Investigation of the upper flammability limit of ethylene/propane mixtures in air at high temperatures and pressures

The upper flammability limit (UFL) of ethylene/propane mixtures was investigated using a self-built 20 L spherical explosion characteristic experimental device at initial temperatures ranging from 20 to 200 degrees C and initial pressures from 0.1 to 1.5 MPa. The effects of temperature, pressure, and ethylene blending ratio on the UFL were analyzed, and a mathematical function of the UFL as a function of temperature and pressure parameters was derived. The results show that the UFL of ethylene and propane displayed an almost linear incline as the temperature rose. Conversely, the ascending pattern of the UFL diminished for both gases as the pressure increased. At elevated temperatures and pressures, both propane and ethylene-propane mixtures demonstrated a bilinear correlation with temperature. Moreover, the impact of increasing pressure on the UFL of blended fuels became less pronounced as the proportion of ethylene in the blend increased. Furthermore, the synergistic effect of temperature and pressure on the UFL was much greater than the sum of the effects of the two individually. Thus, the explosion risk of ethylene/propane mixtures is elevated under the synergistic effect of high temperature and high pressure, and the risk is further increased with an increase in the ethylene blending ratio.