Investigation of Combustion Characteristics in a Kerosene-Fueled Supersonic Combustor with Air Throttling

The paper presents the results of an experimental and numerical study on the combustion characteristics of a supersonic combustor operation enhanced by pilot hydrogen and air throttling, including ignition and combustion. Wall pressure measurements, schlieren images, and hydroxyl-radical planar-laser-induced-fluorescence (OH-PLIF) are used to obtain information on the flowfield and flame development. With the aid of air throttling, the kerosene is ignited by the pilot flame; and the kerosene flame remains stable even after the pilot hydrogen is switched off. The speed of the shock train generated by the throttling air and combustion is about 52 m/s in the expansion section but only about 3.7 m/s in the cavity region. The stable flame and flame blowout cases can be separated by a curve in a plot of the coexistence time of pilot hydrogen and throttling air versus the air throttling flux ratio. There is a special case lying on this curve for which the flame is unstable and will be blown out before the throttling air is switched off. It is also found that the position of the thermal throat is the same for all the subsonic combustion cases: about 595 mm downstream of the scramjet entrance.