Research On Film Cooling Effect Of Trenched Hole On The Leading Edge Of Turbine Blade

With the increase of thrust-to-weight ratio of aeroengine,the inlet temperature of turbine has a great increase.As an effective blade cooling method,film cooling can well improve the thermal bearing capacity of turbines.Therefore,the research and development of high performance film cooling method has become important.Due to many factors such as manufacturing,cascade flow and internal cooling,the design of film holes should not be too complicated.Instead,it should start with some simple and feasible cooling structures to study the key flow and cooling mechanism,and improve the cooling effect,which is more practical.The trenched holes are one of the most representative cooling structures.Due to the factors such as swirl generator,cooling dilution flow,fuel injection and inhomogeneity of combustion area,the physical quantities at the exit of the combustion chamber are greatly different in radial and circumferential directions.Local overheated areas,called hot streaks,appear in temperature,and obvious circumferential angles and pitch angles,called swirl,appear in velocity.According to the actual situation,the cooling effect of the trenched holes should be considered.In this paper,trenched holes are arranged at the leading edges of stator and rotor to analyze the film cooling effect.First,under the background of uniform inlet conditions,four blowing ratios of 0.5,1,1.5 and 2 were selected to analyze heat transfer and aerodynamic parameters such as adiabatic temperature distribution,cooling efficiency,total pressure loss and flow structure in trench,so as to explore the improvement effect of trenched holes on film cooling.The results show that the cooling air can be filled in the trench by means of "spiral" collision and radial flow along the wall surface,than overflow from the trench under the condition of high blowing ratio,which increases the coverage area of the cooling.The cooling efficiency of the trenched holes on the suction surface of the leading edge is improved more obviously than that on the pressure surface.The total pressure loss is also lower than that of the ordinary circular hole.Then,according to the background of hot streaks and swirl at the combustion exit,four typical blowing ratios of 0.5,1,1.5 and 2 are still selected,hot streaks and swirl is directly facing the leading edge of stator,and there are two swirling directions,clockwise and counter-clockwise,to explore the film cooling effect of trenched holes.The results show that hot streaks lead to an overheated area in the leading edge of stator,and the swirling direction directly affects the position and shape of the leading stagnation line and changes the thermal load area.Different swirling directions will lead to different flow directions of the cooling,which will have different influences on the blade surface.The cooling effect of the trenched holes is still much better than that of the circular hole under the condition of hot streaks and swirl,but the total pressure loss is higher than that.The flow structure in the trench would be distributed differently from blade tip to blade root by swirl.