Oil Filled Flexural Ultrasonic Transducers for Resilience in Environments of Elevated Pressure

Somerset, William E.; Feeney, Andrew; Kang, Lei; Li, Z.; Dixon, Steve

doi:10.1109/ius52206.2021.9593697

Cited by 1 publication

(6 citation statements)

References 7 publications

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“…This again indicates that the vibrational responses of the OFFUTs are independent of orientation at atmospheric pressures, and therefore have negligible air bubble entrapment in the oil filled cavity. However, multiple signal frequencies can be observed in the A-scans of the OFFUTs, even after the shortcycle input, as observed in prior research [19]. This contrasts with the narrowband ringing in the original commercial FUT, which for this design is dominated by the (0,0) mode resonance only [11,13,17].…”

Section: Absorbing Boundarymentioning

confidence: 60%

“…This provides a reliable measurement environment for the investigation of the OFFUT's dynamic response at higher pressures. The reliability of this approach has been demonstrated in prior research [17,18,19].…”

Section: Absorbing Boundarymentioning

confidence: 86%

“…An alternative cap design to the VFUT that is hermetically sealed is required for ultrasonic measurements in high pressure fluid environments. A recent concept has been introduced, the oil filled FUT (OFFUT) [19], where the internal air cavity of a FUT is filled with oil that is effectively incompressible. As external pressure is increased, the pressure difference across the membrane is minimized as the membrane undergoes small deformations that compress the liquid in the FUT to a pressure level close to the external pressure.…”

Section: B Pressure Balancing a Fut Membranementioning

confidence: 99%

“…4. The acoustic microphone is not suited to measurement at elevated pressure levels, but the mitigation of disruptive interference inside the pressure chamber must be ensured [19]. An acoustic microphone, and the lining of reflective walls within the pressure vessel with acoustically absorbent material, is key to achieving this objective.…”

Section: B the Dynamic Characterisation Processmentioning

confidence: 99%

“…Baffles are 3D printed from ABS for the OFFUTs, so that they can be securely positioned inside the pressure chamber. Prior research has shown that small variations in the dimensions and clamping of flexural transducers can influence the position of their series resonance [19], but here the OFFUT pair are fabricated using identical methods and hence should possess similar resonance frequencies, making them suitable for this measurement. The response of the OFFUT pair at elevated pressure levels is investigated, with both transducers within the stainless steel pressure chamber of internal volume 2.2 L. The pressure level is controlled through an air compressor (300 bar PCP compressor, IYS), measured by a ratiometric pressure sensor (MLH Series, Honeywell) within the chamber.…”

Section: B the Dynamic Characterisation Processmentioning

confidence: 99%

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Design and Dynamics of Oil Filled Flexural Ultrasonic Transducers for Elevated Pressures

et al. 2022

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The flexural ultrasonic transducer has traditionally been limited to proximity measurement applications, such as car-parking systems and industrial metrology. Principally, their classical form is unsuitable for environments above atmospheric 1 bar pressure, due to an internal air cavity which creates a pressure imbalance across the transducer's vibrating membrane. This imbalance leads to physical deformation and degradation of the transducer's structure, restricting the membrane's capacity to vibrate at resonance to transmit and receive ultrasound. There is a requirement for ultrasonic sensors which can withstand environments of elevated pressure, for example in ultrasonic gas metering. Recent research demonstrated the dynamic performance of flexural ultrasonic transducers with vented structures, allowing the pressure to balance across the transducer membrane. However, a hermetically sealed transducer is a more practical and robust solution, where the internal components of the transducer, such as the piezoelectric ceramic disc, will be protected from harmful environmental fluids. In this research, the design and fabrication of a new form of flexural ultrasonic transducer for environments of elevated pressure is demonstrated, where the internal air cavity is filled with an incompressible fluid in the form of a non-volatile oil. Dynamic performance is measured through acoustic microphone measurements, electrical impedance analysis, and pulse-echo ultrasound measurement. Together with finite element analysis, stable ultrasound measurement is achieved above 200 bar in air, opening the possibility for reliable ultrasound measurement in hostile environments of elevated pressure.

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