Diesel

Diesel engines, developed by Rudolf Diesel, rely on the heat of combustion of the fuel. Fuel is injected into the combustion chamber in an atomized spray at the end of the compression stroke after air has been compressed to 450–650 psi and has reached a self-ignition temperature due to compression of at least 500°C. This temperature ignites the fuel and initiates the piston’s power stroke. The fuel is injected at about 2,000 psi to ensure good mixing. Diesels are expensively used in truck transport, rail trains, and marine engines. They are being used more in automobiles. In addition, they are employed in industrial and commercial stationary power plants. Fuels for diesels vary from kerosene to medium residual oils. The choice is dictated by engine characteristics, namely, cylinder diameter, engine speed, and combustion wall temperature. High speed small engines require lighter fuels and are more sensitive to fuel quality variations. Slow-speed, larger industrial and marine engines use heavier grades of diesel fuel oil. Ignition qualities and viscosity are important characteristics that determine performance. The ignition qualities of diesel fuels may be assessed in terms of their cetane numbers or diesel indices.