机械设计制造及其自动化专业汽车发动机毕业论文外文文献翻译及原文

毕业设计（论文）外文文献翻译
文献、资料中文题目：汽车发动机
文献、资料英文题目：AUTOMOTIVE ENGINE
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专业：机械设计制造及其自动化（车辆工程）
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翻译日期： 2017.02.14
译文题目： Automobile engine
AUTOMOTIVE ENGINE
1 Engine Classification and Overall Mechanics
The automobile engines can be classified according to: (1) cycles, (2) cooling system, (3) fuel system, (4) ignition method, (5) valve arrangement, (6) cylinder arrangement, (7) engine speed.
Engines used in automobiles are the internal combustion heat engines. The
burning of gasoline inside the engine produces high pressure in the engine combustion chamber. This high pressure force 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 car moves.
The engine requires four basic systems to run (Fig. 2-1). Diesel engines require
three of these systems. They are fuel system, ignition system (except diesel), lubricating system and cooling system. However, three other related systems are also necessary. These are the exhaust system, the emission-control system, and the starting system. Each performs a basic job in making the engine run.
Fig. 2-1 The engine construction
2 Engine Operating Principles
Fig. 2-2 Engine terms
The term “stroke” is used to describe the movement of the piston within the cylinder. The movement of the piston from its uppermost position (TDC, top dead center) to its lowest position (BDC, bottom dead center) is called a stroke. The operating cycle may require either two or four strokes to complete. Most automobile engines operate on the four stroke cycle (Fig. 2-2).
In four-stroke engine, four strokes of the piston in the cylinder are required to complete one full operating cycle. Each stroke is named after the action. It performs intake, compression, power, and exhaust in that order (Fig. 2-3).
Intake stroke Compression stroke Power stroke Exhaust stroke
Fig. 2-3 Four-stroke-cycle gasoline engine
1. The intake stroke
The intake stroke begins with the piston near the top of its travel. As the piston begins its descent, the exhaust valve closes fully, the intake valve opens and the volume of the combustion chamber begins to increase, creating a vacuum. As the piston descends, an air/fuel mixture is drawn from the carburetor into the cylinder through the intake manifold. The intake stroke ends with the intake valve close just after the piston has begun its upstroke.
2. Compression stroke
As the piston is moved up by the crankshaft from BDC, the intake valve closes. The air/fuel mixture is trapped in the cylinder above the piston. Future piston travel
compresses the air/fuel mixture to approximately one-eighth of its original volume (approximately 8:1 compression ratio) when the piston has reached TDC. This completes the compression stroke.
3. 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 sets fire to, the air/fuel mixture. It now begins to burn very rapidly, and the cylinder pressure increases to as much as 3-5MPa or even more. This terrific push against the piston forces it downward, and a powerful impulse 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.
4. Exhaust stroke
At the end of the power stroke the camshaft opens the exhaust valve, and the exhaust stroke begins. Remaining pressure in the cylinder, and upward movement of the piston, force the exhaust gases out of the cylinder. At the end of the exhaust stroke, the exhaust valve closes and the intake valve opens, repeating the entire cycle of events over and over again.
3 Engine Block and Cylinder Head
3.1 Engine Block
The engine block is the basic frame of the engine. All other engine parts either fit inside it or fasten to it. It holds the cylinders, water jackets and oil galleries (Fig. 2-4). The engine block also holds the crankshaft, which fastens to the bottom of the block. The camshaft also fits in the block, except on overhead-cam engines. In most cars, this block is made of gray iron, or an alloy (mixture) of gray iron and other metals, such as nickel or chromium. Engine blocks are castings.
Fig. 2-4 V6 engine block
Some engine blocks, especially those in smaller cars, are made of cast aluminum. This metal is much lighter than iron. However, iron wears better than aluminum. Therefore, the cylinders in most aluminum engines are lined with iron or steel sleeves. These sleeves are called cylinder sleeves. Some engine blocks are made entirely of aluminum.
3.2 Cylinder Sleeves
Cylinder sleeves are used in engine blocks to provide a hard wearing material for pistons and piston rings. The block can be made of one kind of iron that is light and easy to cast while the sleeves uses another that is better able to stand up wear and tear. There are two main types of sleeves: dry and wet (Fig. 2-5).
Dry sleeve Wet sleeve
Fig. 2-5 Cylinder sleeve
3.3 Cylinder Head
The cylinder head fastens to the top of the block, just as a roof fits over a house. The underside forms the combustion chamber with the top of the piston. In-line engine of light vehicles have just one cylinder head for all cylinders; larger in-line engines can have two or more. Just as with engine blocks, cylinder heads can be made of cast iron or aluminum alloy. The cylinder head carries the valves, valve springs and the rockers on the rocker shaft, this part of valve gear being worked by the pushrods. Sometimes the camshaft is fitted directly into the cylinder head and operates on the valves without rockers. This is called an overhead camshaft arrangement.
3.4 Gasket
The cylinder head is attached to the block with high-tensile steel studs. The joint between the block and the head must be gas-tight so that none of the burning mixture can escape. This is achieved by using cylinder head gasket. Gaskets are also used to seal joins between the other parts, such as between the oil pan, manifolds, or water pump and the blocks.
3.5 Oil Pan
The oil pan is usually formed of pressed steel. The oil pan and the lower part of cylinder block together are called the crankcase; they enclose, or encase, the crankshaft. The oil pump in the lubricating system draws oil from the oil pan and sends it to all working parts in the engine. The oil drains off and run down into the pan. Thus, there is a constant circulation of oil between the pan and the working parts of the engine.
4 Piston Assembly, piston rings , The piston pin ,Connecting Rods, Crankshafts And Flywheel
4.1 Piston
Piston rings and the piston pin are together called the piston assembly (Fig. 2-6).。