汽車發(fā)動機電動風扇冷卻系統(tǒng)的設計
汽車發(fā)動機電動風扇冷卻系統(tǒng)的設計,汽車發(fā)動機,電動,風扇,冷卻系統(tǒng),設計
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譯文題目： COOLING SYSTEM
冷卻系統(tǒng)
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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)動機冷卻系統(tǒng)的一項研究：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)動機內(nèi)部的冷卻液通道。安裝噴射泵是用來從外部系統(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)燃機的冷卻系統(tǒng)。?
精通設計的人都知道，發(fā)動機冷卻系統(tǒng)的主要目的是將發(fā)動機產(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。在其最簡單的形式中，冷卻系統(tǒng)理應包括局部鑲嵌發(fā)動機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，并且是最原始應用在內(nèi)燃機發(fā)動機上的冷卻系統(tǒng)。?
現(xiàn)如今，高速運轉(zhuǎn)的發(fā)動機,空冷已經(jīng)不足滿足發(fā)動機的冷卻需求了；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，然后安裝導管從發(fā)動機冷卻通道中將冷卻劑移出來（這種冷卻劑從發(fā)動機中吸收熱量，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，通常會在冷卻液管道中安裝一個節(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），同時極少的熱量從燃燒室傳遞到冷卻液，這對發(fā)動機的高效運轉(zhuǎn)很有益。溫度越高，對冷卻系統(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（?精通設計的人熟知的部分），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相當昂貴。?
第二，水冷系統(tǒng)也存在氣穴問題，氣穴指的是當液體由于減壓而沸騰時，液體中就會產(chǎn)生氣泡，然而，這些氣體重新融入液體。氣泡存在的時間會很短；當冷卻液的壓力恢復到正常水平時這些氣泡就會自動破裂消失。氣穴的產(chǎn)生對冷卻系統(tǒng)的組成部件是有害的，因為氣泡的破裂會產(chǎn)生微沖擊，對冷卻不利，這種現(xiàn)象在冷卻系中相當常見。氣穴也會造成冷卻系統(tǒng)金屬組成機構(gòu)的表面出現(xiàn)細微的洞。
第三，發(fā)動機熄火后水冷系統(tǒng)存在沸騰問題；當發(fā)動機熄火后，冷卻液就會停止在冷卻系統(tǒng)中的循環(huán)流動。氣缸壁和排氣歧管中剩余的熱量將會被傳送至冷卻液，冷卻液吸收熱量后就會達到沸騰溫度。精通設計的人都知道，當氣體的體積超過液體流出的體積時，在正常大氣條件下溫度超過100℃，從沸騰的冷卻液中釋放的氣體增加，可能會迫使冷卻液流出冷卻系統(tǒng)，這會增加冷卻液的消耗。
第四，如果冷卻液不是連續(xù)的真空，可能會引出夾雜空氣這個問題。在先前的空冷系中，冷卻系真空會發(fā)生在膨脹室，但是以后會很明顯，在將來這個問題會得到有效的解決。?
大家熟知的一種有效的減少發(fā)動機熄火后引起的氣穴和沸騰問題的方法是增加冷卻液的壓力。然而這種方式的代價很昂貴,因為膨脹罐必須是一種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)流動的發(fā)動機冷卻系統(tǒng)。它由一個從散熱器中將冷卻液送至發(fā)動機的泵、一個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，因此那個水罐可以是質(zhì)量相對較輕的、用規(guī)定的材料做成的。?
在某種程度上U.S.Pat.No.4,?346,757?通過將冷卻系降壓來解決存在的氣穴問題。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)動機低速運轉(zhuǎn)和發(fā)動機熄火時，在冷卻系統(tǒng)中會存在很小的或者沒有壓力增加。在發(fā)動機低速運轉(zhuǎn)或熄火時，冷卻系統(tǒng)和膨脹室中的壓力會很快的達到平衡，因為在散熱器和膨脹水箱之間有規(guī)定的毛細水管。結(jié)果是，根據(jù)U.S.Pat.No.4,346,757?的設計，在發(fā)動機熄火后并沒有以任何方式強調(diào)存在的沸騰問題。
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)見到、成本低廉，但這種解決辦法既沒有強調(diào)膨脹器皿的價格昂貴及其承受的壓力能力問題，也沒有強調(diào)沸騰的冷卻液問題在方劑熄火后。?
容納壓縮空氣的膨脹器皿存在的一個問題，就是這種類型的器皿要像“呼吸”一樣經(jīng)常收縮和膨脹，每一次當進氣門打開的時候冷卻液就會從膨脹器皿里面流出來。?
提供一種帶有高壓的冷卻系統(tǒng)是很有必要的，在發(fā)動機低速運轉(zhuǎn)和熄火后其壓力保持在較低狀態(tài)。?
根據(jù)那項發(fā)明的一個方面，通過將規(guī)定的單向的氣門裝置在連接膨脹罐和內(nèi)部冷卻循環(huán)通道之間來解決這個問題。?
為了能夠達到一種充足的動作壓力，那個單向的氣門開啟的壓力大概為0.5Mpa。
?如果單向氣門的開啟壓力接近0.5Mpa,那么系統(tǒng)會提供第二個允許冷卻液從膨脹罐流向噴射泵的單向氣門。?
為了獲得一種高效的冷卻液除氣方法，一個除氣罐會作為一種連接發(fā)動機冷卻系統(tǒng)的較高位置的管道的接合點，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。
那個除氣罐的容積大概有1到5公升。
?此外，噴射泵包括一個連接膨脹罐的進氣室，一個開口朝進氣室的噴嘴并且向一個連接進氣室和混合區(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的冷卻液流的方向直徑會增加。為了能獲得充分的泵水效果，那個噴嘴的直徑大概2到4毫米，并且那個頸部的直徑大概在5到10毫米?；旌蠀^(qū)的長度大概是頸部直徑的4到10倍，混合區(qū)應該有直徑的增長，大概從頸部直徑到頸部直徑的2到3倍之間。
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