Study On Aerodynamic Design Method And Flow Control Of Helium-Xenon Turbine

The closed Brayton cycle power conversion device using helium-xenon mixture as the working medium has better compression characteristics than helium,which reduces the mechanical size of the impeller,making it an ideal power for deep space probes.Conversion device.In the entire closed Brayton cycle power conversion device,the helium-xenon turbine is the core component,and it plays an important role in the operation of the entire system.Due to the large difference in physical properties between helium-xenon mixed gas and fuel gas,the characteristics of helium-xenon turbines are also different from those of ordinary gas turbines.The helium-xenon turbine has the characteristics of short blades,large turning angle of the rotor blades,small hub ratio,and transonic flow of the internal working fluid,which leads to a significant increase in the proportion of shock wave loss and secondary flow loss.This paper explores the aerodynamic design method of the helium-xenon turbine,and studies the control method for the internal shock loss and secondary flow loss.In order to provide a certain reference value for the optimization method of helium xenon turbine aerodynamic design.Firstly,the research on the aerodynamic design method of helium-xenon turbine was carried out,and the selection method of blade profile and aerodynamic parameters was explored.By studying the influence of different aerodynamic parameters on turbine efficiency,it is determined that the optimal design plan is when the load coefficient is 1.8,the flow coefficient is 0.6,the reaction degree is 0.2,and the axial speed ratio is 0.8.On this basis,the influence of the axial chord length of the stator blades and the rotor blades on the output power and efficiency is discussed.Secondly,in view of the high shock loss inside the helium-xenon turbine,and explores the influence of the blade geometry parameters and the blade profile curvature on the shock intensity.Through research,the best value range of unguided turning,trailing edge wedge angle,and stagger with low shock loss is obtained.In addition,by comparing the impact of different outlet channel widths on the shock wave intensity,it is found that appropriately increasing the outlet channel width can also reduce the shock wave loss.At the same time,the influence of the curvature of the pressure surface and the front suction surface of the throat on the trailing edge shock is systematically analyzed,and the blade profile curvature control method is obtained to reduce the shock loss.The specific method for reducing shock loss is applied in the three-dimensional space of a helium-xenon turbine,and the improvement of the three-dimensional flow field inside the turbine is analyzed.Finally,in view of the problem of large secondary flow loss,a comparative analysis of the internal flow conditions and aerodynamic performance of the original blade,forward curved blade,reverse curved blade and reverse J-curved blade.At the same time,by studying the effects of different bending angles on the performance of reverse-bending blades and reverse-J-bending blades,it is determined that the blade with the best internal flow condition should be a reverse-J-bending blade with a bending angle of -10°.In addition,the effect of linear,concave curvature,convex curvature and combined concave-convex curvature on the upper end wall of the turbine is also studied,and it is found that the convex-curvature end wall can maximize the aerodynamic performance of the turbine stage.Finally,the convex-curvature upper end wall stator and the reverse J-bent rotor blade with a bending angle of -10° were combined into a new turbine stage,and it was found that its off-load characteristics were significantly better than the original turbine stage.