Research On Information Transmission Technology Based On Pressure Wave

Since the requirement of electronic, cyber and communication technology, various wireless transmission technology adapted with special environments are well developed, where pressure wave information transmission technology is one of the favorite method because of its capacity of resisting disturbance, low cost and long transmission distance. Nowadays, pressure wave transmission is used to not only bi-directional communication between surface and downhole of the oil well but also the information transmission in pipeline under the special environments. Oversea company blocks the pressure wave technology to seek high yield by providing field service, and some Chinese research institutes began to research pressure wave transmission but still have big technology gap with oversea company. Therefore, it has great significance to develop the pressure wave information transmission technology.In this thesis, based on existing theory about the mechanism of drilling fluid transmission systems, the one dimensional differential motion equations and continuous equations of fluid were introduced, and transmission characteristic of pressure wave signals were deduced by solving the fluid equations. The attenuation of transmission signal was analyzed based on the theoretical model of transmission characteristic which was built by using fluid dynamics and non-Newtonian fluid mechanics. Matlab was used to analyze how the signal strength are affected during the transmission process.Based on the transmission characteristic theory, a pressure wave transmission system including hardware and software was designed in this thesis. The system includes information sending module, information receiving module and the PC software module, which can denoise the original pressure wave data with noise by LabVIEW and Matlab mixed programming method. By using digital signal processing technology, to remove the actual signal noise signal and decode real data. To verify the feasibility of designed pressure wave information transmission system, a hydraulic pressure cycle control system experimental platform was built based on the original equipment and pipeline of oil-gas gathering and transportation control system.From experimental testing, the system designed in this thesis, which can realize coding, data filtering and decoding of pressure wave information, was verified feasible. Experimental research was done to analyze how the signal frequency and void fraction of liquid in the pipeline affect the reliability of pressure wave transmission. The test results shown that the designed system can satisfied the application requirement and can provide theoretical foundation and experimental support of pressure wave transmission system design, pressure wave signal coding and decoding and pressure wave information detection and recognition.