Study On Parameters Measurement Of Gas-liquid Two-phase Flow Based On LS-SVM

Two-phase flow exists widely in many industrial fields such as power,petroleum, metallurgy, nuclear energy, chemical engineering and so on.Measurement of two-phase flow parameters is very important for the metrology,control and environment protection in modem production processes. However, the inherent complexity of two-phase flow system leads to many difficulties in measuring the parameters of two-phase flow. Voidage is one of the most important parameters. Although many voidage measurement methods have been proposed, it is still difficult to measure the voidage due to the complexity of the characteristics of two-phase flow. It is necessary to explore new methods for voidage measurement.The author mainly focuses on the research of voidage measurement of gas-liquid two-phase flow. The main works of the dissertation are listed as follows:1. An improved Least Squares Support Vector Machine (LS-SVM) was proposed to overcome the drawback existing in the present LS-SVM. According to the training errors of LS-SVM model, data points with too large or too small errors were discarded, and thus the generalization ability and robustness of LS-SVM model was improved. The improved LS-SVM was verified by simulation data.Experimental results of voidage measurements also demonstrate that the improvement of LS-SVM is effective.2. Real-Coded Genetic Algorithm (RC-GA) was introduced to solve the difficult problem of parameters selection in LS-SVM. The issue of parameters selection in LS-SVM was regarded as an optimization problem. A RC-GA with global searching capability was employed to search the optimal parameters in LS-SVM. Experimental results show that the RC-GA based parameters optimization method is effective.3. Based on Electrical Capacitance Tomography (ECT) and LS-SVM, a new method was proposed for on-line voidage measurement of oil-gas two-phase flow. LS-SVM was used to establish the voidage measurement models under different flow patterns. In the measurement process, the flow pattern of oil-gas two-phase flow was first identified, and then, the voidage was computed using the voidage model corresponding to the identified flow pattern. This new method implemented voidage measurement without complicated and time-consuming image reconstruction. And thus the real-time performance of voidage measurement was improved. Experimental results show that the new method is effective.4. Based on Electrical Resistance Tomography (ERT) technique and LS-SVM, a new voidage measurement method of gas-liquid two-phase flow was proposed. In this method, the ERT sensor was employed to obtain the 104 independent resistance values. These 104 measurements values (88 measurements after reducing dimension by eliminating 16 adjacent values) were the input of the voidage measurement model which was established by LS-SVM. The output of the model was the voidage. Experimental results prove the effectiveness of the new method.