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Low Loss Vortex Flowmeter For Non-Corrosive Gas

IP.com Disclosure Number: IPCOM000049193D
Original Publication Date: 1982-May-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 53K

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Feigel, FR: AUTHOR


The reproducible measure of airflow with a very low pressure drop makes it especially suited to low head delivery systems such as blowers.

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Low Loss Vortex Flowmeter For Non-Corrosive Gas

The reproducible measure of airflow with a very low pressure drop makes it especially suited to low head delivery systems such as blowers.

The phenomenon of vortices being shed at regular intervals from a non- streamlined object in a fluid flow path has been known and observed for a long time, dating back to Leonardo da Vinci. That the shedding frequency is linear with respect to stream velocity is also well known. However, few of the prior-art devices are reliable for gaseous flow, and none are suitable where insertion pressure loss must be less than a few inches of water.

The airflow meter described below and illustrated in the figures has shown reliable, high signal to noise output, free from intermittency at insertion losses of
.4 inch of water when operated at altitudes from sea level to 7,500 feet, and a temperature range of 15 degrees C to 35 degrees c.

The order of magnitude decrease in pressure drop from previously disclosed flowmeters is a result of two factors. The primary factor is the novel construction of the bluff body and integral sensing element which greatly increases sensitivity and reliability. Secondary is the construction of the flowmeter conduit.

Unlike other vortex type flowmeters which have circular conduits. the flowmeter depicted in the drawing uses a rectangular conduit 10. Since the shedding of vortices is predominantly a two-dimensional effect, the rectangular cross sectional conduit 10 of the flowmeter presents more of a quasi two dimensional effect than a circular cross section. As vortices are shed, flow and pressure vary alternately around the bluff body 15. The design of the bluff body 15 provides for the measurement of the differential pressure directly at the sidewalls of the body 15, cancelling out common mode noise which might appear from either vibrations or blower noise.

As shown in Fig. 1, the bluff body is essentially a right isoceles triangular prism with a solid apex angle of 3O degrees. The narrow plane, opposite the apex is modified to be a convex surface 17. Except for the difference in circumferential curvature the b...