Research On Experiment And Loss Control Mechanism For Tandem Cascades

Compared with the conventional single-row cascade,the tandem cascade has more design freedom and more room for performance optimization.It performs better than the single-row cascade,and can effectively increase the stage load and enlarge the surge margin.In the future,the tandem cascade is a research direction that deserves attention in the process of compressor development towards high load and high efficiency.The experiment and loss control mechanism research of tandem cascades have good engineering value.In this paper,the flow field structure and aerodynamic performance of the prototype cascade and the corresponding three sets of modified tandem cascades are studied through both experimental and numerical methods,and the reasons for the better performance of the tandem cascade are studied.On this basis,the influence of the relative position of the blades on the flow and performance of the cascade and its mechanism are further studied.First,the two-dimensional and three-dimensional flow structure and aerodynamic performance of the prototype blade cascade under different angles of attack are studied.The results show that because the prototype blade cascade is a high-turning cascade,and the flow separation of the suction surface is serious,the flow field structure is easy to become asymmetric.As a result,in the linear cascade experiment,the measuring position of the five-hole probe is in the back-flow zone.In order to better study the performance of the airfoil shapes,end wall suction control is required.Numerical and experimental studies on prototype blade cascades with suction grooves show that the two-dimensional characteristics of the flow at the middle height of the blade has been greatly improved,but end wall suction cannot eliminate flow separation completely,and sometimes may cause additional losses.Secondly,by studying the flow field structure and aerodynamic performance of the tandem cascade No.1,and comparing with No.2 and No.3,the influence law and mechanism of the geometric parameters of the tandem cascade on the flow and performance are explored.The results show that the flow separation of the tandem cascade is smaller,the loss is lower,and it has better performance.In addition,the geometric parameters of the tandem cascades No.1 and No.3 are similar,and the difference in flow and performance is small.However,because the axial distance,circumferential distance and width of gap flow channel are larger,the flow separation phenomenon of No.2 is more serious and the performance is poorer.Finally,taking the tandem cascade No.1 as the object,changing the two geometric parameters that affect the relative position of adjacent blades,the width of the gap flow channel and the axial overlap,this paper further explores the changing law and mechanism of the flow structure and aerodynamic performance of the tandem cascade.The results show that as the gap flow channel becomes narrower,the total pressure loss first decreases and then increases.As the axial overlap decreases,the total pressure loss first decreases and then increases as well.In addition,the change of the relative position between the first two rows of blades has a more significant impact on the flow and performance of the tandem cascade,and the width of the gap flow channel has a more significant impact on the flow and performance of the cascade than the axial overlap.