超临界二氧化碳轴流透平冷却系统耦合传热特性数值研究

Numerical investigations on the coupled heat transfer characteristics of the cooling system of a supercritical carbon dioxide axial turbine

针对某型超临界二氧化碳(S-CO_(2))轴流透平开展了冷却系统设计,通过抽取压缩机后管道中低温S-CO_(2)对干气密封、转轴和壳体进行冷却,以保证干气密封工作温度低于200.0℃。采用耦合传热方法分析了该冷却系统的流动和传热特性,对比了不同冷却方案的干气密封、转轴与壳体等固体域的温度分布。结果表明:采用转轴冷却方案时转轴温度降幅达到220.3℃,干气密封最高温度为229.1℃;进一步引入温度更低流量更大的S-CO_(2)对壳体进行冷却,能抑制透平进口处高温主流的加热作用,转轴温度降幅增加到244.1℃,干气密封最高温度下降到181.2℃,同时S-CO_(2)轴流透平干气密封、壳体和转轴等被冷却部件温度梯度可控。该冷却系统为S-CO_(2)轴流透平的安全可靠运行提供了解决方案。

A cooling system was designed for a supercritical carbon dioxide(S-CO_(2))axial turbine.The dry gas seal,shaft and casing were cooled by extracting the low temperature S-CO_(2) in the pipeline behind the compressor to ensure that the dry gas seal operating temperature was below 200℃.The flow and heat transfer characteristics of the cooling system were analyzed using the coupled heat transfer method,and the temperature distributions of solid domains such dry gas seal,shaft and casing of different cooling schemes were compared.The research shows that the temperature drop of the shaft reaches 220.3℃ when theshaft cooling scheme is adopted,and the maximum temperature of the dry gas seal is 229.1℃.Further introduction of S-CO_(2) with lower temperature and larger flow rate to cool the casing can inhibit the heating effect of the high temperature mainstream at the turbine inlet.The temperature drop of the shaft increases to 244.1℃,and the maximum temperature of the dry gas seal decreases to 181.2℃.Meanwhile,the reasonable temperature gradient of the cooled domains such as the dry gas seal,shaft and casing is achieved.The cooling system designed in this paper provides a solution for the safe and reliable operation of S-CO_(2) axial turbines.