This experimental investigation involved the study of gas film cooling from a single row of spanwise angled holes using the stagnation region of a cylinder in cross flow to model the leading edge of a turbine vane. The objective was to obtain data for the local convective heat transfer rates to a highly cooled, curved surface exposed to a turbulent hot mainstream flow and a secondary, film coolant flow. Since the leading edge of the first stage, inlet turbine vane experiences some of the most severe thermal loads found in the turbine engine, effective film cooling is most important in this area. Film cooling of the leading edge area was modeled by making heat transfer measurements on the front stagnation region of a cylinder in cross flow. Experiments were conducted in a rectangular duct using a film cooled cylindrical test surface normal to a two-dimensional freestream flow. A gas turbine combustor provided heated air flow to simulate a Reynolds number typical of a high pressure, high temperature turbine vane. Internal convection cooling of the cylinder allowed a gas-to-wall temperature ratio of 2.1 to be achieved while using a moderate freestream gas temperature (1000R; 555K. The film coolant was chilled to obtain a coolant-to-freestream density ratio of 2.2, representative of the gas turbine environment. The cylindrical test surface was instrumented with miniature heat flux gages, and wall thermocouples to determine the influence of the film coolant blowing ratio and the injection hole geometry on the film cooling performance.

Wall cooling effectiveness is investigated for tangential, inclined, and normal injection of coolant through single or multiple wall slots into a laminar compressible boundary layer. Numerical solutions of the boundary layer equations are obtained by a reliable finite difference method. A grid control procedure which maintains a constant flow rate between grid lines is applied to the injection calculations wherein the boundary layer growth in the slot is as much as hundred-fold and the longitudinal component of the injection velocity is in some cases as large as the free stream velocity. Film cooling effectiveness is reported for a variety of injection configurations so that the effects of injection angle, coolant mass flow rate, Mach number, upstream boundary layer thickness, slot width, and the presence of upstream cooling slots can be investigated.