Research On Heat Transfer And Flow Of Film Cooling Under Complex Vortex Structure

Gas turbine is developing most rapidly and has obvious advantages in modern power machinery.It is widely used in aviation,shipbuilding,power generation and other military and civilian fields.Therefore,gas turbine manufacturing technology has also become a high-end technology with high input,strict blockade,and competing development in various countries.However,with the continuous increase of the power of the gas turbine,the outlet temperature of the combustion chamber is too high,which exceeds the thermal limit of the metal material of the turbine blade,and it poses a severe test for its operation.Therefore,it is particularly important to effectively cool the turbine blade.Among the modern cooling technologies,film cooling has unique advantages and is most commonly used for cooling the blades of gas turbines,so there has great value to research and develop.In a real gas turbine,the complex three-dimensional flow structure in the blade passage makes the working environment of the film cooling getting worse and greatly affects the action of coolant.In this paper,the film cooling under a certain complex vortex system is studied and the heat transfer effect and flow characteristics are analyzed.The specific complex vortices here are generated by the cylindrical spoiler in front of the jets.In this paper,the structural characteristics are calculated and analyzed separately.Although the vortex structures in the complex vortices and the actual blades are not completely the same,they still have similarities.The analogy analysis provides a reference for the actual film cooling research.First of all,the heat transfer characteristics of film cooling under complex vortex system are studied by RANS,and the cooling effect is intuitively evaluated.By comparing and analyzing the calculation results of film cooling under complicated vortex series under three different blow ratio conditions,it is considered that when the blow ratio is low,the disturbance of the incoming vortex system is not conducive to the film cooling,but under the condition of medium and high blow ratio,the disturbance of the complex vortex system plays a role in improving the film cooling effect to a certain extent,and the improvement under the high blowing ratio is more obvious.In addition,the adiabatic cooling efficiency counter and changing trends of film cooling under four conditions of vortex action distance L of 4d,6d,8d,and 10 d are compared.The results show that when the action distance is close,cooling zone appears at the front edge of the jets,and there is an optimal position of action so that its overall cooling effect is best under this operating condition.In order to explain the different heat transfer effects,the flow characteristics of film cooling under complex vortices were further analyzed.Because the steady-state results can not describe the flow characteristics well,the DES was used for the unsteady calculation.As a result,it was found that the complex vortex incoming flow caused a certain change in the flow field structure.Among them,the horseshoe vortex in the front edge of the cylinder is smaller in scale,so there is no interference with the downstream flow of the jets.The main influences on the structure of the film cooling flow field are the arch vortex and the trailing vortex,they mainly exist and act on the middle region.The arch vortex makes parts of the middle hole jet return,the cooling zone appears in front of the jet hole,and the trailing vortex presses the coolant towards the wall with its spread in the exhibition direction,so that the the coolant coverage in the exhibition area is larger,but at the same time,it also weakens the ability of the coolant to transmit along the flow direction.Therefore,under the low blowing ratio,it cannot be obtained good air-conditioning coverage at far downstream,while this situation gradually improved with the increase of the blow ratio.