Advanced Model of Nitric Oxide Formation in Hypersonic Flows

A model for nitric oxide (NO) formation in low-density hypersonic e ows is presented. The thermal nonequilibrium reaction rates, reactant energy removal rates, and product energy disposal rates are based on a quasiclassical trajectory analysis of the Zeldovich reactions. At hypersonic e ow conditions, the newly obtained reaction rate for the second Zeldovich reaction is approximately an order of magnitude larger than the commonly used rate. The rate of this reaction is a weak function of the reactant internal energy, but it produces vibrationally excited NO molecules that result in an elevated NO vibrational temperature. A e owe eld model that includes these effects is proposed, and a computational e uid dynamics method is used to simulate the BSUV1 and BSUV2 e ight experiments. The new model generally improves the agreement with the spectrally resolved radiation data; however, it appears that there are additional mechanisms that preferentially remove the highly excited NO molecules.