There is increasing interest in application of various alternative fuels in marine diesel engines, including methanol. One of the challenges in the relevant research is the development of computer codes for simulation of the dual-fuel working process and engineering optimization of engines. In this work the mathematical model is described which simulates a mixture formation and combustion in an engine with a dual-fuel system, in which methanol is used as main fuel and a pilot portion of diesel oil is injected to ignite methanol. The developed combustion model was incorporated into the existing engine full cycle thermodynamic simulation tool, namely DIESEL-RK [1]. The developed combustion model includes the self-ignition delay calculation sub-model based on the detail chemistry simulation of methanol pre-combustion reactions, sub-model of evaporation of methanol droplets, submodels of methanol fuel sprays penetration, spray angle and droplets forming, respectively. The developed computer code allows engineers to account for the arbitrary shape of the combustion chamber. Additionally, each fuel system (for methanol and diesel oil) may include several injectors with arbitrary oriented nozzles with different diameters and central, off-central and side location in the combustion chamber. The fuel sprays evolution model consists of equations with dimensionless parameters to account for fuel properties and in-cylinder conditions. Specifics of injection pressure profiles and interaction of sprays with the air swirl and between themselves are also considered. The model allows engineers to carry out rapid parametric analysis. Results of modelling for a medium speed dual-fuel diesel engine are presented which demonstrate a good agreement between calculated and experimental heat release curves and integral engine data.

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