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中文譯文 螺桿壓縮機(jī) 螺桿壓縮機(jī)的幾何形狀對(duì)稱分布有一個(gè)巨大的吹孔面積不包括它任何壓縮機(jī)應(yīng)用在高或中等壓力比參與。然而，對(duì)稱分布的表現(xiàn)出奇的好在低高壓壓縮機(jī)中的應(yīng)用。對(duì)圓形的輪廓，更多的細(xì)節(jié)可以發(fā)現(xiàn)馬德克，1978。 2.4.8 SRM的“A”型 SRM”“曲線如圖2.11所示。它保留了所有的有利的特征的對(duì)稱外形像它的簡單性的同時(shí)避免其主要的缺點(diǎn)，即，大吹孔面積。減少的主要目標(biāo)氣孔面積允許主門的尖點(diǎn)了轉(zhuǎn)子產(chǎn)生他們的同行，在柵極和主轉(zhuǎn)子擺線分別同行，剖面主要由界的門轉(zhuǎn)子和一條線穿過門轉(zhuǎn)子軸。 主曲線的設(shè)置包括:D2C2,這是一個(gè)圓形的門轉(zhuǎn)子與中心門口節(jié)圓,C2B2,這是一個(gè)圓在大門口轉(zhuǎn)子,該中心位于外的節(jié)圓區(qū)域。這是一個(gè)新的功能實(shí)施的一些問題在一代的主旋翼同行,因?yàn)閿?shù)學(xué)用于配置生成。當(dāng)時(shí)通用傳動(dòng)裝置不足。這偏心保證壓力角的轉(zhuǎn)子球不同于零,導(dǎo)致它的易于制造。 段是一個(gè)圓形的英航轉(zhuǎn)子以其中心門在節(jié)圓。 扁平的葉邊的主要和門出現(xiàn)生成EPI /圓內(nèi)旋輪線，分別由G和H的門主轉(zhuǎn)子組成。 是一個(gè)徑向線GF2門口的轉(zhuǎn)子。 這帶來了同樣的制造業(yè)的好處前面提到的圓偏心在最受歡迎的轉(zhuǎn)子型線的評(píng)論2.4。 圖2.11 “A”型發(fā)動(dòng)機(jī) 31對(duì)面的葉側(cè)。F2E2是一個(gè)圓的中心在大門口音高和最后,E2D2是一個(gè)圓的中心在門軸。 有關(guān)“A”簡介的更多詳細(xì)信息由 Amosov et al. 所出版的， 1977 年和作者： Rinder， 1979。 “一個(gè)”配置文件是一個(gè)很好的例子,一個(gè)好的和簡單的想法如何進(jìn)成一個(gè)復(fù)雜的結(jié)果。 因此,“一個(gè)”剖面是不斷遭受 這導(dǎo)致變化的“C”剖面。這主要是生成改善剖面可制造性。 最后,一個(gè)完全新的配置文件“D”剖面生成了一個(gè)新的發(fā)展介紹在剖面?zhèn)鲃?dòng)裝置 和增加門轉(zhuǎn)子扭矩。盡管復(fù)雜，其最終形式的復(fù)雜性的“一個(gè)”剖面出現(xiàn)的最受歡迎的螺桿壓縮機(jī)剖面,特別是在其專利過期。 2.4.9 SRM的“D”簡介 SRM的“D”文件，如圖2.12所示，是專門由界產(chǎn)生隨著離轉(zhuǎn)子節(jié)圓的中心。類似的演示類偏心圓的半徑為R3的內(nèi)圈。B1C1為偏心圓的半徑為R1，其中，連同a1j1小圓弧的半徑R2，位于主轉(zhuǎn)子。g2h2在柵極轉(zhuǎn)子和E2F2小圓弧柵上的圓弧轉(zhuǎn)子。f2g2是產(chǎn)生的門轉(zhuǎn)子相對(duì)大的圓弧在主旋翼的可能的最小曲率對(duì)應(yīng)的曲線。兩個(gè)圓弧，b2c2和f2g2確保在大曲率半徑節(jié)圓的面積。這避免了高應(yīng)力在轉(zhuǎn)子接觸區(qū)。 圖2.12 開關(guān)磁阻電機(jī)的“D”簡介 32 2螺桿壓縮機(jī)的幾何形狀 2.4.10 SRM的“G”簡介?！癎”配置文件介紹了SRM在上世紀(jì)十九年代作為一個(gè)對(duì)于“D”更換轉(zhuǎn)子，如圖2.13所示。相比“D”，“G”轉(zhuǎn)子，轉(zhuǎn)子具有兩個(gè)額外的界的獨(dú)特的特征在主轉(zhuǎn)子葉頂區(qū)域，靠近分度圓。此功能提高了轉(zhuǎn)子的接觸和，此外，產(chǎn)生較短的密封線。這在圖2.13中可以看到，其中一個(gè)轉(zhuǎn)子的“G”簡介通過分段h1i1僅在其扁平面特性。 圖2.13 開關(guān)磁阻電機(jī)的“G”簡介 2.4.11市“N”產(chǎn)生的轉(zhuǎn)子型線架 “N”轉(zhuǎn)子由一架生成程序計(jì)算。這個(gè)區(qū)別來自另外的他們。在這種情況下，大吹孔面積，這是一個(gè)特征架產(chǎn)生的轉(zhuǎn)子，所產(chǎn)生的高壓力克服通過轉(zhuǎn)子共軛程序是一側(cè)的機(jī)架。這削弱了單一的適當(dāng)?shù)那€的架子上。那么這樣一架用于分析兩個(gè)主要的門轉(zhuǎn)子。該方法及其擴(kuò)展應(yīng)用由作者創(chuàng)造了許多不同的轉(zhuǎn)子型線，他們中的一些應(yīng)用通過斯托西奇等人，1986，和Hanjalic斯托西奇，1994。一個(gè)應(yīng)用程序齒條的生成過程的描述斯托西奇，1996。 以下內(nèi)容是被生成的一個(gè)架子的簡潔的描述“N”使腐壞者簡介，典型使腐壞者的一個(gè)家庭中為空氣的有效壓縮設(shè)計(jì)描，共同 refrigerants 和一些過程氣體。使腐壞者被生成按聯(lián)合架子-rotor 的一代程序其特征是，以便為表現(xiàn)盡可能優(yōu)化任何細(xì)節(jié)可能欣然地進(jìn)一步被修改申請(qǐng)。 33架子上所有主要的弧坐標(biāo)在此相對(duì)在機(jī)架上的坐標(biāo)系統(tǒng)。機(jī)架的葉分為幾個(gè)弧。輪廓圓弧之間的分歧被表示為大寫字母和每個(gè)弧分別定義，如圖所示。2.14和2.15在那里架和轉(zhuǎn)子所示。 圖2.14 生成的“N”型架 圖2.15 “N”轉(zhuǎn)子的主曲線給出架 34 2螺桿壓縮機(jī)的幾何形狀 所有的曲線給出了一個(gè)“弧”表述為：axp + byq = 1。因此，直線，圓，一組拋物線，橢圓和雙曲線都容易描述通過選擇一個(gè)適當(dāng)?shù)闹档膮?shù)，B，P和Q。段的機(jī)架上的直線，EF是圓弧半徑R，段FG是上漸開線直線，P = Q = 1，同時(shí)段生長激素對(duì)齒條嚙合曲線生成的圓弧g2h2上內(nèi)圈。段HJ齒條嚙合曲線所產(chǎn)生的在主轉(zhuǎn)子半徑的圓弧h1j1。段JA是一個(gè)循環(huán)圓弧半徑R上的齒條，AB是一個(gè)圓弧，可以是圓形或雙曲線或拋物線，橢圓，段BC在齒條直線匹配的轉(zhuǎn)子輪葉和CD的漸開線的圓弧架，半徑為R3?！癗”簡介的更多詳細(xì)信息可以被找到在 Stosic， 1994 年。 2.4.12特色的“N”型 示例的“N”在2-3，3-5，4-5，4-6，5-6形，5-7和6-7配置在圖中給出。2.16圖2.23。應(yīng)該指出的是自動(dòng)獲得從一個(gè)計(jì)算機(jī)代碼被所有的轉(zhuǎn)子考慮簡單地指定在主門轉(zhuǎn)子葉數(shù)，和 在一般型的葉曲線。各種改性分布是可能的?！癗”型設(shè)計(jì)是一種妥協(xié)之間的完全密封，小吹孔面積，大位移，短。 圖2.16 “N”在2-3配置的轉(zhuǎn)子 圖2.17 “N”在3-5配置的轉(zhuǎn)子 圖2.18 “N”在4-5配置的轉(zhuǎn)子 圖2.19 “N”在4-6配置的轉(zhuǎn)子 圖2.20 “N”轉(zhuǎn)子相對(duì)于“西格瑪”，“D”和“開關(guān)磁阻電機(jī)轉(zhuǎn)子旋風(fēng)” 圖2.21 “N”在5-6配置的轉(zhuǎn)子 圖2.22 “N”在5-7配置的轉(zhuǎn)子 圖2.23 “N”在6 / 7配置的轉(zhuǎn)子 密封線,小關(guān)卷,漸開線轉(zhuǎn)子接觸和適當(dāng)?shù)拈T轉(zhuǎn)子扭矩分配連同高轉(zhuǎn)子機(jī)械剛度。葉的數(shù)量需要隨指定的壓縮機(jī)責(zé)任。 3/5安排最適合干空氣壓縮,4/5和5/6的石油淹沒了壓縮機(jī)和溫和的壓力差和6/7為高壓和大內(nèi)置體積比制冷應(yīng)用程序。 雖然一個(gè)轉(zhuǎn)子型線的全面的評(píng)估需要不止一個(gè)幾何評(píng)估，一些對(duì)“N”型可能是關(guān)鍵的功能 通過與三個(gè)最流行的螺釘比較容易理解轉(zhuǎn)子型線已經(jīng)描述在這里，（一）“西格瑪”輪廓的bammert，1979，（b）SRM的“D”輪廓的astberg 1982，和（c）“旋風(fēng)”簡介通過Hough變換和莫里斯，1984。所有這些轉(zhuǎn)子如圖2.20所示的地方可以看出，“N”的公司有一個(gè)更大的吞吐量和更嚴(yán)厲的門轉(zhuǎn)子在所有情況下，當(dāng)如吹孔面積等特點(diǎn)，有限體積和高壓密封線的長度是相同。同時(shí)，低壓密封線較短，但這不重要因?yàn)橄鄳?yīng)的間隙可以保持很小。吹孔面積可由尖端半徑的調(diào)整控制無論是主要和門的門轉(zhuǎn)子外徑小于或等于中徑。同時(shí)密封線可以保持很通過構(gòu)建大部分從圓的中心轉(zhuǎn)子型線短靠近分度圓。但是，在吹孔面積的減少將增加在平坦的轉(zhuǎn)子側(cè)的密封線長度。之間的一種折衷這些趨勢，因此需要獲得最好的結(jié)果。轉(zhuǎn)子失穩(wěn)往往是由在門轉(zhuǎn)子扭矩分布引起的在一個(gè)完整的周期變化的方向。配置文件生成程序本文介紹了能夠控制大門上的扭矩轉(zhuǎn)子，從而避免這樣的影響。此外，全齒之間的接觸“N”轉(zhuǎn)子使任何額外的接觸載荷更容易被吸收比任何其他類型的轉(zhuǎn)子。兩個(gè)轉(zhuǎn)子對(duì)圖2.24所示第一個(gè)具有所謂的“負(fù)”的門轉(zhuǎn)子扭矩的同時(shí)第二顯示更常見的“積極”的扭矩。 圖2.24 “N”負(fù)轉(zhuǎn)矩，左、右正扭矩， 2.4.13鼓風(fēng)機(jī)轉(zhuǎn)子型線 風(fēng)機(jī)配置文件，如圖2.25所示是對(duì)稱的。因此，只有一個(gè)季度需要指定以定義整個(gè)轉(zhuǎn)子。它由兩段，在轉(zhuǎn)子葉尖端和直的一個(gè)很小的圈子線。圓線的幻燈片和生成，而直線生成漸開線。 圖2.25 風(fēng)機(jī)簡介 編號(hào) 無錫太湖學(xué)院 畢業(yè)設(shè)計(jì)（論文） 相關(guān)資料 題目： 軸承檢測裝置的設(shè)計(jì) 信機(jī) 系 機(jī)械工程及自動(dòng)化專業(yè) 學(xué) 號(hào)： 　　　 0923802　　　　 學(xué)生姓名： 樊阿紅 指導(dǎo)教師： 　 何雪明 （職稱：副教授 ） （職稱： ） 2013年5月25日 目 錄 一、畢業(yè)設(shè)計(jì)（論文）開題報(bào)告 二、畢業(yè)設(shè)計(jì)（論文）外文資料翻譯及原文 三、學(xué)生“畢業(yè)論文（論文）計(jì)劃、進(jìn)度、檢查及落實(shí)表” 四、實(shí)習(xí)鑒定表 無錫太湖學(xué)院 畢業(yè)設(shè)計(jì)（論文） 開題報(bào)告 題目： 軸承檢測裝置的設(shè)計(jì) 信機(jī) 系 機(jī)械工程及自動(dòng)化 專業(yè) 學(xué) 號(hào)： 0923802 學(xué)生姓名： 樊阿紅 指導(dǎo)教師： 何雪明 （職稱：副教授 ） （職稱： ） 2012年11月25日 課題來源 無錫某軸承設(shè)備廠大批量生產(chǎn)檢測需求 科學(xué)依據(jù)（包括課題的科學(xué)意義；國內(nèi)外研究概況、水平和發(fā)展趨勢；應(yīng)用前景等） （1）課題科學(xué)意義 該課題主要是為了培養(yǎng)開發(fā)和創(chuàng)新機(jī)械設(shè)備的設(shè)計(jì)能力，要求能夠結(jié)合所學(xué)知識(shí)對(duì)被加工零件進(jìn)行UG三維建模和二維出圖，根據(jù)實(shí)際生產(chǎn)需要中所產(chǎn)生的實(shí)際性問題。綜合所學(xué)的機(jī)械理論設(shè)計(jì)與方法、自動(dòng)化控制等知識(shí)，完成盡可能多的軸承的檢測項(xiàng)目需求，實(shí)現(xiàn)自動(dòng)化檢測。 再設(shè)計(jì)三維建模的過程中，在滿足生產(chǎn)檢測的需求下，應(yīng)盡可能多的采用標(biāo)準(zhǔn)件，提高其互換性要求，實(shí)現(xiàn)大批量自動(dòng)檢測，同時(shí)降低產(chǎn)品的生產(chǎn)成本。 （2）國內(nèi)外的發(fā)展?fàn)顩r及其發(fā)展前景 軸承是各類機(jī)械裝備中最為重要的基礎(chǔ)部件，它的精度、性能、壽命以及可靠性對(duì)主機(jī)的精度、性能、壽命以及可靠性起著極為重要的作用。隨著軸承檢測儀器的發(fā)展，對(duì)軸承檢測項(xiàng)目的要求及檢測項(xiàng)目的精確度要求也越來越多、越來越高，此外還要在一定程度上滿足人機(jī)協(xié)作要求。 在國內(nèi)，常用的檢測軸承質(zhì)量的振動(dòng)檢測儀器有兩種：一種是測量軸承振動(dòng)的加速型軸承振動(dòng)檢測儀，另一種是通過測量軸承振動(dòng)速度的速度型軸承振動(dòng)檢測儀。杭州軸承試驗(yàn)研究中心的BVT-5軸承振動(dòng)速度檢測儀是其性能最完善的一個(gè)型號(hào)。 在國外，丹麥研制出了B&K2112型儀器，其性能與國產(chǎn)的S0910型軸承振動(dòng)給檢測儀類似。在國外軸承振動(dòng)一般采用測量多個(gè)參數(shù)進(jìn)行判斷。如美國BENDIX公司研制的B1010就是國際上此類設(shè)備中具有代表性的產(chǎn)品之一。國內(nèi)軸承行業(yè)的測試與試驗(yàn)技術(shù)在多方面逐步與世界接軌，并不斷開發(fā)出一系列適合國情和國家標(biāo)準(zhǔn)的測試儀器與實(shí)驗(yàn)裝備。 研究內(nèi)容 ① 熟悉軸承檢測裝置的發(fā)展歷程，特別是近十幾年來國內(nèi)外的發(fā)展?fàn)顩r，及應(yīng)用的主要原理依據(jù)等； ② 較好的結(jié)合機(jī)械理論知識(shí)、自動(dòng)化控制的硬、軟件知識(shí)； ③ 達(dá)到技術(shù)指標(biāo)所要求，滿足實(shí)際工作需要，安全、可靠、工作穩(wěn)定、測量精度準(zhǔn)確的要求； ④ 熟練掌握并靈活運(yùn)用UG軟件完成三維繪圖工作； ⑤ 完成軸承檢測裝置的裝配圖設(shè)計(jì)（三維及工程圖紙）； 擬采取的研究方法、技術(shù)路線、實(shí)驗(yàn)方案及可行性分析 （1）實(shí)驗(yàn)方案 結(jié)合機(jī)械制造設(shè)備、機(jī)械設(shè)計(jì)、自動(dòng)化控制的理論知識(shí)針對(duì)相關(guān)檢測項(xiàng)目擬定方繪制草圖模型。 （2）研究方法 ① 借閱相關(guān)書籍雜志，利用圖書館及網(wǎng)絡(luò)資源查閱資料。 ② 三維建模、擬定方案進(jìn)行可行性分析設(shè)計(jì)。 研究計(jì)劃及預(yù)期成果 研究計(jì)劃： 2012年11月12日-2012年12月25日：按照任務(wù)書要求查閱論文相關(guān)參考資料，填寫畢業(yè)設(shè)計(jì)開題報(bào)告書。 2013年1月9日-2013年2月12日：填寫畢業(yè)實(shí)習(xí)報(bào)告。 2013年2月13日-2013年2月17日：按照要求修改畢業(yè)設(shè)計(jì)開題報(bào)告。 2013年2月18日-2013年3月21日：學(xué)習(xí)并翻譯一篇與畢業(yè)設(shè)計(jì)相關(guān)的英文材料。 2013年3月22日-2013年4月11日：軸承檢測裝置的研究項(xiàng)目分析，初步三維建模。 2013年4月12日-2013年4月25日：UG設(shè)計(jì)。 2013年4月26日-2013年5月25日：畢業(yè)論文撰寫和修改工作。 預(yù)期成果： 通過模擬、建模、實(shí)驗(yàn)等可行性方法，達(dá)到產(chǎn)品的最優(yōu)化設(shè)計(jì)，大大降低勞動(dòng)強(qiáng)度，提高生產(chǎn)效率，基本實(shí)現(xiàn)自動(dòng)化檢測。 特色或創(chuàng)新之處 ① 運(yùn)用UG軟件完成三維建模，并制作成二維圖紙 ② 較好的結(jié)合機(jī)械理論知識(shí)、自動(dòng)控制軟件等 已具備的條件和尚需解決的問題 ① 設(shè)計(jì)方案思路已經(jīng)非常明確，已經(jīng)具備使用UG建模的能力和檢測方面的知識(shí)。完成相關(guān)檢測項(xiàng)目的設(shè)計(jì) ② 設(shè)計(jì)多個(gè)方案，從中總結(jié)優(yōu)劣進(jìn)行相關(guān)設(shè)計(jì)與分析 指導(dǎo)教師意見 指導(dǎo)教師簽名： 年 月 日 教研室（學(xué)科組、研究所）意見 教研室主任簽名： 年 月 日 系意見 主管領(lǐng)導(dǎo)簽名： 年 月 日 英文原文 Screw Compressor The Symmetric profile has a huge blow-hole area which excludes it from any compressor applicat -ion where a high or even moderate pressure ratio is involved. However, the symmetric profile per -forms surprisingly well in low pressure compressor applications.More details about the circular p -rofile can be found in Margolis, 1978. 2.4.8 SRM “A” Profile The SRM “A” profile is shown in Fig. 2.11. It retains all the favourable features of the symmetric profile like its simplicity while avoiding its main disadvantage,namely, the large blow-hole area. The main goal of reducing the blow hole area was achieved by allowing the tip points of the main and gate rotors to generate their counterparts, trochoids on the gate and main rotor respectively. T -he “A” profile consists mainly of circles on the gate rotor and one line which passes through the gate rotor axis.The set of primary curves consists of: D2C2, which is a circle on the gate rotor with the centre on the gate pitch circle, and C2B2, which is a circle on the gate rotor, the centre of whi ch lies outside the pitch circle region.This was a new feature which imposed some problems in the generation of its main rotor counterpart, because the mathematics used for profile generation at tha -t time was insufficient for general gearing. This eccentricity ensured that the pressure angles on th -e rotor pitches differ from zero, resulting in its ease of manufacture. Segment BA is a circle on th -e gate rotor with its centre on the pitch circle. The flat lobe sides on the main and gate rotors were generated as epi/hypocycloids by points G on the gate and H on the main rotor respectively. GF2 is a radial line at the gate rotor. This brought the same benefits to manufacturing as the previously mentioned circle eccentricity on Fig. 2.11 SRM “A” Profile 2.4 Review of Most Popular Rotor Profiles 31 the opposite lobe side. F2E2 is a circle with the cent -re on the gate pitch and finally, E2D2 is a circle with the centre on the gate axis.More details on t -he “A” profile are published by Amosov et al., 1977 and by Rinder, 1979.The “A” profile is a go od example of how a good and simple idea evolved into a complicated result. Thus the “A” pro file was continuously subjected to changes which resulted in the “C” profile. This was mainly gen erated to improve the profile manufacturability. Finally, a completely new profile, the“D” profile was generated to introduce a new development in profile gearing and to increase the gate rotor tor -que.Despite the complexity of its final form the “A” profile emerged to be the most popular scre -w compressor profile, especially after its patent expired. 2.4.9 SRM “D” Profile The SRM “D” profile, shown in Fig. 2.12, is generated exclusively by circles with the centres off the rotor pitch circles. Similar to the Demonstrator, C2D2 is an eccentric circle of radius r3 onthe gate rotor. B1C1 is an eccentric circle of radius r1, which, together withthe small circular arc A1J1 of radius r2, is positioned on the main rotor. G2H2is a small circular arc on the gate rotor and E2F2 is a circular arc on the gaterotor. F2G2 is a relatively large circular arc on the gate rotor which produces a corresponding curve of the smallest possible curvature on the main rotor.Both circular arc, B2C2 and F2G2 ensure a large radius of curvature in the pitch circle area. This avoids high stresses in the rotor contact region. Fig. 2.12 SRM “D” Profile The “G” profile was introduced by SRM in the late nineteen nineties as a replacement for the “D” rotor and is shown in Fig. 2.13. Compared with the“D” rotor, the “G” rotor has the unique feature of two additional circles in the addendum area on both lobes of the main rotor, close to the pitch circle.This feature improves the rotor contact and, additionally, generates shorter sealing lines. This can be seen in Fig. 2.13, where a rotor featuring “G” profile characteristics only on its flat side through segment H1I1 is presented. Fig. 2.13 SRM “G” Profile 2.4.11 City “N” Rack Generated Rotor Profile “N” rotors are calculated by a rack generation procedure. This distinguishes them from any others. In this case, the large blow-hole area, which is a characteristic of rack generated rotors, is overcome by generating the high pressure side of the rack by means of a rotor conjugate procedure. This undercuts the single appropriate curve on the rack. Such a rack is then used for profiling both the main and the gate rotors. The method and its extensions were used by the authors to create a number of different rotor profiles, some of them used by Stosic et al., 1986, and Hanjalic and Stosic, 1994. One of the applications of the rack generation procedure is described in Stosic, 1996.The following is a brief description of a rack generated “N” rotor profile,typical of a family of rotor profiles designed for the efficient compression of air,common refrigerants and a number of process gases. The rotors are generated by the combined rack-rotor generation procedure whose features are such that it may be readily modified further to optimize performance for any specific application. 2.4 Review of Most Popular Rotor Profiles 33 The coordinates of all primary arcs on the rack are summarized here relative to the rack coordinate system. The lobe of the rack is divided into several arcs. The divisions between the profile arcs are denoted by capital letters and each arc is defined separately, as shown in the Figs. 2.14 and 2.15 where the rack and the rotors are shown. Fig. 2.14 Rack generated “N” Profile Fig. 2.15 “N” rotor primary curves given on rack 34 2 Screw Compressor Geometry All curves are given as a “general arc” expressed as: axp + byq = 1. Thus straight lines, circles, parabolae, ellipses and hyperbolae are all easily described by selecting appropriate values for parameters a, b, p and q.Segment DE is a straight line on the rack, EF is a circular arc of radius r4, segment FG is a straight line for the upper involute, p = q = 1, while segment GH on the rack is a meshing curve generated by the circular arc G2H2 on the gate rotor. Segment HJ on the rack is a meshing curve generated by the circular arc H1J1 of radius r2 on the main rotor. Segment JA is a circular arc of radius r on the rack, AB is an arc which can be either a circle or a parabola, a hyperbola or an ellipse, segment BC is a straight line on the rack matching the involute on the rotor round lobe and CD is a circular arc on the rack, radius r3.More details of the “N” profile can be found in Stosic, 1994. 2.4.12 Characteristics of “N” Profile Sample illustrations of the “N” profile in 2-3, 3-5, 4-5, 4-6, 5-6, 5-7 and 6-7 configurations are given in Figs. 2.16 to Fig. 2.23. It should be noted that all rotors considered were obtained automatically from a computer code by simply specifying the number of lobes in the main and gate rotors, and the lobe curves in the general form.A variety of modified profiles is possible. The “N” profile design is a compromise between full tightness, small blow-hole area, large displacement. Fig. 2.16 “N” Rotors in 2-3 configuration Fig. 2.17 “N” Rotors in 3-5 configuration Fig. 2.18 “N” Rotors in 4-5 configuration Fig. 2.19 “N” Rotors in 4-6 configuration Fig. 2.20 “N” Rotors compared with “Sigma”, SRM “D” and “Cyclon” rotors Fig. 2.21 “N” Rotors in 5-6 configuration Fig. 2.22 “N” Rotors in 5-7 configuration Fig. 2.23 “N” rotors in 6/7 configuration sealing lines, small confined volumes, involute rotor contact and proper gate rotor torque distribution together with high rotor mechanical rigidity.The number of lobes required varies according to the designated compressor duty. The 3/5 arrangement is most suited for dry air compression, the 4/5 and 5/6 for oil flooded compressors with a moderate pressure difference and the 6/7 for high pressure and large built-in volume ratio refrigeration applications.Although the full evaluation of a rotor profile requires more than just a geometric assessment, some of the key features of the “N” profile may be readily appreciated by comparing it with three of the most popular screw rotor profiles already described here, (a) The “Sigma” profile by Bammert,1979, (b) the SRM “D” profile by Astberg 1982, and (c) the “Cyclon” profile by Hough and Morris, 1984. All these rotors are shown in Fig. 2.20 where it can be seen that the “N” profiles have a greater throughput and a stiffer gate rotor for all cases when other characteristics such as the blow-hole area, confined volume and high pressure sealing line lengths are identical.Also, the low pressure sealing lines are shorter, but this is less important because the corresponding clearance can be kept small.The blow-hole area may be controlled by adjustment of the tip radii on both the main and gate rotors and also by making the gate outer diameter equal to or less than the pitch diameter. Also the sealing lines can be kept very short by constructing most of the rotor profile from circles whose centres are close to the pitch circle. But, any decrease in the blow-hole area will increase the length of the sealing line on the flat rotor side. A compromise betweenthese trends is therefore required to obtain the best result. 2.4 Review of Most Popular Rotor Profiles 39 Rotor instability is often caused by the torque distribution in the gate rotor changing direction during a complete cycle. The profile generation procedure described in this paper makes it possible to control the torque on the gate rotor and thus avoid such effects. Furthermore, full involute contact between the “N” rotors enables any additional contact load to be absorbed more easily than with any other type of rotor. Two rotor pairs are shown in Fig. 2.24 the first exhibits what is described as “negative” gate rotor torque while the second shows the more usual “positive” torque. Fig. 2.24 “N” with negative torque, left and positive torque, right 2.4.13 Blower Rotor Profile The blower profile, shown in Fig. 2.25 is symmetrical. Therefore only one quarter of it needs to be specified in order to define the whole rotor. It consists of two segments, a very small circle on the rotor lobe tip and a straight line. The circle slides and generates cycloids, while the straight line generates involutes. Fig. 2.25 Blower profile