Heat Transfer Studies on Gas Turbine Combustor Liner Cooling

Abstract

This study deals with the combination of film cooling techniques in an effusion cooled test plate. Geometrical parameters of the effusion cooling test plate have holes of diameter 1 mm, hole angle of 27° and 7.2 mm pitch in both streamwise and spanwise directions. Effusion holes are placed in a staggered manner with 9 holes per row, and there are 13 rows in total. Experimental and numerical investigation of adiabatic cooling effectiveness and convective heat transfer coefficient on an effusion cooled test plate is carried out with and without machined ring geometries upstream. For these tests, the effusion cooling geometrical parameters are scaled up by 3 times. Tests are carried out at blowing ratio ranging from 0.5 to 2.5, coolant to mainstream density ratio of 1.3 and at a mainstream velocity of 20 m/s. The convective heat transfer coefficient investigations are carried out using a constant heat flux surface with coolant and mainstream at the same temperature. Test plate surface temperature measurements are recorded by an infrared camera. Effusion cooling along with machined ring geometries upstream shows higher adiabatic film cooling effectiveness and higher film heat transfer coefficients than effusion cooling alone at all the blowing ratios. Measurements of overall film cooling effectiveness are also carried out in stainless steel effusion cooling test plate of 2 mm thickness with and without machined ring geometries. This comparison result also shows that the overall cooling effectiveness increases significantly before the effusion cooling holes with the presence of machined ring geometries. Another combination of impingement with effusion cooling is studied for an effusion test plate having a 5.4 mm pitch in both the spanwise and streamwise directions. An impingement plate is kept backside of the effusion plate at a distance of 6 mm. The holes in the impingement plate are arranged in a staggered manner such that each effusion hole is surrounded by four impingement holes. The result shows that the effusion cooling with impingement gives higher overall cooling effectiveness than effusion cooling alone. The comparison is made between effusion cooling with impingement and effusion with machined ring geometries. The result shows that the effusion with machined ring geometries has higher overall cooling effectiveness than effusion cooling with impingement. Numerical analysis is performed using ANSYS workbench, and the methodology is validated against the experimental results. The numerical results are matching with the experimental results and the temperature contours obtained are compared with infrared camera images. A MATLAB program isiii used to obtain the effectiveness contours for both the experimental and numerical results.