Effect of oxygen concentrations in intake air on combustion characteristics of ammonia direct injection SI engine
Cheolwoong Park, Ilpum Jang, Gyeongtae Park, Chanki Min, Minki Kim, Yongrae Kim, Young Choi
Abstract
• Combustion stability is improved by adding oxygen to the intake air. • Additional efficiency improvement is not significant with a further increase in oxygen to 30 %. • Adding oxygen has a greater impact on ignition delay than the overall combustion duration. • As the oxygen is introduced, NO x increases, and N 2 O and unburned NH 3 decrease. • Adding oxygen improves ignition delay and overall combustion speed. The emission of unburned ammonia, which is hazardous to the human body, is a top priority in engines that use ammonia as fuel. Because improving combustion speed is the most effective method to increase thermal efficiency and reduce exhaust gases, such as unburned ammonia, adding oxygen to the engine’s intake manifold was considered to increase the combustion speed of ammonia. In high-speed operation conditions of 2000 rpm or more and low-load operation conditions of 1500 rpm, stable operation is possible only by adding hydrogen due to the slow combustion rate of ammonia. In the present study, the operability was confirmed and the performance was compared by supplying oxygen without adding hydrogen. The addition of hydrogen during ammonia combustion only had a significant effect on improving ignition delay. At the same time, the addition of oxygen significantly improved not only ignition delay but also overall combustion speed, thereby improving combustion stability and thermal efficiency.