Abstract:

Annular flow of an inner gas core and an annular liquid film is one of the most important flow patterns in engineering application. A disturbance wave occurs at interface of liquid film and gas core, which wave frequency is a characteristic parameter for describing the disturbance wave at annular flow interface and for studying mass and heat transfer in annular flow. A near infrared (NIR) equipment was designed to measure liquid film thickness. Non-contact thickness measurement of partial liquid film in annular flow was achieved by vertical optical path and inserted light guide tube to cover one side of liquid film and liquid droplet in gas core. Then frequency of interface disturbance wave was estimated by power spectral density. Quantitative study on annular flow in 50-mm-diametered vertical tube obtained wave frequencies at 70 different flow conditions with pressure ranging from 0.1 to 0.8 MPa, liquid volume flux ranging from 1.2 to 2.5 m³·h⁻¹, and gas volume flux of 90 and 110 m³·h⁻¹. These experimental results were used to verify current models, and a St-Fr model was established to predict disturbance wave frequency from flow parameters, which the Strouhal number was to describe influence of liquid phase and the Froude number was to describe influence of gas phase. The mean absolute error (MAE) of the St-Fr model prediction to experimental results is 11.42%.

Key words: near infrared, absorption, gas-liquid flow, riser, annular flow, wave frequency, power spectral density, model

摘要：

气液两相环状流的相界面存在扰动波，波动频率是描述环状流界面扰动波特性的关键参数，对环状流的传质传热研究有重要参考价值。利用近红外光的吸收特性，设计了液膜检测装置，采用垂直对射光路设计，并通过置入式导光管屏蔽一侧液膜和气芯夹带液滴，实现了对环状流局部液膜的非接触式检测。在此基础上对界面扰动波进行了频域分析，运用功率谱密度估计，对50 mm管径竖直上升管环状流界面扰动波波动频率进行了定量研究，得到0.1～0.8 MPa不同压强条件下，共70个流动条件的环状流界面扰动波频率值。利用实验结果对现有模型进行验证分析，在此基础上利用Strouhal数描述液相流动条件的影响，利用Froude数描述气相流动条件的影响，建立了预测环状流界面扰动波波动频率的St-Fr模型，经实验数据验证预测的平均绝对误差（MAE）为11.42%。

关键词: 近红外, 吸收, 气液两相流, 上升管, 环状流, 波动频率, 功率谱密度, 模型