Comparison of Combustion, Emissions and Efficiency Characteristics between LPG and Ammonia-fueled Spark Ignition in a Light-duty Engine

Since the 'Global warming of 1.5 °C report of the IPCC(Intergovernmental Panel on Climate Change) was published in 2018, it is inevitable to hear proposal that can reduce the usage of conventional fossil fuels in the fields of transportation and power generation. As a result, the use of hydrogen and ammonia on combustion-based powertrains became an important issue. Nowadays, although hydrogen is the most famous carbon-free fuel used on fuel cell systems, it is difficult to store and transport. On the other hand, ammonia can be easily liquified by pressurizing it, and it is easy to produce. Yet, ammonia is hard to apply on a fuel cell system by itself, so it is better to use ammonia on combustion-based powertrains, such as an internal combustion engine, hi this research, ammonia was supplied to a 2.5 L light-duty SI(spark ignition) engine under relatively high load conditions. To understand the characteristics of an ammonia engine better, all experimental results were compared to an LPG(Liquified Petroleum Gas)-fueled SI engine, which is already widely used in the field of transportation. The result emphasized that, as load condition increased, the brake thermal efficiency(BTE) of ammonia also increased compared to LPG due to its high knocking resistance. However, the issues of poor ignitability and unburned ammonia must be addressed in future studies.