Heat and mass transfer problems for film cooling

In the paper, a review of calculation methods and of experimental results for heat transfer under film cooling is presented. The effects of arrangement of film cooling, longitudinal pressure gradient, nonisothermality and compressibility of the gas, injection of a foreign gas, surface roughness, swirling of flow, and turbulent pulsations of the main gas flow on the effectiveness of film cooling are considered. A generalized correlation for the effectiveness of film cooling, is proposed, which makes it possible to take into account the influence of the above factors. It is shown, that in determination of the heat transfer coefficient in the region of film cooling, it is necessary to take into account the influence of injected gas on the development of the thermal boundary layer. A method of calculation for combined cooling (film, porous or transpiration and convective), which accounts for effect of longitudinal hear conductivity of the wall on the film cooling effectiveness is proposed. An estimation of profile losses on a gas turbine blade is given for the cases of film and porous or transpiration cooling.