Impact of Heat Release in Turbine Film Cooling

Abstract

The Ultra Compact Combustor is a design that integrates a turbine vane into the combustor flow path. Because of the high fuel-to-air ratio and short combustor flow path, a significant potential exists for unburned fuel to enter the turbine. Using contemporary turbine cooling vane designs, the injection of oxygen-rich turbine cooling air into a combustor flow containing unburned fuel could result in heat release in the turbine and a large decrease in cooling effectiveness. The current study explores the interaction of cooling flow from typical cooling holes with the exhaust of a fuel-rich well-stirred-reactor operating at high temperatures over a flat plate. Surface temperatures, heat flux, and heat transfer coefficients are calculated for a variety of reactor fuel-to-air ratios, cooling hole geometries, and blowing ratios. Results demonstrate that reactions in the turbine cooling film can result in increased heat transfer to the surface. The amount of this increase depends on hole geometry and blowing ratio and fuel content of the combustor flow.Failure to design for this effect could result in augmented heat transfer caused by the cooling scheme, and turbine life could be degraded substantially.

Chemiluminescence and High Speed Imaging of Reacting Film Cooling Layers

“…C and are calculated using the two temperatures, T 1 and T 2 , provided by the thermocouples. (18) Setting Eqs. 17 and 18 equal and solving for provides an equation for the heat flux.…”

“…The two toroidal sections sandwich the jet ring and form a 250 ml internal reactor volume. Inside the reactor the fuel-air mixture react and exits through a continuous circumferential exhaust port located in the center of the reactor, which is in contrast to the discrete exhaust holes used by Evans (18). The port leads to a common exhaust section directing the flow upward to the test section.…”

“…The test rig was designed by Evans (18). It is comprised of a transition section, a test section, two cooling air assemblies, four heat transfer gauge assemblies, a window assembly, and an aft plate.…”

“…The design process and geometry is described in detail in Ref. (18). assembly is inserted into a stainless steel flange pipe and is then mounted on a plate which helps in supporting the test rig above the WSR.…”

“…The springs also accommodate any thermal expansion of the transition section. References (18) and (19) provide further images and details on the transition section design and mounting method.…”