Research On The Effects Of Dimples And Protrusions On Flow And Heat Transfer In Matrix Cooling Channels In Turbine Blades

Nowadays,gas turbine engines play an indispensable role in modern industry,which have been widely used especially in the aviation,marine and energy fields.The turbine inlet temper-ature is one of the most important factors that influences the performance of the turbine engine.It’s acknowledged that the higher turbine inlet temperatures contribute to the overall gas turbine engine efficiency.Since the turbine inlet temperature has exceeded the melting point of the material of the turbine blade,the internal cooling technology of turbine blades is of vital im-portance,which can ensure its safe and normal function.This paper mainly studies the flow and heat transfer mechanism in matrix cooling channels of the turbine blades by numerical simulation and experiment methods.Meanwhile,the opti-mized structures have been made and tested.The main results and conclusions are as follows:1.The low speed wind tunnel experiment system has been designed and built.The transi-ent liquid crystal technique has been used in the experiment to measure the heat transfer per-formance of different kinds of matrix cooling structures.The Nusselt number distribution of cooling channels is obtained when Reynolds number is equal to 16000³0000.The experi-mental data is shown to prove that the numerical simulation methods are reasonable and ac-ceptable.2.Pro/ENGINEER is used to establish geometric model and ICEM CFD is employed to generate the structured mesh,which can make sure the high quality and enough refinement of the grids.The commercial code ANSYS Fluent is used.Besides,Large eddy simulation is em-ployed under Re=30000,50000 and 80000 to calculate the simplified and enlarged models and obtain the flow field and heat transfer characteristics in matrix cooling channels.According to the analyses of the flow field,pressure loss and heat transfer,it can be concluded that the airflow impinges on the wall in the turning area which can enhance the heat transfer in these regions.When the air flows into the turning structure,it is forced to rotate through 90 degrees and the flow direction is changed.The secondary flow forms and mixes with the main flow,which can also contribute to the heat transfer enhancement.3.The original model has been optimized with the dimple and protrusion structure,which improves heat transfer performance as well as the thermal performance factor（TPF）on condi-tion that the pressure loss increases slightly.15 optimized structures have been calculated under Re=100000⁸0000.A comparison between the CFD results and the experimental data is made.Note that the heat transfer performance is much better when the ratio of the dimple depth and the dimple diameter is equal to 0.3,compared with the ratio of 0.1 and 0.2 cases.The cases with two sides dimples have better heat transfer performance than the cases with one side dimples.In terms of the cases with two sides dimples,the heat transfer can be enhanced by increasing the number of the dimples.In addition,the heat transfer performance is the best when both of dimples and protrusions are applied.Nu/Nu₀ and TPF increase by up to approximately 8%and5%respectively.