Flame luminescence was recorded at 30,000 frames per second with a high-speed CMOS camera system at the DLR Cologne. Prevapourised Kerosene was injected through a centre tube surrounded by swirled air. The gauge pressure was 4 bar. The sequence shows the formation of a precessing vortex core that 'tumbles' around the swirl nozzle exit.
The LES-G-equation model was modified to deserve for simulations taking into account variable mixtures. The local burning velocity of the flame (black iso-surface) is approximated as a function of the mixture which is displayed on a projected plane (blue: lean, red: rich). Selected streamlines illustrate the flow motion.
Large Eddy Simulation of a turbulent shear-layer. Before Helium (10.9m/s, 0.641kg/m3) and Nitrogen (4.12m/s, 4.49kg/m3) mix they are separated via a infinitifely thin splitter plate (l=0.005m). For the inlet conditions turbulent inflow data was generated according to Klein et al. 2003. The calculation was performed on a elliptically smoothed hexaedra grid consisting of 17 blocks (approx. 1x106 gridpoints).
LES of a strongly swirled flame. The premixed flame is illustrated by an iso-surface of the G-equation. Secondary air entrainment leads to dillatation of the premixed gas which is mapped on the G-surrface.
Instantaneous temperature field in a complex mixing device obtained with a hybrid LES-TPDF approach. Here isosurfaces of the cell-averaged Monte-Carlo solution (200 ppc) for 400, 415 and 430 K are plotted.
LES of a premixed turbulent bunsen flame using the Artificially Thickened Flame Model (Thickening Factor 15). The unresolved sub-grid fluctuations acting on the thickened flame front are modelled using the Smagorinsky approach.
The acoustic pressure disturbance in the nearfield of a turbulent diffusion flame (H3) is shown for a axial cut. (Flemming et al., AIAA-2006-2615, 2006)
The animation shows the temperature field in [K] of a non-premixed swirl flame computed by LES in combination with a steady flamelet chemistry model.
LES of the flow in a GDI engine.
DNS of a premixed flame kernel. The camera is moving around the flame.
3D DNS of a waterfilm ejected into air (top view).
LES of a premixed flame using the Artificially Thickend Flame model to simulate the enclosed propane-air-flame of the ORACLES burner. Equivalence ratio: phi=0.75. Cooperation with T. Broeckhoven (VUB).
The mixing of the fuel jet with the surrounding air flow is shown inside a generic gas turbine combustor. The isothermal swirling flow case is investigated.
The flame is passed by a pulsed laser beam (E ~1 J/pulse @ 532nm). The intensity of the Rayleigh and Raman scattered light serves to determine temperature and species concentration along a 1D region. In hot zones (i.e. in the flame fronts) the particle density is low and therefore the Rayleigh scattered light is weaker than in cold zones (center line, ambient space). The focussed laser beam causes thermal breakdowns if a dust particle is hit. (nozzle speed Uexit = 2.3 m/s, equivalence ratio phi = 2.4)
The Flame is passed by the vertical pulsed laser beam (E ~1 J/pulse @ 532nm, focus diameter ~0.3mm). The intensity of the Rayleigh and Raman scattered light serves to determine temperature and species concentration along a 1D region. (nozzle speed Uexit = 9.3 m/s, equivalence ratio phi = 0.62, Reynolds number Re = 30,000)
A representative event of extinction driven by a vortex . The sequence is taken by a high speed camera at 1 kHz. The flow is seeded with particles and illuminated 10 times per image by a high repetitive laser at 10 kHz.
The acoustic pressure disturbance in the nearfield of a turbulent diffusion flame (H3) is shown for a crossectional cut at x/D=25. (Flemming et al., Proc. Comb. Inst. 31, 2006)
Liquid jet breakup for low density ratio. 2D periodic configuration.
DNS of a strongly swirled isothermal flow. Recirculation zone is yellow. Precessing vortex core is blue. Background colour corresponds to scalar concentration.
Instantaneous density field of the Sydney swirling methane/air flame SMA2 – (Jet: methane/air (1:2) @ 66.3m/s, swirl number: 1.59). The simulation was carried out using the explicit, multigrid version of the LES solver FASTEST. Here an elliptical smoothed multiblock-grid with approximately 2.5 mio. grid-points was used.
Simulation of the Sydney bluff-body stabilized methane/air flame HM1e – (Jet: methane/hydrogen (1:1) @ 108 m/s). The simulation was carried out using the explicit, multigrid version of the LES solver FASTEST. The LES was started using RANS results as initial solution. Here an elliptical smoothed multiblock-grid with approximately 2.08 mio. grid-points was used.
Large Eddy Simulation of the Sydney N29S054 Low Swirl Flow (TNF model problem). Here iso surfaces of the absolute velocity are shown (35, 45, 66 m/s) together with axial velocity countours. The simulation was performed on an elliptical smoothed multiblock-grid with approximately 3.08 mio. grid-points. The resolution in the near nozzle region amounts 50 microns.