发动机专业英语（柴油机和汽油机）
INTERNAL COMBUSTION ENGINE
（内燃机）
1 principle of operation （⼯作原理）
1.1 Engine and power（发动机和功率）发动机排量
Engine is used 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 used in automobiles are internal combustion heat engines. Heat energy released in the combustion chamber raises the temperature of the combustion gases with the chamber. The increase in gas temperature causes the pressure of the gases to increase. 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 useful mechanical power.
1.2 Engine Terms （发动机术语）
Linking the piston by a connecting rod to a crankshaft causes the gas to rotate the shaft through half a turn. The power stroke “uses 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.
Engine capacity: this is the swept volume of all the cylinders, e.g. a four-stroke having a capacity of two 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..
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
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 closed.
Compression stroke
As the piston moves upward to compress the fuel mixture trapped in the cylinder,
the valves are closed 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 compressed, heated mixture of fuel and air in the combustion chamber to cause rapid burning. The burning fuel produces intense heat that causes rapid expansion of the gases compressed 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 gases out through the open exhaust valve.
Then, just before the piston reaches its highest point, the exhaust valve closes 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. These sy
stems are the fuel system, intake system, ignition system, cooling system, lubrication system and exhaust system. Each of these systems has a definite function. These systems will discussed in detail later.
New Words
Piston 活塞
Connecting rod 连杆
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
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 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.
2.2 Cylinder Head（⽓缸盖）
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. The most common cylinder head types are the hemi, wedge, and semi-hemi. All three of these terms refer to the shape of the engine's combustion ch
amber. 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.
2.3 Gasket（垫圈）
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. This is a sandwich gasket, i.e. a sheet of asbestos （[ ?s'best?s ]⽯棉）be
tween two sheets of copper, both these materials being able to withstand the high temperature and pressures within the engine.
2.4 Oil Pan or Sump（油底壳）
The oil pan is usually formed of pressed steel. The oil pan and the lower part of the 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 runs down into the pan. Thus, there is constant circulation of
oil between the pan and the working parts of the engine.
New Words
engine block 缸体
cylinder head ⽓缸盖
fasten 使固定
water jacket ⽔套
oil gallery 油道
camshaft 凸轮轴
overhead-cam(OHC) 顶置凸轮
gray iron 灰铸铁
alloy 合⾦
nickel 镍
chromium 铬
casting 铸件
head cover 汽缸盖罩
intake manifold 进⽓总管
distributor 分电器
oil pan 油底壳
aluminum 铝
be lined with 镶有
cylinder sleeve ⽓缸套
hemi 半球形
wedge 楔型，楔⼊
semi-hemi 准半球形
rocker 摇臂
push-rod 推杆
gasket 衬垫
high-tensile ⾼强度的
stud 螺栓
gas-tight 密封的
asbestos ⽯棉