超臨界有機朗肯循環之渦輪機分析與研究

Research and Development of a Supercritical Organic Rankine Cycle (SORC) Turbine

陳雲飛(Yun-Fei Chen)

指導教授 ： 蔣小偉

國立清華大學/工學院/動力機械工程學系/碩士(2015年)

摘要

目前全球能源使用以熱能形式占能源消耗量90%以上，其中僅40%熱能轉換為製程熱能、機械功、電力或化學能；其餘50%熱能則以廢熱形式排放於環境，故中低階餘熱回收的市場量相當可觀。目前主要餘熱回收方式為有機朗肯循環(ORC)，其有機流體有較低沸點溫度可適用於低溫熱源蒸發，其效率大多落在10%出頭。為了更進一步提升效率，目前學術界多朝超臨界循環研究。超臨界有機朗肯循環(SORC)乃將有機流體加壓至臨界點以上，使做功段擁有更大的能量差，但其工作條件所需的設配較為嚴苛，其研究量也尚不完備，固本研究將針對SORC之做功元件進行研究。
首先為了決定做功元件設計規格，必須確定使用的工作流體和熱力性質。研究過程中，首先針對200℃和300℃熱源溫度進行超臨界流體效率比較，並同時和次臨界循環做比對。200℃熱源的效率最佳的超臨界流體比次臨界提升了7%；而300℃下可提升20%。回收溫度300℃下效率最佳的超臨界態流體為R123，其效率可達17.71%。
根據其熱力條件和發電需求將採用徑向式渦輪作為研究目標， 並根據文獻[32]中針對次臨界流體的徑向式渦輪參數設計方法，進行超臨界R123的渦輪參數設計，並將設計結果用CFD軟體進行流場模擬，除了透過模擬結果對比參數計算結果外，可針對轉子葉形進行最佳化調整，以得到最大輸出與做功效率。並將設計完成之超臨界R123渦輪轉子與次臨界流體之渦輪轉子文獻進行比較討論。

關鍵字

ORC ； 渦輪 ； 餘熱回收

並列摘要

For now the global energy use ,over 90% energy consumption is in heat form ,but only 40% heat energy be transferred into mechanical work , electricity or chemical energy etc; the rest 50% would be emitted as the waste heat, so it is considerable to the low and medium waste heat recover market . For now the primary waste heat recover way is Organic Rankin Cycle (ORC). The organic fluid has a lower boiling temperature suitable for the low temperature heat source to evaporate. The efficiency is about 10%. In order to further raise the efficiency, the academic community takes their research in supercritical cycle. Supercritical Organic Rankin Cycle (SORC) is to pressurize the organic fluid over the critical point to produce larger energy gap to make work. But the equipment in need would have more restrictions due to the working condition, also the incompleteness of the research data. According to this the research put the emphasis on the SORC working component.

First is to decide the designation of the component. We have to decide the working fluid and its thermal character. In the research procedure, we compare the 200℃ and 300℃ heat source temperature efficiency and compare it to the subcritical cycle. To the 200℃ fluid the best efficiency only 0.78% better than the subcritical but 2.95% in 300℃. The best efficiency fluid in 300℃ is R123 which can reach to 17.71%.

According to the thermal condition and the working range we use radial turbine as the research target. Do the fluid simulation using subcritical fluid coefficient of the radial turbine according to document [23]. Compare the result and the isentropic efficiency to confirm the reliability of the simulation .Use the same model to the supercritical fluid’s thermal character then compare and discuss their results. In the future, we would consult the related document about the advised range of the radial turbine coefficient to design R123 stator and rotator, then adjust the coefficient due to the simulation result to get the largest output and best working efficiency.

參考文獻

Gary J. Zyhowski, Andrew P. Brown, Abdennacer Achaichiab” HFC-245fa Working Fluid in Organic Rankine Cycle - A Safe and

Economic Way to Generate Electricity from Waste Heat” 14-17th june 2010, Lausanne, Switzerland

Hsiao-Wei D. Chiang*, Chih-Yung Huang† and Sung-Wei Hsu’’ Performance analysis and optimization of a transcritical ORC system” ASME-ORC 2013 Book of Abstracts

A. Schuster , S. Karellas , R. Aumann “Efficiency optimization potential in supercritical Organic Rankine Cycles” Energy 35 (2010) 1033–1039

Zhang Shengjun*, Wang Huaixin, Guo Tao” Performance comparison and parametric optimization of subcritical Organic Rankine Cycle (ORC) and transcritical power cycle system for low-temperature geothermal power generation” Applied Energy 88 (2011) 2740–2754