【正文】 天津職業(yè)技術師范大學 2021屆本科生畢業(yè)設計 Engine Fundamentals Automobiles have been operated successfully by electric motors ,steam engines ,and internal bustion engines .The internal bustion engine burns fuel within its cylinders and converts the expanding force of the burning fuel ,or bustion, into a rotary force used to propel the vehicle. There are several types of internal bustion engines: twoand fourcycle reciprocating piston engines ,gas turbine engines .However ,fourcycle reciprocating engines have been refined to such a degree that they have almost plete dominance of the automotive field .Engines of other types are described in Chapter 18 ,Diesel and Other Engines. Many things are demanded of an engine used to propel an automobile. Some of the requirements are: （ 1） Ease of starting. （ 2） Reliability. （ 3） Power. （ 4） Responsiveness. （ 5） Economy in fuel ,oil ,and ,repairs. （ 6） Ease of handling. （ 7） Quiet operation. Some of these factors conflict .For example ,a great amount of power can be had from an engine of sufficient size, but a supersize engines is not economical to operate .Therefore ,all automobile engines are a promise in order to obtain the desirable bination of performance and economy. Engine fuels Internal bustion engines can be made to operate on almost anythi ng that can be converted into a bustible gas, such as wood ,coal, alcohol, vegetable oils, mineral oils, etc. However, because of convenience, a variety of petroleum products are monly used as fuel :gasoline, kerosene ,fuel oil ,liquefied petroleum gas (LPGas) ect. What kerosene ,fuel oil ,or LPGas is used it is necessary to alter the design of the engine to achieve efficient operation. 天津職業(yè)技術師范大學 2021屆本科生畢業(yè)設計 Engine Deign Gasoline engines used in automotive vehicles are of two basic types :fourcycle engines and twocycle engines .Either type may be watercooled ,or aircooled .Four ,six, and eightcylinder engines are mon However, three, five, ten ,and twelvecylinder engine are available. Almost all automobile engines have more than one cylinder. These cylinders can be arranged in an inline ,opposed ,or Vtype configuration. Engines for other purpose ,such as aviation, are arranged as radial, inverted inline ,inverted V, and Xshaped configurations. Reciprocating Engines In the typical automobile engine, a piston reciprocates (moves back and forth) within each cylinder. Each piston is connected to the crankshaft by means of a link known as a connecting rod. Other types of reciprocating engines substitutes an eccentric, an inclined plate ,or a cam mechanism for the crankshaft .The piston engine has no crankshaft or connecting rods. Engine Components The typical automotive engine is made up of several essential ponents. These ponents are designed to provide efficient and reliable engine operation .The basic ponents in a fourcycle automotive engine include the following: （ 1） Cylinder block. （ 2） Crankshaft. （ 3） Pitons. （ 4） Piston rings. （ 5） Connecting rods. （ 6） Piston pin. （ 7） Cylinder head. （ 8） Valve train(includes valves and valve operating mechanism). 天津職業(yè)技術師范大學 2021屆本科生畢業(yè)設計 Engine construction Cylinder Block The cylinder block is cast in one piece. Usually, this is the largest and the most plicated single piece of metal in the automobile. The cylinder block is a plicated casting made of gray iron (cast iron ) or aluminum. It contains the cylinders and the water jackets that surround them. To make the cylinder block, a sand form called a mold is made. Then molten metal is poured into the mold. When the metal has cooled the sand mold is broken up and removed. This leaves the tough cylinderblock casting.