Measurement Of Flow Parameter In Gas-liquid Two-phase Annular Flow Based On Near-infrared (NIR) Technique

The gas-liquid two-phase annular flow is one of the most important and typical flow patterns in engineering field,which widely exists in the fields of natural gas pipeline transport,nuclear reactor cooling,evaporation and condensation.The accurate measurement,analysis and prediction for the characteristic parameters play an important role in the energy measurement of the oil and gas production process,and the safety and reliable operation in the cooling and heating system.In the paper,the experimental measurement technology and the predictive correlations are carried out for the characteristic parameters of gas-liquid two-phase annular flow.The main research contents and innovative results are listed as follows:1.Based on the analysis of the existing experimental testing technology,the process analysis technology（PAT）of near infrared（NIR）is introduced into the two-phase flow measurement.According to the absorption characteristics band of O-H key,the peak wavelength of the double frequency absorption band is selected as the wavelength of near-infrared light.The sensor,for the interfacial wave parameters measurement,is designed based on NIR spectrum technology.According to the NIR spectral absorption principle,power spectrum for frequency measurement,the cross-correlation algorithm for velocity measurement,the measurement of liquid film thickness and interfacial wave characteristics are achieved.Moreover,a direct liquid film thickness sensor is designed based on the conductance probe,and the calculation method of duty ratio weight and the compensation calculation method of system error are presented,which improve the measurement accuracy obviously and realize the dynamic calibration for the liquid film thickness sensor.2.Aiming at the higher operating pressure in industrial field,the interfacial wave velocity measurements are available for 154 flow conditions under five system pressures（0.2～0.9MPa）.The data have been utilized to evaluate and analyze the four classical disturbance wave velocity predictive models.By introducing the parameters,e.g.the density increasing of gas core caused by entrained droplet and the relative velocities of gas core and liquid film surface,the parametric structure()is optimized reasonably,and the modified disturbance wave velocity model of vertical tube is proposed.Test results indicate that the mean absolute error（MAE）of the modified correlation is 5.37%for the current data and the relative deviations are within±10%for all the data.3.Utilizing the linearized stability equation,the effect of interfacial shear stress on the interfacial wave stability is analyzed.Air-water annular flow experiments have been conducted at five pressure conditions（from 0.3MPa to 0.9MPa）in a stainless steel tubular test section.A comparison of the performance of six existing predictive correlations based on experimental dataset mentioned above is made.The paper analyzes the effect of system pressure on interfacial disturbance wave velocity systematically.Through introducing the nondimensional parameters e.g.the pressure ratio and pipe diameter ratio,an improved horizontal disturbance wave velocity correlation is proposed based on the interfacial shear model,which could acceptably handle the data of different system pressures and pipe diameter.Experimental results indicate that the MAE is 2.72%with 90%relative deviations within±10%for all the data.4.Based on the NIR spectrum technique,a non-invasive sensor is designed for the void fraction measurement.Considering the effects of liquid film absorption,entrained droplets scattering and two-phase interfacial reflection,a void fraction model is constructed and further simplified.Laboratory results indicate that the range of relative deviations is from-5.53%to 7.34%,and the 93.75%of relative deviations are within±5%.