Chemical Kinetics and Self-Ignition in A Model Supersonic Hydrogen-Air Combustor

Authors: C. J. Sung, J. G. Li, G. Yu, and C. K. Law

Direct link to the paper: DOI: 10.2514/2.715


Self-ignition tests of a model scramjet combustor were conducted by using parallel sonic injection of gaseous hydrogen from the base of a blade-like strut into a supersonic vitiated airstream. The range of stagnation pressure and temperature studied varied from 1.0 to 4.5 MPa and from 1300 to 2200 K, respectively. Experimental results show that the self-ignition limit, in terms of either global or local quantities of pressure and temperature, exhibits a nonmonotonic behavior resembling the classical homogeneous explosion limit of the hydrogen– oxygen system. SpeciŽ cally, for a given temperature, increasing pressure from a low value can render a nonignitable mixture torst become ignitable, then nonignitable again. This correspondence shows that, despite the globally supersonic nonpremixed conŽ guration studied herein, ignition is strongly in uenced by the intricate chemical reaction mech-anism and thereby exhibits the homogeneous explosion character . Consequently, self-ignition criteria based on a global reaction rate approximating the complex chemistry are inadequate. An auxiliary computational study on counter ow ignition was also conducted to systematically investigate the contamination effects of vitiated air . Re-sults indicate that the net contamination effects for the present experimental data are expected to be substantially smaller than contributions from the individual contamination species because of the counterbalancing in uences of the H2 O-inhibition and NO-promotion reactions in effecting ignition.

Citation: C. J. Sung, J. G. Li, G. Yu, and C. K. Law, “Chemical Kinetics and Self-Ignition in A Model Supersonic Hydrogen-Air Combustor,” AIAA Journal 37 (2), 208-214 (1999).