The ignition of a combustible environment by hot jets is a safety concern in many industries. Hence, understanding the ignition of combustible mixtures by hot jets of burnt gases plays an important role in explosion protection. In explosion protection concepts, for a protection of the type "flameproof enclosures" a maximum permissible gap is of major importance. In this work a numerical framework is developed to investigate the ignition processes by a hot turbulent jet which flows out from such gaps. The method is used to explore the maximum nozzle diameter for specific boundary conditions which does not lead to an ignition. The scope of the this work is to investigate the mechanisms leading to ignition and explain the processes governing the ignition delay time as well as the ignition location. It is found that macro- as well as micromixing and the chemical kinetics have a profound influence on the ignition process and that a realistic model for the ignition process has to account for all these processes in combination with a transient description of the jet penetration. For the calculations a probability density function ( PDF ) method in conjunction with a reaction-diffusion manifold ( REDIM ) is employed.
This study is divided into two main parts. The first part of the work is dedicated mainly to the development, improvements and implementation of the models and the methods required to be used in the second part of the work. In this work a new formulation of the projection approach was introduced to be used in conjunction with stand alone PDF methods in order to calculate the mean pressure field.