The information in this paper is intended to provide a general knowledge of flow turbulence and its possible effects on flow metering and regulating stations. It gives station designers and operators insight into the mechanisms that can create excessive flow turbulence and its adverse effects, and well as strategies for mitigating turbulence-related problems, should they arise. Gas flows in metering and regulation stations are nearly always turbulent. Large-scale turbulence from flow separation and secondary flow patterns produced by elbows and other piping elements that change the direction of flow is present in pipe headers and other piping that leads to flow meters and pressure control valves. Pressure regulation produces additional flow disturbances that depend greatly on the regulator geometry and fluid velocity in the regulator. Excessive flow velocities can result in unacceptable velocity profile distortions, audible and ultrasonic noise levels, and piping vibrations that can cause metal fatigue damage or failure in piping systems. Metering station designs must take into account the shape of the velocity profile at the flow meter inlet to ensure that the profile is of sufficient quality for the flow meter of choice. A flow conditioner can be utilized to help ensure an adequate velocity profile at the flow meter inlet while also minimizing the meter station area or footprint. Pressure sensing and gas quality sampling taps should not be located in areas of large-scale flow structures (e.g. recirculation zone or in areas of secondary flow) because the gas dwelling in these areas is not usually representative of the gas properties for the flowing stream. In general, these sensing and sampling points should be at locations where the flow is consistent and well ordered, typically a significant distance upstream or downstream (preferably upstream) of any flow obstruction or piping headers or branches. While the reduction of flow velocity in a header is necessary for flow distribution among parallel branches, the void areas created in the header when flow is isolated from one or more of the parallel branches can allow the development of secondary flow patterns that produce noise.
Turbulence and its effects in measuring and regulating stations
2012
14 Seiten, 17 Bilder, 14 Quellen
Conference paper
English
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