Investigation of intake air temperature effect on co-combustion characteristics of NH₃/gasoline in naturally aspirated high compression ratio engine with sub-chamber

Recently, ammonia (NH₃), which has a higher energy density than hydrogen, has gained attention for zero-carbon emission goals in the transportation sector. However, in a conventional internal combustion engine (ICE), NH₃ combustion mechanism is still under investigation. In this paper, to further expand the knowledge on the adoption of NH₃ in ICEs, authors conducted NH₃/gasoline co-combustion experiments in a modified, 17.7:1 compression ratio, naturally aspirated spark-assisted CI engine with sub-chamber. The sub-chamber was chosen in order to enhance the combustion speed of NH₃. In addition, the sub-chamber was equipped with glow and spark plugs to overcome the high auto-ignition temperature of NH₃. Engine performance and NO_X emissions were studied under three different intake air temperatures. During the experiments, NH₃ content was increased gradually where the engine was run under lean conditions. Although higher NH₃ content was achieved compared to our previous work, increasing the intake air temperature resulted in decreased charging efficiency. In addition, corrosion was found on the piston ring after 120 h of operation, negatively affecting the engine performance. Furthermore, NH₃/gasoline co-combustion duration was shortened drastically with the influence of the sub-chamber, where the longest combustion duration under the present conditions was found to be 17°CA.