A duct and method for damping pressure waves caused by thermoacoustic instability

摘要

To damp pressure waves caused by thermoacoustic instability a duct 10 has a locking Helmholtz resonator HHR1 on the circumference tuned to a first frequency, and damping Helmholtz resonators HHR2 tuned to a different frequency on the circumference at or adjacent to 90° and/or 270° from the locking Helmholtz resonator HHR1. The damping Helmholtz resonators HHR2 can be in pairs either side of 90° and/or 270°. The duct can be a combustion chamber of a turbomachine, furnace or boiler. There can be another locking Helmholtz resonator (HHR3, fig 4). The resonators can be tuned by adjusting neck length, volume, or changing temperature.