Control Of Tip Leakage Flow By Multiple Plasma Actuators Based On Kriging Model

Since aero-engine technology plays an important role in national economic development,infrastructure construction and national defense construction,countries across the world invested a large number of costs and formulated a series of development plans to improve the performance indicators of aero-engine.Because the rotor blades must have a margin space for rotating and thermal expansion in the turbine,tip clearance must exist.However,at the same time,partial fluid will flow through the tip clearance and evolve various complex vortexes,resulting in energy loss of turbines.Therefore,how to reduce the leakage loss under the limited tip clearance height has become a topic of concern to researchers.In this paper,by placing several plasma actuators at the tip of turbine rotor blades,the control effect and control mechanism of the combined plasma on the tip leakage flow were studied based on numerical simulation.Firstly,the sample scheme of different plasma actuator positions was obtained through orthogonal experimental design,and then the leakage flow values were obtained through numerical simulation.Kriging model was built with leakage flow values as the objective function.Then Kriging model was used to find out the optimal scheme.The control mechanism of plasma can be obtained by analyzing the relationship between the arrangement of actuators and the leakage flow,vortex structure and loss distribution.In this paper,the control effect of 15 plasma actuators along the suction edge on leakage flow was studied.Through the comparison between the baseline case and the optimal cases,the leakage flow distribution and flow structures in the clearance were analyzed.The results showed that the plasma actuators located along the suction edge could effectively reduce the low pressure area and reduce the pressure difference between the two sides of the blade.The leakage flow can be reduced by up to 45.9%.At the same time,the plasma actuators would generate induced vortex structures on one side of the suction edge,which prevented the leakage fluid from flowing out of the gap,and effectively consumed the vortex intensity of the separation bubble,prompting its vortex core to move up and disintegrate.The source of mixing loss in the channel and the loss distribution in the outlet of the channel were also discussed.The calculation results showed that the mixing loss between the leakage fluid and the main flow was mainly concentrated in the back part of the cascade,and the difference of momentum in the normal direction of the suction edge was the main reason for the mixing loss.The plasma actuators can effectively reduce the angle and momentum difference between the tip leakage fluid and the main flow,thus reducing the mixing loss,which can be up to about 70%.In addition,the plasma actuators can significantly weaken the strength of the leakage vortex,restrict the development of the leakage vortex,and promote the upper passage vortex to squeeze tip leakage vortex to move towards the tip of blade,thus reducing the energy loss at the cascade outlet section by up to 15.72%.Furthermore,the arrangement of plasma actuators arrays along the suction edge of blade tip,the middle arc and the middle line of both were proposed in this paper.The control effect of the optimal case under the inlet velocity of 10 m/s and 20 m/s was also discussed.The results showed that when flow velocity was 10 m/s,the plasma arrays can generate multiple induced vortexes,which made the effect of leakage vortex flow field almost disappeared.In addition,the distribution of upper and lower passage vortexes in the outlet of cascade was almost symmetrical.Therefore,the plasma array can further hinder the tip leakage flow.When the inlet velocity was 20 m/s,compared with the baseline case,the leakage flow of the optimal array arrangement case decreased by 11.59%,the average mixing loss decreased by about 15.1%,and the average energy loss coefficient of the outlet also decreased by 4.7%,which showed that the plasma actuators can also control the tip leakage flow well under the inlet velocity of 20 m/s.