Analysis of Nonlinearity of the Turbine Gas Meters Time Constant During Step Response

Turbine flowmeter response to transitional flow regimes

“…( 7)-( 9), all modeled variables (V50, θ and τ) increase with the flowmeter size δ. This is consistent with the findings of Cheesewright et al [10] and Tonkonogij & Tonkonogovas [15] who reported longer response times and larger over-registered volumes for larger turbine flowmeters. Such behavior can be explained by the fact that larger flowmeters possess a higher ratio of inertial mass forces to dissipative forces of aerodynamic drag and friction in bearings and other mechanical elements [5].…”

“…2, the dynamic response of investigated flowmeters will be presented by curves of the normalized turbine rotational speed ωn (Figs. [15]). However, the dynamic response of the normalized rotating speed ωn to otherwise very quick flow deceleration is slow, with halving times τ1/2 between 6 s and 35 s and generally dropping with Q (Fig.…”

“…These are mostly induced by quick changes in the flow rate of gas, usually due to opening or closing of a pipeline valve or sudden changes in gas demand. The rotational speed of a flowmeter turbine typically follows the flow acceleration well, but exhibits a significant delay when slowing in a decelerating flow (Cascetta & Rotondo [8], Tonkonogij et al [14], Tonkonogij & Tonkonogovas [15]) resulting in over-registration of gas volume. Despite the exponential reduction of the turbine rotational speed [14] [15], the meter response duration may be relatively long compared to the duration of the flow transition (especially if the flow is completely stopped), leading to significant over-registration of gas volume.…”

“…According to Cascetta and Rotondo [8], a typical medium-sized turbine flowmeter may experience as much as 10000 on/off cycles or other significant step changes in flow rate per year, consequently overestimating the gas volume by more than 1%. In [14] and [15], response characteristics and corresponding dynamic measurement errors of turbine gas meters are discussed in dimensionless form.…”

Skysčio ir dujų srautų dinamikos kanaluose tyrimai tūrio, debito ir greičio matavimų tikslumui didinti

“…čia: τ -laiko pastovioji; ω -sukimosi dažnis; t -laikas; indeksai gal ir pr -atitinkamai pulsaci jos laikotarpio pabaigoje ir pradžioje. Laiko pastovioji buvo nustatoma dviem meto dais, laikant ją pastoviu dydžiu atsako metu, bet priklausantį nuo rotoriaus inercijos parametrų ir debito, arba laikant ją kintamuoju dydžiu [4,9], apskaičiuojamu pagal priklausomumą: ;…”