MEASURED SUPERSONIC FLAME PROPERTIES - HEAT-RELEASE PATTERNS, PRESSURE LOSSES, THERMAL CHOKING LIMITS

Some general properties of a research-scale supersonic combustion devi ce are reported and compared to a simple one dimensional analysis of s upersonic how with heat addition and area change, The properties that were measured include the stagnation pressure losses because of combus tion, the static pressure axial profiles, and the thermal choking limi ts; the heat release pattern was inferred from these measurements, A s imple combustor geometry was chosen that consists of a hydrogen-air tu rbulent jet flame that is stabilized along the axis of a supersonic (M ach 2.2) airflow within a diverging duct, It was found that the heat-r elease pattern (in kilowatts per centimeter of axial distance) is not uniform in space, but varies in a lognormal manner in the axial direct ion for the supersonic jet flame, which differs from the Gaussian patt ern that characterizes a subsonic jet flame. The difference is attribu ted to earlier air entrainment and combustion caused by the supersonic coflowing air. It was found that it is possible to adequately estimat e the measured stagnation pressure loss and the thermal choking limits using a one-dimensional analysis, if the measured lognormal shape of the heat release pattern is used. Measurements also quantify the wall divergence angle that is required to avoid thermal choking.