Experimental study of inclined jets cross flow interaction in compressibleregime. II. Effect of injection rate on surface heat transfer.

An experimental study of a row of jets entering in a transonic mainstream ( M = 0.72) is carried out in order to investigate the influence of the injec tion rate, defined as the ratio of the mass fluxes per unit surface of the jet to the cross flow fluids, on the interaction of the two flows and on th e wall heat transfer. The velocity field is derived from total pressure and temperature measurements. Infrared thermography technique is used to ident ify the wall surface heat transfer. Experiments are carried out for three v alues of the injection rate R = 0.24, 0.37 and 0.50. The experiments indica te the existence of an optimum film effectiveness for a value of R close to 0.37. A higher injection rate leads to a higher penetration of the jet in the cross flow with an associated reduction of the film cooling effect due to the injection of cross flow fluid under the jets. A lower injection rate induces a higher mixing of the jet fluid with the incoming boundary layer flow which also reduces the film efficiency. (C) 2000 Editions scientifique s et medicales Elsevier SAS.