关键词: 气液两相流, 仪器仪表, 流速, 含率, 测量, 流型识别

Abstract:

Aiming at the gas-liquid two phase flow in horizontal pipeline, a comprehensive method for flow pattern identification and flow velocity and phase fraction measurement was proposed, using only a single conductance sensor. Firstly, a conductance sensor composed of six ring-shaped electrodes was adopted to acquire flow information about the water holdup and cross-correlation velocity of gas-liquid two phase flow under different flow conditions. Secondly, based on the signal fluctuation analysis, the flow characteristics of different flow patterns were revealed. The mean and variance of the time series of normalized voltage and the cross-correlation velocity were calculated as a feature vector for flow pattern representation. Using support vector machine (SVM) method which was suitable for small samples, 15 binary classifiers with radial basis function as kernel function were constructed by “one-to-one”strategy. The parameters of the identification model were optimized by cross validation method, and 6 flow patterns (stratified flow, wavy flow, bubbly flow, plug flow, slug flow and annular flow) were identified with the identification rate of 93.1%. Thirdly, based on the identification results, the measurement models for calculations of phase fraction and mean velocity through normalized voltage and cross-correlation velocity were established for every specific flow patterns. Compared with reference values at inlet, dynamic experiments showed that the root mean square errors (RMSE) of water fraction and gas fraction were 2.56% and 2.73%, and the RMSE of mean velocity was 0.69m/s. The proposed method provides a simple, efficient, low-cost, and non-invasive flow pattern identification and process parameter measurement strategy for gas-liquid two-phase flow, which has important scientific and engineering significance.

Key words: gas-liquid flow, instrumentation, velocity, fraction, measurement, flow pattern identification