U.S. patent application number 12/881655 was filed with the patent office on 2011-03-24 for gas turbine with a shroud and labyrinth-type sealing arrangement.
This patent application is currently assigned to Rolls-Royce Deutschland Ltd & Co KG. Invention is credited to Robert BENTON, Zbigniew SCHABOWSKI.
Application Number | 20110070074 12/881655 |
Document ID | / |
Family ID | 42537784 |
Filed Date | 2011-03-24 |
United States Patent
Application |
20110070074 |
Kind Code |
A1 |
SCHABOWSKI; Zbigniew ; et
al. |
March 24, 2011 |
GAS TURBINE WITH A SHROUD AND LABYRINTH-TYPE SEALING
ARRANGEMENT
Abstract
A gas turbine with a shroud and labyrinth-type sealing
arrangement has a casing 1 and at least one rotor 9, whose blades 2
are provided with a shroud 3. The labyrinth seal 4 is provided
between the shroud 3 and the casing 1 and the shroud 3 includes at
least two radially spaced and axially protruding annular fins 5,
which are part of the labyrinth seal 4 At least one sealing fin 6
is provided on the casing 1 which extends essentially radially to
the shroud 3 at least over a part of the circumference and at least
partly in a space between the annular fins 5.
Inventors: |
SCHABOWSKI; Zbigniew;
(Berlin, DE) ; BENTON; Robert; (Berlin,
DE) |
Assignee: |
Rolls-Royce Deutschland Ltd &
Co KG
Blankenfelde-Mahlow
DE
|
Family ID: |
42537784 |
Appl. No.: |
12/881655 |
Filed: |
September 14, 2010 |
Current U.S.
Class: |
415/174.5 |
Current CPC
Class: |
F01D 11/08 20130101 |
Class at
Publication: |
415/174.5 |
International
Class: |
F01D 11/02 20060101
F01D011/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 24, 2009 |
DE |
10 2009 042 857.7 |
Claims
1. A gas turbine, comprising: a casing; at least one rotor having
blades provided with a shroud; a labyrinth seal provided between
the shroud and the casing, the shroud including at least two
axially spaced and radially outwardly protruding annular fins
forming a part of the labyrinth seal; at least one sealing fin
provided on the casing which extends essentially radially inwardly
from a surface of the casing toward the shroud at least over a part
of the circumference and at least partly in a space between the
annular fins.
2. The gas turbine of claim 1, wherein the sealing fin is provided
as a ring.
3. The gas turbine of claim 1, wherein the sealing fin is
circumferentially segmented.
4. The gas turbine of claim 1, wherein the sealing fin has a
circumferentially constant cross-section.
5. The gas turbine of claim 1, wherein the sealing fin has a
circumferentially varying cross-section.
6. The gas turbine of claim 1, wherein the sealing fin has an
essentially rectangular cross-section.
7. The gas turbine of claim 1, wherein the sealing fin has a
rounded cross-section.
8. The gas turbine of claim 1, wherein the sealing fin has an
essentially radially oriented cross-section.
9. The gas turbine of claim 1, wherein the sealing fin has a
cross-section which is inclined to a radial direction.
10. The gas turbine of claim 1, wherein the sealing fin is integral
with the casing.
11. The gas turbine of claim 1, wherein the sealing fin is a
separate item connected to the casing.
12. The gas turbine of claim 1, wherein the casing includes a
conically widening axial cross-section.
13. The gas turbine of claim 1, wherein the casing includes a
stepped axial cross-section with sealing fins positioned on the
casing steps.
Description
[0001] This application claims priority to German Patent
Application DE102009042857.7 filed Sep. 24, 2009, the entirety of
which is incorporated by reference herein.
[0002] This invention relates to a gas turbine having a shroud and
labyrinth-type sealing arrangement.
[0003] More particularly, the present invention relates to an
axial-flow turbine of a gas-turbine engine provided with at least
one bladed rotor having--arranged on its outer periphery--a
segmental shroud joining the blade tips.
[0004] The term "casing" as used in this invention refers to a
non-rotating component including any tubular component which is not
a casing as such. The component referred to as a casing in the
present invention can be an arrangement of structural elements, a
ring or a part of the actual turbine casing.
[0005] On the turbine of a gas-turbine engine, power is extracted
from the gas flow released from the combustion chamber to thereby
produce a torque to drive a compressor. For this purpose, the
turbine has a number of stationary vanes and at least one rotor
provided with a blade row. The number of these components is
variable according to the present invention.
[0006] The rotor moves relatively to the casing, with the required
free movability of the rotor being provided by a gap between the
rotor and the casing. This gap invariably involves a certain amount
of leakage flow entailing, in particular, two negative effects
compromising the efficiency of the turbine. Firstly, the leakage
flow reduces the gas mass flowing through the rotor, thereby
decreasing the power extracted. Secondly, the flow caused by the
gap affects the actual flow through the turbine as they have
different angles and different local velocities. This results in a
mixing of both flows and a reduction of the aerodynamic efficiency.
The leakage flow also leads to a degradation of the inflow into a
subsequent stator vane row.
[0007] From the state of the art it is known to reduce the leakage
flow by use of suitable sealing measures in the form of a
labyrinth-type sealing arrangement. FIGS. 3 and 4 schematically
show a blade root 7 that is part of a rotor 9. Arranged on the
respective blade root 7 is a blade 2. The radially outward end
areas of the blades 2 are joined by a shroud 3 being essentially
annular and composed of, for example, individual segments.
[0008] The shroud 3 is provided with several, essentially radially
outwardly extending sealing fins 5. FIGS. 3 and 4 each show three
such sealing fins 5.
[0009] The sealing fins 5 together with the wall of a casing 1 form
a labyrinth seal 4. The dashed lines in FIGS. 3 and 4 show the flow
through the labyrinth seal. While a stepped casing contour with
casing steps 8 is provided in FIG. 3, FIG. 4 shows a conically
widening casing cross-section (in axial cross-sectional view).
Accordingly, FIGS. 3 and 4 show a meridional section of the turbine
rotor and the casing.
[0010] The annular fins 5 can be oriented purely radially, but are
also axially inclinable, as shown in FIGS. 3 and 4. Furthermore, it
is known from the state of the art to provide varying numbers of
such annular fins 5.
[0011] The dashed lines in the representations of FIGS. 3 and 4
show that the leakage flow, although being obstructed in the
labyrinth seal 4, still passes the latter to an amount that is
capable of producing the detriments described earlier. This applies
in particular where design or thermal operating conditions entail a
larger radial spacing between the shroud and the casing.
[0012] In a broad aspect, the present invention provides a gas
turbine with a shroud and labyrinth-type sealing arrangement,
which, while being simply designed and cost-effectively producible,
avoids the disadvantages of the state of the art and ensures
optimum sealing efficiency.
[0013] According to the present invention, it is therefore provided
that, on the casing, at least one sealing fin is arranged which
extends essentially radially inwardly to the shroud at least over a
part of the circumference and at least partly in a space between
the annular fins.
[0014] The sealing fin, which according to the present invention
can be a closed axial ring or circumferentially segmented,
therefore is a flow barrier additionally obstructing the leakage
flow. Thus, the flow mass of the leakage flow is reduced.
[0015] The sealing fins according to the present invention can have
a circumferentially constant or varying cross-section. The
cross-section can, for example, be rectangular with sharp edges,
but it is also possible to provide a rounded cross-section or an
additional leakage flow barrier by way of a special cross-sectional
configuration. Furthermore, the cross-section of the sealing fins
can be such that the sealing fins are also arranged axially
inclined. Here, one side or both sides are angularly inclinable
relative to the axial direction. Also, the radially situated end
face can be slanted or straight. Also providable is a stepped
cross-section or a parallelogrammatic cross-section.
[0016] According to the present invention, the sealing fins can be
either integral with the casing or provided as separate items
connected to the casing, for example as annular segments or the
like.
[0017] The present invention is applicable to both conically
smooth, widening casing cross-sections and stepped casing
cross-sections (in each case relative to an axial sectional
view).
[0018] Accordingly, the present invention is advantageous in that
the leakage flow through the annular gap between the surface of the
shroud and the casing is considerably obstructed. The jet-type
flow, which is accelerated upon passing the annular fins, is
significantly obstructed and deflected with regard to the flow
direction as it impinges on the sealing fins according to the
present invention. Thus, kinetic energy of the leakage flow is
dissipated, resulting in a reduced mass of the leakage flow.
Similarly, the leakage flow passing the sealing fins is obstructed
upon impinging on the axially subsequent sealing fin of the casing
or shroud, with flow energy here also being dissipated.
Accordingly, a considerable obstruction of the leakage flow is
provided by one sequence or several sequences of annular fins and
sealing fins, resulting in an improvement of the sealing
efficiency. Thereby, the negative effects described earlier are
reduced, allowing the blade areas to be flown with less disturbance
and better efficiency. This provides for an overall higher
efficiency of the turbine.
[0019] The present invention is more fully described in light of
the accompanying drawings, showing preferred embodiments. In the
drawings,
[0020] FIG. 1 is a schematic axial sectional view of a first
embodiment of the present invention;
[0021] FIG. 2 is a view, analogically to FIG. 1, of a modified
embodiment of the present invention;
[0022] FIG. 3 (Prior Art) is an illustration applicable to the
state of the art, analogically to FIG. 2; and
[0023] FIG. 4 (Prior Art) is an illustration applicable to the
state of the art, analogically to FIG. 2.
[0024] In the embodiments, like parts carry the same reference
numerals.
[0025] FIGS. 1 and 2 show, analogically to FIGS. 3 and 4, a casing
1 which can be provided with casing steps 8 (FIG. 1) or have a
smooth, conically widening surface (FIG. 2).
[0026] As regards the description of rotor 9, the blades 2, the
shroud 3 and the annular fins 4, reference is made to the
description of FIGS. 3 and 4 applicable to the state of the
art.
[0027] FIGS. 1 and 2 show in dashed representation the flow through
the gap between the shroud 3 and the surface of the casing 1.
[0028] According to the present invention, sealing fins 6 extending
essentially in the radially inward direction are arranged in the
spaces between axially spaced annular fins 5. Accordingly, in one
embodiment, a sealing fin 6 is disposed in each space. According to
the examples of FIGS. 1 and 2, the sealing fins 6 have rectangular
cross-section. However, the cross-section is also variable, both
circumferentially and in departure from the rectangular
cross-section.
[0029] The representations in FIGS. 1 and 2 convey that the sealing
fins 6 effect a considerable obstruction of the flow and a
significant mass flow reduction of the leakage flow through the
labyrinth seal 4.
[0030] According to the present invention, the sealing fins 6 are
provided such that they obstruct the flow without contacting the
shroud 3 and/or the annular fins 5. Accordingly, they do not form
elements of a rubbing-contact sealing arrangement, but rather a
defined distance is provided between the sealing fins 6 and the
shroud 3 and/or the annular fins 5.
LIST OF REFERENCE NUMERALS
[0031] 1 Casing [0032] 2 Blade [0033] 3 Shroud [0034] 4 Labyrinth
seal [0035] 5 Annular fin/shroud fin/shroud sealing fin [0036] 6
Sealing fin/casing fin/casing sealing fin [0037] 7 Blade root
[0038] 8 Casing step [0039] 9 Rotor
* * * * *