MODELING OF RING VORTICES AND THEIR INTERACTION WITH TURBULENT PREMIXED FLAMES

Abstract

Depending on amplitude and frequency of self-excited flame/pressure oscillations in technical combustion systems, the formation of large-scale turbulent ring vortices can be observed which interact with the flame. The phenomenon was investigated with numerical simulations using unsteady Reynolds-averaged Navier–Stokes methods. The results were validated against experimental data. The calculation of the forced isothermal flow field yields that the prediction of the transient vortex positions works very well. In contrast, the turbulent diffusion is underestimated. The flame frequency response of a forced premixed turbulent axial methane jet flame (P _therm = 40 kW) was calculated using a simplistic turbulent reaction model. The measured flame frequency response was derived via detection of the global radiation of OH radicals and the calculated flame response via analysis of the global heat release rate. Despite the fact that a quantitative comparison of these properties is not possible, a qualitative comparison shows good agreement regarding the representation of amplitude response and phase-angle function.

Keywords:

• modeling
• CFD
• turbulent instationary premixed flames
• combustion instabilities
• ring vortices
• flame frequency response

This work was founded by the DFG (Deutsche Forschungsgemeinschaft) under project number BO293/12-2. The support is gratefully acknowledged.