Development of ultrasonic tomography system for liquid/gas flow measurement in a vertical column
Liquid/gas two-phase flow widely exists in many applications including chemical and petroleum industries. Measurement of this two-phase flow is an essential parameter for these applications where accurate flow measurement is required. Two-phase flow, a phenomenon of critical importance to oil and...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
Universiti Malaysia Perlis (UniMAP)
2014
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| Subjects: | |
| Online Access: | http://dspace.unimap.edu.my:80/dspace/handle/123456789/31920 |
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| Summary: | Liquid/gas two-phase flow widely exists in many applications including chemical and
petroleum industries. Measurement of this two-phase flow is an essential parameter for
these applications where accurate flow measurement is required. Two-phase flow, a
phenomenon of critical importance to oil and gas sector where compared with singlephase flow, its flow characteristic is much more complex. Thus, the improvement of the instrumentation and measurement technology for the two-phase flow such as the
development of two-phase flowmeters will have a growing demand since it will bring
significant benefits to many industries. Based on the advantage of tomographic imaging
technique, non-invasive ultrasonic sensing technique is realized by using electronic
measurement circuits for transmitting and receiving the analog signals, data acquisition
system for transferring the data to the PC and most importantly the suitable image
reconstruction algorithm for providing visual access to the two-phase liquid/gas flow
and estimating the component distribution for real-time measurement. The important
characteristic for sensor selection is noted and balanced between high operating
frequency for increased spatial sensitivity and the cross-sectional area of the vertical
column to avoid undetected measurement signal caused by complete attenuation. The
enhancement of liquid and gas component distribution imaging over the common Linear Back Projection (LBP) algorithm has been successful by implementing the new Eminent Pixel Reconstruction (EPR) algorithm. Simulative study on liquid/gas two-phase velocity measurement for dual-plane ultrasonic tomography system also has been made.
Two different methods based on the use of cross-correlation technique have shown the
usability of the technique for estimating the flow velocity. The image reconstructions
quality of the two-phase flow is seen to have a significant increase by combining the
EPR algorithm with Median Filtering technique that eliminated pixel values which are
unrepresentative of their surroundings. Another advantage of such combination is the
smoothen effect on the reconstructed images, resulting in better visualization of the twophase liquid and components because the outcome have approximating shape and size
if compared with the actual flow condition. Linear regression method are also
introduced for configuring the appropriate threshold values for imaging different size of
gas component inside the investigated column especially on the successful detection of
small gas bubbles. The results obtained can be useful for the online monitoring of
liquid/gas flow in many industrial processes such as chemical mixing process, fluid
transportation or process monitoring. |
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