Research On Influencing Factors Of Film Cooling Efficiency Based On Taguchi Method

Film cooling technology is now widely used in the cooling of gas turbines,and its development directly affects the stability and long-term operation of gas turbines.Adopting innovative structure and selecting optimal parameters in film cooling system is the most effective way to improve film cooling efficiency.Based on the control variable method and Taguchi method,the numerical study of flat plate and film cooling structure with transverse groove is carried out in this paper.Firstly,the cooling efficiency and flow field structure of flat plate and film cooling structure with transverse groove are compared and analyzed by using the control variable method,and the effects of different blowing ratio,incident angle and hole spacing are studied.The results show that film cooling with transverse grooves can inhibit the generation of CRVP,increase the spanwise momentum of the cooling jet at the outlet of the cooling jet,reduce its normal momentum,and make the film more evenly distributed in the spanwise direction and closer to the wall flow.The film cooling efficiency decreases with the increase of blowing ratio,increases with the increase of incident angle and increases with the decrease of hole spacing;Film cooling with transverse grooves increases with the increase of blowing ratio and with the decrease of hole spacing.The effects of three geometric parameters of transverse groove,namely hole spacing S/D,transverse groove height H/D and transverse groove width W/D,on cooling efficiency and flow field structure are also systematically analyzed.The results show that the film cooling efficiency decreases with the increase of the hole spacing S/D,increases with the increase of the transverse groove depth H/D,and slightly decreases with the increase of the transverse groove width W/D.When the flow field develops and stabilizes,the optimal parameters of the three factors can be obtained as S/D=1.5,H/D=0.75,and W/D=2.5respectively.Finally,Taguchi method is used for experimental design,the parameter design scheme is optimized,and the simulation times are greatly reduced.Three influencing factors of flat plate film cooling and four influencing factors of film cooling with transverse groove are studied respectively.By comparing the value of K and the value of R,it is concluded that in the flat film cooling,the contribution rate of the three factors to the cooling efficiency of the flat film is ranked as follows: hole spacing > incident angle > blowing ratio.In the film cooling with transverse grooves,the order of the contribution rate of the four factors to the film cooling efficiency is: hole spacing > transverse groove depth > blowing ratio > incident angle.