Carl Steinbeck, age 13, of Sioux City, Iowa, for his question:
HOW DOES A DIESEL ENGINE WORK?
Diesel engines have a high thermal efficiency, which means they have an ability to convert the stored chemical energy in the fuel into mechanical energy, or work. Cars and trucks with diesel engines burn cheap fuel and can perform heavy work under highly overloaded conditions. This is why diesel engines are favored for heavy duty work.
A diesel engine is a type of internal combustion engine that is used mainly for heavy duty work. A lot of the train locomotives used in the United States are powered by diesel engines, and you'll also find them in large freight trucks, buses, tractors and heavy road building equipment.
Diesel engines are also used to power ships and submarines. In small cities, you'll also find diesel engines running the generators of electric power stations.
Diesel engines burn fuel oils which require less refining and are cheaper than higher grade fuels such as gasoline. During the combustion process, the stored chemical energy in the diesel fuel is converted to thermal energy, or heat.
The temperature in each cylinder goes as high as 4,500 degrees Fahrenheit. This heat creates pressures of 1,500 pounds per square inch. The pressure pushes against the tops of the pistons, forcing them to the other end of their cylinders. The pistons are connected by a rod or other suitable connecting mechanism to a crankshaft which they turn. In this way, a diesel engine supplies rotary power to drive vehicles and other machines.
In order for the compressed air inside the cylinders to ignite the fuel, it must have a certain temperature. The degree to which the temperature of the air rises depends on the amount of work done by the piston in compressing it.
Near the end of the diesel engine piston's compression stroke, the fuel is injected into a cylinder. In order to have the fuel and air mix well, the fuel is injected under high pressure as a spray. Combustion usually starts just before the piston ends its compression stroke. The power of diesel engines can be increased by supercharging, or forcing air under pressure into the cylinders.
Diesel engines can be either four stroke cycle engines or two stroke cycle engines.
A German engineer named Rudolf Diesel invented the engine in 1893. His first engine exploded and almost killed him, but the accident proved that fuel could be ignited without a spark. He operated his first successful engine in 1897. Later a British engineer named Sir Dugald Clerk developed the two stroke diesel engine.