Effect of single and split injection on combustion process of diesel spray injected into 2D piston cavity

The flame characteristics of wall-impinging diesel fuel spray at single injection and split injection strategies were investigated in a high-temperature high-pressure constant volume combustion vessel. The 2D piston cavity has been used to form the impingement spray flame and the two-color method has been used to analyze the flame process. Results reveal that 2nd ignition delay can be defined in a specific area surrounded by single and split injections when the 1st injection proportion is from 25% to 75%. The KL factor and distribution area of a single injection are smaller than that of a split injection at EOI + 0.2 ms. The soot oxidation area is far away from the wall surface. However, the soot formation area is mainly concentrated along the cavity groove. The soot oxidation area proportion plays a decisive role in the emission of soot. The split injection interval has a key role in the soot formation dominant process at the initial stage of ignition. The initial mean flame temperature changes slightly, the mean flame temperature decreases earlier, the soot oxidation degree becomes higher, no interaction or small interaction between the 1st and 2nd injection, and the maximum degree of soot formation and oxidation dominant process occur when the 1st injection proportion equals 50%. The mean flame temperature drop time of the single injection is advanced. The total flame area and the soot formation and oxidation dominant process before and after EOI + 0.2 ms were also discussed. The total flame area of split injection is larger than single injection after EOI + 0.2 ms.