Fuel injection nozzle

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

In detail, the invention relates to a fuel injection nozzle for a gas turbine combustor with a film applicator, formed on which a plurality of fuel orifices are.

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

Fig. 1 shows in a schematic side sectional view of a Combustor 10 with associated fuel injection. shown is a central supply of the fuel in the Brenner axis 22 and a decentralized supply of fuel 23 almost perpendicular to the burner axis. The arrows 11 and 12 is a schematic way, the supply of air to a inner swirler 14 and outer swirler 15 shown. The fuel-air mixture 13 flowing in a known manner into the combustion chamber 10 a.

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. A Alternatively, the fuel in this atomizer apply, there is a so-called film layers, wherein Fuel is possible uniformly distributed in a film.

A further possibility of the fuel as intensively as possible to mix a large part of the air is in a decentralized injection (Fig. 2) from the outer edge of a flow channel formed by a film applicator 1, which the bulk of the air leads. This can range from an atomizer or else also from the outer contour of the nozzle. This injection is characterized in that, unlike than with a film applicator, the fuel a defined Penetration is experienced in the main air flow.

Both the fuel injection nozzle or with a central Pressure atomisers, as well as an application as a film on a Film applicator are to optimize such a way that if possible the entire the atomizer air flowing through homogeneously with fuel is mixed before combustion. Characterized by the emission specifically low-nitrogen oxide combustion is a lean with excess air premixed fuel preparation. The consequence are fuel nozzles, the large flow cross-sections have to pre-mix the high proportion of air with fuel to. Due to the size of the fuel nozzle and the limited capacity of the fuel jets and - sprays, deliverable at a central injection, the growing to penetrate air channels and thus a homogeneous distribution To achieve the fuel-air-mixture, are 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 often be switched at higher loads of the engine, 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 heated fuel remaining and decomposed.

The fuel nozzles are often by a radial direction very uneven velocity and mass flow distribution in. Due to the swirl of the air, which needed to stabilize the subsequent combustion is, are the local air mass flows in the radially outer boundary wall is greatest. If the fuel from introduced a few openings in the flow, on the one hand the homogeneity of the fuel in the air in the circumferential direction affected, but on the other hand, the fuel can very penetrate deep into the flow and thus unintentionally in mix and vaporize regions where insufficient Air is available. This can also at a decentralized Injection occur.

The invention is based on the object, a fuel injector to provide the above-mentioned type which, when simple construction and reliable operation of a uniform Mixing of fuel and air ensured.

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 the fuel openings through the film applicator with respect to their radial orientation is substantially parallel to the main flow direction the air are arranged. This substantially parallel arrangement may also include up to a range of the absolute Parallelism differ by an acute angle is marked. From a purely structural reasons, it is not Whenever possible, the fuel injection completely parallel perform. According to the invention is important that the fuel injection has a high axial component and the fuel is thus not injected radially.

The fuel orifices may at a radially inner wall the film applicator to be created, but they can also be a Trailing edge exit thereof.

The film applicator or the area of ​​the injection of the fuel is arranged preferably between two swirlers.

It is particularly advantageous when the fuel ports in addition are inclined in the swirl direction of the air, ie an additional have peripheral component. This may in corotating his or trained in counter-rotation. It is also inventively possible fuel openings row, one row mutually staggered alignment or another to arrange.

The film applicator can inventively also formed lamellar be an even better mixing of the air-fuel mixture to reach.

In the following the invention with reference to embodiments described in connection with the drawing. In which:<dl tsize="7"><dt>Fig. 1</dt><dd>a schematic representation of a longitudinal section through an inventive gas turbine combustor,</dd><dt>FIG. 2</dt><dd>a fuel nozzle with decentralized, inward Fuel injection according to the prior Technology with appropriate clarification of the details,</dd><dt>Fig. 3</dt><dd>a first embodiment of the invention a Fuel nozzle with distributed injection with flow-directed fuel injection, in an analogous Representation to Fig. 2,</dd><dt>Fig. 4</dt><dd>another embodiment of a fuel nozzle with distributed injection with fuel injection, at the trailing edge of a film applicator, also in a representation analogous to FIGS. 2 and 3,</dd><dt>Fig. 5</dt><dd>a cross-sectional end view in the direction of Arrows A, B and C of FIG. 2 to 4, illustrating the Fuel injection in the co-rotating to the air flow,</dd><dt>Fig. 6</dt><dd>an illustration analogous to FIG. 5 showing the Fuel injection in counter-twist to the air flow,</dd><dt>Fig. 7</dt><dd>a partial side view, similar to FIG. 4,</dd><dt>Fig. 8</dt><dd>the course of the axial velocity of the air over a local coordinate x that the axial distance indicating from the trailing edge of the fuel injector,</dd><dt>Fig. 9</dt><dd>an explanatory view similar to FIG. 7, for Explanation of Figs. 10 and 11,</dd><dt>Fig. 10</dt><dd>a view in the direction of the arrow D of FIG. 9 illustrating the outer and inner Luftverdrallung and the swirling of the fuel in the co-rotating,</dd><dt>Fig. 11</dt><dd>a representation, analogous to FIG. 10, in an injection the fuel in the counter-twist to the air flow,</dd><dt>Fig. 12</dt><dd>is an explanatory view showing the figures of FIG. 13 and 14,</dd><dt>Fig. 13</dt><dd>a view in the direction of arrow D in FIG. 12 showing a row of arrangement Fuel holes,</dd><dt>Fig. 14</dt><dd>an analog representation to FIG. 13 with a staggered Arrangement of the fuel holes,</dd><dt>Fig. 15</dt><dd>a further variant with a lamellar Execution of the film applicator surface.</dd></dl>

In the figures, like parts are each provided with the same reference numerals provided.

The FIG. 3 shows a simplified representation of a section by the inventive film applicator 1, wherein the fuel openings 2, in particular fuel holes 3, illustrated are, the center axes 5 α at an angle to the main flow direction 6 (near-wall flow direction in the inner swirl channel) are inclined.

Numeral 16 shows a wall element of hired Film applicator 1, the numeral 17 is an aerodynamically custom film applicator surface. is designated by the reference numeral 21 a fuel line shown.

The invention avoids the unwanted penetration of the liquid Fuel in areas with low flow rates and the related non-uniform fuel-air mixture. A proposed embodiment is shown in Fig. shown. 3 The fuel is here on a film applicator not radially inward, that is having a high radial component the exit speed of the fuel in an internal Swirl duct injected. Rather, in the proposed approach a high axial component of the exit speed of the fuel available and the fuel is approximately parallel to the main flow direction of the inner swirl channel brought in. In FIG. 3, schematically, the fuel ports and Ausdüsung fuel represented.

The fuel is initially through the openings shown a relative to the direction of air flow salaried Injected angle α, which is formed as an acute angle. In addition, the fuel ports may also circumferentially arranged in direct or counter-twist to the air flow be. By appointing the number of fuel orifices are reduced, at the same time is also the depth of penetration controlled since the regions of high air velocity and thus high local air mass flows in the near-wall region the outer wall of the swirled airflow occur. Of the liquid fuel passes after a short run length after the Ausdüsung on the surface of a wall element employed the film applicator, on a distribution or filming takes place of the fuel in the axial and circumferential direction (See FIG. 3). The high flow acceleration near the wall of the film applicator is the that forms Fuel film further downstream in the boundary layer near the following Contour of the film applicator maintained. Through an aerodynamically cheap ie low-loss design of the film applicator geometry in front of the outlet holes of the fuel, is thus already from the injection point of the fuel mixing with the twisted air instead. In addition, the Flow acceleration of the air utilized to penetration of non-vaporized fuel droplets in the direction of the burner axis to avoid. In contrast to the previously known Fuel nozzle with distributed injection (see Fig. 2) can according to the invention the formation of an undisturbed located ensured along the film applicator developing fuel film will. For structural reasons, the in FIG. designed 3 embodiment illustrated as divided construction be. The shape of the openings may also vary be carried out, ie, circular, elliptical, etc. The inventive Construction is the development of a fuel film in a radially very limited flow layer guaranteed. At the trailing edge of the film applicator pulls the Fuel film from and will be accelerated by the presence of and swirled air from the outer and inner Flow channel homogeneously mixed.

Another embodiment of the invention provides for the injection of fuel on the trailing edge of a flow divider between Two swirl cups before (Fig. 4). The maximum rate of accelerated in the swirl generators and twisted Air is located near the walls of the formed flow divider, ie in the outer flow of the boundary layer on both sides of the flow divider. In the wake of the flow divider finds a continuous acceleration of the air held at high Luftverdrallung. Fig. 7 and 8 show to the axial acceleration of the flow in the wake of the trailing edge of the flow divider, where x is the axial distance from the trailing edge the flow divider is. CFD studies have shown that with this embodiment, a very homogeneous Fuel-air mixture in the trailing area of ​​the flow splitter can be achieved, wherein the fuel is accelerated in axial Flow areas is introduced. In the Middle low temperatures can be very low nitrogen oxide emissions to accomplish. The main feature of this embodiment, is the avoidance of significant radial velocity components of the injected fuel, so that a penetration of individual drops classes in the vicinity of the burner axis, ie in areas with low flow rates, is always avoided. By the forming carried shear layer between the twisted airflows at high relative velocities between the fuel and Air a very intensive mixing. Different Eindüsungsvarianten are shown in Figs. 9 to 14. The injection the fuel can be used both in DC and countertwisting made at the inner and outer air swirl. also the arrangement of the fuel holes, both row and one row aligned and staggered to each other be arranged.

A further embodiment of the invention provides a lamellar Shaping before the film applicator. In Fig. 15 is to schematically illustrated a variant of the film applicator. On the basis the low-loss design of the exhaust mixer of a Aircraft engine is desired, different air mass flows loss as possible to bring together a total flow. The mixture is in the proposed torch concept However, an improved mixture formation by a dimensional mixing a swirled airflow with an already fuel partially premixed air flow to lead. The swirling air from the outer channel penetrates through the shaping periodically in the inner channel on. In an injection of the fuel in the inner and outer Swirl duct develops in increasing the residence time downstream of the film applicator, a fuel-air mixture. This Mixture can also by the shape of the inner Swirl duct penetrate. Within an appropriate "deflection" s to a maximum of ± 15% of the nominal center line of the rear edge the film applicator can thus produces a flow layer are, in a very intensive mixing of the fuel-air mixture from the inner channel and pure air admixture can from the outer swirl port or vice versa. In order to can be a very homogeneous mixture produce, the a uniform temperature field with low absolute temperatures enables and low nitrogen oxide values. Another feature the embodiment shown in Fig. 15 may also be a extensive custom spiral geometry of the laminar film applicator be, in which the slats geometry according effectively the air twist is adjusted close to the wall of the film applicator.

The advantage of the invention is a practice-oriented solution the problem, fuel pre-mix homogeneously 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 gas turbine combustor Stickoxidaustoßes with a robust and technically implementable fuel injection configuration.

LIST OF REFERENCE NUMBERS

<dl tsize="2" compact="compact"><dt>1</dt><dd>film applicator</dd><dt>2</dt><dd>Fuel opening</dd><dt>3</dt><dd>Fuel bore</dd><dt>4</dt><dd>Fuel direction</dd><dt>5</dt><dd>Central axis of the fuel ports</dd><dt>6</dt><dd>Wall near the main flow direction (inner swirl channel)</dd><dt>7</dt><dd>Wall near the main flow direction (outer swirl duct)</dd><dt>8th</dt><dd>Air twist (inner swirl channel)</dd><dt>9</dt><dd>Air twist (outer swirl duct)</dd><dt>10</dt><dd>combustor</dd><dt>11</dt><dd>Air supply (inner swirl channel)</dd><dt>12</dt><dd>Air supply (outer swirl duct)</dd><dt>13</dt><dd>Fuel / air mixture</dd><dt>14</dt><dd>Inner swirler </dd><dt>15</dt><dd>Outer swirler</dd><dt>16</dt><dd>wall element</dd><dt>17</dt><dd>Film applicator surface</dd><dt>18</dt><dd>Outside swirl duct (air)</dd><dt>19</dt><dd>Inner swirl duct (air)</dd><dt>20</dt><dd>Film applicator surface</dd><dt>21</dt><dd>Fuel line</dd><dt>22</dt><dd>Fuel supply (central)</dd><dt>23</dt><dd>Fuel supply (decentralized)</dd><dt>24</dt><dd>Slat-shaped film applicator</dd></dl>