EP0967437A1 - Improvement to combustion apparatus with several combustion air inlet ducts - Google Patents

Abstract

The burners (6) using liquid or gas fuel with a central conduit (12) to carry primary air. Inside this conduit is a rod (8) carrying fuel and a stabiliser (55) with a screen (55a) enclosing the rod. A second conduit brings secondary comburent round the central conduit. The burner has two sliding cylinders (19,21) supported on an articulated Watt parallelogram structure.

Description

The present invention relates to an improvement made to combustion appliances comprising several transport conduits oxidizer.

The technical sector of the invention is the field of manufacture of burner combustion appliances, such as boilers, hot gas generators, ovens or others.

The present invention applies to combustion appliances using one or more solid and / or powdery fuels, or well fluids, which comprise at least one burner associated with at least two coaxial ducts for transporting gaseous oxidant.

The present invention applies in particular to installations of cogeneration of electrical and thermal energy in which exhaust gases from engines or turbines are heated by one or several burners, being used as oxidizer, then are used to produce steam, hot water or hot gases.

The object of the present invention is to propose a system improved adjustment of the oxidizer flow rate delivered to the burners; the present invention applies to burners equipped with several circuits or oxidizer conduits; in such installations, a conduit central conveys an oxidizer current generally called primary, which surrounds and extends coaxially with the nose of the burner; one or several other annular section conduits extend around the central duct and carry a flow or stream of oxidant said secondary and where appropriate tertiary.

The combination of these different oxidant flows, including the velocity and orientation of the resulting oxidizer jets, exiting into the combustion chamber, must be kept within limits predetermined, allows to realize combustion installations efficient, and makes it possible to control combustion, in particular flame shape and stability, as well as the content of different combustion residues, in particular residues of formula Nox, CO whose training must be limited.

It is generally planned to regulate the oxidant flow circulating in a duct using one or more pivoting registers, for example essentially constituted by a plane flap pivoting according to a central axis contained in the plane of the shutter; this type of register has drawbacks, particularly with regard to its dimensions which are high having regard to the permissible oxidant flow rate, and its poor performance in terms of stability and linearity; in furthermore, these registers do not lend themselves well to a parallel installation of several registers, in order to regulate a gas oxidant flow important and variable.

• le brevet N° FR 1.561.182 (Foyers Turbine) décrit une virole cylindrique suspendue à un rail support par l'intermédiaire d'une suspension à cardan ;
• les documents N° GB 2.136.554 (Volcano) et N° E 128085 (Forney) décrivent des brûleurs équipés de deux registres coulissants suspendus à des rails.

It is also known to use one or two sliding registers for supplying air to a burner:

• Patent No. FR 1,561,182 (Turbine Hearths) describes a cylindrical shell suspended from a support rail by means of a cardanic suspension;
• documents N ° GB 2.136.554 (Volcano) and N ° E 128085 (Forney) describe burners fitted with two sliding registers suspended from rails.

However, these devices have drawbacks: the registers suspended from a rail are liable to jam during their movement due to the eccentric position of the support rail relative to the longitudinal sliding axis; moreover, it has been found that these various systems do not allow a reliable, precise and stable adjustment of the position of the damper, in any (partial) opening position of the duct which they can close; these known devices do not allow effective and precise adjustment of the oxidant flow admitted into each of the burner conduits.
Furthermore, patent N ° FR 2,188,780 (Pillard) describes a sliding damper in which an external ferrule movable relative to a fixed internal ferrule is supported by pivots mounted on Watt parallelograms, ensuring movement (sliding) without no contact or friction; it has also been found in practice that this device does not allow stable and precise regulation of the air flow rate passing through the damper, these registers being used in practice ("all or nothing") to close completely or to open totally an air passage.

Precise, stable and faithful adjustment of the admitted oxidizer flow in each flue of a burner is necessary to ensure on the one hand a need for variable heating power over time, and this in particular for each burner of an equipped combustion appliance several burners supplied by a common conduit for transporting oxidizer, on the other hand to ensure stable combustion in precisely controlling the primary air introduction speeds and secondary in the home, and to limit the formation of residues undesirable (Nox in particular).

The object of the present invention is to provide a burner and a combustion appliance fitted with an improved flow control system oxidizer.

The invention consists in proposing a burner associated with at least two ducts for transporting gaseous oxidant, which comprises at at least two sliding cylindrical registers, to allow adjustment independent of the respective oxidizer flow admitted through openings annular and / or arranged annularly in each of said conduits transport of oxidizer; the burner has a central duct supply of primary oxidant (air), inside which coaxially extend a completed fuel injection pipe by one or more nozzles and a stabilizer comprising a hub forming a screen surrounding the rod, which is set back from the nozzles and is provided with peripheral fins, the burner further comprising a secondary oxidant (air) supply line extending around from the central duct; each register is supported by a structure articulated comprising at least two or three parallelograms of Watt.

The burner according to the invention ensures combustion stable and low pollution for very operating conditions variable and allows full use of flame stability resulting from the stabilization device described in the patent N ° FR 2.122.820, which allows the creation of a fiery toric eddy at the birth of the flame and around it, improving the attachment, ignition and quality of the flame.

Preferably, said cylindrical registers are coaxial, sliding mounted along their common longitudinal axis, and are of substantially identical diameter.

Thanks to the presence of at least two registers, the flow adjustment oxidant circulating and / or admitted into the conduits can, on the one hand be carried out independently for each conduit in order to maintain oxidizer injection rates into the combustion chamber at predetermined values, and can on the other hand be performed more specifically, over a larger range of flow variation, and with variable oxidizer supply pressures.

The idea behind the invention is therefore to use a register with Watt parallelogram for each of the circuits of a fitted burner two separate air circuits, for example to obtain a reduction nitrogen oxide emissions by air staging, or to use turbine gases or ambient air in cogeneration.

A further improvement is to use these registers to adjust the flow rates in each circuit, regulating the position partial opening taking advantage of the fact that the parallelogram of Watt, without friction and without play, allows a precise and faithful adjustment. This adjustment is facilitated by having a grid at the openings perforated or grooved improving the progressiveness of the opening of the passage section.

Optimal performance, in terms of stability and precision adjustment of partial opening of the damper, are obtained by providing a deformable seal ensuring contact between the fixed shell and the movable ferrule in any position of the register; this joint preferably takes the form of a metal broom annular which is engaged in an annular groove of the movable shell, which stiffens it.

Thanks to the cylindrical shape of the registers and the shape or annular arrangement of the inlet orifices of said conduits which they can seal in whole or in part, we can get in the conduits homogeneous distribution of oxidant velocities and / or flows, and consequently obtain a homogeneous injection, according to a symmetry of revolution around the axis common to registers and conduits, different oxidant streams entering the combustion, even when the oxidant (s) are delivered in upstream of the registers by a non-coaxial conduit, in particular by a radial or oblique duct (by reference to said axis of symmetry); these results are particularly easy to achieve with a fixture simple mechanical, robust and stable in all adjustment positions, by providing registers in the form of coaxial cylindrical ferrules sliding along their common axis, which ensure a homogeneous flow in the oxidizer conduits, downstream of the registers, regardless of the degree of openness of the registers.

By providing sliding cylindrical registers with diameters different, we get a compact structure that allows the flow high oxidizer flow, thanks to the larger diameter of the damper external and to the large passage section which it can close; this structure adapted to the equipment of burners each equipped with two or three coaxial oxidant transport conduits, intended for deliver - by nozzles or flaps - balanced oxidizer jets, axial, convergent or divergent, possibly rotating, in the combustion chamber.

The compactness of the assembly can in particular be optimized by providing for a crossing (or overlapping or overlapping) of registers and / or their support, guiding and translational drive, for certain open positions; this recovery can take place in the open position of two registers whose directions of opening movements are opposite.

The compactness of the assembly combining two or three registers (equipping two or three oxidizer conduits associated with a burner) is particularly optimized by providing registers whose diameters are such that the ratio of the diameter of the external register to the diameter of the internal register is less than or equal to 2 (and greater than 1 except in certain cases where the diameters are substantially identical), in particular of the order of 1.3 to 1.6.

By diameter is meant the equivalent diameters of the profile cross section of the register, in case the cross section of oxidizer ducts and their associated registers is not in shape circular, but for example square or rectangular.

Another advantage provided by the invention is that it allows, in a combustion appliance equipped with two (at least) powered burners by combustion by a single duct, to regulate easily, precisely and stably, usually at the same value if it is identical burners, the oxidizer flow delivered to each each burner, and therefore makes it possible to resolve the difficulties inherent in such balancing of oxidizer flows regulated by registers arranged in parallel.

Each register can be fitted with sealing means prohibiting the passage of oxidizer in the closed position (and / or limiting as much as possible the "leakage" rate in this position); these sealing means may include a linked crown or flange (or fixed or integrated) at one longitudinal end of the damper; this crown is able to come into contact with (or press on) fixed crown (or flange) forming part of the structure of the device, in closing position of the register; a metal joint may have or be constituted by said flat crown fixed to the register and extending in a transverse plane (with reference to the longitudinal axis of symmetry of the register); by making this crown in a sheet of thin, in particular of the order of 0.5 to 2 millimeters, this crown may deform slightly when pressed on the fixed crown of the structure, which ensures contact with the other end of the register, along its entire perimeter, with a second wall or crown fixed device, which therefore ensures closure substantially sealed from the register by circumferential contact of its two longitudinal ends with the fixed structure of the device combustion.

According to another preferred embodiment, the structure of the cylindrical damper consists of a thin sheet, in particular of 1 to 3 millimeters, rolled and welded to form a ferrule cylindrical of circular section, which is provided with one or more annular or circumferential reinforcements (or stiffeners), which stiffen the structure of the register, which allows to obtain a light register of simple construction; this reinforcement can be obtained (or constituted) by a fold or circumferential undulation made in the sheet metal of the register.

The presence of the sealing and reinforcement means presents considerable advantages compared to the structure described in the patent FR 2,188,780; the cylindrical structure of these registers ensures a very large passage section, and therefore a low pressure drop.

This structure of multiple sliding registers is particularly suitable for outlet gas heating installations of gas engines or turbines, in cogeneration plants.

In this type of installation, the gases escaping from the heater are heated engine or turbine by causing them to burn; in times of engine or turbine operation, these oxidizing gases are delivered in large quantities to burners at a temperature of the order of 500 ° C; when the engine or turbine stops, the burner is supplied with cold air, in much smaller quantity; the system according the invention allows in this operating mode, by closing of one of the registers, to adapt to these variations in operation.

This device is also suitable for air stage burners in which a first part of the combustion air is injected into the center of the burner, and the other part is injected by nozzles or by a annular space coaxial with the burner, on a diameter of the order of 1.2 to 2 times the diameter of the internal circuit; these burners are intended for reduce nitrogen oxide emissions.

The means of support, guidance and training in movement of each of the sliding cylindrical registers, are constituted by an articulated structure comprising two or three Watt parallelograms, which is preferably actuated by a jack associated with each register, under the control of a control unit, and extends outside and around the movable cylindrical wall of each register; alternatively, this structure is actuated manually.

• deux fourches sensiblement en forme de demi-arc de cercle disposées autour dudit registre et articulées chacune autour de deux pivots tourillonnant sur des axes fixes ;
• deux biellettes articulées reliant entre elles les deux extrémités des fourches situées du même côté du registre ;
• deux pivots diamétralement opposés, supportant ledit registre et placés au milieu desdites biellettes ;
• des moyens pour faire pivoter les deux fourches simultanément autour de leurs pivots et d'au moins un dispositif de guidage du registre formé de deux bras articulés autour de pivots fixes, les extrémités des deux bras étant reliées entre elles par une biellette articulée portant, en son milieu, un pivot fixé à l'extérieur dudit registre.

The deformable parallelogram structure linked to the cylindrical register by articulations (or pivots), is particularly suitable for supporting the register exposed to dust and soot; as described in patent N ° FR 2,188,780, the structure essentially consists of:

• two forks substantially in the form of a half-arc arranged around said register and each articulated around two pivots swiveling on fixed axes;
• two articulated links connecting together the two ends of the forks located on the same side of the register;
• two diametrically opposite pivots, supporting said register and placed in the middle of said links;
• means for pivoting the two forks simultaneously around their pivots and at least one register guide device formed by two arms articulated around fixed pivots, the ends of the two arms being connected to each other by an articulated connecting rod carrying, its middle, a pivot fixed outside said register.

The advantages of the invention will be better understood from through the following description which refers to the accompanying drawings, which illustrate without any limiting character preferential modes of realization of the invention.

In the drawings, identical or similar elements bear, unless otherwise indicated, the same references from one figure to another.

Figure 1 illustrates in partial cross-sectional view a combustion appliance equipped with a burner associated with two transport of oxidizer, each equipped with a sliding damper cylindrical.

Figure 2 is a simplified perspective view of the register of figure 1.

Figure 3 illustrates in cross-sectional (and longitudinal) view simplified the application of the invention to a burner associated with means of combustion smoke recirculation.

Figure 4 illustrates in partial longitudinal section view a burner equipped with two registers of the same diameter; Figure 5 is a partial enlarged view of Figure 4 illustrating the movable shell of a damper fitted with sealing brushes at each end.

With reference to Figures 1 and 2 in particular, the apparatus 1 to combustion allows the production of a flame 2 in a combustion 3 delimited by walls 4 of refractory material.

An orifice 5, for example cylindrical, extending along the axis 7 of general symmetry of the burner and the combustion apparatus is provided in the wall 4, inside which the burner 6 extends.

This burner is associated with a duct 8, extending along the axis longitudinal 7 of symmetry, transporting a fuel (liquid or pulverulent) up to the burner nose, as well as conduits 9 delivering gas (such as natural gas or LPG by example).

The wall 4 has a second annular orifice 10 which defines a conduit 11 for transporting oxidant gas through the wall 4.

A fixed structure consisting of a cylindrical shell 13 of axis 7 and a flange 14 essentially, delimits a central duct 12 serving also to the delivery of oxidizer to the nose 6a of the burner 6.

The apparatus 1 has a chamber 15 separate from the chamber 3 by the wall 4, and in which the conduits 8, 9 and a part extend of the structure 14, 13 of the burner, in which chamber 15 are admitted the gases (or the air serving as oxidizer) which are delivered by a conduit 16, according to a radial flow represented by arrow 17.

The device shown in Figures 1 to 3 includes a sliding register internal cylindrical 21, which is shown in the open position maximum in FIG. 1 and in the intermediate position in FIG. 3, and an external cylindrical sliding damper 19 shown in the position of closure in Figures 1 and 3; register 21 allows passage according to the arrow 20 of the oxidizing gases in the central channel 12 for transporting oxidizer to the burner nose, while register 19 prohibits the circulation 18 of oxidizer towards the second conduit or channel 11 of transport of the oxidant to the combustion chamber 3, in the position shown in Figures 1 and 3.

The register 21 mounted sliding along the axis 7, like the register 19, is in the form of a cylindrical shell of circular section, of which the end 21a can come by sliding, with a view to closing the passage 33, in contact with a wall 23 delimiting the chamber 15 and at through which lines 8 and 9 extend, as well as connecting rods 24 for moving registers 19 and 21.

Register 19 consists of a rolled sheet forming a ferrule cylindrical, provided (figure 1) in the central part with a corrugation 19b to reinforce it, extending from a first end 19a in contact with a flange 22 fitted to the wall 4 (in the closed position shown in Figure 1), to a second end (19d in Figure 2) or it is provided with a flat transverse sheet 19c (Figures 1 and 3) forming a flange or crown and coming to bear against the flange 14 (making part of the fixed structure supporting the burner and the appliance combustion) to ensure a tight seal in this position.

Each of registers 19 and 21 is respectively supported, guided and set in motion via connecting rods 27 and 29 (for what concerns register 19), which connecting rods 27 and 29 (fork-shaped) are linked by a hinge 27a, 29a to a central link 28 to which is fixed the register 19 by a central articulation 28a, for form a Watt parallelogram; two Watt parallelograms arranged symmetrically with respect to a median longitudinal plane, as illustrated in Figure 2 in particular, as well as a third parallelogram of Watt 28, 34 serving as anti-rotation stabilizer, form the register guide system 19.

Each of the forks 27, 29 in a semi-circular arc is articulated, thanks to two pivots (arranged symmetrically on either side of a longitudinal plane containing the axis 7 and the axis of the control rod 24) 27b (respectively 29b), with respect to bars or support rods 35, partially shown, which are linked to the fixed structure.

The shell of the register 19 is thus suspended from the three pivots or joints 28a of the three links 28; according to an alternative, the third link 28 of the third parallelogram 34, 28 can be replaced by a guide preventing rotation of the ferrule 19.

An identical or smaller system, comprising connecting rods or forks 30 and 32 and a central link 31, allows the same way support, guidance and drive in motion register 21; the registers are respectively activated by two cylinders 25 and 26, by means of a rod or connecting rod 24 extending at through bulkhead 23, and provided with an articulated connection with the fork 27 (respectively 30) ordered.

With reference to FIG. 3, a similar device with double register sliding is used in a combustion appliance equipped with means smoke recycling, and a mixed burner.

Such a burner comprises a central supply duct 12 in primary air, means 8 for injecting liquid fuel into the hearth 3 arranged inside the central duct 12 (in the axis of this last), a flame stabilizer 55 disposed coaxially with the interior of this central duct 12, and several orifices 63 secondary air supply located outside the means injection 8 of liquid fuel and of line 12; means 9 injection of gaseous fuel are arranged in a ring between the injection means 8 of liquid fuel and the orifices 13 secondary air supply; these can be replaced with a single annular passage 11 arranged in a ring outside said injection means 9 and 8; stabilizer 55 includes means 55a forming a screen surrounding the rod 8, which is arranged set back from the nozzles and is fitted with peripheral fins 55b.

The device comprises a ring 53 ₁ of refractory material comprising all of the air supply, fuel injection and smoke recirculation orifices, which is mounted through the refractory wall 4 of the hearth 3 so that its front face 53, through which said orifices open, or projecting relative to the latter.

• d'une part un caisson 60 de distribution desdites fumées recirculées, alimenté d'un côté par les orifices d'aspiration 74 des fumées dans le foyer 3, et réinjectant celles-ci après refroidissement, dans des conduits 59 de réinjection dans le foyer, à travers lesquels débouchent également les moyens d'injection 9 du combustible gazeux,
• d'autre part, un caisson de distribution 64 de l'air secondaire, qui d'un côté est alimenté (flèche 18) par un conduit d'alimentation 16, après passage dans le registre 19, et d'un autre côté (après réchauffement de cet air secondaire) injecte celui-ci dans le foyer par les canaux 11 terminés par les orifices 63 définis précédemment.

The orifices 63 are placed peripherally in staggered rows between the orifices 74 for sucking the fumes in the hearth 3; these suction orifices 74 can be replaced by a single peripheral annular passage, but the presence of multiple orifices staggered makes it possible to avoid re-aspirating the secondary air in said smoke suction orifices and allows (conversely) 'prevent this secondary air supply preventing said fumes from being sucked (according to arrow 61) to be recirculated in the burner head; these two fluids exchange their calories inside the burner, thanks to a common wall 60 ₁ separating:

• on the one hand, a box 60 for distributing said recirculated fumes, supplied on one side by the suction orifices 74 for the fumes in the hearth 3, and reinjecting these after cooling, in conduits 59 for reinjection into the hearth, through which also open the injection means 9 of the gaseous fuel,
• on the other hand, a secondary air distribution box 64, which on one side is supplied (arrow 18) by a supply duct 16, after passage through the register 19, and on the other hand (after heating of this secondary air) injects it into the hearth through the channels 11 terminated by the orifices 63 defined above.

The means 9 for injecting gaseous fuel and the means for reinjection of the fumes, which are preferably coaxial and have their orifices 9 combined, are located in the peripheral ring around the flame stabilizer 55.

To create a staging of the air intake relative to the flame liquid fuel, the fuel injection ports as well than those of gaseous fuel and primary air supply, lead to the bottom of a bowl 56; it is hollowed out by relation to the refractory wall 53 which surrounds it and through which open out said orifices 63 and the fumes from the focus 2; the bowl may be in the form of a truncated cone.

The means 9 for injecting the gaseous fuel can be separate feeding rods, arranged in a ring around the means 8 for injecting liquid fuel and located in the conduit 12 primary air supply, or be replaced by nozzles mounted on a single ring arranged peripherally in a ring around the injection means 8 of the liquid fuel, and supplied by a single feeding rod.

The means 8 for injecting the liquid fuel can have multiple orifices, creating multiple flames independent in foyer 3 which can be either directed parallel to axis 7 of the burner, either divergent and oriented towards secondary air supply ports 63 to improve the combustion of said liquid fuel after a first phase of combustion with primary air.

The sliding register system according to the invention applies also advantageously to the burners described in application EP 774 620, which do not include smoke recirculation circuits.

As illustrated in FIG. 4, the admission of oxidizer into the conduit 12 along arrow 20, is effected by passing through orifices circulars 13a regularly drilled in the rear part of the shell fixed 13; this ferrule is pierced in the front part with elongated orifices 13b allowing the passage, according to arrow 18, of the oxidizer from the chamber 15 to the duct 11 of annular section which surrounds the central duct 12.

Each of the mobile ferrules of the register before 19 and of the register rear 21 is provided at each longitudinal end with a corrugation annular delimiting a groove receiving a brush 99 (Figure 5) seal which rests on the fixed shell 13.

As illustrated in Figures 1, 3, 4, the position of the "front" register 19 - and associated openings 13b - arranged against the wall 4 contributes to the compactness of the burner.

Claims (10)

Burner (6) with liquid and / or gaseous fuel, comprising a central duct (12) for supplying primary oxidizer (air), inside which coaxially extend a rod (8) for injecting fuel terminated by one or more nozzles (6a) and a stabilizer (55) comprising a hub (55a) forming a screen surrounding the rod (8), which is set back from the nozzles and is provided with fins peripherals (55b), the burner further comprising a duct (11) supply of secondary oxidant (air) extending around the central duct (12), said burner being characterized in that it comprises two sliding cylindrical registers (19, 21) each supported by an articulated structure comprising two or three parallelograms of Watt. Burner according to claim 1, wherein each of registers (19, 21) comprises sealing means (19c) comprising a deformable metal seal (99). Burner according to claim 2, wherein each of registers (19, 21) comprises circumferential stiffeners (19b). Burner according to claim 3, which comprises a jack (25, 26) respective actuation of each register to regulate the opening partial of each register according to data or signals delivered by a control unit. Burner according to any one of Claims 2 to 4, wherein each register has two metallic seals (99) deformables arranged at each end of the register in a corrugation or circumferential groove for reinforcing the sheet of the damper, which seals are supported on the external face of a cylindrical shell fixed (13) delimiting one of said conduits (11, 12). Burner according to any one of Claims 2 to 5, in which the registers are of substantially identical diameter. Burner according to any one of claims 2 to 6, which comprises a fixed ferrule (13) perforated (13a, 13b). Burner according to any one of claims 1 to 7, which further comprises several conduits (9) for injecting combustible gas which extend partly inside and around the central duct (12) of the flame stabilizer (55). Combustion appliance such as a cogeneration of electrical and thermal energy, which involves several burners (6) according to any one of claims 1 to 8, which are supplied with oxidant via a common radial or oblique conduit (16). Method of command and control of the operation of burners (6) of an apparatus according to claim 9, wherein one regulates partial opening of each register according to data or signals delivered by a control unit.

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