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湖南科技大學(xué)機(jī)電工程學(xué)院 2015屆畢業(yè)設(shè)計(jì)（論文）開題報(bào)告
題 目
5MW海上風(fēng)電機(jī)組齒輪傳動系統(tǒng)設(shè)計(jì)
作者姓名
賴文馨
學(xué)號
1103010401
所學(xué)專業(yè)
機(jī)械設(shè)計(jì)制造及其自動化
1、 研究的意義：
當(dāng)今社會隨著經(jīng)濟(jì)日益發(fā)展，人們對能源的需求越來越大，而石油等不可再生能源也面臨枯竭，人們急需尋找替代能源。自然界中具有非常大的風(fēng)能儲存量，由于太陽的輻射作用，地球每年大約可獲得的 地球每年大約可獲得 KW·h 的風(fēng)能。其中，邊界層占整個(gè)大氣層的 35%，因而邊界層大氣中可利用的風(fēng)能功率約為 KW，如果人類在近地面層能利用其中的十分之一，則全球可開發(fā)風(fēng)能的功率為KW。這個(gè)值相當(dāng)于 2005 年全球發(fā)電能力的 74.7 倍[1]。通過上述數(shù)據(jù)可知，風(fēng)能是地球上最重要的能源之一，合理的開發(fā)利用風(fēng)能可以解決越來越嚴(yán)重的能源短缺問題。風(fēng)能作為一種清潔的、儲量極為豐富的可再生能源，在未來的能源市場很有開發(fā)潛力，各國政府相繼投入大量的人力及資金研究生產(chǎn)風(fēng)力發(fā)電機(jī)，力圖設(shè)計(jì)出安全可靠高效的風(fēng)力發(fā)電機(jī)。風(fēng)力發(fā)電機(jī)中很重要的一部分就是齒輪傳動增速箱，如何把齒輪傳動系統(tǒng)設(shè)計(jì)好便成了關(guān)鍵問題
2、國內(nèi)外現(xiàn)狀：
從20世紀(jì)70年代末以來，隨著世界各國對能源危機(jī)、環(huán)境保護(hù)等問題的日益關(guān)注，一致認(rèn)為大規(guī)模發(fā)展利用風(fēng)力發(fā)電是非常有效的措施之一。19 世紀(jì)末、丹麥最先開始探索風(fēng)力發(fā)電、研制出風(fēng)力發(fā)電機(jī)組直到20 世紀(jì)70 年代以前，只有小型充電用風(fēng)力機(jī)達(dá)到實(shí)用階段。1973 年石油危機(jī)后，美國、歐洲等發(fā)達(dá)國家為尋求替代能源，投入大量經(jīng)費(fèi)，研制現(xiàn)代風(fēng)力發(fā)電機(jī)組，開創(chuàng)了風(fēng)能利用的新時(shí)期。世界風(fēng)能委員會 11 日公布的一份報(bào)告指出，到 2010 年，全球風(fēng)能發(fā)電能力將比現(xiàn)在提高一倍，達(dá)到 149.5 吉瓦。根據(jù)世界風(fēng)能委員會的統(tǒng)計(jì)數(shù)據(jù)，僅在 2006年，全球風(fēng)力發(fā)電能力就比上年增長了 25％，達(dá)到了 74 吉瓦。
歐洲一直以來是風(fēng)力發(fā)電市場的領(lǐng)導(dǎo)者，目前在風(fēng)能發(fā)電領(lǐng)域仍處在世界前列，而且在今后幾年其在風(fēng)力發(fā)電實(shí)際運(yùn)用及其國際市場上還將繼續(xù)保持領(lǐng)先地位，但隨著近年來世界其他國家和地區(qū)對風(fēng)力發(fā)電的重視和發(fā)展，歐洲的領(lǐng)先優(yōu)勢會有所下降。據(jù)世界風(fēng)能委員會的統(tǒng)計(jì)，2004 年歐洲風(fēng)力發(fā)電裝機(jī)容量占全世界風(fēng)電總裝機(jī)容量的 72％，2005 年該比例就下降為 69％，而去年則又跌至 51％，到 2010 年，雖然整個(gè)歐洲的風(fēng)力發(fā)電量將比目前的 48 吉瓦增長近一倍達(dá)到 82 吉瓦，但其占全球市場的份額則將下滑到 44％。這份報(bào)告還對 2006 年到 2010 年期間全球各地區(qū)風(fēng)力發(fā)電態(tài)勢進(jìn)行了預(yù)測。報(bào)告說，由于美國連續(xù)采取生產(chǎn)稅抵免等多項(xiàng)風(fēng)能激勵(lì)措施，北美地區(qū)風(fēng)力發(fā)電的發(fā)展仍將保持快速增長勢頭。緊隨其后的是風(fēng)力發(fā)電的新興增長地區(qū)——亞洲，主要是中國和印度，亞洲將成為全球風(fēng)能發(fā)電年增長幅度最快的地區(qū)之一，年增長將達(dá) 28.3％，其風(fēng)力發(fā)電能力將從 2006 年的 10.7 吉兆增長到 2010 年的 29 吉兆。風(fēng)力發(fā)電機(jī)單機(jī)裝機(jī)容量也從最初的 50KW，發(fā)展到 3.6MW，目前新建風(fēng)場普遍采用 1.5MW 成熟機(jī)型，單機(jī)容量繼續(xù)穩(wěn)步上升已成為風(fēng)力發(fā)電機(jī)的發(fā)展趨勢[2]。
我國三北地區(qū)風(fēng)能功率密度在 200～300W/m2以上，有的可達(dá) 500W/m2以上，如阿拉山口、達(dá)坂城、輝騰錫勒、錫林浩特的灰騰梁等、可利用的小時(shí)數(shù)在 5000小時(shí)以上，有的可達(dá) 7000 小時(shí)以上。東南沿海地區(qū)年有效風(fēng)能功率密度在 200W/m2以上，將風(fēng)能功率密度線平行于海岸線，沿海島嶼風(fēng)能功率密度在 500 W/m2以上如臺山、平潭、東山、南鹿、大陳、嵊泗、南澳、馬祖、馬公、東沙等?？衫眯r(shí)數(shù)約在 7000-8000 小時(shí)。根據(jù)最新風(fēng)能資源評價(jià)，我國陸地可利用風(fēng)能資源 3 億千瓦，加上近岸海域可利用的風(fēng)能資源，共計(jì)約 10 億千瓦，風(fēng)能儲量非常豐富，開展風(fēng)力發(fā)電是既經(jīng)濟(jì)又高效的方式[3]。我國風(fēng)力發(fā)電技術(shù)的研究始于 20 世紀(jì) 70 年代末 80 年代初，通過自主研發(fā)小型風(fēng)力發(fā)電機(jī)解決廣大牧區(qū)牧民及一些島嶼上居民的生活生產(chǎn)用電。到 2006 年底，全國已建成約 90 個(gè)風(fēng)電場，已經(jīng)建成并網(wǎng)發(fā)電的風(fēng)場主要分布在、內(nèi)蒙、廣東、浙江、河北、遼寧等 16 個(gè)省區(qū)，裝機(jī)總?cè)萘窟_(dá)到約 260 萬千瓦。但與國際先進(jìn)水平相比，國產(chǎn)風(fēng)電機(jī)組單機(jī)容量較小，關(guān)鍵技術(shù)依賴進(jìn)口，零部件的質(zhì)量還有待提高。我國2009年新增風(fēng)電裝機(jī)容量13800兆瓦(0.138億千瓦),同比增長高達(dá)124%，新增市場容量超過美國居全球第一；累計(jì)裝機(jī)容量連續(xù)第四年翻番,超越德國和西班牙，規(guī)模排在美國的 35159 兆瓦之後，位居世界第二。中國可再生能源協(xié)會風(fēng)能專業(yè)委員會主任賀德馨在風(fēng)能大會上亦稱,中國今年底風(fēng)電裝機(jī)容量有望達(dá)到40000 兆瓦，去年底為 25800 兆瓦。到 2020 年時(shí)中國風(fēng)電裝機(jī)容量有望達(dá)到 3 億千瓦左右，大幅高于官方最新預(yù)期的 2.3 億千瓦。由此可見，未來我國的風(fēng)力發(fā)電發(fā)展前景非常良好，因此如何設(shè)計(jì)制造出安全高效的風(fēng)力發(fā)電機(jī)就成了很重要的研究課題。
1、 研究目標(biāo)、內(nèi)容和擬解決的關(guān)鍵問題（根據(jù)任務(wù)要求進(jìn)一步具體化）
研究目標(biāo)：
（1） 對齒輪箱選用合理的結(jié)構(gòu)、增速比和材料。設(shè)計(jì)質(zhì)量好、重量輕、空間體積小、運(yùn)行穩(wěn)定的大容量風(fēng)電機(jī)組齒輪傳動系統(tǒng)。
（2） 引用風(fēng)力機(jī)的風(fēng)輪葉片設(shè)計(jì)及塔架設(shè)計(jì)，從而完成整個(gè)風(fēng)力發(fā)電機(jī)的設(shè)計(jì)。
主要內(nèi)容：
本增速箱速箱的結(jié)構(gòu)為二級行星，一級斜齒輪，根據(jù)設(shè)計(jì)任務(wù)書的要求合理分配各級傳動比，計(jì)算各級的齒輪參數(shù)，軸承參數(shù)，并進(jìn)行校核。選出合理的軸承類型，并對增速箱尺寸進(jìn)行計(jì)算，以及將各個(gè)部分裝配起來。
進(jìn)程：
第一階段：開題階段 3月9日至3月20日，收集、查閱和整理設(shè)計(jì)資料，完成3000字的文獻(xiàn)翻譯，完成畢業(yè)實(shí)習(xí)報(bào)告和開題報(bào)告。
第二階段：設(shè)計(jì)階段 3月21日-3月28 日，齒輪傳動系統(tǒng)方案選擇、傳動比分配，傳動結(jié)構(gòu)造型等整體方案設(shè)計(jì)與計(jì)算。
第三階段：計(jì)算階段 3月29日至4月15日，齒輪、軸、軸承等關(guān)鍵傳動結(jié)構(gòu)件的設(shè)計(jì)計(jì)算，繪制零件圖。
第四階段：繪圖階段 4月16日至5月 5日，傳動系統(tǒng)裝配圖繪制。
第五階段：畢業(yè)答辯 5月6日至 5月25日，設(shè)計(jì)計(jì)算說明書的編制、整理、修改、定稿，準(zhǔn)備答辯
解決的關(guān)鍵問題
風(fēng)力發(fā)電機(jī)床系統(tǒng)主要是將能量由葉輪傳遞至發(fā)電機(jī)。傳動系統(tǒng)主要包括主軸、主軸承、齒輪箱、高速軸、聯(lián)軸器等部件。而本課題的主要部分是對風(fēng)電機(jī)傳動系統(tǒng)的設(shè)計(jì)，所以有可能遇到的主要問題：
（1）準(zhǔn)確對傳動方案的分析；
（2）確定齒輪箱的傳動比的分配；
（3）齒輪尺寸參數(shù)的確定
（4）對軸承的尺寸進(jìn)行確定；
（5）選擇合理的軸承類型；
（6）對箱體和總體結(jié)構(gòu)的確定；
（7）對箱體主要部件載荷的計(jì)算和校核；
（8）確定冷卻溫度和潤滑系統(tǒng)；
（9）對整個(gè)部件的裝配圖和零件圖的繪制；
這些問題都是設(shè)計(jì)該風(fēng)機(jī)傳動系統(tǒng)的關(guān)鍵問題，在設(shè)計(jì)過程中，將通過查閱有關(guān)文獻(xiàn)資料和向老師咨詢的方法來解決。
2、 特色與創(chuàng)新之處：
我國的風(fēng)力事業(yè)由于起步晚，特比是兆瓦級風(fēng)電機(jī)齒輪箱，主要生產(chǎn)設(shè)備長期依賴進(jìn)口。在自主開發(fā)風(fēng)力大型容量發(fā)電機(jī)等方面還比較落后，特別是像齒輪傳動系統(tǒng)等技術(shù)領(lǐng)域還存在很大的差異。為此希望減少此差距。
按照現(xiàn)在風(fēng)機(jī)裝機(jī)要求，在考慮重量、體積、運(yùn)行穩(wěn)定性的多種情況下，設(shè)計(jì)合理的齒輪箱和增速比，采用合理的材料提高運(yùn)行的壽命。同時(shí)在設(shè)計(jì)繪制零件圖和裝配圖時(shí)廣泛運(yùn)用CAD/CAM/CAE技術(shù)和Pro/e軟件，以提要傳動系統(tǒng)運(yùn)行的精度、可靠性、降低傳動系統(tǒng)制造成本，提高傳動系統(tǒng)標(biāo)準(zhǔn)化水平和傳動系統(tǒng)標(biāo)準(zhǔn)件的使用率。
在本次畢業(yè)設(shè)計(jì)，本人將全部應(yīng)用CAD/CAE/CAM技術(shù)和soliworks軟件來設(shè)計(jì)傳動系統(tǒng)。利用CAD軟件繪制二維裝配圖和零件圖，利用soliworks軟件繪制三維裝配圖和零件圖；大大縮短了設(shè)計(jì)時(shí)間以及畫圖時(shí)間，并提高了設(shè)計(jì)精度還有減小誤差。
3、 擬采取的研究方法、步驟、技術(shù)路線
(1)查閱資料，熟悉國內(nèi)外風(fēng)電機(jī)及其傳動系統(tǒng)齒輪箱的現(xiàn)狀和發(fā)展趨勢。
(2)理解風(fēng)電傳動系統(tǒng)齒輪箱工作原理及結(jié)構(gòu)分析，確定齒輪箱總裝設(shè)計(jì)思路。
(3)建立準(zhǔn)確的分析模型，準(zhǔn)確求解受載輪齒的載荷分布。?
(4)完成主要零部件設(shè)計(jì)并進(jìn)行強(qiáng)度校核。
(5)繪制零件加工圖，選定加工工藝。?
(6)編寫設(shè)計(jì)說明書。
4、 擬使用的主要設(shè)計(jì)、分析軟件及儀器設(shè)備
主要設(shè)計(jì)、分析軟件：
CAD軟件（繪制二維裝配圖和零件圖）
soliworks軟件（繪制三維裝配圖和零件圖）
儀器設(shè)備：
本課題主要是對大容量風(fēng)電機(jī)組齒輪傳動系統(tǒng)進(jìn)行三維設(shè)計(jì)，所采用的設(shè)備儀器是普通計(jì)算機(jī)。
5、 參考文獻(xiàn)
B：
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[11]、劉忠明、風(fēng)力發(fā)電機(jī)齒輪箱設(shè)計(jì)制造技術(shù)的發(fā)展與展望[J]、機(jī)械傳動、2006
[12]、成大先、機(jī)械設(shè)計(jì)手冊第三卷、 北京、 化學(xué)工業(yè)出版社、1993
[13]、葉偉昌、機(jī)械工程及自動化簡明設(shè)計(jì)手冊、 機(jī)械工業(yè)出版社
[14]、關(guān)慧貞、機(jī)械制造裝備設(shè)計(jì)、 北京、 機(jī)械工業(yè)出版社
[15]、濮良貴 紀(jì)名剛、 機(jī)械設(shè)計(jì)、 北京、 高等教育出版社
注：
1、開題報(bào)告是本科生畢業(yè)設(shè)計(jì)（論文）的一個(gè)重要組成部分。學(xué)生應(yīng)根據(jù)畢業(yè)設(shè)計(jì)（論文）任務(wù)書的要求和文獻(xiàn)調(diào)研結(jié)果，在開始撰寫論文之前寫出開題報(bào)告。
2、參考文獻(xiàn)按下列格式（A為期刊，B為專著）
A：[序號]、作者（外文姓前名后，名縮寫，不加縮寫點(diǎn)，3人以上作者只寫前3人，后用“等”代替。）、題名、期刊名（外文可縮寫，不加縮寫點(diǎn)）年份、卷號（期號）：起止頁碼。
B：[序號]、作者、書名、版次、（初版不寫）、出版地、出版單位、出版時(shí)間、頁碼。
3、表中各項(xiàng)可加附頁。
5
湖 南 科 技 大 學(xué)
畢業(yè)設(shè)計(jì)（論文）任務(wù)書
機(jī)電工程 學(xué)院 機(jī)械設(shè)計(jì)制造及其自動化 系（教研室）
系（教研室）主任: （簽名） 年 月 日
學(xué)生姓名: 賴文馨 學(xué)號: 1103010401 專業(yè): 機(jī)械設(shè)計(jì)制造及其自動化
1 設(shè)計(jì)（論文）題目及專題： 5MW海上風(fēng)電機(jī)組齒輪傳動系統(tǒng)設(shè)計(jì)
2設(shè)計(jì)（論文）時(shí)間：自 2014 年 10 月 17 日開始至 2015 年 06 月 01 日止
3 設(shè)計(jì)（論文）所用資源和參考資料：
① 5MW傳動系統(tǒng)葉片額定轉(zhuǎn)速12.1rpm，額定發(fā)電機(jī)轉(zhuǎn)速1173.7rpm，齒輪箱傳動比為97:1。(一級行星、二級斜齒輪)
② 國外REpower 5MW、Multibrid M5000等風(fēng)電機(jī)組齒輪傳動系統(tǒng)的相關(guān)資料；相關(guān)教材，如《海上風(fēng)力發(fā)電機(jī)組設(shè)計(jì)》、《風(fēng)力機(jī)設(shè)計(jì)、制造與運(yùn)行)》等；圖書館電子資源數(shù)據(jù)庫搜集到的期刊論文，博士、碩士學(xué)位論文等。
4 設(shè)計(jì)（論文）應(yīng)完成的主要內(nèi)容：
1) 完成5MW海上風(fēng)電機(jī)組齒輪箱傳動形式、傳動比分配等設(shè)計(jì)與計(jì)算；
2) 完成傳動軸、齒輪、軸承等關(guān)鍵傳動零部件的選擇、設(shè)計(jì)、計(jì)算與校核；
3) 查閱相關(guān)文獻(xiàn)資料，撰寫開題報(bào)告；
4) 完成相關(guān)論文的翻譯(英譯中，不少于3000字)。
5 提交設(shè)計(jì)（論文）形式（設(shè)計(jì)說明與圖紙或論文等）及要求：
1) 完成5MW海上風(fēng)電機(jī)組傳動系統(tǒng)設(shè)計(jì)，提供傳動系統(tǒng)3D模型，裝配圖、零件圖等共折合A0圖紙不少于2.5張；
2) 設(shè)計(jì)計(jì)算說明書一份，畢業(yè)設(shè)計(jì)說明書的書寫格式和版面要求參照《湖南科技大學(xué)本科生畢業(yè)設(shè)計(jì)（論文）要求與撰寫規(guī)范》，說明書不少于40頁。
6 發(fā)題時(shí)間： 2014 年 10 月 17 日
指導(dǎo)教師： （簽名）
學(xué) 生： （簽名）
湖 南 科 技 大 學(xué)
畢 業(yè) 設(shè) 計(jì)（ 論 文 ）
題目
5MW海上風(fēng)電機(jī)組齒輪動系統(tǒng)設(shè)計(jì)
作者
賴文馨
學(xué)院
機(jī)電工程學(xué)院
專業(yè)
機(jī)械設(shè)計(jì)制造及其自動化
學(xué)號
1103010401
指導(dǎo)教師
沈意平
二〇一五年五月二十一日
附件2：任務(wù)書示例
湖 南 科 技 大 學(xué)
畢業(yè)設(shè)計(jì)（論文）任務(wù)書
機(jī)電工程學(xué) 院 系（教研室）
系（教研室）主任: （簽名） 年 月 日
學(xué)生姓名: 學(xué)號: 專業(yè):
1 設(shè)計(jì)（論文）題目及專題：
2 學(xué)生設(shè)計(jì)（論文）時(shí)間：自 年 月 日開始至 年 月 日止
3 設(shè)計(jì)（論文）所用資源和參考資料：
4 設(shè)計(jì)（論文）應(yīng)完成的主要內(nèi)容：
5 提交設(shè)計(jì)（論文）形式（設(shè)計(jì)說明與圖紙或論文等）及要求：
6 發(fā)題時(shí)間： 年 月 日
指導(dǎo)教師： （簽名）
學(xué) 生： （簽名）
附件3：指導(dǎo)人評語示例
湖 南 科 技 大 學(xué)
畢業(yè)設(shè)計(jì)（論文）指導(dǎo)人評語
[主要對學(xué)生畢業(yè)設(shè)計(jì)（論文）的工作態(tài)度，研究內(nèi)容與方法，工作量，文獻(xiàn)應(yīng)用，創(chuàng)新性，實(shí)用性，科學(xué)性，文本（圖紙）規(guī)范程度，存在的不足等進(jìn)行綜合評價(jià)]
指導(dǎo)人： （簽名）
年 月 日
指導(dǎo)人評定成績：
附件4：評閱人評語示例
湖 南 科 技 大 學(xué)
畢業(yè)設(shè)計(jì)（論文）評閱人評語
[主要對學(xué)生畢業(yè)設(shè)計(jì)（論文）的文本格式、圖紙規(guī)范程度，工作量，研究內(nèi)容與方法，實(shí)用性與科學(xué)性，結(jié)論和存在的不足等進(jìn)行綜合評價(jià)]
評閱人： （簽名）
年 月 日
評閱人評定成績：
附件5：答辯記錄示例
湖 南 科 技 大 學(xué)
畢業(yè)設(shè)計(jì)（論文）答辯記錄
日期：
學(xué)生： 學(xué)號： 班級：
題目：
提交畢業(yè)設(shè)計(jì)（論文）答辯委員會下列材料：
1 設(shè)計(jì)（論文）說明書 共 頁
2 設(shè)計(jì)（論文）圖 紙 共 頁
3 指導(dǎo)人、評閱人評語 共 頁
畢業(yè)設(shè)計(jì)（論文）答辯委員會評語：
[主要對學(xué)生畢業(yè)設(shè)計(jì)（論文）的研究思路，設(shè)計(jì)（論文）質(zhì)量，文本圖紙規(guī)范程度和對設(shè)計(jì)（論文）的介紹，回答問題情況等進(jìn)行綜合評價(jià)]
答辯委員會主任： （簽名）
委員： （簽名）
（簽名）
（簽名）
（簽名）
答辯成績：
總評成績：
NOTICE
The submitted manuscript has been offered by an employee of the Midwest Research Institute (MRI), a contractor of the US Government under Contract No. DE-AC36-99GO10337. Accordingly, the US Government and MRI retain a nonexclusive royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for US Government purposes.
This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof.
Available electronically at http://www.osti.gov/bridge
Available for a processing fee to U.S. Department of Energy and its contractors, in This paper describes a new research and development initiative to improve gearbox reliability in wind turbines begun at the National Renewable Energy Laboratory (NREL) in Golden, Colorado, USA. The approach involves a collaboration of NREL staff, expert consultants, and partners from the wind energy industry who have an interest in improving gearbox reliability. The membership of this collaborative is still growing as the project becomes more defined, but the goal is to include representatives ranging from the operators, owners, wind turbine manufacturers, gearbox manufacturers, bearing manufacturers, consultants, and lubrication industries. The project is envisioned to be a multi-year comprehensive testing and analysis effort. This will include complementary laboratory and field testing on a 600 to 750-kW turbine and gearbox of a configuration that exhibits reliability problems common to a broad population of turbines. The project will target deficiencies in the design process that are contributing to substantial shortfalls in service life for most designs. New design-analysis tools will be developed to model the test configuration in detail. This will include using multi-body dynamic analysis to model wind turbine loading, coupled to internal loading and deformations of the gearbox. Intellectual property conflicts will be minimized by maintaining a test configuration that does not replicate any specific manufacturer’s wind turbine model precisely, but represents a common configuration.
Background
The wind energy industry has experienced high gearbox failure rates from its inception [1]. Early wind turbine designs were fraught with fundamental gearbox design errors compounded by consistent under-estimation of the operating loads. The industry has learned from these problems over the past two decades with wind turbine manufacturers, gear designers, bearing manufacturers, consultants, and lubrication engineers all working together to improve load prediction, design, fabrication, and operation. This collaboration has resulted in internationally recognized gearbox wind turbine design standards [2]. Despite reasonable adherence to these accepted design practices, wind turbine gearboxes have yet to achieve their design life goals of twenty years, with most systems requiring significant repair or overhaul well before the intended life is reached [3,4,5]. Since gearboxes are one of the most expensive components of the wind turbine system, the higherthan-expected failure rates are adding to the cost of wind energy. In addition, the future uncertainty of gearbox life expectancy is contributing to wind turbine price escalation. Turbine manufacturers add large contingencies to the sales price to cover the warranty risk due to the possibility of premature gearbox failures. In addition, owners and operators build contingency funds into the project financing and income expectations for problems that may show up after the warranty expires. To help bring the cost of wind energy back to a decreasing trajectory, a significant increase in long-term gearbox reliability needs to be demonstrated.
In response to design deficiencies, modification and redesign of existing turbines is a continual process in current production units, but it is difficult to validate the effectiveness of the modifications in a timely manner to assure that multiple units with unsatisfactory “solutions” are not deployed. Presently, gear manufacturers introduce modifications to new models, replacing a deficient component with a re-engineered one that is
1 thought to deliver higher performance. To test these new designs, the re-engineered gearboxes are installed and a field evaluation process begins. This approach may eventually lead to the reliability goals needed, but it may take many years to develop the needed confidence in a solution, and reduce the uncertainty to a level where it will reduce turbine costs. By that time, the wind turbine industry may have moved to larger turbines or different drivetrain arrangements that could invalidate these solutions. Moreover, the fundamental failure mechanisms of the original problem may never be understood, making it easier for design unknowns to be inadvertently propagated into the next generation of machines.
This paper summarizes a long-term NREL/DOE project to explore options to accelerate improvements in wind turbine gearbox reliability by addressing the problems directly within the design process. In the execution of this program, our intentions are to improve the accuracy of dynamic gearbox testing to assess gearbox and drivetrain options, problems, and solutions under simulated field conditions. The project will evaluate the wide range of possible load events that comprise the design load spectrum [6], and how critical design-load cases
[7] may translate into unintended bearing and gear responses such as misalignment, bearing slip, and axial motion.
NREL has made a commitment to address gearbox reliability as a major part of its research agenda, and plans to engage a wide range of stakeholders including researchers, consultants, bearing manufacturers, gearbox manufacturers, wind turbine manufacturers, and wind turbine owner/operators to form a gearbox reliability collaborative (GRC). The collaborative will address major gearbox issues with the common goal of increasing overall reliability of wind turbines. The approach will involve three major technical efforts which include field testing, dynamometer testing, and drivetrain analysis. These elements make up a comprehensive strategy that will address the true nature of the problem and hopefully spark a spirit of cooperation that can lead to better gearboxes.
Observations on the Basic Problems
While it is premature to draw firm conclusions about the nature of these failures, some reasonable observations have been made to help narrow the course and scope of this project.
1. Most of the problems with the current fleet of wind turbine gearboxes are generic in nature, meaning that the problems are not specific to a single gear manufacturer or turbine model. Over the years, most wind turbine gearbox designs have converged to a similar architecture with only a few exceptions. Therefore, there is an opportunity to collaborate among the many stakeholders in the wind turbine gearbox supply chain to find root causes of failures and investigate solutions that may advance the collective understanding of the industry.
2. The preponderance of gearbox failures suggests that poor adherence to accepted gear industry practices, or otherwise poor workmanship, is NOT the primary source of failures. Of course, some failures have been directly attributed to quality issues, and further improvements in this area are not precluded from consideration, but we assume that manufacturers are capable of identifying and correcting quality control problems on their own if they choose to do so. Therefore, the target of this project will be the greater problem of identifying and correcting deficiencies in the design process that may be diminishing the life of the fleet.
3. Most gearbox failures do not begin as gear failures or gear-tooth design deficiencies. The observed failures appear to initiate at several specific bearing locations under certain applications, which may later advance into the gear teeth as bearing debris and excess clearances cause surface wear and misalignments. Anecdotally, field-failure assessments indicate that up to 10% of gearbox failures may be manufacturing anomalies and quality issues that are gear related, but this is not the primary source of the problem.
4. The majority of wind turbine gearbox failures appear to initiate in the bearings. These failures are occurring in spite of the fact that most gearboxes have been designed and developed using the best bearing-design practices available. Therefore, the initial focus of this project will be on discovering weaknesses in wind turbine gearbox bearing applications and deficiencies in the design process.
2 Furthermore, we believe that the problems that manifested themselves in the earlier 500-kW to 1000kW sizes five to ten years ago still exist in many of the larger 1 to 2 MW gearboxes being built today with the same architecture. As such, it is likely that lessons learned in solving problems on the smaller scale can be applied directly to future wind turbines at a larger scale, but with less cost.
Using these observations to help bound the problem, we reason that the accepted design practices that are applied successfully throughout other industrial bearing applications must be deficient when applied to wind turbine gearboxes. This characterization is based primarily on anecdotal field-failure data, and the experience of gear and bearing experts who have studied the problems for many years. Unfortunately, the available analytical methods to assess design life in typical gearbox designs are not accurate enough to shed much light on this problem, so much of the investigation must be conducted empirically.
A major factor contributing to the complexity of the problem is that much of the bearing design-life assessment process is proprietary to the bearing manufacturers. Gearbox designers, working with the bearing manufacturers, initially select the bearing for a particular location and determine the specifications for rating. The bearing manufacturer then conducts a fatigue life rating analysis to determine if the correct bearing has been selected for the specific application and location. Generally, a high degree of faith is required to accept the outcome of this analysis because it is done with little transparency. Even though bearing manufacturers claim adherence to international bearing- rating standards (ISO 281:2007 [8]), each manufacturer uses its internally developed design codes that have the potential to introduce significant differences that can affect actual calculated bearing life without revealing the details to customers. A new code is needed in the public domain that will give the industry a common method for due diligence in bearing design [9].
Moreover, since the bearing manufacturers do not have broad or intimate knowledge of gearbox system loads and responses that may be contributing to unpredicted bearing behavior beyond the bearing mounting location such as housing deformations, they are not capable of making valid root-cause analyses on their own. A broader collaboration of the various stakeholders, each of whom holds a piece of the answer, is clearly needed.
Gearbox Reliability Collaborative
Many of the gearbox problems described above may be the direct result of institutional barriers that hinder communication and feedback during the design, operation, and maintenance of turbines. In isolation, it is very difficult for single entities in the supply chain to find proper solutions. Hence, a collaborative is needed to bring together the various portions of the design process, and to share information needed to address the problems. This promises to be one of the more challenging parts of this project, as information sharing introduces perceived risk to the protection of intellectual property, which is guarded dearly by most companies. A goal of this project is to establish this cooperative framework while protecting the intellectual property rights of all parties. These concerns will be addressed through legal agreements with NREL, and will be further mitigated since the project does not focus on any manufacturer’s specific design. The collaborative is operated by NREL staff and expert consultants hired by NREL to guarantee privacy of commercially sensitive information and data. In addition, a goal of the collaborative is to engage key representatives of the supply chain, including turbine owners, operators, gearbox manufacturers, bearing manufacturers, lubrication companies, and wind turbine manufacturers. Each party holds information and experience that is needed to guide the project, supply the components, and interpret results of the test. The collaborative partners will benefit by having input throughout the testing setup and execution, and will have access to data within the agreements established by the cooperative. Results will be released by the GRC as agreed upon by its members.
Generic Wind Turbine Drivetrain Architecture
The selected configuration is comprised of a single main bearing upwind of the gearbox with rear non-locating support bearings inside the gearbox. Trunnion mounts on either side of the gearbox are used to attach it to a mainframe or bedplate, typically through elastomeric bushings used to dampen noise and vibrations. Torque reactions are resolved through the trunnion support assembly that is normally an integral part of the gear housing. The external geometry of this configuration is shown in
The low speed stage of the gearbox is a planetary configuration with either spur or helical gears. The sun pinion drives a parallel intermediate shaft that in turn drives a high speed stage. Both the intermediate and high speed stages use helical gears. A generalized schematic of a typical wind turbine gearbox is shown in Figure 2. 4
Critical bearing locations are defined as places that have exhibited a high percentage of application failures in spite of the use of best current design practices. In the generic configuration, there are three critical bearing locations that we have identified:
1. Planet bearings
2. Intermediate shaft-locating bearings
3. High-speed locating bearings
Each location has exhibited a relatively high degree of bearing failures with a relatively low dependence on machine size, machine make, or model.
A Three Point Plan
As previously mentioned, some aspects of the wind turbine, gearbox, and bearing design process are preventing gearboxes from reaching expected life. These deficiencies could be the result of many factors, including:
? the possibility that one or more critical design-load cases were not accounted for in the design load spectrum,
? that transfer of loads (both primary torque loads and non-torque loads) from the shaft and mounting reactions is occurring in a non-linear or unpredicted manner, or
? that components within the gearbox (especially the bearings) are not uniformly specified to deliver the same level of reliability.
Due to the complexity of this problem, a comprehensive approach that expands our existing base of knowledge and capabilities will be required. Under this project, NREL plans an integrated three-pronged approach of analysis, dynamometer testing, and field testing as shown in Figure 3.
Figure 3 - Comprehensive Strategy to Investigate Wind Turbine Gearbox Reliability
5 Laboratory testing of a representative instrumented drivetrain in the NREL 2.5-MW dynamometer will be coordinated with parallel field tests on an identical instrumented drivetrain conducted at a nearby wind farm site. With the benefit of hindsight, the selected drivetrain will be upgraded prior to testing to current state-ofthe-art to eliminate known design weaknesses and quality issues as best as possible. These upgrades may include different bearing types, cooling and filtration system upgrades, lubrication changes, and gear tooth modifications. The test specimens will therefore not be precise representations of any manufacturer’s design. The laboratory and field measurements will be validated with dynamic analysis using an accurate structural-system model of the selected drivetrain.
The test will be based on a 600 to 750-kW wind turbine selected by a committee of expert gearbox consultants hired by NREL under the GRC. The exact details of the drivetrain to be tested and analyzed are confidential to the members of the GRC. Project success will be highly dependent on making the right measurements that correctly characterize the behavior of the critical bearings under various loading scenarios. Instruments will be developed and installed to capture data about significant loads, deflections, thermal effects, dynamic responses and events, and changes to the condition of the lubricant.
Critical loads measurements will include shaft bending and torque on the input shafts, but also measurements of how load sharing varies dynamically from one planet bearing to another. Similarly, measurements will be made to determine how the load is being shared between bearings axially along a single planet shaft. Displacement sensors to make continuous measurements will be installed internally, if possible, wherever gear tooth clearances or alignments of the gears might be affected. These locations may include bearing inner ring to outer ring alignments and clearances, shaft axial motions, bearing slip (inner or outer motions or bearing components), roller slipping or skidding, combined roller slip, relative motion of carrier to housing, sun pinion displacement relative to carrier, sun-pinion axial motion, housing stiffness, and displacement measurements of housing. We anticipate that certain locations will be difficult to access with standard instrumentation. Temperature measurements will be made at all critical bearing locations, including the inner rings, the outer rings, and planet bearings. Lubrication monitoring will include bulk sump temperature, cleanliness (e.g., particulate, ferrous, additive, and water), and filter debris. Laboratory analysis will be conducted frequently on all test specimens.
The test data will be analyzed and correlated to look for bearing behavior that is unexpected, non-linear, or is suspect under a wide range of input conditions. If this behavior can be correctly documented and understood, it may not be necessary to reproduce every type of bearing failure if subsequent analysis can demonstrate that certain abnormal behavior can result in loss of bearing life.
Dynamometer Testing
The National Renewable Energy Laboratory operates a 2.5-MW dynamometer test facility funded by the U.S. Department of Energy at its National Wind Technology Center in Golden, CO that is dedicated to the testing of wind turbine drive trains [12]. Since 1999, this facility has been in continuous operation providing testing services to prototype and production wind turbine drive trains up to 2 MW in size. NREL plans to use this facility and its support staff to conduct full-scale tests on the 750-kW drivetrain selected. A schematic of the facility is shown in Figure 4.
One of the benefits of using a full scale drive-train