EXPERIMENTAL AND NUMERICAL INVESTIGATION OF DUCTED SPRAY WITH DUAL INJECTION STRATEGIES

Ducted fuel injection (DFI) is a newly established technology showing great potential in breaking the soot/NO_x trade-off. Multiple-injection strategy is also seen as a possible way to reduce soot and NO_x emissions simultaneously. However, the applicability of these approaches is not fully understood. To address thism, the spray characteristics of DFI technology coupled with a dual-injection strategy were studied. Results showed that during the injection interval (the interval between two injections), ambient gas continues to flow into the duct due to the pressure difference between the duct inside and outside, which increases the velocity of the second injection. The spray penetration length development of ducted spray is faster than that of free spray in both the first and the second injection events. During the first injection, the distribution of the equivalence ratio of ducted spray is more uniform than free spray, and the peak value of the equivalence ratio of ducted spray is lower than that of free spray. Compared to the first injection, in the second injection, when the radial equivalence ratio distribution of ducted spray is equivalent to the that of free injection, the path of spray traversed is shorter.