Investigation On Flow And Heat Transfer Characteristics Of Film-effusion Cooling

With the aero engine thrust weight ratio increasing,it faces more severe challenges at high temperature.As the most important part of the combustion chamber,the flame tube bears the highest thermal stress during the combustion process.In order to ensure the durability and reliability of the flame tube,it is necessary to use advanced and efficient cooling measures to cool the wall of the flame tube.The film-effusion combination cooling structure is an advanced cooling method which integrates the advantages of pure film cooling and pure effusion cooling.At present,the research on the cooling characteristics and influencing factors of the film-effusion cooling structure is not enough.In order to study the cooling characteristics of film-effusion combination cooling structure,three kinds of test pieces of different effusion cooling holes arrangement but equivalent orifice area were designed.The effects of aerodynamic parameters and geometric parameters on the overall cooling efficiency,adiabatic cooling efficiency and the convective heat transfer coefficient were investigated experimentally and numerically.The main conclusions are as follows:(1)The overall cooling efficiency and adiabatic cooling efficiency are less affected by the main flow Reynolds number within the parameters of the study,but convective coefficient is increased gradually with the increase of main flow Reynolds number.(2)The heat transfer characteristics of the film-effusion cooling structure can be affected by the blowing radio.The overall cooling efficiency of the experimental plate is obviously increased with the increase of the blowing ratio when the blowing ratio is increased from 0.5 to 4;however,the overall cooling efficiency and adiabatic cooling efficiency do not show a significant increasing trend when the blow ratio is over 4,and convective heat transfer coefficient increases with the increase of the blowing ratio.(3)The overall cooling efficiency,adiabatic cooling efficiency and convection heat transfer coefficient of the effusion cooling structure are greatly affected by the film slot.Generally speaking,the overall cooling efficiency,convective heat transfer coefficient and adiabatic cooling efficiency can be enhanced by the film slot.(4)For the three test specimens,the adiabatic cooling effectiveness and the convective coefficient of the test plate III with the largest stream wise spacing are the largest,and followed by test plate II with medium stream wise spacing,and the minimum of test plate I with the minimum stream wise spacing.According to the comprehensive cooling effect,the overall cooling effect of the test plate I is the highest after the blowing ratio is less than 5;When the blowing ratio is over 5,the overall cooling efficiency of the test plate III has been significantly improved in the latter stage.