Explosion characteristics of methane-ethane mixtures in air

- Ethane has higher Upper Flammability Limit, maximum explosion pressure and maximum pressure rise rate than methane in air.
- The Lower Flammability Limits of both ethane and methane in air are almost the same.
- With increasing ethane content, the flammability and explosion pressure build-up of fuel mixtures in air are strengthened as well.
- Chemical equilibrium calculation performs a qualitative prediction of maximum explosion pressure.
- Better agreements between experiments and calculations are usually observed around stoichiometric condition.

Experiments were systematically performed in a standard 20-L spherical vessel to measure the explosion parameters of different methane-ethane/air mixtures. Data were scrutinized and carefully compared to elucidate the explosion characteristics. Firstly, it turns out that ethane has higher maximum explosion pressure, Pmax and maximum rate of pressure rise, (dP/dt)max than methane in air against the equivalence ratio. The Upper Flammability Limit, UFL (in equivalence ratio) of ethane in air is also larger; while the Lower Flammability Limits, LFLs (in equivalence ratio) of both gases in air are almost the same. Then for methane-ethane mixtures, when the ethane content increases, the value of Pmax versus equivalence ratio and the UFL both rise as well; while the LFL changes little if taking the uncertainty of measurement into account. Similarly, (dP/dt)max increases together with growing ethane content in the fuel mixture at the same equivalence ratio, especially at the fuel-rich side; but at the fuel-lean side the discrepancies are relatively smaller. In general, due to the higher reactivity, exothermicity and laminar flame speed of ethane, it can remarkably raise the explosion pressure, pressure rise rate and flammable range, and ultimately enhance the explosion risk and severity of fuel blend system.