Experimental Investigation on Flow Resistance and Heat Transfer Coefficient of Internal Lamilloy

Abstract

Flow resistance and heat transfer coefficients of the lamilloy with two kinds of film hole pitch were experimentally studied at the impinging Reynolds numbers ranging from 1×104 to 6×104. The detailed distributions of pressure coefficients on the target plate, impingement plate and pin-fins, local loss coefficients of jet, channel flow, effusion and the flow resistance coefficients of lamilloy were obtained by using a lot of pressure taps. The dense grids of the surfaces were generated and the pressure values of all the grid points were obtained by Kriging interpolation method based on the experimental data. Distributions of heat transfer coefficients on the target and the impingement surfaces ( The surface of the impingement plate in the impingement hole outlet surface) were tested by the transient liquid crystal technique. The coolant temperatures of both impingement hole inlet and the film hole outlet were measured by K type thermocouples. The results show that the pressure coefficients on the jet stagnation region increase firstly and then decrease along the radius direction from stagnation point. The pressure distributions on the two rows of pin-fins near the two film hole rows are significantly affected by the Reynolds numbers. The pressure coefficient values are nearly the same in the pin fin height direction which means the flow pattern near the pin fins of this two rows likes the crossflow past a circular cylinder at Re=3×104 and has the characteristics of reverse flow and flow around circular cylinder at Re=4×104. The loss coefficients of effusion are the biggest, those of channel flow are the second and those of impingement jet are the smallest. The loss coefficients of effusion of film hole increase at least 4 times and those of the impingement jet and the channel flow change slightly when the spacing of film hole decreases one half. The averaged heat transfer coefficient of target surface is higher than that of the impingement surface. This difference becomes obvious with the increase of Reynolds number. The differences of Nusselt number on the impingement surface and the target surface are 16% and 10% respectively under the two models at the Reynolds number of 6×104, indicating that the hole pitch has a weak influence on the averaged heat transfer coefficients. The second peak of heat transfer coefficients was found.