Industry new

Introduction to the working principle of pulsating flow

Arterial motion is common in industrial tube flow, which may be generated by rotary or reciprocating prime movers, compressors, blowers, pumps, and winged rotating machinery can also produce small pulsations at the blade passing frequency. Some positive displacement meters can also produce pulsation. Vibration-induced resonances, oscillations in piping operations and control systems, flow separation caused by valve "hunting", pipe fittings, valves or rotating machinery are also sources of flow artery motion. Flow arterial motion may also be triggered by fluid dynamic oscillations caused by flow systems and multiphase flow. For example, the fluid flows through the temperature measuring protection tube, and a vortex is generated as if it flows through the vortex generator of the vortex flowmeter; in the flow path of the three-way connection, the self-excitation causes fluid oscillation or the like.
From the field instrument indication, the presence of pulsations in the industrial pipe flow is often not seen. This is because the commonly used flow meters and pressure gauges are slow to respond and have a tail stop, but in fact, flow arterial motion may exist. The pulsation can also be transmitted from the upstream to the downstream, or from the downstream to the upstream, so the pulsation source may affect its indication upstream of the flow meter, or it may affect its indication downstream of the flow meter. However, an increase in the distance from the pulsation source to the flow meter can attenuate the pulsation and the amplitude becomes small. It can be attenuated by compressibility effects (including gases and liquids) to detect no pulsation amplitude at the flowmeter installation location.
Flow arterial frequencies range from a few fractions to hundreds of Hz, and pulsation amplitudes from a few percent to one hundredth of an average flow, or even larger, are possible. When the pulsation amplitude is small, it is often difficult to distinguish between pulsating flow and turbulence.
The main parameters of the pulsating flow are the pulsation amplitude, the pulsation frequency and the pulsation waveform. Among them, the pulsation amplitude is expressed by the ratio of the rms value of the flow velocity fluctuation to the average flow velocity.

PREVIOUS：Analysis of the influence of flow artery motiNEXT：Description of uncertainty in flow measuremen