Research On The Parameter Measurement Of The Gas-Liquid Two-Phase Flow Based On The Fluctuation

Two-phase flow widely exists in processes such as power, chemical, petrol, metallurgy, pipeline transport, medical and refrigeration industries. Researches on hydrodynamics, mechanisms and accurate detection of parameters in two-phase flow are very important for the development of modern industrial equipments. These subjects have already been the frontier subjects in the world. The measurement of two-phase flow is difficult, owing to the complex of the characteristic of two-phase flow. The two-phase flow measurement technique has been one of the bottlenecks in the research field of the two-phase flow.Based on theoretical analysis of the fluctuation in the process of the two-phase flow, the fluctuation coefficient of two-phase flow was proposed, and fatherly the fluctuation coefficient is applied in the identification of the gas-liquid two-phase flow patterns and measurements of parameters (such as flowrate, the void fraction, etc.). The main innovation is summarized as follows:(1) The fluctuation coefficient was presented and the influencing factor of the fluctuation coefficient was investigated. The process of two-phase flow was analyzed. The fluctuation coefficient was deduced from the energy conservation equation. The effects of the void fraction, flowrate and tube diameter on the fluctuation coefficient were analyzed. The experimental results show that the fluctuation coefficient could indicate the state of two-phase flow. The fluctuation coefficient provides a new method for the parameter measurement for two-phase flow.(2) A new flow pattern identification method was put forward based on the fluctuation of the two-phase flow. The fluctuation coefficients of the two-phase flow were calculated. The effects of two-phase flow patterns on the fluctuation coefficient were analyzed. The relationship among the fluctuation coefficient, R and the flow pattern was analyzed. The experimental results show that the method could properly identify the bubble flow, slug flow, plug flow, annular flow and stratified flow. Moreover the transition states of flow patterns were described by the fluctuation coefficient and R.(3) The measurement method of the two-phase flowrate based on flow patterns was put forward and the relation of the fluctuation coefficient and measurement accuracy is analyzed. Based on the analysis of the dynamic differential pressure signal of two-phase flow through Venturi tube, the various flowrate equations were established according to the flow pattern. The experimental results show that the method is feasible: the mean of relative error decreased from 10% to 5.7%, and the mean square-root of relative error decreased from 20% to 4.2%.Moreover, the parameter-measurement accuracy could be denoted by the fluctuation coefficient. The smaller the fluctuation coefficient is, the higher the measurement accuracy is. (4) The measurement method of the parameters of two-phase flow by the loop tube was proposed. The state of two-phase flow with loop tube was analyzed. The relationship equations of the differential pressure on the flowrate and the volume fraction were established, thus the parameters of two-phase flow were measured. Experimental results indicate that the involvement of the fluctuation coefficient in the result modification is effective to reduce the estimation error. The mean absolute error of volume void fraction was 1.2%; the root mean square error was 1.6%, which shows the method of the parameter measurement is feasible under present experimental conditions.