Combustion analysis of methane-hydrogen port injection combined with OMEN/Diesel spray injection in an RCCI engine

Compressed Natural Gas (CNG) is recognized as an environmentally friendly alternative vehicle fuel, but it has a low flame speed. Combining hydrogen with CNG to create 'hydrogen compressed natural gas' (HCNG) allows for faster and leaner combustion. Additionally, OME2_4 with varying cetane numbers, from 63 for OME2 to 90 for OME4, serves as a highly reactive fuel suitable for use in a dual fuel strategy known as RCCI (reactivity-controlled compression ignition). This project investigates the impact of adding OME2_4 to HCNG, focusing on pressure, temperature, and emissions. Results indicate that lengthening the OME chain advances the peak heat release rate but delays the second combustion phase. In diesel + HCNG, the first-phase combustion is 2 degrees CA shorter than OME2 + HCNG, resulting in a 6.5% higher peak pressure than OME2 + HCNG and a 20% increase over basic diesel. Lengthening the OME chain from OME2 to OME4 raises the peak pressure by about 6.2%. The addition of gaseous fuels, especially hydrogen, increases peak temperature by 16%. OME4 + HCNG has a similar peak temperature to OME3 + HCNG, while OME2 + HCNG is about 1.5% lower than OME4 + HCNG.