EFFECT OF METHANE ADDITION ON HYDROGEN COMBUSITON AND EXPLOSION CHARACTERISTICS

Hydrogen application can be carried out with the heat value of combustion maintained and the risk of explosion reduced, which is a feasible technical solution. In this paper, the effects of methane addition on the flammability limit and explosion characteristics of hydrogen are studied by using a constant volume combustion bomb. A comparative study of the explosion characteristics of hydrogen-enriched/methane/air and hydrogen/air is conducted under a wide equivalence ratio. Results show that the flammability range decreases exponentially with the increase of methane addition. The upper flammability limit can be reduced by 22.9% only by adding 10% methane. However, with 10% methane addition, its laminar burning velocity decreases, its explosion time under stoichiometric ratio increases by 20 times, and the heat loss also rises, which resulted in a slight drop of its maximum explosion pressure and a significantly lower value of maximum pressure rise rate. Combined with the analysis of the flame schlieren images, it can be seen that the addition of methane could reduce the risk of combustible gas explosion, which is not only affected by the reduction of laminar burning velocity, but also related to the weakening of flame surface cracks and cellular structure.