Combined effects of initial pressure and turbulence on explosions of hydrogen-enriched methane/air mixtures: Fid-Bau Portal

Combined effects of initial pressure and turbulence on explosions of hydrogen-enriched methane/air mixtures

Cammarota, F. / Benedetto, A. di / Sarli, V. Di / Russo, G. / Salzano, E.

The combined effects of initial pressure and turbulence on maximum pressure, maximum rate of pressure rise, burning velocity and Markstein lengths have been quantified for explosions of stoichiometric methane/air and hydrogen-methane/air (hydrogen = 10% molar in the fuel) mixtures. Tests have been carried out in a 5 l closed cylindrical vessel at different initial pressures (1, 3 and 6 bar), and starting from both quiescent and turbulent conditions. From the results obtained, the following conclusions can be drawn: (1) The presence of 10% molar of hydrogen in the fuel has negligible effects on the flame reactivity and, thus, on the maximum pressure, the maximum rate of pressure rise (deflagration index) and the burning velocity. (2) The presence of 10% molar of hydrogen in the fuel has appreciable effects on the flame stability, as demonstrated by the Markstein lengths. (3) On increasing the initial pressure, the maximum pressure and the deflagration index increase. This effect is less pronounced in quiescent conditions than in turbulent conditions. (4) The burning velocity and the Markstein length decrease with the initial pressure. The decreasing effect is stronger for the laminar burning velocity than for the turbulent burning velocity. (5) The calculation of both burning velocities and Markstein lengths from the pressure time histories recorded during the closed vessel explosions provides reliable data.