Mitigation of Heat Release from Film Cooling in Fuel-Rich Environments

摘要

A result of higher combustor temperatures and pressures is the potential for unconsumed radical species or fuel-rich gas to enter the turbine. When these gases encounter the cool, oxygen-rich cooling air, the potential for a secondary reaction and subsequent augmented heat transfer to the airfoil arises. Depending on the goal of the cooling-flow designer, two different mitigation strategies were proposed and investigated in this effort. The first set of cooling arrangements of holes was conceived with the objective to quickly consume the fuel-rich radicals and decrease the reaction zone size. The tradeoff with these concepts was that the local heat load to the airfoil was expected to be enhanced. The second set of configurations aimed to buffer the reactions off the wall and thus reduce the local augmentation of heat load to the wall. The drawback to these schemes was that the fuel-rich species would not be completely consumed, thus resulting in the potential for further reactions downstream. In addition to heat-flux measurements on the film-cooled surface, the location and length of the flame were recorded using visual photography. Results were evaluated based on net heat-flux reduction, which accounted for how well a given scheme protected the wall from the additional heat released from reactions. Although no one scheme was expected to excel at both of these goals, a scheme was identified to accomplish each independent goal.