| 摘要 |
A low pressure drop air flowmeter (10) for an automobile engine is disclosed. The meter contains a main air flow passage (24), a relatively small venturi (20) to receive a portion of the air flow, pressure ports (98a and 120) for sensing stagnation and static pressure and a set of swirl vanes (22) disposed adjacent the outlet of the venturi and operative to impart a swirl to the remainder of the air in the main passage, thereby creating a reduced pressure at the venturi outlet for amplifying the pressure difference between the stagnation and static pressure without appreciably increasing the pressure drop across the flowmeter. A tertiary passage (28) provides a path of fluid communication between points upstream and downstream of the swirl vanes. This passage includes a flow restricting throat (29) which is manually calibrated during or after assembly. Air exiting the tertiary passage impinges upon the swirl to modulate the vortex velocities. This arrangement results in a fluid flowmeter having a characteristic pressure drop which is less than that of a conventional device, particularly at high flow rates. Also disclosed is a solenoid valve (48) operative in the auto-referencing mode to selectively sample stagnation pressure in the tertiary passage or alternatively upstream of the venturi inlet and signal pressure in the throat of the venturi and generate an electrical output signal as a function of the diffrence between these two pressure signals.
|
