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A mathematical model of formation and transport of liquid films, incorporating a droplet-wall impaction model and exchange mechanisms with the gas-phase, has been developed and incorporated into the STAR-CD computational fluid dynamics code. It has been applied to a test case representation of the multi-point fuel injection in four stroke SI engines. The results indicate that the major features of droplet impaction and film development are reproduced by the model. The qualitative agreement with data in the region of spray impaction is good.

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.

Multidimensional calculations axe presented of the behaviour of sprays injected into the combustion chambers of motored reciprocating engines, in circumstances giving rise to three-dimensional spatial variations in the droplet and gas flow fields. The calculations were performed using the implicit EPISO algorithm, extended to include a Lagrangian description of the spray. The gas-phase turbulence is represented by the κ-ε model and its effect on the droplets is modelled stochastically. Two applications of the method are reported: one involves the simulation of, and comparison with data from, published experiments on a laboratory engine fitted with a single-hole injector in the cylinder wall. The second case is a demonstration calculation for a direct-injection Diesel with a cylindrical piston bowl and a four-hole injector.