Development of a reduced primary reference fuel-PODE3-methanol-ethanol-n-butanol mechanism for dual-fuel engine simulations

Polyoxymethylene dimethyl ethers (PODEn) have attracted worldwide attention, which could be adopted as an alternative or additive of diesel in compression ignition engines. This work focuses on the implementation of PODE for dual-fuel engine combustion. The effects of four dual-fuel combinations on the engine combustion performance and emissions were studied, including PODE-isooctane, PODE-methanol, PODE-ethanol, and PODE-n-butanol. First, a new reduced mechanism of primary reference fuel-PODE3-methanol-ethanol-n-butanol was developed and validated. This mechanism was then employed for the three-dimensional numerical investigation. The results demonstrated that at an exhaust gas recirculation (EGR) rate of 45%, PODE-n-butanol and PODE-isooctane generated higher thermal efficiencies than PODE-methanol and PODE-ethanol, primarily due to the higher reactivity of n-butanol and isooctane compared to methanol and ethanol. The highest thermal efficiency of 47.0% was obtained using PODE-NC4H9OH with a start of injection timing of −7.5°. With an EGR rate of 52%, NOx emissions of all cases met the regulation limit, which, however, were achieved at a sacrifice of engine efficiency; additionally, the highest thermal efficiency of 43.3% was achieved using PODE-CH3OH with an injection timing of −17.5°.