GB2247744A

GB2247744A - Flow guidance and control device

Info

Publication number: GB2247744A
Application number: GB9116718A
Authority: GB
Inventors: Erwin Schulze
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-08-11
Filing date: 1991-08-02
Publication date: 1992-03-11
Anticipated expiration: 2011-08-02
Also published as: GB2247744B; FR2665750A1; DE4025588C1; GB9116718D0

Description

FLOW GUIDANCE AND CONTROL DEVICE The present invention relates to a flow

guidance and control device, and has particular reference to a device for reduction in the kinetic energy of a mixture of a gas and solid matter led through a duct into a space, such as a mixture of air and coal dust into the 5 combustion chamber of a boiler.

The fuel for a large boiler plant is usually fed to the boiler in form of a mixture of air and coal dust. For this purpose, several ducts starting out from one plane are introduced, one above the other, into the boiler. Due to the different duct lengths that result and also the different co-efficients of friction in the ducts, there are different entry speeds for the mixture of air and coal dust entering the combustion chamber. It is known that different entry speeds are unlikely to promote a combustion which is low in nitrous oxide. Accordingly, it has been attempted to match the kinetic energy of the shorter ducts to the longest duct by means of slides introduced into the ducts, to that the exit speed of the mixtures of air and coal dust will be equal over all of the ducts.

However, it is disadvantageous in the use of such slides that the flow of the mixture of air and solid matter is disturbed in such a manner that the abrasive property of the coal dust causes the ducts to wear out particularly quickly.

There is thus a need for flow guidance and control means by which the energy in a duct can be reduced without the flow being disturbed in such a manner that the wear in the duct is increased.

If possible, wear in the duct should be reduced.

According to the present invention there is provided a flow guidance and control device comprising a duct for conducting a mixture of a gas and solid matter and flow guidance and control means arranged in the duct to reduce the kinetic energy of the mixture when flowing therethrough and comprising respective pluralities of flow guidance and control elements disposed opposite and at a spacing from each other.

Preferably, some of the elements are arranged to be displaceable in radial direction in the duct. By means of the arrangement of the elements the flow of. a mixture of air and coal dust, even in a bend, may be kept away from the wall of the duct. This is because a carrier flow, which is substantially free of solid substances, forms in the region between the duct wall and the flow profile of the mixture of air and coal dust. Due to the preferred adjustability of a part of the elements, the cross-sectional area available for the throughput of the mixture in the duct can be varied so that, in the case of a number of such ducts leading into a combustion chamber, the entry speed of the mixture into the chamber is the same for all ducts.

For the further reduction in the cross-sectional area of theduct, which can be constructed as a four-cornered tube, the elements which lie opposite one another can interengage or intermesh. Thus has the further advantage, particularly in'the case of a duct with a bend, that the mixture flow is split- up and the individual currents resulting from the splitting-up are thinner and thus can be guided around a bend more easily than would be the -case for a more voluminous flow.

z The displaceability of the elements can be achieved by arranging the elements on a carrier plate which is mounted to be pivotable in the duct.

It has proved that the formtion of the carrier flow is enhanced if the stationary elements are concave towards the flow entry and flow exit ends and if the movable elements are concave towards the flow entry end and convex towards the flow exit end.

Preferably the movable elements Are shorter in their axial extent than the elements which are fixed in the duct. For equalisation of the length of the stationary and movable elements, a respective complementing element, which can be concave towards the flow entry end and towards the flow exit end, can be arranged downstream of each of the movable elements.

It has also been found out that the carrier flow, which forms between the individual elements and which is substantially free of solid substances, is disturbed least by a reduction in cross-section if the elements each have a curvature extending in axial direction towards the duct centre line. For preference, the elements which are disposed opposite one another have curvatures in opposite direction.

In a particularly advantageous embodiment, the stationary elements are each constructed in three parts and with a out-line of the free edge in the duct axial direction, wherein the height of the element increases continuously along a line in the first part, a concave curvature extending in axial direction adjoins thereat in the second part, and the line of the free edge extends parallel to the duct centre line in the third part. Correspondingly, the movable z J elements are also each constructed in three parts, wherein the height of the element increases continuously along a line in the first part, a convex curvature extending in axial direction adjoins thereat in the second part, and the height of.the element is reduced along the outline of a curve adjoining thereat. In this case, the height towards the flow exit corresponds to about the height of the associated complementing - element, the height of the complementing element being substantially constant over its length. By- virtue of this construction of the elements, a continuous reduction in cross- sectional area is achieved. Such a continuous reduction in crosssectional area over a greater length of the duct may avoid disturbance of the carrier flow in such a manner that the mixture of air and coal dust conveyed in the duct comes into contact with the duct wall.

1 The device can be, in one preferred embodiment, a compensator.

In another embodiment the duct incorporates a bend. In that case, the fixed elements can be constructed to be concavely curved towards the flow entry end and convexly curved towards the flow exitend. The movable elements, thereagainst, can be constructed to be convex towards the entry end and concave towards the exit end. It has proved that the wear in the duct bend and in the flow region may be permanently reduced by this construction of the elements, because the mixture of air and coal dust does not come into contact with the duct wall. Once again, a carrier flow substantially free of solid substances forms in the region between the duct wall and the flow profile of the mixture.

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For preference, the stationary elements have a height which is greater than the spacing of the duct wall from the duct centre line. The height of the stationary elements towards the flow entry end is preferably less than at the fl.o% exit end, the maximum height expediently being in the centre of curvature. The movable elements extend in radial direction to about the stationary elements.

For constructional reasons, the duct can be angular at the inner side of the bend.

Embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a schematic sectional side elevation of a first device embodying the invention; Fig. 2 is a cross-section, to an enlarged scale, along the line II-II of Fig. 1; Fig. 3 is the detail X of Fig. 1 in enlarged scale; Fig. 4 is a sectional side elevation of a second device embodying the invention; Fig. 5 is a cross-section to an enlarged scale, along the line H-IV in Fig. 4; and Fig. 6 is a view, to an enlarged scale, of a movable baffle of the device of Fig. 4.

Referring now to the drawings, there is shown In Fig. 1 a flow guidance and control device 1 comprising a duct 2 with baffles 3 fixedly arranged therein and baffles 4 arranged to be pivotable in the duct. In addition, complementing baffles 5 are arranged downstream of the baffles 4 to be pivotable in the duct 2.

The stationary baffles 3 have a concavely curved ends towards the duct flow entry and the duct flow exit. Thereagainst, the pivotable baffles 4 h-ave a concavely curved end towards the duct flow entry, but a convexly curved end towards the duct flow exit. Each complementing baffle 5 has a concavely -curved end towards both the flow entry and the flow exit.

The axial outline of each of the fixed and pivotable baffles is divided into three parts (1, 11, 111). The fixed baffles each have a height increasing continuously along a line in the first part I. In the directly adjoining second part II, the profile is that of a concave curvature extending in axial direction. In the third part III, the outline extends along a line parallel to the centre line of the duct. In the case of the pivotable baffles, the height also increases continuously along the line in the first part I.

Adjoining thereat in the second part II is a convex curvature extending in axial direction. Finally, the height of the baffles in the adjoining third part III is reduced and ends in a straight 'line. The height towards the flow exit of the pivotable baffle corresponds in to the height of the associated complementing baffle 5, which height is constant over the entire length.

The baffles 4, which are pivotable in radial direction, are for this purpose arranged on a carrier plate 6, which is mounted to be pivotable in the duct (Fig. 3). The carrier plate 6 is fastened to an axle 7, which is rotatably located in a bearing shell 8 in the wal 1 of the duct 2. The displacement of the plate 6 in radial c 1 direction is effected by way of a piston-cylinder drive 7.

The meshing interengagement of the individual baffles 3 and 4 is evident from Fig. 2.

Fig. 4 shows an embodiment in which the device comprises a duct 9 with a bend. The flow direction in the duct is indicated by an arrow Z. The duct wall, which is constructed to be four-cornered, is denoted by 9b and baffles arranged to be statiionary in the duct are denoted by 10. Baffles which are arranged to be movable in the duct in the region of the bend are denoted by 11. The movable baffles 11, which have a convex leading edge 11a and a concave trailing edge 11b, are arranged on a carrier plate 12, which is mounted on an axle 13 to be pivotable in the duct wall gb. The stationary baffles 10 have a concave leading edge 10a towards the duct flow entry and a convex trailing edge 10b towards the duct flow exit. The fixed baffles 11 have their maximum height in the region of the centre of curvature 10c of the bend. At its inward side, the bend is angular for constructional reasons.

The meshing interengagement of the movable baffles 11 and fixed baffles 10 is evident in Fig. 5.

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Claims

1. A flow guidance and control device comprising a duct for conducting a mixture of a gas and--solid matter and flow guidance and control means arranged in the duct to reduce the kinetic energy of the mixture when flowing therethrough and comprising respective pluralities of flow guidance and control elements disposed opposite and at a spacing from each other.

2. A device as claimed in claim 1, wherein a group of the elements is arranged to be movable inwardly of the duct.

3. A device as claimed in claim 2, wherein the elements of each 10 plurality mesh with those of the respective opposite plurality.

4. A device as claimed in either claim 1 or claim 2, wherein the duct is four-cornered in cross-section.

5. A device as claimed in any of claims 2 to 4, wherein the movable elements are mounted on a plate which is pivotable in the duct.

6. A device as claimed in any one of claims 2 to 5, wherein the elements other than said movable elements have concave ends facing each of an inlet end and outlet end of the duct and the movable elements have concave ends facing 'the inlet end of the duct and convex ends facing the outlet end of the duct.

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7. A device as claimed in claim 6, wherein the movable elements are shorter in the axial direction of the duct than said other elements.

8. A device as claimed in claim 7, comprising a respective additional flow guidance and control element arranged downstream of each of the movable elements and of such length in the axial direction of the duct that the combined lengths in that direction of each movable element and associated additional element is substantially equal to the length of each of said other elements, the additional elements having concave ends facing the inlet end of the duct and convex ends-facing the outlet end of the duct.

9. A device as claimed in any one of claims 2 to 8, wherein each of the elements has a portion which is curved in the axial direction of the duct.

10. A device as claimed in claim 9, wherein the 'curved portions of the elements of each plurality curve in opposite sense to those of the elements of the respective other plurality.

11. A device as claimed in any one of the claims 2 to 5, wherein the elements other than said movable elements each comprise a first end portion continuously increasing in height away from an inlet end of the duct and having a straight edge inclined relative to the duct axis, a centre portion adjoining the first end portion and having a concavely curved free edge, and a second end portion adjoining the centre portion and having a straight free edge substantially parallel to the duct axis.

12. A device as claimed in any one-,of claims 2 to 5 and 11, wherein the movable elements each comprise a first end portion continuously increas ing in height away from an in.let end of the duct and having a straight free edge, a centre portion adjoining the first end portion and having a convexly curved free edge, and a second end portion adjoining the centre portion and of reduced height.

13. A device as claimed in claim 8, wherein each of the additional elements is of substantially constant height and of substantially the same height as the associated movable element.

14. A device as claimed in any one of the preceding claims, where the device is a compensator.

15. A device as claimed in any one of claims 1 to 5, wherein the duct is bent and the elements other than said movable elements have concave ends facing an inlet end of the duct and convex ends facing an outlet end of the duct.

16. A device as claimed in claim 15, wherein the movable elements have convex ends facing the inlet end of the duct and concave ends facing the outlet end of the duct.

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17. A device as claimed in claim 15 of claim 16, wherein the height of each of said other elements is greater than half the width of the duct in the plane of the element.

18. A device as claimed in any one of claims 15 to 17, wherein the 5 duct bend is angular at the inner side thereof.

19. A device as claimed in any one of claims 15 to 18, wherein each of said other elements has its maximum height at the centre of the bend.

20. A device as claimed in any one of claims-15 to 19 when appended to claim 2, wherein said movable -elements are those of one of the pluralities and extend in the duct substantially up to the elements of the other plurality.

21. A device as claimed in claim 17, wheein the height of each of said other elements is lower at the end facing the inlet end of the duct than at the end facing the outlet end of the duct.

22. A flow guidance and control device substantially as hereinbefore described with reference to Figs. 1 to 3 of the accompanying drawings.

23. A flow guidance and control device substantially as hereinbefore described with reference to Figs. 4 to 6 of the accompanying drawings.

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24. A boiler comprising a combustion chamber and a device as claimed in any one of the preceding claims and arranged to conduct a mixture of air and coal dust into the combustion chamber.

Published 1992 at The Patent Offlce. Concept House. Cardiff Road. Newport. Gwent NP9 M. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Point, CwmfeWach, Cross Keys, Newport. NPI 7HZ. Printed by Multiplex techniques lid. St Mary Cray. Kent.

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