Passive scalar interface in a spatially evolving mixing layer (A. Attili and D. Denker)

Quartz nozzle sampling (D. Felsmann)

Dissipation element analysis of a planar diffusion flame (D. Denker)

Turbulent/non-turbulent interface in a temporally evolving jet (D. Denker)

Dissipation elements crossing a flame front (D. Denker and B. Hentschel)

Particle laden flow (E. Varea)

Turbulent flame surface in non-premixed methane jet flame (D. Denker)

DNS of primary break up (M. Bode)

Diffusion flame in a slot Bunsen burner (S. Kruse)

Various quantities in spatially evolving jet diffusion flame (D. Denker)

OH layer in a turbulent wall bounded flame (K. Niemietz)

Capsule to investigate ultra-slow flame propagation in micro-gravity

Ultra-slowly propagating flames are well known to be challenging for measuring their burning velocity. Conventional methods, such as flat burners and closed combustion vessels, fail to produce accurate flame speed data at normal gravity because of the flame structure being violated by buoyancy. This is crucial for the characterization of fundamental combustion and fire-safety properties of slowly-burning alternative fuels (ammonia), modern refrigerants with low global warming potential (R-32, R-1234yf, etc.), and any other combustible mixtures close to the flame propagation limits.

Description of the setup

The High repetition chamber to determine laminar flame speeds is regularly used by ITV for the investigation of ultra-slowly propagating flames in micro-gravity. A compact dual-field schlieren arrangement is installed vertically with a high-power LED light source at the bottom and a high-speed CMOS camera at the top. Flame images are recorded at 10000 frames per second (fps) with a spatial resolution of 17.5 pixel/mm. The entire experimental capsule is pivotable in the normal laboratory environment to allow for flame recordings in two camera angles, aligned parallel and perpendicular to the gravitational force.

After the vessel and tube network are evacuated from residual gases, the vessel is filled via an additional premixing chamber. The process is remotely controlled with solenoid shut-off valves, mass-flow controllers, and an additional pressure-regulating valve at the chamber outlet. After sufficient mixing time and once the set-point ignition pressure remains steady, the valves are closed simultaneously. The igniting spark is discharged through two elongated tapering spark plug electrodes positioned opposite each other.

The ITV-designed capsule is capable of conducting micro-gravity experiments in drop tower facilities, such as the novel GraviTower Bremen Pro of ZARM (Center of Applied Space Technology and Microgravity, Bremen, Germany). The GraviTower allows ITV to perform ~30 micro-gravity combustion experiments a day, providing a unique opportunity for multiple parameter variations and a high repetition rate. Thus, unique insights into radiation, physics, and chemistry of slowly propagating flames can be gained and analyzed by ITV.