During ACHEMA 2012 in Frankfurt am Main, the trade fair newspaper ACHEMA Daily reported on the new optical measurement technique from the Institute of Fluid Mechanics and Aerodynamics at TU Darmstadt. The article appeared in the section “Partikelcharakterisierung” (particle characterization) under the German headline “Größe und Geschwindigkeit von Partikeln und Tropfen messen” – measuring the size and velocity of particles and droplets.

ACHEMA Daily article “Größe und Geschwindigkeit von Partikeln und Tropfen messen” with a photo of Walter Schäfer
ACHEMA Daily, June 2012. Photo in the article: Wühr. Click to enlarge.

What the Article Reported

The article explains why the characterization of droplets and particles in a flow is central to many process engineering tasks, for example measuring droplets in spray drying. According to Walter Schäfer, established methods for measuring size and velocity were not suitable for non-transparent particles or for droplets of suspensions and emulsions.

  • Improved time-shift technique: Walter Schäfer and his colleagues extended the known time-shift technique with new evaluation and validation algorithms, so that such measurements become reliable in technical systems with little instrumentation effort.
  • Compact optics: The optical configuration was considerably simplified and made smaller. It can be set up in forward or backward scatter, can therefore also be used where access to the process is limited, and is easy to adapt to special tasks such as milk powder or hair spray production.
  • Droplets and solid particles: Besides droplets, solid particles can be measured in size and velocity. In many cases the refractive index can also be determined to distinguish between different phases. Users thus obtain a simple, flexibly positionable inline system for process monitoring and optimization.
  • Prototypes and patents: Prototype instruments were already in use, and the key new developments had been filed for patents. For transparent particles, measurement range and accuracy were comparable with established optical methods.
  • Funding: The research was supported by the German Research Foundation (DFG) and the Research Training Group (Graduiertenkolleg) 1114, among others.

At the Stand in Hall 9.2

Time-shift measurement demonstrator at the TU Darmstadt stand at ACHEMA 2012
The time-shift demonstrator at the TU Darmstadt stand: spray chamber, optical probes on a traversing system and live signal processing.
Walter Schäfer in conversation with a visitor at the ACHEMA 2012 stand
Walter Schäfer explaining the measurement technique to a visitor.

Trade Fair Brochure

For ACHEMA 2012, the institute published a bilingual brochure (German/English) titled “Optisches Zeitverschiebungsverfahren zur Partikelcharakterisierung – Time-Shift Technique for Optical Particle Characterization”.

Cover of the TU Darmstadt brochure “Time-Shift Technique for Optical Particle Characterization”
Cover
Inside pages of the TU Darmstadt brochure with measurement principle and optical setup
Inside pages (German and English)

From Research to ai-quanton

The time-shift technique shown at ACHEMA 2012 is one of the technological roots of the measurement systems developed by ai-quanton today. More about the exhibition itself: ACHEMA 2012 – First Public Presentation of TSTOF Spray Measurement Technology. The principle is explained in TSTOF and Light-Scattering Signals.