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The tiny and normal injection quantity instances usually happen under the multi-injection strategy condition to restrain the uncontrollability of the ignition timing of the homogeneous charge compression ignition (HCCI) combustion concept. Meanwhile, instead of the traditional and fundamental single-hole diesel injector, the axisymmetric multi-hole injectors are usually applied to couple with the combustion chamber under most practical operating conditions. In the current paper, the internal flow and spray characteristics generated by single-hole and multi-hole (10 holes) nozzles under normal (2 mm3/hole) and tiny (0.3 mm3/hole) injection quantity conditions were investigated in conjunction with a series of experimental and computational methods. High-speed video observation was conducted at 10000 and 100000 fps under the condition of 120 MPa rail pressure, 1.5 MPa ambient pressure, room temperature, and nitrogen environment to visualize different spray properties.

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.