| 摘要 |
A flow meter 10 comprising a body 11 having a throughbore 11a which defines a flow path 12; a flow displacement member 14; and a moveable sleeve 30 mounted within the flow path. The sleeve is slidable between and settable at different axial positions to select a predetermined flow rate measurement range. The sleeve may move relative to the flow displacement member and partially enclose it. The sleeve may act as an orifice or constriction by changing an inner diameter of the flow path and therefore its area ratio. The sleeve may have entrance and exit throat sections having a stepped profile (250a, Fig. 3E). There may be an external mechanism 40 to effect the axial movement of the sleeve which may be a manual, hydraulic, pneumatic, electrical or mechanical actuator that operates in a linear, rotary, reciprocating or oscillating motion. The mechanism may be coupled to a display to monitor and track the sleeve position. There may be a control unit for sensing the sleeve position and activating an alarm if the sleeve is incorrectly located. Also provided is a method of operating the apparatus which comprises moving the sleeve and obtaining a beta ratio value. |
