Flame propagation characteristics and gas-phase oxidation of nitrous oxide and propane

Abstract

Nitrous oxide and fuel blends propellant as one of the substitutes for highly toxic hydrazine are under investigation. This study investigated the flame structure and dynamics of stoichiometric nitrous oxide and propane mixture (N2O/C3H8) by using polymethyl methacrylate (PMMA) tubes of varying inner diameters (5, 10, 15, and 50 mm) and a consistent length (1400 mm). The influence of tube diameter on flame acceleration was analyzed. The results reveal that within the 50-mm diameter tube, the flame propagation speed increased as the flame front moved forward in the tube, achieving a maximum speed of 532 m/s. In the tubes with 5-, 10-, and 15-mm diameters, all three stages—deflagration, transition to detonation, and detonation attenuation—were observed. Notably, the flame acceleration rate and maximum propagation velocity increased with the tube diameter, with the maximum velocities in the 5-, 10-, and 15-mm tubes being 1900, 2060, and 2140 m/s, respectively. The oxidation pathways of C3H8 reacting with N2O were studied using the B3LYP/6–31++G** method based on density functional theory. Thus, the study could determine changes in the configurations of reactants, intermediates, transition states, and products; the characteristics of the potential energy associated with the reaction pathways; and the reaction laws and thermodynamic parameters.