GB2347205A

GB2347205A - Atomizing device

Info

Publication number: GB2347205A
Application number: GB9930543A
Authority: GB
Inventors: Joachim Nikolaus Butz
Original assignee: ABB Alstom Power Switzerland Ltd; Alstom Power Inc
Current assignee: General Electric Switzerland GmbH; Alstom Power Inc
Priority date: 1998-12-30
Filing date: 1999-12-23
Publication date: 2000-08-30
Anticipated expiration: 2019-12-23
Also published as: GB2347205B; DE19860785A1; GB9930543D0

Abstract

An atomizing device (10) for the atomization of a liquid comprises a central atomizing nozzle (32), which is arranged in an axis (11) at the tube end (16) of a coaxial inner tube (12) and atomizes the liquid, fed through an inner passage (14) in the inner tube (12), in the direction of the axis (11) into a spray cone (33) having a first spray angle (W1), and also fluidic means (13, 15, 18) which are arranged concentrically around the atomizing nozzle (32) and enable a second spray angle (W2) differing from the first to be set. In such a device, a simple and flexible setting of the spray angle is achieved owing to the fact that the fluidic means comprise an outer tube (13), which concentrically encloses the inner tube (12) and forms an annular outer passage (15) between the inner tube (12) and the outer tube (13), the annular outer passage (15) opening in the region of the atomizing nozzle (32) into the exterior space or combustion space in such a way that liquid fed in the outer passage (15) and discharging under pressure from the outer passage (15) interacts with the spray cone (33) from the atomizing nozzle (32) and brings about a change in the spray angle.

Description

1 2347205

DESCRIPTION

ATOMIZING DEVICE TECHNICAL FIELD

The present invention relates to the field of atomization technology. It concerns an atomizing device for the atomization of a liquid, in particular of a liquid fuel into the combustion space of a gas turbine, the atomizing device comprising a central atomizing nozzle, which is arranged in an axis at the tube end of a coaxial inner tube and atomizes the liquid, fed through an inner passage in the inner tube, in the direction of the. axis into a spray cone having a first spray angle, and the atomizing device also comprising fluidic means which are arranged concentrically around the atomizing nozzle and enable a second spray angle differing from the first to be set.

Such an atomizing device for the atomization of liquid fuel in a rotary tubular kiln has been disclosed, for example, by publication US-A-4,976,607 (see Figures 5 and 12 there and the associated parts of the description).

PRIOR ART

During the atomization of liquids by nozzles - as used,, for example, in burners for kilns or gas turbines - a certain spray angle and/or degree of atomization, is obtained as a function of various parameters. In this case, the spray angle, i.e. the opening angle of the spray cone produced, depends not only on the diameter and the shape of the nozzle necessary for the atomization but also on the pressure difference at the nozzle. However, the properties of the liquid to be atomized, such as, for example, the viscosity and the density, are also important.

This results in a problem for the practical operation of an atomizing device: if, in an atomizing device, a changeover is made from a liquid having certain properties to another liquid having other properties (e.g to another oil type in the case of an oil burner), another spray angle at a constant mass flow - is obtained as a rule. if the spray angle is to remain the same upon changeover to the other liquid, this may be' effected by a corresponding change of the nozzle parameters. To this end, either a (complicated) mechanical adjusting mechanism ought to be provided at the nozzle, or the nozzle as such ought to be completely exchanged for another nozzle having appropriately adapted nozzle parameters. However, such a change in the nozzle parameters is very laborious. Although a mechanical adjusting mechanism is relatively flexible, it is susceptible to faults. On the other hand, the exchange of the nozzle is less susceptible to faults, but is instead also not very flexible.

DESCRIPTION OF THE INVENTION

The object of the invention is therefore to provide an atomizing device in which, at little cost and in a relatively simple and reliable manner, the spray angle can be varied continuously or the same spray angle can be set for different liquids.

The object is achieved by all the features of claim 1. The essence of the invention consists in varying the spray angle in a fluid-mechanical manner by interaction of the spray cone from the central atomizing nozzle with a concentrically surrounding envelope flow of the liquid. Thus the solution clearly differs from other solutions as disclosed in US-A4,967,607 mentioned at the beginning or in US-A3,752,405 and in which a variable flame geometry is produced by a simple superimposition without interaction of a plurality of spray cones having a different spray angle. In particular, these known solutions are not suitable or Intended for leaving the spray angle unchanged during a change of the liquid to be atomized, as is desirable during the operation of gas turbines, but are intended for rotary tubular kilns in the cement industry, in which the flame geometry in particular is to be varied in a suitable manner in order to compensate for differences in the filling.

A first preferred embodiment of the invention is characterized in that control means which enable the liquid mass' flow flowing through the outer passage to be controlled are provided, and in that the liquid for the outer passage is fed by means of a pump via a first control valve- By the pump with the following valve, the requisite pressure can be produced and the desired mass flow for influencing the spray angle can be set.

If the liquid mass flow is to remain unchanged overall when the spray angle is varied, it is especially simple and advantageous if, in a second preferred embodiment of the invention, control means which enable a constant liquid mass flow to be alloted to the inner passage and the outer passage in an adjustable manner are provided, if both the liquid for the outer passage and the liquid for the inner passage are fed by means of the same pump, if the liquid delivered by the pump reaches the passages via separate distribution lines, and if a control valve is arranged in each of the distribution lines and is controlled as a.function of the other respective control valve.

The interaction between the central spray cone and the surrounding envelope flow depends to a considerable extent on the geometry of the arrangement in the discharge region of the liquids. In this case, it is possible for the inner tube and the outer tube to end at the same level, f or the tube end of the inner tube to be set back relative to the tube end of the outer tube or for the tube end of the outer tube to be set back relative to the tube end of the inner tube. In particular in the last-mentioned case, the envelope flow can fully form after the discharge from the outer passage before it interacts with the central spray cone.

The forming of the envelope flow is assisted if at the same time a stepped recess is provided at the tube end of the outer. tube in order to bring about a controlled flow separation at the inner wall of the outer tube. However, it is also conceivable for the envelope flow to be directed inward into the central 5 spray cone by the outer tube having a conical constriction at its tube end. However, the interaction may also be increased by turbulence elements for swirling the discharging liquid being provided inside the outer passage in the region of the orifice.

According to the invention, the atomizing device according to the invention is used for the atomization of liquid fuel into the combustion chamber of a gas turbine. In this case, due to the concentric construction, it is especially favorable if the atomizing device is part of a fuel lance.

BRIEF DESCRIPTION OF THE FIGURES

The invention is to be explained below in 20 more detail with reference to exemplary embodiments in connection with the drawing, in which: Fig. 1 shows a longitudinal section of a preferred exemplary embodiment of the atomizing device according to the invention at the front end 25 of a fuel lance and the associated schematic fuel supply; Fig- 2 shows the cross section through the fuel lance in the plane II-II of Fig. 1; Fig. 3 shows a second exemplary embodiment of the atomizing device according to the invention with tubes ending in the same plane and a conical constriction of the outer tube in the orifice region; Fig. 4 shows a third embodiment of the atomizing device according to the invention with a setback outer tube, which has an inner recess; Fig. 5 shows a fourth exemplary embodiment of the atomizing device according to the invention with tubes ending in the same plane and recesses on both sides in the orifice region of the outer passage; and Fig. 6 shows a fifth exemplary embodiment of the atomizing device according to the invention with a set-back inner tube and additional t9rbulence elements in the orifice region of the outer passage.

WAYS OF IMPLEMENTING THE INVENTION A preferred exemplary embodiment of the atomizing device according to the invention at the front end of a fuel lance and the associated schematic fuel supply are reproduced in longitudinal section in Fig. 1. Such a fuel lance is used, for example, in the so-called double-cone burners of the applicant, as disclosed by US-A-5, 489,203. The atomizing device 10 comprises, concentric to an axis 11, an inner tube 12 and an outer tube 13 which concentrically encloses the inner tube, the inner tube 12 and outer tube 13 narrowing in diameter toward the end. The interior of the inner tube 12 forms an inner passage, through which the liquid to be atomized (in this case the liquid fuel) is directed in a primary liquid flow to the atomizing nozzle 32 located at the orifice or the tube end 16 of the inner tube 12. In the present example, the atomizing nozzle 32 is a circular central opening. The liquid under high pressure is atomized by pressure atomization- during the discharge from the atomizing nozzle 32 and forms a spray cone 33 of fine liquid droplets, which has a first opening or spray angle Wl and is indicated in Fig. I by solid lines.

Formed between the inner tube 12 and the outer tube 13 is an annular outer passage 15, via which the same liquid is directed in a secondary liquid flow parallel to the inner passage 14 to the orifice or the tube end 18 of the outer tube 13. The liquid from the outer passage 15, which liquid is likewise under pressure, discharges there in an atomized manner in the form of an envelope flow, which interacts with the spray cone 33 from the central atomizing nozzle 32. Depending on the preselection of the velocity and/or pressure ratio or of the velocity and/or pressure differences between the primary flow and the secondary flow, this interaction produces a variable change in the spray 6ngle, which can then be varied as second spray angle W2 (indicated in Fig. I by broken lines) within a larger angular range about the first spray angle Wl- For the conventional pressure atomization, a liquid pump and a control valve are normally provided. For the atomizing device according to Fig. 1, a pump 26 which forces the liquid drawn in from a feed line 27 into the inner passage 14 and the outer passage 15 via two distribution lines 21 and 22 likewise preferably suffices. Arranged in each of the distribution lines is a control valve 24 and respectively a control valve 25, which are preferably actuated as a function of one another by a control device 23 in such a way that the total mass flow remains constant in the event of a variation in the mass flows in the individual distribution lines 21, 22. In this way, the spray angle W2 can be adjusted by simultaneous adjustment of the control valves 24, 25 without the total mass flow (and thus the output at the burner) being changed. Figure 2 shows a section through the atomizing device along line II-II in Figure 1.

The interaction of the envelope flow from the outer passage 15 with the spray cone 33 from the central atomizing opening also depends to a considerable extent on the geometric relationships in the orifice region or at the tube ends 16, 18.

Different variants of the orifice geometry are reproduced in Figs. 3 to 6. In Fig. 3, the tube ends 16 and 16 of the two tubes 12 and 13 lie in the same plane. The flow separation at the inner wall of the inner tube 12 is facilitated by a stepped recess 17 in the inner tube 12. The inner tube 12 is tapered slightly conically on the outside at the tube end 16.

The outer tube 13. has a corresponding conical constriction 28, so that the envelope flow from the outer passage 15 is directed conically inward and thus interacts with the spray cone in an intensified manner.

In Fig. 4, the tube end 18 of the outer tube 13 is set back rearward relative to the tube end 16 of the inner tube 12. As a result, an envelope flow can form in an undisturbed manner before it interacts with the central spray cone. The forming of the envelope flow is facilitated by a controlled flow separation at the inner wall of the outer tube 13 by means of the stepped recess 29 on the inside.

In the exemplary embodiment in Fig. 5, the tube ends 1 6, 18 again lie in the same plane. In this case, the controlled flow separation and thus the forming of defined flows is ensured by the various stepped recesses 17, 29 and 30.

Finally, in Fig. 6, the tube end 16 of the inner tube 12 is set back rearward relative to the tube end 18 of the outer tube 13. Here, too, a controlled flow separation at both passages 14, 15 is achieved by corresponding stepped recesses. In addition, turbulence elements 31, which improve the atomizing action and the interaction between the envelope flow and the spray cone, are arranged in the outer passage 15 in the region of the orifice.

Although the invention has been explained using the example of a fuel lance for the burner of a gas turbine and can also preferably be used in this field, the proposed type of atomization with spray angles which can be set in a steady fluid-mechanical manner is not restricted to the field of burners, but may also be advantageously used in other fields of liquid atomization (e.g. spray drying, painting, etc.).

LIST OF DESIGNATIONS Atomizing device 11 Axis 12 Inner tube 13 OUter tube 14 Inner passage Outer passage 16 Tube end (inner tube) 17 Recess (stepped) 18 Tube end (outer tube) 21, 22 Distribution line 23 Control device 24, 25 Control valve 26 Fump 27 Feed line 28 Constriction (conical) 29, 30 Recess (stepped) 31 Turbulence element 32 Atomizing nozzle 33 Spray cone W1, W2 Spray angle

Claims

PATENT CLAIMS

I. An atomizing device (10) for the atomization of a liquid, in. particular of a liquid fuel into the combustion; space of a gas turbine, the atomizing device (10) compriting a central atomizing nozzle (32), which is arranged in an axis (11) at the tube end (16) of a coaxial inner tube (12) and atomizes the liquid, fed through an inner passage (14) in the inner tube (12), in the direction of the axis (11) into a spray cone (33) having a first spray angle (Wl), and the atomizing device (10) also comprising fluidic means (13, 15, 18, 28, 29) which are arranged concentrically around the atomizing nozzle (32) and enable a second spray angle (W2) differing from the first to be set, characterized in that the fluidic means comprise an outer tube (13), which concentrically encloses the inner tube (12) and forms an annular outer passage (15) between the inner tube (12) and the outer tube (13), the annular outer passage (15) opening in the region of the atomizing nozzle (32) into the exterior space or combustion space in such a way that liquid fed in the outer passage (15) and discharging under pressure from the outer passage (15) interacts with the spray cone (33) from the atomizing nozzle (32) and brings about a change in the spray angle:.
2. The atomizing device as claimed in claim 1, characterized in that control means (24, 26) which enable the liquid mass flow flowing through the outer passage (15) to be controlled are provided.
3. The atomizing device as claimed in claim 2, characterized in that the liquid for the outer passage (15) is fed by means of a pump (26) via a first control valve (24).-
4. The atomizing device as claimed in claim 1, characterized in that control means (23-26) which enable a constant liquid mass flow to be alloted to the inner passage (14) and the outer passage (15) in an adjustable manner are provided.
5. The atomizing device as claimed in claim 4, characterized in that both the liquid for the outer passage (15) and the liquid for the inner passage (14) are fed by means of the same pump (26), in that the 5 liquid delivered by the pump (26) reaches the passages (14, 15) vic't separate distribution lines (21, 22), and in that a control valve (24 or 25 resp.) is arranged in each of the distribution lines (21, 22) and is controlled as a function of the other respective control valve.
6. The atomizing device as claimed in one of claims I to 5, characterized in that the inner tube (12) and the outer tube (13) end at the same level.
7. The atlomizing device as claimed in one of claims 1 15 to 5, characterized in that the tube end (16) of the inner tube (12) is set back relative to the tube end (18) of the outer tube (13).
8. The atomizing device as claimed in one of claims I to 5, characterized in that the tube end (18) of the outer tube (13) is set back relative to the tube end (16) of the inner tube (12).
9. The atomizing device as claimed in one of claims 1 to 8, characterized in that a stepped recess (29) is provided at the tube end (18) of the outer tube (13) in order to bring about a controlled flow separation at the inner wall of the outer tube (13).
10. The atomizing device as claimed in claim 6, characterized in that the outer tube (13) has a conical constriction (28) at its tube end (18).
11. The atomizing device as claimed in one of claims 1 to 10, characterized in that turbulence elements (31) for swirling the discharging liquid are provided inside the outer passage (15) in the region of the orifice.
12. The use of the atomizing device as claimed in one 35 of claims I to 11 for the atomization of liquid fuel into the combustion chamber of a gas turbine.
13. The use as claimed in claim 12, characterized in that the atomizing device (10) is part of a fuel lance.
14. An atomizing device substantially as herein described with reference to Figures I and 2; Figure 3; Figure 4; Figure 5 or Figure 6 of the accompanying drawings.