Study on the performance of premixed natural gas/ammonia engine with diesel ignition

Abstract

To improve the in-cylinder knock caused by premixed natural gas combustion in engines, ammonia blending in natural gas can slow down the combustion rate and thus can avoid knock combustion. In this paper, the effects of diesel ignition of premixed natural gas/ammonia on engine combustion and emission performance were studied by simulation. The study has set 10 groups of ammonia blending ratios from 0 to 90% in natural gas. The results show that as the ammonia blending ratio in natural gas increases, the engine dynamics gradually decrease. The fuel consumption rate is the lowest when the ammonia blending ratio is 60%. With the ammonia blending ratio and the slit effect in the cylinder increase, the unburned ammonia in the piston ring gap increases, and the CO2 and NOx emissions decrease significantly. However, the emissions of soot, HC, CO, CH2O, N2O, and NO2 increase after ammonia blends. The impact of N2O emissions on the greenhouse effect is 298 times that of CO2, therefore, N2O emissions should be noted. In this paper, the premixed 40% natural gas/60% ammonia is selected as the best ratio, which can effectively reduce the knock combustion phenomenon in the cylinder and promote the engine to near zero carbon emissions.