Numerical simulation of gas-liquid flow through a 90° duct bend with a gradual contraction pipe

Abstract

The effect of a gradual contraction pipe (GCP) on gas-liquid flow in a circular-sectioned horizontal to vertical 90° duct bend was investigated by computational fluid dynamics (CFD) simulation. The hydrodynamics of gas-liquid flow in 90° duct bends with and without a GCP in the vertical section were compared using a 3D steady Eulerian-Eulerian approach. The predicted static pressure in the vertical section of the pipes and the pressure drop in the whole pipe were consistent with experimental data. Results of simulations showed that liquid could distribute more uniformly at the exit of the pipe with a GCP. The increased uniformity was accompanied by an increase in pressure drop by a factor of less than 10% compared to the pipe without a GCP. The position of minimum pressure in the bend was changed by the GCP. A GCP can alter the trajectories of the fluid and secondary flow. As a result, the fluid can quickly reach a steady state downstream from the bend.

中文概要

目 的

90°弯管广泛应用于工业中的流体输送, 但是流体 在经过弯头时会由于离心力的作用而导致弯头 下游管道内出现流体分布不均的现象, 从而影响 后续的生产过程。本文将实验和计算流体力学 (CFD)模拟的方法结合研究缩径管对经过弯头 后的流体整流作用并分析原因, 以期为缩径管在 工业中的应用提供一定的参考。

创新点

1. 提出在弯头后的管路中增加缩径管来调整流体 的方法; 2. 在冷模实验数据验证模拟结果的正确 性的基础上, 根据CFD 模拟得到的管道内的压 力、流体速度、相分布及湍动能分布详细分析了 缩径管能起整流作用的原因。

方法

1. 通过冷模实验所得的压力数据与模拟值进行对 比, 证明模拟所采用模型的正确性; 2. 通过对不 同流体入口条件模拟结果的比较, 找到缩径管的 作用规律; 3. 通过CFD 模拟得到管道内的压力、 流体速度、相分布及湍动能, 分析缩径管的整流 原理。

结论

1. 模拟所采用的模型可较好地反映管道内的流体 流动情况; 2. 缩径管能起到很好的整流效果; 3. 缩 径管可使流体加速, 促进流体的快速混合, 因此 能够使不稳定的流体快速达到稳定状态。