The bluff body stabilized premixed flame in an acoustically resonating tube: combustion CFD and measured pressure field.

The resulting limit cycle amplitude and frequency spectrum of a flame placed in a combustor of rectangular cross section is investigated. The partially premixed flame is stabilized on a bluff body placed in the upstream half of the combustor. The bluff body is an equilateral triangular wedge with one of the edges pointing in upstream direction. Acoustically there is an open downstream end and theer are variable acoustic conditions at the upstream end. In order to assess the properties of the flame in this combustor, steady state flame simulations have been performed of the flame in the enclosure. These provided the fields of the mixing of gases, temperature and the velocity. A test rig was manufactured for this burner at the University of Twente. In a first set of experiments, gas temperature, pressure field and flame chemiluminescence in the combustor were measured as a function of power and acoustic inlet condition. It was observed that the combustor exhibited strong natural pressure oscillations. The measured pressure, temperature and chemiluminescence data are compared to the CFD simulations and to numerical calculations of the acoustics presented in a companion paper by M.Heckl.