The advantages of diesel engines are high torque and good economic performance. The working process of a diesel engine has many similarities with that of a gasoline engine. Each working cycle also undergoes four strokes of intake, compression, work, and exhaust. However, since the fuel for diesel engines is diesel, its viscosity is larger than that of gasoline, it is not easy to evaporate, and its auto-ignition temperature is lower than that of gasoline. Therefore, the formation and ignition of combustible mixture are different from those of gasoline engines. The main difference is that the mixture in the cylinder of a diesel engine is compression-ignited rather than ignited. When the diesel engine is working, the air entering the cylinder is air. When the air in the cylinder is compressed to the end point, the temperature can reach 500-700 ° C, and the pressure can reach 40-50 atmospheres. When the piston approaches the top dead center, the fuel injector of the fuel supply system injects fuel into the cylinder combustion chamber at a very high pressure in a very short time. The diesel fuel forms fine oil particles, which are mixed with high-pressure and high-temperature air, and the combustible mixture burns by itself. The violent expansion produces explosive power and pushes the piston down to work. At this time, the temperature can reach 1900 to 2000 ° C, the pressure can reach 60 to 100 atmospheres, and the generated torque is very large, so the diesel engine is widely used in large diesel equipment.
The characteristics of the traditional diesel engine: thermal efficiency and economy are better. The diesel engine uses compressed air to increase the air temperature, so that the air temperature exceeds the self-ignition point of the diesel. At this time, it is injected into the diesel, diesel spray and air mixture while igniting and burning. . Therefore, diesel engines do not require an ignition system. At the same time, the fuel supply system of the diesel engine is relatively simple, so the reliability of the diesel engine is better than that of the gasoline engine. Due to the limitation of deflagration and the need for self-ignition of diesel, the compression ratio of the diesel engine is very high. The thermal efficiency and economy are better than that of the gasoline engine. At the same power, the torque of the diesel engine is large, and the rotation speed of the power is low, which is suitable for the use of the truck.
However, due to the high working pressure, the diesel engine requires high structural strength and rigidity of the relevant parts, so the diesel engine is relatively bulky and bulky; the diesel engine's fuel injection pump and nozzle have high manufacturing precision requirements, so the cost is high; in addition, the diesel engine works rudely. The vibration noise is large; the diesel oil is not easy to evaporate, and it is difficult to start when the cold car is cold in winter. Due to the above characteristics, the previous diesel engines are generally used on large and medium-sized trucks. Traditionally, diesel engines are relatively cumbersome, and their power-up indicators are not as good as gasoline engines (lower speed), noise and vibration are higher, and soot and particulate (PM) emissions are more serious, so they have rarely been favored by cars. Especially for the new development of small high-speed diesel engines, a number of advanced technologies, such as electronically controlled direct injection, common rail, turbocharging, and intercooling, have been applied to small diesel engines, and the shortcomings of the original diesel engines have been obtained. Better solution, and the advantages of diesel engines in terms of energy saving and CO2 emissions are all “thermal engines” that cannot be replaced by all heat engines including gasoline engines.