Passive control of combustion instability in lean premixed combustors

A Solar fuel injector that provides lean premixed combustion conditions has been studied in a combined experimental and numerical investigation. Lean premised conditions can be accompanied by excessive combustion driven press ure oscillations which must be eliminated before the release of a final com bustor design, In order to eliminate the pressure oscillations the location of fuel injection was parametrically evaluated to deter mine a stable conf iguration. It was observed that small axial changes in the position of the fuel spokes within the premix duct of the fuel injector had a significant p ositive effect on decoupling the excitation of the natural acoustic modes o f the combustion system, In order to further understand the phenomenon, a r ime-accurate 2D CFD analysis was performed 2D analysis was first calibrated using 3D steady-stare CFD computations of the premixer in order to model t he radial distribution of velocities in the premixer caused by non-uniform inlet conditions and swirling flow. 2D rime-accurate calculations were then performed on the baseline configuration. The calculations captured the cou pling of heat release with the combustor acoustics, which resulted in exces sive pressure oscillations. When the axial location of the fuel injection w as moved, the CFD analysis accurately captured the fuel rime lag to the fla me-front, and qualitatively matched the experimental findings.