Premixing gas burner

(42) Date of commencement of the patent: 15. 4.1994 (45) Date of issue: 27.12.1994 (56) Documentation:

(73) Patent owner:

A7-PS 35044 (E)

US-PS 992181 US-PS1456250

DE-GS3S39974 Gc-PS 615822 US-PS1563049 US-PS1878427

VAILLANT SOCIETY M.8.H. A-1233 VIENNA (AT).

(54) PREMIXED GAS BURNER (57) Pre-gas burner with at least one gas nozzle, which generates a kegelfohrigen gas jet having a Öffnungswihkel, and at least one mixing tube. In order to keep the mixing ratio between fuel gas and Priosrluft largely constant over the entire load and operating range of the burner in such a burner, it is provided that in the front end inlet near ßereich the mixing tube (6), in Strönungsrichtung of the gas immediately before the At least one further opening (43) is provided on the area of ​​the impingement of the gas jet on the inner wall of the mixing tube (6).

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The invention relates to a premix gas burner according to the preamble of the independent claim.

Such Vormischgasbrenner are atmospherically burning known in a variety of designs, that is, the gas is supplied through a nozzle under pre-pressure (natural gas, LPG or city gas), and the air is entrained through the gap between the gas nozzle and the entrance of the mixing tube by the gas jet pulse and mixed.

It has been found that the mixing ratio between gas and primary air varies depending on the operating state of the burner, that is, depending on the height of the gas jet pulse and the temperature of the burner.

With increasing demands on flame stability and low-emission combustion, there is a need to adjust the mixing ratio between fuel gas and primary air very precisely and constantly over the entire load and operating range of the burner.

In the known premixed gas burners, the mixing tubes usually have dense walls and are provided only at the gas nozzle facing end face with an opening into which the gas jet emerging from the gas jet enters and entrains the surrounding air. In these known burners, the entire air must be entrained before the entry of the gas jet into the mixing tube, or it can absorb the gas jet after its entry into the mixing tube no more air. However, this results in that only a part of the gas jet emerging from the gas jet can actually contribute to the intake of the surrounding air. However, this leads to the fact that with increasing temperature of the burner entrained by the outflowing gas air mass decreases, so that the mixing ratio changes accordingly. Since only a portion of the gas stream contributes to the suction of the surrounding air, the ratio of gas to air changes with increasing temperature of the burner accordingly strong.

Mixing tubes with wall openings are known for example from GB-PS 615 822 and US-PS 1 456 250. The formation and arrangement of these openings in relation to the shape of the gas jet, however, are disadvantageous in that no optimization of the same is provided, so that the intended effect, namely the intake of additional air, is relatively small.

The aim of the invention is to avoid these disadvantages and to propose a burner of the type mentioned, in which the suction of air is optimized, whereby the mixing ratio between fuel gas and primary air over the entire load and operating range of the burner remains largely constant.

This is achieved by the characterizing features of the independent claim according to the invention.

By this measure it is achieved that the gas jet can also suck in the area of ​​the mixing tube in an effective manner air. This results in the advantage that due to the vortex formation caused by the suction of the air virtually all of the gas jet emerging from the gas nozzle can contribute to the suction of the air. As a result, the temperature increase of the air with increasing burner temperature affects the mixing ratio less than in the known burners, in which only a part of the gas jet emerging from the gas jet contributes to the suction of the air.

According to a further feature of the invention can be provided that the openings are formed as a window breaking through the mixing tube, resulting in a particularly simple solution in terms of design.

The windows are arranged in a region of the mixing tube, in which there is a suppression by the incoming gas jet, so that in addition a considerable amount of air can be sucked in through the windows.

According to another feature of the invention can be provided that the mixing tube is formed in two parts, wherein the two parts are telescopically nested in compliance with an annular gap forming the opening and are preferably held against each other axially displaceable.

These measures result in a simple construction, whereby it is also possible to control the adjustment of the two parts of the mixing tube in dependence on the temperature of the burner. As a result, a particularly extensive consistency of the mixing ratio of air and gas over a very large operating range of the burner can be ensured.

The invention will now be explained in more detail with reference to the drawing.

Showing:

1 is a plan view of a section of a premix gas burner according to the invention, and FIG. 2 is a plan view of a detail of another premix gas burner according to the invention.

In a first embodiment of a burner according to the invention according to FIG. 1, a mixing tube 6 is provided, which is provided in its inlet region with a section 40 which widens to a nozzle 8, which merges into another section 41 which widens in the direction of flow. there

AT 398 472 Β openings 43 are provided in the form of window-like openings of the wall of this section 42 in a lying between these sections 40 and 41 cylindrical portion. The openings 42, viewed in the inflow direction of the gas, are arranged on the inner wall of the mixing tube 6 immediately before the region of impingement of the cone-shaped gas jet (59) having an opening angle 59.

In the region of the window 42, a suppression is caused by the gas jet, whereby a larger volume of air can be sucked by the gas jet.

The burner of FIG. 2 differs from that of FIG. 1 in that the opening 43 is formed in the, seen in the inflow of the gas, the front portion of the widening portion 41 as an annular gap, but here again the opening 43 in Inflow direction of the gas seen, is arranged immediately before the region of the impact of the gas jet on the inner wall of the mixing tube 6.

For both figures:

The gas nozzle 8 is aligned coaxially with the mixing tube 6 and arranged on a line 10, via which the supply of the fuel gas takes place.

The gas nozzle 8 has an annular nozzle opening 50. In this case, a truncated cone 51 is arranged in the center of the gas nozzle 8, which is inserted into a conical bore 52 of the gas nozzle 8, wherein the wall of this bore 52 forms the outer circumferential surface of the annular gap 53 of the nozzle 8.

This truncated cone 51 is directed with its thinner end against the line 10.

The gas exits from the conduit 10 in the form of a conical shell. Depending on the choice of the gap width of the annular nozzle opening 50, the gas exits in a more or less thick conical shell.

The opening angle 59 is selected so that the gas emerging from the gas nozzle 8 impinges on the inner wall of the mixing tube 6 in the flow direction immediately behind the opening (s) 43.

By the gas jet, the surrounding air is entrained in the region of the window 43, wherein it comes to turbulence, which completely detect this due to the relatively small wall thickness of the gas cone sheath. This results in a very good mixing of the gas with the surrounding air.

The two parts 41 and 40/42 of the mixing tube 6 according to FIG. 2 can be held axially displaceable relative to one another, wherein an actuator controlled by the temperature of the burner can be present.