Detonation behaviors of stoichiometric H2-O2 mixture diluted with He, N2, CO2 at different initial pressures

Abstract

In this study, the detonation parameters for stoichiometric H2-O2 mixtures diluted with varying amount of He, N2, CO2 are measured and analyzed in a small bore tube at different initial pressure P0. Signals of flame front and cell patterns are obtained by photodiodes and smoked foil technique, respectively. Experimental results indicate that as dilution mole fraction increases, the average detonation velocity deviates more from the theoretical value, and the detonation velocity deficit increases. The detonation velocity deficit of the H2-O2-N2 mixtures is relatively smaller than that of the H2-O2-He mixtures. The maximum detonation velocity occurs at 65% He dilution fraction. The cell sizes of the H2-O2 mixture diluted with CO2 are most affected by P0. The dilution mole fraction less than 10% has little effect on the cell size at higher initial pressure. The H2-O2-He mixture can make the induction zone length shorter than that of H2-O2 mixture as P0 increases. The detonation instability increases as N2 or CO2 dilution fraction increases, and the cellular instability decreases as He dilution fraction increases. Detonation parameters such as reaction zone thickness are calculated to introduce a cell size predicting formula based on the Ng model. Linear relationships are determined by: λ = 42.457 Δi (H2-O2-N2 mixture), λ = 48.945 Δi (H2-O2-He mixture).