Abstract
The use of gaseous fuels for internal combustion engines is expected to increase in the future. Heavy duty diesel gas engines often use dual-fuel combustion based on natural gas/methane that is supplied with intake air by injecting the gas into the intake manifold and using direct injection (DI) of pilot diesel as the ignition source. This means that a large fraction of the chemical energy in the fuel is aspirated with the intake air.
In order to simulate dual-fuel combustion, a new computer model incorporating two coupled combustion modes has been developed: a diesel mode modeled as a partially premixed reactor, and a flame propagation mode. The combustion model was implemented in the updated KIVA-3V CFD engine code.
The paper focuses on validating the dual-fuel combustion model (natural gas (NG) or methane with diesel oil) by comparing its predictions to experimental data. An experimental investigation was conducted on a single-cylinder Volvo D12C DI Diesel engine with a displaced volume of 2.02 liters that was modified to operate under dual-fuel conditions. Experimental data such as in-cylinder pressures, heat release traces and emissions (NOx and CO2) were acquired at constant engine speed and load. Different equivalence ratios of the gaseous mixtures were prepared in the cylinder before ignition, and compared to the calculated dual fuel engine in-cylinder parameters. The model was also applied to conventional diesel combustion as a comparative study.
Keywords: combustion modeling, dual-fuel combustion, natural gas, methane