Study on the overpressure and flame propagation of ethanol aerosol explosion in a square closed vessel: Effects of equivalence ratio and initial pressure.

• The relationship between the explosion overpressure and flame evolution of ethanol aerosols has been elucidated. • The intensity of the ethanol aerosol explosion and the speed of flame propagation increase with the initial pressure. • When P0 ≤ 70 kPa, an orange-yellow transitional phase occurs during the development of the flame. Ethanol is one of the most common renewable fuels and chemical raw materials, and there is a risk of aerosol explosion disasters at all stages of its production, transport, storage, and use. This paper investigates the explosion overpressure and flame propagation characteristics of ethanol aerosols at different equivalence ratio under sub-atmospheric pressure conditions in a square closed vessel. The results show that the maximum explosion pressure (P max), the maximum rate of pressure rise ((dP/dt) max), and the explosion index (K a) of ethanol aerosol explosions increase with the equivalence ratio, peaking at an equivalence ratio of 1.45, reaching values of 0.92 MPa, 20.25 MPa/s, and 4.73 MPa·m/s, respectively. The variation in Pmax with equivalence ratio can be fitted by a cubic polynomial function. P max , (dP/dt) max , and K a all increase linearly with the initial pressure. The evolution speed and luminosity of the ethanol aerosol explosion flames are stronger in rich fuel conditions than in lean fuel conditions, and the explosion combustion time is also shorter in rich fuel conditions. Moreover, when the initial pressure is less than or equal to 70 kPa, the blue flame of the ethanol aerosol explosion is initially dim in color, displaying an orange-yellow transitional phase before turning into a dazzling white. The flame propagation speed undergoes four stages as displacement increases: rapid increase, high-speed maintenance, rapid decline, and oscillatory weakening. The findings provide experimental data and theoretical support for preventing and mitigating explosion disasters of alcohol-based fuel aerosols under sub-atmospheric pressure conditions. [ABSTRACT FROM AUTHOR]