| 摘要 |
An air flowmeter (10) includes a main air flow passage (26), a relatively small venturi tube (28) receiving a portion of the air flow, a pressure port (74) for sensing stagnation pressure in the main passage, a pressure port (70) for sensing static pressure in the throat of the venturi, and a complimentary pair of sets of stationary swirl vanes (30, 32) disposed adjacent the outlet of the venturi to impart an air swirl in the main passage, thereby creating a reduced pressure at the venturi outlet for amplifying the pressure difference between the stagnation and static pressures. The sets of swirl vanes are rotationally displaceable with respect to one another, allowing some of the air to bypass the effect of the swirl vanes without being diverted to a separate passageway. This arrangement results in a fluid flowmeter having a characteristic pressure drop which is less than that for a conventional device, particularly at high flow rates.
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