Investigation On The Influence Of A Seal Whisker Bionic Trailing Edge On The Aerodynamic And Cooling Performance Of Turbine Blades

The performance requirements of modern gas turbines are constantly increasing.It is necessary to improve cooling technology to adapt to the increase of turbine inlet temperature.On the other hand,the flow control method can be used to reduce aerodynamic losses in gas turbines.The trailing edge loss of turbine blades is an important component of blade profile loss and also an important area for blade cooling.The vortex shedding from the blade trailing edge is an important source of unsteady losses in the turbine cascade,and the vortex shedding from the cutback lip of the pressure-side cutback cooling blade causes a sharp decrease of the film cooling effectiveness on the cutback surface.Therefore,it is necessary to introduce effective flow control methods and innovative trailing edge design to control trailing edge shedding vortices and improve turbine efficiency.This article uses the seal whisker structure as a flow control method and applies the seal whisker biomimetic structure to the trailing edge and the cutback lip of turbine blades to reduce trailing edge loss and improve the film cooling effectiveness of pressure-side cutback cooling blades.The control mechanism of the seal whisker structure on the shedding vortex of turbine blade trailing edges is revealed by using Delayed Detached Eddy Simulation and Large Eddy Simulation methods.Finally,the biomimetic trailing edge design scheme of the pressure-side cutback cooling blade is explored by considering both the aerodynamic and cooling performance.Firstly,a biomimetic trailing edge blade generation method is proposed for uncooled high-pressure turbine blades.Delayed Detached Eddy Simulation method was used to study the flow inside the cascade of the seal whisker biomimetic trailing edge blade.The results show that the biomimetic blade can achieve the best aerodynamic performance when the isentropic Mach number at the cascade outlet is within the range of 0.38 to 0.9.The biomimetic trailing edge breaks Karmen vortex street structures in the wake,transforming the shedding vortex into small vortices with a three-dimensional spatial structure,greatly reducing the mixing loss in the wake.As the wake moves downstream,the vortices rapidly dissipate into smaller vortices,resulting in a significant narrowing of the wake area width and faster wake recovery.Under supersonic conditions,the biomimetic trailing edge suppresses the dynamic motion of the shock waves.Secondly,the seal whisker structure is applied to the trailing edges of the vane and the blade of the uncooled turbine stage.The differences between the prototype and the biomimetic turbine stages in aerodynamic losses,the turbine stage vane’s wake migration,and vane-blade interaction were studied using Delayed Detached Eddy Simulation and entropy analysis methods.Research has shown that the bionic trailing edge reduces the energy loss coefficients of the vane domain and the blade domain by 0.94% and 1.53%,respectively,and increases the turbine stage efficiency by 2.09%.The mechanism that the wake of the prototype vane gradually widens during downstream transportation is the increase of the surrounding vortex region and the pursuit of the vortices.The bionic trailing edge significantly reduces the wake width of the vane,the interaction time between the core area of the vane wake and the leading edge of the blade,and the secondary flow in the passage of the rotor blade.The biomimetic trailing edge significantly weakens the pressure fluctuation amplitude and high-frequency pressure pulsation at the leading edge of the blade and suppresses the velocity oscillation in the near-wall region of the blade.Thirdly,the thermal mixing process of the trailing edge cutback cooling unit was studied using Large Eddy Simulation and modal analysis methods.Then,the application of the seal whisker structure on the cutback lip of the pressure-side cutback cooling unit was explored.The results indicate that the flow field of trailing edge cutback cooling consists of three main vortex structures: the lip vortex,the streamwise vortex,and the cooling vortex.The lip vortex dominates the temperature dynamics in the middle of the cutback surface,while the temperature dynamics in the rear of the cutback surface are dominated by the streamwise vortex near the wall.The seal whisker bionic lip case-3achieved the best film cooling effectiveness under moderate blowing ratio(0.7-0.9)conditions.The bionic lip reduces the mixing between mainstream high-temperature gas and cooling gas.The boundary layer analysis shows that the bionic lip makes the boundary layer migrate laterally before separation,resulting in the uneven distribution of the film cooling effectiveness on the cutback surface in the transverse direction.Finally,Delayed Detached Eddy Simulation method was used to study the effects of the biomimetic lip and the biomimetic tailing edge structure on the aerodynamic and cooling performance of the pressure-side cutback cooling blades.The contribution of the biomimetic lip and the biomimetic trailing edge to the reduction of losses in pressure side cutback cooling biomimetic blades is evaluated.Then,the phase difference between the cutback lip and trailing edge control curves was studied,as well as the impact of asymmetric trailing edge design on aerodynamic and cooling performance.The design scheme of the cutback lip’s and the trailing edge’s sine control curve peak at the same blade height achieved the best aerodynamic performance,reducing the thermal energy loss coefficient of the prototype by 0.98% and 0.99% respectively under the conditions of mass flow ratio of 0.5% and 1%.In addition,the bionic blade significantly increases the spanwise-averaged adiabatic film cooling effectiveness of the cutback surface.Increasing the amplitude of the suction side control curve increases the instability of the wake,weakening the spanwise constraint effect of the biomimetic blade on the wake.