CLASSIFICATION OF ENGINES

CLASSIFICATION OF ENGINES

Engines for automotive and construction equipment may be classified in several ways: type of fuel used, type of cooling employed, or valve and cylinder arrange-ment. They all operate on the internal combustion principle. The application of basic principles of construction to particular needs or systems of manu-facture has caused certain designs to be recognized as conventional.
The most common method of classification is based on the type of fuel used; that is, whether the engine burns gasoline or diesel fuel.

GASOLINE ENGINES VERSUS DIESEL ENGINES


Mechanically and in overall appearance, gasoline and diesel engines resemble one another. However, many parts of the diesel engine are designed to be somewhat heavier and stronger to withstand the higher temperatures and pressures the engine generates. The engines differ also in the fuel used, in the method of introducing it into the cylinders, and in how the air-fuel mixture is ignited. In the gasoline engine, we first mix air and fuel in the carburetor. After this mixture is compressed in the cylinders, it is ignited by an electrical spark from the spark plugs. The source of the energy producing the electrical spark may be a storage battery or a high-tension magneto.
The diesel engine has no carburetor. Air alone enters its cylinders, where it is compressed and reaches a high temperature because of compression. The heat of compression ignites the fuel injected into the cylinder and causes the fuel-air mixture to burn. The diesel engine needs no spark plugs; the very contact of the diesel fuel with the hot air in the cylinder causes ignition. In the gasoline engine the heat compression is not enough to ignite the air-fuel mixture; therefore, spark plugs are necessary.