IGNITION AND DETONATION INITIATION OF MOVING HYDROGEN-AIR MIXTURES AT ELEVATED TEMPERATURE AND PRESSURE

Abstract

Experimental and computational studies of detonation initiation, using Deflagration-to-Detonation Tran sition (DDT) processes, were performed to investigate the effect of varying inlet parameters at elevated temp eratures and pressures on the run-up to detonation in hydrogen-air mixtures for a repeating detonation rig. It is found that the gasdynamic and chemical processes which effect the initial flame acceleration are the rate-li miting processes in determining the time scale of run-up t o detonation. A parametric study was performed in which the independent parameters of temperature, T (290 ‐ 615 K), pressure, P (1.0 ‐ 4.0 atm) and inlet fill velocity, Vb (10 ‐ 40 m/s) were systematically varied, and thei r effect on location, L DDT , and time of detonation, t DDT , initiation was quantified. A Pareto of effects in this parametric study shows variation in fill veloc ity and rig pressure have the largest effect on t DDT , while it shows variation in fill velocity and rig pressure followed by initial gas temperature have the largest effect on L DDT . Dimensionalized best-fit correlations were obtai ned from the test measurements for t DDT and L DDT as functions of P, T, and V. A nondimensional be st-fit correlations was obtained from the test measurements for t DDT as a function of key nondimensionalized independent variables, namely density expansion ratio α, a nondimensional length scale l/l F (where l is the integral length scale and l F is the laminar flame thickness) and a nondimensional velocity scale M (flow Mach number in the reactants) which govern the flow and chemical processes that occur during the DDT process.