Study on the image recognition of ammonia ignition process induced by methanol micro-jet 2023-32-0067

Ammonia is regarded as a possible carbon-free energy source for engines, drawing more and more attention. However, the low burning velocity of ammonia inhibits its application. To improve the ignition energy by ignition chamber (pre-chamber) jet ignition seems to be a good solution. In this study, the jet-controlled compound ignition (JCCI) model was proposed to improve the ammonia premixed combustion, in which the ignition chamber was fueled with methanol, investigated by visualization method in a constant volume chamber. Jet flame image recognition and characteristic parameters determination is significant to the analysis of the jet flame propagation and combustion processes. In this study, jet flame image recognition approaches were investigated and compared. The Approach 1 as jet flame contour extraction method was applied to study the overall jet flame propagation. Approach 2 focuses on the jet flame variation of the adjacent images to recognition the jet ignition process, which is more conducive to paying attention to the instantaneous change of the ignition process. The jet ignition timings were determined and analyzed with the help of pressure rise rate (Method 1) and jet flame image characteristic parameter (Method 2), respectively. The jet ignition timing determined by Method 1 is 0.52ms later than that of the Method 2. The delay of jet ignition timing determined by jet flame image recognition is mainly due to the jet flame images information being less sensitive than that of pressure variation information. The difference turned to be smaller as the equivalent ratio increased. As the equivalent ratio increased from 0.8 to 1.2, the ignition delay times calculated by Method 2 were delayed by 20%, 7%, and 2% than that of Method 1, respectively. The study of jet flame image recognition of ammonia induced by methanol micro-jet ignition helps to understand the jet ignition and ammonia combustion process.