| 摘要 |
A system for metering the flow rate of air through a duct in which gates are pivotally mounted and connected together to vary the area of the duct. The gates are balanced so as to be effectively weightless. The forces on and the position of the gates correspond to the pressure and the flow rate in the duct thereby avoiding the need for air pressure transducers exposed to the pressure in the duct. The forces due to the pressure in the duct are amplified by the gates so that the pressure measurement as a function of the forces on the gates is a much more sensitive function of the flow rate through the duct than is obtainable directly in response to the pressure in the duct (for example, the velocity pressure of air as measured by pressure transducers responsive directly to the velocity pressure in the duct). A computer system is responsive to the position of the gates and to the magnitude of an actuating signal (the fluid pressure applied to an actuating cylinder coupled to the gates) for determining the air flow rate and for varying the actuating signal in order to control the area in the ducts between the gates so as to obtain a desired air flow rate.
|
