The diesel fuel mixture formation characteristics of a multi-hole diesel injector: a comparison with a single-hole diesel injector

摘要

The mixture formation process of a diesel spray between single- and multi-hole injectors was compared. Two injection quantities, 0.5 and 2.5 mg, were selected to also observe the difference of spray evolutions with respect to the injection quantity. The laser absorption scattering (LAS) technique was utilized to derive the mixture formation process in terms of equivalence ratio. The increase rate of injection rate for multi-hole injector was slower than that of single-hole injector, due to the slower injection pressure built-up process inside the sac volume. Therefore, the spray penetration development was slower for multi-hole injector. The spray angle with multi-hole injector was greater than that with single-hole injector, especially at the transient period right after SOI. However, the spray angle difference between two injectors decreased and became almost identical when the spray entered into quasi-steady state. The mixture formation of both injectors under injection quantity of 2.5 mg showed similar results at their corresponding end-of-injection (EOI) timing. Both injectors went through quasi-steady state injection which provided similar conditions for mixture formation process. However, for the injection quantity of 0.5 mg where the entire injection was a transient process, the mixture formation of multi-hole injector was poorer than that of single-hole injector. It was possibly due to the poorer air entrainment caused by the shorter penetration and lower sac pressure of the multi-hole injector.