Instrumented flow-following sensor particles with magnetic position detection and buoyancy control
A concept for buoyancy control and magnetic position detection has been developed for the improvement of instrumented flow-following sensor particles. The sensor particles are used for investigation of hydrodynamic and biochemical processes in large-scale vessels such as biogas fermenters, bioreacto...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-06-01
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| Series: | Journal of Sensors and Sensor Systems |
| Online Access: | http://www.j-sens-sens-syst.net/5/213/2016/jsss-5-213-2016.pdf |
| Summary: | A concept for buoyancy control and magnetic position detection has been
developed for the improvement of instrumented flow-following sensor
particles. The sensor particles are used for investigation of hydrodynamic
and biochemical processes in large-scale vessels such as biogas fermenters,
bioreactors and aerated sludge basins. Neutral buoyancy of the sensor
particles is required for tracing of the fluid flows. Buoyancy control is
performed by adjustment of the sensor particles' volume, which is altered by an
integrated piston. A miniaturized linear actuator, namely a stepper motor
with linear transmission, is operated by a microcontroller to drive the
piston. The buoyancy control unit enables accurate automated taring of the
sensor particles in the stagnant process fluid to achieve neutral buoyancy.
Therefore, the measured vertical position of the sensor particle as a function
of the hydrostatic pressure is used as feedback. It has an incremental
density change of 0.0136 % as compared to water and a residual drift velocity
of approximately 3.6 × 10<sup>−3</sup> m s<sup>−1</sup>. Furthermore, a minimum density of
926 kg m<sup>−3</sup> can be set by full extension of the piston, which
allows floating of the sensor particles after a defined event, namely
critical charge of battery, full data storage or the end of a fixed time cycle.
Thus, recovery of the sensor particles can proceed easily from the fluid
level. The sensor particles with a buoyancy control unit are tested for depths
up to 15 m. Also, detection of a local magnetic position marker by the sensor
particles has been implemented to enhance movement tracking. It was tested in
a lab-scale biogas digester and was used for estimation of the liquid
circulation time distribution and Peclét number to describe the
macro-flow. |
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| ISSN: | 2194-8771 2194-878X |