Influence of fuel composition on combustion and emissions characteristics of natural gas/diesel RCCI engine

• Effect of natural gas composition and engine speed on RCCI combustion is studied.
• Varying fuel composition and engine speed affects RCCI performance and emissions.
• RCCI Engine fuelled with higher WN displayed higher peak pressure and temperature.
• RCCI Engine fuelled with higher WN displayed higher NOx and lower UHC and CO.
• By increasing engine speed, CA50 is delayed. CO and UHC significantly increase.

The effects of natural gas composition and engine speed on combustion and emissions characteristics of an RCCI engine fuelled with natural gas/diesel at engine medium load of 9 bar indicated mean effective pressure (IMEP) are studied. Natural gas with low reactivity is assumed to be inducted into the engine through the intake port, while diesel fuel with high reactivity is directly injected into the engine using a double injection strategy. The obtained numerical results are validated against available results in the literature. Two different compositions of natural gas (including pure methane) are taken into account to study RCCI combustion and emissions characteristics. It is shown that Wobbe number (WN) of gases and engine speed significantly affects RCCI engine combustion and emissions. The gas with higher WN displayed higher peak pressure, temperature and NOx emissions, and lower unburned hydrocarbon (UHC) and carbon monoxide (CO) emissions.