Study On Flow And Heat Transfer Mechanism Of Honeycomb-Like Cooling Of Turbine Blade

The porous laminated plate structure is the leading technology used in turbine blade cooling,but there are still some problems such as large flow resistance,further improvement of cooling effect,and large damage to blade strength.Based on the shortcomings of existing technologies and combined with the principle of bionics,this paper obtains inspiration from the honeycomb structure of nature,puts forward the concept of new honeycomb-like cooling,and designs a series of honeycomb-like cooling structures by using the independently proposed design method,hoping to improve the comprehensive performance of leaves through the honeycomb-like cooling structure.Taking the honeycomb-like cooling structure with parallel inlet and outlet as the representative,the flow characteristics of the structure and the corresponding typical laminated structure are studied by numerical simulation.Numerical calculation of flow characteristics of honeycomb-like cooling structure and typical laminated plate is carried out under approximate engine operating conditions and normal temperature and pressure conditions.The pressure ratio of inlet and outlet is gradually changed from 1.01 to 1.05 to simulate the flow of airflow in the structure at different pressure ratios.The flow characteristics of schemes and the drag reduction mechanism of honeycomb-like cooling structure are emphatically analyzed under the same mass flow rate in actual working conditions.The results show that the structural flow loss can be effectively reduced by reducing the air flow turning angle and the change of channel section and avoiding the mutual impact and mixing between air flows.In the range of working conditions studied,the honeycomb-like cooling structure can reduce the flow loss by more than 60% compared with the typical laminated structure.The loss of the former mainly comes from multiple turns in the cavity,accounting for about half of the total loss.In addition,the structure was further optimized according to the flow resistance characteristics of honeycomb-like structure,such as reducing the number of turns in the cavity.The flow resistance characteristics experiment and corresponding simulation calculation were carried out for inlet and outlet parallel honeycomb-like cooling structure and typical laminates,and the variation of total pressure loss with Reynolds number was studied.The results show that the flow resistance of the parallel honeycomb-like cooling structure is 10~14% lower than that of the typical laminates,and the experimental results are in good agreement with the calculation results.By comparing the calculation results of different inlet angles,it is found that the inlet angle has a great influence on the flow loss of honeycomb-like cooling structure,and reducing the inlet angle is beneficial to reduce the flow loss of the structure.The heat transfer characteristics of the two schemes were also studied by numerical simulation.Under the same mass flow rate,the temperature distribution of the outer wall of the two schemes was compared and the reasons were analyzed.The results show that the heat transfer area on the inner wall of the honeycomb-like cooling structure is larger,which is 10% higher than that of the typical laminated structure,but the total heat transfer is about 4% lower than that of the latter.The main reason is that the honeycomb-like cooling structure greatly reduces the eddy current in the plate and weakens the wall impact cooling while reducing the flow loss.In particular,the turbulent column structure in the honeycomb-like structure has the lowest wall heat transfer coefficient and fails to play a full role,which is the focus of subsequent improvement.Finally,the comprehensive performance coefficient Nu/C_p is used to compare the comprehensive performance of the two schemes.The results show that the comprehensive performance of the honeycomb-like cooling structure is significantly better than that of the typical laminates,and the greater the Reynolds number is,the more obvious the advantage is.It also shows that honeycomb-like cooling structure has great potential to improve the comprehensive performance of blade,which is worthy of further study.