EP0651162A1 - Compressor - Google Patents

Abstract

A compressor (1) comprises a rotor shaft (10) which is rotatable about a compressor axis (18) and is equipped with a multiplicity of moving blades (7) fastened to its periphery, a compressor casing (2) surrounding the rotor shaft (10) in the area of the moving blades (7), an inlet casing (9) enclosing the rotor shaft (10) on the inlet side of the compressor (1) and having an outer shell (3) and an inner shell (16), between which an inlet space (4) for the air to be compressed is formed, which inlet space (4) is connected on the one side to the ambient via an air inlet (5) provided with an inlet filter (6) and merges on the other side into a suction duct (27) equipped with adjustable inlet guide blades (8), the outer shell (3) adjoining the compressor casing (2), and a seal casing (11) at the end of the inner shell (16) facing the moving blades (7), which seal casing (11), bearing against the periphery of the rotor shaft (10), seals off the suction duct (27) from the ambient and contains a sealing-air chamber (12) from which sealing air can discharge into the annular gap (28) between seal casing (11) and rotor shaft (10). Such a compressor is improved in its operational reliability by the sealing chamber (12) being connected to the inlet space (4) via at least one sealing-air duct (15). <IMAGE>

Description

TECHNICAL AREA

• (a) eine um eine Verdichterachse drehbare Rotorwelle mit einer Mehrzahl von an ihrem Umfang befestigten Laufschaufeln;
• (b) ein die Rotorwelle im Bereich der Laufschaufeln umgebendes Verdichtergehäuse;
• (c) ein auf der Eintrittsseite des Verdichters die Rotorwelle umschliessendes Einlassgehäuse mit einer Aussenschale und einer Innenschale, zwischen denen ein Eintrittsraum für die zu verdichtende Luft gebildet wird, welcher Eintrittsraum auf der einen Seite über einen mit einem Eintrittsfilter versehenen Lufteintritt mit der Umgebung in Verbindung steht, und auf der anderen Seite in einen mit verstellbaren oder festen Einlassleitschaufeln ausgestatteten Ansaugkanal übergeht, wobei die Aussenschale an das Verdichtergehäuse anschliesst; und
• (d) an dem den Laufschaufeln zugewandten Ende der Innenschale ein Dichtungsgehäuse, welches am Umfang der Rotorwelle anliegend den Ansaugkanal gegen die Umgebung abdichtet und eine Dichtungsluftkammer umfasst, aus der Dichtungsluft in den Ringspalt zwischen Dichtungsgehäuse und Rotorwelle austreten kann.

The present invention relates to the field of turbomachines. It relates comprehensively to a compressor, in particular for gas turbines

• (a) a rotor shaft rotatable about a compressor axis with a plurality of rotor blades attached to its periphery;
• (b) a compressor housing surrounding the rotor shaft in the region of the rotor blades;
• (c) an inlet housing enclosing the rotor shaft on the inlet side of the compressor with an outer shell and an inner shell, between which an inlet space for the air to be compressed is formed, which inlet space on the one hand communicates with the surroundings via an air inlet provided with an inlet filter stands, and on the other hand merges into an intake duct equipped with adjustable or fixed inlet guide vanes, the outer shell connecting to the compressor housing; and
• (d) at the end of the inner shell facing the rotor blades, a sealing housing which, adjacent to the circumference of the rotor shaft, seals the intake duct from the environment and comprises a sealing air chamber from which sealing air can escape into the annular gap between the sealing housing and the rotor shaft.

Such a compressor is e.g. from the article by J. P. Smed and H. Saeki, A NEW DESIGN FOR A COMPRESSOR INLET CASING ATMOSPHERIC VENT SYSTEM, ASME Cogen-Turbo, IGTI-Vol. 7, p.535-537 (ASME 1992).

STATE OF THE ART

With compressors, such as those used as part of a gas turbine, precautions must be taken to seal spaces with different pressures against each other during operation on the rotating rotor shaft, so that the efficiency of the compressor remains high and faults - such as those caused by the ingress of lubricating oil can be triggered from the bearings in the compressor duct - safely avoided.

A possible type of seal is the seal with pressurized air, such as e.g. in US-A-3,031,132 for the gas turbine of an aircraft. The rotor shaft is ring-shaped at the point to be sealed by a sealing chamber accommodated in a corresponding sealing housing. The pressurized sealing air can escape from the sealing chamber into the annular gap between the sealing housing and the rotor shaft, thus limiting or completely preventing the penetration of undesired media into the annular gap. The compressed air is usually drawn off from one or optionally several pressure stages of the compressor and fed into the sealing chamber via a suitable valve circuit and control.

Such a compressed air seal can be arranged at various points on the compressor: in the cited US patent, the seal housing, which can also take on cooling tasks at the same time, is arranged next to the high-pressure shaft bearing of the compressor. A prior art is described in the publication mentioned at the beginning (See FIGS. 1 and 2 there), in which the seal is arranged on the input-side axle bearing, where the rotor shaft goes out and the compressor housing merges into the inlet housing. The main aim of this is to prevent unfiltered and possibly oil-contaminated outside air from being pressed via the bearing into the vacuum part of the compressor on the inlet side and mixing with the compressor air.

If the compressor is operated with fixed or little changing parameters, the effort for the compressed air seal is kept within tolerable limits. However, this solution becomes impractical if adjustable inlet guide vanes are provided at the inlet of the compressor, with which the inlet air flow can be throttled to a considerable extent at part load. Since the air pressure in the compressor reaches an atmospheric level at the earliest after about the third compression stage, it is necessary to extract the compressed air at the fifth stage or later. If, on the other hand, the throttling is eliminated, the temperature and pressure of a compressed air extracted at the fifth stage or later at 180 ° C. and 4 bar are too high, so that a changeover valve is necessary in order to draw off the compressed air at a cooler stage.

In the publication mentioned at the beginning (Smed and Saeki), an air-operated seal has been proposed which does not require external control and regulating circuits (FIG. 4). This is achieved in that the sealing chamber, which is to separate the suction side of the compressor which is under vacuum from the bearing, which is also but at a lower vacuum, is acted upon by cooling air through a duct which is at atmospheric pressure.

However, this known solution has one problem in particular: the cooling air on the inlet side is usually not subjected to special filtering so that here too (via the sealing air) impurities can be introduced into the compressor duct.

PRESENTATION OF THE INVENTION

It is an object of the invention to provide a compressor with a seal in which the risk of contamination is considerably reduced.

• (e) die Dichtungskammer über wenigstens einen Dichtungsluftkanal mit dem Eintrittsraum in Verbindung steht.

The object is achieved in a compressor of the type mentioned in that

• (e) the sealing chamber is connected to the entry space via at least one sealing air duct.

The essence of the invention consists in tapping the sealing air behind the inlet filter and in front of the inlet guide vanes from the inlet space, the removal preferably taking place in front of the intake duct. Filtered air is available there, which has approximately atmospheric pressure and can therefore perform the desired sealing tasks.

• (a) in dem Ringspalt zwischen Dichtungsgehäuse und Rotorwelle in Richtung der Verdichterachse hintereinanderliegend eine Mehrzahl von Dichtrippen angeordnet ist, welche Dichtrippen abwechselnd von dem Dichtungsgehäuse und der Rotorwelle ausgehend in den Ringspalt hineinragen und durch ihren Abstand von der gegenüberliegenden Seite ein radiales Spiel definieren; und
• (b) die Dichtrippen in zwei Gruppen unterteilt sind, und die Dichtungsluft durch eine zwischen den beiden Gruppen angeordnete Dichtungsluftöffnung aus der Dichtungsluftkammer in den Ringspalt ausströmt.

A preferred embodiment of the invention is characterized in that

• (a) a plurality of sealing ribs is arranged one behind the other in the annular gap between the sealing housing and the rotor shaft in the direction of the compressor axis, which sealing ribs alternately protrude from the sealing housing and the rotor shaft into the annular gap and define a radial play due to their distance from the opposite side; and
• (b) the sealing ribs are divided into two groups, and the sealing air flows out of the sealing air chamber into the annular gap through a sealing air opening arranged between the two groups.

By dividing the sealing ribs, the ratio between the quantities of sealing air and ambient air flowing through the annular gap can be optimized in a simple manner. Likewise, an optimization between partial load (adjustable inlet guide vanes) and full load is possible.

Further embodiments result from the dependent claims.

BRIEF EXPLANATION OF THE FIGURES

Fig. 1

im Längsschnitt einen Teil der Ansaugseite gemäss einem bevorzugten Ausführungsbeispiel des Verdichters nach der Erfindung;

Fig. 2

im vergrösserten Ausschnitt die eigentliche Dichtung eines zweiten Ausführungsbeispiels des erfindungsgemässen Verdichters;

Fig. 3

ein Diagramm der Druckverhältnisse im Ansaugtrakt des Verdichters nach Fig. 1 ohne (Kurve a) und mit (Kurve b) Drosselung;

Fig. 4

die bei einem Verdichter gemäss Fig. 2 am Ringspalt auftretenden Leckagedurchflüsse (L) von Dichtungsluft (Intake Air IA) und Umgebungsluft (Ambient Air AA) ohne (a) und mit (b) Drosselung;

Fig. 5

die Abhängigkeit der Leckagedurchflüsse (L) aus Fig. 4 von der Aufteilung der Dichtrippen im Ringspalt; und

Fig. 6

die zu Fig. 5 gehörende Darstellung der für die Durchflüsse zugrundegelegten Dichtungsgeometrie.

The invention will be explained in more detail below on the basis of exemplary embodiments in connection with the figures. Show it

Fig. 1

in longitudinal section part of the suction side according to a preferred embodiment of the compressor according to the invention;

Fig. 2

in the enlarged detail the actual seal of a second embodiment of the compressor according to the invention;

Fig. 3

a diagram of the pressure conditions in the intake tract of the compressor of Figure 1 without (curve a) and with (curve b) throttling.

Fig. 4

the leakage flow rates (L) of sealing air (Intake Air IA) and ambient air (Ambient Air AA) occurring in a compressor according to FIG. 2 without (a) and with (b) throttling;

Fig. 5

the dependence of the leakage flow rates (L) from FIG. 4 on the distribution of the sealing ribs in the annular gap; and

Fig. 6

the representation belonging to FIG. 5 of the sealing geometry on which the flow rates are based.

WAYS OF CARRYING OUT THE INVENTION

In Fig. 1 the suction side of a preferred embodiment of a compressor according to the invention is shown in longitudinal section. The compressor 1 comprises a rotor shaft 10 which can be rotated about a compressor axis 18. The rotor shaft 10 is guided outwards on the right side of the figure and is equipped on the left side with a plurality of rotor blades 7 fastened to its circumference, only rotor blades of the first of which are shown here Level are shown.

The rotor shaft 10 is surrounded in the region of the rotor blades 7 by a compressor housing 2 which has guide vanes (not shown) and forms the actual compressor together with the rotor. The rotor shaft 10 is enclosed by an inlet housing 9 on the inlet side of the compressor 1. The inlet housing 9 consists of an outer shell 3 and an inner shell 16, between which an inlet space 4 for the air to be compressed is formed. The entry space 4 is connected on one side to the surroundings via an air inlet 5 provided with an inlet filter 6. On the other hand, it merges into an intake duct 27 equipped with inlet guide vanes 8. The outer shell 3 of the inlet housing 9 adjoins the compressor housing 2. The inlet guide vanes 8 themselves are adjustable here and rotatably supported in the seal housing 11 by means of the blade bearings 26a in the compressor housing 2 and 26b (FIG. 2).

To seal the space downstream downstream of the inlet guide vane 8, in which there is negative pressure during operation of the compressor, against the ambient air, a seal housing is provided on the end of the inner shell 16 facing the rotor blades 7 11 provided. The seal housing 11 lies at a small distance on the circumference of the rotor shaft 10 and contains a sealing air chamber 12, from which sealing air can escape into the annular gap 28 (FIG. 2) formed between the sealing housing 11 and the rotor shaft 10. The rotor shaft 10 is supported on the input side by means of a shaft bearing 17 attached to the inner wall of a bearing housing 25.

The sealing air flowing out of the sealing air chamber 12 into the annular gap 28 is drawn off from the inlet space 4. For this purpose, one or more sealing air channels 15 are provided, which e.g. run in the form of bores in the interior of the inner shell 16 and connect the sealing air chamber 12 to the inlet space 4 via a respective sealing air inlet 13. Each sealing air duct 15 can advantageously have a second inlet, which is normally closed with a closure plate 14, but in special cases allows the sealing air to be obtained from a separate, connected compressed air system. Tapping the sealing air from the inlet space 4 has the particular advantage that the sealing air, like the air to be compressed, has passed the inlet filter 6 and is thus freed from harmful impurities to the same extent as the compressor air itself.

In Fig. 3, the pressure curve of the static pressure P _s in the intake tract of the compressor from Fig. 1 is shown schematically for two different operating states, the circled Roman numerals I to III denoting different locations of the intake tract. (I) denotes the outside of the inlet filter 6, (II) the inlet space 4 and (III) the part of the intake duct 27 behind the inlet guide vanes 8 and in front of the first compressor stage.

The solid curve (a) represents the pressure curve in the event that the inlet guide vanes 8 are fully open, ie in the target position of the compressor design point are posed. In this case, the pressure drops slightly from the environment to the inlet space 4 because the cross sections are large enough here. In contrast, it falls more sharply in the intake duct 27 because the cross sections are correspondingly smaller here or the air is accelerated accordingly.

The dashed curve (b) represents the pressure curve in the event that the inlet guide vanes 8 are in a throttle position rotated by a large angle, so that up to 50% less air reaches the compressor. In this case, the pressure drop in the intake duct is greater because of the increased flow resistance of the inlet guide vanes 8, while the course to the inlet space 4 flattens out because of the reduced flow.

The flow conditions in the sealing area itself can be explained on the basis of the enlarged detail from FIG. 2: The sealing housing 11 with the sealing air chamber 12 lying inside and closed off by a closing ring 19 is attached to a flange-like end of the inner shell 16. The seal housing 11 encloses the rotor shaft 10 at a short distance, so that the annular gap 28 remains between the housing and the shaft. The solution drawn from the inlet chamber 4 the sealing air IA (I Ntake A ir) into the sealing air chamber 12 passes through the sealing air passage 15 and flows from there through the sealing air openings 21 in the annular gap 28th

On the right side of the seal housing 11, in the ambient space 22, there is ambient air AA ( A mbient A ir) under normal pressure. It is sealed against the shaft bearing by means of various sealing elements 23, 24. On the left side of the seal housing 11 there is largely the negative pressure that occurs downstream of the inlet guide vanes 8 when the compressor is in operation. For this reason, there is a pressure gradient along the annular gap 28, which Ambient air AA and the sealing air IA emerging in the annular gap drive to the left through the annular gap.

The annular gap 28 itself has a thickness of a few millimeters. The flow resistance in the annular gap 28 is increased by a large number of sealing ribs 20 arranged one behind the other in the axial direction (see also FIG. 6). The sealing ribs 20 alternately protrude from the inner wall of the seal housing 11 and from the outer surface of the rotor shaft 10 perpendicular to the compressor axis 18 into the annular gap 28 and, with their distance from the opposite wall, define a radial play S (FIG. 6), which is preferably about 1 mm. The entirety of the sealing ribs 20 is divided into two groups 20a and 20b, one of which, 20a, is arranged downstream of the sealing air opening 21 and the other, 20b, in front of it. Instead of the sealing ribs alternatingly emanating from the inner wall of the seal housing 11 and from the outer surface of the rotor shaft 10, the sealing ribs 20 can also be fitted exclusively on the rotor shaft 10 according to an exemplary embodiment not shown.

The two groups 20a, b of sealing ribs essentially determine the leakage flows of the sealing air IA and ambient air AA through the annular gap in terms of the number and division of the ribs. For the typical sealing geometry shown in FIG. 2 of a large gas turbine compressor with 9 pairs of sealing ribs 20, ie, 9 upper and 9 lower sealing ribs, of which 6 pairs are arranged in group 20a and 3 pairs in group 20b, and a radial clearance S of 1 mm results in the leakage flow rates L for IA and AA shown in the diagram in FIG. 4, L₀ being the sum of the air quantities IA and AA in case (a) of the example shown in FIG. 4. Case (a) in turn relates to fully opened inlet guide vanes 8, while case (b) refers to the strong throttle position already mentioned.

Although, in contrast to a conventional sealing system working with compressed air, the leakage flow L of ambient air AA cannot be completely prevented in the compressor according to the invention, it is nevertheless very low even in the worst case (a) and decreases further when the compressor 1 operates in throttle mode (Case b). This leakage flow can also be further reduced at the cost of bypassing the throttling if the distribution of the sealing ribs 20 to the groups 20a and 20b is carried out differently. This results from the diagram in FIG. 5, which relates to the sealing geometry shown again in FIG. 6. The diagram shows the change in the leakage flows L of the sealing air IA and the ambient air AA as a function of the number n of the pairs of sealing ribs, which are arranged in a constant total number of 9 pairs in the group 20b (a and b here in turn relate to the Operating mode with and without throttling; the case n = 3 otherwise corresponds to the illustration in FIG. 4). Of course, the invention can also be applied to compressors with rigid inlet guide vanes 8.

• es gibt einen vernachlässigbar kleinen Anteil von einströmender Luft, die am Eintrittsfilter vorbei in das Verdichtersystem eintritt
• die Dichtung benötigt keine Druckluftversorgungsleitungen und -steuerventile
• da die Dichtungsluft an einer Stelle stromauf anstelle von stromab abgezapft wird, ergibt sich durch eine Drosselung mittels der Einlassleitschaufeln 8 eine Verbesserung der Dichtwirkung

Overall, the invention results in a compressor which is distinguished by the following advantages:

• there is a negligibly small proportion of incoming air that passes the inlet filter and enters the compressor system
• the seal does not require compressed air supply lines and control valves
• since the sealing air is tapped at an upstream position instead of downstream, throttling by means of the inlet guide vanes 8 improves the sealing effect

LIST OF DESIGNATIONS

1

compressor

2nd

Compressor housing

3rd

Outer shell (inlet housing)

4th

Entry space

5

Air intake

6

Inlet filter

7

Blade

8th

Inlet guide vane (rotatable or fixed)

9

Inlet housing

10th

Rotor shaft

11

Seal housing

12th

Sealing air chamber

13

Sealing air inlet

14

Sealing plate

15

Sealing air duct

16

Inner shell (inlet housing)

17th

Shaft bearing

18th

Compressor axis

19th

Graduation ring

20.20a, b

Sealing rib

21

Seal air opening

22

Surrounding space (bearing housing)

23.24

Sealing element

25th

Bearing housing

26a, b

Shovel bearing

27

Intake duct

28

Annular gap

IA

Sealing air

AA

Ambient air

L

Leakage flow

n

Number of sealing rib pairs 20b

P _s

static pressure

S

radial play

Claims (5)

Compressors, in particular for gas turbines, comprehensive (a) a rotor shaft (10) rotatable about a compressor axis (18) with a plurality of rotor blades (7) attached to its circumference; (b) a compressor housing (2) surrounding the rotor shaft (10) in the region of the rotor blades (7); (c) an inlet housing (9) enclosing the rotor shaft (10) on the inlet side of the compressor (1) with an outer shell (3) and an inner shell (16), between which an inlet space (4) for the air to be compressed is formed, which inlet space (4) communicates with the environment on one side via an air inlet (5) provided with an inlet filter (6), and on the other side merges into an intake duct (27) equipped with adjustable or fixed inlet guide vanes (8) , wherein the outer shell (3) connects to the compressor housing (2); and (d) a seal housing (11) on the end of the inner shell (16) facing the rotor blades (7), which seals the suction channel (27) against the environment and which includes a sealing air chamber (12), lying against the circumference of the rotor shaft (10) the sealing air can escape into the annular gap (28) between the sealing housing (11) and the rotor shaft (10); characterized in that (e) the sealing chamber (12) is connected to the inlet space (4) via at least one sealing air duct (15). Compressor according to claim 1, characterized in that (a) a plurality of sealing ribs (20) is arranged one behind the other in the annular gap (28) between the sealing housing (11) and the rotor shaft (10) in the direction of the compressor axis (18), which starts from the rotor shaft (10) into the annular gap (28 ) protrudes and defines a radial play (S) by their distance from the opposite side; and (b) the sealing ribs (20) are divided into two groups (20a, b), and the sealing air from the sealing air chamber (12) into the annular gap (28) through a sealing air opening (21) arranged between the two groups (20a, b) emanates. Compressor according to claim 1, characterized in that (a) a plurality of sealing ribs (20) is arranged one behind the other in the annular gap (28) between the sealing housing (11) and the rotor shaft (10) in the direction of the compressor axis (18), which sealing ribs (20) alternately from the sealing housing (11) and protrude the rotor shaft (10) into the annular gap (28) and define a radial play (S) by its distance from the opposite side; and (b) the sealing ribs (20) are divided into two groups (20a, b), and the sealing air from the sealing air chamber (12) into the annular gap (28) through a sealing air opening (21) arranged between the two groups (20a, b) emanates. Compressor according to Claim 3, characterized in that the group of sealing ribs (20b) arranged between the sealing air opening (21) and the surroundings has a plurality of pairs of sealing ribs. Compressor according to one of claims 1 to 4, characterized in that the at least one sealing air duct (15) runs inside the inner shell (16) of the inlet housing (9), and in that the at least one sealing air duct (15) on the one hand is connected to the inlet space (4) via a sealing air inlet (13) and on the other hand has a closable connection for a separate compressed air line.

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