Experimental study on the characteristic premixed methane/hydrogen deflagration and water mist suppression in a semi-confined duct

This study investigates the characteristics of the deflagration process in premixed methane/hydrogen mixtures and the suppression effect of water mist in a semi-confined duct under various experimental conditions. Increasing the hydrogen fraction in the methane/hydrogen mixture enhanced the maximum flame velocity, maximum overpressure, pressure rise rate, and deflagration intensity. For unobstructed deflagration at an equivalence ratio of 1, deflagration intensities increased by 43.53% and 122.63% for hydrogen fractions of 25% and 35%, respectively, compared to a 15% hydrogen fraction. In obstructed deflagration, Rayleigh-Taylor and Kelvin-Helmholtz instabilities intensified flame instability and turbulence vortices between obstacles. Compared to unobstructed deflagration, obstructed deflagration showed increases of 165.04% in maximum flame propagation velocity, 161.18% in maximum overpressure, 293.96% in maximum pressure rise rate, and 985.35% in deflagration intensity. Under suppression with 8 μm water mist, yellow-colored bubbles persisted behind the flame front until the flame exited the duct. However, as the water mist droplet diameter increased, the appearance of yellow-colored bubbles behind the flame front diminished, and suppression efficiency gradually decreased with increasing droplet size.