The effect of pressure evolution on flame propagation dynamics of H2/CH4 mixtures explosion in a horizontal closed duct

Abstract

To investigate the effect of explosion pressure on flame propagation of H2/CH4 mixtures, the pressure dynamics of H2/CH4 mixtures explosion with different volume fractions of hydrogen (0, 0.2, 0.4, 0.6, 0.8, 1 (×100/%)) and equivalence ratios (0.8, 1, 1.2, 1.4) is measured using 2 pressure sensors in a horizontal duct with ignition electrode position not at the end. The flame propagation characteristic is studied using images recorded by a high-speed camera. Through the analysis and discussion of the experimental results, the interaction among explosion pressure, flame front, and flow field are discussed. The results show that when the volume fraction of hydrogen is greater than 0.6, the rate of explosion pressure rises, the flame front position, and the flame front speed are greatly improved. At higher and lower equivalence ratios, it is easier to form distorted “tulip” flames. As the volume fraction of hydrogen increases, the inclination angle of the flame front decreases, and becomes a typical “tulip” flame gradually. The convection of the flow field is an important cause of pressure oscillation, which makes the pressure distribution uneven, and its influence on Pmax, (dP/dt)max, and tc is weak. As the volume fraction of hydrogen increases, the duration of pressure oscillation decreases, and the intensity of pressure oscillation increases. The pressure wave has a substantial impact on the flame front propagation of distorted “tulip” flames and the pressure history of typical “tulip” flames.