EP1812747A1

EP1812747A1 - Burner for a heating device with improved fuel supply

Info

Publication number: EP1812747A1
Application number: EP05814457A
Authority: EP
Inventors: Michael PÖHNER; Friedrich Widemann; Steffen Weber; Jan Steffens
Original assignee: Webasto SE
Current assignee: Webasto SE
Priority date: 2004-11-17
Filing date: 2005-11-16
Publication date: 2007-08-01
Also published as: US20090239184A1; RU2361107C2; JP2008520949A; KR20070086043A; RU2007122480A; WO2006053541A1; CA2601319A1; DE112005003410A5; CN101103226A

Abstract

The invention relates to a burner for a heating device, in particular, for application in motor vehicles, comprising a burner nozzle (12), for the introduction and atomisation of fuel, which has a fuel lance (14), for the introduction of fuel into the burner (10), a combustion air inlet (16), for the introduction of combustion air into the burner and a starter zone (18), in which an ignition of the fuel to start the burner occurs. According to the invention, the exit speed of the fuel is determined by selection of the inner diameter of the fuel lance (14), such that during a start phase for the burner (10), fuel enters the start zone (18) in an essentially non-atomised form.

Description

Burner for a heater with improved fuel supply

The invention relates to a burner for a heater, in particular for use in motor vehicles, having a burner nozzle for supplying and atomizing fuel, which has a fuel needle for supplying fuel into the burner and a combustion air supply for supplying combustion air into the burner, and a start zone in which an ignition of the fuel to start the burner er¬ follows.

Such burners, which are also referred to as atomizing burners or as spray burners, are used in particular in auxiliary heaters and auxiliary heaters for motor vehicles. There are numerous requirements for such burners, in particular with regard to safe and largely emission-free starting behavior and stable combustion operation. Furthermore, efforts are being made to design heaters which can be used in different mounting positions.

With regard to the starting behavior, different operating parameters must be coordinated with one another. On the one hand, it is necessary to provide a relatively rich fuel-air mixture during the burner start in the starting zone, but on the other hand it is necessary to provide a sufficient amount of primary combustion air to transport the fuel from the fuel needle to ensure the starting zone.

The requirement to allow different installation positions of the heating appliance is connected with the problems with regard to the starting behavior. In order to be able to transport fuel into the starting zone with little supply of primary air, it has hitherto been accepted to orient the fuel needle with the outlet opening facing downwards; As a result, the entire burner had to be mounted in a vertical installation position.

In order to ensure a stable combustion operation of the burner, contradictory requirements must also sometimes be met. On the one hand, a good thorough mixing of fuel and air is always required; on the other hand, it is in the core region of the flame and there in particular during the start-up phase undesirable to cause high levels of air and excessive turbulence.

The object of the invention is to at least partially overcome the described problems of the prior art and, in particular, to enable a reliable and low-emissivity or low-smoke starting behavior with different installation positions.

This object is achieved by the features of the independent claim.

Advantageous embodiments of the invention are indicated in the dependent claims.

The invention is based on the burner of the generic type in that, by choosing the inner diameter of the fuel needle, the exit velocity of the fuel is predetermined in such a way that fuel reaches the starting zone in a substantially unatomized form during a starting phase of the burner. By reducing the Innendurch¬ diameter of the fuel needle compared to Brennstoffna¬ deln in heaters of the prior art, the exit speed of the fuel is increased in Glei¬ chem fuel delivery volume. This makes it possible in any installation position that a fuel jet from the Austrittsöff¬ tion of the fuel needle enters the start zone. In particular, with a small amount of primary air, wherein the primary air supplied should also have only a slight twist, such a substantially non-atomized fuel jet can reach the starting zone. Consequently, the Burner sure, and the formation of smoke during takeoff is significantly reduced.

It is preferable that the inner diameter of the fuel needle is between 0.5 and 0.7 mm. In comparison to exit speeds in fuel needles of the prior art, in which the inner diameter is in the range of 0.8 mm, the exit velocity at inner diameters between 0.5 and 0.7 mm can be almost doubled or even more than doubled ,

It is particularly preferred that the inner diameter of the fuel needle is about 0.6 mm. With such an inner diameter, exit speeds of more than 0.6 m / s are possible in full-load operation, ie at a fuel mass flow of 0.5 kg / h, while at an inner diameter of 0.8 mm, the exit velocity is in the range of 0.35 m / s. Correspondingly, the exit speed increases during part-load operation, that is to say at a fuel mass flow of 0.2 kg / h from approximately 0.14 m / s to approximately 0.25 m / s. With a corresponding selection of structural properties or operating parameters, the goal of a substantially non-atomized jet, which reaches the starting zone when starting the heater, can also be achieved with a conventional fuel needle with an inner diameter of approximately 0.8 mm.

Usefully, it is provided that the starting zone is designed as a starting chamber into which an ignition element protrudes. The wall of the combustion chamber can surround the ignition element in this way. During the starting operation, the "ballistic" fuel jet then the ignition element and wet the combustion chamber wall with fuel, so that the combustion chamber wall and adjacent components serve as wall evaporator after their heating.

According to a particularly preferred embodiment of the present invention, it is provided that, in addition to the primary air supplied by the burner nozzle, secondary air can be fed into the combustion chamber through openings provided in the heat shield and through a heat shield arranged between the burner nozzle and a combustion chamber the openings are equipped with air guide elements. A heat shield is fundamentally useful for shielding the nozzle and the fuel feed against the heat energy present in the combustion chamber. Secondary air is fed into the combustion chamber via the heat shield. By the openings for secondary air supply are equipped with Luftleitelemen¬ th, the supply of Sekundär¬ this air can be targeted, so that the burning operation, both in terms of the starting mode as well as during continuous operation can be selectively influenced.

Usefully, it is provided that the air guiding elements are formed by tabs formed in the direction of the combustion chamber and integrally formed with the heat shield. Such a heat shield can be manufactured in a simple manner, for example by forming holes with a V-shaped punching tool, which are bent out of the plane of the heat shield after or with the punching operation.

The invention is also usefully further developed in that the tabs are arranged at different angles to the surface of the heat shield and / or to the radius of the heat shield. Shield are formed. If the tabs extend almost perpendicular to the radius of the heat shield, a strong twist is introduced by the latter, while a lesser twist is introduced by tabs with a smaller angle to the radius. Tabs, which occupy a small angle to the surface of the heat shield, produce Luftströ¬ regulations, which have a large radial component and a small axial component, while in tabs with large angles to the surface of the heat shield, the axial component dominated. In this way it is possible to direct secondary air with little swirl into the core region of the flame formation. As a result, on the one hand, the air required for combustion is supplied; however, there is no excessive swirl which would adversely affect the stabilization of the flame. In particular, a division of the secondary air can take place as a function of the orientation of the individual air guiding elements.

According to a further embodiment, it is provided that the tabs are formed in groups at substantially identical angles to the surface of the heat shield and / or to the radius of the heat shield. The collective alignment of the straps results in defined flow states in the combustion chamber.

The invention is further useful in that the burner has a burnout zone and that the secondary air supplied to the burnout zone has a higher swirl than the secondary air supplied to the start zone. In the Ausbrandzone a high twist is desired. In particular, a radially inward swirled back Stream area improves burnout and ensures that the combustion chamber volume is well utilized.

It is further provided that the heat shield has an opening for the passage of an ignition element.

In a particularly preferred embodiment of vorlie¬ ing invention is further provided that the Brenn¬ chamber is substantially axially symmetrical, that in the combustion chamber, a baffle plate is arranged and that the baffle plate has a predetermined curvature in the axial direction. Due to the curvature of the baffle plate, there is a temperature-independent defined shaping of the baffle plate. In the case of newly formed baffle plates of the prior art, this is sometimes not the case since, depending on the temperature, spontaneous changes in shape can occur, which can adversely affect the combustion behavior of the burner.

It is preferred that the curvature is provided in the direction of the burnout zone. As a result, a sufficient space is provided in the region of the starting chamber. Furthermore, it has been found that the curvature in the direction of the burn-out zone does not adversely affect the flow behavior in this zone. In particular, the turbulent pronounced backflow region is retained in the radially inner region of the burnout zone.

According to a preferred embodiment of the invention, it is provided that the outer circumference of the baffle plate defines a level and that the ratio between the maximum axial distance of the baffle plate from this plane and the diameter of the baffle plate is between 0.07 and 0.21. The most bulged point of the baffle plate is preferably substantially at the center of the assembly with respect to the radial coordinate. From the plane defined by the outer circumference of the baffle plate, this point has an axial distance defined by the specified ratio to the diameter.

In this context, it is particularly preferred that the ratio between the maximum axial distance of the baffle plate from the plane and the diameter of the baffle disc is about 0.14. For example, the round diameter of the baffle plate is about 40 mm, while the bulge has a value of about 5.7 mm.

The invention is based on the finding that the operating behavior of a burner can be markedly improved by the novel fuel feed with a fuel needle having a reduced outlet cross section, in particular in combination with the novel heat shield and the novel baffle plate. This applies in particular to the starting behavior, the stability of the burner operation and the possibilities with regard to the installation position of the burner in the motor vehicle.

The invention will now be explained by way of example with reference to the accompanying drawings with reference to preferred embodiments.

Showing:

FIG. 1 shows a sectional view of a burner according to the invention; FIG. 2 is a perspective view of a burner flange with a heat shield inserted therein; and

3 shows a perspective view of a heat shield.

In the following description of the preferred embodiments of the invention, the same reference numerals designate the same or comparable components.

FIG. 1 shows a sectional view of a burner according to the invention. The burner 10 according to the invention has a nozzle 12 which is fixedly connected to a heat shield 24. The heat shield 24, together with a burner tube 40 connected to the heat shield 24, defines a combustion chamber 22. The combustion chamber tube 40 is surrounded by an outer tube 42, which forms the burner flange. At this outer tube 42, a flame tube 38 is attached. The connections between heat shield 24 and combustion chamber tube 40 or between combustion chamber tube 40, outer tube 42 and flame tube 38 are generally welded joints. A fuel feed 50, which has a metal tube 52 for supplying fuel and a fuel needle 14 for injecting fuel into the combustion chamber 22, is arranged on the fuel nozzle 12. Furthermore, in the area of the fuel nozzle 16, there are provided channels for feeding primary combustion air into the fuel nozzle 20, which flows past the fuel needle 14 and then along the radially expanding air guide of the fuel nozzle 12 in the direction of the combustion chamber and finally into the fuel nozzle Burner chamber 22 to flow. Due to the radial expansion of the air guide, a ne improved atomization due to the Venturi effect achieved. Within the combustion chamber 22, a baffle plate 36 is further arranged, which has an advantageous curvature. This curvature in the direction of the burn-out zone 32 is advantageous because heat-induced spontaneous changes in form of the baffle plate 36 are thereby prevented. Due to the curvature of the baffle plate 36 in the direction of the Ausbrandzone 32 is also a sufficient space for the accommodation of the start chamber 18 is available. The wall defining the start chamber 18 is welded to the baffle plate 36.

FIG. 2 shows a perspective view of a burner flange with a heat shield inserted therein, and FIG. 3 shows a perspective view of a heat shield. It will also be pointed to components of the burner according to Figure 1 below. The heat shield 24 has a central opening 48 through which the fuel-air mixture discharged from the nozzle 12 enters the combustion chamber. Furthermore, a laterally arranged opening 34 for the passage of the ignition element 20 is provided. On the heat shield 24 fastening pins 44, 46 are further provided, on which the nozzle 12 is attached. The heat shield 24 also has a plurality of openings 26 through which secondary air can enter the combustion chamber 22. On the combustion chamber 22 facing side of the Hit¬ zeschildes 24 triangular air guide elements 28, 30 are provided. These cause due to the different angles to the radius of the heat shield 24, a division of the secondary air. A first group of air guiding elements, whose members are partially designated by the reference numeral 28, are at a large angle to the radius of the heat Shield 24 aligned, that is, their orientation is substantially or nearly tangential. On account of this orientation, the secondary air which passes through the corresponding openings 26 and whose outlet flow direction is indicated by an arrow, passes with high swirl past the baffle plate 36 into the burn-out zone 32. This air, which is provided with a high swirl, flows radially outer region of the burn-out zone 32 in the rear region of the combustion chamber 22, that is, in the region of the combustion chamber 22 facing away from the heat shield 24, and then with great turbulence in the central region back towards the baffle plate 36. Consequently, there is an advantageous Mixing of the gaseous components in the burn-out zone 32. Another group of air-guiding elements 30 has a smaller angle to the radius of the heat shield 24 in their orientation. These air guide elements are partially identified by the reference numeral 30. In addition, these air guiding elements 30 have a smaller angle to the surface of the heat shield 24 than the air guiding elements 28. Consequently, secondary air whose outlet flow direction is indicated by a further arrow is guided by these air guiding elements 30 into the core region of the flame with a small twist , which in particular favors a sta¬ biles burning behavior.

Thus, a novel spray burner is provided which is improved with regard to the possible installation positions, the starting behavior and the behavior in continuous operation. Furthermore, problems with regard to temperature-induced changes in shape of the baffle plate are avoided. The features of the invention disclosed in the foregoing description, in the drawings and in the claims may be essential to the realization of the invention both individually and in any combination.

LIST OF REFERENCE NUMBERS

10 burners

12 burner nozzle

14 fuel needle

16 combustion air supply

18 start zone

20 ignition element

22 combustion chamber

24 heat shield

26 opening

28 air guide

30 air guide

32 burn-out zone

34 opening

36 baffle plate

38 flame tube

40 burner tube

42 outer tube

44 fixing pin

46 fixing pin

48 opening

50 fuel feed

52 metal pipe

Claims

1. burner for a heater, in particular for use in motor vehicles, with

a burner nozzle (12) for supplying and atomising fuel, which has a fuel needle (14) for supplying fuel into the burner (10) and a combustion air supply (16) for supplying combustion air into the burner, and

a start zone (18), in which an ignition of the fuel takes place to start the burner,

characterized in that the outlet speed of the fuel is predetermined by the choice of the inner diameter of the fuel needle (14) such that fuel in a substantially unatomized form during a starting phase of the burner (10) forms the starting zone (18). reached.

2. Burner according to claim 1, characterized in that the inner diameter of the fuel needle (14) is between 0.5 and 0.7 mm.

3. Burner according to claim 1 or 2, characterized gekennzeich¬ net, that the inner diameter of the fuel needle (12) is about 0, 6 mm.

4. Burner according to one of the preceding claims, da¬ characterized in that the starting zone is formed as a start chamber (18) into which an ignition element (20) hinein¬ protrudes.

5. Burner according to one of the preceding claims, da¬ characterized by

that in addition to the primary air supplied from the burner nozzle by a between the burner nozzle (12) and a combustion chamber (22) arranged heat shield (24) secondary air can be supplied by provided in the heat shield openings (26) in the combustion chamber and

the openings are equipped with air guiding elements (28, 30).

6. Burner according to claim 5, characterized in that the air guide elements are formed by protruding in the direction of the combustion chamber integrally formed with the heat shield La- see (28, 30).

7. Burner according to claim 5 or 6, characterized gekennzeich¬ net, that the tabs (28, 30) are formed at different angles to the surface of the heat shield and / or the radius of the heat shield (24).

8. Burner according to one of claims 5 to 7, characterized ge indicates that the tabs (28, 30) are formed in groups at substantially identical angles to the surface of the heat shield (24) and / or the radius of the heat shield ,

9. Burner according to one of claims 5 to 8, characterized ge indicates

- That the burner (10) has a burn-out zone (32) and

the secondary air supplied to the burn-out zone has a higher swirl than the secondary air supplied to the starting zone.

10. Burner according to one of claims 5 to 9, characterized ge indicates that the heat shield (24) has an opening (34) for carrying out an ignition element.

11. Burner according to one of the preceding claims, da¬ characterized by

that the combustion chamber (22) is substantially axially symmetrical,

that in the combustion chamber (22) a baffle plate (36) is arranged, and

- That the baffle plate (36) has a predetermined curvature in the axial direction. - Ul -

12. Burner according to claim 11, characterized in that the curvature in the direction of the burn-out zone (30) is provided.

13. Burner according to claim 11 or 12, characterized gekennzeich¬ net,

the outer circumference of the baffle plate defines a plane and

the ratio between the maximum axial distance of the baffle plate from this plane and the diameter of the baffle plate is between 0.07 and 0.21.

14. Burner according to claim 13, characterized in that the ratio between the maximum axial distance of the baffle plate (36) from the plane and the diameter of the baffle plate (36) is approximately 0.14.