Detonation propagation characteristic of H2–O2–N2 mixture in tube and effect of various initial conditions on it

Abstract

As for the premixed H2–O2–N2 gas ignited and induced by flame in tube, this paper represents systemic researches on its detonative formation process and flow field changes under different initial conditions (pressure, temperature, component concentration). The conservational Euler equation set with chemical reaction is taken as the basic gas phase equation model and the reduced elementary chemical reaction and shock wave problem are considered available so as to establish a theoretical model of premixed H2–O2–N2 combustible gas detonation process. A unity coupling TVD format with second-order accuracy is adopted to solve the gas phase equation and deduce the two-dimension Riemann invariant, and the TVD format for solution of the polycomponent convection equation with elementary chemical reaction is proposed. Meanwhile, a time splitting format is adopted to perfectly treat with the rigid problem resulted from the higher time difference value between gas phase flow characteristic time and chemical reaction characteristic time. It is shown by the calculation results that the detonation waves form certain angle with relation to the tube wall surface at the initial stage of ignition, so as to incur reflections and form reflection waves; during the propagation of the detonation waves, the reflection wave structures are propagated backwards the back of waves constantly, so the whole flow field is characterized of obvious two-dimension. Besides, the excessive pressure detonation occurs at first before formation of the stable detonation propagation process, then a stable detonation propagation process forms finally. Mixed gas detonation characteristics resulted from different calculated-initially parameters are different. The higher the initial temperature and pressure of flame is, the shorter the induction time for detonation formed due to combustion acceleration of the mixed gas is, but which nearly brings no great influence on the later propagation process of the detonation waves. The initial mixed gas component can influence the detonation characteristic of the mixed gas observably, when the quantity relative ratio is close to 1 and the mixed gas with larger reaction activity, its detonation propagation speed is rapider and the pressure after detonation waves is higher. The simulation result keeps accordant with the calculated result of the typical C–J detonation theory model.