Next generation ultrasonic flow measurment
Supervisor: Professor Steve Dixon
This project will develop instrumentation and methods for generating ultrasonic waves in fluids
flowing in pipelines for the purpose of measuring flow rate, including the implementation of novel
approaches using flexural and low frequency transducers that have not been previously considered.
The use of ultrasound to measure flow velocity in pipes using a counter propagating transit time
difference is a well established technique. There is a broad range of applied physics that underpins
the design of the transducers used in these approaches, but there remains a number of technical
challenges.
The first stage of the project will be to develop a new gas flow rig, using a high power pump to drive
air through a suitably designed pipe run. We have been working with partners in an EU project who
have developed a similar system and so we are aware of the requirements.
The use of flexural transducers has not been investigated for use in industrial gas flow applications,
and has potential issues if the pressure inside the pipe is high. We are investigating ways to
compensate for this that will allow the flexing motion of the transducer to operate at high pressures.
We shall also investigate more conventional designs of ultrasonic transducer, that uses thickness or
radial modes of vibration of a piezoelectric element to generate ultrasound in a fluid. The physics of
the ultrasonic generation mechanism will be modelled using a number of analytical and numerical
approaches, that have already been published. The propagation of the ultrasonic waves through the
fluid and the structure containing the fluid will be modelled using finite element techniques and this
will then be experimentally validated.
The use of low frequency ultrasonic waves to measure flow has been shunned, mainly because there
is a conception that higher frequencies will give higher temporal resolution when waves are being
propagated against and with the flow direction. This is despite the fact that the waves themselves
will be travelling at the same speeds, with the same temporal shifts, regardless of the frequency of
the wave. One can understand why low frequency waves are often avoided when the conventional
methods for determining transit time are methods such as zero crossing or peak detection applied in
the time domain. More sophisticated methods such as a number of correlation techniques or phase
switching mid-pulse are likely to provide sufficient measurement accuracy. The ability to operate at
lower frequency could be a major game changer in many applications, and will enable
measurements at lower powers, through more attenuative media, using lower cost transducers.
This project will be performed in collaboration with an industrial partner, as part of a larger scale
research project designed to generate applied physics and engineering publication outputs in
addition to delivering impact. There may be an element of matched funding available for this project
through a Honeywell contract.