Research On Turbine Shock Weakening Based On Optimization Design Method

As the gas turbine load continues to increase,the shock wave inside the turbine is enhanced and the shock wave weakening has become an important research direction.However,the research on shock mechanism and weakening method at home and abroad is not yet mature,especially in the application of multi-operating point shock weakening and shock weakening method in turbine design,and related research results are rarely seen.This paper focused on the above situation,using the optimization design method to weaken the turbine shock wave,built a single point,multi-point turbine shock weakening optimization design platform,and combined with the turbine design method to achieve the shock wave weakening on high load turbine optimization design.Firstly,a feasible single-point optimization design method was proposed for the difficult on global optimization design of turbine cascade,such as long calculation time and large sample space.This method took 17 parameters of control profile as optimization variables and adopted the second multi-objective genetic algorithm.The genetic algorithm performs global automatic optimization.Based on this method,a cascade global optimization design platform was built.Using this platform,a supersonic turbine cascade was optimized by axial consistency fixed and free.The numerical results showed that the total pressure loss coefficient of the two sets of optimized design cascades was 19.5% and 10.0% decreased than the reference cascade,and the shock intensity in the flow channel was weaker.On variable operating conditions,the total pressure loss coefficient was also decreased.After analyzing the flow field and shock structure in depth,it was found that the outer tail shock had a greater influence on the total pressure loss than the inner tail shock.By reducing the airflow expansion angle or the inner tail shock deflection angle,the outer tail shock can be effectively weakened.Based on the single-point optimization design,in order to further improve the aerodynamic performance of the cascade on the whole operating condition,a multi-operating point optimization design method was developed.Comparing the single-point and multi-point optimization design methods,it was found that the aerodynamic performance of the single-point optimized design of the cascade positive angle of attack was reduced,while the aerodynamic performance of the multi-point optimized design cascade was improved compared with the original cascade.The total pressure loss coefficient of the design condition was reduced by 5.8%,and the total pressure loss coefficient within the operating condition range was reduced by up to 37%.Analysis of the flow field revealed that the upstream and downstream shocks were mutually constrained to form a complex shock-viscous loss structure.Multi-point optimization design adjusted the proportion of each loss factor to ensure that the loss of each operating condition was more balanced,so as to improve the performance of the whole operating condition.In order to realize the application of the cascade optimization design method of shock wave weakening in turbine design,the aerodynamic design of a single-stage ultra-high load axial flow turbine with a pressure drop ratio of 5.6 and a load factor of 2.0 was carried out.Through the one-dimensional design and parameter analysis,the reasonable blade design parameters were obtained,and the blade profile was completed based on the constructed turbine cascade shock weakening optimization design platform.The flow field numerical simulation of the designed turbine was carried out.The results showed that the designed turbine met the design requirements,the isentropic efficiency of the design point was 89.5%,and it performed well on variable operating conditions.The feasibility of the turbine shock weakening method is further verified and the preliminary application of the method in turbine design is realized.