内燃机专业英语自编讲义部分：
1. Engine Classification and Overall Mechanics
盘成语The automobile engines can be classified according to: 1. number of cylinders; 2. arrangement of cylinders; 3. arrangement of valves; 4. type of cooling; 5. number of cycles (two or four); 6. type of fuel burned; 7. type of ignition.
The engine is the source of power that makes the wheels go around and the car move. The automobile engine is an internal-combustion engine becau the fuel (gasoline) is burned inside it. The burning of gasoline inside the engine produces high pressure in the engine combustion chamber. This high pressure forces piston to move, the movement is carried by connecting rods to the engine crankshaft. The crankshaft is thus made to rotate; the rotary motion is carried through the power train to the car wheels so that they rotate and the moves.
The engine requires a fuel system to supply it with a mixture of air and fuel. The fuel system
does this by pumping liquid gasoline from a tank into the carburetor, a mixing device that mixes the gasoline with air. The mixture is delivered to the engine where it is burned.
The engine also needs a cooling system, the combustion of the air-fuel mixture in the engine creates a very high temperature (as high as 2000 to 2700 ℃). The cooling system takes heat away from the engine by circulating a liquid coolant (water mixed with antifreeze) between the engine and a radiator. The coolant gets hot as it goes through the engine. It cools off as it goes through the radiator. Thus, the coolant continually takes heat away from the engine, where it could do damage, and delivers it to the radiator. Air passing through the radiator takes heat away from the radiator.
The engine also includes a lubricating system. The purpo of the lubricating system is to supply all moving parts inside the engine with lubricating oil; the oil keeps moving parts from wearing excessively.
The engine requires a fourth system, the ignition system. The ignition system provides high-voltage electric sparks that ignite, or t fire to, the charges of air-fuel mixture in the
engine combustion chambers.
罗盘使用方法The fifth is starting system and its purpo is to change the electrical current into the mechanical energy to push the crank-shaft around. By means of this, the engine can be started.
The five systems are discusd briefly in following ctions.
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大西洋公路杨利伟事迹Words and Expressions
combustion chamber 燃烧室；ignition. 点燃；power train 小学数学思维训练题动力传动系统；carburetor 化油器；antifreeze 防冻的；coolant 冷却剂（液态）；crankshaft 曲轴
2. Four-stage-engine Operation
The action taking place in the engine cylinder can be divided into four stages, or strokes. “Stroke” refers to piston movement; as stroke occurs when the piston moves from one limiting position to the other. The upper limit of piston movement is called TDC （top dea
d center）. The lower limit of piston movement is called BDC (bottom dead center). A stroke is piston movement from TDC to BDC or from BDC to TDC. In other words, the piston completes a stroke each time it change its direction of motion.
Where the entire cycle of events in the cylinder requires four strokes (or two crankshaft revolutions), the engine is called a four-stroke-cycle engine, or a four-cycle engine. The four piston strokes are intake, compression, power, and exhaust.
Intake stroke. On the intake stroke, the intake valve has opened, the piston is moving downward, and a mixture of air and vaporized gasoline is entering the cylinder through the valve port. The mixture of air and vaporized gasoline is delivered to the cylinder by the fuel system and carburetor.
Compression stroke. After the piston reaches BDC, or the lower limit of its travel, it begins to move upward. As this happens, the intake valve clos. The exhaust valve is also clod, so that the cylinder is aled. As the piston moves upward (pushed now by the revolving crankshaft and connecting rod), the air-fuel mixture is compresd. By the time
the piston reaches TDC, the mixture has been compresd to as little as one-tenth of its original volume, or even less. This compression of the air-fuel mixture increas the pressure in the cylinder. When the air-fuel mixture is compresd, not only does the pressure in the cylinder go up, but the temperature of the mixture also increas.
Power stroke. As the piston reaches TDC on the compression stroke, an electric spark is produced at the spark plug. The ignition system delivers a high-voltage surge of electricity to the spark plug to produce the spark. The spark ignites, or ts fire to, the air-fuel mixture. It now begins to burn very rapidly, and the cylinder pressure increas to as much as 3-5 MPa or even more. This terrific push against the piston forces it downward, and a power impul is transmitted through the connecting rod to the crankpin on the crankshaft. The crankshaft is rotated as the piston is pushed down by the pressure above it.
