1D simulation, performance response analysis, and multi-objective optimization strategy for a marine methanol/diesel dual-fuel engine

With the rapid advancement of green shipping and low-carbon fuels, methanol has emerged as a promising marine alternative fuel. However, its low auto-ignition reactivity and high latent heat of vaporization impose challenges on combustion stability and substitution levels in dual-fuel engines. To improve the performance of a marine methanol/diesel dual-fuel engine, a 1D engine model was developed based on experimental data, followed by a systematic sensitivity analysis to evaluate the effects of key parameters on fuel economy, combustion behavior, and emissions. The results indicate that combustion sensitivity varies significantly with different parameters. Specifically, for each 1°CA advance in diesel main injection timing, the crank angle of peak in-cylinder pressure advances by 0.38–0.96°CA, while NOx emissions increase by approximately 0.5–1.4 g/kW·h. When the diesel pilot injection quantity increases from 0 mg to 40 mg, the two-stage heat release behavior is enhanced, and the MPRR first decreases and then increases, with variations of 21–101 % across different operating conditions. As the compression ratio increases from 15 to 17, NOx emissions at 25 % and 50 % load decrease by 5.094 g/kW·h and 2.635 g/kW·h, respectively. By contrast, pilot injection timing exhibits the smallest influence on overall performance. On this basis, a DOE-based multi-objective constrained optimization was conducted under different operating conditions. The results indicate that the BTE increases by 0.676 % on average, while EFCR decreases by 0.667 % on average and CO2 emissions decrease by 3.209 % on average. These findings provide quantifiable design guidance for combustion control and parameter optimization of marine methanol dual-fuel engines.