Study on explosion dynamics and kinetic mechanism of DME/H2 blended gas at typical fuel-lean/rich concentrations

Abstract

Owing to the promotion of DME (dimethyl ether) liquefaction transportation technology and in-station hydrogen production technology, the explosion risk of DME/H2 blended gas caused by unintended or uncontrollable leakage has become the focus of attention. To assess the explosion risk, the explosion dynamics and chain mechanism of DME/H2 blended gas at typical fuel-lean/rich concentrations were investigated with experiments and numerical simulations. The results show that the maximum explosion overpressure Pmax increases and then decreases with increasing equivalence ratio for Φ = 0.6–2.0, and Pmax is maximal for Φ = 1.0 (the maximum increase is 20.3%). In the zone away 2.85 m from the ignition point, the effect of fuel-rich concentrations on flame temperature lift and explosion risk enhancement gradually emerges, which is because that the fuel concentration here is diluted to near stoichiometric concentration. The fuel-rich concentration caused a secondary flame acceleration and further flame propagation in the outfield zone, and the flame propagation distance is increased by 22.6% compared to the fuel-lean concentration. The high temperature caused by the incorporation of hydrogen makes the pyrolysis reaction CH3OCH3(+M)CH3O + CH3(+M) promotes the explosion most effectively. The sensitivity coefficients of most elementary reactions reach maximum at the stoichiometric concentration, thereby promoting or inhibiting explosions most effectively. At Φ = 1.0–1.1, the equilibrium molar fractions of H and OH radicals are maximal, the chemical reactivity gets highest, and the explosion risk is greatest.

Keywords

• Hydrogen explosion
• Blended gas
• Flame dynamics
• Shock wave
• Sensitivity coefficient
• Chemical equilibrium