Permanent contact mode operation of air-coupled capacitive micromachined ultrasonic transducers (CMUTs) for wide pressure range application
Abstract/Contents
- Abstract
- Flare gas stacks are widely used to burn off raw natural gas as waste in oil production facilities. In areas without proper gas transportation infrastructure, collecting the natural gas for sale can be even more costly than flaring it off. About 150 billion cubic meter of natural gas is flared annually worldwide, which is equal to 25% of the US gas consumption and contributes to about 400 million tons of carbon dioxide emission each year. In recent year, therefore, it is not surprising that regulatory agencies require the oil producers to report flare emissions, and effective regulation of gas flaring relies heavily on accurate measurement. The focus of this research is to provide ultrasonic transducers for flare gas metering, with a targeted pressure range of 1 - 20 atm and temperature up to 300 degree C. Piezoelectric transducers are not a good candidate due to their limited Curie temperature. In order to operate CMUTs over a wide and varying pressure range without suffering from drastic changes in static operational point and operational frequency, we proposed a new operation mode, in which the plate is in permanent contact with the bottom of the cavity, even at zero dc bias and 1 atm pressure. This dissertation describes the design, finite element simulation, the fabrication, and characterization results for the CMUTs in permanent contact mode. Finite element analysis predicts the behavior of these CMUTs very well, and provides design guidelines that are useful in determining the device dimensions to fabricate. Improvements in device design and fabrication processes are also implemented in a second fabrication to increase the mechanical strength of the devices, and pitch-catch measurements with good SNR are demonstrated with these CMUTs up to 20 atm. This dissertation also presents the experimental results, including the charging method and charge storage long-term (29 months) stability, for pre-charged CMUTs for dc-bias-free operation.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2014 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Ho, Min-Chieh |
|---|---|
| Associated with | Stanford University, Department of Electrical Engineering. |
| Primary advisor | Khuri-Yakub, Butrus T, 1948- |
| Thesis advisor | Khuri-Yakub, Butrus T, 1948- |
| Thesis advisor | Howe, Roger Thomas |
| Thesis advisor | Solgaard, Olav |
| Advisor | Howe, Roger Thomas |
| Advisor | Solgaard, Olav |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Min-Chieh Ho. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2014. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2014 by Min-Chieh Ho
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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