Study On New Measurement Methods Of Two-phase Flow Parameters Based On Data Mining

Parameter measurement of two-phase flow has been an urgent and difficult task in the world for a long time.However,it has not been solved satisfactorily up to now.Data mining technique is currently a hot spot in the research field of information science.Based on data mining techniques such as Principle Component Analysis(PCA)/ Principle Component Regression(PCR),Partial Least Squares(PLS)/Partial Least Squares Regression(PLSR) and Least Squares Support Vector Machine(LS-SVM),this dissertation studies the flow pattern identification and the voidage measurement methods of gas-liquid two-phase flow and the parameter measurement method of liquid-liquid two-phase flow.The main innovative points and contributions of this dissertation are listed as follows:1.Based on the ECT capacitance sensor array and data mining techniques,three new methods are proposed and compared for the flow pattern identification of oil-gas two-phase flow:1) flow pattern identification method based on LS-SVM,2) flow pattern identification method based on PCA and LS-SVM,3) flow pattern identification method based on PLS and LS-SVM.Research results show that these three proposed methods are all effective and the method based on PLS and LS-SVM has the highest flow pattern identification accuracy. Compared with other flow pattern identification methods,the method based on PLS and LS-SVM has the advantages of relatively high accuracy and good real-time performance.2.Based on the ECT capacitance sensor array and data mining techniques,a new method is proposed for the voidage measurement of oil-gas two-phase flow.Voidage measurement models are established in advance for each typical flow pattern of oil-gas two-phase flow in horizontal pipe.In the practical measurement process,the flow pattern of oil-gas two-phase flow is firstly identified according to the method based on PLS and LS-SVM.Then,the suitable voidage measurement model is selected by using the flow pattern identification result to calculate the voidage value.The voidage measurement models are established based on data mining techniques.Three kinds of modeling methods are studied and compared:1) Modeling methods based on linear regression(PCR and PLSR),2) Modeling methods based on non-linear regression(LS-SVM),3) Modeling methods based on feature extraction(PCA or PLS) and LS-SVM.Research results show that the proposed method is effective.Without any image reconstruction process,it directly uses the measured capacitance values to implement the voidage measurement and can overcome the influence of flow pattern on the voidage measurement.Research results also indicate that among all the established voidage measurement models,the PLS and LS-SVM based models shows the best measurement performance.Compared with the other voidage measurement methods based on ECT or data mining,if the PLS and LS-SVM based model is adopted,the proposed voidage measurement method has the advantages of high accuracy and good real-time performance and its maximum voidage measurement error is less than 3.6%.3.With the 16-electrode ERT conductivity sensor array,the measurement principle of hybrid flowmeter and data mining techniques,a new method is proposed for the parameter measurement of liquid-liquid two-phase flow.To overcome the influence of oil fraction on the measurement results,a dominant phase identifier is developed based on the conductivity values obtained by the conductivity sensor array and data mining techniques(PLS and LS-SVM).The hybrid flowmeter consists of a Venturi meter and an oval gear flowmeter.In the practical measurement process,the differential pressure and the total volume flowrate of two-phase flow are firstly obtained by the Venturi meter and the oval gear flowmeter. Meanwhile,the phase that dominates the global characteristics of the oil-water two-phase flow is identified by the dominant phase identifier.Then,the meter coefficient of the Venturi meter is selected according to the domiant phase identification result.Finally,the total volume flowrate,the density and the the total mass flowrate of the oil-water two-phase flow are calculated.Research results show that the proposed oil-water two-phase flow measurement method is effective.The maximum measurement error of the total volume flowrate,the density and the the total mass flowrate of the oil-water two-phase flow are 1.0%,4.6%and 4.5%,respectively.Additionally,the proposed method is low-cost and easy to be implemented.