An experimental study of a generic supersonic combustor.

The overall objectives of the present study were to measure the general properties of a hydrogen jet flame in a supersonic air stream, and to compare the supersonic results to subsonic trends and a one-dimensional analysis. The general properties measured were blowout stability limits, heat release distributions, thermal choking limits, stagnation pressure loss, static pressure profiles, and $\rm NO\sb{x}$ emission index. While supersonic flame properties were of primary interest, subsonic flame blowout limits and $\rm NO\sb{x}$ levels also were measured for comparison. A supersonic (Mach 2.2) combustor was designed which provided a wide range of conditions, including stagnation temperature from 294 K to the autoignition temperature of 900 K. It was found that the flame blowout curves display two distinct stable regions which are bounded by the far-field blowout limit and near-field blowout limit. Supersonic flame stability requires fuel tube lip thickness and sufficient stagnation temperature to extend the near-field blowout limit curve into the supersonic regime. It was determined from the data and a one-dimensional analysis that a supersonic flame has a heat release distribution with a log-normal shape. Using this log-normal shape, the one-dimensional supersonic analysis does adequately predict the measured loss of stagnation pressure and the amount of heat addition that causes the onset of thermal choking. Measurements quantify the wall divergence half angle that is required to avoid thermal choking. The $\rm NO\sb{x}$ emission index was measured for numerous subsonic and supersonic cases. In the subsonic cases, the global residence time and the deviations from chemical equilibrium (i.e. the Damkohler number) were varied and the resulting effects were compared with the thermal $\rm NO\sb{x}$ theory. In particular, a unique jet flame was studied that is composed of helium-diluted hydrogen fuel, and the $\rm NO\sb{x}$ data of this helium-diluted hydrogen flame was found to be correlated successfully by the use of a Damkohler number. In the supersonic cases, the global residence time was varied for a hydrogen jet diffusion flame and it was found that the measured $\rm NO\sb{x}$ emission index data increased with the global residence time, which is the same trend as that observed in the subsonic cases.PhDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/104229/1/9501073.pdfDescription of 9501073.pdf : Restricted to UM users only