Generalized characterization of pipeline systems with air chamber through development of the dimensionless impedance response

Abstract

An air cushion chamber is a feasible and efficient hydraulic device to control water hammers for pressurized pipeline systems. Considering that all factors simultaneously can be incredibly difficult, even for a simple air chamber pipeline valve layout, this study introduces the dimensionless transfer function and expression for air chambers in the dimensionless frequency domain to effectively address the water hammer generation and its counteracting processes. To comprehensively characterize hydraulic transients for pipeline systems equipped with air chambers, two representative dimensionless parameters were used. One parameter corresponded to the main pipeline and the other to the air chamber. Along the pipeline system, it is possible to develop a frequency-independent expression for hydraulic impedance, which can be translated into a time-domain expression for pressure. A comparison between the developed method and other existing methods (e.g. characteristic method and impulse response method) revealed excellent agreement. Application of the dimensionless parameters to systems with different dimensions and hydraulic conditions shows that the proposed dimensionless parameters can address substantial ranges of real systems. It has been investigated how two dimensionless parameters have an impact on hydraulic responses over a wide range of parameter combinations and flow conditions.