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A detailed analysis is performed upon the results of CFD combustion simulations of several diesel fuel spray flame experiments. Simulations are validated against measurements from a constant volume combustion chamber testcase [9]. Particular emphasis is made in the analyses to identify mechanisms associated with the ‘lift-off’ phenomena characteristic of contemporary high injection pressure diesel engine combustion. A recently developed industry state of the art RANS hybrid combustion model (Extended Coherent Flame Model - 3 Zones) [41] is used which takes account of both a propagating (premixed) flame combustion mode as well as the conventionally assumed diffusion flame mode used in most diesel combustion models. The location of and development of a propagating reaction front, obtained from analysis of the progress variable within the model, is studied in relation to the lift-off behaviour.

This paper uses CFD methodology to simulate a prototype Diesel engine operating at high peak pressures (HPP). Under these conditions the accurate estimation of the level of thermomechanical stress on metal components is crucial for the design process. CFD simulations have been performed of flow, combustion and heat transfer to provide detailed insight into the in-cylinder behaviour of the engine. Particular emphasis was put on improving wall heat transfer predictions which have been compared with detailed local time-resolved surface heat transfer measurements. It is demonstrated that heat transfer strongly depends on flame spread via flow field and spray-related processes. Hence local heat transfer measurements also provide a stringent testing ground for spray and combustion model performance. Additionally it is shown that widely-used empirical heat transfer correlations are incapable of estimating the critical level and nature of thermal loading.

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.

Multi-dimensional modelling of the flow and combustion promises to become a useful optimisation tool for IC engine design. Currently, the total simulation time for an engine cycle is measured in weeks to months, thus preventing the routine use of CFD in the design process. Here, we shall describe three tools aimed at reducing the simulation time to less than a week. The rapid template-based mesher produces the computational mesh within 1-2 days. The parallel flow solver STAR-CD performs the flow simulation on a similar time-scale. The package is completed with COVISEMP, a parallel post-processor which allows real-time interaction with the data.