Investigation of Diametral Acoustic Modes in a Model of a Steam Control Gate Valve

Abstract

The objective of the present study is to provide an insight into mechanism of coupling between turbulent pipe flow and partially trapped diametral acoustic modes associated with a shallow cavity formed by the seat of a steam control gate valve. First, the effects of the internal pipe geometry immediately upstream and downstream of the shallow cavity on the characteristics of partially trapped diametral acoustic modes were investigated. The mode shapes were calculated numerically by solving a Helmholtz equation in a threedimensional domain corresponding to the internal geometry of the pipe and the cavity. Second, the set of experiments were performed using a scaled model of a gate valve mounted in a pipeline that contained converging–diverging sections in the vicinity of the valve. Acoustic pressure measurements at three azimuthal locations at the floor of the cavity were performed for a range of geometries of the converging–diverging section and inflow velocities. The experimentally obtained pressure data were then used to scale the amplitude of the pressure in the numerical simulations. The present results are in good agreement with the results reported in earlier studies for an axisymmetric cavity mounted in a pipe with a uniform crosssection. The resonant response of the system corresponded to the second diametral mode of the cavity. Excitation of the dominant acoustic mode was accompanied by pressure oscillations corresponding to other acoustic modes. As the angle of the converging–diverging section of the main pipeline in the vicinity of the cavity increased, the trapped behavior of the acoustic diametral modes diminished, and additional antinodes of the acoustic pressure wave were observed in the main pipeline.