Homogeneous mixture formation by swirled injection of the fuel

The invention relates to a fuel injector for a gas turbine according to the features of the preamble the main claim.

In detail, the invention relates to a fuel injector for a gas turbine with a flow passage for the air flow, its flow to a plurality of walls Fuel orifices for injecting fuel into the Air flow are formed.

The mixture preparation of fuel and air in gas turbine combustors carried out in very different ways and can in principle concerning their application to stationary Gas turbines or aircraft gas turbines and thus respect distinguish the different requirements. To reduce pollutant emissions mainly of nitrogen oxide emissions but has generally the fuel with as much Air are premixed to a lean by excess air adjust combustion state marked. This mixture is problematic because they stabilizing the combustion can affect mechanisms.

The stabilization of the combustion takes place almost exclusively with air twist, the recirculation of partially burned gases allows. The fuel is often centrally through a nozzle introduced, which is mounted on the central axis of the atomizer is. The fuel is in this case often with considerable Overpressure injected into the air flow to provide enough to achieve penetration and as much air with fuel to premix. This pressure atomizers have to a function to atomize fuel directly. some However, shapes of an injector to the fuel as completely sprayed onto an atomizer will. The fuel is in the air on an atomizer accelerated and at the downstream end of this lip torn into small drops and mixed with the air.

Another possibility of the fuel to this atomising lip apply, there is a so-called film applicator, wherein fuel as possible uniformly distributed in a film becomes.

A further possibility of the fuel as intensively as possible to mix a large part of the air is in a decentralized injection from the outer boundary of the flow channel, which performs the bulk of the air. This can of an atomizer or even from the outer nozzle contour carried out. This injection is characterized in that unlike a film applicator of fuel learn a defined penetration into the main air flow should.

Both the fuel injection nozzle or with a central Pressure atomisers, as well as an application as a film on a Film applicator should be optimized such that the total possible the atomizer air flowing through homogeneously with fuel is mixed before combustion. Characteristic for the low-pollution, especially low-nitrogen oxide, combustion is a lean, premixed with air excess fuel preparation. The consequence are fuel nozzles, the large flow cross-sections own to the high proportion of air to fuel to premix. Due to the size of this Fuel nozzle and the limited capacity of the fuel jets and sprays, at a central injection to penetrate the growing air ducts and thus a homogeneous distribution of the fuel-air mixture to reach, novel concepts of fuel injection and premix required.

The homogeneous distribution and introduction of the fuel in large airflow channels requires a decentralized injection from as many fuel orifices to the Flow walls of the air flow must be arranged. A high number has the consequence that these openings very are small, through to blockages or obstructions may cause fuel impurities. Since these burners at higher loads of the engine are often switched on, can splinting by decomposition products of the fuel caused if after previously erfolgtem agent or High-load operation of the burner operation by these fuel orifices is switched off and the fuel nozzle in the remaining fuel is heated and decomposed. The fuel nozzle often by a radially very uneven Velocity and mass flow distribution in. Due to the swirl of the air, which to stabilize the subsequent combustion is needed is the local air mass flows in the radially outer boundary wall the biggest. If the fuel from a few openings introduced into the flow, on the one hand is the homogeneity the fuel in the air circumferentially impaired but on the other hand, the fuel can very deep into the flow entering and thus unintentionally in regions mix and evaporate in which not enough air to Available. This may be particularly at a decentralized Injection, as described above occur.

The invention has the object of providing a fuel injector to provide the aforementioned type, which with a simple structure and more reliable applicability avoids the disadvantages of the prior art and optimized Mixing of fuel and air ensures.

According to the invention the object is achieved by the combination of features solved the main claim, the subclaims show further advantageous embodiments of the invention.

According to the invention it is thus provided that the center axes tilted the fuel apertures at least in the circumferential direction are arranged.

The invention eliminates the one hand the disadvantages at a small number occur on fuel openings. These disadvantages of the prior art are in the circumferential direction of the Fuel nozzle uneven fuel distribution and to deep penetration of the fuel into the main flow. To the other is not the high number of fuel openings necessary which are very small and tend therefore to clogging. This corresponds to a technically feasible fuel supply with few fuel ports at the same time good homogeneity of the air-fuel mixing process.

The invention thus provides, by a few circumferentially salaried openings fuel from the outer boundary in introduce the airflow. The swirl of the fuel, of the DC and the counter-twist principle to twisted Air flow can be introduced, is ensured, that through relatively large openings of the fuel with a defined by the swirl penetration in the regions of penetrate air and cause a very homogeneous mixture can. Both the number of fuel holes is reduced, as well as the penetration depth is controlled, since the Regions of high air speed and thus high local Air mass flows in the near-wall region of the outer wall of the swirled airflow occur.

The central axes of the fuel ports may also additionally be inclined axially.

The advantage of the invention is a practice-oriented solution homogeneous premix problematic fuel with air and this with as few, relatively large fuel orifices a defined and not too deep penetration of Fuel to obtain the air flow. The overall objective is the reduction of the nitrogen oxide emissions of the gas turbine combustion chamber with a robust and technically implementable force fuel injection configuration.

In the following the invention with reference to embodiments described in connection with the drawing. In which:<dl tsize="6"><dt>Fig. 1</dt><dd>a partial schematic view including an enlarged Representation of a fuel nozzle according to the invention with distributed injection</dd><dt>FIG. 2</dt><dd>a part-sectional view through the device shown in Fig. 1 Assembly, the cutting direction has a conical Shape along the respective center axes of fuel apertures, and</dd><dt>Fig. 3</dt><dd>a sectional view, similar to FIG. 2, a modified Embodiment of the invention.</dd></dl>

In Fig. 1, a fuel nozzle according to the invention is shown, comprising a flow channel 1, which in a Individual air flow not shown via a swirler, the the airflow imposed a twist, is supplied. On centric cone serves to align the air flow and could additionally at least one further injection nozzle for have fuel. is over at least one fuel line 9 Fuel a fuel annular channel 8 performed. A Strömungswandung 2 (see enlarged view of Fig. 1) comprises a plurality of fuel holes 3, whose center axis 4 each placed against the air flow in the flow channel 1 is, so as can be seen in FIG. 1.

Figs. 2 and 3 show variants of the arrangement according to the invention the central axes 4 of the fuel orifices 3. These are inclined in the circumferential direction, so that it tangentially extend to a central circuit not shown. FIG. 2 shows an arrangement in which the fuel injection in co-rotating to a twist direction of 5 Air flow takes place, while FIG. 3 shows an embodiment shows, in which the central axes 4 of the fuel ports arranged in counter-twist to the twist direction of the air flow 5 are.

The invention is not limited to the embodiments shown limited, but the angle of inclination of the central axes 4 the fuel openings 3 in the present invention can be varied. The same applies for the number and the diameter of the fuel ports 3 and the associated fuel passages. in the Scope of the invention it is also possible, in the axial staggering multiple fuel injection inventive arrangements provide that also each other in the opposite direction of injection may be combined. Furthermore, the invention with different further embodiments of fuel injections combined.

LIST OF REFERENCE NUMBERS

<dl tsize="1" compact="compact"><dt>1</dt><dd>flow channel</dd><dt>2</dt><dd>flow wall</dd><dt>3</dt><dd>Fuel opening</dd><dt>4</dt><dd>Central axis of the fuel opening 3</dd><dt>5</dt><dd>Swirl direction of the air flow</dd><dt>6</dt><dd>swirler</dd><dt>7</dt><dd>cone</dd><dt>8th</dt><dd>Fuel annulus</dd><dt>9</dt><dd>Fuel line</dd></dl>