WO2009065733A1

WO2009065733A1 - A burner, specifically a premix burner

Info

Publication number: WO2009065733A1
Application number: PCT/EP2008/064956
Authority: WO
Inventors: Gianfranco Scribano; Maurizio Beghi
Original assignee: Sit La Precisa SpA
Current assignee: Sit La Precisa SpA
Priority date: 2007-11-19
Filing date: 2008-11-04
Publication date: 2009-05-28
Anticipated expiration: 2010-05-19
Also published as: ITPD20070388A1; US20100291495A1; CN101861496A; EP2227655B1; EP2227655A1

Abstract

A burner, particularly for combustible gas with premixing, comprises a cylindrical burner head (3) designed to be housed in a combustion chamber (4) of a heating apparatus, on which an air and gas mixture supplied to the combustion chamber (4) is burnt, the head (3) including a cylindrical shell (9) with through apertures, fixed at a first axial end by a connecting flange (8) to a shutter element (7) intended to seal the combustion chamber (4), while its opposite axial end has a solid end wall (3a) which seals the head (3), an element (10) for distributing the air and gas mixture, positioned inside the burner head (3) and intended to distribute the flow of combustible mixture reaching the burner on to the burner head (3). The distributor element comprises a platelike portion (11) extending as a continuation of said connecting flange (8) and extending substantially in an orthogonal direction to the axial direction of extension of the cylindrical head, the platelike portion (11) having through apertures (12) for distributing the mixture to the burner head (3).

Description

A burner, specifically a premix burner

Technical field

The present invention relates to a burner and specifically to a premix gas burner having the characteristics described in the preamble of main Claim 1. Technological background

In this specific technical field, there is a known way of making a premix gas burner whose burner head is intended to be housed in a combustion chamber in a position facing a heat exchanger which, when contacted by the flames of the burner, heats the fluid passing through it. Typically, the burner is connected to a shutter or similar element for sealing the combustion chamber.

In a known kind of burner of the aforesaid type, the burner head of the burner is made in a cylindrical shape which can extend into a combustion chamber, which is also of cylindrical shape, the cylinders preferably being coaxial with each other. In this configuration, the cylindrical shell of the burner head is provided with through apertures designed to allow the combustible air and gas mixture to pass through them, and faces the coils of the exchanger in an annular space of the chamber which is substantially delimited by the outside dimensions of the cylindrical burner. The burner head is generally sealed by a solid end wall, at the opposite end to the shutter. Typically, a burner of the aforesaid type requires an internal distributor element which is designed to distribute the combustible mixture uniformly to the burner head. There is a known way of making the distributor in a cylindrical shape, coaxial with the burner head, and extending axially inside the burner head. At the end of the head, the distributor is also sealed by a base supported and centred on the end of the head, for example by engagement with a pin or screw projecting axially from the end of the head towards the distributor. The base wall of the distributor is normally solid, but alternatively some through holes may be provided to allow a small flow of mixture to pass through, with the primary purpose of cooling the end wall of the head. In a known application of this type, the distributor and the burner head are both connected in a known way to the sealing shutter, by means of a connecting flange which is coaxial with these elements and which is provided with a large central hole, the size of which is substantially equal to the cross section of the distributor, to allow the mixture to flow directly to the distributor and from there to the burner head.

In other known applications, a Venturi pipe can also be provided inside the distributor, with the principal purpose of reducing any noise created in the flow of the mixture supplied to the burner in some stages of operation. The Venturi pipe, where provided, is also fixed to the flange, by a mechanical connection for example, and extends axially into the distributor, coaxially with the distributor and the burner head.

One of the main limitations of the aforesaid known configurations is the structural complexity created by the number of components required in the burner assembly. As described above, a basic configuration requires not less than six components, including the cylindrical shell of the distributor, the end wall of the distributor, and the pin for centring this wall on the end of the head, which must be provided separately and then suitably connected to each other. Description of the invention A principal object of the invention is to provide a premix burner which is structurally and functionally designed to overcome the limitations described with reference to the prior art, and which is designed, in particular, to allow greater structural simplicity for the same level of performance, thus reducing costs both in terms of assembly time and in terms of the manufacturing and assembly costs of the individual components in the production of the burner. This object is achieved by the invention by means of a burner made in accordance with the following claims. Brief description of the drawings

Other features and advantages of the invention will become clear from the following detailed description of a preferred example of embodiment thereof, illustrated, for the purpose of guidance and in a non-limiting way, in the appended drawings, in which :

Figure 1 is a perspective view of a burner made according to the present invention;

Figure 2 is a perspective view in partial section of the burner of Figure 1; - Figure 3 is a view in axial section of the burner of the preceding figures;

Figure 3A is a view corresponding to that of Figure 3, in a variant embodiment of the invention;

Figure 4 is a view in front elevation of a detail of the burner of the preceding figures; - Figure 5 is a perspective view of the detail of Figure 4.

Preferred embodiments of the invention

With reference to the cited drawings, the number 1 indicates the whole of a burner, particularly a burner for combustible gas of the premixed type, made according to the present invention. The burner comprises a burner body 2 with a burner head 3 where the air and gas mixture supplied to the burner is burnt, with the aid of a fan device (not shown) for example.

The burner is designed to be housed in a combustion chamber 4, which is shown only schematically, of a heating apparatus (not shown), in which a heat exchanger 5 is also housed, the exchanger being provided with a tube bundle 6 in which a working fluid circulates and is heated by means of the burner. The burner body 2 is fixed to a shutter element 7 which is provided to seal the combustion chamber and which is removably connected to a static structure of the chamber. The number 8 indicates a connecting flange for fixing the burner body to the shutter, as will be described clearly below. Through holes 8a are provided in a fastening base of the flange 8 for fixing it to the shutter 7. Figure 3 is a schematic illustration of the burner configuration described above. More specifically, the burner head 3 has a cylindrical shape, with its principal axis indicated by X in the drawings, and its cylindrical shell 9 is provided with through apertures, with an alternation of slots and holes (see Figure 1) for the passage of the combustible air and gas mixture, the flame being ignited in the proximity of these apertures outside the burner head.

The cylindrical head is sealed at one of its axial ends by a solid end wall 3a, while the opposite axial end of the head 3 is fixed to the connecting flange 8, with which it is coaxial.

The number 10 indicates the whole of an element for distributing the combustible mixture to the head 3, this element being positioned inside the head and having through apertures for distributing the flow of mixture, as explained more fully below. According to a principal feature of the invention, the distributor element 10 comprises a platelike portion 11, in which are provided a plurality of through apertures 12 having the function of distributing the combustible mixture in the direction of the head 3, said portion extending to form a continuation of the flange 8 and extending orthogonally to the direction X of axial extension of the head 3.

Conveniently, the platelike portion 11 has a flat profile of predetermined thickness, with a circular shape, as shown in Figure 4. Preferably, the portion 11 is made in one piece with the flange 8, the latter extending to form an annular surround of the portion 11 of the distributor. Alternatively, the portion 11 can be formed separately from the flange, for example as a disc-shaped body which is intended to be fixed to the flange 8 (produced, for example, in the form of an annular collar).

The portion 11 also preferably extends into the connecting flange, by means of a limited axial projection from the plane of the connecting flange 8, as shown in Figure 3. This projection (in the axial direction X) can be provided by means of a cylindrical formation 13, which is sleeve-shaped and coaxial with the portion 11, thus forming a linking section between said portion 11 and the connecting flange 8. Conveniently, the cylindrical section 13 has a solid-walled shell, without through apertures. The flange and the portion 11 are also preferably made integrally with the cylindrical formation 13.

With reference to Figure 3, where L indicates the axial dimension of the head (the length measured along the axis X from the flange 8) and Ll indicates the distance along the axis X between the platelike portion 11 and the flange 8, the positioning of this portion is preferably chosen in such a way that the ratio Ll/L is preferably less than or equal to 0.5. Figure 3A shows a variant embodiment, in which the portion 11 is positioned on the opposite side of the flange 8 from the head 3. In this case also, the ratio Ll/L is preferably chosen to be equal to or less than 0.5. The number and size of the distribution apertures 12, formed so as to pass through the thickness of the platelike portion 11, are selected in such a way that the total passage cross section of the mixture is not less than 70% of the total distribution cross section of the mixture required for a predetermined power of the burner, in order to ensure the correct operation of the burner. If the apertures 12 are not exclusively formed in the portion 11, they can be provided in the shell of the cylindrical sleeve formation 13.

The apertures 12 are preferably made in the form of circular through holes passing through the platelike portion 11 (the axes of the holes being parallel to the axis X), the holes being formed in a plurality of concentric rings (concentric with the axis X), and being distributed at regular angular intervals along each ring. Figure 4 shows a preferred configuration, in which six concentric rings are provided, and in which the cross sections of the individual holes in each ring increase from the outermost ring towards the ring closest to the axis X. Additionally, the passage cross sections of all the holes 12 of each ring are identical. In a preferred option, each ring of holes 12 also has the same total passage cross section, thus ensuring the most uniform possible distribution of mixture towards the burner head. Clearly, different distributions of mixture in the head, for example those designed to create distinct regions with flames having different velocities, can be provided by varying the total cross section of one ring with respect to the others. Alternatively, the apertures 12 can be shaped differently, for example in the form of through slots.

Additionally, the number 14 indicates a central hole, formed as a through hole in the portion 11 and coaxial with the axis X, the passage cross section of this hole being added to that delimited by the rings of holes 12.

The distribution of the apertures 12 can also be chosen to modify the flame on the burner head in a suitable way, in order to simulate the effect created by a Venturi pipe provided in known solutions in addition to the distributor element. Tests conducted by the present applicant have demonstrated that the distribution of the mixture towards the burner head is carried out by the platelike distributor element 11 described above with a flame combustion efficiency and performance levels at the head 3 equal to those provided by the cylindrical distributor configurations conventionally provided in the prior art solutions. In this connection, it should be noted that the invention requires a smaller number of burner components, since the conventional cylindrical distributor is replaced by the platelike distributor element described above, which is substantially formed in the flange connecting the burner head to the shutter, resulting in an advantageous reduction in the time and cost of manufacturing and assembling the burner components.

By providing a simplified construction relative to the known solutions, the invention thus achieves the proposed objects and yields the aforementioned benefits.

Claims

1. A burner, particularly for combustible gas with premixing, comprising : a cylindrical burner head (3) designed to be housed in a combustion chamber (4) of a heating apparatus, on which an air and gas mixture supplied to the combustion chamber (4) is burnt, said head (3) including a cylindrical shell (9) with through apertures, fixed at a first axial end by a connecting flange (8) to a shutter element (7) intended to seal the combustion chamber (4), while its opposite axial end has a solid end wall (3a) which seals said head (3), an element (10) for distributing the air and gas mixture, positioned inside the burner head (3) and intended to distribute the flow of combustible mixture reaching the burner on to the burner head (3), characterized in that said distributor element comprises a platelike portion (11) extending as a continuation of said connecting flange

(8) and extending substantially in an orthogonal direction to the axial direction of extension of the cylindrical head, said platelike portion (11) having through apertures (12) for distributing the mixture to the burner head (3).

2. A burner according to Claim 1, in which said portion (11) of the distributor element extends into the connecting flange (8).

3. A burner according to Claim 1 or 2, in which the total cross section of the through apertures (12) in said portion (11) of distributor forms not less than 70% of a predetermined cross section of distribution of the mixture towards the burner head (3).

4. A burner according to any one of the preceding claims, in which said portion (11) of the distributor element (10) is coaxial with the burner head (3).

5. A burner according to any one of the preceding claims, in which the positioning of said portion (11) of distributor with respect to the head

(3) is chosen in such a way that the ratio between the axial distance (Ll) of the portion from a fastening base of the connecting flange (8) and the axial length (L) of the head measured from the fastening base of the flange is less than or equal to 0.5.

6. A burner according to any one of the preceding claims, in which said portion (11) is made in one piece with said flange (8).

7. A burner according to any one of the preceding claims, in which said portion (11) of distributor is disc-shaped.

8. A burner according to Claim 7, in which said portion (11) of the distributor element is platelike with a flat profile.

9. A burner according to any one of the preceding claims, in which said portion (11) of the distributor element is linked to the flange (8) by means of a sleeve formation (13) coaxial with it.

10. A burner according to Claim 9, in which said sleeve formation (13) has a shell with a cylindrical profile having a predetermined axial extension towards the end wall of the burner head.

11. A burner according to Claim 10, in which said sleeve formation (13) is integral with said flange (8) and with said portion (11) of the distributor element.

12. A burner according to any one of the preceding claims, in which the distribution apertures (12) passing through said portion (11) of the distributor element are formed along a plurality of concentric rings and are distributed at regular intervals along each ring.

13. A burner according to Claim 12, in which the cross sections of the through apertures (12) of each ring are equal to each other.

14. A burner according to Claim 13, in which the characteristic passage cross section of the apertures (12) of each ring increases from one ring to the next, towards the central axis of said portion.

15. A burner according to any one of the preceding claims, in which said through apertures (12) are shaped in the form of circular holes.

16. A burner according to any one of Claims 12 to 15, in which a central through hole (14) coaxial with the principal axis of said portion (11) of distributor element (10) is provided, in addition to said plurality of concentric rings of through apertures.

17. A burner according to any one of Claims 12 to 16, in which the total cross sections of the apertures of each ring are equal to each other.