Experimental investigation of operating conditions on performance and emissions of spark ignition ammonia direct injection engine

Hydrogen, attracting attention as a future eco-friendly fuel, is difficult to handle and store because of its material characteristics; thus, ammonia has been proposed as an alternative. However, when only ammonia is utilized as the fuel, the operating range in which stable combustion is possible is limited because of the slow combustion speed and high minimum ignition energy. Here, to examine the applicability of ammonia as an engine fuel, an experiment was conducted based on changes in hydrogen energy ratios and operating conditions in a directinjection ammonia combustion engine with hydrogen addition. The hydrogen energy ratio for stable operation is about 4.5 % at 1500 rpm under low-load operating conditions such as BMEP 0.2 MPa, and hydrogen must be supplied at a high energy ratio of 27.8 % in the case of a rated-power condition of 3800 rpm. The unburned NH3 and NOx emissions were high at 9285 ppm and 4870 ppm, respectively, under rated-power operating conditions.