MA - Development and Characterization of a Radial Wire Tomograph for Current-Based CT Imaging in Multiphase Systems

MA - Entwicklung und Charakterisierung eines radialen Draht-Tomographen zur strombasierten CT-Bildgebung in Mehrphasensystemen

Background

For the precise investigation of multiphase flows in industrial reactors, robust and high-resolution measurement techniques are essential. Classical wire-mesh sensors —pioneered and heavily developed by research groups such as HZDR and TU Dresden—offer excellent temporal resolution for multiphase pipe flows and bubble columns. Electrical Impedance Tomography (EIT), on the other hand, utilizes complex reconstruction algorithms but often suffers from the soft-field effect of boundary surface electrodes.

To bridge this gap, this thesis explores a novel, hybrid approach: a sensor where wire electrodes are arranged radially at various angles within the medium. The objective is to leverage the mechanical design principles, wire-tensioning techniques, and robustness of classical wire-mesh sensors, while replicating the physical behavior of a current-based computed tomography (CT) system. This approach potentially enables the use of established, analytical CT reconstruction algorithms (such as Filtered Backprojection) for electrical process imaging.

Objectives

The goal of this thesis is the systematic assembly and metrological characterization of this radial wire sensor. To manage system complexity and ensure strict testability, the development follows an incremental approach: starting with the analysis of the electrochemical interaction of a single wire, the setup will then be scaled and integrated into an existing, STM-based EIT measurement system. Finally, a mathematical transfer function will be developed to map the acquired impedance data into a CT-compatible format.

Work Packages

1. Literature Review and Conceptual Design

• Comprehensive literature review on classical wire-mesh sensors (WMS), specifically focusing on their mechanical construction, grid design, sealing techniques, and industrial applications (e.g., work by Prasser, Hampel, Schleicher, and Wiedemann).

• Review of electrode-electrolyte interactions in conductive media and the mathematical fundamentals of CT image reconstruction (Radon transform, Filtered Backprojection).

• Design of the mechanical fixture and housing for the radial wire arrangement, directly incorporating manufacturing experiences from state-of-the-art wire-mesh sensors.

2. Single-Wire Characterization and Calibration (Hardware Focus)

• Implementation of a simplified test setup to analyze the impedance of a single wire within the medium (e.g., using a 4-terminal/Kelvin sensing approach).

• Calibration of the wire's interaction (conductivity/impedance changes) using a suitable, high-precision reference sensor.

• Identification and quantification of parasitic effects such as double-layer capacitance and electrochemical drift in reactive or acidic media.

3. System Integration and STM-Based Measurement

• Adaptation of the radial sensor geometry to the existing, STM-based EIT data acquisition system.

• Integration and testing of an adapted, external current source for targeted excitation of the radial wire electrodes.

• Data acquisition and signal preprocessing during static and dynamic test operations.

4. Modeling and Transfer Function (Software/Algorithm Focus)

• Development of a physical-mathematical transfer function that maps the measured current/voltage data from the radial wires onto the line-integral concept of computed tomography (hard-field approximation).

• Export of the transformed data and exemplary image reconstruction using established open-source CT software packages (e.g., in Python).

5. Validation and Documentation

• Evaluation of image quality, artifacts, and spatial resolution using defined phantoms (non-conductive obstacles placed in the medium).

• Comprehensive written documentation and analysis of the methodology and experimental results.

Checklist

• Introduction / tour in M4

• Urheberrechtsvereinbarung signed

• if applicable: signed confidential agreement

• official registration

Helpful links:

• Thesis Work / Studentische Arbeiten 

• Criteria for the evaluation of Bachelor's and Master's theses, handout version

• Laborordnung

• Spotlights / Kurzvorträge

• Templates (Latex, ppt etc.)

Document Upload Final Thesis / Dokumentenabgabe Abschlussdokument

File of final presentation / Dokumentenabgabe Abschlusspräsentation

Link for further files / Link für weitere Dokumente