Low flow fluid controller apparatus and system

A fluid flow control apparatus adapted for fluid flow therethrough in a flow region extending along a flow axis and laterally bounded by a tubular inward facing surface of a support structure from an upstream end to a downstream end of the flow region, comprising:

• A. a low flow blade set, and a high flow blade set disposed in the support structure, wherein the low flow blade set includes at least one blade and the high flow blade set includes at least one blade,
• wherein edges of the respective blades and the inward facing surface define an array of one or more adjustable cross-section area variable apertures characterized by area Ao within the bounds of the inward facing surface and define fluid flow paths therethrough between an upstream portion of the flow region between the blades and the upstream end and a downstream portion of the fluid region between the blades and the downstream end, wherein Ao is representative an aggregate of areas of cross-sections of the apertures of the array of apertures normal to fluid flow paths passing through the apertures, and
• wherein the blades of the low flow blade set and the high flow blade set are each pivotable about an associated one of a set of mutually parallel pivot axes, between:
• i. closed angular orientations where edges of adjacent blades overlap and are adjacent, and edges of blades which are not adjacent to other blades are adjacent to the inward facing surface, with no portion of the fluid flow path extending past (a) the overlapping edges of the blades of the blade sets and (b) non-overlapping edges of blades which are adjacent to the inward facing surface;
• and
• ii. open angular orientations angularly offset from the closed orientations thereby establishing a portion of the fluid flow path extending past the blades of the blade sets;
• B. an actuator assembly including at least one actuator;
• C. a linkage assembly having at least one end effector coupling the blades of the respective blade sets to the at least one actuator of the actuator assembly;
• and
• D. a controller responsive to:
• i. an upstream pressure upstream of the low flow blade set and the high flow blade set and a downstream pressure downstream of the low flow blade set and the high flow blade set, to generate a pressure difference signal representative of a differential pressure ΔP along the flow axis across the low flow blade set and the high flow blade set,
• ii. the actuator assembly to generate an aperture signal representative of the area Ao of the respective apertures normal to flow paths of fluid flowing therethrough,
• iii. the pressure difference signal, and the aperture signal to generate a damper area control signal, and apply the damper area control signal to the actuator assembly, in a closed loop manner,
• wherein the actuator assembly is adapted by way of the at least one end effector to independently control the angular orientations of at least one of the blades of each of the respective blade sets
• whereby fluid flows from the upstream portion of the flow region, through the array of apertures and to the downstream portion of the flow region, wherein the fluid flowing between the array of apertures and the downstream portion, is characterized by a corresponding array of vena contractae having an aggregate cross section area Ac normal to the fluid flow therethrough, where Ac <Ao , and Ac is less than the aggregate cross section area normal to fluid flow elsewhere between the array of apertures and the downstream portion,
• thereby establishing a contraction coefficient C for aggregate fluid flow along the fluid flow path past the blades of the respective blade sets through the array of apertures wherein C =Ac/Ao where Ac is representative an aggregate of cross section areas of the vena contractae of fluid flowing through the respective apertures of the array of apertures, and
• whereby the controller is responsive to contraction coefficient C, the aperture signal and the pressure signal, to regulate the variable apertures over time in a closed loop manner so that a set point is attained.