Search Results

In this paper a multidimensional method is described and evaluated for the prediction of Diesel sprays. The method, which shares many features with similar approaches developed elsewhere, embodies an Eulerian description of the gas flow and a stochastic Lagrangian treatment of the spray droplets. Gas phase turbulence effects are represented by the k-ε model and their influence on the droplets is modelled stochastically, as are the processes of collision and coalescence. Comparisons are made with the spray penetration measurements in a quiescent bomb of Yule et al [1] covering a range of pressures and temperatures. Satisfactory agreement is obtained at combinations of low pressure and temperature and high pressure and temperature, but not for high-pressure, low-temperature cases. The sensitivity of the predicted penetration rates to the assumed initial droplet size distribution is relatively weak, but the calculated vaporization rates are strongly sensitive.

This paper presents a mathematical model for the prediction of the dynamic characteristics of wall films formed by impinging sprays. The model takes into account the impingement pressure due to bombardment of impinging droplets, tangential momentum transfer resulting from oblique droplet impingement on the film surface, and the gas shear force at the film surface. The general transport equations of mass, momentum and energy for wall film flows are established in the boundary-layer framework. It is shown that this set of equations can be substantially simplified if local equilibrium occurs and a dimensional analysis is performed to identify the conditions for the applicability of the local equilibrium model. Solution of the full film equations is obtained by an efficient hybrid integral/numerical method, which allows numerical calculations to be performed in a two-dimensional framework. An implicit finite volume scheme is employed for this purpose.