Computational study of the sensitivity to ignition characteristics of the resonance in DI diesel engine combustion chambers

Abstract

PurposeThe purpose of this computational fluid dynamics (CFD) study is to give insight about the influence of the piston bowl geometry and the fuel ignition features on the resonance of direct injection diesel engines combustion chambers in order to provide support to the experimental findings on combustion noise.Design/methodology/approachThe resonance due to the burned gases oscillations in a diesel combustion chamber is caused by the sudden rise in pressure due to the initial ignition of the air‐fuel mixture, and leads to the resonance noise. In the CFD study presented here the excitation source is represented by imposing locally in a small area (excitation zone) the pressure and temperature gradients of the start of combustion. The CFD approach is first validated against the acoustic modal theory. A parametric study representing different ignition conditions is then performed with a real bowl geometry.FindingsThe solutions obtained are analysed in terms of the energy of resonance (ER) and the response in the frequency domain. It was found that the response in frequency only varies with the diameter of the bowl, while the ER varies significantly in function of the injection conditions.Research limitations/implicationsThese first conclusions need to be verified on the one hand by taking into account the piston motion, and, on the other hand, by modelling in a more realistic way the combustion excitation.Practical implicationsThis CFD study has brought some insight into the flow phenomena that affect the resonance modes of a combustion chamber.Originality/valueThis CFD study uses a novel methodology to model the effect of the combustion excitation on the resonance modes of a combustion chamber.