Development of a Physically/Chemically Based Approach for 2-Stage Ignition Delay Calculation in Medium Speed Dual-Fuel Engines
Considering the upcoming global sulfur limitation for maritime fuels and the existing IMO Tier III legislation, natural gas as a fuel will become more important in the shipping sector. One way to use natural gas is the dual-fuel (DF) combustion process where a homogeneous lean natural gas mixture is ignited by a micro pilot injection of diesel fuel. This paper presents the first major step towards a new combustion model for the prediction of the DF combustion in the context of a 1D simulation. The combustion models known from literature are based on empirical models of a steady jet. Here in most cases the package model of Hiroyasu is used. Because the injection timing of the diesel fuel is very early and the injection ends before ignition, the spray behavior differs from that of a steady jet. Especially the well-known end-of-injection transients lead to stronger entrainment and therefore affect the ignition delay.