Experimental study of full coverage film cooling optimization

Abstract

Film cooling technique is often used to protect combustion and turbine walls of turbojet engine. The general principle is to inject cooling air coming from compressor, through drilled holes. This air flow provides a cold layer between the hot gases and the walls. In the present study, the effects of rows of holes number on the formation of cooling layer are experimentally investigated. Experiments were carried out on a wall with inclined staggered injection holes. Results indicate that it is necessary to have at least four rows of injection holes to form a cold layer. However, the latter fades away quickly after the last row of holes. So, the second part of the study concerns the influence if new rows of holes over the maintaining of the film. The addition of only one row of holes shows that its effect is independent of the additional row position. The addition of three rows of holes improves Nusselt number and adiabatic effectiveness values. The inter-rows distance also plays an important role. Among the additional injection patterns, a better cooling is noticed for the one with smaller inter-rows distance. © Published under licence by IOP Publishing Ltd.