The influence of the last-post-injection strategy on the exhaust emissions

brake specific fuel consumption and the temperature rise behaviour were investigated on a diesel engine. Results show that both HC and CO emissions increase with the rise of post injection quantity. With the delay of post-injection timing

the HC emissions reach stable condition after initial increase

and the CO emissions decrease after initial increase. While the emissions of NOx and soot tend to decrease first and then increase moreover

the NOx emissions decrease by 9.8%～24.0% with last post injection and reduce with the increase of post injection quantity

while the soot emissions decrease with the delay of post injection timing of less than 70° after TDC

but show an opposite trend with more than 70° after TDC. The temperature of exhaust gas after the DOC can reach over 600 ℃ for DPF active regeneration when the post injection quantity is 14 mg or 17 mg with the injection timing of 80 to 140° after TDC and the maximum temperature at 100° after TDC. The energy efficiency of the DOC increases with the rise of post-injection quantity

and reaches stable conditions after initial increase with the delay of post injection timing. The energy utilization efficiency of DOC is within the range of 62.73% to 75.75% when the post injection timing is 80° to 140° after TDC

thus leading to a maximum energy efficiency of DOC at 100° after TDC. The results provide a valuable information for the development of DPF regeneration and control strategy.