Spherical Flames and Reactors
The spherical combustion geometry is important for a variety of technical and scientific applications. For instance, for saftey reasons high-pressure experiments on premixed flames, be they laminar or turbulent, often are conducted in so-called "combustion bombs" that are of spherical shape. These bombs are filled with a combustible mixture of gases and then ignited at the centre by a spark or a laser beam. After a transient ignition process, a spherical premixed flame forms and travels radially outwards. Both flame structure and flamespeed are of interest.
In addition, for modelling turbulent premixed combustion phenomena, flame stretch is a relevant quantity that can be measured experimentally in such configurations but which can also be evaluated numerically during a simulation. In this context, Markstein number and Markstein length are of particular importance.
With Cosilab such computations can be carried out. Not only are the fully transient flame structures resolved, but also flamespeed, Markstein length and Markstein number can be computed.
In the following figure, as one example, shown for an outwards propagating hydrogen-air flame are profiles of selected quatitities, namely of the temperature, of the molefractions of the radicals H, OH and O, and of the molefractions of the stable species O2, N2, H2O and H2. At the time of the screenshot, the flame zone was located approximately 2 cm off the centre.