Abstract:

 Nozzle internal flow significantly affects the spray breakup, combustion and emissions of an internal combustion engine. The characteristics of internal flows in a nozzle and the corresponding diesel spray primary breakup during the initial stage were investigated through a single transparent nozzle by using a high-speed microscopic technique to capture the interaction process between gas-bubbles and liquid films. Numerical simulation was used to analyze the coupling process between the bubbles and thin fuel films with probing the velocity field and clarify the formation mechanism of the spray formation and its breakup process. The results show that the residual liquid fuel volume, the fuel properties, the strength of pressure shock wave, and the interaction between gas-bubbles dominate the spray morphology. Under low injection pressure, the gas-bubbles store less energy, and lead to the formation of mushroom-shaped spray. When injection pressure is high, the gas-bubbles save more energy, effectively promote spray atomization, and form a drum-shaped spray.

Key words: internal combustion engine ,  energy conservation and emission reduction ,  fuel combustion , spray morphology ,  bubble , primary breakup ,  spray