How Does a Diesel Engine Work?
2 Answers
Diesel engines operate by combusting diesel fuel within the cylinders to generate kinetic energy. This energy drives the crankshaft connecting rod mechanism attached to the pistons, producing reciprocating circular motion around the crankshaft to deliver power. A four-stroke diesel engine consists of four cycles: intake, compression, power, and exhaust. During the intake stroke, the piston moves from top dead center to bottom dead center, driven by the crankshaft, while the intake valve opens and the exhaust valve closes. As the piston moves downward, the volume above it increases, reducing the gas pressure inside the cylinder and creating a vacuum. With the intake valve open, the cylinder connects to the intake manifold, drawing fresh air into the cylinder. By the time the piston reaches bottom dead center, the cylinder is filled with fresh air. During the compression stroke, the piston moves from bottom dead center to top dead center with both intake and exhaust valves closed.
As someone in mechanics, I find the working principle of diesel engines quite fascinating: they rely solely on air compression for ignition, eliminating the need for spark plugs found in gasoline cars. Simply put, it's a four-stroke cycle—during the intake stroke, the cylinder draws in air; the compression stroke sees the piston forcefully compressing the air, with pressure soaring and temperatures exceeding 500°C; at ignition, the injector sprays a fine mist of diesel, which instantly combusts upon contact with the hot air, generating a powerful thrust; finally, the exhaust stroke pushes out the waste gases. This process is called compression ignition, with an ultra-high compression ratio of around 18:1 or more, achieving energy efficiency over 40%, compared to less than 30% in gasoline cars, making diesel engines more fuel-efficient and capable of longer ranges. Modern versions incorporate turbocharging to compress more air for increased horsepower and exhaust after-treatment systems to reduce emissions. During maintenance, remember to check the cleanliness of the fuel injectors.
