Mitigating Combustion-driven Oscillation (Thermoacoustic Instability) in Industrial Combustors

Combustion processes generate a band-limited pseudo-random sound that is often referred to as “combustion roar.” Although combustion roar sound is moderately intense but it is rather straight forward to quiet to a non-objectionable level by properly applying sound absorbing material around the burner area. In addition to the 'roar' sound which almost always exists in any confined combustion, on occasion a very intense, narrow-band (frequently single-frequency/tonal) noise is generated in a combustion chamber resulting in a high-amplitude, self-sustaining pressure oscillation. This phenomenon originates from a coupling between the flame‟s heat release dynamics, the combustor acoustics, as well as transient fluid dynamics in the combustor and is referred to by many names including, but not limited to, „combustiondriven oscillation‟, „combustion dynamic instability‟, and , „thermoacoustic instability‟. The excited acoustic oscillation causes large pressure fluctuations (high combustor noise levels), poor combustion, increased emissions and even catastrophic combustor failure (structural damage). „combustion-driven oscillation‟ has been reported in all types of combustion systems including industrial combustors (heaters, boilers, etc.), propulsion systems (rockets, afterburners) and gas turbine combustors.