A burner unit with an air regulator

Description

[0001] This invention relates to a burner unit having a regulator for the air supply.

[0002] In any burner unit the air for combustion by the burner is generally regulated by a damper, butterfly valve, one or more gates etc, and this causes a loss of head in the air circuit. Also the air is set in motion either by the natural draught, by a fan or more usually by a combination of the two. Apart from certain highly automated industrial installations, the adjustment is fixed and is set at intervals which may range from for example one week to one year. The adjustment is made for average conditions and therefore is rarely satisfactory if the natural draught of the chimney represents a substantial part of the total motive head.

[0003] We have now devised a burner unit having an air regulator which automatically controls the air pressure at the inlet of the burner at a predetermined value relatively to the pressure of the exhaust gas flow downstream of the burner, which predetermined value may be that of the base of the chimney or at a value differing from that of the base of the chimney by a fixed amount.

[0004] U.S. patent 2,283,745 discloses a regulator for controlling the setting of a damper in the air supply to a natural draught burner, so as to maintain a predetermined pressure difference between the upstream air pressure and the combustion chamber of the burner. The pressure difference is determined by the setting of a spring which applies an elastic biasing force on a diaphragm separating two zones subjected to the upstream air pressure and the combustion chamber pressure.

[0005] An air inflow regulator for a burner is also known from U.K. patent 691,376. The regulator includes a corrugated capsule exposed on opposite sides to the differential pressure to be monitored but one side of the capsule is exposed to the kinetic pressure of the incoming air so that it takes into account its mass flow. Additionally, the capsule is an elastic corrugated capsule.

[0006] In contrast, the present invention employs a partition, subjected on opposite sides to the pressures to be monitored and controlled, which is freely moveable within a container with substantially no elastic return forces, for responding to changes in pressure of the exhaust gas flow downstream of the burner.

[0007] According to the present invention there is provided a burner unit, which comprises a burner and an intake for air for the burner; in combination with an air regulator for controlling the air flow to the said intake, the regulator comprising a flow regulating device in the air supply to said intake and a container divided into one zone in communication with the air supply to said intake and another zone in communication with the exhaust gas flow downstream of the burner, the zones being separated by a partition so that the pressure of each zone is respectively that of the air supply to said intake and that of the downstream exhaust gas flow and the partition being operably coupled to the flow regulating device and responsive to the pressures of said zones such that a change in pressure in the downstream exhaust gas flow causes the flow regulating device to adjust the air supply to said intake to oppose said change whereby the pressure values of the air supply to said intake and the exhaust gas flow downstream of the burner remain substantially constant relative to one another, characterised in that the partition is freely moveable within the container with substantially no elastic return forces for responding to changes in pressure in the downstream exhaust gas flow.

[0008] The air regulator is eminently suitable for use with the burner unit described in French patent 2311994 (equivalent to U.K. Patent 1 554226. However the air regulator can be attached to any burner unit, for example burner units used for heating premises connected to natural draught chimneys. Furthermore the air regulator can act as a scavenging limiter when the burner unit is not being used, for as the pressure drops in the combustion zone and chimney of the burner unit so will the supply of air to the regulator from the atmosphere substantially cease.

[0009] It has been found that there is good control on burners fitted with this regulator with a diminution in the variation in the amount of C0₂ produced compared with the same burner unit not using this regulator.

[0010] The container which is divided into zones by the moveable partition can take various forms, and may simply be a cylinder or a rectangular box with a slideable piston as the moveable partition. Alternatively, it may be a cylindrical housing with rotary blades constituting the moveable partition. Other suitable forms of container are any mechanical arrangements producing a displacement when submitted to a differential pressure provided there are substantially no elastic return forces. In such cases the moveable partition can for example be a pendulum, or certain kinds of a membrane or an aneroid type element.

[0011] The separate communications between the zones and the air flow downstream of the burner and the air supply to the burner are usually by way of pipe, conduit or tubing. The communication with the air supply downstream of the burner is preferably made with the chimney stack of the burner, but it can if desired be made at the combustion chamber itself.

[0012] Most burner units include a fan or other device, between the intake of the burner unit and the burner itself, which takes in air at atmospheric pressure and delivers it at a higher pressure e.g. a compressor. In such cases the respective zone of the container must communicate with the air supply upstream of the fan or said other device. Most burner units also include an adjustment means whereby for a given operation the amount of air entering the burner is fixed at a certain level. Again the respective zone of the container must communicate with the air supply upstream of the adjustment means.

[0013] The flow regulating device for causing a change in the amount of air entering the air regulator may be of various forms, for example a damper, butterfly valve, a gate or one or more vanes, e.g. where the moveable partition comprises rotary blades. It must be designed so that aerodynamic forces do not produce substantially any force or momentum tending to close or open the flow regulating device. The flow regulating device is operatively connected to the moveable partition and this may be by means of a mechanical link whereby for example lateral shifting of the moveable partition in a box or cylinder causes lateral shifting of the link which thereby alters the setting of the flow regulating device according to how much lateral shifting has been undergone by the moveable partition. Where a rotary container is used shifting of the blades due to a difference of pressure will cause a shifting of a vane or vanes whereby the amount of air entering the air regulator is altered.

[0014] If desired one could use a servo mechanism, for example pneumatic, hydraulic or electric, to replace the mechanical connection between the moveable partition and the flow regulating device. This could be suitable for large burners where the flow regulating device may be hard to move.

[0015] The connection between the moveable partition and the flow regulating device can be adjusted so that negative pressure in the combustion chamber will tend to move the moveable partition in a direction closing the regulating means. If the burner is operating this closure will subject the air supply to a sub-atmospheric pressure and with no return force the flow regulating device will continue to close until the air supply pressure is equal to that in the combustion chamber.

[0016] If the burner is not working the flow of air is very slight so that the pressure drop through the regulator is negligible and the air regulator will close completely, thus limiting the scavenging of the combustion chamber when the burner unit is not working. This may often be advantageous in that heat losses can be reduced during shut-down periods.

[0017] By contrast when the burner starts, a pressure peak generally occurs before the draught (which is due to the difference in temperature between the flue gases and ambient air) is established and for analogous reasons the regulator opens widely, so reducing the smoke during the few seconds or minutes following the start up.

[0018] For a natural draught burner unit there must be a difference in pressure between the air supply and the combustion chamber and the pressure of the air supply must be greater than that of the combustion chamber. It is necessary therefore that the difference in pressure between the zones should not cause the moveable partition to move so much that the flow regulating device changes the amount of air so that the pressure of the air supply equalises that the combustion chamber. This can be readily prevented by applying a force to one side of the moveable partition, the force being applied so as to act against the tendency of the moveable partition to close the air regulator. A weight connected to the moveable partition by a line passing over a pulley is a convenient way of applying a force. It is desirable that the difference in pressure between the air supply and the combustion chamber should be constant, and the use of the weight as just described provides this constant pressure difference.

[0019] It is preferred that burner units where there is no pressure difference between the air supply to the burner and the combustion chamber be used.

[0020] The invention is now described with reference, by way of example, to the drawings in which:

Figure 1 shows a perspective view of one form of air regulator suitable for use with a burner;

Figure 2 shows a view of another regulator;

Figure 3 shows the regulator of Figure 1 with an upstream fan, for a combustion chamber under superatmospheric pressure;

Figure 4 shows an exploded perspective view of a rotary form of the regulator;

Figure 5 shows an axial section of the regulator of Figure 4;

Figure 6 shows a cross-section of the regulator on the line 6-6 of Figure 5; and

Figure 7 shows a view of a detail of a modified form of the regulator according to Figures 4 to 6.

[0021] Referring to Figure 1 of the drawings where it is assumed that the combustion chamber is under negative pressure a damper 1 closes an air box 2 in communication with the air supply. This damper 1 is constructed so as to slide freely so that the difference in pressure between the two faces of the damper does not lead to any forces tending to open or close the damper.

[0022] A piston 3 moves in a cylinder 4 which is closed at both ends except for allowing passage of rod 8 which connects the piston 3 to the damper 1. In this example the regulator therefore consists of the box 2, damper 1, cylinder 4, piston 3 and rod 8. The chamber or zones 5 and 6 on each side of the piston 3 are connected respectively via conduits 9 and 10 to the box 2 and the combustion chamber (not shown). The cross-section of conduits 9 and 10 is sufficient to enable the pressure in the zones 5 and 6 to be the same as that in box 2 and combustion chamber respectively.

[0023] Since this regulator (Figure 1) has no return force the negative pressure in the combustion chamber will tend to move the piston 3 (to the left in Figure 1) so as to close the damper 1. If the burner is operating, the closing of damper 1 will subject the box 2 to a subatmospheric pressure and the damper 1 will continue to close until the pressure in the box 2 is equal to that in the combustion chamber. Therefore, the piston 3 moves into a different position of equilibrium within cylinder 4 according to the magnitude of the change in pressure in the downstream exhaust gas flow.

[0024] For a natural draught burner there must obviously be a difference in pressure between the system upstream of the burner unit and the combustion chamber. Figure 2 shows a regulator which provides this difference in pressure and a difference which is constant. Parts shown with numerals 1, 3, 4, 5, 6 and 8 are as previously described. This rod passes out of zone 5 and is connected to cable 12 which passes over pulley 13 and is connected to weight 14. The (constant) difference in pressure between zones 5 and 6, will be

where m is the mass of weight 14 and S the cross- . sectional area of piston 3. It is necessary that the piston 3 should have sufficient power to overcome friction and displace the damper 1.

[0025] The area of cross-section S must therefore be large and friction as low as possible. If S is large the variation of volume of zones 5 and 6 will be large and conduits 9 and 10 (not shown) of large cross-section area are used to avoid excessive time for achieving desired changes to the damper opening.

[0026] Normally combustion chambers which are under superatmospheric pressure are not of interest as far as this invention is concerned because they are usually completely insensitive to variations of natural draught. However where combustion chambers are occasionally subjected to superatmospheric pressure the regulator and burner can still be used provided that upstream of the damper of the air regulator there is a fan which for the normal air supply produces a head at least equal to the highest superatmospheric pressure recorded. A suitable regulator is shown in Figure 3 where the same numerals indicate identical parts as those shown in Figure 1 and the fan is shown at 15.

[0027] A regulator having more sensitivity is described with reference to Figures 4 to 7 which is a rotary regulator. There is a stationary housing 16 and a rotary bell 17. Both housing 16 and bell have blades 18 and 19 respectively. In this case there are two zones 5 and two zones 6, each zone being bounded by the blades 18 and 19. As can be seen from Figure 6 zones 6 are in communication with conduits 11 leading to the combustion chamber and zones 5 communicate with ports or conduits 10 leading to the air supply.

[0028] The fixed housing 16 carries circumferential vanes 20 as does the rotary bell 17 i.e. vanes 21. The rotary bell 17 is mounted co-axially inside the housing 16 so that the relative overlap of the vanes 20 on the one hand and the vanes 21 on the other hand act as a damper for air passing through the regulator. Pressure differences between zones 5 on the one hand and zones 6 on the other hand will cause slight rotation of bell 17 thereby altering the damper setting until the pressure is equalised.

[0029] One difficulty of a rotary regulator is to achieve tightness between the rotary bell 17 and the housing 16, that is between the zones 5 and 6 and the outside. This can be achieved if the depth of the housing amounts to a few cm, if diametrical play is minimum (less than 0.5 mm) and if one of the two walls is of the labyrinth type. This is shown in Figure 7 where the hub 23 of the housing 16 has an undulating surface about which rotates the hub 22 of the rotary bell 17. In the regulator described with reference to Figures 4 to 7 the nozzle pipe 24 passes through the regulator and the bearing is important in size and difficult to realise. When the burner unit is of the pneumatic atomisation type, the atomisation compressor facility may be used to provide an air bearing which is frictionless. The bearing hence rotates about a fixed axis, floating on an air film. In other cases good results can be obtained using a thin axle for example 1 mm diameter for a domestic burner, rotating in fixed bearings.

Claims

1. A burner unit, which comprises a burner and an intake for air for the burner, in combination with an air regulator for controlling the air flow to the said intake, the regulator comprising a flow regulating device (1) in the air supply to said intake and a container (4) divided into one zone (5) in communication with the air supply to said intake and another zone (6) in communication with the exhaust gas flow downstream of the burner, the zones (5, 6) being separated by a partition (3) so that the pressure of each zone (5, 6) is respectively that of the air supply to said intake and that of the downstream exhaust gas flow and the partition (3) being operably coupled to the flow regulating device (1) and responsive to the pressures of said zones (5, 6) such that a change in pressure in the downstream exhaust gas flow causes the flow regulating device (1) to adjust the air supply to said intake to oppose said change whereby the pressure values of the air supply to said intake and the exhaust gas flow downstream of the burner remain substantially constant relative to one another, characterised in that the partition (3) is freely moveable within the container (4) with substantially no elastic return forces for responding to changes in pressure in the downstream exhaust gas flow.

2. A burner unit and an air regulator in combination according to claim 1, characterised in that the burner unit further comprises a fan between said intake and said burner.

3. A burner unit and an air regulator in combination according to claim 1 or 2, characterised in that the burner unit further comprises an air regulating device between said intake and said burner.

4. A burner unit and an air regulator in combination according to claim 1, 2 or 3, characterised in that said flow regulating device (1) is arranged to maintain the pressure values of the air supply to said intake and the downstream exhaust gas flow substantially the same.

5. A burner unit and an air regulator in combination according to any one of claims 1 to 3, characterised in that a force is applied to one side of the partition (3) so as to act against the tendency of the partition to close the air regulator.

6. A burner unit and an air regulator in combination according to any preceding claim, characterised in that the partition (3) is moveable into a different position of equilibrium within the container (4) according to the magnitude of any change in pressure in the downstream exhaust gas flow.

7. A burner unit and an air regulator in combination according to any preceding claim, characterised in that the container (4) is a cylinder, the partition (3) a slideable piston, and the flow regulating device (1) is a damper, the slideable piston (3) being connected to the damper (1) by a mechanical link (8) whereby lateral shifting of the piston (3) alters the setting of the damper (1).

8. A burner unit and an air regulator in combination according to any one of claims 1 to 6, characterised in that the container is a stationary cylindrical housing (16) having a first set of blades (18) and the moveable partition comprises a rotary bell (17) having a second set of blades (19) and being mounted coaxially inside the stationary housing (16) so as to provide a first plurality of zones (5) in communication with one another and with the air supply to said intake, and a second plurality of zones (6) in communication with one another and with the exhaust gas flow downstream of the burner, the zones of said first and second plurality (5, 6) being bounded by the blades (18, 19) of the stationary housing (16) and of the rotary bell (17).

9. A burner unit and an air regulator in combination according to claim 8, characterised in that the flow regulating device comprises one or more vanes (20, 21).

10. A burner unit and an air regulator in combination according to any one of the preceding claims, characterised in that said another zone (6) of the container (4) communicates with a chimney stack associated with the burner.

Ansprüche

1. Brennereinheit mit einem Brenner und einem Lufteinlaß für den Brenner, und zwar in Kombination mit einem Luftregler zur Steuerung des Luftstroms zu dem Einlaß, wobei der Regler eine Strömungsregelungseinrichtung (1) in der Luftzufuhr zu dem Einlaß und einen Behälter (4) aufweist, der in eine Zone (5), die an die Luftzufuhr des Einlasses angeschlossen ist und in eine andere Zone (6) unterteilt ist, die mit dem Abgasstrom stromabwärts von dem Brenner in Verbindung steht, wobei die Zonen (5, 6) durch eine Trennwand (3) derart getrennt sind, daß der Druck jeder Zone (5, 6) jeweils der der Luftzufuhr zu dem Einlaß und der des stromabwärtigen Abgasstroms ist und wobei die Trennwand (3) arbeitsmäßig an die Strömungsregelungseinrichtung (1) angeschlossen ist und auf die Drücke der Zonen (5, 6) anspricht, so daß eine Druckverländerung im stromabwärtigen Abgasstrom bewirkt, daß die Strömungsregelungseinrichtung (1) die Luftzufuhr zu dem Einlaß einstellt, um der Veränderung entgegenzuwirken, wodurch die Druckwerte des Luftzuführung zu dem Einlaß und des Abgasstroms stromabwärts von dem Brenner im wesentlichen konstant in bezug aufeinander bleiben, dadurch gekennzeichnet, daß die Trennwand (3) in dem Behälter (4) im wesentlichen ohne elastische Rückstellkräfte zum Eingehen auf Druckänderungen in dem stromabwärtigen Abgasstrom frei bewegbar ist.

2. Brennereinheit und Luftregler in Kombination, und zwar gemäß Anspruch 1, dadurch gekennzeichnet, daß die Brennereinheit ferner ein Gebläse zwischen dem Einlaß und dem Brenner aufweist.

3. Brennereinheit und Luftregler in Kombination, und zwar gemäß Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Brennereinheit ferner eine Luftregeleinrichtung zwischen dem Einlaß und dem Brenner aufweist.

4. Brennereinheit und Luftregler in Kombination, und zwar gemäß Anspruch 1, 2 oder 3, dadurch gekennzeichnet, daß die Strömungsregelungseinrichtung (1) angeordnet ist, um die Druckwerte der Luftzufuhr zu dem Einlaß und den stromabwärtigen Abgasstrom im wesentlichen gleich zu halten.

5. Brennereinheit und Luftregler in Kombination, und zwar nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß eine Kraft auf eine Seite der Trennwand (3) ausgeübt wird, um gegen die Neigung der Trennwand zum Schließen des Luftreglers zu wirken.

6. Brennereinheit und Luftregler in Kombination, und zwar gemäß einem der vorhergenden Ansprüche, dadurch gekennzeichnet, daß die Trennwand (3) in eine andere Gleichewichtsstellung in dem Behälter (4) gemäß der Größe einer Druckveränderung im stromabwärtigen Abgasstrom bewegbar ist.

7. Brennereinheit und Luftregler in Kombination, und zwar gemäß einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß der Behälter (4) ein Zylinder ist, daß die Trennwand (3) ein verschiebbarer Kolben ist, und daß die Strömungsregelungseinrichtung (1) ein Dämpfer ist, wobei der verschiebbare Kolben (3) mit dem Dämpfer (1) durch ein mechanisches Gestänge (8) verbunden ist, so daß eine Lateralverschiebung des Kolbens (3) die Einstellung des Dämpfers (1) verändert.

8. Brennereinheit und Luftregler in Kombination, und zwar gemäß einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, daß der Behälter ein stationäres zylindrisches Gehäuse (16) mit einer ersten Gruppe von Flügeln (18) ist und daß die bewegbare Trennwand eine drehbare Manschette (17) aufweist, die eine zweite Gruppe von Flügeln (19) hat und koaxial innerhalb des stationären Gehäuses (16) montiert ist, um eine erste Anzahl von Zonen (5) miteinander und mit der Luftzufuhr zu dem Einlaß und eine zweite Anzahl von Zonen (6) miteinander und mit dem Abgasstrom stromabwärts von dem Brenner in Strömungsverbindung zu bringen, wobei die Zonen der ersten und zweiten Anzahl (5, 6) durch die Flügel (18,19) des stationären Gehäuses (16) und der drehbaren Manschette (17) begrenzt sind.

9. Brennereinheit und Luftregler in Kombination, und zwar gemäß Anspruch 8, dadurch gekennzeichnet, daß die Strömungsregelungseinrichtung ein oder mehrere Leitbleche (20, 21) aufweist.

10. Brennereinheit und Luftregler in Kombination, und zwar gemäß einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die andere Zone (6) des Behälters (4) mit einer zu dem Brenner gehörenden Schornsteinanordnung in Strömungsverbindung steht.

Revendications

1. Bloc brûleur, qui comprend un brûleur et une admission d'air pour le brûleur, en combinaison avec un régulateur d'air destiné à commander l'écoulement de l'air vers ladite admission, le régulateur comprenant un dispositif (1) de régulation d'écoulement dans l'alimentation en air vers ladite admission et un contenant (4) divisé en une première zone (5) en communication avec l'alimentation en air vers ladite admission et une autre zone (6) en communication avec l'écoulement de gaz d'évacuation en aval du brûleur, les zones (5, 6) étant séparées par une cloison (3) de manière que la pression de chaque zone (5, 6) soit respectivement celle de l'alimentation en air vers ladite admission et celle de l'écoulement de gaz d'évacuation en aval, et la cloison (3) étant accouplée fonctionnellement au dispositif (1) de régulation d'écoulement et étant sensible aux pression desdites zones (5, 6) de manière qu'une variation de pression dans l'écoulement de gaz d'évacuation en aval ait pour effet, sur le dispositif (1) de régulation d'écoulement, de lui faire régler l'alimentation en air vers ladite admission afin de s'opposer à ladite variation pour que les valeurs de pression de l'alimentation en air vers ladite admission et de l'écoulement de gaz d'évacuation en aval du brûleur restent sensiblement constantes l'une par rapport à l'autre, caractérisé en ce que la cloison (3) est mobile librement à l'intérieur du récipient (4), pratiquement sans aucune force de retour élastique, pour réagir aux variations de pression dans l'écoulement de gaz d'évacuation vers l'aval.

2. Bloc brûleur et régulateur d'air en combinaison selon la revendication 1, caractérisés en ce que le bloc brûler comprend en outre un ventilateur entre ladite admission et ledit brûleur.

3. Bloc brûleur et régulateur d'air en combinaison selon la revendication 1 ou 2, caractérisé en ce que le bloc brûleur comprend en outre un dispositif de régulation d'air entre ladite admission et ledit brûleur.

4. Bloc brûleur et régulateur d'air en combinaison selon la revendication 1, 2 ou 3, caractérisés en ce que le dispositif (1) de régulation d'écoulement est agencé de façon à maintenir les valeurs de pression de l'alimentation en air vers ladite admission et de l'écoulement de gaz d'évacuation vers l'aval sensiblement les mêmes.

5. Bloc brûleur et régulateur d'air en combinaison selon l'une quelconque des revendications 1 à 3, caractérisés en ce qu'une force est appliquée à un premier côté de la cloison (3) afin d'agir contre la tendance de la cloison à fermer le régulateur d'air.

6. Bloc brûleur et régulateur d'air en combinaison selon l'une quelconque des revendications précédentes, caractérisés en ce que la cloison (3) peut se déplacer vers une position différente d'équilibre à l'intérieur du récipient (4) en fonction de l'amplitude de toute variation de pression dans l'écoulement de gaz d'évacuation en aval.

7. Bloc brûleur et régulateur d'air en combinaison selon l'une quelconque des revendications précédentes, caractérisés en ce que le récipient (4) est un cylindre, la cloison (3) est un piston coulissant et le dispositif (1) de régulation d'écoulement est un registre, le piston coulissant (3) étant relié au registre (1) par une liaison mécanique (8) afin qu'un déplacement latéral du piston (3) modifie le positionnement du registre (1

8. Bloc brûleur et régulateur d'air en combinaison selon -l'une quelconque des revendications 1 à 6, caractérisés en ce que le récipient est un corps cylindrique fixe (16) comportant un premier jeu de palettes (18) et la cloison mobile comprend une cloche rotative (17) comportant un second jeu de palettes (19) et montée coaxiale- ment à l'intérieur du corps fixe (16) afin de former un premier groupe de zones (5) en communication les unes avec les autres et avec l'alimentation en air vers ladite admission, et un second groupe de zones (6) en communication les unes avec les autres et avec l'écoulement de gaz d'évacuation en aval du brûleur, les zones desdites premier et second groupes (6) étant délimitées par les palettes (18, 19) du corps fixe (16) et de la cloche rotative (17).

9. Bloc brûleur et régulateur d'air en combinaison selon la revendication 8, caractérisés en ce que le dispositif de régulation d'écoulement comprend une ou plusieurs ailettes (20, 21).

10. Bloc brûleur et régulateur d'air en combinaison selon l'une quelconque des revendications précédentes, caractérisés en ce que ladite autre zone (6) du récipient (4) communique avec une cheminée associée au brûleur.

Drawing