同步自转型CO2涡旋膨胀机跨临界膨胀气液相变延迟特性及流动控制机理研究

Recovery of throttle expansion energy by scroll expander is an important way to improve the performance of transcritical CO2 heat pump and refrigeration cycle. However, the delayed gas-liquid phase transition in the process of CO2 transcritical phase change expansion will lead to a significant decrease in the expander performance and the cycle efficiency. By means of numerical simulations and experiments, this project will study the gas-liquid phase transition delay characteristics and the energy-work conversion mechanism of the transcritical expansion of CO2 scroll expander. This project will study the cavitation mechanism of the opposite suction vortex and the induction mechanism of gas-liquid phase transition in CO2 scroll expander, and study the variation law of gas-liquid phase transition delay characteristics based on the control of opposite suction vortex. The flow control method of the gas-liquid phase transition delay in CO2 transcritical expansion will be summarized and put forward. Through the implementation of this project, we can deeply reveal the correlation mechanism between the energy-energy conversion efficiency and the gas-liquid phase transition delay in the process of transcritical phase change expansion of CO2 scroll expander, and clarify the induction mechanism of the suction cyclone cavitation of CO2 scroll expander to the nucleation and gas-liquid phase change of the transcritical expansion bubble. The research results will provide theoretical support for weakening the gas-liquid phase transition delay of CO2 transcritical expansion, reducing the loss of phase transition delay, and improving the power conversion efficiency of CO2 scroll expander.

利用涡旋膨胀机回收节流膨胀功是提升跨临界CO2热泵与制冷循环性能的重要途径。然而，CO2跨临界相变膨胀过程中发生的气液相变延迟会导致膨胀机性能以及循环效率大幅下降。针对同步自转型涡旋膨胀机，本项目通过数值模拟与试验手段，研究CO2涡旋膨胀机跨临界膨胀气液相变延迟特性与能功转换机理；研究CO2涡旋膨胀机对置吸气旋涡空化以及气液相变诱导机理；研究基于对置吸气旋涡控制的气液相变延迟特性变化规律；在此基础上，总结并提出CO2跨临界膨胀气液相变延迟的流动控制方法。通过实施本项目，可以深入揭示CO2涡旋膨胀机跨临界相变膨胀过程的能功转换效率与气液相变延迟的关联机理，并阐明CO2涡旋膨胀机吸气旋涡空化对CO2跨临界膨胀气泡核化与气液相变的诱导作用机制。研究结果将为弱化CO2跨临界膨胀气液相变延迟、减小相变延迟损失，进而改善CO2涡旋膨胀机能功转换效率提供理论支撑。

利用涡旋膨胀机回收节流膨胀功能够有效提升跨临界二氧化碳热泵与制冷循环性能。然而，CO2跨临界相变膨胀过程中发生的气液相变延迟会导致膨胀机性能以及循环效率下降。针对CO2热泵循环涡旋膨胀机跨临界变相膨胀过程中发生的气液相变延迟问题，本项目结合数值模拟与试验方法，围绕跨临界相变膨胀流动特性、气液相变延迟机理以及流动控制方法等三个方面内容展开研究。基于本项目发展的CO2涡旋膨胀机跨临界相变膨胀VOF多相流非定常数值模拟方法，揭示了CO2涡旋膨胀机跨临界气液相变膨胀流动特征；结合熵产理论+Omega涡识别方法，阐释了CO2涡旋膨胀机跨临界气液相变膨胀流动的不可逆损失机理；在此基础上，探讨了吸气旋涡空化对跨临界膨胀气液相变的诱导作用机制，并获得了吸气结构对吸气湍流拟序旋涡及流动损失的影响规律，提出了基于吸气旋涡导流调控的流动增效控制方法。上述研究结果为弱化CO2跨临界膨胀气液相变延迟、减小相变延迟损失，改善CO2涡旋膨胀机能功转换效率提供了理论支撑。依托本项目，发表相关标注国际顶级期刊论文4篇，国际重要期刊论文1篇，授权/公开国家发明专利3项，培养博士研究生2人，硕士研究生4人，相关研究持续获批国家自然科学基金面上项目1项。

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