Patent Application
20100291495
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.
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.
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.
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:
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.
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
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
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
With reference to
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.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| PD2007A000388 | Nov 2007 | IT | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP08/64956 | 11/4/2008 | WO | 00 | 5/18/2010 |
