Study On Impingement Jet Cooling In Gas Turbine Combustor Liner

The flame temperature in the combustor of a gas turbine is usually as high as 2000 K,while the maximum temperature that can be endured by metal materials is less than 1200 K at present.Therefore,various protective and cooling measures are needed to ensure the operation life of the liner wall which wraps the flame.The traditional combustor liner with film cooling requires a good deal of air.In order to meet the increasingly stringent emission requirements,lean premixed combustor has attracted more attention.Lean premixed combustor require more air for premixed combustion and less air for cooling and dilution.According to the characteristics of lean premixed combustor,the film cooling structure of in the liner of a can annular combustor was transformed to impingement jet cooling strucuture.Based on this structure,a preliminary design method of impingement jet cooling liner is proposed,which is used to determine the diameter of impingement jet holes and dilution holes.In addition,a method for calculating the wall temperature of the liner is presented to verify the feasibility of designing the liner with impingement jet cooling.In order to obtain a better impingement jet cooling structure,this thesis studies the impingement jet cooling structure which is inline with vertical circular holes of equal diameter under the condition of single outlet.The structural variables studied include jet hole diameter D,impinging distance Z,jet hole length(jet plate thickness)t,and hole spacing X.In this thesis,the significance of each parameter to the average heat transfer coefficient h on the target surface was determined by orthogonal test.Among them,X/D has a significant impact on h due to the change of cooling air flow rate,Z has a noticeable impact on h,D has a certain degree of impact on h,and t has a negligible impact on h.In this thesis,the influence trends of parameters Z and D on h at X/D=10 and X/D=8 are studied respectively by means of regression orthogonal experiment,and the optimal values of Z and D within the research range are found.In order to observe the effect of impingement jet cooling on real combusor,this thesis use CFD method to simulate the can annular combustor with impingement jet cooling.The results show that the nonuniformity of internal flow field and temperature field in the liner results that the effect of uniform array impingement jet cooling is inadequate.Given that,in the process of liner design,the distribution of the flame in the liner should be considered,more or bigger jet hole should be arranged on the region where the convective heat transfer in the liner is high.