The Research On Flow Field And Performance Of Transonic Multistage Splitters Centrifugal Compressor

Centrifugal compressors are widely used in aviation,aerospace,and energy due to their simple structure,single stage with high pressure,and great stability.With the advancement of technology and the demand of high performance of products,the single-stage pressure ratio is getting higher and higher,and the absolute Mach number of impeller outlet is also getting higher and higher.This brings great challenges to the impeller aerodynamic design and the reasonable matching of the impeller and stationary components.In this paper,the centrifugal impeller with a pressure ratio of 7 is taken as the research object to study the impeller and the matched diffuser.The specific contents include the following parts:(1)The influence of the splitter blade parameters of the transonic impeller on performance.Using an orthogonal test to explore the primary and secondary factors of the influence of variables of the splitter on the impeller performance,and obtain the primary and secondary factors.According to the test results,a baseline impeller with the number of splitter stage is 1 had a better performance,and the improvement effect of parameter changes on the flow field and performance is analyzed.(2)The influence of multi-stage splitter blades and types on the internal flow field and performance of the impeller.By changing the number of splitter blades and the position of the leading edge,the law of its influence on the development of leakage flow and secondary flow was studied.The results show that the increase in the number of splitter blades is beneficial to suppress the circumferential movement of the leakage flow.The longer the axial length of the splitter blade,the better the effect of suppressing the circumferential migration of the leakage flow at the leading edge;However,the increase in the number of splitter stages also exacerbates the secondary flow,increase the degree of disorder of the impeller outlet.Therefore,it is necessary to comprehensively consider the sensitivity of the leakage flow and the secondary flow to the main flow in order to select an appropriate stage number.For this pressure ratio,the stepped blade with a split stage of 2 improves the uniformity of the outlet flow and has the best aerodynamic performance.(3)For transonic flow,explore the influence of structural parameters of wedge diffuser on performance.The leading edge,trailing edge and expansion angle of the wedge diffuser on the internal flow field is studied.Comparing several groups AR of different leading edge,the smaller the ratio,the greater the shock wave loss in the diffuser,the aerodynamic performance is reduced,and the interference between the impeller and the diffuser is strengthened;The trailing edge pattern changes the area rule of the flow channel by cutting the pressure surface profile and affects the pressure gradient.This paper compares a variety oftrailing edges.The starting point of the arc is later and the tail cutting type with a smooth Bezier curve is the best;the change of the expansion angle changes the proportion of shock loss and separation loss in the overall loss.Due to the high mach number of the diffuser inlet and the the shock wave is high,increasing the expansion angle causes a significant decrease in performance.(4)Research on different types of diffusers.Explore the effect of structural changes on flow separation.Result shows that the boundary layer of the airfoil diffuser casing develops rapidly due to the high incidence,and the performance is not good when the trans / supersonic flow is flown;The improvement of the flow field of the half-height diffuser changes with the gaps,the determination of the gap depends on the ratio of mixing loss and separation loss.Unsteady calculation results show that the pressure fluctuation at the inlet and outlet of the half-height diffuser is small,and the flow field stability is good;The wedge diffuser with splitter blades improves the separation of the internal flow field.The position of the splitter blade should avoid secondary acceleration in the flow field,and the improvement of the separation loss should be greater than the effect caused by the wake.In this paper,the radial length of splitter is 80% of the length of the main blade,and the circumferential position centered has the better performance.The results of this paper provide a reference for the aerodynamic design and optimization of transsonic high-pressure ratio centrifugal compressors.