关键词: 气液两相流, 段塞流, 持气率, 快关阀法

Abstract:

Quick closing valve (QCV) method is a common means of calibrating gas holdup in gas-liquid two-phase flow test. Unreasonable selections of spacing between valves and trapping times in QCV could bring about large error in gas holdup measurement, particularly since the gas slug and liquid slug in slug flow present flow characteristics with random variability. In this study, an optimal design was proposed for measuring gas holdup using QCV method. The cross-correlation velocity of gas-liquid two-phase slug flow was measured based on the signals between axially upstream and downstream probes. Then, the lengths of gas slug and liquid slug were extracted from the upstream probe signals under different flow conditions. Also, the gas holdup in liquid slugs was calculated by using Maxwell equation. On that basis, the gas holdup series was simulated at different spacing between valves based on the gas slug ratio in pipe. By analyzing the fluctuation of gas holdup series, the floor level of trapping times was indicated under the condition of 95% confidence coefficient and 5% permissible error at different spacing between valves. Finally, an experiment was conducted to assess the trapping times in QCV with the spacing setting at 1.55 m length. The measuring errors of gas holdup using QCV method was statistically analyzed, and it was proved that the design guideline provided a sufficient condition for setting up the spacing between valves.

Key words: gas-liquid two-phase flow, slug flow, gas holdup, QCV method