Diesel engine

A diesel engine is a type of internal combustion engine. It is often called a compression-ignition engine, or a CI engine. This name refers to how the engine starts the combustion process. In a petrol engine, a spark plug creates a spark to ignite the fuel. In a diesel engine, the heat from squeezed air starts the fire. This method allows the engine to be very efficient.

The mechanism of a diesel engine follows a specific sequence of steps. First, air is drawn into a chamber called a cylinder during the intake stroke. Next, the engine performs a compression stroke. During this stage, the piston squeezes the air very tightly. This mechanical compression causes the air temperature to rise significantly. Once the air is hot enough, atomized diesel fuel is injected into the combustion chamber. The intense heat causes the fuel to ignite instantly without a spark.

Engine designers use different cycles to manage how the engine operates. Some engines use a four-stroke cycle, while others use a two-stroke cycle. Diesel engines also manage power by changing the air-fuel ratio, known as lambda (λ). Instead of using a throttle to limit intake air, they change the amount of fuel injected. This often results in a high air-fuel ratio. Some engines also use exhaust gas recirculation, or EGR. This process involves combining fresh air with leftover gases from the exhaust to assist the cycle.

The history of this technology began with Rudolf Diesel. He was a German engineer and a student in Munich in 1878. He studied under Carl von Linde, who taught him about the Carnot cycle. Diesel wanted to build a heat motor that was much more efficient than steam engines. He published his ideas in an 1893 essay titled "Theory and Construction of a Rational Heat Motor." Although he faced many critics, Diesel successfully built several prototypes. His first prototype was built in Augsburg in 1893. By 1897, his third prototype achieved an effective efficiency of 26.2%.

Diesel engines are famous for their high thermal efficiency. This means they convert more heat energy into useful work than many other engines. Low-speed diesel engines used in large ships can reach efficiencies as high as 55%. This high efficiency is due to a high expansion ratio and a lean burn process. A lean burn uses excess air to help dissipate heat. While combined cycle gas turbines are more efficient, they are too large for most vehicles.

We see diesel engines in many massive and specialized machines. The world's largest diesel engines are 14-cylinder, two-stroke marine engines. These giants can produce a peak power of almost 100 MW. In the 21st century, diesel technology has even moved into the sky. Since the late 1990s, production of diesel engines for aircraft has increased. Between 2002 and 2018, over 5,000 diesel engines were delivered for light airplanes and unmanned aerial vehicles.

Today, diesel engines connect to many different industries and global systems. They have been used in submarines and ships since the 1910s. Later, they became common in locomotives, buses, trucks, and heavy farm equipment. They are also vital for electricity generation plants. In the European Union, diesel cars accounted for half of all new registrations at one point. However, because diesel emissions can be harder to control than gasoline, their use in the United States is mostly limited to large vehicles.