KSEF RDE: Flame Stabilization by Autoignition in Non-homogeneous Mixtures For Clean Combustion

Modern gas-turbine engines for electricity generation and aerospace power are under increasing regulation to reduce pollutant emissions. One method to improve efficiency and reduce emissions is to increase the operating pressure. A second method to reduce emissions is to distribute the heat release throughout the combustor by staging the fuel injection such that lower peak temperatures are achieved. Both methods have been implemented by engine manufacturers; however, these conditions have led to key differences that change the nature of flame stabilization. Continued improvement in engine designs requires a fundamental understanding of these differences. First, the staging of fuel leads to significant variations in the fuel/air mixture throughout the combustor. Second, the temperatures of gas where fuel is injected is higher than in previous designs. Under these conditions flame stabilization can occur by autoignition of the injected fuel as it mixes with the surrounding hot gases. In previous designs, flames would be stabilized by flame propagation or pilot flames, and this stabilization could be intentionally located by the design of the fuel injector. In the new designs, the flame can stabilize by igniting wherever the mixture composition and temperature are suitable. This leads to larger uncertainty in engine operation. Prior work on autoignition has focused almost exclusively on uniform mixtures. The conditions that lead to autoignition when there are large gradients in the fuel/air mixture and the temperature are not understood. The PI has begun developing a combustor that can stabilize flames by autoignition with gradients in mixture and temperature. This seed funding will complete the development of this experiment and provide preliminary data on flame stabilization by combining a variety of laser diagnostics available in the PI's lab. This work is expected to lead to proposals for funding from NSF, DOD, DOE, and NASA.