Fundamental Scramjet Combustion Experiments using Hydrocarbon Fuel

摘要

Combustion of ethylene was examined experimentally via free-jet testing of a fundamental, axisymmetric combustor model at conditions representative of Mach 7-8 flight at 50 kPa dynamic pressure. The model consisted of diffusor, constant area isolator, cavity and diverging combustor sections. Pressure data were measured along the wall of the model, and were complemented with OH PLIF visualisation at the exit of the diverging section. Robust combustion of ethylene was observed for two stagnation enthalpy cases for equivalence ratios of 0.3 or greater. A low enthalpy, low equivalence ratio case showed significant, but structurally different, OH PLIF signals even though there was little combustion-induced pressure rise. Edge-detection techniques were applied to the PLIF images, and the resulting azimuthal distributions analysed. Mean radii and standard deviations are presented for the inner and outer edges of the OH rich band for four tunnel/fuelling conditions. Finally, amplitude spectra of fluctuations in the edge radii are shown, indicating that low wavenumber oscillations are dominant. These experimental results provide useful data for comparison with numerical simulation in future studies.