Kinetics of hydrogen-air flow systems. II. Calculations of nozzle flows for ramjets

Abstract

The performance of exhaust nozzles through which highly dissociated gases are accelerated depends greatly on the degree to which these gases are chemically recombined during the expansion process. An analytical method for calculating the extent of recombination for a specified nozzle contour has been developed from a combination of the chemical kinetic, gas dynamic, and state equations. A computer program has been evolved and used to solve these equations for hydrogen-air combustion products. The solution of these equations, leads to the determination of concentrations, temperatures, pressures, and velocities as a function of time or distance for the combustion process and nozzle expansion. To illustrate the use of the computer program, the extent of recombination of hydrogen-air combustion products in a convergent-divergent exhaust nozzle, having a throat diameter of 6.18 inches was calculated for combustion chamber entrance conditions of pressure 3000 psf, temperature 2000 o R, velocity 200 ft/sec, and an equivalence ratio equal to one. The results indicate that the flow freezes at an area ratio of approximately 1.1 in the nozzle convergent section.