Combined pressurised atomising nozzle

Technical field

The invention relates to a combined pressure atomizer nozzle for gas turbine burners operated with liquid fuel, according to the preamble of claim 1.

State of the art

A low-pollutant combustion of liquid fuels, such as extra light heating oil, requires the complete evaporation of the fuel drops and the premixing of the fuel vapor with the combustion air before reaching the flame front. Even small zones with a higher fuel concentration lead to higher temperatures in the reaction zone and thus to an increased formation of thermal nitrogen oxides. A disadvantage of lean premixed flames is that the flame temperatures are very close to the extinguishing limit. A targeted enrichment of the flame stabilization zones is necessary to ensure that burner operation remains stable at low loads and thus lower flame temperatures. There is therefore the problem of covering a wide operating range of the gas turbine with a burner and an atomizing nozzle.

The depth of penetration of the fuel spray into the combustion air, which is necessary for a good distribution of the fuel in the combustion air, is influenced above all by the ratio of the pulse flows of combustion air and fuel. This ratio changes with the operating conditions, ie as a result of changes in the fuel mass flow, in the fuel pressure and in the temperature and pressure of the burner air. The evaporation time of the fuel essentially depends on the atomization quality, the relative speed between fuel and air and the ambient conditions such as temperature and pressure. While the latter are predefined for the different load conditions by the gas turbine process, the atomization quality and the relative speed are mainly determined by the atomizer nozzle. In conventional gas turbine burners, return-controlled swirl atomizers or two-stage swirl atomizers are used to compensate for the changing environmental conditions. However, since no specific change in the direction of injection is possible with swirl nozzles, these known atomizer nozzles only allow a rough adaptation of the atomization quality and the fuel pulse to the respective load conditions.

An improvement can be achieved with the high pressure atomizing nozzle disclosed in EP-A2-0 711 953, the outlet openings of which are aligned with the zones of high air velocity and in which the angle of the fuel spray to the axis of the burner is at least as large as the cone half angle of the burner. As the name already expresses, high pressure is required to operate this pressure spray nozzle, which is particularly suitable for a double-cone burner known from EP-B1-0 321 809. For this purpose, the liquid fuel must be supplied at a pressure of more than 100 bar, which, however, requires a considerable effort in the design of the fuel system. In addition, it is also not possible to change the direction of injection or the jet profile.

DE-PS 862 599 discloses a combined two- or multi-stage swirl atomizer which, however, has an impulse behavior which is unsuitable for gas turbine burners. A very fine atomization is achieved with the resulting swirl spray, but the fuel impulse is too low to achieve a sufficient distribution of the fuel droplets in the combustion air and thus a good premixing.

Presentation of the invention

The invention tries to avoid these disadvantages . It is based on the task of creating a combined pressure atomizing nozzle for gas turbine burners with which an improved adaptation of the atomization quality of liquids to the respective load conditions, ie a good premixing over the entire load range, can be achieved.

According to the invention, this is achieved in that in a device according to the preamble of claim 1, the second feed channel has at least two outlet openings to the outside. As a result, the combined pressure atomizer nozzle is designed as a multi-hole orifice nozzle with a simple, central nozzle which, in addition to the fine atomization of the liquid fuel, also ensures a high fuel pulse. In this way, both rapid evaporation of the liquid fuel and good premixing of the fuel spray with the combustion air can be achieved, which is why the pressure atomizer nozzle according to the invention is particularly suitable for gas turbine burners. In addition, a relatively simply constructed pressure atomizer nozzle with a small space requirement is created, the two-stage of which is realized only by the additional introduction of the outlet openings of the second feed channel.

Compared to the injection of liquid fuel via an annular channel (DE-PS 862 599) known from the prior art, the outlet openings according to the invention produce several separate fuel sprays with a relatively narrow spray cone. However, these fuel sprays have a significantly higher momentum than an annular fuel spray and also have a higher relative speed of the liquid fuel to the combustion air. Therefore, an improved premixing can be achieved with this solution. In the case of a fuel distribution between the orifice nozzle and the central nozzle that corresponds to the specific operating situation, the pressure atomizer nozzle enables both targeted mixing of the liquid fuel into the combustion air and adaptation of the fuel pulse to the required penetration depth of the liquid fuel into the combustion air. Via the central nozzle, ie through the first feed channel, the pressure atomizing nozzle is supplied with such a mass flow of liquid fuel which corresponds to the required amount of fuel of the gas turbine at partial load.

It is particularly advantageous if the outlet openings of the second feed channel are arranged uniformly distributed on the circumference of the nozzle body. This arrangement ensures a uniform fuel concentration in the reaction zone and therefore prevents the increased formation of nitrogen oxides.

The first feed channel is formed inside a first tube and the second feed channel inside a second tube. Both pipes are arranged concentrically to each other and are closed downstream from a cover to the outside. The cover and the first tube are made in one piece. As a result, the pressure atomizing nozzle can be assembled relatively easily by pushing the second tube onto the first tube until it stops on the cover. The second tube and the cover are then firmly connected to one another, for example by welding.

A turbulence chamber is advantageously formed immediately upstream of the outlet openings of the second feed channel. The atomization of the liquid fuel can be improved by the additional inclusion of the turbulence chamber in the multi-hole orifice nozzle. The turbulence chamber is separated from the second feed channel by an intermediate wall. At least two turbulence generator openings are arranged in the intermediate wall off-center of the second feed channel. With such an asymmetrical introduction of the liquid fuel into the turbulence chamber, a higher turbulence can be achieved and the atomization of the liquid fuel can thereby be further improved.

The turbulence generator openings are particularly advantageously arranged offset to the outlet openings of the second feed channel. The displacement for each four turbulence generator openings or outlet openings is preferably approximately 45 °, so that the turbulence generator openings are arranged exactly in the middle between the outlet openings. This leads to a more intensive, small-scale and turbulent structure, ie to a very fine fuel spray.

The pressure atomizing nozzle designed with the additional turbulence chamber can also be installed relatively easily. For this purpose, the cover, the first tube and the intermediate wall are formed in one piece, so that these components can be inserted together, to some extent as an insert, into the second tube. Finally, the first tube and the cover are firmly connected to one another, for example by welding.

As an alternative to a simple, central nozzle, either a swirl chamber or a turbulence chamber is formed between the first feed channel and the outlet opening. In the first case, ie when using a swirl nozzle, a swirl spray is generated with a relatively wide spray cone, so that a high fuel concentration in the center of the burner and sufficient evaporation of the fuel can be achieved even at partial load. This enables stable burner operation even in the partial load range of the gas turbine. If, on the other hand, a turbulence nozzle is used as the central nozzle, a narrower spray angle can be achieved while the atomization of the liquid fuel remains constant. In this way, the fuel concentration in the center of the burner can be increased further, thereby additionally stabilizing the burner operation at part load.

Brief description of the drawing

In the drawing, several exemplary embodiments of the invention are shown using a combined pressure atomizing nozzle for gas turbine burners.

Show it:<dl id="dl0001" compact="compact"><dt>Fig. 1</dt><dd>a partial longitudinal section of the atomizer nozzle, including the representation of the fuel spray at full load;</dd><dt>Fig. 2</dt><dd>a cross section through the pressure atomizing nozzle of Figure 1, along the line II-II.</dd><dt>Fig. 3</dt><dd>a cross section through the pressure atomizing nozzle of Figure 1, along the line III-III.</dd><dt>Fig. 4</dt><dd>a representation according to Figure 1, but with a representation of the fuel spray at part-load operation.</dd><dt>Fig. 5</dt><dd>a schematic representation of the liquid supply system to the pressure atomizing nozzle, wherein liquid fuel (fuel oil) is atomized in each case;</dd><dt>Fig. 6</dt><dd>a schematic representation of the liquid supply system to the pressure atomizing nozzle, wherein different liquids (fuel oil, water) are atomized;</dd><dt>Fig. 7</dt><dd>a partial longitudinal section of a pressure atomizing nozzle, with a turbulence chamber in the outer feed channel;</dd><dt>Fig. 8</dt><dd>a cross section through the pressure atomizing nozzle of Figure 7, along the line VIII-VIII.</dd><dt>Fig. 9</dt><dd>a cross section through the pressure atomizing nozzle of Figure 7, along the line IX-IX.</dd><dt>Fig. 10</dt><dd>a partial longitudinal section of a pressure atomizer nozzle, with radial outlet openings of the outer feed channel;</dd><dt>Fig. 11</dt><dd>a cross section through the pressure atomizing nozzle of Figure 10, along the line XX.</dd><dt>Fig. 12</dt><dd>a partial longitudinal section of a pressure atomizing nozzle, according to a next embodiment, in partial load operation;</dd><dt>Fig. 13</dt><dd>a partial longitudinal section of a pressure atomizing nozzle, according to a further embodiment;</dd><dt>Fig. 14</dt><dd>a partial longitudinal section of a pressure atomizing nozzle, according to a further embodiment, at part-load operation.</dd></dl>

Only the elements essential for understanding the invention are shown. For example, the gas turbine burner receiving the pressure atomizing nozzle is not shown. The direction of flow of the work equipment is indicated by arrows.

Way of carrying out the invention

The gas turbine burner, not shown, which receives the pressure atomizing nozzle is designed, for example, as a double-cone burner, as is known from EP-B1-0 321 809. Of course, the pressure atomizing nozzle is in principle also suitable for other gas turbine burners, for example for the burner known from EP-A2-0 704 657 and consisting of a swirl generator with a subsequent mixing section. The pressure atomizing nozzle has a nozzle body 1 with two tubes 2, 3 arranged concentrically to one another, which are closed downstream from a conical cover 4 to an outer space 5. The outside space 5 of the pressure atomizing nozzle is also the inside of the gas turbine burner. The nozzle body 1 has a longitudinal axis 6 which coincides with the longitudinal axis (not shown) of the gas turbine burner.

The first, inner tube 2 encloses a first, inner feed channel 7, to which a swirl chamber 8 connects downstream. The swirl chamber 8 is bounded on the outside by the inner tube 2, downstream of the cover 4 and upstream by an insert 9 (FIG. 1). It is connected to the inner feed channel 7 via tangentially arranged swirl channels 10 (FIG. 2) arranged in the insert 9 and to the outer space 5 via an outlet opening 11. The outlet opening 11 is arranged in the longitudinal axis 6 of the nozzle body 1. The second, outer tube 3 has a larger diameter than the inner tube 2, so that a second, outer and designed as an annular feed channel 12 is arranged between the two tubes 3, 2. The latter is also connected to the outside space 5 via four outlet openings 13 located in the cover 4. The outlet openings 13 are evenly distributed over the circumference of the nozzle body 1 (FIG. 3) and aligned so that they spray into the wake of the swirl generator of the burner, not shown. The exact alignment depends on the boundary conditions of the gas turbine. It should be noted that the number of outlet openings 13 is not fixed at four, but at least two outlet openings 13 must be provided for an even fuel distribution. A pressure atomizer nozzle designed in this way is particularly suitable for swirl generators with a conical shape.

The cover 4 and the inner tube 2 of the nozzle body 1 are formed in one piece. As a result, the entire pressure atomizing nozzle can be assembled relatively simply by pushing the outer tube 3 onto the inner tube 2 until it stops on the cover 4. The outer tube 3 and the cover 4 are then welded together.

When the gas turbine burner is operating, a liquid fuel, for example fuel oil, is supplied to the pressure atomizing nozzle as the liquid 14 to be atomized. Depending on the specific operating situation of the gas turbine, ie depending on whether it is operated at full or partial load, the liquid fuel 14 is supplied to the gas turbine burner either via the outer feed channel 12 or via the inner feed channel 7 of the pressure atomizer nozzle. The nozzle body 1 thus has two different nozzles, namely an outer multi-hole orifice nozzle and a central swirl nozzle.

At partial load, the liquid fuel 14 is introduced into the inner feed channel 7 of the nozzle body 1, from where it reaches the swirl chamber 8 in a swirled manner via the swirl channels 10. The liquid fuel 14 is then injected into the outer space 5 via the outlet opening 11, the swirl nozzle producing a swirl spray 15 with a relatively wide spray cone 16 (FIG. 4). This means that a high fuel concentration in the center of the burner and sufficient evaporation of the fuel is achieved even at partial load. This enables stable burner operation even in the partial load range of the gas turbine.

In the exemplary embodiment shown, the liquid fuel 14 is fed centrally via the inner feed channel 7, which is arranged in the center and is completely surrounded by the outer feed channel 12. Of course, the inner feed channel 7 can also be arranged off-center and / or only partially surrounded by the outer feed channel 12, so that the liquid fuel 14 reaches the swirl nozzle in a decentralized manner, but with the same effect (not shown).

In order to achieve good atomization quality and a high jet penetration depth into the combustion air, the injection pressure should be up to 100 bar. The maximum mass flow of the liquid fuel 14 is selected depending on the load range of the gas turbine to be covered and is usually less than 50% of the mass flow at full load. Thus, the gas turbine burner can work in the premix mode even at part load of the gas turbine.

In contrast, the liquid fuel 14 is introduced at full load into the outer feed channel 12 of the nozzle body 1 and reaches the outer space 5 via its outlet openings 13. In this way, the multi-hole orifice nozzle generates several fuel sprays 17, each corresponding to the number of outlet openings 13, with a relatively narrow one Spray cone 18 (Fig. 1). The separate fuel sprays 17 have a high momentum and also have a high relative speed of the liquid fuel 14 to the combustion air. The multi-hole orifice nozzle therefore atomizes the liquid fuel 14 well. In addition, the liquid fuel 14 reaches a high depth of penetration into the combustion air, which leads to a significantly improved mixing quality. In spite of the now improved penetration depth of the liquid fuel 14 in full load operation, there are no problems due to wall application of fuel oil droplets at part load, because then a switch is made to the central swirl nozzle.

Because of this variable mode of operation due to a corresponding liquid supply system, the pressure atomizing nozzle according to the invention can meet the requirements for the fuel spray 15, 17 which differ greatly depending on the specific operating situation. 5 schematically shows a possible liquid supply system to the pressure atomizing nozzle. The liquid fuel 14 to be atomized is pumped from a fuel line 20 into a pressure container 21 via a pump 19. A return valve 22 is used to set the pump admission pressure. A shut-off valve 23 is arranged in the fuel line 20 between the pump 19 and the pressure vessel 21. Two lines 24, 25 extend from the pressure vessel 21, the line 24 feeding the second feed channel 12, ie the multi-hole orifice nozzle, and the line 25 communicating with the first feed channel 7, ie with the swirl nozzle. A control valve 26, 27 is arranged in each of the lines 24, 25, which allows the respective amount of liquid supplied to be regulated. Depending on requirements, both control valves 26, 27 can also be opened, so that in this case both nozzles are in operation. Smooth switching is possible between the two nozzles. As in Fig. 5 is indicated, several burners, for example a gas turbine combustion chamber, can be supplied with liquid fuel 14 via this fuel supply system. The circuit shown has the advantage that only the two control valves 26, 27, ie only one control valve 26 or 27 per nozzle, are required to regulate the pressure atomizing nozzle consisting of two separate nozzles. Of course, a water-oil emulsion can also be used as fuel in special cases, which enables a further reduction in NOx emissions.

An alternative fluid delivery system is shown in FIG. The pressure atomizing nozzle is fed via a first feed line 28 with water, as a first liquid 29 to be atomized, and via a second feed line 30 with liquid fuel (fuel oil), as a second liquid 31 to be atomized. A pump 19 'is arranged in the feed lines 28, 30 and a shut-off valve 23' is arranged downstream, with which the lines 28, 30 can optionally be closed. The mass flow of the liquids 29, 31 to be atomized is regulated by means of a control valve 26 ', 27' arranged in each of the supply lines 28, 30. As shown in Fig. 6 indicated that several burners, for example a gas turbine combustion chamber, are supplied with liquid fuel 31 or with water 29 via this liquid supply system, the pressure atomizing nozzle can be operated at the start or at partial load by only atomizing fuel oil 31 via the multi-hole orifice nozzle. At higher loads or at full load, the gas turbine burner is then supplied with water 29 via the feed line 28. When the interior of the gas turbine burner, which is not shown, is injected, the droplets of the water 29 are mixed with those of the fuel oil 31, which leads to a reduction in NOx emissions. Here, too, there is the advantage that only one control valve 26 ′, 27 ′ per nozzle of the pressure atomizer nozzle and only one supply line 30 for the liquid fuel 31 are required for gas turbine operation.

The gas turbine burners equipped with the pressure atomizer nozzle designed according to the invention can be operated with several different liquid fuels 31 as well as with a liquid fuel 31 and with water 29, with only one liquid fuel 31 or also with liquid fuel / water mixtures. They therefore allow a relatively wide range of applications and can be adapted to changing operating conditions. The central swirl nozzle is continuously flowed around by the liquid 14, 31 passed through the latter during operation of the multi-hole orifice nozzle. Therefore, when switching from full to partial load, as is the case, for example, with a load loss, no cooling of the swirl nozzle is necessary, so that a quick load change can be guaranteed.

In a next exemplary embodiment, a turbulence chamber 32 is formed directly upstream of the outlet openings 13 of the outer feed channel 12. The turbulence chamber 32 is separated from the outer feed channel 12 by an intermediate wall 33. Four turbulence generator openings 34 are formed in the intermediate wall 33 off-center of the outer feed channel 12 (FIG. 7). When using a pressure atomizer nozzle with the additional turbulence chamber 32 of the outer feed channel 12, the liquid fuel 14 is injected via the outlet openings 13 as a highly turbulent outlet jet into the interior of the gas turbine burner, where it then breaks down into a fine fuel spray 17. The premixing of the gas turbine burner can thus be further improved.

As can easily be seen in a comparison of FIGS. 8 and 9, the turbulence generator openings 34, relative to the main flow direction of the liquid fuel 14, are arranged at an angle of 45 ° to the outlet openings 13 of the outer feed channel 12. As a result, one of the turbulence generator openings 34 is arranged centrally between two mutually adjacent outlet openings 13. With this measure, the turbulent structure of the liquid fuel 14 becomes on the one hand more intense and on the other hand small-scale. Therefore, a turbulent, rapidly disintegrating free jet emerges from the multi-hole orifice nozzle. Of course, a number other than four outlet openings 13 or turbulence generator openings 34 can also be realized, in which case the angle described changes accordingly.

The cover 4, the inner tube 2 and the intermediate wall 33 of the nozzle body 1 are formed in one piece (FIG. 7). As a result, this pressure atomizing nozzle can also be assembled relatively simply by pushing the outer tube 3 onto the inner tube 2 until it stops on the cover 4. The outer tube 3 is then welded to both the cover 4 and the intermediate wall 33.

According to a further exemplary embodiment, the outlet openings 13 of the outer feed channel 12 have a radial outlet direction 35 (FIG. 10, FIG. 11), which is particularly suitable for axial swirl generators. Particularly when the pressure atomizer nozzle has an axially parallel flow, this leads to a very high penetration depth of the fuel spray 17 into the combustion air and thus to an additional improvement in the premixing of the gas turbine burner.

As an alternative to the formation of the swirl channels 10, turbulence channels 36 are arranged in the insert 9 in accordance with a next exemplary embodiment. These open into a turbulence chamber 37, which in turn is connected to the outside space 5 via the outlet opening 11 (FIG. 12). During part-load operation of this pressure atomizer nozzle, which consists of a multi-hole orifice nozzle and a central turbulence nozzle, a rapidly disintegrating fuel spray 38 is generated with a particularly narrow spray cone 39. As a result, the fuel concentration in the center of the burner can be increased even at partial load of the gas turbine.

Of course, the pressure atomizing nozzle can also be designed without an insert 9, so that the first feed channel 7 extends directly to the cover 4 (FIG. 13). In this case, a particularly simple, central nozzle with a small space requirement and a function essentially analogous to that of the central nozzles of the exemplary embodiments described above is produced.

In a further embodiment, likewise without insert 9, a third tube 40 is arranged inside the first tube 2 and concentrically to it, which ends upstream of the outlet opening 11 and receives the inner feed channel 7. The first and third tubes 2, 40 are spaced apart from one another, so that a free space 41 designed as an air duct is formed between them. The air duct 41 widens downstream of the third pipe 40 to a mixing space 42 into which the feed duct 7 opens (FIG. 14). When this central nozzle is in operation, air 43 is supplied via a supply line (not shown) and via the air duct 41. In the mixing space 42, the air 43 hits the liquid fuel 14, which leads to its air-assisted injection into the outer space 5 of the pressure atomizer nozzle, ie into the interior of the gas turbine burner. The required atomization quality is thus achieved regardless of the current fuel throughput, which is particularly advantageous in the case of part-load operation.

Reference list

1 nozzle body 2 first tube 3 second pipe 4 lids 5 outside space 6 longitudinal axis, from 1 7 first, inner feed channel 8 swirl chamber 9 use 10 swirl channel 11 outlet opening, from 7 12 second, outer feed channel, annular space 13 outlet opening, from 12 14 liquid, liquid fuel (fuel oil) 15 swirl spray, fuel spray 16 spray cones, from 15 17 fuel spray 18 spray cones, from 17 19 pump 20 fuel line 21 pressure vessels 22 return valve 23 shut-off valve 24 line 25 line 26 control valve 27 control valve 28 supply line 29 liquid, water 30 supply line 31 liquid, liquid fuel (fuel oil) 32 turbulence chamber 33 partition 34 Turbulence generator opening 35 Exit direction, radial 36 turbulence channel 37 turbulence chamber 38 fuel spray 39 spray cones 40 pipe 41 Free space, air duct 42 mixing room 43 air 19 'pump 23<img file="EP0902233A1_D0001.tif" />  Shut-off valve 26 'control valve 27 'control valve