Spark Ignition of Liquid Kerosene in Scramjet Combustor Equipped with Partly-Covered Cavity

The ignition of room temperature kerosene via a spark plug was investigated by direct-connect facility experiments with a flight condition of M = 4.5. A partly covered cavity is installed in the scramjet combustor model to assist spark ignition of the liquid kerosene injection. The main factors affecting the ignition and flame expansion process, including the direct-injection pressure inside the partly covered cavity, the upstream-injection pressure, and the length of the baffle, were investigated with plenty of experiment results. The flame propagation process was analyzed via wall pressure distribution and thrust. The experiment results indicated that the pressure of the direct injection and the length of the baffle were key factors for the emergence of the weak combustion inside the partly covered cavity. The upstream injection could assist spark ignition inside the partly covered cavity and broaden the direct-injection pressure range that is suitable for ignition. Moreover, upstream injection can stimulate the propagation of the weak combustion to ignite the whole combustor. Fuel distribution near the shear layer of the partly covered cavity was indicated to be the key factor in this propagation process.