Heat and mass transfer of fuel film on the piston top of internal combustion engines

In direct injection engine wall-wetting of injected fuel leads to high hydrocarbon (HC) emission. In order to quantitatively study the HC formation near piston top, a heat and mass transfer model of fuel film and droplet is necessary. Previous research developed a model based on boiling theory and correlations. The Leidenfrost effect was well predicted with neglecting the effects of heating surface roughness. In this research newer nucleate boiling model including roughness effects is combined with proven natural convection model to calculate the total wall heat flux within the nucleate boiling regime. The result generated by the combined model is compared with experimental data. In addition to the nucleate boiling regime, more film boiling experimental results are reviewed to further validate the current film boiling model. Also, the natural convection model is extended into supercritical regime by applying appropriate equation of state. The resulting boiling curve models a condition more similar to the operation condition of internal combustion engine and provides better evaluation of the heat and mass transfer process.