Fraction Measurement Model for Gas-liquid Two-phase Flow Using Ultrasonic Method

The phase fraction measurement for stratified wavy gas-liquid two-phase flow is influenced by random ultrasonic reflection, and the utilization of ultrasonic measurement information is limited, which result in measurement inaccuracy of phase fraction. Aiming at the above problems, a modified model of gas-liquid interface height with ultrasonic pressure reflection coefficient is proposed based on the pulse-echo principle. To begin with, according to the assumption that the gas-liquid interface height distribution follows the Gaussian distribution, the wavy gas-liquid interface is regarded as a rough interface, and the statistical characteristics of gas-liquid interface are extracted by numerical simulation. In addition, considering effects of the gas-liquid interface inclination angle on time-of-flight (TOF) measurement, a modified model of gas-liquid interface height is established based on the Kirchhoff approximation method. Furthermore, the Levenberg Marquardt (L-M) algorithm is adopted to optimize the undetermined parameters in the model. The gas fraction test results show that MRE, RMSE and R2 are 0.245%, 0.291 % and 0.959 respectively. In conclusion, compared with the existing model, the effect of interfacial waves on gas-liquid interface height measurement is reduced in the modified model of gas fraction measurement, which improves measurement accuracy of gas fraction in gas-liquid two-phase flow.