Study Of Cross-Correlation Flow Measurement Technique Based On Annular Capacitor

With the rapid development of science and technology, Multiphase flow has occupied very important part in country economy and human life. The Parameters measurement of multiphase flow has became a question of first importance in the research field of multiphase flow. Flow measurement is a very important part in this subject.Multiphase flow measurement system based on cross-correlation flow measurement technique has been developed since the middle of 1960s, offering effective technology methods for multiphase flow measurement. With the appearance of digital signal processor (DSP), the calculation of correlation functions is greatly speeded up, which makes on-line multiphase measurement possible. Based on the study of flow measurement sensors and methods commonly used both at home and abroad, cross-correlation flow measurement technique based on annular capacitor was studied. The main work of the thesis is as follows:First of all, through the research on the principle of cross-correlation flow measurement, a new type of internal and external annular capacitor sensor for cross-correlation flow measurement and the design of Intelligence micro-capacitance measuring circuit were presented. The part of the signal detection circuit design was completed, also a processing of signal programmable amplify was conducted. Abstracting, detecting and analyzing of flow noise signal based on the capacitor sensor in field were realized.Secondly, through the study of fast correlation algorithm based on FFT, a digital correlator with high sampling frequency and computational capabilities was designed and implemented. According to the double-core technique (MCU+DSP), the system's capacities of operation and control are enhanced greatly. Simultaneously, the calculated results were output.Because the pseudo-random code has fine double value auto-correlation characteristics, whose correlation functions like impulse functions. That makes correlation identification easy. Through the study of pseudo random sequence knowledge, a dual channel pseudorandom signal generator was designed. When calibrate the digital correlator, an ideal result has been achieved. Finally, some questions in the process of the system's development were concluded and future research prospect were given.