An analytical solution for wall film heating and evaporation

Abstract

The evaporation of the fuel wall film considerably affects the performance and exhaust emissions of internal combustion engines. An analytical model for wall film heating and evaporation was developed and applied in this paper for predicting the temporal and spatial temperature distributions of the liquid film. The effects of the heat conduction between the fuel film and the wall, the convection between the film surface and the surrounding gas, and the film evaporation were taken into account in the present analytical model. This analytical solution was validated by the predictions from the discrete numerical vaporization model, and it is found that accurate predictions can be obtained by the present model. In order to understand the evolution behavior of the wall film, the influence of the wall temperature, the ambient pressure, and the initial film thickness were investigated. The results indicate that the evolution of the wall film evaporation can be divided into two distinct stages, i.e., an initial rapid heating stage and a slow cooling stage. The lifetime of the wall film can be shortened by increasing the wall temperature, decreasing the ambient pressure and the initial wall film thickness. The purpose of this work is to reproduce the transient behaviors of the wall film heating and evaporation with an analytical solution, which is easy to setup and solve.