E. Fuel Injection Rate Control a. Main Injection Same as conventional fuel injection. b. Pilot Injection ‡ Pilot injection is the injection of a small amount of fuel prior to the main injection. 1EMR-RNIGXMSR 4MPSX-RNIGXMSR 5) ‡ 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 in- crease 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. 8(' 'SQFYWXMSR 4VSGIWW 7QEPP-RNIGXMSR%QSYRX 4VMSVXS-KRMXMSR ,MKL-RNIGXMSR 6EXI 4MPSX-RNIGXMSR -RNIGXMSR6EXI -QTVSZIQIRX 0EVKI4VIQM\XYVI 'SQFYWXMSR 23\2SMWI 7QEPP4VIQM\XYVI 'SQFYWXMSR ,IEX+IRIVEXMSR 6EXI -KRMXMSR(IPE] 5) -25-