ROLE OF HYDROGEN AIR CHEMISTRY IN NOZZLE PERFORMANCE FOR A HYPERSONIC PROPULSION SYSTEM

A computer model for describing quasi-one-dimensional flow of a gas mixture with area change and finite-rate chemical reactions was used to study the role of hydrogen/air chemistry in nozzle performance for a hypersonic propulsion system. The important results obtained for a typical nozzle at a Mach 18 flight condition are as follows: 1) finite-rate chemistry should not be neglected in nozzle performance simulations because beneficial chemical processes persist throughout the entire nozzle length; 2) termolecular recombination reactions represent the principal chemical contribution to nozzle performance; 3) intermediate HNO species have little effect on hydrogen radical recombination; and 4) nitrogen oxides are not involved directly in the hydrogen radical recombination process but rather they provide a source of oxygen for recombination. In addition, the study shows that any major reduction in the detailed reaction mechanism used here may lead to incorrect simulations of nozzle performance.