EP1896773A1

EP1896773A1 - Burner

Info

Publication number: EP1896773A1
Application number: EP06778673A
Authority: EP
Inventors: Jean-Claude Pillard
Original assignee: EGCI Pillard
Current assignee: Fives Pillard SA
Priority date: 2005-06-27
Filing date: 2006-06-26
Publication date: 2008-03-12
Also published as: US20090208889A1; FR2887597B1; CN101208559B; US9011141B2; WO2007000512A1; CN101208559A; BRPI0612123A8; BRPI0612123A2; FR2887597A1

Abstract

The invention relates to a burner comprising several substantially concentric channels, one (1) of which is arranges outside of all fuel supply conduits and is delimited by two pipes (2, 3), whose axes (4) are placed in a parallel position and which are movable with respect to each other. According to said invention, diverting members (6) used for imparting a tangential component (7) to a fluid flowing in the channel (1) are carried by the first pipe (2) and are fixed thereto, the second pipe (3) comprises a drive portion (9) for driving the fluid outside the diverting members (6) and the angle of tangential deviation of the fluid at the downstream end (8) of the channel (1) depends on the axial position of the second pipe (3) with respect to the first pipe (2).

Description

BURNER

The present invention relates to an annular pipe and a burner comprising such a pipe, the burner being a primary air burner, a total air burner, a gas burner ...

An annular pipe of the type delimited by two tubes whose axes are parallel and which are axially movable relative to each other is known, a first tube carrying deflection members adapted to impart a tangential component to a moving fluid. in driving.

Such a pipe is commonly used in burners, especially in primary air burners such as those described in application EP 967 434. Indeed, in modern burners such as those described in this application, to improve combustion, the fuel supply pipes are surrounded by two peripheral primary air supply pipes generating a vortex flow (or helical flow), one of these pipes having no deflection members so that the air which therein circulates out according to an axial flow, while the other comprises such bodies so that the air flowing therethrough in a rotating flow around the axis of the burner. The quality of the improvement provided by these two peripheral pipes depends on the adjustments that must be made, especially with regard to the primary air flows they provide: on the one hand the total flow of air brought these two peripheral pipes with respect to the flows of the other constituents (fuels and central primary air), and, on the other hand, the ratio of these two peripheral primary air flow rates that modulates the swirling effect. The setting of the two flow rates is particularly delicate and requires the user to be particularly qualified. In addition, because of the presence of two peripheral air supply lines, these burners are particularly heavy, bulky, complex (at the upstream portion of the pipes to allow their supply) and expensive. Moreover, these burners have a relatively large loss of charge because the peripheral primary air rubs against four walls (two per pipe).

A first solution consisted in eliminating the axial flow primary air supply peripheral pipe. However, in this case, it is no longer possible to adjust the importance of the tangential component of the vortex flow.

A second solution was to improve the first solution by decomposing the single peripheral primary air supply pipe into an upstream section (without a deflection member), a downstream section (without a deflection member), and flexible pipes arranged between the two sections and regularly distributed around the axis of the burner. Relative rotation of the two sections causes torsion of the flexible pipes which thus make it possible to confer a greater or lesser tangential component to the fluid at the outlet of the downstream section. The main problem of this solution concerns flexible pipes which are moving and deformable parts in a zone hot, which are subject to wear and rupture, especially when the circulating air is loaded with dust. The present invention aims to provide, on the one hand, a burner offering the same possibility of adjusting the swirling flow as the burners having two peripheral air supply lines, without having the aforementioned drawbacks, and, on the other hand, a annular conduit for having such a burner.

According to the invention, in the annular pipe of the aforementioned type, the second tube is shaped so that the tangential deflection angle of the fluid at the downstream end of the pipe depends on the axial position of the second tube relative to the first.

Thus, according to the invention, for a given flow rate of air flowing in the pipe, it is possible to modify the tangential component of the fluid by a simple relative axial displacement of the two tubes, without the pipe comprising mobile elements by compared to these two tubes. In addition, the axial mobility of the two tubes does not have the disadvantages of the previously proposed flexible tubes.

Other features and advantages will appear in the detailed description of the embodiment given by way of non-limiting example and illustrated in the accompanying drawings.

FIG. 1 is an axial sectional view of the downstream portion of a pipe according to a first embodiment of the present invention, the first tube being in an advanced position; FIG. 2 is a view similar to FIG. the first tube being in a retracted position, 77

FIG. 3 is a view similar to FIG. 1, of a pipe according to a second embodiment of the present invention,

FIG. 4 is a view similar to FIG. 3, the first tube being in a retracted position,

FIG. 5 is a view taken from the downstream part of the first tube,

FIG. 6 is a partial axial sectional view of a portion of the first tube and deflection members, and

Figure 7 is a partial view of a burner in axial section with an annular conduit according to the second embodiment of the present invention.

An annular pipe 1 according to the present invention is delimited by two tubes 2,3 whose axes 4 are parallel (in this case, the two tubes 2,3 are coaxial) and which are movable in the axial direction 5 one compared to each other.

A first tube 2 (in this case the inner tube 2) carries deflection members 6 which are adapted to impart a component in the tangential direction 7 to a fluid moving in the pipe. The second tube 3 (in this case the outer tube 3) is shaped so that the tangential deflection angle of the fluid at the downstream end 8 of the pipe 1 depends on the axial position of the second tube 3 relative to the first 2.

As can be seen in Figures 1 and 2, in the present examples, the second tube 3 comprises a drive portion 9 which is adapted to allow the fluid to be driven out of the deflection members 6, and thus to allow the fluid to have at the end downstream 8 of the pipe 1 substantially the same tangential deflection as its output of the deflection members 6. The change of the tangential deflection angle of the fluid is achieved by the axial displacement of the driving portion 9 relative to the organs bypass 6.

The driving portion 9 is oriented, in the radial direction 10, in the direction of a distance from the first tube 2 for displacement in the axial direction 5 from upstream to downstream (because the second tube 3 is the outer tube, the driving portion 9 is divergent). Here, the driving portion 9 is a conical portion 9.

In the present embodiments, the modification of the tangential deflection angle of the fluid is facilitated by the application of the Coanda effect. More specifically, the second tube 3 is shaped so as to allow a plating of the fluid threads against its wall by Coanda effect. In order to be able to use this effect, in the present embodiments, the half-angle 11 at the top of the cone is less than 15 °. As a result, from the upstream end 12 of the driving portion 9, the fluid follows the wall of the second tube 3 and, in view of its orientation, releases the deflection members 6 of the first tube 2. Thus, as a function of the axial position of the upstream end 12 of the driving portion 9 with respect to the deflection members 6, the fluid acquires a more or less significant tangential component. The deflection members 6 are fixed relative to the first tube 2, and in this case they are formed by channels 6 made by machining (for example, by milling) of the first tube 2. This tube may comprise, for example between 8 and 36 channels 6.

Each channel 6 is delimited by a bottom wall 13 and by two longitudinal walls 14. The bottom wall 13 extends in the axial 5 and tangential directions 7 and, therefore, is cylindrical. The two longitudinal walls 14 extend in the axial 5 and radial 10 directions and they have, with respect to the axis 4 of the first tube 2, a tangential deflection angle 15 as can be seen in FIG.

In order to have at the outlet of the pipe 1 a fluid having a good swirling behavior in the case where it is used in a burner, for each channel 6, at any point in the axial direction 5, the angle of the tangential deflection 15 is less than 45 °.

In order to be able to have a large tangential flow amplitude at the outlet of the pipe 1, for each channel 6, the angle of the tangential deflection 15 at a point taken along the axial direction 5 varies as a function of the distance from this point with the downstream end 16 of the first tube 2. And more specifically, for each channel 6, the tangential deflection angle 15 increases from the upstream end 17 of the channel 6 to its downstream end 18. As a result, depending on the position of the driving portion 9 with respect to the channel 6, it is possible to very simply modify the tangential component of the fluid leaving the pipe, the more this fluid has been released from the channels 6 upstream, the lower its tangential component ( and corresponds to the tangential deflection angle of the channel 6 at the axial point where the fluid leaves the latter (the channel 6 being "open" in the direction of the second tube 3). each channel 6 so that its tangential deflection angle 15 is zero (or substantially zero) at its upstream end 17, it is possible to have, at the outlet of the pipe 1, an axial flow fluid. As can be seen in Figures 1 to 4, the longitudinal walls 14 have, in the radial direction 10 a dimension such that their free radial end 19 does not rub against the second tube 3, Thus, the radial distance between the radial end free 19 longitudinal walls 14 and the portion 20 of the second tube 3 upstream of the upstream end 12 of the drive portion 9 is at least equal to 0.5 mm.

It is understood that, due to the application of the Coanda effect, regardless of the relative axial position of the two tubes 2, 3, from the upstream end 12 of the driving portion 9, with respect to the part of the fluid hitherto canalized (the part of the fluid which upstream of the upstream end 12 of the drive portion 9, was between the longitudinal walls 14), a portion (the portion closest to the free radial end 19) is released from the channel 6, and this portion becomes increasingly important as the fluid along the driving portion 9, until reaching an axial release point 20 where substantially the all of the part of the fluid hitherto channeled when the radial distance between the driving portion 9 of the free radial end 19 reaches the radial dimension of the longitudinal walls 14. Consequently, the part of the channels 6 which is downstream of the axial point of release 20 is inuti (for a relative axial position of the two tubes 2,3 given). In the first example illustrated in Figures 1 and 2, for each channel 6, the bottom surface 13 has a downstream end portion 21 which is oriented, in the radial direction 10, in the direction of a coming together of the second tube 3 for a displacement in the axial direction 5 from upstream to downstream. Here, this orientation is such that at the downstream end 18 of the channels 6, the bottom wall 13 reaches the free radial end 19 of the longitudinal walls 14 so that the radial dimension of the longitudinal walls is zero.

In the second example illustrated in FIGS. 3 and 4, each channel 6 opens at the downstream end 16 of the first tube 2 (which is then also the downstream end 18 of the channels 6), as illustrated elsewhere in FIG. elsewhere, the radial distance between the free radial end 19 of the longitudinal walls 14 and the portion 20 of the second tube 3 upstream of the upstream end 12 of the driving portion 9 may be relatively large (both in absolute terms). , for example at least equal to 10 mm, only relative to the radial dimension of the longitudinal walls). Therefore, it is possible to have, at the outlet of the pipe 1, a portion of the fluid whose flow is axial, regardless of the relative axial position of the two tubes 2,3. This part is that which has not been channeled (or which has been channeled over the axial portion of the channels 6 whose tangential deflection angle is zero), ie the portion of the fluid which upstream of the the upstream end 12 of the drive portion 9, was between the second tube 3 and the free radial end 19 of the longitudinal walls 14. In addition, because of the variation of the tangential deflection angle along the axis 4 of the first tube 2, if the spacing between the two longitudinal walls 14 of a channel 6 is constant over the entire length of the In channel 6, the flow rate of the fluid at the outlet of the channels 6 varies as a function of the relative axial position of the two tubes 2, 3 (as a function of the tangential deflection angle at the outlet of the channel 6). Also, in order to have a constant flow regardless of the relative axial position of the two tubes 2,3, as can be seen in Figure 5, each channel 6 is configured so that the spacing between its two longitudinal walls 14 at a point taken along the axis 4 of the first tube 2, varies according to the tangential deflection angle 15 at this point so as to have a useful section 22 for output of the channel 6 at the upstream end 12 of the portion 9 substantially constant drive. The useful section 22 being equal to the product of the cross section 23 by the cosine of the tangential deflection angle 15. In addition, in order to have at the outlet of the pipe 1 a flow that does not deviate with respect to the axis 4 of the pipe 1 (in this case, the second tube 3 being the outer tube, so that the flow is not divergent), the second tube 3 comprises a cylindrical portion 24 extending the downstream end 25 of the drive portion 9. Preferably, so that this portion has a sufficient rectifying effect, its length is at least greater than three times the distance separating the two tubes 2,3 at this downstream cylindrical portion 24.

Such a pipe 1 can be integrated in any burner comprising several pipes substantially concentric because it makes it possible to vary in a very simple manner the tangential component of the output fluid as a function of the relative axial position of the two tubes 2,3 delimiting this pipe 1, and this variation may not cause a change in flow rate in the case where the deflection members 6 are in a suitable configuration.

The burner may be of the partial air type. It may for example comprise at least four substantially coaxial pipes, these four pipes comprising a central fuel supply pipe, a central primary air supply pipe surrounding the central fuel supply pipe, a peripheral feed pipe. in fuel surrounding the central primary air supply pipe, and a primary air supply annular pipe according to the present invention located outside all the fuel supply pipes, the burner having a central stabilizer which covers the outlet of the primary central air supply pipe, and which has openings through which the primary air coming from the central duct supplying primary air. In fact, this burner corresponds to that described in application EP 967 434, the pipe according to the present invention replacing the two external pipes.

It may also comprise at least four substantially coaxial lines, these four lines comprising a central fuel supply pipe, a pulverized solid fuel supply annular pipe surrounding the pipe a fuel supply unit, a central annular primary air supply line surrounding the pulverized solid fuel supply line, and a primary annular primary air supply line according to the present invention which surrounds the central annular line. primary air supply unit, the burner comprising a central stabilizer, placed at the outlet of the annular central primary air supply pipe, and which has openings through which the primary air coming from the central duct primary air supply. This burner then corresponds to that described in application EP 1 445 535, the pipe according to the present invention replacing the two external pipes.

The burner may also be of the total air type, the annular primary air supply pipe according to the present invention being surrounded by at least one secondary air supply line. The burner may also be of the gas type comprising at least two substantially coaxial conduits, both of which comprise a peripheral annular gas supply line according to the present invention which surrounds the other conduit. The present invention is not limited to the embodiment previously described.

It would thus be possible for the first tube (that carrying the deflection members) to be the outer tube, the second tube then being the inner tube. It would be possible for the channels to be made by fixing longitudinal walls (for example by welding) to the first tube.

Claims

Burner comprising a plurality of substantially concentric pipes, one (1) of which, located outside all fuel supply pipes, is delimited by two tubes (2, 3) whose axes (4) are parallel and which are axially movable (5) relative to one another, characterized in that deflection members (6) adapted to impart a tangential component (7) to a fluid moving in the pipe (1) are carried by a first tube (2) and are fixed relative to the latter, the second tube (3) comprising a drive portion (9) adapted to allow the fluid to be driven out of the deflection members (6), tangential deflection angle of the fluid at the downstream end (8) of the pipe (1) depending on the axial position of the second tube (3) relative to the first (2).

2. Burner according to claim 1, characterized in that the second tube (3) is shaped to allow a plating of the fluid threads against its wall by Coanda effect.

Burner according to claim 2, characterized in that the drive portion (9) is oriented, in the radial direction (10), in the direction of a distance from the first tube (2) for movement in the direction axial (5) from upstream to downstream.

4. Burner according to claim 3, characterized in that the driving portion (9) is a conical portion (9), the half angle (11) at the top of the cone being less than 15 °.

5. Burner according to claim 3 or 4, characterized in that the second tube (3) comprises a cylindrical portion (24) extending the downstream end (25) of the driving portion (9).

6. Burner according to one of claims 1 to 5, characterized in that the deflection members (6) are formed by channels (6), each channel (6) being delimited, on the one hand, by a wall of base (13), and on the other hand, two longitudinal walls (14) which extend in the axial (5) and radial (10) directions and have, with respect to the axis (4) of the first tube ( 2), a tangential deflection (15).

7. Burner according to claim 6, characterized in that, for each channel (6), the angle of the tangential deflection (15) is substantially zero at its upstream end (17).

Burner according to Claim 6 or 7, characterized in that, for each channel (6), the angle of the tangential deflection (15) increases from the upstream end (17) of the channel (6) to its downstream end. (18).

9. Burner according to one of claims 6 to 8, characterized in that, for each channel (6), at any point in the axial direction (5), the angle of the tangential deflection (15) is less than 45 °.

10. Burner according to one of claims 6 to 9, characterized in that each channel (6) opens at the downstream end (16) of the first tube (2).

11. Burner according to one of claims 6 to 9, characterized in that, for each channel (6), the bottom surface (13) of its downstream end portion (21) is oriented in the radial direction (10). , in the sense of a approaching the second tube (3) for displacement in the axial direction (5) from upstream to downstream.

12. Burner according to one of claims 6 to 11, characterized in that, for the part of the channels (6) upstream of the upstream end (12) of the drive portion (9), the radial dimension of the longitudinal walls (14) is such that their free radial end (19) is at a distance of between 0.5 and 10 mm from the second tube (3).

13. Burner according to one of claims 6 to 12, characterized in that, for each channel, the spacing between the two longitudinal walls (14) at a point varies as a function of the tangential deflection angle (15) in this point so as to have a useful output section of the channel (6) at the upstream end (12) of the substantially constant drive portion (9) regardless of the relative axial position of the two tubes (2,3) .