Effect of Disc Geometry on the Dynamic Stability of Direct Spring Operated Pressure Relief Valves

Abstract

Abstract. The most important parameter of a direct spring operated pressure relief valve is its capacity, which is the rated flow through the valve under conditions given by the corresponding industrial standard. There are several phenomena due to which dynamic instabilities may arise in the system, leading to dangerous oscillations and reduced flow rate. One of the causes of these instabilities is the acoustic coupling of the valve with its upstream piping, the mathematical background of which has already been thoroughly investigated by the researchers at our department. As a continuation of that work, this paper focuses on the engineering applications by proposing various valve disc geometries based on preliminary measurement results, and evaluating their dynamic stability performance in a wide range of parameters. Steady-state CFD computations were performed to determine the mass flow rate and force characteristics of the various valve discs. Through these quantities, the behaviour of each geometry was implemented into our one-dimensional coupled gas dynamical solver, which resolves the pipe dynamics using the one-dimensional continuity-, momentum-and energy equations. The valve itself is modelled as a one degree-of-freedom oscillator. Finally, the stability maps of each geometries were calculated using the gas dynamical model and it was shown that the shape of the fluid force function does indeed have a significant effect on the stable operating range. 7695

Dynamic behaviour of direct spring loaded pressure relief valves connected to inlet piping: IV review and recommendations

“…In general though, it should be noted that the encapsulation of the exiting flow features into a single discharge coefficient C d for a given fluid and geometry is an engineering simplification. In practice, as can be confirmed with CFD Misra et al (2002); Bazsó and Hős (2012); Erdődi and Hős (2015), the 'coefficient' can be shown to a (typically quite weak) function of the valve opening, C d (x v ), which is relatively straightforward to determine experimentally. We should stress though that variation of C d with x v is not believed to be the primary cause behind any form of valve instability.…”