ANALYSIS OF THE OCCURRENCE OF FLOW-INDUCED PULSATIONS IN A GAS CONTROL STATION

摘要

Strong flow-induced pulsations were observed at some measurement and control stations of the major gas transport company in the Netherlands, Gasunie. These resonances occur when the gas flow is passing closed side branches in the system at a sufficiently high velocity. Unsteady vortex shedding at the T-joints is a strong source of pressure fluctuations which can cause a strong pulsating flow when the vortex shedding is coupled with an acoustic resonance in the pipe system. For a specific case, pressure pulsation levels up to 3 bar pp were observed in a control station which caused unacceptable noise and vibration levels. The onset of these pulsations was analysed at TNO with the help of the PULSIM package, in which the pulsation source resulting from vortex shedding is incorporated. This enables a prediction of the resonance frequencies of the pipe system and an estimate of the pulsation amplitude caused by flow-induced noise. Not only the resonance frequencies could be predicted, but also the gas velocities at the onset of pulsating flow and the resulting pulsation levels. For two field cases this phenomenon is discussed with respect to the actual measurements on site and the simulation results and the solutions to prevent these problems in the future are presented.