What is the working principle of a diesel engine?
2 Answers
Working principle of a diesel engine: A diesel engine compresses air to generate high heat, then injects atomized diesel fuel, which explodes and expands. The pressure directly acts on the piston, driving the piston to perform high-speed, non-uniform linear reciprocating motion along the cylinder. Through the crank-connecting rod mechanism composed of the piston pin, connecting rod, and crankshaft, the linear motion of the piston is converted into the rotational motion of the crankshaft, thereby outputting mechanical work. Below is an introduction to diesel engines: 1. The working process of a diesel engine shares many similarities with that of a gasoline engine. Each working cycle also goes through four strokes: intake, compression, power, and exhaust. However, since diesel engines use diesel fuel, which has higher viscosity than gasoline and is less prone to evaporation, and its auto-ignition temperature is lower than that of gasoline, the formation of the combustible mixture and the ignition method differ from those of gasoline engines. The main difference is that the mixture in a diesel engine cylinder is ignited by compression rather than by spark. 2. Compared to gasoline engines, diesel engines have advantages such as better fuel economy, lower nitrogen oxide emissions in exhaust gases, and high torque at low speeds. Due to their excellent environmental characteristics, they are highly regarded in European vehicles. As for drawbacks like smoothness and noise, these are no longer significant issues under Europe's advanced automotive industry. Currently, the performance and operating conditions of diesel engines are almost on par with those of gasoline engines.
I've been driving for many years and really appreciate the fuel efficiency of diesel engines. The working principle is actually not complicated, divided into four strokes: first is intake, where the engine piston moves downward, drawing in fresh air; then comes compression, where the piston moves upward to compress the air extremely tightly, raising the temperature above 500 degrees; next is fuel injection and combustion, at the peak of compression, the fuel injector sprays diesel into the cylinder, which ignites spontaneously upon contact with the hot air, the explosion forces the piston downward to generate power; finally, exhaust, where the piston moves upward to expel the waste gases. This cycle keeps repeating continuously. There's no spark plug, ignition relies entirely on compression heat, and the compression ratio is high, generally above 16:1, so energy utilization is excellent, allowing a tank of fuel to go much farther. The downside is it's a bit noisier, and when starting cold, it needs help from glow plugs. Understanding these points makes me pay more attention to fuel injection system cleanliness during maintenance.
