| Two-phase flow has a wide range of application in industry. The research on two-phase flow is developed rapidly. The subject on two-phase flow has been one of the frontier subjects concerned deeply in the world. Two-phase flow system is a complex, nonlinear and dynamic system. There are interface effect and relative velocity between these two phases. Real-time and accurate measuring of two-phase flow parameters is needed very urgent, however it can not be solved well until now.Electrical resistance tomography (ERT) is a kind of process tomography techniques which are widely studied. It is suitable for the two-phase flow whose continuous phase is conductive. By detecting conductance changes in the object field, ERT can acquire the information of object field and reconstruct the image of conductance distribution. ERT has several advantages over other traditional process-parameter-measurement techniques, such as non-invasion, fast-responding, low-cost and non-radiation. ERT can provide 2D/3D visualization information of the multi-phase inside a close process pipe or vessel. So it has great potential for production process and environment monitoring.This dissertation researches on some difficult and key problems being of ERT and proceeds deeply theory analysis and experiment researches deeply, all this is based on the research of the principle of ERT and its application in visualization of two-phase flow. A new high-speed ERT experiment system based on the Bi-directional Current Pulse Technique is designed and developed. On-line observation is realized for simulating gas/liquid two-phase flow using this experiment system.The main works are listed as follows:(1) Based on the excitation of Bi-directional Current Pulse Technique, a new measuring circuit for weak variation of resistance was proposed for electrical resistance tomography. Traditional AC current source isn't adopted as the exciting source. Through fast bi-directional current switching, the polarization effects are eliminated. As the system is regarded as being excited by a constant direct current at the data acquisition point, no complex AC circuit such as filter is required. It can improved the rate of data acquisition and simplify the circuitry of ERT system.(2) Some optimization methods such as differential measurement, isolation are also introduced into this new system. For further improving the data-acquiring rate, parallel-sampling and serial-measurement are combined in this system. It also reduces the cost.(3) An ERT experiment system is developed base on the new resistance measuring circuit. This system is entirely designed as a field-bus instrument. Instructions are sent from the PC to execute some work such as parameter configuration, fault-checking and data-acquiring.(4) A high-speed communication module for ERT was introduced in this system. The advantages of this communication module are RS422/RS232 compatibility, high band rate of 921.6Kbps, noise-immunity and low cost. The module was successfully used in electrical resistance tomography.(5) Three ERT reconstruction algorithms are analyzed and compared by the simulation gas/liquid two-phase flow experiment data. Their name is the sensitivity coefficient algorithm, the combination algorithm of Tikhonov regularization and Algebraic Reconstruction Technique(ART) and the Modified BFGS (MBFGS)algorithm. Their advantages and disadvantages are discussed respectively.(6) The real-time imaging is realized using the sensitivity coefficient algorithm and Modified BFGS (MBFGS)algorithm. The corresponding speed of real-time imaging can reach 26 frames per second and 10 frames per second. A lot of experiments are made with this system to observe flow regimes of gas/liquid two-phase flow.
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