CFD simulation of turbulent diffusion and phase transition of methanol spray in a 20L spherical vessel

Abstract

The atomization process of flammable liquids occurs across various aspects of chemical industry production. Atomized droplets dispersed into the surrounding environment significantly enhance their risk, as the resulting fuel-air mixture requires minimal energy for ignition. Methanol, a widely used chemical feedstock, poses significant explosion risks due to its high volatility and flammability. The spray explosion behavior of flammable liquids is commonly studied experimentally using a standard 20L spherical explosion vessel. Recently, CFD simulations have emerged as a cost-effective and reliable approach for predicting particle behavior with high accuracy. In this study, the numerical simulation of methanol spray in a 20L spherical vessel utilized the DPM model. The continuous and discrete phases adhere to the Euler-Lagrange approach, employing two-way coupling and incorporating phase changes of methanol droplets upon entering the vessel. The numerical model was validated using experimental data of pressure and velocity variations over time. The spatial distributions of velocity, streamline patterns, particle trajectories, and turbulent kinetic energy (TKE) were examined under various ignition delay times. The correlation between the gas-phase methanol distribution after phase change and the temperature field was investigated. The results indicate that during the initial spray stage, the 20L spherical vessel exhibits a distinct spray diffusion behavior. Strong turbulence regions were observed near the nozzle outlet and in the central axis of the vertical jet. The TKE at the vessel center varied with ignition delay time, conforming to a Sigmoidal-Boltzmann fit. The gas-phase methanol distribution within the vessel exhibited a strong correlation with the temperature field. After 120 ms, both the gas-phase methanol distribution and temperature field achieved a steady state, with methanol droplets uniformly distributed and turbulence levels relatively low. Ignition at this stage can effectively prevent issues such as reduced fuel concentration and incomplete combustion resulting from uneven fuel-air mixing or droplet settling.