Resistance And Ultrasonic Dual-modality Measurement For Gas-oil-water Multi-phase Flow

Process Tomography, which is capable of obtaining two-dimensional orthree-dimensional distribution of information describing the measured area withspace-sensitive electrode array, is widely used in two-phase/multi-phase flowmeasurements. Electrical Resistance Tomography (ERT) and Ultrasonic Tomographyare two different modalities with advantages of non-perturb and high-response. Theyboth have huge prospects on multi-phase measurements for their low-cost, small-sizeand non-radiation sensors. They have different scope of applications and variety ofimage principle, while complementary sensing field. For enhancing measurementprecision and broaden the range of applications, a combination of electrical andultrasonic dual-modality system was proposed. The main work and results are asfollows:1. Adopted ultrasonic transmission method as the complementary modality ofERT to design dual-modality system. Ultrasound was sensitive to gas-liquid interface,transmission method can obtain the gas-liquid interface and approximate distributionof the bubbles, which can be used as priori information of ERT. What’s more, as twodifferent measurement modalities, their sensor information, sensitive field distribution,data structure and spatial resolution are highly complementary;2. A data acquisition platform for multi-phase flow measurement with strongexpansibility and high stability was developed on the basis of Compact PCI bus andadoption of FPGA. The platform can meet data acquisition needs for a variety ofsensor modalities, and also had good compatibility and scalability. High-speed andstable data transmission was conducted due to the DMA mode with the feature of norelying on CPU based on Compact PCI bus. The improvement of flexibility andreal-time performance was obtained for the design of control logic and parallelhigh-performance data processing modules by FPGA;3. On the platform above, a parallel dual-cross ERT system was designed anddeveloped digitally. The acquisition speed and precision were greatly improved, over1042frames/s data acquisition speed, more than60dB channel SNR and less than0.7%frame measurement deviation. Dedicated user-friendly software also has been developed with function of data acquisition, image reconstruction and flowinformation extraction for on-line and off-line data processing. The calibration resultsshowed great precision with error less than5.6%for single object and good resolutionfor multiple objects. Preliminary dynamic experiments have been done in a horizontalpipeline, and the estimated volume fraction was very good with error less than6%under the flow rate less than3m3/h;4. Based on the ultrasonic transmission method, there exists relations betweenvoltage loss and bubble diameter due to the near total reflection of ultrasonic wave atthe liquid/gas interfaces. One-transmitter-three-receiver narrow band ultrasonicmeasurement system with16transducers was designed for gas-oil-water multi-phaseflow in horizontal pipeline with inner diameter of50mm. The calibration experimentswere conducted using1MHz ultrasonic transducer. And the results showed themethod had good resolution with minimum resolvable diameter of1.5mm.