车辆工程专业英语

Ignition System
Internal combustion engines require ignition of the mixture, either by spark ignition (SI) or compression ignition (CI).
Starting System
As their name implies, four-stroke internal combustion engines have four basic steps that repeat with every two revolutions of the crankshaft:① Intake stroke ② Compression stroke, ③ Power stroke, ④ Exhaust stroke. The four strokes will be illustrated in Fig.2.4. They draw in an air-fuel mixture to the cylinders, compress it, ignite and combust it, then discharge it. Repeating these four actions gives gasoline engines their power. The cycle begins at Top Dead Centre (TDC), when the piston is farthest away from the crankshaft. A cycle refers to the full travel of the piston from TDC to Bottom Dead Centre (BDC).
Cylinder Block
The core of the engine is the cylinder, with the piston moving up and down inside the cylinder.
Crankshaft awenku.baidu.comd Connecting Rod Mechanism
Valve Mechanism
A valve mechanism is a group of components that opens and closes the intake and exhaust valves in the cylinder head at the appropriate time. The main functions of the valve gear are to provide timely admission of the fresh charge into the cylinders and exhaust of spent gases from them.
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汽车专业英语
Fuel Supply System
The fuel system supplies fuel to the engine. It also has the functions to regulate the volume of fuel supply. The fuel systems in diesel and gasoline engines are different.
(a) flat Fig.2.2
(b) V-type Cylinder Arrangement
(c) in-line
By Cooling System
Liquid-cooled engines and air-cooled engines are being used. Liquid-cooled engines are the most common in the engine industry. There are also other ways to classify the engines. Despite of these classifications, the structure of the engine is basically the same.
Fig.2.3 1—intake valve
Main Parts in Four Stroke Engine 4—combustion chamber 5—piston head
2—spark plug 3—exhaust valve
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Unit 2
The Basic Principle of Engine
The starting system forces the engine to crank with an electric motor, and starts the engine.
Text B Engine Operating Principles
A four-stroke engine, also known as four-cycle, is an internal combustion engine in which the piston completes four separate strokes：intake, compression, power and exhaust—during two separate revolutions of the engine’s crankshaft, and one single thermodynamic cycle.The main parts in four stroke engine are shown in Fig.2.3.
The crankshaft changes the linear movement of the piston into a rotational movement via a connecting rod. The connecting rod connects the piston to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates.
Unit 2
The Basic Principle of Engine
By Cylinder Arrangement
Most cars have more than one cylinder. Four, six and eight cylinders are common used. In a multi-cylinder engine, the cylinders are usually arranged in one of three ways: in-line, V-type, or flat (Fig.2.2). Today the number of cylinders is growing, the cylinders also can be arranged as W-type.
Cooling System
The cooling system regulates the engine temperature to an optimal level (80℃ to 90℃ at coolant temperature) by circulating the coolant throughout the engine under all operating conditions and during all seasons of the year. The cooling fan cools the coolant in the radiator and water pump circulates the coolant through the cylinder head and the cylinder block.
Main Components
The engine consists of several different mechanisms and systems including cylinder block, crankshaft and connecting rod mechanism, valve mechanism, fuel supply system, lubrication system, cooling system, ignition system and starting system.
Classification of Engine
The engine can be classified in following ways:
By Fuel System
Gasoline engine and diesel engine are used. In a gasoline engine, the air-fuel mixture is exploded in the engine. A diesel engine uses diesel fuel. It generates high power at low speeds. The fuel efficiency is better than that of a gasoline engine.
Lubrication System
The lubrication system uses an oil pump to continuously supply engine oil throughout the inside of the engine. This system reduces friction between parts with a film of oil. If the engine is run without oil, the friction can cause poor running, or cause even meltdown. In addition to lubrication, engine oil cools and cleans the engine.
Unit 2
The Basic Principle of Engine
Text A Classification and Main Components of Engine
The internal combustion engine is an engine in which the combustion of fuel occurs with oxygen(usually air) in a combustion chamber, as shown in Fig.2.1.
Intake Stroke
On the intake stroke of the piston, the piston descends from (TDC,BDC) to (TDC, BDC), reducing the pressure inside the cylinder. A mixture of fuel and air, or just air in a diesel engine, is forced by atmospheric pressure into the cylinder through the intake port. The intake valve(s) then (open,close).
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Fig.2.1 1—the cap of the cylinder head 5—crankshaft 6—oil pan
Internal Combustion Engine 2—valve 7—pulley 3—engine block 8—cylinder 4—flywheel 9—timing gear