[1] Fuel Injection Rate Control (1) Main Injection a. Same as conventional fuel injection. (2) Pilot Injection a. Pilot injection is the injection of a small amount of fuel prior to the main injection. Main Injection Pilot Injection Q000110E b. While the adoption of higher pressure fuel injection is associated with an increase in the injection rate, the lag (injection lag) that occurs from the time fuel is injected until combustion starts cannot be reduced below a certain value. As a result, the quantity of fuel injected before ignition increases, resulting in explosive combustion together with ignition, and an increase in the amount of NOx and noise.
Therefore, by providing a pilot injection, the initial injection rate is kept to the minimum required level dampening, the explosive first-period combustion and reducing NOx emissions. TDC Combustion Process Small Injection Amount Prior to Ignition High Injection Rate Pilot Injection Improvement Injection Rate Large Pre-mixture Combustion (NOx, Noise) Small Pre-mixture Combustion Heat Generation Rate Ignition Delay Q000111E 30