An efficient liquid film vaporization model for multi-component fuels considering thermal and mass diffusions

An improved multi-component quasi-dimensional vaporization model for wall film was proposed with considering the finite thermal and mass diffusions within the liquid film. In the improved model, high-order polynomials were introduced to describe the profiles of the temperature and component concentrations within the film. The results show that the predictions from the present quasi-dimensional model agree well with those predicted by the one-dimensional model. By investigating the effect of the thermal and mass diffusions on the vaporization of the diesel film, it is found that the thermal diffusion plays a more dominant role in the multi-component film vaporization. Compared with the linear temperature model with the linear temperature and uniform component distributions in the film, the application range of the quasi-dimensional model is considerably wider and the computational error is significantly reduced. Finally, the linear temperature, quasi-dimensional, and one-dimensional models were integrated into a Computational Fluid Dynamics (CFD) code for the simulations of film vaporization in the flow over a backward facing step and in a practical diesel engine. The results indicate that the improved model gives much better agreement with the one-dimensional solutions than the linear temperature model, while maintaining high computational efficiency under different operating conditions.