Vibration related outages due to an unbalance in rotating equipment have been a historic problem in the power generation industry and have resulted in increased plant operating costs. Until recently, the only means for solving these vibration problems was to perform manual balancing on the rotating equipment. Active balancing systems have been used in other industrial processing applications, on ID/FD fans, compressors, and turbines, for many years. Further developments in active balancing capabilities have positioned these systems to cover the broad range of applications in the power generation industry today.
The aft interior of the DC-9 aircraft is generally considered to be uncomfortably loud (100–110 dBC). This noise is primarily periodic and is caused by imbalances in the fan and turbine of the Pratt Whitney JT8D engine. Lord Corporation has recently developed active and adaptive passive systems to combat this problem. The active system uses four force-generating actuators located on the left and right engine pylons to minimize the response at eight control microphones which are located in the rear of the cabin. The adaptive passive system consists of eight tuned vibration absorbers whose natural frequency is adapted to the engine speed. An overview of each system with theory will be presented as well as experimental results where the tonal noise reduction and engine speed tracking capabilities of each system were evaluated using an identical engine vibration input on a DC-9 fuselage. These experimental results showed that the active system achieved larger tonal noise reductions and had faster tracking ability than the adaptive passive system.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.