Characteristics of diesel engines

The advantages of diesel engines are high torque and good economic performance. The working process of diesel engines has many similarities with gasoline engines. Each working cycle also goes through four strokes: intake, compression, power, and exhaust. However, since the fuel used in diesel engines is diesel, its viscosity is greater than that of gasoline and it is not easy to evaporate, but its auto-ignition temperature is lower than that of gasoline. Therefore, the formation and ignition of the combustible mixture are different from those of gasoline engines. The main difference is that the mixture in the cylinder of the diesel engine is compression ignition, not ignition. When the diesel engine is working, air enters the cylinder. When the air in the cylinder is compressed to the end, the temperature can reach 500-700℃ and the pressure can reach 40-50 atmospheres. When the piston approaches the top dead center, the fuel injection nozzle of the fuel supply system sprays fuel into the cylinder combustion chamber at extremely high pressure in a very short time. The diesel forms fine oil particles and mixes with high-pressure and high-temperature air. The combustible mixture burns by itself, expands violently to produce explosive force, and pushes the piston downward to do work. At this time, the temperature can reach 1900-2000℃, and the pressure can reach 60-100 atmospheres. The torque generated is very large, so diesel engines are widely used in large diesel equipment.
Characteristics of traditional diesel engines: good thermal efficiency and economy. The diesel engine uses compressed air to increase the air temperature so that the air temperature exceeds the auto-ignition point of diesel. At this time, diesel is injected, and the diesel spray and air are mixed and ignited and burned by themselves. Therefore, the diesel engine does not need 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 restriction of explosion and the need for diesel self-ignition, the diesel engine has a high compression ratio. The thermal efficiency and economy are better than those of the gasoline engine. At the same time, under the same power, the diesel engine has a large torque and a low speed at maximum power, which is suitable for the use of trucks.
However, due to the high working pressure, diesel engines require all related parts to have high structural strength and rigidity, so diesel engines are relatively heavy and large in size; the manufacturing precision of diesel engine injection pumps and nozzles is high, so the cost is relatively high; in addition, diesel engines work roughly, with large vibration and noise; diesel is not easy to evaporate, and it is difficult to start when the car is cold in winter. Due to the above characteristics, diesel engines were generally used in large and medium-sized trucks in the past. Traditionally, diesel engines have been rarely favored by cars because they are relatively heavy, the power per liter index is not as good as that of gasoline engines (low speed), the noise and vibration are high, and the carbon smoke and particulate (PM) emissions are relatively serious. In particular, with the new development of small high-speed diesel engines, a number of advanced technologies, such as electronically controlled direct injection, common rail, turbocharging, intercooling and other technologies, have been applied to small diesel engines, so that the shortcomings of the original diesel engines have been better solved, and the advantages of diesel engines in energy saving and CO2 emissions are irreplaceable by all thermal engines including gasoline engines, making them "green engines".