Experimental study of spray explosion characteristics and flame propagation in methanol blended water/ethanol

Abstract

Methanol, widely used as a fuel and chemical raw material, has a strong affinity for water. Meanwhile, by-products such as ethanol are thermodynamically more stable than methanol, making their formation more favorable. If crude methanol leaks during storage and transportation, it can result in severe spray explosion accidents. Currently, the spray explosion characteristics and flame behavior of methanol containing impurities remain inadequately investigated. Therefore, using a spray explosion experimental system, this study examines the explosion characteristics and flame propagation of methanol under different ignition delay times (IDT) and ambient temperatures (T_a) with varying water/ethanol mass fractions. The explosion characteristics of blended methanol are assessed based on the maximum explosion pressure (p_max), the explosion pressure rise rate (dp/dt), and the maximum explosion pressure arrival time (t_p). The results indicate that due to the expansion caused by water evaporation during combustion, a small amount of water can enhance methanol explosions. However, when the water content exceeds 4 %, the suppression effect becomes evident, significantly reducing both p and dp/dt. IDT has a substantial impact on turbulence intensity within the system. At low IDT, strong turbulence leads to a lower p_max, which subsequently rises. When the IDT exceeds 260 ms, droplet aggregation and sedimentation may occur, leading to a reduction in p_max. The t_p shows a linear relationship with IDT. T_a promotes the evaporation of gaseous methanol, resulting in increased p_max and dp/dt, both of which show a positive correlation with T_a. Compared with gaseous combustion flames, spray explosion flames exhibit significant instability. Water can effectively inhibit the flame propagation speed of spray explosions. At low IDT, turbulence enhances flame propagation and development, resulting in a greater peak flame propagation speed. An increase in T_a enhances molecular thermal motion, leading to a substantial increase in the average flame propagation speed.