Applications Of Electrical Conductivity Measurement Technique In Two-phase Flow Measurement

Electrical conductivity measurement technique and its application are studied in this dissertation. Being of the advantages of high sensitivity, wide measurement range, simple hardware structure and convenience to realize continuous measurement, electrical conductivity measurement technique has been approved valuable to two-phase flow/multiphase flow parameters measurement.A conductivity measurement system is developed and applied to oil-water two-phase flow. A large number of experiments prove that the system is valid and that identifying the dominant phase of oil-water two-phase flow using electrical conductivity signals is feasible.The main works are listed as follows:(1) A conductivity measurement system was developed. The system uses a high-frequency sine wave current source as its exciter, which effectively eliminates polarization effects. As high-speed A/D peak sampling technique is introduced into the system, the filter in the analog demodulation is avoided, measuring speed is improved and the structure of system is simplified. Compared with current systems employing high-speed A/D sampling technique, this system features a configuration consisting of a parallel sample-and-hold amplifier array and a single high-speed A/D device, which effectively reduces the cost;(2) A multi-class classifier of least squares support vector machine used for oil-water two-phase flow dominant-phase-identification was constructed. The classifier is applied to identify the dominant phase of the oil-water two-phase flow using the distributed conductivity signals acquired by the conductivity measurement system. The experiment results show that the classifier is valid;(3) Based on the conductivity measurement system and the multi-class classifier, a oil-water two-phase flow dominant-phase-identifying system was developed, and dominant-phase-identifying experiments were designed. Under different industrial situations, numbers of experiments were conducted. Using online data and the multi-class classifier of least squares support vector machine, the dominant phase of oil-water two-phase flow was identified successfully. At present, the technique of two-phase flow/multiphase parameters measurement based on electrical conductivity signals is mainly limited to flows with continuous conductive mediums, but this dissertation tries to make use of conductivity signals in oil-water two-phase.