Quantification of the explosion risk of biogas-hydrogen-air mixtures with various hydrogen fractions in a 20 L chamber

The explosion risk and severity of biogas-hydrogen-air mixtures are investigated by measuring the explosion parameters—namely, the maximum explosion pressure, maximum pressure rise rate, deflagration index, and laminar burning velocity—using a 20 L spherical explosion chamber. Accurate deflagration indices are calculated using the maximum pressure rise rate derived from a smoothed pressure–time curve. The values of all parameters increase monotonously with increasing hydrogen fraction in biogas-hydrogen-air mixtures: the maximum explosion pressure increases by up to 1.33 times, the maximum pressure rise rate and deflagration index increase by up to 2.54 times, and the laminar burning velocity increases by up to 1.7 times. Hydrogen addition shortens the deflagration duration and accelerates pressure build-up. The addition of a small amount of hydrogen leads to an explosion risk close to that of pure methane. In summary, the addition of hydrogen into biogas-air mixtures significantly increases the explosion risk and severity.