調(diào)整臂外殼（前剎車(chē)）加工工藝規(guī)程及專(zhuān)用夾具設(shè)計(jì)

資源目錄里展示的全都有，所見(jiàn)即所得。下載后全都有,請(qǐng)放心下載。原稿可自行編輯修改=【QQ：401339828 或11970985 有疑問(wèn)可加】 參考文獻(xiàn) 1. Silverman, M.P., 1993. The Wirbelrohr’s Roar. Cambridge University Press, Chpt 6, pp: 221-240. 2. Ranque, G., 1993. Experiences sur la détente giratore avec productions simulanees d’un echappement d’air chaud et d’um echappement d’air froid. Bull. Soc. France Phys., 1128: (J. Phys. Radium, 4, Ser.7). 3. Dissler, R.G. and M. Permutter, 1960. Analysis of the flow and energy separation in a turbulent vortex. Int. J. Heat Mass Transfer, 1: 173-191. 4. Gulyaev, A., 1966. Vortex tube and the vortex effect, soviet physics. Tech. Phys., 10 (10): 326-331. 5. Hilsch, R., 1947. The use of the expansion of gases in a centrifugal field as cooling process. Rev. Sci. Instrum., 18 (2): 108-1113. 6. Lewins J. and A. Benjan, 1999. Vortex tube optimisation theory. J. Energy, 24: 931-943. 7. Saidi, M.H. and M.R. Allaf Yazdi, 1999. Energy model of a vortex tube system with experimental results. J. 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Tools Manuf., 45: 687- 694. 附件1 用于金屬切削的空冷技術(shù) ---------布賴恩博斯韋爾和蒂拉克 機(jī)械工程學(xué)系，科廷科技大學(xué)， 郵政總局信箱U1987，西澳大利亞珀斯6845 摘要： 空氣冷卻干燥加工都是切割金屬行業(yè)為處理長(zhǎng)期運(yùn)行時(shí)為延長(zhǎng)刀具壽命，降低機(jī)床故障和盡量減少在刀尖產(chǎn)生的熱量等問(wèn)題進(jìn)行試驗(yàn)所獲得的可能的解決方案。迄今為止，這個(gè)行業(yè)仍不得不使用大量昂貴的會(huì)造成環(huán)境破壞和健康危害的冷卻劑。如今，干加工引入金屬切削行業(yè)的目的是不懈地努力減少加工費(fèi)用和化學(xué)物質(zhì)對(duì)環(huán)境的影響。現(xiàn)代加工工具已經(jīng)有能力維持其刀刃在較高溫度下切割，然而即使有了這種改善，切削刃最終也會(huì)損壞。應(yīng)用冷空氣吹入這些現(xiàn)代工具的結(jié)合面也將有助于延長(zhǎng)工具壽命，減少切削損失?？諝飧稍锛庸け挥糜诘焦ぞ呓缑嬖谶@篇文章中認(rèn)為有可能替代有害液基冷卻。然而，低對(duì)流散熱率與傳統(tǒng)空冷相關(guān)方法一般是不足以及時(shí)散掉激烈的切割產(chǎn)生的熱量，適當(dāng)?shù)哪軌蛱岣呃鋮s的過(guò)程方法，還沒(méi)有建立起來(lái)。 引言 本研究旨在探討一種被稱作朗克，希爾施渦旋管的，在加工過(guò)程中用于冷卻的有效設(shè)備。該?朗克- 希爾施渦旋管的影響是在30年代初，它的發(fā)明引起了很大轟動(dòng)，因?yàn)樗砻鳎ㄟ^(guò)壓縮空氣一管有可能產(chǎn)生熱冷空氣。起初 人們很難相信，這種裝置可以產(chǎn)生熱空氣和冷空氣并且達(dá)到有用的流量。渦旋管一個(gè)沒(méi)有移動(dòng)部件，簡(jiǎn)單的裝置同時(shí)生產(chǎn)冷，熱空氣流。但是，到目前為止，很少有確定利用冷卻工具渦流管的效率的研究。因此，為確定在刀刃上的熱效率轉(zhuǎn)移過(guò)程的一系列實(shí)驗(yàn)調(diào)查已經(jīng)開(kāi)始進(jìn)行了。這些試驗(yàn)將確定最合適的參數(shù)使用，如冷和熱空氣的質(zhì)量流量，冷熱管直徑、長(zhǎng)度，和可實(shí)現(xiàn)的冷空氣最低氣溫。風(fēng)冷從未被制造業(yè)采用是由于這樣一個(gè)事實(shí)，多年來(lái)，傳統(tǒng)的切削液已被證明是在機(jī)械加工冷卻過(guò)程中有效的方法。這項(xiàng)研究結(jié)果將證明，在很多加工設(shè)備中，空氣冷卻都可以取代傳統(tǒng)的切削液，不會(huì)減少刀具壽命或也不會(huì)造成工作質(zhì)量的下降或是影響工件表面的完成。 給工件表面提供冷空氣的朗克，希爾施渦旋管的使用說(shuō)明表明提高空冷性能的重要。刀具結(jié)合界面的溫度記錄清楚地表明，刀刃的溫度有顯著的減少。用顯微鏡觀察可發(fā)現(xiàn)，這種溫度減緩降低了機(jī)械齒面的磨損。因此，當(dāng)?shù)睹嬗蔑L(fēng)冷時(shí)，監(jiān)測(cè)后刀面磨損的發(fā)展情況，顯示著被延長(zhǎng)了的刀具壽命。 該?朗克，希爾施渦管[1]是一個(gè)了不起的設(shè)備，它能夠同時(shí)獨(dú)立為兩個(gè)不同的氣流，一股比進(jìn)來(lái)的空氣熱和另一股比進(jìn)來(lái)的空氣冷，其間沒(méi)有任何移動(dòng)部分參與。該設(shè)備分離產(chǎn)生的冷空氣和熱空氣穿過(guò)渦流管時(shí)的溫度是尚未完全清楚。這是一個(gè)被稱為麥克斯韋妖怪，一個(gè)幻想不經(jīng)任何工作就能分離熱量的裝置。這種渦管基本上包括三個(gè)管和一個(gè)使壓縮空氣在冷管處的溫度較低的供應(yīng)裝置。 ?朗克[2]試圖利用這種無(wú)運(yùn)動(dòng)部件就能產(chǎn)生熱空氣和冷空氣的奇怪設(shè)備的商業(yè)潛力。不幸的是，這家合資公司失敗了，渦流管也因此變得無(wú)人問(wèn)津。該裝置把冷傳到熱所依據(jù)的能量轉(zhuǎn)移原理仍然很難理解。然而，對(duì)于這個(gè)基本物理現(xiàn)象有一場(chǎng)辯論，盡管大多數(shù)研究者認(rèn)為該設(shè)備是基于互動(dòng)動(dòng)蕩，可是由壓縮和剪切的工作過(guò)程，卻表現(xiàn)出浦大衛(wèi)的戴斯勒和[3]分析。 最近，研究分為兩類(lèi)。 第一 類(lèi)稱為外部研究關(guān)注與該管的性能。它是發(fā)現(xiàn) Gulyaev [4]，該比例最低的長(zhǎng)度管的直徑是13。其他的研究建議40比50為最佳運(yùn)作。至于隔膜，最適尺寸是2:3的比例膜片直徑管的直徑。 渦流管由三個(gè)重要部分組成，空氣進(jìn)入到旋渦發(fā)電機(jī)（這增加了空氣的速度）的中間部分，冷軋管，熱管，如圖1所示。 通常熱管是約350毫米長(zhǎng)，并在底部有一個(gè)錐形閥控制流出的熱空氣量。 渦流發(fā)生器的右側(cè)是冷軋管出口。渦流發(fā)生器和冷軋管之間有個(gè)中心帶有可以很容易改變大小的孔的隔膜，。帶有可大可小孔的隔膜還可以增加或減少在寒冷的出口所得的溫度?？紤]到上述渦管，壓縮空氣以聲波速度供應(yīng)到圓形管，并產(chǎn)生一個(gè)每分鐘1萬(wàn)轉(zhuǎn)氣旋（渦流）。空氣是被迫自旋進(jìn)入中心，在那里它然后沿著熱管當(dāng)前最不抵抗氣流的道路逃離。 旋轉(zhuǎn)的空氣，因?yàn)樗^續(xù)沿管前行，直到它達(dá)到了錐形閥的地方變成了旋轉(zhuǎn)的空氣柱（渦部分內(nèi)部本身）。較慢的內(nèi)空氣柱的旋轉(zhuǎn)流動(dòng)的空氣放棄了它的熱量，讓其更快的旋轉(zhuǎn)到空氣柱外。 寒冷的空氣撞倒正奉命出的渦流發(fā)生器的旋轉(zhuǎn)空氣并且冷端的熱空氣耗盡流出的渦流管的另一端。調(diào)整錐形閥將內(nèi)置悶熱的空氣排出可以改變這兩個(gè)溫度，空氣流低至-55 ° C的由圖所示。 渦流理論 目前沒(méi)有人能確切地解釋為什么渦管會(huì)如此運(yùn)作：這個(gè)過(guò)程本身正如萊溫和Bejan [6]所述的那么簡(jiǎn)單。切向進(jìn)氣噴嘴對(duì)渦流發(fā)生器，因此可以提供一個(gè)高速旋轉(zhuǎn)產(chǎn)生的氣流旋渦。后來(lái)，有一徑向溫度梯度由管芯到管外壁增加。這是主要是因?yàn)榭諝獾膲嚎s勢(shì)能轉(zhuǎn)換為動(dòng)能，由于附近空氣中的外切向力矩進(jìn)口形成的強(qiáng)迫渦。因此，高速旋轉(zhuǎn)內(nèi)流管，遠(yuǎn)離墻壁產(chǎn)生。渦旋內(nèi)的熱管現(xiàn)有的空氣，通常與大氣溫度相等，當(dāng)旋轉(zhuǎn)氣流的渦管流進(jìn)它就擴(kuò)大了，但其溫度下降到比環(huán)境溫度低。兩氣溫的區(qū)別將導(dǎo)致溫度梯度沿管生產(chǎn)比周?chē)諝獾暮诵母涞目諝?。因此，中央空氣分子將失去熱將到達(dá)外部區(qū)域，如圖所示3。 值得注意的是，該系統(tǒng)是一個(gè)動(dòng)態(tài)的系統(tǒng)由于對(duì)管內(nèi)氣流的性質(zhì)，因此將無(wú)法達(dá)到平衡。因此，周邊的空氣有較高的動(dòng)能（溫度超過(guò)內(nèi)空氣（冷））。 一個(gè)主要的壓力梯度由于在徑向方向被迫渦將提供一個(gè)圓形旋轉(zhuǎn)的向心力，因此這將導(dǎo)致高壓的在管壁上，并低壓在中心處。當(dāng)空氣進(jìn)入到周邊地區(qū)（A），隨著它的膨脹，由于它的擴(kuò)張外部空氣得以冷卻。因此，內(nèi)核的空氣（B）會(huì)得到溫暖，因?yàn)樗怯蓧嚎s周邊膨脹的空氣。然后轉(zhuǎn)熱從內(nèi)核（B）到外核心（A）。由于內(nèi)部空氣被壓縮，自然會(huì)嘗試推著向周邊膨脹。因此，處理外核的空氣，然后加熱，由于膨脹和壓力的不同，這會(huì)導(dǎo)致對(duì)工作要做周?chē)目諝獾玫讲煌Y(jié)果收縮的空氣。因此，熱量轉(zhuǎn)移徑向向外圖所示4。當(dāng)空氣繼續(xù)沿管旋進(jìn)產(chǎn)生的更多的分離能量將發(fā)生軸向?qū)α鳎箍諝庀驘岫艘苿?dòng)。在這個(gè)進(jìn)程中，將熱量從核心轉(zhuǎn)的空氣移到外部空氣。 隨著氣流到達(dá)最熱時(shí)，一小部分的空氣將通過(guò)位于熱端的錐形閥門(mén)排出，依靠臨近中心的不良?jí)毫μ荻?，剩下的空氣將在冷端旋轉(zhuǎn)，如圖所示5。 其余部分的溫暖的空氣保持垂直流動(dòng)，其運(yùn)動(dòng)方向要么是沿管道順時(shí)針要么是逆時(shí)針。 此外，這種氣流 在管內(nèi)核心的空氣產(chǎn)生的氣流的壓力也較低。如果兩空氣流的角速度保持，這意味著任何兩個(gè)取自圖 4的粒子：示意圖陣地周邊和內(nèi)部核心空氣 圖5：在渦管氣流模式圖無(wú)論是空氣流將采取同樣的時(shí)間才能完成圍繞管周長(zhǎng)一次循環(huán)。從角動(dòng)量守恒原理，它似乎是在內(nèi)核分子角速度將增加，見(jiàn)EQ： 公式表明，在內(nèi)部的核心中，RA的值（徑向距離測(cè)量中心在管中特別關(guān)注分子）很小，應(yīng)該有一個(gè)相應(yīng)的增加分子的角速度，以便讓總的角動(dòng)量守恒系統(tǒng)。此假設(shè)是微不足道，在管道內(nèi)兩任何空氣分子的質(zhì)量差異。然而，某一角速度在內(nèi)部核心分子保持不變。這也就是說(shuō)，在渦流管內(nèi)的核心，角動(dòng)量實(shí)際上已經(jīng)失去了。由于熱量轉(zhuǎn)移到外的核心，對(duì)內(nèi)核的角動(dòng)量不保留或有更具體的跌幅，這將導(dǎo)致核心能量從內(nèi)到外轉(zhuǎn)移。 內(nèi)核的熱能損失事外核心范圍內(nèi)的空氣分子升溫。因此，外核變熱和內(nèi)核變涼。 當(dāng)達(dá)到熱極限，通過(guò)熱錐形閥和管壁（熱插座）之間的小開(kāi)口將周?chē)目諝庖莩?。不過(guò)，中央的空氣較冷，是由錐形閥軸偏轉(zhuǎn)，并繼續(xù)對(duì)從熱端流向冷管。只有最里面的空氣分子通過(guò)隔膜和從收集冷空氣的出口溢出。因此，空氣分子被分為冷流和熱流通過(guò)渦流管的冷熱兩端。 該圖 6很好的繪出了渦流管。重要的是要注意，特別是在熱端管發(fā)生分離。該錐形主軸（錐形閥），的目的是將一個(gè)寒冷的空氣逆流到管軸向地區(qū)。該隔膜（孔另一方面）是用來(lái)?yè)踔車(chē)目諝?，使中央流?huì)通過(guò)冷端溢出。渦管部件的缺少可能會(huì)造成這種錯(cuò)誤的假設(shè)，這種現(xiàn)象是違反熱力學(xué)規(guī)律的。 事實(shí)上，如果沒(méi)有在室溫下做任何工作，空氣流可以分為兩個(gè)不同的蒸汽，這一冷一熱劃分工作，似乎違背了熱力學(xué)第二定律。不過(guò)，關(guān)鍵是要提的是，盡管有這個(gè)誤導(dǎo)的觀念，可是物理保持不變。雖然，該渦管物理學(xué)是復(fù)雜的，但作為熱力學(xué)的基本原理研究，可以幫助加深對(duì)渦流管內(nèi)發(fā)生了什么進(jìn)行更深入的了解。 熱力學(xué)第一定律是關(guān)于節(jié)約能源。根據(jù)這項(xiàng)規(guī)律，在系統(tǒng)之間的反應(yīng)，它的環(huán)境，能源可以使從周?chē)邮盏皆撓到y(tǒng)與從系統(tǒng)中傳給周?chē)哪芰恐迪嗟?。這種能量可以由兩個(gè)不同狀態(tài)顯現(xiàn)：熱和功。因此，對(duì)于每一個(gè)具體的控制體積熱力學(xué)系統(tǒng)：圖7：一渦管控制體積示意圖 制冷實(shí)際情況對(duì)于確定該冷卻裝置的性能系數(shù)是如此的重要。 因此，確定性能系數(shù)的旋渦管和比較與傳統(tǒng)制冷性能系數(shù)在使用它來(lái)確定它的效率，似乎合乎邏輯。渦流管可以用作制冷設(shè)備在寒冷的管壁是用來(lái)降低溫度或作為加熱裝置，當(dāng)熱管墻是用來(lái)增加外殼溫度。應(yīng)該指出的是，對(duì)面是什么通常在熱力學(xué)看，在這種情況下渦管是一個(gè)開(kāi)放的控制儲(chǔ)存裝置。如果系統(tǒng)認(rèn)為是穩(wěn)定的狀態(tài)，然后從第一定律熱力學(xué)： 其中，DH_是系統(tǒng)焓的變化和平行的演算法之間的系統(tǒng)及其周?chē)h(huán)境的熱量交換。 讓我們假定平行的演算法近似為零，即使冷軋管上可能有霜凍，熱管是很溫暖。如果是這種情況則： 在那里，_Hc是冷流焓變化和_HH是熱焓變流。假設(shè)為理想氣體，總焓變的空氣可以寫(xiě)為： 其中，mc，在冷管的質(zhì)量流量，氫是熱管的質(zhì)量流量，Tc是冷空氣的溫度，Ti是進(jìn)風(fēng)溫度，Th是熱空氣的溫度和Cp為空氣比熱在不斷的壓力和承擔(dān)可逆的絕熱過(guò)程。通過(guò)應(yīng)用熱力學(xué)第二定律上述： 其中，_S是總熵變，q是傳熱和T為絕對(duì)溫度。 在實(shí)際的穩(wěn)態(tài)控制體積熵的變化是：熵變化的實(shí)際控制數(shù)量， 穩(wěn)定狀態(tài)是： 其中，_Sc和_Sh是從入口到出口的熵變的部分進(jìn)入寒冷的空氣管留下了，一部分是進(jìn)入熱管。 對(duì)于理想氣體（空氣）比熱，熵變化可以 在那里我的下標(biāo)，C和H分別進(jìn)流，冷流和熱流，R是理想氣體（空氣）保持不變。 自冷（或熱外觀）的影響時(shí)無(wú)運(yùn)動(dòng)部件將嘗試管壁考慮為冰箱（或競(jìng)爭(zhēng)此設(shè)備熱泵），估計(jì)其系數(shù)性能（COP）是有效的。圍繞冷卻效果可以通過(guò)放置一個(gè)寒冷的管外殼，性能系數(shù)，可計(jì)算方法是： 冷流通過(guò)冷管壁像熱（換熱器）由一些喜歡在一冷箱源（冰箱）和W在本案中是工作壓縮完成從大氣壓力和空氣溫度對(duì)管的入口條件。 其中，T2是壓縮機(jī)出口溫度和T1是壓縮機(jī)進(jìn)氣溫度（可逆的，多方過(guò)程;空氣量：N = 1.4）。如果我們考慮一個(gè)完整的系統(tǒng)，P1和T1的是大氣壓力和溫度， P2和T2的是壓縮機(jī)出口條件， 空氣被壓縮后，它在保持在高壓狀態(tài)，在當(dāng)時(shí)它冷卻大氣溫度，使音速噴嘴的入口溫度T1，相當(dāng)于T1的溫度： 方程（23）可從T2的計(jì)算式。 （24）這是一個(gè)理想的工作值，它比所需的驅(qū)動(dòng)器的實(shí)際工作較少于壓縮機(jī)。通過(guò)考慮上述方程和使用的EQ（21），對(duì)渦流管性能系數(shù)可以決定的。 實(shí)驗(yàn)分析渦管設(shè)計(jì)為了幫助比較的渦管數(shù)參數(shù)是非常有用的使用質(zhì)量分?jǐn)?shù)為冷這是可以對(duì)比以上的渦管范圍測(cè)試。此參數(shù)是簡(jiǎn)單的空氣質(zhì)量流量比率在管冷端進(jìn)口處的壓縮空氣的平均流速，。重要的是要注意氣團(tuán)在管熱端流率各不相同，從它的最高值（即等于質(zhì)量流量的壓縮空氣）到最低值（這是等于零），并顯示在橫向軸的圖表。在冷端質(zhì)量流量等于質(zhì)量差的進(jìn)氣流量和質(zhì)量流量率的冷端。因此，通過(guò)改變質(zhì)量在熱端流率，有效地控制你在制冷結(jié)束時(shí)，其最低流量的大規(guī)模最大的價(jià)值。 其中： mc =空氣質(zhì)量在冷端流率 mh=空氣質(zhì)量流率在熱端 mh=壓縮空氣的質(zhì)量流率在進(jìn) 寒冷空氣的質(zhì)量分?jǐn)?shù)為輸入壓縮空氣通過(guò)冷端釋放管的百分比。一般來(lái)說(shuō)，稍稍寒冷的空氣被釋放后，就會(huì)變得更寒冷。調(diào)節(jié)控制閥旋鈕將改變不同寒冷度的質(zhì)量分?jǐn)?shù)。將給予質(zhì)量分?jǐn)?shù)高的寒冷更大的氣流，但并沒(méi)有給盡可能低的溫度。高質(zhì)量分?jǐn)?shù)寒氣流與冷溫度組合，產(chǎn)生最大低溫冷藏能力。另一方面低質(zhì)量分?jǐn)?shù)氣流是指一股出來(lái)時(shí)體積較小且非常冷的空氣?？傊^少的空氣被釋放，空氣變得更冷。在最冷的那頭，速度對(duì)溫度下降的影響很有效，因?yàn)槿绻a(chǎn)生最低氣溫的速度是已知的，那么，壓縮空氣的壓力和冷噴嘴直徑可以達(dá)到最優(yōu)化。噴嘴直徑的減少也將迫使空氣向熱端流動(dòng)，并會(huì)導(dǎo)致對(duì)渦管效率的提高有一定影響。 估計(jì)的性能系數(shù)可以用來(lái)給出了該冷卻系統(tǒng)的制冷性能，這是一個(gè)能夠確定渦流管的性能。 這對(duì)渦流管性能系數(shù)計(jì)算用到公式（21），并發(fā)現(xiàn)了1.38的價(jià)值。與傳統(tǒng)制冷系統(tǒng)通常約為3.5的值相比，1.38這個(gè)值較低。即使這表明，渦流管是不是空調(diào)系統(tǒng)的理想器件，它仍然合適現(xiàn)場(chǎng)冷卻。對(duì)渦流管顯示設(shè)計(jì)的測(cè)試，寒冷氣流的溫度下降的寒冷的質(zhì)量分?jǐn)?shù)由、是渦流管的一個(gè)功能，如式（27）所示。從這些實(shí)驗(yàn)情況表明，噴嘴使之產(chǎn)生一個(gè)最大降溫如圖?9所示。這已是最小光圈噴嘴直徑（直徑3毫米之間的發(fā)電機(jī)和冷渦管）?？梢詮倪@些測(cè)試得出結(jié)論，冷渦發(fā)生器出口直徑越小，溫度下降越大。 檢查（圖8 - 11B條）顯示的趨勢(shì)，最低氣溫伴隨低的寒質(zhì)量分?jǐn)?shù)發(fā)生。不幸的是，該流量計(jì)沒(méi)有測(cè)量接近零的寒冷質(zhì)量分?jǐn)?shù)的能力。因此，它無(wú)法找到確切的最低氣溫出現(xiàn)時(shí)的寒冷的質(zhì)量分?jǐn)?shù)。雖然，從圖就可以假設(shè)這個(gè)值將介于0和0.1。在冷空氣出口產(chǎn)生最大的溫降，同時(shí)在熱空氣出口產(chǎn)生最大的溫升，這個(gè)結(jié)果顯示在用噴嘴 1時(shí)寒冷質(zhì)量分?jǐn)?shù)在0.6和0.7之間，如圖8所示。 此圖形9顯示了不同噴嘴直徑圖的趨勢(shì)，從0都開(kāi)始增加至最高點(diǎn)，然后有一個(gè)溫度下降趨勢(shì)。這種方式是可以預(yù)見(jiàn)的，因?yàn)樗且阎?，寒冷的質(zhì)量分?jǐn)?shù)低，一內(nèi)旋轉(zhuǎn)氣流有很高的比例加入在出口外流動(dòng)的熱空氣，因此，熱氣流的溫度下降。由于錐形閥逐漸打開(kāi)，一場(chǎng)更高的比例熱空氣逃脫出口，而其余部分則返回混入渦旋空氣中通過(guò)冷端回來(lái)。這讓熱氣流溫度增加至其最高點(diǎn)以及生成最冷空氣。繼續(xù)打開(kāi)超出其最佳位置錐形閥可以通過(guò)額外的空氣逸出，使熱空氣出口溫度降低。 該熱管的長(zhǎng)度對(duì)能源上的渦管分離有重要的影響，可以由（圖10A條，二）證明。例如，通過(guò)增加熱管長(zhǎng)度，溫度下降的快。這是由于空氣內(nèi)流有更多的時(shí)間將能量轉(zhuǎn)移到外部氣流。但是，對(duì)大于對(duì)360毫米的渦流管進(jìn)行測(cè)試顯示：一旦超出了熱管的最佳長(zhǎng)度，溫度下降速度開(kāi)始下跌。這種溫度的下降減少所造成的能量，使得外熱流量開(kāi)始讓內(nèi)流升溫，當(dāng)內(nèi)流時(shí)到達(dá)錐形閥，它返回到更冷的溫度冷端。 從圖中可以得出結(jié)論說(shuō)，所有的長(zhǎng)度，最高溫度可以通過(guò)增加0.4和0.7之間的寒冷質(zhì)量分?jǐn)?shù)進(jìn)行測(cè)試。 另外一個(gè)重要參數(shù)，對(duì)渦流管影響較大的是壓力，因?yàn)樗荆▓D11A條，乙），這表明一般通過(guò)增加更大的壓力，您會(huì)獲得一個(gè)溫度下降。薩迪和亞茲迪[7]從他們的研究還發(fā)現(xiàn)，通過(guò)增加管長(zhǎng)，溫差增大，對(duì)能源的損失減少了。 斯蒂芬[7]在他的實(shí)驗(yàn)得到那些類(lèi)似的趨勢(shì)，在米= 0.8米= 0.95間得到最高溫升。為此渦管的最高值被發(fā)現(xiàn)是在m= 0.5和m = 0.7間，如圖11 b所示：作者與斯蒂芬的渦管比較這些寒冷分?jǐn)?shù)的測(cè)試，存在幾何上的不同。 風(fēng)冷金屬切削 在刀尖嵌入的熱電偶的位置圖12上顯示，最接近被測(cè)量工具接口由13個(gè)頻道（Ch13熱電偶）。圖13顯示了渦管，產(chǎn)生的冷空氣正在走上工具界面直接在金屬切削試驗(yàn)。這一過(guò)程的空氣冷卻性能可以進(jìn)行評(píng)估，確定了此加工條件對(duì)刀具壽命等的影響。如圖14所示的在測(cè)量工具提示之前加工與記錄-5℃的溫度熱電偶2，如通道熱電偶（Ch13）和（Ch15）表示 當(dāng)空氣渦流出口已達(dá)到-30℃左右，加工開(kāi)始。正如在刀尖溫度升高的現(xiàn)象[9]，該工具上升到了60攝氏度的溫度穩(wěn)定狀態(tài)，如圖15所示。 在最后一點(diǎn)溫度下降時(shí)，表示已停止進(jìn)料，沒(méi)有更多的鐵削正在生成。這使冷卻空氣流過(guò)該工具時(shí)提供一個(gè)從減少工具的溫度，加快工具更快的散熱，如圖16所示。 在切削實(shí)驗(yàn)的過(guò)程中渦流管的霜凝可以清楚地看到確認(rèn)，渦流管是提供極冷的空氣。 空氣冷卻對(duì)刀具壽命的影響 據(jù)了解，所有的磨損機(jī)制都會(huì)減少高溫下刀具壽命[10]。 在寒冷的空氣中，應(yīng)用工具顯示會(huì)避免長(zhǎng)時(shí)間在尖端的溫度下使用工具能夠讓刀具有一個(gè)較長(zhǎng)的壽命[11]?？諝饫鋮s系統(tǒng)的效率可以顯示，磨損為干切一1分鐘，7分鐘的加工風(fēng)冷削減之間的比較。圖第17A - D顯示的后刀面磨損下一個(gè)具有63光學(xué)顯微鏡的放大倍率設(shè)定時(shí)間。 后刀面磨損的發(fā)展證明需要更長(zhǎng)的時(shí)間，發(fā)展空氣冷卻時(shí)，應(yīng)用到切削區(qū)，如圖17d所示。 經(jīng)過(guò)七年的干式加工分鐘前刀面的月牙洼磨損開(kāi)始發(fā)展，在0.5毫米的側(cè)面，如圖18a所示。干式加工將進(jìn)一步加快這一磨損率。在這個(gè)階段，刀具半徑?jīng)]有顯示出磨損跡象和頂部側(cè)面邊緣沒(méi)有明顯的缺口?？諝饫鋮s工具顯示在頂部前刀面和后刀面磨損沒(méi)有明顯的跡象是刀具磨損也大大減少。在干燥和空氣的冷卻表示，該芯片產(chǎn)生的熱量多，正在切削區(qū)慢慢消退。圖19顯示了在干燥和空氣冷卻刀尖試驗(yàn)產(chǎn)生的鐵屑。左側(cè)是干燥刀尖試驗(yàn)和右側(cè)是空氣冷卻產(chǎn)生的鐵屑。 總結(jié) 先前的研究，如劉等人。[12]證明，壓縮空氣沒(méi)有像油水乳液或水蒸汽達(dá)到工具的界面，使之良好散熱。然而，結(jié)果得到利用壓縮空氣與渦管結(jié)合表明，這種冷卻工具接口方法是有效的，與傳統(tǒng)的冷卻方法相比,格外好。在圖20中可以看出，此種方法的溫度記錄是60℃，比傳統(tǒng)的濕加工降低40℃，比干加工低了210℃。這些溫度距工具界面1毫米開(kāi)始測(cè)量，所以其在這個(gè)位置產(chǎn)生的溫度記錄要比工具表面的低一些。但是，必須假定該工具界面以及工具的測(cè)點(diǎn)的溫度將減少。因?yàn)槲覀冎?，刀具壽命和磨損機(jī)制之間的關(guān)系將由切削溫度升高顯示出來(lái)，所以是檢測(cè)空氣冷卻效率的最便捷的方法就是通過(guò)檢測(cè)刀具壽命。該工具的使用在顯微鏡的尖端檢測(cè)證實(shí)，該工具被空氣冷卻時(shí)磨損減少，具有更長(zhǎng)的刀具壽命。渦管空氣冷卻系統(tǒng)證明能夠使刀尖有效散熱，，證明空氣冷卻是一個(gè)冷卻刀具尖端的有效方法。因此，干加工進(jìn)行金屬切削時(shí)，空氣冷卻的首選方法應(yīng)納入，因?yàn)樗鼪](méi)有相關(guān)的環(huán)境問(wèn)題，并延長(zhǎng)了刀具壽命。 American Journal of Applied Sciences 6 (2): 251-262, 2009 ISSN 1546-9239 2009 Science Publications Corresponding Author: Brian Boswell, Department of Mechanical Engineering, Curtin University of Technology, GPO Box U1987, Perth Western Australia 6845 Tel: (08) 9266 3803 Fax (08) 9266 2681 251 Air-Cooling Used For Metal Cutting Brian Boswell and Tilak T Chandratilleke Department of Mechanical Engineering, Curtin University of Technology, GPO Box U1987, Perth Western Australia 6845 Abstract: Air-cooling and dry machining are both being trialled as possible solutions to the metal cutting industrys long running problems of extending tool life, reducing tool failure and minimising the heat generation at the tool tip. To date, large amounts of expensive coolant which cause both environmental damage and health hazards have had to be used. The introduction of dry machining is the goal of todays metal cutting industry that tirelessly endeavours to reduce machining costs and impact from chemicals in the environment. Modern tool tips are already capable of maintaining their cutting edge at higher temperatures, but even with these improvements in tool materials, the cutting edge will eventually break down. Applying cold air to the tool interface of these modern tool tips will also help prolong their tool life reducing the cost of metal cutting. Dry machining incorporating air being directed on to the tool interface is considered in this paper as a possible alternative for harmful liquid-based cooling. However, low convective heat removal rates associated with conventional air-cooling methods are generally inadequate for dissipating intense heat generation in the cutting processes and suitable improved cooling methodologies have yet to be established. Key words: Vortex tube, tool life, flank wear, cold fraction, coefficient of performance, air-cooled, environmentally friendly INTRODUCTION In this research examines the operational effectiveness of a Ranque-Hilsch vortex tube being used to cool tool tip during machining. The Ranque-Hilsch vortex effect was discovered in the early 1930s when it caused considerable excitement, as it demonstrated that it was possible to produce hot and cold air by supplying compressed air to a tube. At first it is hard to believe that such a device can produce hot and cold air and at a useful flow rate. The vortex tube is a simple device with no moving parts, which simultaneously produces cold and hot air streams. However, to date, there is little research in determining the efficiency of using a vortex tube in cooling tool tips. Therefore, to establish the effectiveness of the heat transfer process on the tool tip a series of experimental investigations has been carried out. These tests will determined the most suitable parameters to use, like mass flow rate of cold and hot air, cold and hot tube diameter with respect to tube length, to achievable minimum cold air temperatures. Air-cooling has never been taken seriously by the manufacturing industry due to the fact that for many years traditional cutting fluid has been shown to be effective in cooling tool tips during the machining processes. The outcome of this research will prove that air-cooling can replace traditional cutting fluid for many machining applications, without any reduction in tool life or reduction in quality of work piece surface finish. The introduction of using a Ranque-Hilsch Vortex Tube to provide cold air to the tool interface is shown to significantly improve the performance of air-cooling. Recorded tool tip interface temperatures clearly indicate that there is a highly significant reduction in tool tip temperature. This reduction in temperature slows the wear mechanisms as shown by the reduced flank wear when examined under a microscope. Therefore, monitoring the growth of the flank wear indicates the increased tool life when being air-cooled. The Ranque-Hilsch vortex tube1 is a remarkable device that is able to separate airflow into two different streams simultaneously, one hotter than the inlet air and the other cooler, without any moving parts being involved. The mechanism producing the temperature separation of cold air and hot air when passing through the vortex tube is not yet fully understood. This device has been described as Maxwells demon, a fanciful means of separating heat from cold without work. The Am. J. Applied Sci., 6 (2): 251-262, 2009 252 vortex tube basically consists of three pipes and a supply of compressed air to achieve a moderately low temperature at the cold outlet. Ranque2 attempted to exploit the commercial potential for this strange device that produced hot and cold air with no moving parts. Unfortunately, this venture failed and the vortex tube slipped into obscurity. The mechanism underlying the energy transfer from the cold to the hot flow remains elusive. However, there is debate even as to the basic physics of the phenomenon, while the majority of researchers suggest the mechanism is based on the interactions of turbulence, compressibility and shear work as shown by the analysis of Deissler and Perlmutter3. Recent research has been divided into two categories. The first category termed as external studies were concerned with the performance of the tubes. It was found by Gulyaev4 that the minimum ratio of the length of the tube to that of its diameter was thirteen. Other research suggested a ratio of forty to fifty for optimum operation. As for the diaphragm, the optimum dimension is a ratio of 2:3 for the diaphragm diameter to tube diameter. The vortex tube consists of three important parts the mid-section where the air enters into the vortex generator (which increases the speed of the air), the cold tube and the hot tube as shown in Fig. 1. Normally the hot tube is about 350 mm long and at the end there is a conical valve which controls the amount of hot air escaping. On the right side of the vortex generator is the cold tube exit. Between the vortex generator and the cold tube there is a diaphragm, with a central hole that can be easily changed. Diaphragms with large or small holes can also increase or decrease the temperature obtained at the cold exit. Considering the above vortex tube, the compressed air is supplied circumferentially into the tube at sonic speed and creates a cyclone (vortex) spinning at a million revolutions per minute. The air is forced to spin inward to the centre where it then escapes up along the hot tube as this path presents the least resistance to the airflow. The air continues to spin as it travels along the tube until it meets the conical valve where it turns part of the spinning air column (vortex) inside itself. The slower moving air inside column of the spinning air gives up its heat to the faster spinning outside column of air. The cold air travelling down the spinning air is now directed out the cold end of the vortex generator and the hot air is exhausted out of the other end of the vortex tube. Adjusting the conical valve built into the hot air exhaust can change the temperature of these two air streams to as low as 55C as shown by Fig. 2. Fig. 1: Diagram of the Hilsch Vortex Tube5 -60-50-40-30-20-10010050100150Time (s)Nozzle exit temperature (C) Fig. 2: Temperature recoded at cold nozzle exit having an inlet pressure of 1Mpa VORTEX THEORY Currently no one can definitively explain why the vortex tube operates as it does: the process itself is straightforward as outlined by Lewins and Bejan6. The inlet nozzle is tangential to the vortex generator and therefore can provide a high speed rotating airflow inside the vortex generator. Subsequently, there is a radial temperature gradient increasing from the inner core of the tube to the outside wall of the tube. This is primarily because of the potential energy of compressed air converting to kinetic energy due to the forced vortex caused by the external torque near the tangential air inlet. Therefore the high-speed swirling flow inside the tube and away from the walls is created. The existing air inside the vortex hot tube is normally at the atmospheric temperature and so, when the rotating flow enters the vortex tube it expands and its temperature drops to a temperature lower than the ambient temperature. The difference between these two temperatures will lead to a temperature gradient along the tube producing colder peripheral air than the core air. As a result, the central air molecules will lose heat to those in the outer region as shown in Fig. 3. It is notable that this system is a dynamic system due to the nature of the airflow in the tube and so will not reach equilibrium. Hence the peripheral air has a higher kinetic energy (hotter) than the inner air (colder). Am. J. Applied Sci., 6 (2): 251-262, 2009 253 Fig. 3: Radial heat convection in vortex tube due to the expansion of the compressed air The existence of a major pressure gradient due to the forced vortex in the radial direction will provide a centripetal force for circular swirling and therefore it will lead to a high pressure at the tube wall and low pressure at the centre. When the air enters to peripheral region (A), as it expands, the outer air will be cooled due to its expansion. Consequently, the inner core air (B) will get warm because it is compressed by the expansion of the peripheral air. Heat is then transferred from the inner core (B) to the outer core (A). As the inner air is being compressed, it naturally tries to push against the periphery by expanding. Work is therefore done on the outer core air, which then gets heated and the difference in pressures results in the expansion and contraction of the air, which causes work to be done on the peripheral air. Therefore, heat is transferred radially outward as shown in Fig. 4. When the air continues to swirl along the tube the more energy separation will occur by axial convection while it moves towards the hot end. During this progression, the heat will be transferred from the core air to the outer air. As the airflow reaches the hot end a fraction of the air will exhaust through the conical valve, which is located at the hot end and the remaining air flow will spin back towards the cold end due to the adverse pressure gradient near the centre as shown in Fig. 5. The remaining portion of the warm air preserves its direction of motion in the vertical flow that is either in a clockwise or anticlockwise manner around the circumference of the tube. Furthermore, this air stream resides at the inner core of the tube where the air pressure there is lower. If the angular velocities of both the air streams are preserved, it means that any two particles taken from Fig. 4: Schematic positions of the peripheral and inner core air Fig. 5: A diagram of the airflow pattern in vortex tube both the air streams will take the same time to complete a revolution around the circumference of the tube. From the principle of conservation of angular momentum, it seems that the angular velocity of the inner core molecules would increase, by the Eq: 2a aaam rconstant = (1) The equation implies that in the inner core, where the value of ra (radial distance measured from the centre of the tube to the particular molecule in concern) is small, there should be a corresponding increase in the molecules angular velocity, wa, to allow for the conservation of the total angular momentum in the system. This is assuming that there is negligible mass difference, ma, between any two-air molecules in the tube. However, the angular velocity of a particular molecule in the inner core remains unchanged. This means that angular momentum has actually been lost from the inner core of the vortex tube. Angular momentum of the inner core is not preserved or more specifically decreases, due to heat transferred to the outer core. This results in the transfer of energy from the inner core to the outer core. The loss in heat energy Am. J. Applied Sci., 6 (2): 251-262, 2009 254 Fig. 6: Schematic vortex tube diagram showing tangential air inlet from the inner core goes into heating up of the air molecules in the outer core. Hence, the outer core becomes hotter and the inner core becomes cooler. Upon reaching the hot end, the hotter peripheral air escapes through the small openings between the conical valve and the tube wall (hot outlet). However, the central air that is cooler is deflected by the tapered valve spindle and continues its travel from the hot end towards the cold tube. Only the innermost air molecules pass through the diaphragm and exit through the cold end where it is collected. As a result, the air molecules are separated into a hot stream and cold stream through the hot and cold ends of the vortex tube respectively. The Fig. 6 shows a good view of the vortex tube. It is important to note that separation takes place specifically at the hot end tube. The purpose of the tapered spindle (conical valve) is to direct the cold air to the axial region of the tube in a counter flow. The diaphragm (orifice) on the other hand is used to block the peripheral air, so that the central flow will escape through the cold end. The absence of moving parts in the vortex tube may create this wrong supposition that this phenomenon is violating thermodynamics law. The fact that without doing any work at room temperature, a stream of air can be divided into two different steams, one cooler and one hotter, seems to contradict the second law of thermodynamics. However, it is important to mention that despite this misleading belief the physics remains intact. Although, the physics of the vortex tube is complicated, the study of the basic principles of thermodynamics can help to gain a better understanding of what is happening inside a vortex tube. The first law of thermodynamics is about the conservation of energy. According to this law, during a reaction between a system and its ambient, the energy that can be received from the ambient to the system is exactly equal to the energy that is lost from the system to the ambient. This energy can be seen in two different states: Heat and Work. Hence, for every thermodynamics system with a specific control volume: Fig. 7: Schematic control volume of a vortex tube 2iC.Viii2eeeec.vvQm (hgz )2vm (hgz )W2+=+? (2) where cvQ?is the rate of heat flow, which transfers through the control volume boundary and cvW?is the work that can be done by the system on its ambient, m ? is the mass flow rate, h is the enthalpy of the air stream, v is the air stream velocity, z is the distance between the air stream and a source point and the subscripts i and e refer to inlet and outlet streams. Assuming that the vortex tube is well insulated, then the heat transfer between the system and the ambient can be taken as cvQ?equal to zero, with vi and ve also equal to zero, as can the work W. Considering the control volume as shown in Fig. 7 for the vortex tube then Eq. (2) can be simplified as: iieem hm h=? (3) The expanding air can be treated as ideal gas and hence with no Joule-Thomson heating or cooling effect. Also, assuming air obeys the ideal gas laws and having constant specific heat capacity Cp, you can write: ipihC T= (4) ipicpchphm C Tm C Tm C T=+? (5) Am. J. Applied Sci., 6 (2): 251-262, 2009 255 by defining cf as the cold fraction: ccfimm=? (6) from the continuityEq: chimmm+=? (7) Combining Eq. 5, 6 and 7 gives the relationship between inlet stream temperature and cold stream temperature, (hot stream temperature and cold fraction). Hence Eq: ()icfchTT1T= + (8) by assuming, hcTTT= (9) cicTTT= (10) hhiTTT= (11) where, ?T is the difference between the hot and the cold air stream temperatures, ?Tc is the temperature difference between the inlet and cold air streams and finally ?Th is the temperature difference between the inlet and hot air streams. The equation can be written as: hcTTT= (12) Combining E q. 8 and 12 allows you to determine ?Tc and ?Th theoretically by measuring the cold fraction, cf and total temperature difference, ?T. Therefore: ()ccfT1T= (13) hcfTT= (14) Equation 13 and 14 can be used to show the consistency of the first law of thermodynamics for test carried out on the vortex tube. VORTEX TUBE EFFICIENCY In practical cases of refrigeration it is so important to determine the coefficient of performance of the cooling device. Hence, it seems only logical to determine the coefficient of performance of the vortex tube and compare it with the conventional refrigeration coefficient of performance to determine its efficiency in use. The vortex tube can be used as a refrigeration device when the cold pipe wall is used to reduce the temperature or as a heating device when the hot pipe wall is used to increase the temperature of an enclosure. It should be noted that opposite to what is normally viewed in thermodynamics, the vortex tube in this case is an open control volume device. If the system was assumed to be steady state, then from the first law of thermodynamics: HQ=? (15) where, H? is the system enthalpy change and Q? is the heat exchanged between the system and its surroundings. Lets assume that Q? is approximately zero even though the cold tube may have frost on it and the hot tube is very warm. If this is the case then: cHHHH0= + = (16) where, ?Hc is the enthalpy change of cold stream and ?HH is the enthalpy change of hot stream. Assuming the air as an ideal gas, the total enthalpy change can be written as: ()()cpcihphiHm C(TTm CTT0=+= (17) where, mc is mass flow rate at cold tube, mh is mass flow rate at hot tube, Tc is cold air temperature, Ti is inlet air temperature, Th is hot air temperature and Cp is specific heat of air at constant pressure and assumes the process as reversible and adiabatic. By applying the second law of thermodynamics to the above: 1Sdq0T =? (18) where, ?S is total entropy change, q is heat transfer and T is absolute temperature. The actual entropy change of the control volume at steady state is: chSSS = + (19) where, ?Sc and ?Sh are the entropy change from entrance to exit of the portion of entering air which leaves the cold tube and the portion of entering are Am. J. Applied Sci., 6 (2): 251-262, 2009 256 which leaves the hot tube, respectively. For an ideal gas (air) with constant specific heat, the entropy change can be written as: ccihhippiiciihmTPmTPSC lnRlnC lnRlnmTPmTP? =+?(20) where the subscripts i, c and h are respectively inlet stream, cold stream and hot stream and R is the ideal gas (air) constant. Since the appearance of a cold (or hot) effect upon the pipe wall without moving parts would attempt to consider this device as competition for a refrigerator (or heat pump), it is useful to estimate its coefficient of performance (COP). Focusing on the cooling effect that can be achieved by placing the cold pipe within an enclosure, the coefficient of performance can be calculated by: cHCOPW=? (21) Where cH? is obtained from: ()ccicHmTT=? (22) cH? is equal to the heat that is transferred to the cold stream through the cold pipe wall (like a heat exchanger) from some source (like the cold box in a refrigerator) and W? in the present case is the work done to compress the air from atmospheric pressure and temperature to the inlet conditions of the tube. Assuming reversible compression (isentropic, minimum work), W?is then obtained from: ()21mR TT nWn1=? (23) where, T2 is the compressor exit temperature and T1 is the compressor inlet temperature (reversible, polytropic process; air: n = 1.4). If we consider a complete system, P1 and T1 are the atmospheric pressure and temperature, P2 and T2 are the compressor exit conditions, 2211n1PTnPT= (24) After the air is compressed, it is kept in the high-pressure tank where then it cools down to the atmosphere temperature, T1 so the inlet temperature of the sonic nozzle Ti, is equal to T1 noting that: pRnCn1= (25) Equation (23) can be simplified to: ()ip21Wm CTT=?(26) with T2 calculated from Eq. (24). This is an ideal work value so it