Performance Similarity between Different-Sized Air Exchange Valves

A central element of a pipeline’s air management infrastructure is typically its set of air exchange valves (AEVs), a designation that includes air release and air/vacuum valves. Knowledge of the air mass flow rate as a function of pressure difference is essential for AEV selection and design, a relationship expressed by its somewhat complex and certainly nonlinear characteristic curve (CC). However, both measurement and simulation of this CC are often nonintuitive and, for various practical and theoretical reasons, problematic. To provide greater insight, several helpful performance scaling analyses are undertaken here with the goal of aiding system investigation, design, and operation. To this end, a performance similarity relation (PSR) for different-sized AEVs is developed and its effectiveness demonstrated in the light of commonly available air mass flow data. Also, the PSR is successfully applied to aid in the interpretation of published experimental air expulsion data. Additionally, the interaction of the CC with basic pipeline parameters on system performance is explored in the context of common hydraulic transient events. For this second application, the water-hammer pressures generated by a pump trip scenario are numerically simulated for several test pipelines, considering four AEV sizes each having three possible characteristic curves.