Investigation of environmental, operational and economic performance of methanol partially premixed combustion at slow speed operation of a marine engine

This study aims to investigate the environmental, operational and economic performance of the methanol partially premixed combustion concept at slow speed operation of a ship to find a solution for the shipping emission effect on the coastal settlements while do not increase the risk and expense of the engine operation on the ships. The experimental study was done with partially premixed combustion, one of the advanced combustion concepts, on a Scania D13 heavy-duty diesel engine for its promising results of high engine efficiency and low engine emissions. In addition to the experimental study with methanol fuel, the performance of the methanol was compared with marine gas oil, which was mostly used at the slow speed operation of the ships. Empirical equations and coefficients in the literature were used to calculate specific fuel consumption, efficiency, and emissions of the marine gas oiled operation of the engine. The results showed that the combustion efficiency varied from 0.94 to 0.99 and the gross indicated efficiency varied from 0.42 to 0.46 from 10% to 25% engine loads, respectively, while the gross indicated efficiency of the marine gas oil-fuelled engine was 0.32 as a maximum value. The methanol showed good environmental performance with lower CO₂ emissions than the marine gas oil, lower NO_X emissions than the NO_X Tier III levels, varied between 0.3 g/kWh and 1.4 g/kWh, zero SO_X emissions and zero PM emissions. The economic investigation showed that the methanol cost at the low price scenario was 0.147 $/kWh, 0.138 $/kWh and 0.135 $/kWh at 10%, 15% and 25%, respectively, which were lower than the high price scenario and low price scenario of the marine gas oil; and the methanol high price scenario was still competitive with the marine gas oil scenarios.