How Does a Diesel Engine Work?
2 Answers
Diesel engine working principle is as follows: 1. During the intake stroke, the diesel engine inhales pure air. When the compression stroke is completed, diesel fuel is pressurized to over 10MPa by the fuel injection pump and injected into the cylinder through the fuel injector, where it mixes with the high-temperature compressed air in a very short time to form a combustible mixture. 2. Diesel engines have a high compression ratio (generally 16-22). When compression is completed, the air pressure in the cylinder can reach 3.5-4.5MPa, while the temperature can reach 750-1000K (whereas in a gasoline engine at this stage, the mixture pressure would be 0.6-1.2MPa and the temperature would reach 600-700K), significantly exceeding the auto-ignition temperature of diesel. 3. After being injected into the cylinder, the diesel fuel mixes with the air and spontaneously ignites and burns almost immediately. The pressure in the cylinder rapidly rises to 6-9MPa, and the temperature also increases to 2000-2500K. Under the push of the high-pressure gas, the piston moves downward, driving the crankshaft to rotate and perform work. The exhaust gas is then discharged into the atmosphere through the exhaust pipe.
The working principle of diesel engines is quite straightforward. I find driving a diesel vehicle on highways quite exhilarating. Unlike gasoline engines that rely on spark plugs for ignition, diesel engines first draw air into the cylinder and compress it fiercely to a high-temperature, high-pressure state. Then, fuel is injected, which spontaneously ignites and explodes. This pressure drives the piston downward, subsequently rotating the crankshaft to generate power. The entire process is direct and fuel-efficient. Although the noise is a bit louder, the power is robust, making it particularly suitable for long-haul cargo transport or off-roading. When I drive in mountainous areas, it’s very reliable—its high thermal efficiency allows for long-distance travel. Simply put, it’s a cycle of intake, compression, fuel injection, combustion, and piston push, repeated over and over. This design is simple and durable, requiring no additional ignition system, which saves a lot of maintenance hassle. Modern diesel engines have also improved emission treatment, making them quite environmentally friendly.
