| The transient characteristics of high injection pressure diesel fuel sprays have been investigated by sequential high-speed photographic images. Measurement of spray tip penetration length and spray angle were conducted based on the spray images, and the spray Sauter mean diameter was calculated by using a light extinction method.; Two fuel injection systems have been constructed for spray visualization experiments: one is a hydraulic unit injector system, which produces high injection pressure sprays; the other is a common rail injector system, which issues multiple injection sprays. Experiments were conducted by using different nozzles under different operating conditions to investigate the effects of injection pressure, nozzle inlet condition, nozzle injection angle, nozzle hole size, and multiple injection strategy on spray characteristics. To find the relationships between the spray characteristics and combustion emissions, the spray experiments used the same conditions as for a set of engine tests performed in a different project. The spray chamber density was adjusted under room temperature to match the combustion chamber density at the start of injection.; The results from the hydraulic unit injector show that a higher injection pressure produces a longer spray tip penetration length, a narrower spray angle, and a smaller overall average SMD. The spray with a smaller SMD generates higher NO{dollar}sb{lcub}rm x{rcub}{dollar} and lower particulate. The sharp-edged inlet (SEI) tip produces a wider spray angle and a smaller SMD, but needs a higher injection pressure to maintain the same fuel rate as the rounded-inlet (RI) tip under the same injection duration. The 140{dollar}spcirc{dollar} injection angle nozzle produces narrower spray angle and larger SMD sprays because of higher asymmetric internal flow compared with the 125{dollar}spcirc{dollar} nozzle. The smaller hole size nozzle produces a shorter penetration length, a wider spray angle, and a smaller average SMD.; Results from a common rail injector show that a double injection 50(10)50 (50% mass injected, 10{dollar}spcirc{dollar} CA dwell, 50% mass injected) spray has a smaller overall average SMD compared with a single injection spray, and also reduces the particulate and NO{dollar}sb{lcub}rm x{rcub}{dollar} emissions at the same time. |
