What is the working principle of a diesel engine?

[VanRylee]

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.

[DelTeagan]

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.

[GabrielaLee]

As a car enthusiast, the working principle of diesel engines is truly fascinating. The core lies in compression ignition: unlike gasoline engines that use spark plugs, it first draws in air and compresses it to a high-pressure, high-temperature state; the compression ratio typically ranges between 14-25:1, which improves thermal efficiency; diesel fuel self-ignites and explodes at high temperatures, driving the piston. The entire process is divided into four steps: intake, compression, combustion, and exhaust. Combustion is an instantaneous burst of power, triggered by high compression, with the fuel injection system precisely controlling the amount and timing to ensure self-ignition. The advantages are fuel efficiency and strong low-speed torque, making it suitable for large vehicles; the disadvantages are higher particulate emissions, requiring DPF after-treatment. Understanding these details helps in weighing cost-effectiveness when choosing a car, such as opting for more power but slightly higher noise levels.

[LaAiden]

I've seen plenty of diesel engine issues during repairs, so understanding the working principle is essential. Simply put, it's compression ignition: the piston moves down to intake air; moves up to compress air above 300°C, then diesel is injected for spontaneous combustion, pushing the piston down to generate power; finally, exhaust clears the waste gas. Spontaneous combustion relies on high compression ratio—no spark plug, just heat-triggered explosion. The fuel injector is critical—clogging or wear can affect ignition, leading to weak power or black smoke. Key maintenance checks include injection pressure and air filter; poor compression makes starting difficult. Grasping the principle makes daily maintenance more cost-effective and efficient, like shorter oil change intervals.

[VanValerie]

Diesel engine technology is uniquely designed, invented by Germany's Rudolf Diesel. The working principle is based on the four-stroke cycle: intake stroke sucks in air; compression stroke pressurizes and heats the air; high-temperature air ignites the injected diesel fuel for combustion; then exhaust stroke expels the waste gases. The core feature is self-ignition without a spark system, relying on compressing air to the extreme for ignition. With high compression ratios reaching over 20:1, thermal energy is more thoroughly converted into mechanical energy, resulting in lower fuel consumption. It is widely used, from trucks to small boats. Understanding this principle explains why diesel vehicles are durable but noisy, and why preheating during daily starts ensures smoother operation.

[McAddyson]

Choosing a diesel car is for its fuel efficiency and high performance, with a working principle different from gasoline engines. Gasoline engines use spark ignition, while diesel engines rely on compression ignition: air is compressed to an extremely high temperature to ignite the diesel, providing strong piston thrust during the combustion stroke. The higher compression ratio (14-18:1 compared to gasoline's 8-12:1) reduces heat loss, achieving 30-40% efficiency, making it more fuel-efficient and cost-effective. The process involves four steps: intake, compression, combustion, and exhaust. Combustion is precisely controlled by fuel injection at the auto-ignition point. Advantages include strong low-speed torque and better climbing ability, while drawbacks include higher noise and slower cold starts. From an environmental perspective, emissions require filtration, but understanding the simple principles helps make wiser car choices.