Effects of Mechanical Injector Replacement on Spray and Combustion Characteristics in an Agriculture Diesel Engine

Abstract

The objective of this study was to analyze through spray and engine experiments the effects of replacing mechanical injectors. The spray characteristics of the mechanical injectors of a used diesel engine and those of new mechanical injectors of the same model were compared. The injection quantity of the new injector was approximately 2-4% higher than that of the used injector owing to the deposit on the nozzle surface. The opening pressure of the used injector was 225 bar on account of the deterioration of the spring inside the injector. This pressure was lower than that of the new injector. The average spray penetration length of both injectors increased similarly up to 2 ms after injection. Owing to deposits on the nozzle surface, the spray angle of the used injectors tended to be smaller than those of the new injectors. The results of engine experiments showed that the new injectors recovered over 90% of engine torque and engine power on account of the increased fuel injection quantity. However, employing the new injectors caused heat loss and fuel consumption rate deterioration. The new injectors effectively reduced NOx and PM emissions by retarding the fuel injection timing and increasing the fuel injection pressure.