气液两相流中气泡速度的电磁互相关测量

气液两相流作为一种工业领域中普遍存在的流态,在测量时需考虑气相和液相间的速度差。相较于流动规律平稳的气相而言,研究不稳定的气泡流动状态具有更高的技术难度。本文针对空气-水为工质的两相流中一项重要参数——气泡速度进行测量,引入基于互相关运算的电磁检测方法,通过提高系统激励频率得到较大的检测信号。实验设计了高频(1 MHz)电磁检测系统,选用垂直上升管道,并在管道的2个平行截面分别安装电磁传感器,每组传感器均包含一个激励线圈及一个接收线圈,对2组接收线圈上的相位信号进行互相关运算,从而求得气泡的速度。实验中,对3种不同速度气泡采集到的信号进行了对比分析,相对误差控制在10%以内,提供了一种完全非接触非侵入的测量气泡速度的方法。此方法可以进行后续补充完善,用于其他工业场合,如金属液中气泡参数的测量等。

Measurement of bubble velocity in air-liquid two-phase flow based on electromagnetic technique and cross correlation

Air-liquid two-phase flow is a common flow pattern in industrial area. The relative velocity be-tween the gas phase and the liquid phase in air-liquid two-phase flow should be considered for the two-phase flow. Technically,it is more challenging to study the instability of bubbles than regular and steady gas phase. A novel method combining electromagnetic test and cross correlation has been carried out in order to determine the bubble velocity in the air-water flow in vertical upward pipe. Higher excitation frequencies have better re-ceiving signals. The high-frequency (>1 MHz)electromagnetic testing system was designed and two groups of electromagnetic sensors were installed in two parallel sections of the vertical upward pipe,each of which in-cluded an excitation coil and a receiving coil. Experimental results were collected and by cross-correlation al-gorithm,the bubble velocity could be calculated by the time difference of the phase signals on two receiving coils. Three kinds of bubbles with different velocities were distinguished in the experiment. Relative errors of the experimental results were controlled within 10%. The technique which is simple,effective,non-contact and non-invasive provides a new approach for the measurement of bubble velocity in two-phase flow. This method can be improved afterwards for other industrial applications,e. g. bubble parameter measurement in metal liquid.