Matt Cooper, age 15 of Hattesburg, Miss., for his question:
WHEN WAS THE FIRST DIESEL ENGINE MADE?
A diesel engine is a type of internal combustion engine used chiefly for heavy duty work. The engine is often used to power ships and run the generators of electric power stations. A German engineer named Rudolf Diesel invented the engine in 1893, almost 100 years ago.
Diesel's first engine exploded and almost killed him, but he proved that fuel could be ignited without a spark. He operated his first successful engine in 1897.
Diesel engines have what is called a high thermal efficiency. This is an ability to convert the stored chemical energy in the fuel into mechanical energy, or work.
A diesel engine burns cheap fuel and can perform heavy work under highly overloaded conditions. This is why they are used for heavy duty work, such as powering locomotives, buses and large trucks.
The diesel engine is a compression ignition engine. When air confined in a cylinder is suddenly compressed, the temperature of the air rises.
In a diesel engine, each piston compresses air in a cylinder. Fuel is then injected into the cylinder and the very high heat of the air makes it ignite in an explosion.
Diesel engines burn fuel from oil that requires less refining and are cheaper than higher grade fuels such as gasoline. During the combustion process, the stored chemical energy in the fuel is converted to thermal or heat energy.
In a diesel engine, the temperature in each cylinder rises as high as 4,500 degrees Fahrenheit. This extremely high temperature creates pressures of 1,500 pounds per square inch and it pushes against the tops of the pistons, forcing them to the other end of their cylinders. The pistons are connected by rods or other suitable connecting mechanisms to a crankshaft that they turn.
There are two main types of diesel engines: the four stroke cycle engine and the two stroke cycle engine.
In a four stroke engine, the first downstroke draws air into the cylinder and the first upstroke compresses the air. The second downstroke is the power stroke while the second upstroke exhausts the gases produced by combustion.
The four stroke engine requires exhaust and air intake valves.
In a two stoke engine, the exhaust and intake of fresh air happen through openings in the cylinder near the end of the down, or power stoke. The one upstroke is the compression stroke. Valves are not needed in the two stroke engine.