Viscosity-insensitive mechanical fluid flow regulator

摘要

The differential-pressure-sensing and variable-area-occluding fundtions within variable-area flowmeters and flow regulators are performed by separate, but mechanically connected, elements. A housing defines a channel for guiding fluid flow from an upstream to a downstream location. A differential pressure sensor moves in a direction substantially perpendicular to the direction of fluid flow in response to a differential fluid pressure between the upstream and downstream locations. Because the movement of the pressure sensor is substantially perpendicular to the flowing fluid with which it comes in contact, it is substantially insensitive to fluid friction and to changes in fluid viscosity. A flow obstructor connects to the sensor and moves therewith to variably obstruct the channel and its flow of fluid from the upstream to the downstream location. Fluid frictional forces on the movement of the flow obstructor vary with changes in fluid viscosity. However the ratio of the area of the flow obstructor to the area of the pressure sensor, which ratio substantially equals the ratio of the fluid frictional forces to the pressure force, is consistently low, typically 1:100. Consequently the overall flowmeter or flow regulator is relatively insensitive to changes in fluid viscosity. It typically exhibits less than +/-1% deviation in an indicated, or regulated, flow rate for variations in fluid viscosity on the order of x20.