Experimental study on performance of a two-stroke single cylinder engine applying PODE/methanol/ammonia blends and direct injection strategy

In the context of global fuel decarbonization, methanol can substantially reduce soot emissions owing to its high oxygen content. Dissolving ammonia in methanol to form an ammonia–methanol blended fuel can reduce the overall carbon content while enabling ammonia to be incorporated into a liquid fuel mixture. In addition, polyoxymethylene dimethyl ethers, characterized by high oxygen content, high cetane number, and good miscibility with methanol, can compensate for the low reactivity of methanol and ammonia, thereby facilitating fuel preparation and practical application. Therefore, the proposed PODE/methanol/ammonia blending strategy provides a feasible technical pathway for achieving efficient and low-carbon combustion in compression ignition engines. In this study, the performance and emission characteristics of a low-speed two-stroke single-cylinder engine fueled with PODE/methanol blends, PODE/methanol/ammonia blends, and pure PODE were investigated under direct injection mode. The results show that, compared with pure PODE, PODE/methanol and PODE/methanol/ammonia blends shorten combustion duration. For PODE/methanol/ammonia blends, ignition delay is insensitive to injection timing, whereas advancing injection timing effectively shortens combustion duration and increases indicated thermal efficiency by 7.3%. Meanwhile, indicated mean effective pressure and combustion cyclic variation also increase with advanced injection timing. At low load, premixed methanol hinders stable flame propagation, leading to higher cyclic variation. Compared with pure PODE, PODE/methanol/ammonia blends reduce CO 2 emissions by 20.2% and exhibit slightly higher NO X emissions than PODE/methanol blends, but still much lower NO X emissions than pure PODE. Retarding injection timing reduces NO X emissions by 26.1%, but increases CO 2 , CO, and THC emissions. With increasing load, NO X , CO 2 , CO, and THC emissions all decrease. These results demonstrate the combustion feasibility and application potential of PODE/methanol/ammonia blends in diesel engines.