內燃機余熱能轉化熱力單元和材料性能強化設計和集成優化研究報告

吳玉庭 張紅光 陳夏 張業強 楊凱

摘 要：該報告對蒸發器和冷凝器內部能量傳遞機理進行研究，探索了蓄熱過程傳熱傳質的強化機理與方法，建立內燃機廢熱有機朗肯循環單螺桿膨脹機實驗臺。在前幾年工作的基礎上，2013年度該研究的主要進展如下：（1）研究組建立了煙氣-有機工質蒸發器和空冷冷凝器傳熱的數學模型，編制了蒸發器和冷凝器的設計分析程序，進行了247 kW柴油機廢氣余熱有機朗肯循環煙氣蒸發器和空冷冷凝器的設計計算，計算獲得了管翅式蒸發器總換熱量、各區換熱量及其進出口參數隨內燃機工況的變化規律。研制了螺旋盤管強化傳熱鈦管和波紋管煙氣蒸發器和彎曲型平行流冷凝器。（2）提出了一種螺旋管熔鹽蓄熱換熱器的創新方案，建立了蓄熱換熱器的數學模型，并進行了螺旋管蓄熱換熱器和套管式蓄熱換熱器的設計計算。搭建了套管式蓄熱換熱單元性能測試實驗系統，進行了套管蓄熱換熱器的蓄熱、放熱和傳熱試驗。（3）分析去年試驗存在的問題，更換了適合該系統余熱負荷的Φ155 mm螺桿的單螺桿膨脹機，研制了螺旋盤管鈦管煙氣蒸發器和彎曲型平行流冷凝器，重新選擇了多級離心泵，優化了有機朗肯循環流程，建立了247 kW柴油機廢氣余熱有機朗肯循環試驗臺，進行柴油機變工況廢氣余熱有機朗肯循環試驗，獲得了不同發動機工況下有機朗肯循環系統性能參數（輸出功率、膨脹機效率、有機朗肯循環效率、換熱量等）隨發動機工況變化的性能規律。（4）該課題組選取了8種滑移溫度不同的非共沸混合工質，研究了內燃機變工況下，非共沸混合工質對有機朗肯循環余熱回收系統性能的影響，對比分析了4種純工質、4種共沸混合工質和4種非共沸混合工質對變工況下車用柴油機有機朗肯循環余熱回收系統性能的影響。（5）提出比轉數作為有機朗肯循環工質泵的選型指標，給出了蒸發溫度為100 ℃，冷凝溫度為45 ℃時不同工質所需泵的比轉數隨功率的變化關系，并給出了不同比轉數適用泵的建議。進行了旋噴泵的性能試驗，獲得了不同頻率下泵的揚程和效率隨流量的變化規律。

關鍵詞：內燃機 余熱 有機朗肯循環 單螺桿膨脹機

Abstract：Main progresses of the project in 2013 are as follows： （1） Mathematical models on heat transfer of flue gas - organic working fluid evaporator and air cooling condenser were established. Design analysis program of evaporator and condenser were developed. Design for organic Rankine cycle （ORC） of 247 kW diesel waste heat of flue gas evaporator and air condenser was made. By analyzing the heat transfer characteristics of an ORC evaporator applied on an R425 diesel engine， the mechanism of the total and zone heat transfer rates， inlet and outlet parameters with engine speed and load were obtained. Spiral titanium coil tube evaporator， bellows evaporator and curved parallel flow condenser were developed. （2） An innovative concept for spiral coil heat exchanger with molten salt thermal storage was proposed. Mathematical models of heat exchanger with thermal storage were established， and calculation for spiral coil and sleeve heat exchanger with storage was performed. Experiments on heat storage， discharge and heat transfer of sleeve heat transfer unit were made. （3） By replacing with a single screw expander of Φ155 mm， multi-stage centrifugal pump， spiral titanium coil tube evaporator and curved parallel flow condenser， an modified ORC waste heat recovery system from exhaust gas of 247 kW diesel was made. The performances with engine power were tested. （4） The first law and second law of thermodynamics are utilized to investigate the variation of net power output， thermal efficiency， exergy efficiency and mass flow rates of 8 kinds of zeotropic mixtures under various operating conditions of a diesel engine. The waste heat recovery efficiency （WHRE）and power output increasing rate （POIR） are also presented and studied. （5） Specific revolution was proposed as the selection indicator of organic Rankine cycle working fluid pump. The relation between specific revolution and power for different working fluid pump was given under the evaporation temperature of 100 ℃ and the condensing temperature of 45 ℃.Suitable pumps for different specific revolutions were recommended. A rotary jet pump performance test was conducted， and the variations of head and efficiency with frequencies were obtained.

Key Words：Internal combustion engine；Waste heat；Organic rankine cycle；Single screw expander

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