Unit 3
Topic: Automotive Basics Ⅰ
Unit objectives
After studying this unit ,you are expected to be able to 1. have a general idea of vehicle;
2. know the terms and phrases about engine and chassis; 3. talk about the operating principle of engine by your own words;
4.master the basic knowledge about the auto structure; 5. know how to write a note。
Warming-up
Today's average car contains more than 15,000 separate, individual parts that must work together. These parts can grouped into four major categories: engine, body, chassis and electrical equipment.
Task 1 Work with your partner and try to find English expressions about auto
structure as many as possible, and then try to remember their English expressions
Task 2 The following picture is the anatomy of an automobile, please speak
out the name for every part. The words are given below for your reference.
Trunk, tail light, spare wheel, wheel, transmission, muffler, line shaft, body side moulding, disk brake, oil filter, alternator, radiator, distributor, battery, air filter, windshield washer, steering wheel, windshield wiper, seat, window frame, rearview mirror
Section A Engine
Task 1 Before reading the passage, please try to complete the following tasks.
1. Do you know the entire structure of automobiles Engine? Please research online for the information about engine of automobiles and try to understand the principle of operation.
2. Please research online for engine instructions and state them in English according to the following picture.
Flywheel Flywheel belt
Camshaft
valve
cylinder
piston
Connecting rod
bearing Oil pan
crankshaft
Reading A
Automotive Engine Operating Principles
Engine is regarded as the “heart” of an automobile. An engine can convert fuel into energy that moves the automobile. Generally, an
automobile is operated by an engine, inside which the fuel is burned. According to different standards, engine can be classified into different types, such as gasoline engines and diesel engines. But whatever type it is of, the engine always has two main working parts: crank connecting rod and valve system. Besides, any type of engine usually includes five basic systems, i.e. the starting, fuel, ignition, cooling and lubricating systems.
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.
As is said above, the engine supplies power for the automobile and makes it move。Then how an Engine Works? Since the same process occurs in each cylinder, we will take a look at one cylinder to see how the four stroke process works.
The four strokes are intake, compression, power and exhaust. The piston travels down on the intake stroke, up on the compression stroke, down on the power stroke and up on the exhaust stroke. 1. intake
As the piston starts down on the intake stroke, the intake valve opens and the fuel-air mixture is drawn into the cylinder (similar to drawing back the plunger on a hypodermic needle to allow fluid to be drawn into the chamber).When the piston reaches the bottom of the intake stroke, the intake valve closes, trapping the air-fuel mixture in the cylinder.
2. compression
The piston moves up and compresses the trapped air fuel mixture that was brought in by the intake stroke. The amount that the mixture is compressed is determined by the compression ratio of the engine. The compression ration on the average engine is in the range of 8:1 to 10:1.This means that when the piston reaches the top of the cylinder, the air-fuel mixture is squeezed to about one tenth of its original volume.
3. power
The spark plug fires, igniting the compressed air-fuel mixture which produces a powerful expansion of the vapor. The combustion process pushes the piston down the cylinder with great force turning the crankshaft to provide the power to propel the vehicle. Each piston fires at a different time, determined by the engine firing order. By the time the crankshaft completes two revolutions, each cylinder in the engine will have gone through one power stroke.
4. exhaust
With the piston at the bottom of the cylinder, the exhaust valve opens to allow the burned exhaust gas to be expelled to the exhaust system. Since the cylinder contains so much pressure, when the valve opens, the gas is expelled with a violent force (that is why a vehicle without a muffler sounds so loud.) The piston travels up to the top of the cylinder pushing all the exhaust out before closing the exhaust valve in preparation for starting the four stroke process over again.
New Words convert [k?n'v?:t] vt. & vi. 1.(使)转变，(使)转化
2.皈依，改变(信仰)
fuel [fju?l] n. 燃料，燃烧剂 standard ['st?nd?d] n. 1.标准，水准,
2.平均质量；业务水
classify ['kl?s?'fai] vt. 1.分类；归类
2.划分；区分；界定
gasoline ['ɡ?s??lin] n. 汽油 diesel ['diz?l] n. 1.柴油
2.柴油机机车(或船等)，内燃机车
crank [kr??k] n. （L 字形）曲柄，曲轴
vt. 用曲柄转动（或启动）
valve [v?lv] n. 1.阀，活门，阀门，气门
2.(心脏的)瓣膜