Contribution of Optimum Nozzle Design to Injection Rate Control

The purpose of this paper is to discuss injection rate control of the nozzle for direct injection engines. This paper will focus on fuel flow analysis of the nozzle, a key component of Fuel Injection Systems (FIS). The optimum designed nozzle improves fuel flow efficiency and controls injection rate.

To meet emission regulations in 1990's, FIS are required to produce higher injection pressure and injection rate control which creates better fuel spray atomization and higher utilization of air. But the higher injection pressure makes injection rate control difficult. In particular, injection rate control by needle lift traveling control is difficult because fuel flow characteristics in the nozzle change with injection pressure and needle lift. Furthermore, the forced control of needle lift results in poor fuel spray atomization.

To control injection rate with good fuel spray atomization under high injection pressure, we analyzed the fuel flow characteristics and calculated them by using a computer model simulation. We designed the optimum nozzle configuration by utilizing these methods and confirmed their effects through experiments.