The Study Of Fuel Injection System Fault Impact Law To Rotational Speed And Exhaust Temperature Of Diesel Engine

As the core of the diesel engine system, fuel injection system which components work in the environment of high temperature, high pressure and high-impact, is one of the diesel engine parts that the fault frequency is the highest. The rotational speed and exhaust temperature of diesel engine can reflect the combustion of the fuel in the cylinder. In the running process of diesel engine, we can understand the working status of fuel injection system timely and effectively through analyzing the changes in the characteristics and laws of the rotational speed and exhaust temperature.This paper adopts the method of preinstalling fault, and carries out a detailed study that the faults have some influences to the two operation parameters (the rotational speed and exhaust temperature) when three common faults (Injection pressure abnormality, Fuel supply advance angle abnormality, Cylinder misfire) of the fuel injection system in diesel engine are taking place. Obtaining the laws that the rotational speed and exhaust temperature change with injection pressure, fuel supply advance angle and misfire cylinder number. And providing technical support for the fault diagnosis of fuel injection system.In the simulation test of injection pressure abnormality, when change the injection pressure of a diesel engine cylinder, along with the increase of injection pressure (16MPa～26MPa), the rotational speed of the diesel engine appears the trend of first increasing then decreasing, the rotational speed fluctuating value of the diesel engine appears the trend of first decreasing then increasing. The cylinder exhaust temperature and its fluctuating value appear the trend of first decreasing then increasing. The test show that the best fuel injection pressure value of its nozzle is20MPa.In the simulation test of fuel supply advance angle abnormality, when change of diesel engine fuel supply advance angle, along with the increase of fuel supply advance angle (14°CA～20°CA), the rotational speed of the diesel engine is first increasing then decreasing, the rotational speed fluctuating value of the diesel engine is first decreasing then increasing. The total exhaust temperature of diesel engine is always decreasing, its fluctuating value is first decreasing then increasing. The test show that the best fuel supply advance angle of bench test diesel engine is17°CA.In the simulation test of cylinder misfire, along with the misfire cylinder number increasing, when the diesel engine running in low load, the total exhaust temperature of diesel engine is increasing; when the diesel engine running in high load, originally the total exhaust temperature of diesel engine is increasing, then the total exhaust temperature is decreasing sharply. Along with the misfire cylinder number increasing, the fluctuating value of the total exhaust temperature and the rotational speed is increasing, the greater the load, the more fluctuating value increases signally.