Experimental study on a retrofitted marine size spark-ignition engine running on portinjected 100% methanol

The maritime sector is currently facing a serious challenge of reducing emissions to meet the strict international and national emission regulations. In response to this challenge, the industry is initiating several research initiatives focused towards employment of alternative fuels in marine internal combustion engines. One of the promising alternatives is methanol. Methanol has multiple advantages such as higher volumetric energy density (including storage) compared to alternative fuels such as hydrogen and ammonia. Methanol is available at a relatively larger scale than hydrogen. Furthermore, compared to liquefied fuel storage of alternative fuels, methanol can be easily stored as a liquid onboard ships because of its liquid aggregation state at atmospheric conditions. Other advantages such as low flash point compared to LNG, fast biodegradation capabilities, and high water miscibility make it a high potential marine fuel with good safety considerations. Recognizing these benefits of methanol, the Green Maritime Methanol (GMM) project aims to investigate the uptake of methanol as an alternative shipping fuel for maritime vessels. GMM is a Dutch collaborative project among the entire sector. Research on application of methanol in marine engines is in its infancy stages and there is a knowledge gap pertaining to validated effects of methanol combustion in marine engines. This paper focusses on experimental investigations of methanol combustion in a marine spark ignited engine. To study the impact of combusting methanol, experiments were performed on a CAT G3508A natural gas (NG) engine, which is a turbocharged, spark-ignited (SI) engine with 8 cylinders and a rated power of 500 kWe at 1500 rpm. The engine was retrofitted and controlled to allow port-fuel injection (PFI) of methanol. Tests with stable engine operation were achieved with 100% methanol at 25%, 50% and 75% engine loading and constant engine speed of 1500 rpm. Engine performance on 100% methanol was also studied for varying ignition timings. In this paper, we discuss the retrofitting and safety considerations required for methanol combustion. We also present the experimental methodology employed to allow operation of the SI NG test engine on 100% methanol. The performance results of the engine operating on methanol are analyzed and compared against the results for natural gas. The engine performance for the two fuels is compared with respect to cyclic variations, in-cylinder combustion performance, engine efficiency. The results showed that engine efficiency improved by 2.2% and 0.9% at 50% and 75% load with methanol compared to natural gas for the same test conditions of ignition timing and NOx emissions. These preliminary methanol engine results show that improvements in engine efficiency can be obtained from a retrofitted SI NG engine converted to operate on 100% methanol without making any modifications to the geometrical engine specifications.