Chemical kinetics of hypergolic ignition in hydrazine/nitrogen-dioxide gas mixtures

A detailed chemical kinetic mechanism for hypergolic ignition of N2H4/NO2 gas mixture at low temperatures has been constructed. In this mechanism, the hypergolic ignition is caused by following sequential reactions of H atom abstraction from N2Hm by NO2. N2H4 + NO2 = N2H3 + HONO or HNO2 (R1) N2H3 + NO2 = N2H2 + HONO (R2) N2H2 + NO2 = N2H + HONO (R3) N2H + NO2 = N2 + HONO (R4) These reactions are exothermic, especially heat release by the reaction (R4) is large because of N2 production. Temperature rise caused by the heat release accelerates the initiation reaction (R1). This 'thermal feedback' is responsible to the hypergolic ignition at ambient temperatures. Since no experimental and theoretical information was available on these reactions, rate coefficients were evaluated on the basis of transition state theory, unimolecular rate theory, and master equation analysis with quantum chemical calculations of potential energy curves. Results of simulations by using the present mechanism including reactions (R1)-(R4) reasonably agree with existing experimental data.