INTERNAL COMBUSTION ENGINE
（内燃机）
1 principle of operation （工作原理or操作原理）
1.1 Engine and power（发动机和功率）
Engine is ud to produce power. The chemical energy in fuel is converted to heat by the burning of the fuel at a controlled rate. This process is called combustion. If engine combustion occurs with the power chamber, the engine is called internal combustion engine. If combustion takes place outside the cylinder, the engine is called an external combustion engine.
Engine ud in automobiles are internal combustion heat engines. Heat energy relead in the combustion chamber rais the temperature of the combustion gas with the chamber. The increa in gas temperature caus the pressure of the gas to increa. The pressure developed within the combustion chamber is applied to the head of a piston to produce a usable mechanical force, which is then converted into uful mechanical power.
1.2 Engine Terms （发动机术语）
Linking the piston by a connecting rod to a crankshaft caus the gas to rotate the shaft through half a turn. The power stroke “us up”the gas, so means must be provided to expel the burnt gas and recharge the cylinder with a fresh petrol-air mixture:this control of gas movement is the duty of the valves; an inlet valve allows the new mixture to enter at the right time and an exhaust valve lets out the burnt gas after the gas has done its job.
Engine terms are:
TDC(Top Dead Center): the position of the crank and piston when the piston is farther away from the crankshaft.
BDC(Bottom Dead Center): the position of the crank and piston when the piston is nearest to the crankshaft.
Stroke: the distance between BDC and TDC; stroke is controlled by the crankshaft. Bore: the internal diameter of the cylinder.
Swept volume: the volume between TDC and BDC.
证券投资分析Engine capacity: this is the swept volume of all the cylinders, e.g. a four-stroke having a capacity of t
wo liters(2000cm) has a cylinder swept volume of 50cm. Clearance volume: the volume of the space above the piston when it is at TDC. Compression ratio = (swept vol + clearance vol)/(clearance vol)
Two-stroke: a power stroke every revolution of the crank.
Four-stroke: a power stroke every other revolution of the crank..
古王国时期
1.3 The Four-stroke Spark-ignition Engine Cycle（四冲程火花塞点火发动机循环）
The spark-ignition engine is an internal-combustion engine with externally supplied in ignition, which converts the energy contained in the fuel to kineticenergy.(动能)
The cycle of operations is spread over four piston strokes. To complete the full cycle it takes two revolutions of the crankshaft.
The operating strokes are:
Intake stroke
力宏
This stroke introduces a mixture of atomized gasoline and air into the cylinder. The stroke starts when the piston moves downward from a position near the top of the cylinder. As the piston moves downward, a vacuum, or low-pressure area, is created. During the intake stroke, one of the ports is opened by moving the inlet valve. The exhaust valve remains tightly clod.母亲心
Compression stroke
As the piston moves upward to compress the fuel mixture trapped in the cylinder,
仙草的功效与作用>怎样解开手机锁屏密码the valves are clod tightly. This compression action heats the air/fuel mixture slightly and confines it within a small area called the combustion chamber.
Power stroke
Just before the piston reaches the top of its compression stroke, an electrical spark is introduced from a spark plug screwed into the cylinder head.
The spark ignites the compresd, heated mixture of fuel and air in the combustion chamber to cau rapid burning. The burning fuel produces inten heat that caus rapid expansion of the gas compresd within the cylinder. This pressure forces the piston downward. The downward stroke turns the crankshaft with great force. Exhaust stroke
Just before the bottom of the power stroke, the exhaust valve opens. This allows the piston, as it moves upward, to push the hot, burned gas out through the open exhaust valve.
Then, just before the piston reaches its highest point, the exhaust valve clos and the inlet valve opens. As the piston reaches the highest point in the cylinder, known as TDC, it starts back down again. Thus, one cycle ends and another begins immediately.
1.4 Engine Overall Mechanics（发动机总体机构）
The engine has hundreds of other parts. The major parts of engine are engine block, engine heads, pistons, connecting rods, crankshaft and valves. The other parts are joined to make systems. The
systems are the fuel system, intake system, ignition system, cooling system, lubrication system and exhaust system. Each of the systems has a definite function. The systems will discusd in detail later.
New Words
Piston 活塞
Connecting rod 连杆
二年级成语
Crankshaft 曲轴
Power stoke 活塞行程
Expel 排出
Valve 气阀
inlet(intake) valve 进气阀
exhaust valve 排气阀跳跳糖怎么玩
TDC 上止点
BDC 下止点
Bore 缸径
swept volume 有效容积
engine capacity 发动机排量
clearance volume 余隙容积，燃烧室容积
compression ratio 压缩比
revolution 旋转，转数
every other 每隔一个
spread over 分布，遍及intake stroke 进气行程compression stroke 压缩行程knock 敲缸，敲打exhaust stroke 排气行程engine block 发动机缸体lubrication 润滑
2 Engine Block and Cylinder Head（发动机机体和气缸盖）
2.1 Engine Block（发动机机体）
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. The engine block also holds the crankshaft, which fastens to the bottom of the block. The camshaft also fits inside the block, except on overhead-cam engines (OHC). 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.
Some engine blocks, especially tho 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. The sleeves are called cylinder sleeves. Some engine blocks are made entirely of aluminum.
2.2 Cylinder Head（气缸盖）
The cylinder head fastens to the top of the block, just as a roof fits over a hou. The underside forms the combustion chamber with the top of the piston. The most common cylinder head types are the hemi, wedge, and mi-hemi. All three of the terms refer to the shape of the engine's combustion chamber. The cylinder head carries the valves, valve springs and the rockers on the rocker shaft, this part of the valve gear being worked by the push-rods. Sometimes the camshaft is fitted directly into the cylinder head and operates on the valves without rockers. This is called an overhead camshaft arrangement. Like the cylinder block, the head is made from either cast iron or aluminum alloy.
