Investigation of swirl meter performance

Abstract

The performance of vane- and impulse-type swirl meters was investigated, and a direct calibration method for swirl meters was developed. The zero-swirl bias of the meters was tested by installing an axially aligned tube on the swirl meter. Both the vane- and impulse-type meters showed insignificant zero-swirl bias. A known swirl was provided to the swirl meters using an offset, inclined tube arrangement. The angular momentum flux delivered by this system was found to depend linearly on the product of the offset distance and cosine of the inclination angle. Both the impulse- and vane-type meters were found to give measurements below the known swirl value, but both meters gave results that were linearly dependent on the angular momentum flux, which allows characterization of the meter’s efficiency with a single parameter. The efficiency of the impulse-type meter varied from 0.7 to 0.93, was a moderate function of the flow straightener aspect ratio, and depended slightly on the meter size. The vane-type meter’s efficiency was 0.32–0.45 for the conditions tested, was insensitive to the paddle wheel flow straightener aspect ratio, and depended significantly on the meter size. The vane-type meter measurements were also found to depend on the paddle-to-bore-diameter ratio; values slightly exceeding unity should be used. The swirl meter efficiency can be used to correct measurements to an absolute basis. Based on these findings, a universal correction factor does not exist, and a given measuring device will need to be calibrated using the methodology described.