Three-dimensional modeling and finite element analysis on the diesel engine piston is carried out in the paper. The distribution of temperature, stress and strain within piston at the rated conditions of the engine are obtained from the simulation. The calculated temperature is consistent with the results of the piston surface temperature which is obtained by hardness plug method, thus confirming the model's validity. The calculated maximum temperature is 374 °C and the minimum temperature is 144 °C. The maximum stress is 118MPa located between the piston skirt above the pin hole and the third ring groove. The maximum thermal strain appears at the piston top with the value of 6.29×10-3. Finally, the temperature simulation of the piston adopted oil-splashing cooling is implemented. It is proved that thermal load can be further reduced through cooling measure.
The simulation method was used to study the fuel supply and injection characteristics of diesel top clearance plunger pump. The results show that the top clearance plunger pump relative advance of fuel supply is larger than that of the traditional plunger, and it can achieve the purpose of injection advance when the oil pump operate at 600~1000rpm. Through optimizing the structure of top clearance plunger, the amount of the injection advance can become larger and the advanced range of speed is increased. After optimized, the BSFC (Brake Specific Fuel Consumption) is 4.3% lower than that before when the diesel engine matched the top clearance plunger, which shows its advantage especially in working at high-speed.
The simulation results shows that pilot injection, intake preheating, main injection advance angle have a big impact on ignition performance of diesel engine. After using pilot injection, the average cylinder pressure and temperature, and the accumulated heat release increased, ultimately the fuel efficiency had been improved. By using the intake preheating, combustion efficiency had been improved for combustible mixture gas formed easily and combustion conditions significantly improved in cylinder. Besides, an appropriate main injection advance angle could improve the combustion of ignition delay period and increased the engine power and fuel efficiency.
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