Long autoignition delay time and low lateral flame propagation speed are among the key problems in developing high-speed combustors for ram/scramjet engines. Plasma-assisted combustion can help to solve these problems. Estimates indicate that uniform volumetric nonequilibrium cold plasma ignition of fuel-air mixtures in ram/scramjet combustors can require large amounts of power to be deposited into the flow. In this paper, we explore a possibility of using microwaves for increase of flame propagation speed, which would be complementary to plasma ignition, allowing the latter to be applied to a smaller volume. The results suggest that the flame propagation speed strongly depends on the Q of the microwave cavity. For high values of Q (1000), the input microwave power requirement decreases sharply from kilowatts to hundreds of watts. A 20% increase in the premixed methane-air flame propagation speed was observed for 400 Watt of input microwave power which was operating at 2.45 GHz. It was found that the power absorbed by the flame increases with the increase in the input subcritical microwave power.Theoretical estimations suggest that a small amount of power (on the order 10 W) was absorbed in the flame. These theoretical estimates support the observed experimental data. Copyright 2005 by Princeton University.
author list (cited authors)
Zaidi, S., Qin, X., Macheret, S., Ju, Y., Miles, R., Sullivan, D., & Evans, M.
