外文翻譯--流體力學和流體機械概述【中英文文獻譯文】

外文翻譯--流體力學和流體機械概述【中英文文獻譯文】,中英文文獻譯文,外文,翻譯,流體力學,以及,流體,機械,概述,中英文,文獻,譯文 The hydordynanmics and the fluid machineries The hydordynanmics is can be applied in in many ways, this makes the hydordynanmics become all engineering sums and should full one of the important courses of foundation in the science.The fluid run within piping, the water ?t says for the civil engineer that is very important to be like the research of the fluid machineries, such as water aspirator, compressor, heat exchanger, nozzle and the rocket engine...etc., make hydordynanmics say for the mechanical engineer also very important.The air current rounds a phenomenon of aerodynamics of substance is an interested in basic question of the aviation aerospace engineers that designs the airplane, guided missile and rockets the atmosphere and oceanses are all a fluid, so the research of the convection body is meteorology, hydrology and the foundation of the oceanographies.Today, many new theories put together the hydordynanmics and classic theory tie in modern engineering.For example study to call it as to give or get an electric shock the magnetohydrodynamics, MHD together the hydordynanmics and the electromagnetism, electromagnetics theory combinations.In newly) the capacity conversion apparatusof the type, the battery magnetohydrodynamics, MHD is necessary in phenomenon study star and ionosphere We can see, saying for the engineer of the modern and scientist that acquaint with the hydordynanmics is very necessary.Obviously, hydordynanmics and its applications are a course that has the extensive professional realms. In the solid rigid body mechanics, we usually ask thus a question:What is the tiny clique position function concerning time?Pass other ll questions of this condition, for example, what speed and accelerations are, can answer.If the position vector r represents the place of the tiny clique, so the r( t) is a count for much parameter. However.In the fluid we but the twin anti is a tiny clique, what we pay attention to is a continuous stream actually.We need not on the trail of each tiny clique or even a handful of several runnings of liquid are contrary, the question that to ask is:A little bit some place in the space, what speed, acceleration and the thermodynamic property function concerning times are that should order?Change along with the time, the fluid that should order is constantly the sum to flow through its new fluid occurrence to interchange the action, so we do not follow any running of clique with tiny fluid but the research space a little bit some circumstance of change that at any time ask, but ignore in the any and particular time by luck is what fluid in the way of this kind of description fluid call Euler method, with its opposite description method call the method of day of tractive lattice àê , the method of day of the lattice àê of tension is used for the description is in the rigid body mechanics a running of tiny clique. Spoke of a phrase before:Connect the stream from the fluid of angle see, what meaning does that phrase have?We suppose the space of the fluid tiny clique( or molecule), or say more by the square to is an equally free stroke very small.We say very small compare the hydordynanmics theory application in the physics size of the actual question with us but talk.In aerodynamics study, the aerofoil thickness than round the average and free stroke of the air current of the super - aerofoil to want big and many quantisty stages.So we suppose all processes of limit are meaningful, but the people is keeping any fluids of volume of the continuity circumstance F and canning be divided into very obvious and end this kind of division of smaller volume under very difficult progress go to, but we suppose this division and can carry on, this is very small because of the size of the tiny clique, seeing from the angle of tiny view, this hases no influence to our research. In can't press flow, the energy equation anti is necessary, because the density has already know.For describing the fluid run completely, need to solve the pressure and speeds only.At this time the temperature is a separation of, if request to solve the temperature then the demand uses the energy equation The fluid machinery mean those transport the fluid capacity or from sample the capacity in the fluid of equipments of machinery.The number first class fluid machinery knows together as the water aspirator, but the second fluid machinery be constitute by the turbine.Although also involved other machineries, the multiple point is the turbine machinery, namely those with shaft of running to deliver the water aspirator and the turbine of the capacity. Have three turbines of the type type in common usely, they respectively is:The Pelton water turbine sum two kinds of reaction turbine- Francises turbine sum propels the type turbine.The Pelton turbine is a kind of turbine of pulsation type, it includes the ring shape blade that a ring seeparate, the Pelton complete the operate towards seeparating the improvement of the blade to make water turbine can nicely, and therefore the water turbine also got the extensive application.The jet( or several jets of the large scale system) direction of the water with give the direction of settle the blade contrary, and tie the anti to bounce back to fly to again each side in the blade that seeparate, as a result pass impact load blade.When the turbine running, the blade and jets that each one follow become a straight line. The Francis turbine centre in typical model, the water current take to be pass by the leading blade of slice toward quantisty into the outside circumference, the turbine blade designs to make the water current follow the diameter thus to flow through the turbine blade, the fluid lost the angular momentum, so plused a turning moment for blade.Though the first Francis turbine is to leave the cenre type turbine, they are usually combination that leaves the cenre type and the shaft stream types currently, its blade usually screw the water current direction from diameter to for the shaft to. Second reaction turbine, be called to propel the type turbine, is the shaft stream type basically of.Be like the Francis turbine, the propulsion type turbine also reduced the angular momentum of the fluid, as a result also produced a turning moment in propeling the blade.Blade slopes of most moderns propulsion type turbine are all adjustable, in order to in within the scope of certain displacement higher effciency of sustaining.Such apparatus is called the Kaplan turbine. Almost all turbines are direct to connect with each other with generator set, so the turbine must keep the almost unchanged revolution speed, this is the synchronizing speed.This from adjust soon the machine sustaining of speed, from dynamo the number sum of the electrode produces the electric current of frequency to decide.For 60 electric currents of the Hertzs( the number of times of cycle of every second), the speed N( the revolving speed of every minute), from the formula N= the 7200/ np give settle, but the np is the electrode number of the dynamo, and must be the even integer. The pulsation type turbine and of the reaction turbines are most standard distinct is a reaction turbine to full to be surround by the liquid, but the pulsation type turbine then is not.Can see, the Pelton water turbine must from the pressure unchanged jet acquisition capacity, as a result the capacity is only can from the kinetuc energy of the fluid in acquisition. The water of the ex- bath or head of ?t be spread by a duct that is called to lead the service pipe pass toward turbine, but at this time the nozzle that then need to be a to design with meticulous care to raise the capacity that the jet velocity well makes and can acquire to maximize.Displacement from a hand type valve control, and a by - pass valve or the jet convertor assembly are in common use to protect this system, keeping the system amount of internal flow from nasty play to reduce.If the hand type valve must turn off quickly, an overflow water tank can also be the substitute to reduce the ripples of water pressure or the influence of the water hammers.Because the wake is impossible to restore again the residue capacity of the fluid, the water current goes in to turn on water ?t or the path of the wake surface the followings not to bring about any influence on the function of the Pelton water turbine.The Pelton water turbine usually is to set on-line in a horizontal axis, and the direct sum dynamo connect with each other, usually is two water turbine in balance set in the dynamo of both sides drive the same of shaft together. Although the turbine occasionally useds for some small scaled machineries of drive, they used for the quotient of the large and valuable equipments' use to generate electricity almost and all substantially up.The application is only the most standard type in the indrstry.Actually, these three turbines of the type type can immediately overlay all indrstries operation condition.On the other hand, the type of the pump is then a lot of, etc. from the small scaled water aspirator that every minute provides only several waters to the giant water aspirator anti that presses the prinipal far to draw to take the 300 cfs liquid every minute from several 100 foots, ignore to press for life with the water with it, still fuel pump in the autocar, lubricate the oil pump or cool off the oil pump, still used for the household appliance,such as washing machine, dishwasher and refrigerators,, in our daily life, we are few need not to pump, the type and model numbers that therefore pumps are a lot of.We pay attention to only among them the most important a kind of. Be like the turbine, most pumps are the turbines machinery, but have no the place of the likeness with the pulsation type turbine.According to the prinipal stream work direction, we will pump to is divided into three kinds of, they respectively is:The diameter mixs the water aspirator of stream type toward type( leave the cenre type), the shaft stream type( propel the type) sum.Pump is different from turbine, various applied sizes and type that pumps did not correspond with it of arrange or the typical model set the type.The population or low-pressure sides of the pump be called to draw water the port, but the outlet or the high pressure sides be called a water port.If request liquid from low in the place extract of the pump place, the pumps of then most types all in advance to fill up pump liquid. make the pump be able to start draw to take the liquid, sample the liquid thus and availably and continuously.This also requests to draw the perpendicular height difference of take the side enough small, the pressure of the pump neighborhood is no lower than the vapor to press, making the lifting liquid make possible.What further demand notice is, must insure the low pressure for pump to flow small will cause air pocket produce.Although the turbine useds for the water almost and all, the pump almost useds for the liquid of various type, even including the solid liquid mix.The pumping of the gas or use the blower, or use the compressor. Leave the cenre type, the shaft stream type sum mixs the stream type pump of basic operate priniple is contrary to the priniple of the reaction turbine. pump to is drive by motor or other machinerieses namely, and plus a torque on the fluid, be the fluid flow through increased the fluid of angular momentum, then the place that pump offsetted the angular momentum of the increase, making capacity increase. For a diameter of typical model to type or leave the cenre type pump, water current at shaft toward the place enter and because of propeller of action is compelled to follow the diameter to jilt, can have the pan shape tank or the cover, covering objects to use in the both sides of the oar flake to lift high-efficiency, or the oar flake is an open type, thus although lowered the effciency, make the propeller become the not easy bott.Have the quiet diffusion or the leading waves in spite of, pump to usually all have a spiral ?? .If all have the fluid into from two sides of the propeller, the pump becomes the double to draw the liquid propeller. Basic information Version order: 1 ISBN: 7302067201 Country do not: China is big six Publisher: University publisher of Chin Hua Simplify to pack: Paper back 流體力學和流體機械概述 流體力學可被應用于許多方面，這使得流體力學成為所有工程和應川科學中十分重要的基礎(chǔ)學科之一。管道、水渠中的流體流動對于土木工程師來說是很重要的對像水泵、壓縮機、換熱器、噴管和火箭發(fā)動機等流體機械的研究，使得流體力學對于機械工程師來說也很重要。氣流繞過一個物體的空氣動力學現(xiàn)象是設(shè)計飛機、導彈和火箭的航空航天工程師們感興趣的基本問題因為大氣和海洋都是流體，所以對流體的研究是氣象學、水文學和海洋學的基礎(chǔ)。今天，在現(xiàn)代工程中許多新的理論把流體力學和經(jīng)典理論結(jié)合起來。例如把流體力學和電磁學理論結(jié)合在一起研究稱之為電磁流體動力學。在新)型的能量轉(zhuǎn)換裝置中，在研究星球和電離層的現(xiàn)象中電磁流體動力學是不可或缺的 我們可以看到，對于現(xiàn)代的工程師和科學家來說熟悉流體力學是十分必要的。顯而易見，流體力學及其應用是一門有著廣泛專業(yè)領(lǐng)域的學科.在固態(tài)剛體力學中，我們經(jīng)常問這樣一個問題：微團關(guān)于時間的位置函數(shù)是什么？通過這一條件其他所有的問題，例如，速度和加速度是什么，都可以回答。如果位置矢量r代表微團的位置，那么r(t)是一個非常重要的參數(shù)。 然而.在流體中我們而對的不是單個微團，我們所關(guān)注的是一個連續(xù)流實際上.我們無須跟蹤每個微團或者甚至少數(shù)幾滴液體的運動相反，要問的問題是：在空間某點（相對于任意一個固定坐標系）處，該點的速度、加速度和熱力學性質(zhì)關(guān)于時間的函數(shù)是什么？隨著時間的推移，該點的流體不斷地和流經(jīng)它的新流體發(fā)生交換作用，所以我們不跟蹤任何單個流體微團的運動但卻研究空間某點隨時問的變化情況，而不管在任一特定時間恰好是什么流體通過這種描述流體的方法叫歐拉法，與之相對的描述法叫拉格朗日法，拉格朗日方法被用于描述在剛體力學中一個微團的運動. 前面提到了一個詞：連續(xù)流從流體的角度看，該詞有什么意義？我們假設(shè)流體微團（或分子）間的距離，或者更精確地說是平均自由行程很小.我們說很小是與我們將流體力學理論應用于實際問題的物理尺寸相比而言的。在空氣動力學研究中，機翼厚度比繞過機翼的氣流的平均自由行程要大許多個量級。因此我們假設(shè)所有的（積分的）極限過程都有意義，而民在保持連續(xù)性情況F任何體積的流體都能分成更小的體積很明顯最終這種分割很難進行下去，但我們假設(shè)這分割能進行，這是因為微團的尺寸很小，從微觀的角度看，這對我們的研究沒有任何影響. 在不可壓流中，能量方程并不是必要的，因為密度是已知的。為了完整地描述流體流動，只需要求解壓力和速度。此時溫度是分離的，如果要求解溫度則需要用能量方程 流體機械是指那些把能量輸送到流體中或自流體中抽取能量的機械設(shè)備。第一類流體機械統(tǒng)稱為水泵，而第二類流體機械由渦輪機組成。雖然也涉及了其他的的機械，但重點是渦輪機械，即那些以轉(zhuǎn)軸的轉(zhuǎn)動來傳遞能量的水泵和渦輪機。常用的有三種類型的渦輪機，它們分別是：Pelton水輪機和兩種反動式渦輪機—Francis渦輪機和推進式渦輪機。Pelton渦輪機是一種脈動式的渦輪機，它包括一圈分開的環(huán)形葉片，Pelton對分開葉片的改進使水輪機能夠很好地完成工作，而且因此水輪機也得到了廣泛的應用。水的射流（或大系統(tǒng)的多個射流）方向與給定葉片的方向相反，而且打在分開的葉片上反彈回來再流向每一側(cè)，因而將沖擊力傳給葉片。當渦輪轉(zhuǎn)動時，每個后繼的葉片與射流成一條直線。 在典型的Francis渦輪機中心，水流帶著由引導葉片傳給的切向分量進入外部圓周，渦輪葉片這樣設(shè)計使得水流沿徑向流過渦輪葉片，流體失去了角動量，因此給葉片加上了一個轉(zhuǎn)矩。盡管最初的Francis渦輪機是離心式渦輪機，但目前它們通常是離心式與軸流式的結(jié)合，其葉片通常將水流方向由徑向轉(zhuǎn)為軸向。第二類反動式渦輪機，稱為推進式渦輪機，基本上是軸流式的。像Francis渦輪機一樣，推進式渦輪機也減少了流體的角動量，因而也在推進槳葉上產(chǎn)生了一個轉(zhuǎn)矩。大多數(shù)現(xiàn)代推進式渦輪機的槳葉斜度都可調(diào)，以便于在一定的排水量范圍內(nèi)維持較高的效率。這樣的裝置就稱為Kaplan渦輪機。幾乎所有的渦輪機都直接與發(fā)電機組相連接，因此渦輪機必須保持近乎不變的旋轉(zhuǎn)速度，這就是同步速度。這個由調(diào)速機維持的速度，是由發(fā)電機中電極的數(shù)目和產(chǎn)生電流的頻率來決定的。對于60赫茲（每秒鐘的循環(huán)次數(shù)）的電流，速度N（每分鐘的轉(zhuǎn)速），由公式N＝7200/np給定，而np是發(fā)電機的電極數(shù)，而且必須是偶數(shù)。脈動式渦輪機和反動式渦輪機之間最基本的區(qū)別是反動式渦輪機完全被液體包圍，而脈動式渦輪機則不是?？梢钥吹?，Pelton水輪機必須從壓力不變的射流獲得能量，因而能量僅可以從流體的動能中獲得。前池或渠首的水由一個稱為引水管道的導管傳向渦輪機，而此時則需要一個精心設(shè)計的噴管來提高射流速度井使可獲得的能量最大化。排水量由一個針型閥控制，而且一個旁通閥或射流變流裝置常用來保護這個系統(tǒng)，防止系統(tǒng)內(nèi)流量急劇減少。如果針型閥必須迅速關(guān)掉的話，一個溢流水箱也可以作為替代品來減少水波壓力或水錘的影響。由于尾流不可能再恢復流體的剩余能量，水流入放水渠或尾流水面以下的路徑對Pelton水輪機的性能不產(chǎn)生任何影響。Pelton水輪機通常是安裝在一個水平軸線上，并且直接和發(fā)電機相連接，經(jīng)常是兩個水輪機平衡地安裝在發(fā)電機的兩邊共同驅(qū)動同一個轉(zhuǎn)軸。 雖然渦輪機偶爾用于驅(qū)動一些小型機械，但他們大體上幾乎全部用于大型貴重設(shè)備的商用發(fā)電上。應用于工業(yè)上的只有三種最基本的類型。實際上，這三種類型的渦輪機即可覆蓋所有的工業(yè)操作條件。另一方面，泵的種類則很多，從每分鐘提供只有幾滴水的小型水泵到從幾百英尺遠的壓頭每分鐘汲取300 cfs液體的巨型水泵不等、不管是用它給生活用水加壓，還是汽車中的燃油泵、潤滑油泵或冷卻油泵，還是用于家用電器如洗衣機、洗碗機以及電冰箱，在我們的日常生活中，我們很少不用到泵，因此泵的類型和型號很多。我們只關(guān)注其中最重要的一種。像渦輪機一樣，大多數(shù)的泵是渦輪機械，但與脈動式渦輪機毫無相似之處。根據(jù)主要的流功方向，我們將泵分為三種，它們分別是：徑向式（離心式）、軸流式（推進式）和混流式水泵。泵與渦輪機不同，泵的多種應用尺寸以及類型并沒有與之相應的布置或典型安裝類型。泵的人口或低壓側(cè)稱為汲水口，而出口或高壓側(cè)就稱為出水口。如果將液體從低于泵所在的位置抽出，則多數(shù)類型的泵都要求事先將泵裝滿液體．使得泵可以開始汲取液體，從而有效地連續(xù)抽取液體。這也要求汲取側(cè)上的垂直高度差足夠小，泵附近的壓力不低于蒸氣壓，使得提升液體成為可能。更進一步需要注意的是，必須確保泵在流動時的低壓小會導致氣穴產(chǎn)生。雖然渦輪機幾乎全部用于水，但泵卻幾乎用于各種類型的液體，甚至包括固液混合物。氣體的抽運或者用鼓風機，或者用壓縮機。離心式、軸流式和混流式泵的基本工作原理與反動式渦輪機的原理相反．即泵由馬達或其他機械來驅(qū)動，并在流體上加上一個扭矩，當流體流過時就增加了流體的角動量，然后泵的位置抵消了增加的角動量，使得能量增加。 對于一個典型的徑向式或離心式泵，水流在軸向處進入而且由于推進器的作用被迫沿徑向甩出，在槳片的兩面可以有盤形槽或覆蓋物用來提高效率，或者槳片是開放式的，這樣雖然降低了效率，但使推進器變得不易堵塞。不管有沒有靜擴散或引導波，泵通常都有一個螺旋形腔。如果從推進器的兩側(cè)都有流體進入，泵就成為雙汲液推進器。