Swirl dampers were components of the matter/antimatter injector assembly on Galaxy-class starships.
During a brainstorming session in engineering with the senior engineering staff in an attempt to solve a problem with the fuel injectors on the USS Enterprise-D in 2366, Geordi La Forge stated that if the fuel inlet servos were caught in cycle, the swirl dampers would be frozen as well. (TNG: "Hollow Pursuits")