Abstract
This paper focuses on the hydrodynamic behavior of liquid pipelines in the presence of air valves. The aim of installing such valves on pipeline systems is twofold: on one hand, they release the accumulated air content and on the other hand, they allow the outer air to entrain the system when the internal pressure falls beneath ambient pressure (i.e. vacuum formation). We study the hydraulic transients in the presence of such air valve by means of experimental and numerical methods. The experiments were performed using a special test section where the pipeline close to the air valve was built from plexiglas allowing visual access. Furthermore, pressure signals were recorded at several locations of the pipeline. Numerical analysis was also performed using the commercially available CFD software (ANSYS CFX). It was revealed that the entrained air separates well from the primary liquid and the mixture behaves as two distinct phases.
Highlights
Introduction1.1 Purpose of air valvesIn hydraulic systems (e.g. water distribution systems, sewage systems) there are numerous phenomena during the dynamical behaviour that needs to be coped with as early as in the phase of design
1.1 Purpose of air valvesIn hydraulic systems there are numerous phenomena during the dynamical behaviour that needs to be coped with as early as in the phase of design
Pump shutdown due to failure in the power supply is a common origin of hydraulic transients: loss of the pump creates pressure waves with high amplitude that could lead to the dilapidation of the system
Summary
1.1 Purpose of air valvesIn hydraulic systems (e.g. water distribution systems, sewage systems) there are numerous phenomena during the dynamical behaviour that needs to be coped with as early as in the phase of design. Pump shutdown due to failure in the power supply is a common origin of hydraulic transients: loss of the pump creates pressure waves with high amplitude that could lead to the dilapidation of the system. Such transients can lead to two typical wave characteristics. The other regular source of the error is the negative pressure wave when vacuum is formed inside the pipes that typically leads to buckling In this case, the integrity of the pipe is usually intact (i.e. there is no leakage), it is more difficult to detect
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