汽車發(fā)動(dòng)機(jī)電動(dòng)風(fēng)扇冷卻系統(tǒng)的設(shè)計(jì),汽車發(fā)動(dòng)機(jī),電動(dòng),風(fēng)扇,冷卻系統(tǒng),設(shè)計(jì) 畢 業(yè) 設(shè) 計(jì)（論 文）外 文 參 考 資 料 及 譯 文 譯文題目： COOLING SYSTEM 　　　　　 冷卻系統(tǒng) 學(xué)生姓名： ?！　I(yè)： 所在學(xué)院： 指導(dǎo)教師： 職　　稱： COOLING?SYSTEM BACKGROUND?AND?SUMMARY The?present?invention?relates?to?a?cooling?system?for?an?engine,?said?cooling?system?being?divided?into?an?inner?circuit?and?an?outer?circuit.The?inner?circuit?comprises?a?radiator,a?cooling?pump,?a?thermostat?housing,an?ejector?pump?and?cooling?channels?arranged?inside?the?engine..The?ejector?pump?is?arranged?to?draw?coolant?from?the?outer?system,?which?comprises?an?expansion?tank,?ducting?interconnecting?the?expansion?tank?and?the?ejector?pump?and?ducting?interconnecting?the?inner?circuit?and?the?expansion?tank?and?deliver?it?to?the?inner?system. Moreover,?the?present?invention?relates?to?an?ejector?pump?for?pressurizing?a?cooling?system?of?a?combustion?engine.? As?is?well?known?by?persons?skilled?in?the?art,?the?main?purpose?of?a?cooling?system?of?an?engine?is?to?transfer?heat?generated?in?the?engine?to?a?radiator,?where?the?heat?could?be?vented?to?the?ambient?air.?In?its?simplest?form,?a?cooling?system?could?comprise?area-increasing?metal?fins?arranged?e.g.?on?cylinder?walls?of?the?engine?to?be?cooled.?This?type?of?cooling?is?generally?referred?to?as?air-cooling,?and?was?the?first?cooling?system?used?on?internal?combustion?engines.? On?modern,?high?performance?engines,?air-cooling?is?not?sufficient?to?cool?the?engine;?instead,a?cooling?system?with?a?coolant?is?arranged.?The?coolant?is?usually?water?mixed?with?anti-freezing?and?anti-corrosion?agents?and?the?ducting?is?arranged?to?move?the?coolant?from?cooling?channels?in?the?engine(where?the?coolant?absorbs?heat?from?the?engine,?hence?cooling?it)to?a?radiator,?where?the?absorbed?heat?is?vented?to?the?ambient?air.?This?type?of?cooling?is?generally?referred?to?as?water-cooling,?and?is?much?more?sufficient?than?air-cooling.. In?order?to?ensure?a?cooling?that?is?not?too?great,?and?not?too?small,?there?is?usually?provided?a?thermostat?in?the?coolant?ducting,.?The?purpose?of?the?thermostat?is?to?redirect?coolant?to?bypass?the?radiator?if?the?coolant?should?be?cooler?than?desired. There?are?however?some?problems?to?be?solved?relating?to?water?cooling.Firstly,theree?is?a?trend?towards?higher?coolant?temperatures;?a?high?coolant?temperature?gives?a?higher?maximum?cooling?rate(due?to?a?larger?temperature?difference?between?the?coolant?and?the?ambient?air)and?also?less?heat?transfer?from?the?engine’s?combustion?chambers?to?the?coolant,?which?is?beneficial?for?engine?efficiency.?The?higher?temperatures?lead?to?higher?stress?levels?on?cooling?system?components?made?of?plastic?materials?or?rubber.?Especially?the?expansion?chamber?(a?component?well?known?by?persons?skilled?in?art)?is?a?component?that?gets?significantly?more?expensive?if?it?should?stand?elevated?coolant?temperatures.? Secondly,?water-cooling?system?have?problems?with?cavitations;?cavitations?means?that?a?liquid?is?forced?to?boil?by?decompression,?which?gives?gas?bubble?in?the?liquid;?these?gas?bubbles?have,?however,?a?very?short?life;?as?soon?as?the?pressure?in?the?liquid?returns?to?normal?levels,?the?bubbles?will?implode?to?liquid.Cavitation?is?detrimental?to?cooling?system?components?due?to?the?“micro-shocks”?resulting?from?the?bubble?implosions,?and?is?rather?common?in?cooling?system.?The?results?of?cavitations,?e.g.?small?“holes”?in?metal?components?constituting?the?cooling?system,?could?be?seen?e.g.?on?pumping?fins.? Thirdly,?water-cooling?system?have?problems?with?boiling?after?engine?shut-off;?after?the?engine?has?been?shut?off,?the?coolant?will?stop?circulating?in?the?cooling?system.?Remaining?heat?from?the?cylinder?walls?and?the?exhaust?manifold?will?be?transferred?to?the?coolant,?which?mightreach?boiling?temperature.?As?is?well?known?by?persons?skilled?in?the?art,?the?volume?of?gas?exceeds?the?volume?of?the?liquid?it?emanates?from,under?normal?atmospheric?conditions?by?a?factor?exceeding?100.The?volume?increase?emanating?from?boiling?might?force?coolant?out?from?the?cooling?system,?which?leads?to?increased?coolant?consumption. Fourthly,air?entrainment?might?(or?rather,?will)?pose?a?problem?if?the?coolant?is?not?demarcated?continuously.?In?prior?art?system,?the?demarcation?of?the?coolant?will?take?place?in?the?expansion?chamber,?but?as?will?be?evident?in?the?following,?this?is?a?solution?that?will?not?be?very?efficient?in?the?future.? One?efficient,?known,?way?of?reducing?the?problems?with?cavitations?and?boiling?after?engine?shut-off?is?to?increase?the?coolant?pressure.?This?is?however?rather?expensive,?since?the?expansion?tank?must?be?a?vessel?standing?high?pressures,?i.e.a?vessel?having?thick?walls.? U.S.Pat.No.4,?346,757?describes?an?automotive?vehicle?cooling?system?having?a?radiator?connected?to?the?engine?coolant?jacket?for?circulation?of?coolant,?a?pump?delivering?coolant?from?the?radiator?to?the?engine,?a?non-pressurized?reservoir?bottle,?or?expansion?vessel,?communicating?with?a?radiator?and?having?a?make-up?line?communicating?with?a?Venturi?in?a?recirculation?line?around?the?pump?directing?coolant?from?the?outlet?to?the?pump?inlet.?The?Venturi?allows?make-up?coolant?to?be?added?from?the?reservoir?bottle?at?atmospheric?pressure?so?that?the?bottle?can?be?of?a?relatively?light-weight?gauge?material. U.S.Pat.No.4,?346,757?solves,?in?part,?the?problem?with?cavitations?by?putting?the?cooling?system?under?pressure;?however,?deacration?of?the?coolant?takes?place?in?the?expansion?vessel,?which?requires?a?constant?stream?of?coolant?from?the?cooling?system?to?the?expansion?vessel.?At?low?engine?speed,?and?as?the?engine?is?shut?off,?there?will?be?only?a?small,?or?no,?pressure?increase?in?the?cooling?system,?since?the?pressure?in?the?cooling?system?and?the?expansion?chamber?will?be?equalized?rapidly?at?low?engine?speeds?or?as?the?engine?is?shut?pff,due?to?the?provision?of?a?capillary?hose?(34)?between?the?radiator?and?the?expansion?vessel.Consequently,the?design?according?to?U.S.Pat.No.4,346,757?does?not?in?any?way?address?the?problem?of?boiling?after?engine?shut-off.? U.S.Pat.No.6,?886,503?describe?s?a?cooling?system?wherein?the?internal?pressure?is?increased?by?letting?in?compressed?air?from?a?turbocharger?into?the?expansion?vessel.?Although?simple?and?cost?efficient,?this?solution?addresses?neither?the?problem?of?expensive,?pressure?capable?expansion?vessels?nor?coolant?boiling?after?engine?shut-off. One?problem?with?subjecting?an?expansion?vessel?for?compressed?air,?is?that?this?type?of?vessel?will”?breathe”?frequently?and?coolant?can?escape?from?the?vessel?each?time?the?inlet?valve?is?opened.? It?is?desirable?to?provide?a?cooling?system?having?an?elevated?pressure,?which?pressure?remains?at?low?engine?speed?and?after?engine?shut-off. According?to?an?aspect?of?the?invention,?solved?by?the?provision?of?a?one-way?valve?placed?in?a?ducting?interconnecting?the?expansion?tank?and?an?inner?cooling?circuit. In?order?to?reach?a?sufficient?working?pressure,?the?one-way?valve?could?have?an?opening?pressure?of?about?0.5?bar.? If?the?one-way?valve?has?an?opening?pressure?of?about?0.5?bars,?a?second?one-way?valve?allowing?a?coolant?flow?from?the?expansion?tank?towards?the?ejector?pump?is?preferably?provided. In?order?to?obtain?an?efficient?deacration?of?the?coolant,?a?deacration?tank?could?serve?as?a?junction?for?a?ducting?from?an?elevated?position?in?the?engine?cooling?system,?a?ducting?from?an?inlet?of?the?coolant?pump,?a?ducting?from?a?top?portion?of?the?radiator,?and?the?ductinginterconnecting?the?inner?circuit?and?the?expansion?tank. The?deacration?tank?could?have?a?volume?of?about?1-5?liter.? Furthermore,?the?ejector?pump?comprises?chamber?connected?to?an?expansion?tank,?a?nozzle?opening?in?the?inlet?chamber?and?ejecting?a?flow?of?coolant?towards?a?neck?connecting?the?inlet?chamber?and?a?mixing?zone?having?an?increasing?diameter?in?a?flow?direction?of?the?coolant?flow?ejected?from?the?nozzle.?In?order?to?get?a?sufficient?pumping?effect,?the?nozzle?diameter?could?be?about?2-4?mm?and?the?neck?diameter?could?be?about?5-10?mm.The?length?of?the?mixing?zone?could?be?about?4?to?10?times?the?diameter?of?the?neck,?and?the?mixing?zone??could?have?a?diameter?increasing?from?the?neck?diameter?to?about?2?to?3?times?the?diameter?of?the?neck. 冷卻系統(tǒng) 背景和總結(jié) 目前關(guān)于發(fā)動(dòng)機(jī)冷卻系統(tǒng)的一項(xiàng)研究：冷卻系統(tǒng)可以分為內(nèi)循環(huán)和外循環(huán)。內(nèi)循環(huán)包括散熱器，冷卻水泵，節(jié)溫器殼體，噴射泵以及安裝在發(fā)動(dòng)機(jī)內(nèi)部的冷卻液通道。安裝噴射泵是用來(lái)從外部系統(tǒng)中獲取冷卻劑，而外部系統(tǒng)包含膨脹罐，用管道連接膨脹罐和噴射泵，并且用導(dǎo)管連接內(nèi)循環(huán)和膨脹罐，將其送入內(nèi)部系統(tǒng)。? 此外，目前發(fā)明的這種噴射泵主要用于內(nèi)燃機(jī)的冷卻系統(tǒng)。? 精通設(shè)計(jì)的人都知道，發(fā)動(dòng)機(jī)冷卻系統(tǒng)的主要目的是將發(fā)動(dòng)機(jī)產(chǎn)生的熱量傳送至散熱器，散熱器又將熱量釋放到周圍的空氣中。在其最簡(jiǎn)單的形式中，冷卻系統(tǒng)理應(yīng)包括局部鑲嵌發(fā)動(dòng)機(jī)在汽缸壁上的金屬鰭以便于冷卻。這種型的冷卻方式一般被稱為空冷，并且是最原始應(yīng)用在內(nèi)燃機(jī)發(fā)動(dòng)機(jī)上的冷卻系統(tǒng)。? 現(xiàn)如今，高速運(yùn)轉(zhuǎn)的發(fā)動(dòng)機(jī),空冷已經(jīng)不足滿足發(fā)動(dòng)機(jī)的冷卻需求了；相反，裝配了一種帶有冷卻劑的冷卻系統(tǒng)。這種冷卻劑通常是由水和防凍防腐藥劑混合而成，然后安裝導(dǎo)管從發(fā)動(dòng)機(jī)冷卻通道中將冷卻劑移出來(lái)（這種冷卻劑從發(fā)動(dòng)機(jī)中吸收熱量，從而起到冷卻效果）送至散熱器,散熱器又將吸收的熱量釋放到周圍的空氣中。這種類型的冷卻方式通常被稱為水冷，比空冷的效果好得多。 為了保證冷卻效果適宜，通常會(huì)在冷卻液管道中安裝一個(gè)節(jié)溫器，安裝節(jié)溫器的目的是如果冷卻液的溫度比理論上的低，它就會(huì)改變冷卻液流向的散熱器的途徑。? 然而，水冷系仍然存在一些問(wèn)題需要解決。第一，高溫冷卻液存在一種傾向，冷卻液溫度越高，產(chǎn)生的冷卻速率越大（由于周圍空氣和冷卻液的溫度存在差異），同時(shí)極少的熱量從燃燒室傳遞到冷卻液，這對(duì)發(fā)動(dòng)機(jī)的高效運(yùn)轉(zhuǎn)很有益。溫度越高，對(duì)冷卻系統(tǒng)的那些由塑料材料或者合成橡膠組成部分的壓力也越高。尤其是膨脹室（?精通設(shè)計(jì)的人熟知的部分），如果要求膨脹室能夠承受逐漸升高的冷卻液溫度，膨脹室的組成部分會(huì)相當(dāng)昂貴。? 第二，水冷系統(tǒng)也存在氣穴問(wèn)題，氣穴指的是當(dāng)液體由于減壓而沸騰時(shí)，液體中就會(huì)產(chǎn)生氣泡，然而，這些氣體重新融入液體。氣泡存在的時(shí)間會(huì)很短；當(dāng)冷卻液的壓力恢復(fù)到正常水平時(shí)這些氣泡就會(huì)自動(dòng)破裂消失。氣穴的產(chǎn)生對(duì)冷卻系統(tǒng)的組成部件是有害的，因?yàn)闅馀莸钠屏褧?huì)產(chǎn)生微沖擊，對(duì)冷卻不利，這種現(xiàn)象在冷卻系中相當(dāng)常見(jiàn)。氣穴也會(huì)造成冷卻系統(tǒng)金屬組成機(jī)構(gòu)的表面出現(xiàn)細(xì)微的洞。 第三，發(fā)動(dòng)機(jī)熄火后水冷系統(tǒng)存在沸騰問(wèn)題；當(dāng)發(fā)動(dòng)機(jī)熄火后，冷卻液就會(huì)停止在冷卻系統(tǒng)中的循環(huán)流動(dòng)。氣缸壁和排氣歧管中剩余的熱量將會(huì)被傳送至冷卻液，冷卻液吸收熱量后就會(huì)達(dá)到沸騰溫度。精通設(shè)計(jì)的人都知道，當(dāng)氣體的體積超過(guò)液體流出的體積時(shí)，在正常大氣條件下溫度超過(guò)100℃，從沸騰的冷卻液中釋放的氣體增加，可能會(huì)迫使冷卻液流出冷卻系統(tǒng)，這會(huì)增加冷卻液的消耗。 第四，如果冷卻液不是連續(xù)的真空，可能會(huì)引出夾雜空氣這個(gè)問(wèn)題。在先前的空冷系中，冷卻系真空會(huì)發(fā)生在膨脹室，但是以后會(huì)很明顯，在將來(lái)這個(gè)問(wèn)題會(huì)得到有效的解決。? 大家熟知的一種有效的減少發(fā)動(dòng)機(jī)熄火后引起的氣穴和沸騰問(wèn)題的方法是增加冷卻液的壓力。然而這種方式的代價(jià)很昂貴,因?yàn)榕蛎浌薇仨毷且环N能承受高溫高壓的容器，一種壁很厚的容器。? U.S.Pat.No.4,?346,757?描述了一種由于散熱器與冷卻劑夾連接而使冷卻液循環(huán)流動(dòng)的發(fā)動(dòng)機(jī)冷卻系統(tǒng)。它由一個(gè)從散熱器中將冷卻液送至發(fā)動(dòng)機(jī)的泵、一個(gè)常壓蓄水瓶或者膨脹容器組成，連接散熱器并且有結(jié)構(gòu)線與文丘里管圍繞泵再循環(huán)并指導(dǎo)冷卻液從泵出口流向泵入口。在大氣壓力下文丘里管可以從蓄水罐里添加冷卻液，因此那個(gè)水罐可以是質(zhì)量相對(duì)較輕的、用規(guī)定的材料做成的。? 在某種程度上U.S.Pat.No.4,?346,757?通過(guò)將冷卻系降壓來(lái)解決存在的氣穴問(wèn)題。然而，冷卻液除氣代替了膨脹容器,這就要求從冷卻系統(tǒng)到膨脹水箱要有連續(xù)的水蒸氣。在發(fā)動(dòng)機(jī)低速運(yùn)轉(zhuǎn)和發(fā)動(dòng)機(jī)熄火時(shí)，在冷卻系統(tǒng)中會(huì)存在很小的或者沒(méi)有壓力增加。在發(fā)動(dòng)機(jī)低速運(yùn)轉(zhuǎn)或熄火時(shí)，冷卻系統(tǒng)和膨脹室中的壓力會(huì)很快的達(dá)到平衡，因?yàn)樵谏崞骱团蛎浰渲g有規(guī)定的毛細(xì)水管。結(jié)果是，根據(jù)U.S.Pat.No.4,346,757?的設(shè)計(jì)，在發(fā)動(dòng)機(jī)熄火后并沒(méi)有以任何方式強(qiáng)調(diào)存在的沸騰問(wèn)題。 U.S.Pat.No.6,886,503?描述了一種冷卻系統(tǒng)，其中內(nèi)部的壓力通過(guò)渦輪增壓器將壓縮的空氣送至膨脹容器而增加。雖然結(jié)構(gòu)見(jiàn)到、成本低廉，但這種解決辦法既沒(méi)有強(qiáng)調(diào)膨脹器皿的價(jià)格昂貴及其承受的壓力能力問(wèn)題，也沒(méi)有強(qiáng)調(diào)沸騰的冷卻液?jiǎn)栴}在方劑熄火后。? 容納壓縮空氣的膨脹器皿存在的一個(gè)問(wèn)題，就是這種類型的器皿要像“呼吸”一樣經(jīng)常收縮和膨脹，每一次當(dāng)進(jìn)氣門(mén)打開(kāi)的時(shí)候冷卻液就會(huì)從膨脹器皿里面流出來(lái)。? 提供一種帶有高壓的冷卻系統(tǒng)是很有必要的，在發(fā)動(dòng)機(jī)低速運(yùn)轉(zhuǎn)和熄火后其壓力保持在較低狀態(tài)。? 根據(jù)那項(xiàng)發(fā)明的一個(gè)方面，通過(guò)將規(guī)定的單向的氣門(mén)裝置在連接膨脹罐和內(nèi)部冷卻循環(huán)通道之間來(lái)解決這個(gè)問(wèn)題。? 為了能夠達(dá)到一種充足的動(dòng)作壓力，那個(gè)單向的氣門(mén)開(kāi)啟的壓力大概為0.5Mpa。 ?如果單向氣門(mén)的開(kāi)啟壓力接近0.5Mpa,那么系統(tǒng)會(huì)提供第二個(gè)允許冷卻液從膨脹罐流向噴射泵的單向氣門(mén)。? 為了獲得一種高效的冷卻液除氣方法，一個(gè)除氣罐會(huì)作為一種連接發(fā)動(dòng)機(jī)冷卻系統(tǒng)的較高位置的管道的接合點(diǎn)，連接冷卻水泵的入口的管道，一種連接于散熱器頂部的管道，并且這種管道連接在內(nèi)部循環(huán)和膨脹罐之間。 那個(gè)除氣罐的容積大概有1到5公升。 ?此外，噴射泵包括一個(gè)連接膨脹罐的進(jìn)氣室，一個(gè)開(kāi)口朝進(jìn)氣室的噴嘴并且向一個(gè)連接進(jìn)氣室和混合區(qū)的頸部噴射冷卻液，這種混合區(qū)在流向從噴嘴里噴射出來(lái)的冷卻液流的方向直徑會(huì)增加。為了能獲得充分的泵水效果，那個(gè)噴嘴的直徑大概2到4毫米，并且那個(gè)頸部的直徑大概在5到10毫米?；旌蠀^(qū)的長(zhǎng)度大概是頸部直徑的4到10倍，混合區(qū)應(yīng)該有直徑的增長(zhǎng)，大概從頸部直徑到頸部直徑的2到3倍之間。