Flow control device

1. A flow control device in a burner for partitioning a fluid flow from a common combustion air supply stream comprising:

an elongate conduit comprising an outer wall and internal pipes defining concentric secondary and tertiary annular flow channels inside the elongate conduit for supplying the combustion air of the burner into at least two delivery streams along an axial direction of the elongate conduit;

an aperture formed in the outer wall, the aperture configured to provide flow inlets for the combustion air into each of the secondary and tertiary annular flow channels, respectively, so that the aperture is common to the flow inlets for both the secondary and tertiary annular flow channels; and

a damper sleeve disposed concentrically around an outer surface of the outer wall and configured to sliding move in the axial direction of the elongate conduit and over a portion of the outer surface of the outer wall at which the aperture is located so as to divide the common combustion air between the secondary and tertiary annular flow channels by selectively restricting flow through each of the flow inlets of the respective secondary and tertiary annular flow channels,

wherein axial sliding movement of the sleeve damper over the aperture simultaneously increases an open area of the flow inlet of one of the annular flow channels and decreases an open area of the flow inlet of the other one of the annular flow channels, so as to partition the common combustion air supply flowing from outside of the elongate conduit into the secondary and tertiary annual flow channels inside the elongate conduit.

2. A flow control device in accordance with claim 1 wherein the flow inlets to the respective secondary and tertiary annular flow channels are longitudinally spaced along the axial direction of the elongate conduit.

3. A flow control device in accordance with claim 1 wherein the sleeve damper is configured such that movement thereof selectively varies flow in manner that is non-linear with movement of the sleeve damper in that the reduction rate reduces as the damper moves to a position where the open area tends to a more restricted condition.

4. A flow control device in accordance with claim 3 wherein the aperture is provided in a plurality, and the apertures taper in size as the closed condition is approached.

5. A flow control device in accordance with claim 4 wherein the sleeve damper is configured to reciprocate longitudinally and each of the apertures comprises an elongate longitudinal slot in the outer wall which is tapered in a transverse direction from a wider extent to a narrower extent in a direction corresponding to the direction of travel of the sleeve damper as it moves to a position where it restricts flow.

6. A flow control device in accordance with claim 4 wherein each of the apertures comprises an elongate longitudinal slot in the outer wall which is tapered in a transverse direction from a wider extent in a direction towards a midpoint of the travel of the damper member to a narrower extent in a direction towards an extreme of travel of the damper member.

7. A flow control device in accordance with claim 1 wherein the elongate conduit is cylindrical and the sleeve damper is cylindrical and movable axially relative to the elongate conduit.

8. A flow control device in accordance with claim 1 wherein a plurality of the apertures is provided for conveying the combustion air into each of the annular flow channels.

9. A flow control device in accordance with claim 8 wherein each of the apertures in the outer wall is identically dimensioned.

10. A flow control device in accordance with claim 9 wherein the apertures are evenly spaced around an entire perimeter of the outer wall.

11. A flow control device in accordance with claim 1 wherein the aperture is triangular, trapezoidal, ogival, elliptical, hemispherical or other continuous curve shaped.

12. A flow control device in accordance with claim 1 wherein the flow inlet to each of the secondary and tertiary annular flow channels is defined by the aperture within the outer wall disposed so that a part of the aperture defines the flow inlet to the secondary annular flow channel and a part of the aperture defines the flow inlet to the tertiary annular flow channel, and the sleeve damper is configured to move in reciprocating manner across and over the aperture so as to selectively proportion flow between the respective parts of the aperture, so as to selectively proportion flow between the secondary and tertiary annular flow channels.

13. A flow control device in accordance with claim 12 wherein the aperture comprises a first tapered portion tapered towards a first end and defining in use the flow inlet to the secondary annular flow channel and a second tapered portion tapered towards a second end and defining in use the flow inlet to the tertiary annular flow channel.

14. A flow control device in accordance with claim 13 wherein the first tapered portion and the second tapered portion are identically shaped and dimensioned.

15. A flow control device in accordance with claim 14 wherein the aperture is an ellipse or other continuous dosed curve with equivalent x, y symmetry.

16. A combustion device comprising a common gas supply means, and a flow control device according to claim 1 .

17. A combustion device in accordance with claim 16 wherein the common gas supply means is a combustion gas and/or overfire gas supply means.

18. A combustion device in accordance with claim 17 wherein the combustion gas and/or overfire gas is supplied to a combustion site defined by the combustion device by the secondary and the tertiary annular flow channels and further comprising a fuel delivery conduit configured to supply fuel to the combustion site defined by the combustion device.

19. A combustion device in accordance with claim 18 comprising a burner for firing fossil fuels.

20. A burner for a combustion apparatus comprising:

an elongate conduit including, within an interior of the elongate conduit, primary channel means defining a primary flow zone for supplying fuel to a combustion site provided longitudinally along the burner,

a combustion gas supply means such as a wind box;

the elongate conduit further including, within the interior of the elongate conduit, secondary channel means defining at least two secondary flow zones each having one or more inlet flow control apertures to receive combustion gas from the combustion gas supply means disposed outside of the elongate conduit and each of the inlet flow control apertures defining a combustion gas flow zone for supplying combustion gas to the combustion site, the secondary flow zones configured so that the inlet flow control apertures to the respective flow zones are spaced on an outer wall of the conduit; and

a common movable flow control damper disposed circumferentially around a perimeter of the outer wall of the conduit and comprising at least one sleeve damper movable along an axial direction of the conduit and over a portion of the outer wall at which the inlet flow control apertures are located so as to partition flow between the inlet flow control apertures of the respective combustion gas flow zones so as to proportion relative flow between the combustion gas flow zones,

wherein axial sliding movement of the sleeve damper over the inlet flow control apertures simultaneously increases an open area of one of the inlet flow control apertures and decreases an open area of another one of the inlet flow control apertures.

21. A combustion device in accordance with claim 20 wherein the primary channel means defines a central flow zone and the secondary channel means are disposed around an outer periphery of the primary channel means defining respective flow zones disposed around the central flow zone.