Study of elbow effect on pulsation in piping system

BWR (Boiling Water Reactor) had recirculation pumps, which are centrifugal type. They generate pressure pulsation by vane passing. Pulsation is one of the important causes of vibration. It is a common problem in piping system. In order to predict vibration of piping system, the authors to know or predict the distribution of pulsation amplitude. They measured the distribution in a simple piping system, which consists of straight pipes, elbows, a tank and a pump. In this system the pulsation was generated by the pump's vane passing. Pulsation wave reflected at pipe end and formed standing wave. It is conventionally said that the standing wave is sinusoidal and that the phase does not change at straight pipes and elbows. However the authors measured discrepancy from conventional theory at elbows. The amplitude and phase changed discontinuously at elbows. When one locates at loop of standing wave, the discrepancy is large. The authors considered that it is caused by partial reflection at elbow and calculated the distribution taking this effect into account. They obtained good agreement with the calculation and the measurement