Optical diagnostics

Experimental study of fluid flows in general and combustion in particular requires techniques that are non-intrusive: they should not affect the phenomenon under study. Optical diagnostics is undoubtedly the most powerful class of such techniques, and we have a wide range available. Experimental facilities include not only a variety of (often laser-based) diagnostic techniques, but also optically accessible combustion and flow equipment. Much of our work uses spectroscopic techniques to single out individual chemical species.

Available optical techniques:

  • Particle Image Velocimetry (PIV)
  • Schlieren & Shadowgraphy
  • Diffused Back-illumination Imaging (DBI)
  • Chemiluminescence imaging
  • (Planar) Laser Induced Fluorescence ((P)LIF)
  • (Planar) Laser Induced Phosphorescence ((P)LIP)
  • Spontaneous Raman & Rayleigh Scattering
  • (Hi-speed) laser-Induced Incandescence ((HS)LII)
  • Interferometric Particle Imaging (IPI)

 Available test rigs:

  • Optically accessible heavy-duty CI engine
  • Optically accessible light-duty CI engine
  • Constant-volume spray vessel
  • Various dedicated burner systems

Composite image of the structure of a fuel spray under conditions relevant for heavy-duty Diesel engines (made by Noud Maes). The fuel spray enters at the left, and is recorded 700 µs after start-of-injection (aSOI). White line: vapour boundary of an inert spray (Schlieren); Blue line: liquid boundary (DBI); Green: electronically excited OH radicals (flame front; chemiluminescence); Red: formaldehyde (low-temperature reactions; PLIF).

Raman spectrum of a non-premixed n-heptane doped with a few percent of toluene (made by Robin Doddema). The horizontal axis represents the Raman shift, the vertical axis the height above the burner exit.