Diesel Engines Explained: From Principle to Application

1. Principle of operation of diesel engines

The heart of the diesel engine lies in its unique compression ignition mechanism. Unlike gasoline engines, which rely on spark plugs to ignite the mixture, diesel engines compress the air in the cylinder through the piston, causing its temperature to rise sharply to the spontaneous ignition point of diesel. When the air is compressed to the limit, the injector will be a high-pressure mist of diesel fuel sprayed into the cylinder, diesel fuel in the high-temperature, high-pressure environment, rapid spontaneous combustion, pushing the piston down to do work. This process does not require an external ignition source, and relies only on physical compression to realize energy conversion, giving the diesel engine a higher thermal efficiency.

2. Core differences from gasoline engines

The differences between diesel engines and gasoline engines are not only reflected in the ignition method, but also throughout the design process:

(1) Ignition: Diesel engines rely on compression ignition, while gasoline engines rely on spark plug ignition. This difference leads to a simpler structure for diesel engines (no ignition system required), but with higher requirements for fuel injection accuracy and compression ratio.

(2) Fuel supply: diesel engines use direct injection technology, fuel is injected into the cylinder at the end of the compression stroke; gasoline engines need to be pre-mixed with air and fuel to form a homogeneous mixture before ignition.

(3) Performance comparison: diesel engine thermal efficiency is usually more than 30% higher than gasoline engine, fuel consumption is 30% lower, and low-speed torque is abundant, suitable for heavy-duty conditions. However, its noise and vibration are relatively large, and the starting speed is slow, which needs to optimize the NVH performance through the balance shaft and sound insulation materials.

3. History of diesel engine development

(1) Invention process

At the end of the 19th century, Rudolf Diesel, a German engineer, devoted himself to solving the problem of inefficiency of steam engine. He put forward the theory of “compression ignition”, which was patented in 1892. After five years of experimentation, Rudolf Diesel successfully developed the first practical diesel engine in 1897. The power of this single-cylinder engine was only 14 watts, but the thermal efficiency reached 26%, far more than the same period of the steam engine. This invention laid the foundation of modern diesel technology.

(2) Technology Evolution

Turbocharging technology: In 1905, the Swiss engineer Alfred Büchi (Alfred Büchi) put forward the concept of exhaust gas turbocharging, and was first applied to marine diesel engines in 1925. By recovering exhaust gas energy, this technology significantly increases air intake and power, enabling diesel engines to produce higher power at the same displacement.

Fuel Injection System: In 1927, Bosch mass-produced a mechanical injection pump, which realized the precise control of fuel injection. Subsequently, the rise of electronically controlled injection technology (such as common rail injection) further optimized combustion efficiency and reduced emissions.

(3) Expansion of Industry Applications

1903: The first diesel truck was introduced, marking the official entry of diesel engines into the field of road transportation.

1913: diesel locomotives put into operation, with high torque and low fuel consumption advantages, quickly become the main force of railroad freight.

1920s: diesel engines were popularized in the field of agricultural machinery and ships, promoting the modernization of global agriculture and the development of maritime transport.

After the oil crisis in the 1970s: diesel vehicles are favored for their fuel economy, and the market share in Europe has increased significantly, with diesel cars accounting for more than 50% in some countries.

4. The main application areas of diesel engines

(1) Automobile field

Heavy-duty vehicles: trucks, buses and other commercial vehicles are highly dependent on diesel engines.

Passenger cars: in the European market, diesel cars once occupied half of the country.

(2) Ship power

More than 90% of the world's civilian ships use diesel engines as propulsion systems.

(3) Construction Machinery

The core power source of excavators, loaders, bulldozers and other construction machinery are diesel engines.

(4) Power generation and emergency power

Diesel generator sets are important backup power sources for hospitals, data centers and remote areas.

(5) Agricultural Machinery

Agricultural machinery such as tractors and harvesters widely use diesel engines.