Research On Flow And Heat Transfer Of Impingement Cooling In Turbine Blade Leading Edge With Crossflow

The turbine inlet temperature in modern aircraft engine/gas turbine has be gradually increasing to obtain higher thermal efficiency.However,as the turbine inlet temperature increases,the heat transferred to the turbine blades increases,which will increase the thermal stress and cause great damage to the blades.In order to improve the service life of the blades and ensure safe operation,advanced blade cooling technology is employed to reduce the temperature of the turbine blade,which has become the focus of the current turbine engine development.The jet impingement cooling can efficiently cool areas with high temperature using various cooling technologies,which is often used in the cooling of the leading edge of turbine blades.Due to the limit of jet flow structure and stagnation region area,the research is relatively difficult and few works have been done.At present,the research on impingement cooling of blade leading edge is gradually developed to refinement and enhanced heat transfer technique.In this paper,the impingement cooling structure in the blade leading edge of the first stage turbine is chosen.The effects of the jet Reynolds number,the jet nozzle position,the jet channel rotation,and the target surface with film hole are studied through experimental measurement and numerical simulation.The vortex generators(VG)are used to suppress the negative effect of cross flow on jet impingement to enhance the impingement heat transfer on the target surface,and the mechanism of the impingement heat transfer enhancement is analyzed.In addition,the mechanism of unsteady flow and heat transfer in jet impingement channel is also explored.The research results can provide a theoretical guidance for designing high-performance blade impingement cooling structure.Following are the main work and findings of this research thesis:1.A single-row jet impingement test platform and a single-hole with a crossflow jet impingement test platform have been built and set up.Based on the assumption of onedimensional transient conduction over a semi-infinite plate,the transient liquid crystal technique is used to measure the heat transfer coefficient on the concave target surface.2.The effects of jet nozzle position under different jet Reynolds numbers(Rej=12000,15000 and 20000)are investigated using the experimental and numerical methods.The influence of jet nozzle position on heat transfer on the target surface is quantitatively analyzed,and the mechanism of the heat transfer enhancement on the target surface is revealed.Considering that the impingement cooling in the turbine blade leading edge is affected by the rotation and film cooling extraction,the effects of the jet channel rotation and the target surface with film hole are also studied numerically.3.The influence of the vortex generator(VG)placed in the channel upstream of the jet exit on the top wall is studied using experimental and numerical methods.Based on that,the effects of the VG placement angle,the VG placement position,the VG height,the cross flow Reynolds number and the shape of the VG are investigated.In addition,the mechanism of heat transfer enhancement by the VG is also revealed.4.The unsteady flow and heat transfer characteristics in impingement channel of the blade leading edge are analyzed by using the k-? SST-DES method.The mechanism of unsteady heat transfer on the target surface caused by instability of the flow field is revealed.Based on the numerical results,the unsteady heat transfer characteristics in the jet channel is further studied by both POD and DMD which are two main mode decomposition methods.