Reasons for Uneven Fuel Supply of Diesel Generator Set Fuel Injection Pump

What are the reasons for the uneven fuel supply of the fuel injection pump of a diesel generator set? First of all, the debugging state is different from the operating conditions. It is used under the conditions of 500～700℃ and pressure 3～5MPa, there is a big difference between the two. When the locomotive is operating, the temperature of the fuel injection pump and the fuel injector are both around 90°C, which will also cause the viscosity of the diesel to decrease, so the internal leakage of the plunger and needle valve assembly increases, and the amount of oil return is also greater than during debugging. According to the measurement, the actual amount of fuel injected into the cylinder by the fuel injection pump is only about 80% of the test bench debugging volume. Although the fuel pump debugging personnel will consider this factor, it is impossible to accurately grasp it.

Due to the difference in the degree of wear or airtightness of the liner piston and the valve mechanism, the temperature and pressure of each cylinder after compression will also be different. Even if the fuel injection pump has been debugged on the test bench, after it is installed in the diesel generator, the fuel supply of each cylinder will be uneven. Secondly, there is uneven fuel supply during commissioning. When the fuel injection pump is commissioned on the test bench, it is required that the unevenness of the fuel supply of each cylinder at the rated speed should be less than 3%. During the actual debugging process. Since the length, shape, and diameter of the fuel injector and high-pressure fuel pipe dedicated to the test bench cannot be exactly the same as the original machine, and the difference in debugging technology, after the fuel injection pump is installed, the actual amount of fuel injected into the cylinder is often uneven ＞3%.

Finally, the uneven fuel supply caused by the failure of the machine parts. After long-term use of the locomotive, due to the loosening of the driving coupling of the fuel injection pump or the excessive clearance, the driving gear is worn and the backlash increases, which will also affect the uniformity of the fuel supply of each cylinder. In addition, leakage of high-pressure oil pipe joints due to frequent vibration or insufficient tightening, and excessive tightening force may cause the joint metal to fall off and block the oil pipes, which will also cause uneven oil supply in each cylinder. In addition, among fuel injection pumps and governor springs, the plunger springs are the ones with stronger force, greater deformation, and higher working frequency. So its breaking frequency is also higher. The lighter fuel injection volume is reduced, the fuel injection volume of each cylinder is uneven, the fuel injection interval time of each cylinder is out of tolerance, and the fuel injection start time is delayed; the heavy fuel supply is intermittent or even unable to supply.

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