柴油发动机外文翻译.doc

PAGE 5 外文原文 The Diesel Engine In 1892 Rudolf Diesel developed and obtained the German patent for the diesel engine. His goal was to create an engine that was highly efficient. Much more efficient than the gasoline engine that was invented in 1876 and was not very efficient at all, especially at that point in time. There are two main differences between a diesel engine and a gasoline engine: (1) A gasoline engine intakes a mixture of gas and air, compresses it and ignites the mixture with a spark. A diesel engine takes in just air, compresses it and then injects fuel into the compressed air. The heat of the compressed air lights the fuel spontaneously.(2) A gasoline engine compresses at a ratio of 8:1 to 12:1, while a diesel engine compresses at a ratio of 14:1 to as high as 25:1. The higher compression ratio of the diesel engine leads to better efficiency. Gasoline engines use either a carburetor or a fuel injection system to deliver the fuel to the cylinder. With a carburetor the fuel is mixed as it enters the intake manifold, long before it gets to the cylinders. In a fuel injection system the fuel is injected just before the intake stroke at the intake valve. Diesel engines use direct fuel injection (DI), that is to say the diesel fuel is injected directly into the cylinder. The diesel engine has no spark plugs. The air it takes in is compressed and the fuel is injected directly into the cylinder where the heat caused by the air compression ignites the fuel. In the old days this meant that it exploded and expanded very quickly, making a noisy engine. This is why most diesel cars were IDI (indirect injection); the rough behavior was fixed by injecting the fuel into a small pre-combustion chamber that is connected to the cylinder by a narrow passage. This slows down the explosion, as the gasses have to escape from through the narrow passage into the cylinder. This gives a softer bang and a smoother engine, but the gasses have to work harder, which lowers the effi