插入芯体的螺旋型波纹管液氮流动特性仿真研究

Numerical study on the flow characteristics of liquid nitrogen flow in helically corrugated pipes with inserts

液氮在传输管线中的压降特性一直是高温超导电缆低温系统最重要的设计参数之一。以往针对液氮流动阻力的研究大多在直管或环型波纹管方面,主要关注其几何尺寸对压降的影响。然而,实际应用的长距离高温超导电缆更适合应用螺旋型波纹管。本文主要研究螺旋型波纹管插入导体芯后管内液氮的流动特性。通过建立三维数值模型,对螺旋型波纹管中插入直径为5、8 mm的3根或4根螺旋绞织缠绕导体芯时的液氮流动阻力进行对比分析。结果表明,导体芯的粗细、导体芯自身螺旋缠绕的节距、及导体芯缠绕时相互间形成的空隙大小均是直接影响液氮流动压降、摩擦因子的关键因素,并获得了液氮摩擦因子与上述参数的定量关系。

Prediction of liquid nitrogen pressure drop in high temperature superconducting(HTS) power transmission lines is an important design parameter. Researches in literature mainly focused on the relationship between the pressure drop and the geometry parameters of straight pipes or annually corrugated pipes. However, helically corrugated pipes are more feasible for long-distance deployment of the HTS lines. This paper discussed the flow characteristics of liquid nitrogen inside helically corrugated pipes with insertion of multiple cables by numerical simulations. Influence of the diameter(5 mm, 8 mm), quantity(3 or 4) and the arrangement(parallel or spiral) of the cables were investigated parametrically. Results show that the size and the pitch of the cables, and the little gaps between the cables are critical factors affecting the pressure drop and the friction factor. Quantitative relations between the friction factor and the above-mentioned parameters were proposed.