低温液体透平膨胀机旋涡空化流动研究和控制

Cryogenic liquid turbine expander is an effective energy-saving component and used to replace the conventional J-T valve in air separation and natural gas liquefaction systems, and it can reduce the total power consumption by 3-6%. Over recent 10 years, the research team has been working on the development of cryogenic liquid turbine expander, and significant breakthroughs have been achieved in various aspects. The measured overall performance of the developed turbine expander has reached the same level of the imported machines, which has filled the domestic technology void in cryogenic liquid turbine expander. As it is used air separation unit or in LNG plant, the turbine expander is always installed in the main flow process, thus high-level operation stability is required for the turbine expander. Some similarities between the cryogenic liquid turbine expander and the conventional hydraulic turbine are demonstrated from our early primitive study, i.e. significant swirling and cavitation flow is also encountered at off-design condition of turbine expander. It can lead to significant pulsations in turbine expander exiting flow rate and other parameters, and induce severe material cavitation erosion to component surface and structural vibration, which threatens the operation safety of the entire system. However, the thermodynamic effect of cryogenic fluids is significant, and the swirling and cavitating flow of the liquid turbine expander is much more complicated in comparison with the conventional hydraulic turbine. The flow mechanism and major influential factors haven’t been yet clear. In the present project, in-depth numerical and experimental study will be conducted to explore the physics of swirling and cavitating flow. Characterization of swirling and cavitating flow will be performed. Then the flow optimization method will be developed with innovative objective function, which incorporates the flow characterization method and overall performance index. With such a method, both overall performance and stability of the turbine expander will be simultaneously enhanced. This will largely promote the applications of turbine expander in energy-consuming air-separation and LNG industry and produce tremendous economic and social benefits.

低温液体透平膨胀机是低温循环关键节能设备，用于替代低温空分和天然气液化装置中传统高压液体节流阀，使循环总能耗降低3-6%。本课题组通过十余年研发，在液体膨胀机关键技术上取得突破，研制的样机实测性能达到同期国外产品指标, 填补了国内空白。但无论在空分还是在液化装置中，液体膨胀机均用在主流程，其运行稳定性要求很高。我们前期初步研究表明，与水轮机相似，在非设计工况，液体膨胀机发生了显著旋涡空化。导致输出介质流量、压力等大幅脉动，将诱发关键部件表面气蚀破坏和机组振动，威胁整个系统安全运行。而低温流体热力学效应显著，使得液体膨胀机旋涡空化流动更复杂，其成因及主要影响参数等尚不明晰。本项目将通过深入系统的数值和实验研究，探明流动机理，获得旋涡空化表征方法；以抑制旋涡空化为目标，建立膨胀机内流优化控制方法。提升其性能及运行稳定性，促进此项节能技术在高能耗空分和液化装置中推广应用，具有显著经济和社会意义。

按照项目计划，完成了各项内容的系统研究，主要包括低温液体膨胀机旋涡空化流动研究、旋涡空化流动的表征；基于低温实验的数值方法验证和空化模型验证及改进；旋涡空化的抑制等。.通过上述内容的研究，探明了液体膨胀机内流机理和空化机制，获得了旋涡空化的表征方法；以抑制旋涡空化为优化目标，以膨胀机旋涡空化的敏感几何参数为变量，发展了全液体膨胀机和两相膨胀机内流优化控制和空化抑制的方法，形成了自主化的专有技术，并申请了国家发明专利。.在项目的执行期间取得了多方面的成果：获得美国发明专利授权1件、中国国家发明专利授权1件；申请国家发明专利8件；发表SCI/EI高水平英文学术论文8篇；实现了液体膨胀机专利技术的工业转化应用，签订液体膨胀机技术许可应用合同1份（100万元）；培养博士后、博士生、硕士生十余名。此外，项目执行期间骨干成员参加国际高水平学术会议5人次；国外/海外联合培养和合作研究2人次；应邀参数国内行业大会并做主旨演讲2人次。.研究成果具有重要理论学术意义和应用价值。在某种程度上弥补了低温空化理论和基础数据等方面的不足，同时为低温液力机械（如液体膨胀机和泵）的空化研究和抗空化设计提供了重要参考。为本课题组的自主化低温液体膨胀机技术在工业空分和天然气液化领域的推广应用提供了重要支撑。