Assessment of the performances of a spark ignition engine when operating on ammonia

This study presents the characteristics of a spark-ignition internal combustion engines 4CH 7.6/7 and 4CHN 7.6/7 (SI engines 4CH 7.6/7 and 4CHN 7.6/7) when converting from gasoline to ammonia. Ammonia is a promising fuel due to its low cost, unlimited raw material base, availability and ease of storage under normal conditions. With complete combustion of ammonia, only one harmful component is formed - NOx, and in small quantities, since the combustion temperatures of ammonia-air mixtures are relatively low and there are practically no products containing carbon compounds, which are the main causes of the greenhouse effect. High octane number (RON=130) makes ammonia suitable for engines with high compression ratios or high boost pressure to improve engine efficiency, as its resistance to detonation is higher than that of gasoline. The results show that when converting from gasoline to ammonia at the external speed characteristic (ESC), the maximum torque M_e on the ESC increases by 15.8 %, the maximum power N_e on the ESC increases by 11,3 % (compared to the operation of 4CH 7.6/7 on gasoline in terms of ESC). The specific fuel consumption of ammonia is almost 2.5 times higher than that of gasoline. This is due to the lower volumetric energy density and lower calorific value of the ammonia-air mixture compared to gasoline. The increase in the total amount of NO_x in the exhaust gases during combustion of ammonia compared to gasoline is due to the higher maximum temperature of the cycle. The proportion of detonating fuel in gasoline is significantly higher than that of ammonia. Due to the high auto-ignition temperature and low laminar combustion rate of ammonia, the optimal ignition timing is 60 ͦ bTDC at n = 2000 min^-1, full throttle opening and α = 1.0. Increasing the compression ratio or combining the use of the Miller cycle for turbocharged engines helps improve engine performance such as power, torque and efficiency; reduction of specific fuel consumption.

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