Study On Unsteady Film Cooling Characteristics Of Turbine Shroud

With the rapid development of aviation in various countries,in order to achieve a higher thrust-weight ratio and thermal efficiency of aero-engine,the turbine inlet temperature increases continuously,which leads to higher requirements on cooling of the key parts of the turbine.The turbine shroud is exposed to tip leakage flow,and bears high thermal load and high temperature cycle thermal shock,which has become a common life limiting factor for the turbine stage of current aero-engines.However,there is still a lack of research on unsteady film cooling of the turbine shroud,and the detailed mechanism of heat transfer and flow has not been clarified.Therefore,it is necessary to conduct in-depth research on unsteady film cooling characteristics of the turbine shroud.Numerical simulation on unsteady film cooling process of high pressure turbine shroud under high speed blade sweep was conducted.The slip mesh was used to realize relative motion between the turbine blade and the turbine shroud wall.Effects of blowing ratio,forward and inverse jet direction,film hole jet angle on film cooling characteristics of the high pressure turbine shroud were analyzed.It is found that the film cooling efficiency distribution of the turbine shroud is mainly affected by tip leakage flow and tip leakage vortex generated by blade rotation.Tip leakage vortex is manifested as suppression and binding of cool gas.From strong to weak,the suppression effect on the cool gas was followed by tip leakage vortex,tip leakage flow and mainstream.In the case of inverse jet flow,the pattern of tip leakage vortex will change and the distance between the tip leakage vortex and the shroud will increase.Aiming at the phenomenon of uneven film coverage in the turbine shroud at a small blowing ratio,this paper starts with uneven distribution of cool gas in each row of film holes caused by drastic pressure changes along the main flow direction,achieve better cooling effect by changing the diameter of film hole and the structure of the cooling chamber.It is found that changing the structure of the cooling chamber had better cooling effect.