On the basis of the proto type straight blades ensure blade airfoil is constant,changing the blade fold line,the product of several curved blade designing scheme: high of bending is h/2,respectively angle of 10 degree,20 degree and 30 degrees symmetry bending and angle of 20 degrees "J" type curve.Through curved blade flow field and the whole level of turbine analysis proved that the performance of curved blade can change the internal flow field in turbine pressure distribution,to assume the "C" type pressure distribution,leading to increasing of export flow Angle of stator blades and reducing the blade tip export flow Angle of stator blades.It not only makes the turbine blade aerodynamic loading is lower but also increases ability of the flow doing work.2.In this paper,the designing and technology research of the micro-axial flow turbine's stationary blade is carried out.Firstly,the flow field of the stator is analyzed,and then the mechanism of the flow field is analyzed.Finally,only the treatment of the blade root is carried out.By comparing the effects of different swept forms on the flow field of the stator leaves,the swept angel suitable for this impeller is determined.Swept angel is-30°,-20°,-10°,10°,20°,30°and swept depth(0.1,0.2,0.3,0.4,0.5)on the seco ndary flow,flow loss and downstream flow of the turbine stator channel were also analyzed.The results show that with the increase of the swept angle,the effect of improving the root end wall area is obvious.While the loss of the middle channel increase s,and when the swept angle exceeds 20 °,the increase of the loss is faster than the improving of the blade root.For the swept depth,its effect is similar to the swept angle.Finally,the above results are determined to be suitable for this turbine stag e optimum swept of the swept leaves for the swept of swept angle is 20 °,swept depth is 0.5.3.In this paper,micro axial flow turbine blade the aft-loaded airfoil designing technology research was carried out.Studying the effect of the blade thicknes s distribution and arc in the circumferential chord length on the load distribution and secondary flow and impeller performance.The results show that the arc is the main influence factors of load distribution,as the arc chord reduces load center of gravity moved gradually and secondary flow intensity is weakened,total flow losses are reduced;Blade thickness distribution is the assistance of arc,appropriate increase the thickness of leaf type will not reduce the impeller performance;Only when these two kinds of geometry factors work together,can make the impeller presents typical load characteristics in the back.This paper has carried out the combination of micro axial flow turbine blade design method research according to the above scheme of curved b lade changed after loading profile product fold line way after determined the appropriate for the micro axial flow turbine blade loading.