Three-dimensional numerical analysis of diesel combustion under cold ambient conditions

Abstract

A lower compression ratio has been demanded for diesel engines in recent years to improve fuel consumption, exhaust emissions and maximum power recently. However, low compression ratio may have combustion instability issues under cold temperature condition, especially just after engine started. As the first step in this study, cold temperature combustion was investigated on the basis of an in-cylinder pressure analysis, and it was found that higher heat release around top dead center, which was mainly attributed to pilot injection, was a key factor in reducing engine speed fluctuation. Three-dimensional computational fluid dynamics simulations were conducted to obtain a better understanding of combustion under cold condition, particularly mixture formation near the glow plug. Specifically, for this purpose, a time-scale interaction combustion model was developed for simulating combustion phenomena. This model was based on a reasonable combustion mode, taking into account the characteristic time scale of chemical reactions and turbulence eddy breakup. In addition, the parameters of the ignition model and computational grids near the glow plug were improved for application to cold start conditions.

Keywords

Diesel computational fluid dynamics ignition combustion cold glow plug

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