Numerical investigation of the ignition of diethyl ether/air and propane/air mixtures by hot jets

Electrical equipment for use in hazardous areas has to be specially designed and tested to avoid an explosion. Typical ignition sources like arcing contacts can e.g. be enclosed by flameproof enclosures. An internal explosion may lead to jetting of hot exhaust gases through inevitable gaps like joint clearance or other gaps into the surrounding, which may result in an accidental explosion. The initiation of an explosion in a premixed mixture either of diethyl ether and air or of propane and air caused by hot exhaust gas jets is examined in this work by means of numerical simulations. A PDF-PM algorithm is used to examine the ignition processes. The algorithm is based on a Lagrangian PDF (probability density function) method, in conjunction with a projection method (PM) to calculate the mean pressure for transient flows. The transport equation for a joint velocity-turbulent frequency-scalar PDF is solved by a Monte Carlo/particle method. The reaction-diffusion manifold (REDIM) technique is used to reduce the computational cost concerning the calculation of chemical reactions. The chemical time scales of diethyl ether and propane are nearly identical and they have nearly identical maximum experimental safe gap (MESG) values. Therefore, the ignition processes of both gases are compared to evaluate the used numerical model.