Process for combustion of liquid fuel in a burner

The present invention relates to a method for the combustion of liquid fuel in a burner without a premixing section according to the preamble of claim 1. It also relates to a burner for carrying out this method.

STATE OF THE ART

From EP-A1-0 210 462 a burner is known, which is formed of at least two charged with tangential air inlet double curved hollow sectional cone bodies. These bodies are folded in the direction of flow along kegelstrahlig outwardly opening diagonals. The curved rebate side forms an inner cone increases in Abströmungsrichtung conical inclination, while the other curved rebate side forms an outer cone, with in Abströmungsrichtung decreasing cone inclination. The inner cone end bear, along their entire axial extent, each have a fuel line for the supply of the gaseous fuel, flowing through a plurality of fuel nozzles into the interior of the burner to mix there with the tangentially inflowing combustion air. The burner further has a separate supply of a liquid fuel, which is to do here with a dual burner. The injection of the liquid fuel is directed axially to the outer cone, such that there forms depending on the strength of the injection, a different length fuel film. Besides the natural evaporation of the liquid fuel by the prevailing radiant heat, an important mixing is handled by the tangentially guided combustion air, which the fuel film in layers rolls up by their swirling motion in the axial direction, whereby the generation of a strong mixing is unnecessary. Because the momentum of the injection is adjusted liquid fuel load of the machine, the mixture is never too lean or too rich.

Two objectives can thus be reached directly:<ul><li>The advantages of a premix burner, namely little NO_x and CO, make their appearance.</li><li>A good flame stability in a wider range of operation is ensured.</li></ul>

Further results from the structural design of this burner a vortex flow which is drallarm in the center but has a Axialgeschwindigkeitsüberschuss. Because now greatly increases the number of twists in the axial direction and reaches the breakdown value and the critical value at the end of the burner, this results in a stable position vortex backflow.

Although the benefits of acknowledged here burner not be denied, it has been shown that the NO_x- And CO emission values, even though they are already deeply by its use must be over the legal limits, future decreases substantially. Furthermore, it has also been shown that coking of the outer cone can not be excluded from the Oelverbrennung, and the fuel injection is not easy to handle.

Furthermore, the Oeleindüsung is structurally solved relatively expensive. But the design of the folded cone sections and their vote is another not easy to handle.

OBJECT OF THE INVENTION

This is where the invention. The invention, as characterized in the claims, the task is based is to simplify, in a method and a burner of the above mentioned types of the physical configuration of the burner and simultaneously the NO_xEmission levels from the combustion vormischartigen to minimize liquid fuel, without the flow field in the burner to change with the stable Wirbelrückströmzone.

The main advantages of the invention regarding the design can be seen in the fact that in the absence of the usual premixing no risk of restrike is to be feared in the burner. Furthermore, eliminating the well-known problems in the establishment of swirl cups mixed stream, for example, those shortcomings caused by burning of deposits with the destruction of the twist scoops.

The essential advantage of the invention with respect to NO_xEmission values ​​can be seen in the fact that this abruptly to a fraction of its fall, which has been considered until now as the maximum attainable. Thus, the improvement has not merely a few percentage points, but now it is moving in the order of infinitesimal 10-15% of the legal limit, which is a completely new quality level is achieved.

Another advantage of the invention arises out of the possibility that the inventive burner can also be used in gas turbines whose pressure ratio _ _ about 12 is so high that no preliminary evaporation of the liquid fuel more is inherently possible because previously used auto-ignition of fuel would. Finally, the burner according to the invention can also be used even in those cases where no or only an insufficient for vaporization air preheating can be achieved.

Last but not least is also to be seen a significant advantage of the invention that the inventive burner consists of a few ingredients that are easy to manufacture and assemble.

Advantageous and expedient further developments of the inventive task solution are indicated in the dependent claims.

In the following an embodiment of the invention will be explained with reference to the drawing. All elements which are required for direct understanding of the invention are omitted. The flow directions of the various media are indicated with arrows. In the different figures, the same elements with the same reference numerals.

BRIEF DESCRIPTION OF THE INVENTION

It shows:<ul><li>, Cut Fig. 1 shows a burner in perspective accordingly and</li><li>Fig. 2, 3, 4 show corresponding sections through the planes II-II (Fig. 2), III-III (Fig. 3) and IV-IV (FIG. 4), these sections only a schematic, simplified illustration of the burner are.</li></ul>

DESCRIPTION OF THE EMBODIMENTS

To better understand the structure of the burner, it is advantageous if the reader to Fig. 1 draws on the individual sections in FIG. 2-4 simultaneously. Furthermore, so as not to make unnecessary cluttering Fig. 1, are in their baffles 2-4 schematically shown in Fig. 21a, 21b has only hinted added. In the following 2-4 are noted in the description of FIG. 1 selectively, as required, to the rest of Fig..

The burner according to FIG. 1 consists of two half hollow Teikegelkörpern 1, 2, which are offset from each other. The offset of the respective central axis 1b, 2b of the partial conical bodies 1, 2 provides on both sides in mirror-image arrangement one tangential air inlet slot 19, 20 free, (Fig. 2-4), through which the combustion air 15 into the interior of the burner, ie into the conical cavity fourteenth The two partial conical bodies 1, 2 each have a cylindrical initial part 1a, 2a, offset also analogous to the partial conical bodies 1, 2 which extend to each other so that the tangential air inlet slots 19, 20 are available from the beginning. In this cylindrical initial part 1a, 2a, a nozzle 3 is accommodated, the fuel injection 4 coincides with the narrowest cross section of the conical cavity formed by the two partial conical bodies 1, 2 fourteenth Certainly every burner can be purely conical, ie without cylindrical initial parts 1a, 2a, performed. Both partial conical bodies 1, 2 each have a fuel conduit 8, 9, which are provided with openings 17 through which the gaseous fuel 13 which is added by the tangential air inlet slots 19, 20 combustion air flowing 15th The position of these fuel pipes 8, 9 is schematically shown in FIG 2-4 forth. The fuel conduits 8, 9 are at the end of the tangential air inlet slots 19, 20 are mounted so that there takes place also the admixture 16 of the gaseous fuel 13 with the inflowing combustion air 15 , The combustion space end 22, the burner has a collar-shaped serving as an anchor for the partial conical bodies 1, 2 end plate 10 with a number of holes 11 through which, if necessary, dilution air or cooling air can be 18 applied to the front part of the combustion chamber 22 or its wall. The flowing through the nozzle 3 liquid fuel 12 is injected at an acute angle into the conical cavity 14, such that adjusts the burner exit plane a very homogeneous conical fuel spray, is being strictly ensured that the inner walls of the partial conical bodies 1, 2 from the sprayed liquid fuel 12 does not wet. The fuel injection 4, there may be an air-assisted nozzle or a pressure atomizer. The conical liquid fuel profile 5 is enclosed by a rotating combustion air flow flowing tangentially 15th In the axial direction, the concentration of the liquid fuel 12 is continuously reduced by the blended combustion air 15th If gaseous fuel burned 13/16, formation of the mixture with the combustion air 15 directly at the end of the air inlet slots 19, 20. In the injection of liquid fuel 12 in the region of the vortex, ie in the region of the backflow zone 6, the optimum, homogeneous fuel concentration over reaches the cross-section. Ignition takes place at the apex of the reverse 6. Only at this point can a stable flame front 7 arise. A check of the flame into the interior of the burner, as latent in the case of premixing, whereas with complicated flame holders remedy is there wanted is not to be feared here. If the combustion air preheated 15, then sets a natural evaporation of the liquid fuel 12 before the point at the output of the burner is reached, at which can take place, the ignition of the mixture. The degree of evaporation is, of course, depends on the size of the burner, the drop size distribution and the temperature of combustion air 15th Regardless however of whether or not the homogeneous Tropfenvormischung by combustion air 15 low temperature, or in addition, only a partial or complete droplet evaporation is achieved by preheated combustion air 15, the NOx and CO emissions are low and when the excess air is at least 60%. In the case of complete evaporation before entry into the combustion zone, the pollutant emission values ​​are lowest. The same applies to the near-stoichiometric operation if the excess air is replaced by recirculating exhaust gas. When designing the partial conical bodies 1, 2 with respect cone inclination and the width of the tangential air inlet slots 19, 20 are narrow limits to be observed, so that with its reverse 6 adjusts the desired flow field of the air in the region of the burner mouth for flame stabilization. Generally it can be said that a reduction of the air inlet slots 19, 20, the backflow zone 6 further upstream shifts, which then, however, would the mixture ignites earlier. After all, here to say that once geometrically fixed backflow 6 itself is in a stable position, because the swirl number increases in the flow direction in the area of ​​the conical shape of the burner. The construction of the burner is ideally suited, for a predetermined length of the burner, the size of the tangential Lufteintrittsschllitze 19 to change 20 by the partial conical bodies 1, 2 are fixed by means of a releasable connection with the end plate 10th By radial displacement of the two partial conical bodies 1, 2 increases or decreases apart or be enlarged to the distance between the two central axes 1b, 2b, and accordingly changes the gap size of the tangential air inlet slots 19, 20, as shown in Fig. 2-4 particularly well apparent. Of course, the partial conical bodies 1, 2 are also in another plane displaced to each other, whereby even an overlap of the same can be controlled. Yes, it is even possible, the partial conical bodies 1, to move spirally eineinander by an opposite rotational movement. 2 So now you have it in your hands, 20 to vary the shape and size of the tangential air inlets 19 as desired, whereby the burner is universally applicable without changing its length.

From FIGS. 2-4, the position of the guide plates 21a, 21b is shown. They have a flow initiation functions whereby they different lengths each end of the partial conical bodies 1 and 2 extend, in the direction of inflow of the combustion air 15th The canalization of the combustion air into the conical cavity 14, by opening or closing the guide plates 21a, 21b are optimized about the pivot point 23, in particular this is then necessary when the original gap size of the tangential air inlet slots 19, 20 is changed.