The combustion of diesel fuel in the cylinder is a complex physico-chemical process, with the degree of improvement in the combustion process, which directly affects the performance, thermal efficiency and lifetime of diesel engines, divided into four stages:
1. The combustion preparation phase (deflammation period) is the combustion preparation phase between the injection of fuel fuel and the start of the fire. During this phase, the fuel needs physical preparation processes such as heating, evaporation, diffusion and mixing with air currents, as well as chemical preparation processes such as decomposition and oxidation。
2. The velocity-fire phase begins at the start of the fire and ends at the highest pressure in the cylinder. When a small amount of diesel fuel is on fire, the amount of flammable hybrid gas continues to increase the rapid spread of the flames, speed of combustion and high heating rates. Pressure and temperature in the cylinders have increased dramatically. However, when the pressure rises too fast, the impact load on the rotor coil is very high, accompanied by sharp knocks, which should be limited in the case of diesel engines. The maximum pressure growth rate should not exceed 292 kpa ~ 588 kpa/1° (argument angle) in order to stabilize the operation of diesel engines。
The main combustion phase (suspension period) is the main combustion phase from the outbreak pressure point to the maximum combustion temperature point. This phase is characterized by the end of the oil spill, during which most of the fuel was burned, releasing about 80 per cent of the total heat and raising the gas temperature to its highest point. However, the pressure in the cylinder has not changed significantly due to the downsliding of the pistons and the increased volume of the cylinder. Oil supply ends at this stage。
4. The post-combustion phase ranges from the highest burning temperature point to the end of the combustion. At this stage, oxygen has been consumed in such a way that the fuel sprayed in the later stages does not have enough oxygen to mix with it for combustion, with further movement of the pistons, and with a significant decrease in pressure and temperature in the cylinders, which exacerbates the conditions of combustion, resulting in incomplete fuel combustion, exhausting black smoke, increasing the heat load of the parts concerned, affecting the economic and operational life of the diesel engines, so that combustion in the latter period should be minimized。
