Research On Ultrasonic Flow Signal Acquisition And Processing

In the industry of oil energy, quantitative measurement and analysis on productionparameters, such as produced fluid volume, etc., are required. A flow measurement technologybased on ultrasonic, which is both non-contacted and easily installed, has been applied in oilproduction field at present. But considering the particularity of the measured liquid, whichcontains not only the thick oil, but sand, water, even mud, bubbles, etc., it becomes especiallyimportant to find a method that can accurately measure flow of fluid with many impurities.In this paper, the key technologies that can greatly improve the overall performance of thedoppler ultrasonic flow measurement system, are academically lucubrated. Related researcheson ultrasonic transducer and velocity distribution of pipe flow are first discussed, whichprovide theoretical supports for the following circuit design. Reflection, refraction and waveconversion rules of ultrasonic wave in different medium interface are researched and exploited.Incidence angle of the transducer in the experiment is45°, ensuring measurment accuracy ofthe prototype.In hardware design, human-machine interaction module is added. Single chipmicrocomputer is adopted to achieve the real-time display of flow meter data, and parametersettings (such as pipe diameter, pipe number, etc).In signal processing, several kinds ofspectrum refinement algorithms are compared based on ultrasonic doppler echo signalcharacteristics. Multiple modulation refinement with spectrum analysis is adopted to improvethe frequency resolution by frequency refinement. In ultrasonic doppler flow measurementsystem, the measurement is achieved by detecting ultrasonic doppler frequency shift in fluidtransmission, but the value of the frequency offset changes over time. In this paper, Kalmanfiltering algorithm with recursive ability is realized to track peak of the frequency offset.Simulation analysis of this algorithm is conducted in MATLAB environment, the algorithm isalso implemented in a flow measurement system.In order to improve measurment accuracy of the prototype, it is analyzed temperature,velocity and density of the mixed fluid,which have influence on the measurement results ofultrasonic doppler flowmeter, and the results provide theoretical reference for the subsequentexperiment. Experiments and debuggings are conducted on the designed circuit, reliability andaccuracy of the designed flowmeter is tested. Under the existing laboratory conditions, a feasible experiment method is designed to calibrate the flowmeter, the measurement data isalso analyzed. The results show that the algorithm used to design the flow meter has goodstability and high measurement accuracy, the flow meter basically meets the industrial testdemand.