About Diesel Engine

The advantages of diesel engines are large torque and good economic performance. The working process of a diesel engine has many similarities to that of a gasoline engine. Each working cycle also experiences four strokes of intake, compression, work, and exhaust. However, because the fuel used in diesel engines is diesel, it has a higher viscosity than gasoline and is not easy to evaporate, and its spontaneous combustion temperature is lower than that of gasoline. Therefore, the formation and ignition of combustible mixtures are different from those of gasoline engines. The main difference is that the mixture in the cylinder of a diesel engine is compression ignited instead of ignited. When a 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 is close to the top dead center, the fuel injector of the fuel supply system injects fuel into the combustion chamber of the cylinder at a very high pressure in a very short time. The diesel 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 force and pushes the piston down to do work. At this time, the temperature can reach 1900-2000℃, the pressure can reach 60-100 atmospheres, and the generated torque is very large. Therefore, diesel engines are widely used in large diesel equipment.
The characteristics of traditional diesel engines: good thermal efficiency and economy. Diesel engines use compressed air to increase the air temperature, so that the air temperature exceeds the spontaneous ignition point of diesel. At this time, it is injected into diesel, diesel spray and air while self-igniting and burning. . Therefore, the diesel engine does not need an ignition system. At the same time, the fuel supply system of diesel engines is relatively simple, so the reliability of diesel engines is better than that of gasoline engines. Because it is not restricted by deflagration and the need of diesel spontaneous combustion, the compression ratio of diesel engine is very high. Both thermal efficiency and economy are better than gasoline engines. At the same time, under the same power situation, diesel engines have large torque and low speed at maximum power, which is suitable for trucks.
However, diesel engines require high structural strength and rigidity due to high working pressure, so the diesel engines are relatively heavy and bulky; the fuel injection pumps and nozzles of diesel engines require high manufacturing precision, so the cost is high; in addition, diesel engines work rough , Large vibration and noise; diesel is not easy to evaporate, difficult to start when the car is cold in winter. Because of the above characteristics, diesel engines were generally used in large and medium-sized trucks in the past. Traditionally, diesel engines have been seldom favored by cars because they are relatively heavy, have lower power indicators than gasoline engines (lower speed), higher noise and vibration, and more serious emissions of soot and particulates (PM). Especially 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, etc., can be applied to small diesel engines, so that the original shortcomings of diesel engines have been obtained. A better solution, and the advantages of diesel engines in terms of energy saving and CO2 emissions cannot be replaced by all heat engines, including gasoline engines, and become a "green engine"