In project 7, ignition caused by turbulent free jets of hot gas impinging into a fuel/air mixture is investigated. This is done by numerical simulations using a statistical approach to treat turbulence and turbulence/chemistry interactions, and by experiments which are used to create empirical data which help to assess the accuracy of the numerical simulations. During the project, the numerical models underlying the simulations will be continuously refined, so that finally an improved simulation tool with higher predictive capabilities than currently possible will result. In this process, there will also better insight into the detailed processes in hot jet ignition be gained.

In detail, a probability density function (PDF) method will be used for treating the turbulent jet and its interaction with the surrounding fuel/air mixture. A full transport equation for the joint PDF of velocity and scalars will be solved. To describe chemical reactions, already existing reduced models will be used. 

Measurements in free jets mixing with quiescent surrounding air will be performed using laser-based techniques. To isolate effects of missing and of reaction, two kinds of experiments will be performed, namely inert mixing of a low-density jet (helium) with nitrogen, as well as a reacting configuration with a hot jet of combustion products impinging into a fuel/air mixture.

The model development will profit from the input of project 1 (Physical and chemical models for ignition processes) and project 6 (DNS).