Effect Of Pin-fins Combined With Dimple And Protrusion Structure On The Cooling Effeciency Of Turbine Blade Trailing Edge

Society is progressing and science is developing.With the rise of human civilization,gas turbines can be seen everywhere.In this era of pursuing efficiency,gas turbines are facing huge challenges and have been progressing in improving efficiency.People from all walks of life have been striving for high-efficiency turbines,and improving the temperature of the turbine inlet mass is one of the main methods to improve the function of turbines.Nowadays,The maximum temperatures that blades can now be made from are far below those of the gas turbine’s inlet working fluid,so many cooling methods have been born,and air film cooling is one of them.The structural characteristics of the trailing edge of the blade are weak,and the pressure it bears is large,so the cooling difficulty becomes correspondingly large.the appropriate cooling method can not only improve the cooling effect of this stage blade,but also can improve the working environment of the next stage blade,to improve the efficiency of the purpose,so there are a lot of blade trailing edge cooling investigation.In this paper,we adopt the structure of pin-fins to strengthen the disturbance in the flow process and increase the effective area in the heat transfer process,and also strengthen the role of the blade,and then add the dimple and protrusion structure in the gap of the staggered row of pin-fins to investigate the flow and heat transfer of the cooling mass by numerical simulation,and research the role of the dimple and protrusion structure in the cooling of the trailing edge of the blade.In this paper,the dimple and protrusion structures are arranged simultaneously on the pressure and suction surfaces between the pin-fins at the trailing edge of the blade,and four new structures are obtained in each of the tapering and parallel channels,which break the mode of making structural changes only on the shape of the pin-fins or only on the suction surface in previous studies.The geometric model in the study was established by using UG12.0 software,after which the grid was divided by using ICEM software.To ensure the feasibility of the simulation,gridindependent verification and turbulence model verification were carried out,and finally,the turbulence model suitable for the number of grids and the approach the experimental results was gained,i.e.,DES.This study mainly focuses on the flow and heat transfer of the flow field to obtained the effect of the dimple and protrusion structure on the cooling effect.For the tapering channel,the flow characteristics under different blowing ratios are explored,and it is found that the local high pressure and local low zone pressure areas on the pressure surfaces and suction surfaces increase in the new structure.In studying the heat transfer characteristics of each structure,the dimple and protrusion structure improves the cooling efficiency on the suction surface downstream of the splitting slit exit to a certain extent,but is influenced by the blowing ratio in the process.When the blowing ratio is small,the cold fluid velocity is small and the flow is smooth,and the perturbation effect of the dimple and protrusion structure is small;when the blowing ratio is large,the cold fluid velocity is large and the flow is violent,and the perturbation effect of the dimple and protrusion structure fails.During the study,it was found that the blowing ratio of 0.8 best reflects the characteristics of the dimple and protrusion structure,at which time the cooling efficiency of the new structure is significantly greater than that of the original structure after X/H>4.2 along the airflow direction,and the protrusion-protrusion structure performs best after X/H>6.5,with a maximum cooling efficiency improvement of 13.86% at X/H=11.96.The parallel channel itself does not have convergence characteristics,so the cooling fluid flow in the channel is smoother,and even if the dimple and protrusion structure is added,the effect on the downstream temperature of the splitting slit exit is relatively small,and the isotherm only produces weak fluctuations after X/H>10.Unlike the tapering channel,the general heat transfer effect of the improved parallel channel is greater than that of the original structure,and the full mixing position of the high temperature mainstream and cooling incoming flow in the parallel channel extends downstream compared to the tapering channel.The new structure increases the cooling efficiency while also increasing the flow resistance in the pin-fins part.The protrusion-protrusion structure corresponds to the maximum flow resistance by reducing the fluid flow area,and this phenomenon is more obvious in the tapering channel.Both in the tapering channel and in the parallel channel,the pressure surface is protrusion and the suction surface is dimple(i.e.,protrusion-dimple structure),which has the best overall heat transfer effect because of its larger Nussle number and smaller flow resistance.