A Study on the use of Intake Flow Path Modification to Reduce Methane Slip of a Natural Gas-Diesel Dual-fuel Engine
2022-01-0561
03/29/2022
- Event
- Content
- Use of natural gas-diesel dual-fuel (NDDF) combustion in compression ignition (CI) engines is one method of reducing the net greenhouse gas (GHG) and particulate matter (PM) emissions of these engines. Compressed natural gas (CNG) is injected into the intake manifold of the engine and the air-CNG mixture is ignited by a direct injection (DI) of diesel in the cylinder. One of the main challenges with NDDF combustion is the methane (primary component of CNG) slip at low and medium loads which reduces the efficiency and offsets the advantage of lower GHG emissions of the engine. In order to address this issue, an intake manifold insert is devised with the objective to alter the intake flow profile into the engine. This can potentially modify the in-cylinder flow profile and intensify the mixing between diesel and CNG/air mixture in order to improve the CNG utilization in the cylinder. Tests are conducted without and with the insert immediately upstream of the intake valves to compare diesel and NDDF combustion at a medium engine load and two engine speeds. A single-cylinder, four-stroke, heavy duty research engine is used for the tests. In the absence of direct flow measurement, three-dimensional numerical simulations, performed with a computational fluid dynamics (CFD) software suite, are used to estimate the changes in the in-cylinder flow profile with the use of the insert. Results indicate that the use of the intake insert can decrease the methane slip and carbon monoxide emissions of NDDF combustion at the expense of increase in the emissions of nitrogen oxides (NOx) and decrease in the brake thermal efficiency (BTE). Distinct differences in the combustion characteristics of diesel and NDDF combustion are identified without and with the use of the insert. The use of the intake insert causes an overall decrease in the GHG emissions in most cases. By using low levels of exhaust gas recirculation (EGR), the NOx emissions of NDDF combustion can be reduced with no significant impact on the GHG or PM emissions.
- Citation
- Dev, S., Yousefi, A., Lafrance, S., Missaghian, R. et al., "A Study on the use of Intake Flow Path Modification to Reduce Methane Slip of a Natural Gas-Diesel Dual-fuel Engine," SAE Technical Paper 2022-01-0561, 2022, .