Variable aperture fluid flow assembly

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

A. a damper assembly adapted for disposition in the flow region along the fluid flow axis having a first side facing the upstream end and a second side opposite the first side and facing the downstream end, and defining an array of one or more adjustable cross-section area variable apertures characterized by an aggregate area A o within the bounds of the inward facing surface and defining fluid flow paths therethrough between an upstream portion of the flow region between the first side and the upstream end and a downstream portion of the fluid region between the second side and the downstream end, wherein A o is representative of an aggregate of areas of cross-sections of the apertures of the array of apertures normal to fluid flow paths passing through the apertures of the array of apertures,

B. an upstream sensor adapted for sensing upstream pressure at an upstream pressure sense locus in an upstream portion of the flow region displaced by a distal distance in the direction of the flow axis from the first side,

C. a downstream sensor adapted for sensing downstream pressure in at least one downstream pressure sense locus in a downstream portion of the flow region displaced by a proximal distance in the direction of the flow axis from the second side, wherein the distal distance is greater than the proximal distance, and outside of perimeters of apertures of the array of apertures,

D. an actuator assembly adapted to adjust the cross-section areas of respective variable apertures of the array in response to a damper area control signal applied thereto, and

E. a flow control processor responsive to:

i. the sensed upstream pressure and sensed downstream pressure to generate a pressure difference signal representative of a differential pressure ΔP along the flow axis across the damper assembly,

ii. the actuator assembly to generate an aperture signal representative of the area of the respective apertures normal to flow paths of fluid flowing therethrough,

iii. the pressure difference signal, and the aperture signal to generate the damper area control signal, and apply the damper area control signal to the actuator assembly, thereby adjustably controlling the cross-section areas of the respective variable apertures of the array,

whereby fluid flows from the upstream end, through the array of apertures characterized by aggregate area A o normal to the flow therethrough, and to the downstream end,

whereby the flow control processor regulates the variable apertures of the array of apertures over time so that a set point is attained.

2. A fluid flow assembly according to claim 1 ,

wherein the damper area control signal is applied to the actuator assembly in a closed loop manner, and

whereby the fluid flowing between the array of apertures and the downstream end is characterized by a corresponding array of venae contractae having an aggregate cross section area A c normal to the fluid flow therethrough, where A c <A o , and A c is less than the aggregate cross section area normal to fluid flow outside the venae contractae and between the array of apertures and the downstream end, thereby establishing a contraction coefficient C, wherein

C=A c /A o

whereby the flow control processor is responsive to contraction coefficient C, the aperture signal and the pressure difference signal, to regulate the cross-section areas of apertures of the array of apertures over time in a closed loop manner so that the set point is attained.

3. A fluid flow assembly according to claim 2 , wherein the upstream sensor is disposed upstream of portions of the flow region between the upstream pressure sense locus and the first side of the damper assembly.

4. A fluid flow assembly according to claim 2 wherein:

i. the sensed upstream pressure is a total pressure TP upstream at the upstream pressure sense locus, and

ii. the sensed downstream stream pressure is a static pressure SP downstream at the at least one downstream pressure sense locus.

5. A fluid flow assembly according to claim 4 wherein ΔP=TP upstream −SP downstream .

6. A fluid flow assembly according to claim 5 wherein C is a flow coefficient C F corresponding to:

C

F

=

A

c

A

o

=

c

1

-

(

1

-

c

)

⁢

(

A

o

A

d

)

2

wherein

i. A d is representative of the cross-section area of the flow region normal to the flow axis and adjacent to the damper assembly within the bounds of the inward facing surface, and

ii. c is representative of, for an inviscid fluid flowing through an aperture in a plate in response to a pressure differential across the plate, a ratio of an area normal to a vena contracta of fluid flowing through the aperture, to an area of the aperture normal to fluid flow through the aperture.

7. A fluid flow assembly according to claim 6 further comprising a flow rate computation processor adapted to determine the flow rate Q of the fluid flowing through the downstream region, wherein

Q

=

(

A

c

A

o

)

⁢

A

o

⁢

2

⁢

Δ

⁢

P

ρ

=

C

F

⁢

A

o

⁢

2

⁢

Δ

⁢

P

ρ

where

i. ρ is representative of the density of the fluid, and

ii. ΔP is representative of the differential pressure along the flow axis across the damper assembly.

8. A fluid flow assembly according to claim 4 wherein there are at least two downstream pressure sense loci and the at least two downstream pressure sense loci are contiguous.

9. A fluid flow assembly according to claim 2 , wherein:

i. the sensed upstream pressure is a static pressure SP upstream at the upstream pressure sense locus, and

ii. the sensed downstream stream pressure is a static pressure SP downstream at the at least one downstream pressure sense locus.

10. A fluid flow assembly according to claim 9 wherein ΔP=SP upstream −SP downstream .

11. A fluid flow assembly according to claim 10 wherein fluid flow through the array of apertures is characterized by a discharge coefficient C d corresponding to:

C

d

=

c

[

1

-

(

1

-

c

)

2

⁢

(

A

o

A

d

)

2

]

wherein

i. A d is representative of the cross-section area of the flow region normal to the flow axis and adjacent to the damper assembly within the bounds of the inward facing surface, and

ii. c is representative of, for an inviscid fluid flowing through an aperture in a plate in response to a pressure differential across the plate, a ratio of an area normal to a vena contracta of fluid flowing through the aperture, to an area of the aperture normal to fluid flow through the aperture.

12. A fluid flow assembly according to claim 11 further comprising a flow rate computation processor adapted to determine a flow rate Q of fluid flowing through the downstream region, wherein

Q

=

C

d

⁢

A

o

[

1

-

(

A

o

A

d

)

2

]

⁢

2

⁢

Δ

⁢

P

ρ

where

i. ρ is representative of the density of the fluid, and

ii. ΔP is representative of the differential pressure along the flow axis across the damper assembly.

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

A. a damper assembly adapted for disposition in the flow region along the fluid flow axis having a first side facing the upstream end and a second side opposite the first side and facing the downstream end, and defining an array of one or more adjustable cross-section area variable apertures characterized by an aggregate area A o within the bounds of the inward facing surface and defining fluid flow paths therethrough between an upstream portion of the flow region between the first side and the upstream end and a downstream portion of the fluid region between the second side and the downstream end, wherein A o is representative of an aggregate of areas of cross-sections of the apertures of the array of apertures normal to fluid flow paths passing through the apertures,

B. an upstream sensor adapted for sensing upstream pressure at an upstream pressure sense locus in an upstream portion of the flow region displaced by a distal distance in the direction of the flow axis from the first side,

C. a downstream sensor adapted for sensing downstream pressure in at least one downstream pressure sense locus in a downstream portion of the flow region displaced by a proximal distance in the direction of the flow axis from the second side, wherein the distal distance is greater than the proximal distance, and outside of perimeters of apertures of the array of apertures,

D. a net pressure source assembly adapted to effect an adjustable net fluid pressure across an upstream point at or upstream of the upstream pressure sense locus and a downstream point at or downstream of the downstream pressure sense locus, in response to a net pressure control signal applied thereto,

E. an actuator assembly adapted to an actuator assembly adapted to adjust the cross-section areas of respective variable apertures of the array in response to a damper area control signal applied thereto, and

F. a flow control processor responsive to:

i. the sensed upstream pressure and sensed downstream pressure to generate a pressure difference signal representative of a differential pressure ΔP along the flow axis across the damper assembly,

ii. the net pressure source assembly to generate the net pressure control signal representative of a differential pressure across the upstream point and the downstream point,

iii. the actuator assembly to generate an aperture signal representative of the area of the respective apertures normal to flow paths of fluid flowing therethrough,

iv. the pressure difference signal, and the aperture signal to generate the damper area control signal, and apply the damper area control signal to the actuator assembly, thereby adjustably controlling the cross-section areas of the respective variable apertures of the array,

whereby fluid flows from the upstream end, through the array of apertures characterized by aggregate area A o normal to the flow therethrough, and to the downstream end,

whereby the flow control processor regulates the variable apertures over time so that a set point is attained.

14. A fluid flow assembly according to claim 13 ,

wherein the damper area control signal is applied to the actuator assembly, in a closed loop manner, and

whereby the fluid flowing between the array of apertures and the downstream end, is end is characterized by a corresponding array of venae contractae having an aggregate cross section area A c normal to the fluid flow therethrough, where A c <A o , and A c is less than the aggregate cross section area normal to fluid flow outside the venae contractae and between the array of apertures and the downstream end, thereby establishing a contraction coefficient C, wherein

C=A c /A o

whereby the flow control processor is responsive to contraction coefficient C, the aperture signal and the pressure difference signal, to regulate the cross-section areas of the apertures of the array of apertures over time in a closed loop manner so that the set point is attained.

15. A fluid flow assembly according to claim 14 wherein

the upstream sensor is disposed upstream of portions of the flow region between the upstream pressure sense locus and the first side of the damper assembly.

16. A fluid flow assembly according to claim 14 , wherein:

i. the sensed upstream pressure is a total pressure TP upstream at the upstream pressure sense locus, and

ii. the sensed downstream stream pressure is a static pressure SP downstream at the at least one downstream pressure sense locus.

17. A fluid flow assembly according to claim 16 wherein ΔP=TP upstream −SP downstream .

18. A fluid flow assembly according to claim 17 wherein C is a flow coefficient C F corresponding to:

C

F

=

A

c

A

o

=

c

1

-

(

1

-

c

)

⁢

(

A

o

A

d

)

2

wherein

i. A d is representative of the cross-section area of the flow region normal to the flow axis and adjacent to the damper assembly within the bounds of the inward facing surface, and

ii. c is representative of, for an inviscid fluid flowing through an aperture in a plate in response to a pressure differential across the plate, a ratio of an area normal to a vena contracta of fluid flowing through the aperture, to an area of the aperture normal to fluid flow through the aperture.

19. A fluid flow assembly according to claim 18 , further comprising a flow rate computation processor adapted to determine flow rate Q of the fluid flowing through the downstream region, wherein

Q

=

(

A

c

A

o

)

⁢

A

o

⁢

2

⁢

Δ

⁢

P

ρ

=

C

F

⁢

A

o

⁢

2

⁢

Δ

⁢

P

ρ

where

i. ρ is representative of the density of the fluid, and

ii. ΔP is representative of the differential pressure along the flow axis across the damper assembly.

20. A fluid flow assembly according to claim 16 wherein there are at least two downstream pressure sense loci and the at least two downstream pressure sense loci are contiguous.

21. A fluid flow assembly according to claim 14 , wherein:

i. the sensed upstream pressure is a static pressure SP upstream at the upstream pressure sense locus, and

ii. the sensed downstream stream pressure is a static pressure SP downstream at the at least one downstream pressure sense locus.

22. A fluid flow assembly according to claim 21 wherein ΔP=SP upstream −SP downstream .

23. A fluid flow assembly according to claim 22 wherein fluid flow through the array of apertures is characterized by a discharge coefficient C d corresponding to:

C

d

=

c

[

1

-

(

1

-

c

)

2

⁢

(

A

o

A

d

)

2

]

wherein

i. A d is representative of the cross-section area of the flow region normal to the flow axis and adjacent to the damper assembly within the bounds of the inward facing surface, and

ii. c is representative of, for an inviscid fluid flowing through an aperture in a plate in response to a pressure differential across the plate, a ratio of an area normal to a vena contracta of fluid flowing through the aperture, to an area of the aperture normal to fluid flow through the aperture.

24. A fluid flow assembly according to claim 23 further comprising a flow rate computation processor adapted to determine the flow rate Q of fluid flowing through the downstream region, wherein

Q

=

C

d

⁢

A

o

[

1

-

(

A

o

A

d

)

2

]

⁢

2

⁢

Δ

⁢

P

ρ

where

i. ρ is representative of the density of the fluid, and

ii. ΔP is representative of the differential pressure along the flow axis across the damper assembly.