Planar laser-induced fluorescence images of fuel mixing and the reaction zone in a supersonic combustor.

The mixing of fuel and air and the structure of the chemical reaction zone were studied experimentally in a supersonic combustor. Planar images of laser induced fluorescence (PLIF) of acetone seeded into the fuel flow and OH produced in the reaction zone were acquired for two supersonic flame conditions. The PLIF images of acetone show that the fuel and co-flow air experience significant mixing due to the extremely strong recirculation zones which are generated by the supersonic co-flow air and the bluff body geometry. The OH images show that the supersonic flame structure is very different from the subsonic flame structure for the same burner geometry. OH exists as a continuous diffuse region throughout the supersonic flame with distinct OH production regions observed beyond 25 jet diameters. An extensive calibration of the acetone laser induced fluorescence (LIF) technique was conducted in order to properly interpret the LIF signals. The effects of pressure and temperature on the LIF signal were found to be negligible over pressures ranging from 0.1-1.0 atm and temperatures ranging from 240-300 K, which are characteristic of the non-reacting supersonic flow. The first calibration of acetone LIF in a flame environment was conducted by measuring acetone LIF and temperature at identical locations in a laminar non-premixed flame. Five different profiles of acetone LIF and five profiles of gas temperature were found to collapse to a single calibration curve. The results show that the acetone LIF signal can be used to determine the temperature and the mixture fraction in the fuel rich portion of a flame for temperatures up to 1400 K with acceptable accuracy.Ph.D.Aerospace engineeringApplied SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/130908/2/9825174.pd