Applications Of Wavelet Analysis To The Measurement Of Two-Phase Flow

The two-phase flow system is a complex, nonlinear and dynamic system. There are interface effect and relative velocity between the two phases, so the measurement of two-phase flow is more difficult. In the parameter measurement technique of the two-phase flow, the identification of the flow regimes (patterns) is one of most important research fields. Heat transfer, mass transfer and the measurement accuracy of other flow parameters depend on the flow regimes.In this thesis, the author applies the wavelet analysis, ECT, multisensor information fusion and fuzzy technology to the identification of the flow regimes of gas-solid fluidized bed and gas-liquid two-phase flow. The experimental results on the self-designed equipment of gas-solid fluidized bed and gas-liquid two-phase flow show that the presented methods are effective. The main works are written as the following: A new method of the application of wavelet analysis to the identification of the flow regimes of gas-solid fluidized bed is proposed, and the eigenvalues used in identification of flow regimes are constructed. In different flow regimes of gas-solid fluidized bed, the decomposed signals of the pressure fluctuation signal have obvious differences. The eigenvalues of 'scale energy percent' are obtained to identify the flow regimes of fixed bed and bubbling bed of gas-solid fluidized bed, and the rules of identification are also established. The experimental results show that the method is effective. The electrical capacitance tomography(ECT for short) system is successfully applied to the identification of flow regimes of gas-solid fluidized bed by the voidage measurement of gas-solid fluidized bed, and a new combinatorial image reconstruction algorithm which combines Tikhonov regularization theory with ART (Algebraic Reconstruction Techniques) algorithm is presented to implement the global voidage measurement of gas-solid fluidized bed. The use of Tikhonov regularization theory is to solve the ill-posed problem of image reconstruction and the use of ART algorithm is to improve the quality of the final reconstructed image that determines the precision of the voidage measurement. For improving the accuracy of identification of regimes of gas-solid fluidized bed, the multisensor information fusion technique is introduced. In the dissertation, the pressure transducer and the ECT transducer are applied to provide the different signals-pressure fluctuation signal and voltage fluctuation signal. Based on the results of the identification of flow regimes using wavelet decomposition of pressure fluctuation signal and voidage fluctuation signal, using the D-S evidence theory of information fusion, the author identifies the flow regimes of fixed bed, bubbling bed and turbulent bed successfully, and the results show that the method is effective. The accuracies of identification of fixed bed, bubbling bed and turbulent bed have improved to 95%, 90% and 85% respectively. In gas-liquid two phase flow system, the model of soft-sensoring technique is constructed: regarding the differential pressure fluctuation signal as the secondary variable and combining the wavelet analysis and fuzzy identification technique, the primary variable of flow regimes of gas-water two-phase flow is measured. An identification method applied to the gas-water two-phase flow with different pipe diameter is presented. The results show that the method is effective. The wavelet analysis is used in oil-flied two-phase flow system primarily. In the large-diameter upright pipe of Institute of Oil Logging of Daqing Oil Field, the wavelet analysis of differential pressure fluctuation signals along the pipe shows that the wavelet analysis can be used to identify the regime of the upright gas-water two phase flow and the deep research will continue.