www.elsevier.nl/locate/jnlabr/yjfls Journal of Fluids and Structures 18 (2003) 771–781 Spurious counts in gas volume flow measurements by means of turbine meters P.W. Stoltenkamp a, *, S.B. Araujo a , H.J. Riezebos b , J.P. Mulder b , A. Hirschberg a a Fluid Dynamics Laboratory, Department of Applied Physics, Technische Universiteit Eindhoven, Building Cascade, P.O. Box 513, Eindhoven 5600 MB, Netherlands b Gasunie Research, N.V. Nederlandse Gasunie, Energieweg 17, 9743 AN Groningen, Netherlands Received 3 March 2003; accepted 12 August 2003 Abstract Acoustical oscillations can induce a rotation of a turbine flow meter in the absence of main flow, which leads to spurious counts. A simplified model is presented which explains the occurrence of spurious counts in the limit of very thin turbine blades and high Strouhal numbers. The predicted threshold for the occurrence of spurious counts is compared to experimentally obtained data at various gas pressures in the range from 1 to 8bar. The simplified model provides a reasonable prediction of the occurrence of spurious counts and can be used as an useful engineering tool in the prediction of the occurrence of spurious counts. r 2003 Elsevier Ltd. All rights reserved. 1. Introduction Turbine flow meters are often used to measure volume gas flows in gas transport systems. These turbine flow meters are placed in a measurement manifold, consisting of several runs. Flow pulsations in these manifolds affect the accuracy of the flow turbine meters. The N.V. Nederlandse Gasunie (the Dutch gas authority) discovered that these pulsations not only affect turbine meters in open pipes, but can also incidentally cause spurious counts in turbine meters placed in a closed side branch in which there is no main flow. These spurious counts start above a certain critical pulsation level. Spurious counts that occur in open pipes, where a mean flow velocity is present has been studied by several authors (Cheesewright et al., 1996; McKee, 1992; Grenier, 1991; Dijstelbergen, 1966). The aim of the research is to obtain a better understanding of spurious counts under conditions for which there is no main flow. A simplified theoretical model is presented which explains the occurrence of these spurious counts in the limit of very thin turbine blades. The predicted threshold for the occurrence of spurious counts is compared to experimental data at various gas pressures in the range from 1 to 8 bar. 2. Theory The spurious count behavior of a turbine meter can be explained by considering the forces acting on an aerofoil in an oscillating flow. The blades of the turbine rotor used in these gas transport systems have a rounded leading edge and a sharp trailing edge (see Fig. 1). This asymmetry causes the rotation. ARTICLE IN PRESS *Corresponding author. Fax: +31-40-246-4151. E-mail address: p.w.stoltenkamp@tue.nl (P.W. Stoltenkamp). 0889-9746/$-see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfluidstructs.2003.08.019