An Experiment on Ignition in a Rectangular Corss Section Scramjet Combustor

Autoignition and plasma-torch forced-ignition of hydrogen in a scramjet combustor were examined using a direct-connect test apparatus with various fuel injection patterns. Ignition behavior fell into three distinct categories, separated by the three bounding curves on an air temperature-fuel flow rate plane. The lowest boundary was independent of fuel injection patterns, while the other boundaries significantly depended on these patterns. Compared with injection from a single orifice, injection from multiple orifices appreciably enhanced autoignition, because fuel jets from adjacent orifices and from those on the opposite wall tended to attenuate the local flame quenching. A new plasma torch with a feed stock of air or oxygen was developed, which is desirable for a spaceplane from the viewpoint of total system design. The new plasma torch with air or oxygen stably operated without argon as a support gas. It was shown that the effectiveness of an air or oxygen plasma torch was comparable to that of a nitorogen or argon-hydrogen plasma torch, with the exception of an argon-hydrogen plasma torch in single-wall injection. A single plasma torch on a wall was able to ignite all the fuel jets injected from the same wall, but failed to ignite those from the opposite wall.