Teacher: Prof. dr. Omer L.Gulder
In the design and development of engines that are operating in the turbulent premixed combustion mode, it is frequently desired to have an accurate estimate of the mixture burning rate. Often, an approximate estimate of the global mixture consumption rate may seem sufficient, but there are several instances for which a detailed account of the turbulent burning rate is of critical importance. However, the processes involved in turbulent premixed combustion are surprisingly complex and some of the factors affecting it are so elusive that our grasp and account of this crucial problem is in a confused state. As compared to other combustion problems, turbulent premixed combustion has very few tenets whose underpinnings are firmly established.
There are several contentious issues related to (a) the inner structure of the premixed turbulent flame front under various flow field and turbulence conditions, and (b) the Damkohler’s hypothesis which postulates that, for low intensity turbulence, the turbulent burning rate scales with the increase in the flame front surface area instigated by the turbulence field, and its validity range. Further (c) the disparity between recent experimental results and the data produced by DNS computations, and (d) the apparent disagreement among empirical/semi-empirical burning rate correlations oriented towards practical engineering applications are subjects of debate.
These controversies will be presented and discussed after an introduction to the subject area and its importance. The validity range of the so-called flamelet approach will be elaborated using the results of recent experimental studies from the author’s laboratory as well as the data from other research groups. Known limitations of experimental techniques as well as those involved in numerical simulations will be assessed.