Numerical Simulation Of Film Cooling In Slotted Cylindrical Hole

Gas turbines have been playing an important role in aviation,power generation and various industries due to its light and small volume.In order to reduce the surface temperature of turbine blades,vapor film cooling has become one of the most significant cooling methods in the design of the hot end components of modern gas turbines,and the hole type is vital to improve the cooling efficiency of the vapor film.Therefore,it is very important to find the hole with high cooling efficiency and investigate its flow mechanism.Since the computer technology is developing rapidly,the simulation method which requires greater computer hardware,such as large eddy simulation,is gradually applied.It can calculate the internal flow field of the fluid more accurately and reflect the deeper and more detailed structure on the computer,so that the cooling efficiency of the vortex system can be studied in the flow mechanism.In order to get closer to the actual situation,more and more scholars turn to fluid solid coupling research.In this paper,the large eddy simulation and fluid solid coupling method are used to investigate the slotted cylindrical holes,providing effective reference data for engineering practice.The specific research contents are as follows:First of all,large eddy simulation is used to simulate the flow of transverse turbulent jet in a slotted cylindrical hole,which is compared with the vortex structure and heat transfer characteristics of the cylindrical hole flow field under the same working conditions,thus revealing the flow mechanism.The calculation results show that the main stream and the jet are more mixed after the cylindrical hole is slotted,the reverse vortex pair is torsional,and the vortex mechanism is disorganized,and the cooling vapor cannot be lifted,thereby the cooling efficiency is improved.The cooling gas is diffused in the slot due to the function of the cylindrical hole,and comparing with the cylindrical hole,the range of axial cooling is larger.According to the analysis of the vorticity equivalent line,the K-H(Kelvin-Helmholtz)instability changes the velocity direction and size of the mainstream and the secondary flow interface,then affecting the formation of the reverse vortex pair.Secondly,the fluid solid coupling flow mechanism under the combined action of convection and heat conduction is studied.This part is based on the RNG k-ε turbulence model and the SIMPLEC algorithm.The numerical simulation of the slot cylindrical holes is carried out under the coupling condition,and the calculation of the blowing ratio is 1,1.25 and 1.5.The results show that when the blow ratio is 1,the cooling vapor can effectively attach the wall,and its cooling effect is the best.At last,the influence of different thermal conductivity on film cooling and the comparison of temperature distribution when heat insulation and fluid solid coupling heat transfer are investigated with the air blowing ratio of M=1 as the research object.The research shows that comparing with the adiabatic condition,the wall of the coupled heat transfer not only has higher cooling efficiency,but also has wider and even cooling range,which is closer to reality.With the increase of thermal conductivity,the cooling effect of the solid wall area gets better.When a certain value is increased,the cooling efficiency of the whole wall is almost constant,the heat conduction plays the leading role,but it has little effect on the velocity field.