Experimental and simulation-based investigation of the performance of a 100 % methanol port-injected spark-ignited engine

Abstract

The maritime sector faces major challenges with increasing regulations from the International Maritime Organization (IMO) and national regulations for CO2, SOx and NOx. Innovative fuel types for maritime use are now under development by various stakeholders. Methanol shows considerable potential as one of the most promising for implementation in the short to medium term, based on the potential availability, emission reduction, and energy density. The Green maritime methanol (GMM) project is Netherlands based collaboration of important stakeholders such as shipbuilders, engine manufacturers and universities. Within this project, methanol is researched as a potential alternative combustion fuel for maritime vessels. For this purpose, the ”Dutch Caterpillar engine dealer” PON Power provided a G3508A engine available as a retrofit option. The engine is a turbocharged spark-ignited natural gas (NG) engine with 8 cylinders and a rated power of 500 kWe at 1500 rpm. After six months of rebuilding the engine, the spark-ignited (SI), port fuel injected (PFI) engine runs on 100% methanol. Tests with stable engine operation were achieved with 100% methanol at 25%, 50%, and 75% engine loading and a constant engine speed of 1500 rpm.
In this research, experiments and modelling have been performed to study combustion using 100% PFI methanol. Measurements are realized with varying: ignition timings, NOx emission settings, and manifold temperatures. Data collected during these measurements such as in-cylinder pressures, emissions, and temperatures, provided a comparison between running the engine on methanol or natural gas. In this comparison combustion stability is determined with the coefficient of variation (COV) of Pmax and of imep, optimum ignition timing is determined and engine efficiency is calculated and compared to NG. Modelling is accomplished with a TU Delft model of the G3508A SI engine adjusted for the use of 100% methanol as a fuel. A modified sub-model for the PFI and vaporization of methanol has been developed. These engine data will be used to validate the methanol engine model and to optimise the engine performance for further experimental runs and better understanding the use of methanol as a fuel.
The effect on the performance and the combustion when 100% methanol is used as fuel for a SI PFI engine compared to premixed injection of natural gas is shown in this work. The engine operates stably on methanol at 50% and 75% load within ignition timings of 16-24 °CA BTDC, but less stable than with NG. Heat release indicates an almost similar combustion duration, but shorter combustion duration is shown for methanol. Also with methanol, the crank angle where 50% of fuel is burnt (CA50) is shown earlier compared to NG. The faster premixed combustion, combined with a better found fuel consumption operating point, resulted in higher efficiencies for methanol compared to NG for the tested 50% and 75% load at comparable operating conditions.