热动专业英语.doc

1.The Steam Turbine 汽轮机How does a steam turbine work?When a windmill blown with a wind nozzle，it will begin to turn。On the same principle，when high-temperature steam passes through the nozzles and ejects to the blades fitted around the wheel，the wheel turns and thus the heat energy in steam is converted into rotors rotating mechanical energy.The amount of electricity consumed outside changes frequently。The amount of the steam admitted into turbine that drives the generator must also change relevantly so that the rator speed is kept unchanged.If the amount of the steam entry is kept unchanged, the higher the outside load，the lower will be the turbine speed;the lower the outside load，the higher will be the turbine speed.Therefore,the turbine must have a governor gear.The fuction of a governor gear is to regulate the amount of steam entry to keep the turbine speed steady in response to change of the outside load.The following is that the simplest flying ball type direct governor taken as an example to explain its working process.When the turbine speed increases,the flying balls will turn faster by means of the governing gear and they fly apart to both sides due to the action of the centrifugal force.Then the slide ring is made to move upward,with the left end of the link mechanism moved upward and the righr end of it moved downward,and the opening of the governing valve is reduced to a less extent.Thus the amount of steam entry decreases and the turbine speed is lowered.When the speed decreases,the centrifugal force exerted onto the flying balls in the governor decreases and the the spring pulles the flying balls nearer with each other and the slide ring moves downward,with the left end of the link mechanism moved downward and the right end of it moved upward and the opening of the governing valve becomes larger.Thus the amount of the steam entry increases and the turbine speed becomes faster.In this way,the turbine speed is fundamentally kept steady.The amount of exhaust steam of a 300,000 kW condensing turbine is nearly 1,000 tons per hour.Vast amount of exhaust steam is consensed into water by the cooling water in the condenser.The temperature of the cooling water is raised from a few degrees to more than ten degrees.The draining of cooling water wastes a lot of heat energy.This makes the heat economical benefit of the power plant lower greatly.If the amount of exhaust steam entering the condenser is reduced,the heat loss that the cooling water carries away can be reduced.Therfore,the power plants mostly adopt the feed water preheating systems.This is the preheating system that the toewr plants both at home and abroad mostly adopt now.The condensate water is pumped into low-pressure heaters by condensate water pumps and is heated by the steam that has done work in the turbine.Thus it can reduce the turbines amount of steam exhaust to raise the heat economy.The tube plate low-pressure heater is composed of three parts:the shell,core,and cover.There is a steam inlet,a condensate water outlet,a drain water inlet and a water level gauge on the shell.The core is made up of tube plates,U-type tubes,diaphragms and water inlets and water outlets,and mixing chamber on the cover.The heated water flow inside the U-type tubes.After the steam for heating up the water unters,under the action of the guide plates,it is made to flow outsides the U-type tubes in the form of S to splash the outwall of the tubes and to conduct heat to the heated water in the tubes.After the steam gives up its latent heat,it condenses into water,gathers at the lower part and discharges out through the water outlet.Terminologywindmill windmil n.风车，风力发电机nozzle nzl n.喷嘴blade bleid n.叶片rotor rut n.转子，叶轮generator denreit n.发电机，发动机governor gvn n.调速器，控制器govern gvn n.管理，调节，调整，控制centrifugal sentrifjugl n.离心式的valve vlv n.阀门，挡板exhaust igz:st n.乏汽condense kndens n.冷凝，凝结condenser kndens n.冷凝器，凝汽器drain drein n.排水，冷凝水preheat pri:hi:t v.预热，初步加热condensate kndenseit n.冷凝，凝结物shell el n.壳体，外壳gauge geid n.表计，尺度diaphragm daifrm n.膜片，挡板，隔板Notes1.On the same principle，when high-temperature steam passes through the nozzles and ejects to the blades fitted around the wheel，the wheel turns and thus the heat energy in steam is converted into rotors rotating mechanical energy.同理，当高温蒸汽流经喷嘴，喷射到安装在叶轮轮周上的叶片时，叶轮旋转，这样蒸汽的热能转换为转子的旋转机械能。on the same principle 同理2. If the amount of the steam entry is kept unchanged, the higher the outside load，the lower will be the turbine speed;the lower the outside load，the higher will be the turbine speed.如果进汽量保持不变，外界负荷增大，汽轮机转速将下降；外界负荷减少，汽轮机转速将增加。句型 the+比较级the+比较级 愈就愈，越就越3.Then the slide ring is made to move upward,with the left end of the link mechanism moved upward snd the right end of it moved downward,and the opening of the governing valve is reduced to a less extent.然后滑环带着向上移动，连杆左端上升，右端下降，调门开度减小到较小值。4.This is the preheating system that the power plants both at home and abroad mostly adopt now.这就是目前国内国外火电厂大多采用的回热系统。at home and abroad 在国内外5.it is made to flow outside the U-type tubes in the form of S to splash the outwall of the tubes（蒸汽）在U型管外以S型流动，喷洒到U型管外壁上Exercises1.Translate the terms in brackets into English.A turbine is a _(旋转)engine which is driven by a stream of fluid directed on to the_(叶片)of the rotor.In a steam turbine the fluid is steam.Part of the heat and_(压力)energy of steam are changed into_(机械)energy by imparting rotary motion to turbine_(叶轮)In the_(凝汽器),which is a large surface-type heat_(交换器),the steam is condensed,by transferring its_(潜热)to circulating water taken from a nearby river or lake.2.Translate the following paragraph into Chinese.Modern turbines are supplied by the boiler with steam that is highly superheated.As the steam passes through the turbines,its pressure and temperature fall until at a certain stage(级)all the superheat(过热) is lost，and thereafter drops of water are formed by condensation of some of the steam.This drops can damage the blades and reduce the turbine efficiency,and this is one reason why the steam,after passing through the high-pressure turbine,is sometimes re-superheated(再过热)before entering the medium-pressure(中压)turbine.2.Types of turbines 汽轮机类型To obtain a perspective of the field,we shall classify the various typers of turbine according to use.The condensing turbine is commonest in central-station practise.It consists of a steam turbine to which main steam is supplied at any economically indicated pressure and temperature.Some steam normally is extracted for feedwater heating,but most of the steam goes entirely through the turbine to the condenser.The primary function of the condensing turbine is to produce power,usually in a cycle designed to have high economy.The heating of the feedwater is incidental to the main purpose,which is to produce power.By far the greater proportion of steam turbines used in the central-station industry is of this type.The non-condensing turbine is used either in industrial plants or in central stations.Its distinguishing characteristic is that its”back pressure”is above atmospheric.In this strictest interpretation the term applies to any turbine not equipped with a condenser for condensing the exhaust,but common usage has given it the connotation of higher-then-atmospheric exhaust pressure.Non-condensing turbines have two major applications.The first is in an industrial plant which requires process steam at an appreciable pressure.The second is in a central-station plant which is being modernized by superposition of a high-pressure turbine on the original and older low-pressure turbines in the station.The exhaust steam from the high-pressure turbine is used to supply the low-pressure turbines.By this means a cycle is realized which has higher initial pressure and temperature,and consequently better economy,than the original installation,without scrapping the low-pressure turbines,which may have many have many years of useful life left in them.Usually such a program requires the removal of the old low-pressure boilers and installation of new high-pressure and high-temperature ones,although sometimes the old low-pressure boilers are preserved in a standby condition for emergency use in the event of failure of the new high-pressure installation.Another type of turbine in common use,particularly in the industrial field,is the automatic extraction turbine.Such units may be built in the single automatic,the double automatic,or the triple automatic(race)type.The automatic extraction turbine is designed for extraction of considerable quantities of steam at some stage during the expansion,the pressure at the stage being maintained constant at some predetermined value over a large part of the extraction and load range by automatic valving.The automatic extraction turbine,in the single-automatic type,is practically the equivalent of a high-pressue non-condensing turbine placed ahead of a low-pressure turbine.The high-pressure section,so-called,exhaust part of its steam into the low-pressure section,the remainder being bled off for use elsewhere.The valving of the low-pressure turbine acts as a pressure regulator and is sensitive to the pressure in the extracting line.If this pressure tends to increase,the valves open,thus accepting more of the high-pressure-section steam flow and restoring the pressure;in this manner the pressure may be maintained at a nearly constant value over a broad range.Such opening of the valves to the low-pressure section would normally cause an increase in power output.A speed governor is used to control the high-pressure-section valves,and the pressure regulator to control the low-pressure-section valves.Because of the flexibility of this type of turbine and the extra complication in its construction,the manufacture usually charges a higher price than for an equivalent condensing turbine.Because of the extra valving within the turbine,and the necessity for design of the stages to cover a broader range of operating conditions,it is to be expected that the efficiency of the turbine will be somewhat poorer than that of an equivalent straight-condensing turbine,frequently in the neighbor-hood of 1 to 3% at rated power,and greater percentage at the lower powers.Turbine may be further classfied into power-generating and mechanical-drive units,used,respectively,for generation of electrical power and to drive mechanical equipment such as pumps.Terminologyextract ikstrkt v.抽出，分离，萃取cycle saikl n.周期，循环atmospheric ,tmsferik a.大气的，常压的superposition ,sju:ppzin n.叠加，前置initial inil a.最初的，初始的installation ,instlein n.装置，设备standby stndbai a.备用的，储备的，辅助的emergency im:dnsi n.紧急，事故，应急automatic ,:tmtik a.自动的extraction ikstrkn n.抽汽stage steid n.级performance pf:mns n.运行，性能predetermine pri:dit:min v.预定，先定exhaust igz:st v.抽空，排汽section sekn n.部件，部分，区段，分区rated reitid a.额定的，规定的generate den,reit v.发电，发热，产生generation ,denrein n.发电，发热，产生Notes1.The condensing turbine is commonest in central-station practice.凝气式汽轮机在电力工业中应用非常普遍。形容词最高级前面没有the,不表示比较，而只作“非常”或“很大程度上”解释。文中类似的句子还有:In this strictest interpretation the term applies to any turbine not equipped with a condenser for condensing the exhaust.很准确地解释，这个术语书适用于任何一种不带冷凝乏汽的凝汽器的汽机。2.By far the greater proportion of steam turbines used in the central-station industry is of this type.在电力工业中这类汽轮机的应用要占相当大的比例。by far 与比较级或最高级连用，意为“大量,很多”3.By this means a cycle is realized which has higher initial pressure and temperature,and consequently better economy,than the original installation,without scrapping the low-pressure turbines,which may have many have many years of useful life left in them.通过这种方法实现的循环和原始的设备相比，初始压力和温度提高，因而经济性提高，而且不会淘汰那些还有许多年剩余使用寿命的低压汽轮机。此句中主句是A cycle is realized,第一个which引导的定语从句说明a cycle，第二个which引导的定语从句说明the low-pressure turbines。scrap原意为“刮落，擦去”，此处引申为“淘汰”。4.psi为英制压力单位，即磅力每平方英寸。1 psi=6.89kPa psig=pounds per square inch gauge 计示磅力每平方英寸5.The high-pressure section,so-called,exhaust part of its steam into the low-pressure section,the remainder being bled off for use elsewhere.高压段，姑且这么称，抽出的部分蒸汽进入低压段，其余蒸汽抽出来另作它用。so-called 为插入语，译为“所谓的，通常所说的”bleeding off 原意为“抽血”，此处译为“抽出”。Exercises1.Word Building构词法主要的一种词根加前缀(the prefix)或后缀(the suffix)构成新词，例如:heat(加热)reheat(再热)water(水)waterfree(不含水)试按构词法推断以下列举的术语的意思。multiloop multistage thermometer thermodynamicrecirculation restart preheat prepositionpracticable considerable attractive relative2.Translate the following paragraph into Chinese.The central-station industry realized the wisdom(知识)of such superposition in early part of the 1930-1940 decade(十年),and a wave of superposition began.In this program,which encompassed most of the larger utilities in the country,the usual exhaust pressure was from 200 to 300 psi.Most of the superposed units supplied steam to low-perssure turbines installed from 10 to 20 years previously. Most of the old low-pressure capacity was“topped”in that decade,so that any new wave of superposition will probably encompass low-pressure turbines of higher initial pressure than the previous ones-perhaps units up to 400 or 450 psi initial pressure.Such a program will use topping(前置的)turbines at pressures of 1800 psig and higher,with the necessary high initial temperatures(and/or reheat)to obtain sufficient power from the new capacity to make the investment(投资)justifiable both on the basis of added power and on the grounds of improved economy.3.Methods of Steam Distribution 配汽方式With respect to constructional features,turbines may be classified as throttling,multivalve,overload-valve,and stage-valve machines.This designation describes the method of control and is diagrammatically illustrated in Fig.1. Fig.1 Turbine valving arrangementThe throttling machine is equipped with a valve in the steam line which decreases or increases the load on the turbine by changling the pressure applied to it.The method of control,though very economical from the standpoint of first cost and acceptable in many cases,does not yield the highest efficiency over the load range.At the full-load point,with the throttle valve wide open,a turbine of this type will be as efficient as,and in some cases even more efficient than,the multivalve type.At the lighter loads the efficiency is greatly decreased because the turbine is supplied at a pressure lower than the design pressure,the throttle valve having“broken down”the original pressure to some lower value before the steam reaches the turbine proper.The multivalve machine is equipped with a series of valves designed to supply steam to separate groups of nozzles in the first stage of the turbine.The merit of the arrangement is that the efficiency of the cycle at the lower powers is greatly improved over that of the throttling machine.The improvement is accomplished by permitting the turbine to operate at full steam pressure and reduced flow by supply of the steam to a smaller area of nozzle in the first stage,so that full pressure is required,even though the flow is reduced below the maximum design flow.This method of control utilizes the full boiler pressure(nearly)throughout almost the entire load range,giving better economy without sacrifice of flexibility.The valves are operated in sequence by a camshaft or other device under control of the governor.In this arrangement there is a decrease in efficiency of the first stage of the turbine at light loads,but it is more than overbalanced by the use of the full pressure,giving a considerable net gain in performance.The overload-valve type of machine is a turbine usually equipped with multiple control valves but in addition equipped with a separate valve(one or more)which permits part of the main steam to be admitted to a lower stage(or more than one,with multiple overload valves)in the turbine.The pressure in this“overload stage”is permitted to build up to nearly line pressure,thus causing a considerably greater flow to be passed by the turbine than would be passed if all the steam had to pass through the relatively small area of the nozzles in the first stage.When the pressure in the overload stage(assume this to be the first stage,for example)builds up to a high value,the flow which passes through the first stage is greatly reduced by the highly restrictive pressure in the first stage shell,until finally almost no steam is passing through it .In this arrangement the parts of the turbine must be made mechanically strong enough to withstand the additional mechanical loading imposed by the high steam flow.A slight sacrifice in efficiency is usually caused by the reduction in flow to the first stage to the point where the first stage produces very little power,and even in some cases becomes detriment,requiring power from the rest of the turbine to overcome its windage losses.The advantage of this arrangement is that a turbine may be designed to carry high maximum load without sacrifice in the light-load performance.The stage-valve machine is similar in some respects to the overload machine,the chief difference being that a valve is provided to bypass steam from the space following the first stage(first-stage shell)to a lower stage,usually the third or fourth stage.In this arrangement all the steam is passed through the first stage,thereby having its temperature reduced.The reduction in temperature is partic