| Aviation gas turbines are developing with a high-performance trend of high thrust ratio and low fuel consumption.High-loading,high-efficiency,less stages,and small-sized turbines can satisfy the development needs of modern aero-engines.In order to improve the engine performance of the gas turbine,it is of great significance to enhance the performance of a single turbine blade and reduce the energy loss during its work.The flow of gas in the turbine cascade passage is extremely complex.The flow of gas through the turbine passage,converts its high enthalpy into kinetic energy and then transform into mechanical work.In this process,the gas flow is complex in the structure of the rotating machinery,the flow will causes a series of secondary flow losses.The leakage losses caused by the leakage flow phenomenon in the tip clearance will obviously cause the reduction of the working ability of the turbine blade and in the meanwhile reduce the efficiency,which will also have a negative impact on the overall efficiency.The purpose of this reserch is to study the control method of the gap leakage flow phenomenon generated by the clearance of a single turbine straight cascade by numerical methods.Firstly,a passive flow control method of a specific structure of honeycomb tip is used to control the tip clearance leakage flow,and the mechanism of this flow control method is analyzed,it was found that the leakage vortex of the honeycomb tip was weakened,the core of the passage vortex moved up,and the energy loss decreased.Then,the different depths of the tip honeycomb cavities are investigated for the tip clearance leakage.The rule of influence showed that when the depth of the tip honeycomb was 1% relative to the leaf height,the leakage flow suppression effect was the best,and the mass of the leakage decreased by 10.96% relative to the flat tip.Finally,on the basis of this honeycomb parameters,the idea of the tip structure of the leaned honeycomb is proposed and calculated.Firstly,the tip clearance leakage flow control with the honeycomb leans to different directions was explored.It was found that when the honeycomb cellular leans to the direction of the incoming flow,the mass of the leakage is less than leaned to other directions.It can reduce the leakage by 15.31% relative to the flat tip.The effect of different lean angles of the leaned honeycomb cavities on the leakage control is investigated.It is found that the lean angle of the honeycomb cavities and its leakage control effect also have certain rules.As the lean angle gradually increases,the ability to inhibit clearance leakage flow increases.The leaned honeycomb tip with a 60° angle of inclination can reduce the tip leakage flow rate by 17.26% relative to the flat tip,meanwhile the energy loss at the outlet section is reduced by 4.35%.Obviously,the clearance leakage flow is well controlled by this kind of blade tip structure. |
