DE60107597T2 - PREMIXED BURNER WITH CURVED, NON-CIRCULAR END CAP - Google Patents

Abstract

The invention relates to a premix burner comprising a tubular burner body and an impermeable end cap. The impermeable end cap, which closes the tubular burner body, is welded to said tubular burner body The impermeable end cap is, according to the present invention is at least partially curved, each point of the impermeable end cap surface having a bending radius R and a material thickness T, said each R being larger than 3xT.

Description

technical area

The The present invention relates to a premix burner for combustion of premixed gas-air mixtures.

background the invention

premix are well known in the art. Some of these premix burners comprise a tubular burner body. Such a burner is described in US5022352 in which it is used to heat the Water from, for example, a central heating system is used. Furthermore, such burners are described in GB 1 258 784 and FR 2 676 269.

Such Premix burners comprise a tubular burner body which is preferably made of sheet steel and at its tubular burner body at least one, but usually several matrices of burning slots and / or -löchern having. The tubular burner body is closed at one side by a so-called end cap. If the end cap is not provided with burner slots, occur possibly the premix burner known from the prior art after a certain period of use some errors.

nowadays are the operating conditions of premix burners in general due to higher Requirements for the firing conditions stricter. Premix burners are capable of providing air-to-gas throughput today to regulate wide area. In particular, premix burners must be in the Be able to burn very small amounts of air-gas mixtures. Thus, the combustion takes place at a low air-gas mixture throughput very close to the tubular torch body. The lower the throughput, the closer the flame front is at the tubular burner body. One Part of the combustion energy heats the tubular burner body and the end cap, thus causing thermal expansion of the tubular burner body and the end cap. Especially if the end cap does not have burner slots (hereinafter referred to as "impermeable end cap") may it between both elements, which is the end cap and is the tubular torch body, due to, for example, different temperatures or different CTE the two elements come to a different thermal expansion. The tubular body becomes due to a closer flame front on higher Temperatures heated and is exposed to stronger thermal stresses. This Difference can cause heat cracks, especially in the welding area both elements lead.

Short illustration the invention

A Object of the present invention is to provide tubular burner body, the the strong thermal expansions at the connection between the tubular burner body and the impermeable Resist endcap stronger can, both parts made of metal, usually sheet steel are.

According to the present In the invention, a premix burner comprises a tubular burner body, a impermeable End cap and possibly a diffusion system located within the tubular burner body. The tubular burner body has on its surface at least a matrix of burner slots and / or holes. The premix air-gas mixture will over a suitable inlet, usually at the bottom of the tubular burner body, in blown the tubular burner body. As the tubular burner body to the other side closed by the impermeable end cap is, the air-gas mixture is forced to, possibly over one Air-gas diffuser, through the burning slots and / or holes too stream, where combustion takes place.

According to the present Invention has been found that the risk of heat cracks weld together an impermeable one End cap with the longitudinal end of (with this opaque End cap to be closed) tubular burner body for huge Part can be avoided, the impermeable end cap surface at least partially curved is while the bending radius of each point on the impermeable end cap surface is larger as three times the metal thickness of the material of the impermeable end cap.

Preferably Radii are used that are larger as four times the metal thickness of the material of the impermeable end cap. An additional one Advantage of this (this) big Radius (radii) is that the internal stresses in the impermeable End cap due to the shape of the impermeable end cap to a minimum be reduced.

Of the Edge of the opaque End cap and the longitudinal end of the tubular burner body must be tight engage each other.

Preferably, but not exclusively, this impermeable end cap is to be welded to the longitudinal end so that the curvature of the impermeable end cap surface to the outside tubular burner body runs. Hereinafter, the outward flow from the tubular burner body is referred to as "convex." The impermeable end cap is welded to the longitudinal end via the lower edge of the impermeable end cap The impermeable end cap may also be connected to the tubular burner body having an inwardly extending tubular burner body Hereinafter, the outward flow from the tubular burner body will be referred to as "concave."

The impermeable End cap can over their whole area bent be, with their bending radius is greater as three times the metal thickness of the material of the impermeable end cap. However, the bend radius for each point of the surface of the impermeable end cap differ. Preferably, the impermeable end cap is only at its outer edge, where the end cap is connected to the tubular torch body is bent. In the inner part or area of the surface of the impermeable end cap is the impermeable one End cap preferably substantially flat and has a bending radius which is essentially infinite. "Essentially infinite" should be considered more than ten times the maximum distance between two points of the edge the impermeable End cap to be understood.

If according to the present Invention such impermeable End cap with the longitudinal end of the tubular burner body with a concave or convex curvature welded is possible (enable) the relatively large (s) Radius (radii) of the impermeable end cap, the thermal expansion difference between the tubular burner body and the impermeable End cap during the combustion of the combustible gas / air mixture at the burner slots by slight change equalize the radius or radii. By this slight change will the occurrence of too big Tensions at the weld between the tubular burner body and the impermeable end cap prevented. As a result, can heat cracks be avoided.

Of the tubular burner body and the impermeable End caps are made of metal, for example metal or steel sheet, preferably stainless steel. Preferably, for both Elements used the same material. It can be a metal thickness Both, the tubular burner body and the impermeable End cap, which is between 0.2 and 1.5 mm, preferably between 0.2 to 1 mm, such as 0.3 mm, 0.5 mm, 0.6 mm, 0.8 mm or 1 mm, to be used.

Of the tubular burner body can through different techniques are formed. In general, one will tubular burner body Rolling out of a tube formed of a perforated metal sheet. The pipe is welded the sheet metal edges in the axial direction, for example by laser / TIG welding, sealed.

In The rule is impermeable End cap punched out of sheet metal.

Of the lower edge of the impermeable End cap and the longitudinal end of the tubular burner body can in dependence from the dimensions of the lower edge of the impermeable end cap compared to the perimeter of the longitudinal end of the tubular burner body, at both concave and convex curvature, in different ways welded together be.

If the inside of the lower edge of the impermeable end cap with the outside of the longitudinal end of the tubular burner body standing, become the impervious End cap and the tubular burner body preferably through Spot or laser welding welded together.

If the outside the lower edge of the impermeable End cap with the inside of the longitudinal end of the tubular burner body in engagement standing, become the impervious End cap and the tubular burner body preferably through Spot or laser welding welded together.

If the lower edge of the impermeable end cap has substantially the same circumference as the longitudinal end of the tubular burner body the impermeable End cap and the tubular burner body Laser or TIG welding welded together. she become, so to speak, area on area without overlap of material of the impermeable End cap and the tubular burner body welded.

For one It is obvious to a person skilled in the art that a large dimensional range, both concerning the Diameter and height of the premix burner can be obtained. As a rule, the diameter is greater than 0.5 cm and is preferably between 2.5 and 25 cm, but is mostly between 6 and 8 cm. A height of the tubular burner body is located preferably between 10 and 50 cm, usually between 10 and 20. Nevertheless, the tubular torch body should not as a circular one Having cross-section when cut longitudinally, be understood. It can other cross sections, such as elliptical or oval, be used.

Such The premix burner forming the subject of the invention can be used in Heating water or air Heaters, for example central heating systems and boilers, be used.

Short description the drawings

in the The invention will now be described with reference to the accompanying drawings in more detail described; show in it:

1 schematically a premix burner as subject of the invention;

2 a radial section of a tubular burner body which is part of a Vormischbrenners forming the subject of the invention;

3 an impervious end cap forming part of a premix burner forming the subject of the invention;

4a an axial section of a detail A of 1 ;

4b an axial section of an alternative embodiment of the present invention;

5a . 5b . 5c and 5d various welding options for connecting an impermeable end cap and a tubular burner body as subject of the invention;

6a . 6b . 6c . 6d and 6e various impervious end cap surfaces as subject of the invention.

description the preferred embodiments of invention

A part of a premix burner to which the present invention relates is disclosed in U.S.P. 1 shown. A tubular burner body 11 is at its longitudinal end 12 with an impermeable end cap 13 closed with a convex curvature. The impermeable end cap 13 and the tubular burner body 11 are in a welding area 14 welded together. A premixed air-gas mixture becomes a suitable inlet system by a known mixing system 15 fed. The premix air-gas mixture is passed through the tubular burner body 11 provided burning slots and / or holes 16 forced. When leaving the burning slots and / or holes 16 the premixed air-gas mixture is exposed to combustion.

A longitudinal section II 'at the longitudinal end 12 of the tubular burner body is in 2 shown. The longitudinal end 12 has an inner circumference 21 and an outer circumference 22 on. The material thickness of the tubular burner body is shown at T1. An impermeable end cap 13 is in 3 shown in more detail. The impermeable end cap 13 includes a bottom edge 31 with an inside 32 and an outside 33 , According to the invention, the impermeable end cap surface 34 curved. The impermeable end cap has a material thickness indicated by T2.

The thicknesses T1 and T2 may be different, but an equal thickness in a range of 0.2 to 1.5 mm, for example, in a range of 0.4 to 1 mm, especially 0.6 mm, is preferable. A preferred embodiment of a premix burner as in 1 has a height between 10 and 14 cm, for example 12 cm, of the tubular burner body and a diameter of 7 cm of the tubular burner body. Most preferably, the tubular burner body and the impermeable end cap are made of a stainless steel alloy.

An axial section of detail A of 1 is in 4a shown. An impermeable end cap 13 and a tubular burner body 11 are again in the welding area 14 welded together. This welding region has a thickness D. At least part of the impermeable end cap surface 34 is curved with a radius of curvature R. Preferably, this curved portion of the impermeable end cap surface is near the weld area 14 , The curvature of the impervious end cap surface extends outwardly from the tubular torch body (as indicated by arrow 41 shown).

An alternative axial section of another embodiment of a premix burner as the subject of the invention is shown in FIG 4b shown. There is an impermeable end cap with a curvature extending inwardly of the tubular burner body (as indicated by arrow 42 indicated).

In the in the 4a and 4b In embodiments shown, a radius in a range of 2 mm to 10 mm is preferred, depending on the material thickness of the impermeable end cap. In a most preferred embodiment with a material thickness T2 of the opaque end cap of 0.6 mm, a radius of not smaller than 2.5 mm is preferred.

As in the 5a . 5b and 5c There are various ways, the opaque end cap 13 with the tubular burner body 11 to weld. In 5a is the inside 32 the curved impermeable endcap 13 with the outer circumference 22 of the tubular burner body 11 engaged. The impermeable end cap surface is convex. The welding area 14 is characterized by an overlap of the impermeable end cap and the tubular burner body over a distance D. Preferably, D is kept smaller than 6 mm. This welding can be done by spot welding, but preferably laser welding is used.

In 5b takes the outside 33 the curved impermeable end cap 13 the inner circumference 21 of the tubular burner body 11 engaged. The impermeable end cap surface is convex. The welding area 14 is characterized by an overlap of the impermeable end cap and the tubular burner body over a distance D. Preferably, D is kept smaller than 6 mm. This welding can be done by spot welding, but preferably laser welding is used.

However, the best results can be obtained by welding the impermeable end cap and the tubular burner body "face to face" as in FIG 5c shown, achieve. In this case, the lower edge 31 the impermeable end cap 13 and the longitudinal end 12 of the tubular burner body 11 essentially the same scope. They are arranged together and welded together by TIG welding, but preferably laser welding. An additional advantage of this connection is that the two layers of material (one from the impermeable end cap and the other from the tubular torch body) at the weld area 14 , whose thickness is usually less than 6 mm, do not overlap. Preferably, surface-to-surface laser welding techniques are used to connect the impermeable end cap and the tubular burner body. Using this technique, the thickness D of the weld area becomes 14 reduced to a minimum. When the premix burner is heated due to combustion at a low rate of the premix air / gas mixture, the differential thermal expansion is due only to the differential thermal expansion at the tubular burner body and the impermeable end cap.

In 5d stands the outside 33 the curved impermeable end cap 13 with the inner circumference 21 of the tubular burner body 11 engaged. The impermeable end cap surface is concave. The welding area 14 is characterized by an overlap of the impermeable end cap and the tubular burner body over a distance D. Preferably, D is kept smaller than 6 mm. This welding can be done by spot welding, but preferably laser welding is used.

In the in 5a . 5b and 5d As shown, there is an additional thermal expansion difference caused by the presence of a region where both layers of material are present.

There are many different curvatures possible, with some examples in the 6a and 6b to be shown. 6a shows an impermeable end cap 13 with an elliptical curvature. There may be a different radius at each point of the impermeable end cap surface. An alternative is in 6b shown in the one impermeable end cap 13 a substantially flat area 61 and an area 62 at the edge of the impermeable end cap which is curved inwardly of the tubular body of the premix burner as subject of the invention. The bending radii in the area 61 and 62 are greater than three times the thickness of the material of the impermeable end cap. In the area 61 the bending radii are essentially infinite and are at least ten times the diameter 63 the circular impermeable end cap. It is obvious that the diameter of the tubular burner body with the diameter 63 is essentially identical.

Further, it is understood that if the tubular burner body does not have a circular cross-section, the edge of the impermeable end cap and the longitudinal end of the tubular burner body must be closely engaged. Of course, here are in area 61 the bending radii are substantially infinite and at least greater than ten times the largest distance between two points of the edge of the impermeable end cap.

6c . 6d and 6e show an impermeable end cap 13 with a W-shaped shape. In 6c here is only one part 64 the end cap 13 curved, and this curvature extends from the tubular burner body 11 outward. In 6d is a big part of the impermeable end cap 13 concave. 6e shows an impermeable end cap which is partially convex ( 65 ) and partly concave ( 66 ).

For one One skilled in the art will appreciate that the above examples are not limiting and that the tubular burner body has a circular radial section must have.

Claims (13)

Premix burner, which is a tubular Burner body ( 11 ) and an impermeable end cap ( 13 ) which closes the tubular burner body, wherein the impermeable end cap is welded to the tubular burner body and has an impermeable end cap surface (Fig. 34 ) which is at least partially curved, each point of the impermeable end cap surface having a bending radius R and a material thickness T, where R is greater than 3 × T in each case. A premix burner according to claim 1, wherein the curvature of the impermeable end cap surface ( 34 ) is at least partially concave. A premix burner according to claim 1, wherein the curvature of the impermeable end cap surface ( 34 ) is at least partially convex. A premix burner according to claim 1, wherein the curvature of the impermeable end cap surface ( 34 ) is at least partially concave and partly convex. A premix burner according to any one of claims 1 to 4, wherein the impervious end cap surface ( 34 ) has a substantially flat area. A premix burner according to claim 4, wherein the impervious end cap surface ( 34 ) a substantially flat area ( 61 ), wherein the bending radii in the substantially flat region are greater than ten times the maximum distance between two points of the edge of the impermeable end cap. Premix burner according to claims 1 to 6, wherein the impermeable end cap ( 13 ) a lower edge ( 31 ), wherein the tubular burner body ( 11 ) a longitudinal end ( 19 ) and the lower edge and the longitudinal end are welded together without overlap. Premix burner according to claims 1 to 7, wherein the impermeable end cap ( 13 ) and the tubular burner body ( 11 ) are welded together by laser welding. Premix burner according to claims 1 to 7, wherein the impermeable end cap ( 13 ) and the tubular burner body ( 11 ) are welded together by spot welding. Premix burner according to claims 1 to 7, wherein the impermeable end cap ( 13 ) and the tubular body ( 11 ) are welded together by TIG welding. Premix burner according to claims 1 to 10, wherein the tubular burner body ( 11 ) has a height in a range of 10 to 50 cm. Premix burner according to claims 1 to 11, wherein the tubular burner body ( 11 ) has a circular cross section with a diameter in a range of 0.5 to 25 cm. Use of a premix burner according to claims 1 to 12 in a central heating or in a water heating system.