Genauigkeit der Bestimmung von Blasengrößen aus Messdaten eines Leitfähigkeits‐Gittersensors

Abstract

In experimentellen Versuchen wurde die Genauigkeit eines Leitfähigkeits‐Gittersensors mit einer zeitlichen und räumlichen Auflösung von 5 kHz und 4,8 mm in Bezug auf die Bestimmung von Blasengrößen untersucht. Als Referenzwert werden einzelne Luftblasen definierten Gasvolumens im Größenbereich von 2 – 12 mm in eine ruhende Flüssigkeit aufgegeben. Die Ergebnisse zeigen eine erhöhte Messunsicherheit für Blasen, deren Durchmesser kleiner als die Auflösung des Gitternetzes ist. Die ermittelte Blasengröße hängt in diesem Fall stark von der örtlichen Position der aufsteigenden Gasblasen im Gitternetz ab.

Prediction of Bubble Sizes in Bubble Columns with Machine Learning Methods

“…The experimental data for the study presented here are taken from [3]; details of the experimental setup are provided in [8]. In [3] single bubbles were injected manually with syringes into a hemisphere which was placed within the bubble column (Fig. 2).…”

“…Local gas phase ε i,j,k is often calculated with the measured voltage U meas at each grid point (i,j) and the measured voltage in the entire liquid/gas phase, U L (i,j) and U G (i,j), respectively, leading to 3 …”

“…With Δ z depending on the frame rate f and bubble velocity u B while ε i,j,k and Δ x , Δ y being the phase fraction and radial distances of the WMS, respectively. In their work, Theßeling and Grünewald 3 calculated u B with a correlation provided by Fan et al 13. The bubble diameter was approximated by …”

“…For data reduction and pre-processing, an algorithm developed by Theßeling and Gru ¨newald [3] is applied, which identifies the local position x, y and time t of the overall maximum signal. Afterwards, the experimental data set was reduced to a 7 7 matrix with the grid point of the maximum signal in the centre position since even in case of the largest investigated bubbles, signal intensity is no longer distinguishable from the noise signal at radial distances equivalent to more than three WMS grid points in each direction from the maximum signal position.…”

“…WMS has been applied to derive i.e. local and integral gas void fraction [3], radial profiles of void fraction [4,5] and to characterize CO 2 absorption [6].…”