Experimental study on the deflagration characteristics of methane-ethane mixtures in a closed duct

For the study of premixed methane/ethane/air explosion propagation characteristics, the explosion overpressure parameters and flame propagation process images of premixed methane/ethane at different initial stoichiometric and volume ratios were obtained by using a horizontal closed duct and a high-speed camera. The numerical simulation method was used to study the evolution characteristics of the flow field inside the duct during explosion propagation. Parameters such as the maximum explosion pressure (P-max), maximum pressure rise rate (dP/dt)(max) and combustion time t(c) of the premixed system were acquired. The premixed system flame front position was detected based on a self-written program of the Canny operator, and the variations in the premixed flame propagation speed were obtained. The results show that with increasing ethane volume fraction, the premixed system explosion process is more rapid and drastic. Each premixed system can be divided into three combustion stages according to the different ethane volume fractions: the methane-dominant combustion stage (I), transition stage (II) and ethane-dominant combustion stage (III). When a tulip flame is generated, a vortex is created inside the duct. After a plane flame is formed by the flame front, the pressure rise rate (dp/dt) sharply oscillates. Based on the GRI-Mech3.0 mechanism, the chemical kinetics analysis of the premixed gas showed that the production rate of key free radicals (H*,O* and OH*) gradually increased with the increase of ethane volume fraction, thus enhancing the explosion reaction intensity.