民航机务英语教程【完整版】.doc

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1、民航机务英语教程【完整版】(文档可以直接使用，也可根据实际需要修订后使用,可编辑放心下载）Lesson OneBernouIlis Principle Why Planes FlyAviation is dependent upon the principle discovered by an eighteenth century scientist，Daniel Bernoulli. Bernoullis principle helps to explain why an airplane flies，how a wing produces lift，and how fuel flows i

2、n an aircraft carburetorIt explains the relationship between the pressure，the vo1ume and the velocity of a fluid in motionSimply stated，the velocity of a given volume of a fluid in motion is inversely proportional to its pressure. As velocity increases，pressure decreasesSince both gases and liquids

3、are classified as fluidsWell use air to demonstrate the properties of a fluid in motionThere are several simple experiments that demonstrate Bernoullis principleThe simplest may be conducted with only a sheet of paperHold the paper up to your lips find blow across the top surfaceNotice that the pape

4、r risesThe velocity of the air over the top of the paper is greater than that under the paperA low pressure area is created above the paper and the difference in pressure causes the paper to risePerhaps you walk past the vacuum cleaner department of department store and youll see a pingpong ball sus

5、pended in the air above vacuum cleaner seemingly without sportThe air passing around the curved surface of the ball is traveling faster than the air just be on the surfaceAgain, the higher pressure outside the airflow causes the ball to remain in the center of the airflowAnother simple experiment us

6、es a piece of paper, a straight pin and a simple sewing spoo1First，push the pin through the paper and insert it in the hole in the spool，the pin simply keep the paper from dropping to the floor . Now, blow through the other end of the spool, a low pressure area is created as the velocity of the air

7、increases between the spool and paperThe higher atmospheric pressure on the back of the paper holds the paper close to the end of the spoolThese experiments illustrate the fact that when the velocity of the fluid increases, the pressure decreasesConversely, when the velocity decreases, the pressure

8、IncreasesHow does this apply to aviation? Lets place a restriction in the path of moving air in this wind tunnelSmoke injected into the air stream indicates the path the air takes around and through the restrictionThe restriction is called a venturi，a given volume of air travels through and around t

9、he venturi in a given period of timeThe entire volume must pass al1 points in the system. Lets consider 3 molecules of air to be our given volume，all 3 molecules must pass around and through the venturi and meet at the other end at the same time. Notice that the molecule passing through the venturi

10、must follow a longer curved path, traveling at greater distance in the same period of time as the molecule that follows a straight pathThat means the molecules traveling through the venturi must travel faster. According to Bernoullis principle，as the velocity increases, pressure decreases，this cause

11、s a reduced pressure in the center of the venturi，while pressure remains the same at either endNow lets look at a half section of the venturi, does the shape remind you anything? You are looking at the cross section of an airfoil，such as a wing the primary lift producing surface of an aircraftThe sa

12、me principle applies here as in the venturi，the 2 molecules of air represent a certain volume，both molecules must reach the trailing edge of the wing section in the same period of time，but the molecule traveling over the upper surface must travel further than the one traveling under the wing because

13、 a curved path it must follow. Again，the molecule traveling the curved path must travel taster than the one traveling the straight line. The pressure differential between the upper and lower surfaces of a wing produces lift that keeps the aircraft aloftWe may illustrate simply the tremendous amount

14、of force that generated by liftSuppose the lower surface of the wing has an area of about 15，000 square inches, remembering that pressure is a force per unit area, a pressure of 15 lbsinch would produce a total force on the bottom of the wing of 225，000 poundsThe curved upper surface of the wing has

15、 a greater surface area than the lower surface，perhaps 20，000 square inchesHowever the pressure on the upper surface is less per square inchIf the pressure weve reduced to 10 lbsinch on the upper wing surface，the total force would be reduced to 200，000 poundsThe difference in pressure between the lo

16、wer and upper wing surfaces is 25，000 poundsThe greater force acting on the bottom wing surface，this is an extremely over simplified explanation of the production of lift on the wingHowever，the basic idea is soundThere are other factors to consider，such as the shape of the airfoil，the angle of attac

17、k，and lift and drag coefficients as well as the speed of the airfoil through the airWeve seen how Bernoullis principle creates lift on an aircraft wing whether in powered or unpowered flightBut，the principle also applies to any important function in aircraft engines，specifically the fuel flow throug

18、h an aircraft carburetorLets return for a moment to the venturi in the wind tunnel，you recall that the pressure in the restriction of the venturi was lower than the pressure outside the venturiA venturi is found in the primary air passage of floattype aircraft carburetor. As air is drawn into the en

19、gine by the pistons，pressure is reduced in throat of the carburetorLets insert a tube in the narrowest part of the venturiand attach the tube to a fuel supply which is open to atmospheric pressureThe difference in pressure between atmospheric pressure on the fuel supply and pressure in the venturi c

20、auses fuel to flow into the venturi where fuel is mixed with air before entering the engine combustion chambersVenturi or orifices may be found in other parts of the aircraft，in a hydraulic line or a fuel control，a measured orifice produces a measured pressure differential between two sides of the l

21、ine，causing fluid to flow at a predetermined rateLets review weve learnt about the relationship of pressure and velocity of a fluid in motionBernoullis principle says that as the velocity of fluid increases，its pressure decreasesAs the velocity of air passing through a venturi increases，the pressure

22、 in the narrowest part of the venturi decreasesAs the velocity of air increases over the upper surface of a wing，the pressure decreases，the imbalance of forces between the upper and lowar surfaces causes the wing to riseBernoullis principle is also partly responsible for fuel flow in an aircraft car

23、buretor which uses a venturi in the primary air passageVenturi may also be used to create a measured rate of fluid flowVenturi-like orifices are found in aircraft hydraulic systems and in fuel controls Words and PhrasesBernoulli s principle 贝努利原理carburetor 汽化器ninversely proportional 反比于lip 唇nthroat

24、咽喉，狭口nproperty 性质nvacuum cleaner 真空吸尘器suspend 悬挂vcurved surface 弯曲外表sewing spool 缝纫机线轴conversely 相反地adrestriction 限定，节流nventuri 文氏管，细腰管nmolecule 分子ncross section of an airfoil 翼型剖面sound 完好的，合理的aangle of attack 攻角，迎角piston 活塞norifice 小孔nlift and drag coefficients 升力和阻力系数hydraulic 液压的areinforce 加强v.co

25、ncept 概念，根本原理nNotesAviation is dependent upon the principle discovered by an eighteenth century scientist，Daniel Bernoulli航空学与十八世纪科学家丹诺尔贝努利所发现的原理密切相关。to be dependent upon意为“依靠于“取决于。discovered by是过去分词引导的定语修饰the principle。The simplest may be conducted with only a sheet of paper 可用一张纸来进行最简单的试验。to be co

26、nducted with意为“由处理“由进行。a sheet of paper意为“一张纸，paper是不可数名词，所以一张纸必须用a sheet of来表示，同样的用法还有许多。The air passing around the curved surface of the ball is traveling faster than the air just be on the surface绕球曲面流过的气流比即将到达球外表的气流速度要快。passing around the curved surface是现代分词引起的定语，修饰the air；faster than意为“比快，比拟的内容

27、前后要一致。 The pressure differential between the upper and lower surfaces of a wing produces lift that keeps the aircraft aloft机翼上下外表的压差产生了升力，使飞机保持在空中。However the basic idea is sound但根本思想是正确的。sound在这里是形容词。Weve seen how Bernoullis principle creates lift on an aircraft wing whether in powered or unpowered

28、 flight我们已经看到了，不管是有动力飞行还是无动力飞 行，贝努利原理是如何在机翼上产生升力的。whetheror意为“不管还是。Grammar用it作形式主语的各种结构常见形式有：请看下面例句：It is often inconvenient to combine vectors by the geometric method用几何方法来合成矢量通常是不便当的。It is worthwhile to use an ultrahigh vacuum system for such purpose把超高真空装置用于这种场合是有价值的。If a body moves from one posi

29、tion to another，it is said to have had displacement如果物体从一处移到另一处，就认为它有了位移。It is common practice to build rockets in pieces通常的做法是把火箭分级制造。It takes sunlight over eight minutes to travel to the earth太阳光传播到地球要8分多钟。It requires a longterm practice to be a good pilot要成为优秀的飞行员需要长时间的实践。It makes steel weak in s

30、trength to rust生锈使钢的强度下降。 Exercises1. Answer the following questions：1) What relationship is described mainly by Bernoullis principle?2) How the paper be moved when you hold the paper up to your lips and blow across the top surface? and why?3) In which section of the venturi the pressure is lowest w

31、hen the air stream passes the tube?4) Why the air traveling over the upper surface must travel further than the air traveling under the wing?5) List some factors that must be consider to calculate the lift except the pressure difference6) What is the function of the measured orifice in a hydraulic l

32、ine or a fuel contr01 77) Why the powered flight come into being? (The lift can be created by just the wings according to Bernoullis principle)2. Choose the correct answer：1) Which one is not correct?ABernoullis principle have not applied in the aviationBWhen the velocity increases，pressure decrease

33、CBernoullis principle is the only scientific principle related to flight DAirfoil can be considered as a part of venturi2) Bernoullis principle expresses the relationship between Atime and velocity of a fluid in motionBvelOCity and distance of a motion fluidCpressure and friction of a liquidDvelocit

34、y and pressure of motion fluid3) several simple experiments that demonstrate Bernoullis principle AThere is BHere is CThis are DThere are4) The curved upper surface of the wing has a surface area than the lower surfaceAgreat BgreatlyCgreatest Dgreater5) It is that keeps the aircraft aloftAthe pressu

35、re differential between the upper and lower surface of a wingBthe high velocity of air below the lower wing surfaceCthe small area of upper wing surfaceDthe large area of lower wing surface6) The basic idea is sound，means that Athe basic idea is noiseBthe basic idea is well voiceCthe basic idea is c

36、orrectDthe basic idea is hearing 7) The same principle applies here in the venturiAas B. than Cthat Dto8) Since both gases and liquids as fluidsWe will use air to demonstrate the principle of a fluid in motionAbe classifiedBclassifyCis classifiedDare classified9) Aviation is dependent the Bernoullis

37、 principleAto Bfor Cupon Dat10) The fuel is mixed airAwith Bto Cin DatLesson TwoArea and VolumeThe study of mathematics is basic to the training of professional aviation maintenance technicianTo watch your career，youll be required to make mathematic calculations that are vital to the successful comp

38、letion 0f many tasksWe study in practice，these calculations may be made safely and easily ensuring the accuracy of your workAmong the most important these calculations used frequently in aviation maintenance，are the measurement of area and volumeSheet metal for airframe repairs is ordered and sold b

39、y the square foot，know exactly how much material to order for particular job，save the customer and your employer money by eliminating wasteEngine horsepower is based in part on the cubic inch displacement or volume of the engine cylindersFirst，lets consider the calculation of areaEveryday objects su

40、ch as this wooden block are measured in three dimensions：length，width and thickness or depthIn calculating the area of one surface of the block，we concern withonly two of these dimensions：length and widthThese two measurements describe a plane surfaceA rectangle is a four sided plane surface with op

41、posite side equally length and with 90 degrees or right angles between adjacent sidesIt is one of simplest plane surfacesThe formula for calculating the area of rectangle is length multiplied by widthL being the length of one of the sides，and W being the width of one of adjacent sidesIn our example，

42、the length of one side is 144 inches，and width of the other side is 48 inches，multiply，we find the area of the rectangle is 6，912 square inchesArea measurements are described in square unitsSquare is a unique form of rectangle in which all sides are equal lengthsThe angle between adjacent sides is a

43、gain 90 degreesThe calculation of the area of a square is done basically the same as that of rectangleSince all sides are the same lengths，we can give them all the same symbol：SSimply multiply the length of one side by the same number，this is called squaring the numberOur formula for the area of a s

44、quare becomes simply as SThe next figure well consider is the triangleA triangle is a three sided plane figure，the sum of the three angles in a triangle always equals 180 degreesAs some interesting comparisons between the triangle and rectangle，that may help you better understand the method of calcu

45、lating the area of the triangleYou notice that the rectangle has four angles that when added together equals 360 degreesThe sum of three angles of triangle add up to 1 80 degrees or half of the angular measurement of the rectangleThe area of the triangle is equal to half of the area of rectangle tha

46、t would enclose itHere is how that works，the three sides of triangle are the base，indicated by the letter B，the altitude，shown here in the letter A，and hypotenuseFor calculating the area，only the base and altitude measurements are necessaryIf we will do a enclosure of our triangles into a rectangle，

47、we would see that the base and altitude measurements are equivalent to the length and width measurements of rectangleHowever，the area of the triangle would only be half the area of the rectangleUsing the formula for calculating the area of rectangle and substituting the base and altitude notations for the length and width of rectangleWe see that the area of the triangle is the base multiplied by the altitude，that product divided by two，this formula will work for the calculations of all trianglesWeve just used an isosceles tria