Study on the effect of ventilation conditions on the methanol fuel evaporation characteristics in the engine room leakage accidents

The volatility of methanol poses fire and explosion risk when methanol fuels leak in the engine room of methanol-powered vessels. Considering that ventilation conditions significantly affect methanol evaporation by altering the airflow patterns, the main contents of this research are to quantitatively study the methanol evaporation characteristics under the effect of ventilation conditions. A numerical approach is proposed to accurately capture the phase transition process in multiphase flow. Results demonstrate that the evaporation process can be divided into two stages: liquid flow stage and stable evaporation stage, based on the methanol flow state. The evaporation rate in these two stages depends on liquid flow velocity and air flow velocity, respectively. The airflow circulation efficiency can be improved by increasing ventilation velocity, adding ventilation opening and reducing ventilation temperature, which can significantly reduce the vapor accumulation in the engine room. Increasing ventilation velocity to 3 m/s will reduce flammable gas cloud by 80%, and further increasing it to 7 m/s can reduce more than 50% of vapor and 90% of flammable gas cloud. The other two methods can also achieve the same effect. Among which, the more important role of reducing ventilation temperature is to eliminate vapor accumulation in the stable evaporation stage.