Underexpanded Hydrogen Jets Research Articles

Numerical modeling of supersonic-flow deceleration in a two-dimensional duct in combustion of wall tangential hydrogen jets

Results are presented of a numerical modeling of the ignition and combustion of underexpanded turbulent hydrogen jets injected into supersonic air flow (M=2.63) along the walls of a two-dimensional duct. Calculations were performed by numerical integration of reduced Navier-Stokes equations using the method of global iterations. The kinetic mechanism of hydrogen combustion in air involved 13 reactions. In the calculations the duct height was varied. In a fairly narrow duct, the static pressure increased with flow deceleration to subsonic velocities due to ignition and combustion. The influence of combustion on the pressure distribution in the transverse direction is ambiguous. Initially, combustion increases the pressure nonuniformity (a new oblique shock wave occurs), while, downstream, the pressure profile is flattened out due to the appearance of a subsonic layer near the flame front.

Effects of combustion on the interaction of an underexpanded wall hydrogen jet with a supersonic flow in a planar channel

Effects of combustion on the interaction of an underexpanded wall hydrogen jet with a supersonic flow in a planar channel

Three-dimensional calculations of supersonic reacting flows using an LU scheme

A new three-dimensional numerical program that incorporates comprehensive real gas property models has been developed to simulate supersonic reacting flows. The code employs an implicit, finite volume, Lower-Upper (LU), time-marching method to solve the complete Navier-Stokes and species equations in a fully coupled and very efficient manner. A chemistry model with nine species and eighteen reaction steps is adopted in the program to represent the chemical reactions of H 2 an air. To demonstrate the capability of the program, flow fields of underexpanded hydrogen jets transversely injected into the supersonic airstream inside the combustors of scramjets are calculated. Results clearly depict the flow characteristics, including the shock structure, the separated flow regions around the injector, and the distribution of the combustion products.

Supersonic Combustion of Hydrogen in a Vitiated Airstream Using Transverse Injection

Theme I N this paper, an investigation of the two-dimensional supersonic jet interaction flowfield with and without chemical heat release is presented, and the spontaneous ignition limits of the bulk flame produced far downstream are determined. Highly underexpanded hydrogen and nitrogen jets are injected from a converging slot nozzle perpendicular to the supersonic vitiated air stream, at various airstream and injectant conditions. The parameters varied during the experiments include the airstream stagnation temperature and oxygen concentration, and the injection pressure. The temperature profiles and the Schlieren photographs of the resulting flowfield with chemical heat release are compared with those of nonreacting case. From these results, the ignition mechanism of supersonic diffusion flame and the extent to which chemical heat release changes the jet interaction flowfield are discussed.

Including methods for the study of refractive index fields in combustion and aerodynamicsF. J. Weinberg. London: Butterworths, 1963. x+251 pp. (illus.). 55s

Most experimental investigations of underexpanded hydrogen jets have been limited to circular nozzles in an attempt to better understand the fundamental jet-exit flow physics and model this behaviour with pseudo source models. However, realistic compressed storage leak exit geometries are not always expected to be circular. In the present study, jet dispersion characteristics from rectangular slot nozzles with aspect ratios from 2 to 8 were investigated and compared with an equivalent circular nozzle. Schlieren imaging was used to observe the jet-exit shock structure while quantitative Planar Laser Rayleigh Scattering was used to measure downstream dispersion characteristics. These results provide physical insight and much needed model validation data for model development.