U.S. patent application number 09/877711 was filed with the patent office on 2002-01-10 for exhaust turbine for a turbocharger.
Invention is credited to Doring, Volker, Hensel, Hans-Dieter, Schick, Peter.
Application Number | 20020004007 09/877711 |
Document ID | / |
Family ID | 7645328 |
Filed Date | 2002-01-10 |
United States Patent
Application |
20020004007 |
Kind Code |
A1 |
Doring, Volker ; et
al. |
January 10, 2002 |
Exhaust turbine for a turbocharger
Abstract
In an exhaust turbine of a turbocharger with a rotor mounted
rotatably in a turbine casing having a spiral inlet duct with a
guide vane structure including guide vanes arranged around the
rotor and extending essentially tangentially to an outer and inner
imaginary circular surface areas in the inflow zone and,
respectively, the outflow zone of the guide vane structure, at
least the trailing edges but preferably also the leading edges of
the guide vanes extend at an angle to an axial line of the
imaginary circular surface areas, thereby providing for a uniform
loading of the rotor.
Inventors: |
Doring, Volker; (Stuttgart,
DE) ; Hensel, Hans-Dieter; (Vaihingen, DE) ;
Schick, Peter; (Esslingen, DE) |
Correspondence
Address: |
KLAUS J. BACH & ASSOCIATES
PATENTS AND TRADEMARKS
4407 TWIN OAKS DRIVE
MURRYSVILLE
PA
15668
US
|
Family ID: |
7645328 |
Appl. No.: |
09/877711 |
Filed: |
June 8, 2001 |
Current U.S.
Class: |
415/203 |
Current CPC
Class: |
F02C 6/12 20130101; F05D
2250/34 20130101; F05D 2250/35 20130101; F05D 2220/40 20130101;
F05D 2250/15 20130101 |
Class at
Publication: |
415/203 |
International
Class: |
F01D 001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 9, 2000 |
DE |
100 28 733.6 |
Claims
What is claimed is:
1. An exhaust turbine for a turbocharger comprising a turbine
casing with a spiral inlet duct, a rotor mounted rotatably in said
turbine casing, a guide vane structure with guide vanes arranged in
said inlet duct so as to surround the rotor, said guide vanes
extending essentially tangentially to an outer and an inner
imaginary circular surface in an inflow area and an outflow area of
said guide vane structure, said guide vanes having leading edges
and trailing edges with at least said trailing edges extending at
an angle to axial lines of said imaginary circular surfaces.
2. An exhaust turbine according to claim 1, wherein both, said
trailing edges and said leading edges of said guide vanes extend at
an angle to axial lines of the respective imaginary circular
surfaces.
3. An exhaust turbine according to claim 1, wherein said guide
vanes have different circumferential lengths.
4. An exhaust turbine according to claim 1, wherein said guide
vanes are connected to one another by cover rings disposed at the
axial ends of said guide vanes.
Description
[0001] The invention relates to an exhaust turbine for a
turbocharger including a turbine rotor which is rotatably supported
in a turbine housing including a spiral inlet duct with a guide
vane structure for guiding the exhaust gas onto the turbine
rotor.
BACKGROUND OF THE INVENTION
[0002] Exhaust gas turbochargers are used both for
compression-ignition reciprocating-piston internal combustion
engines with quality control and for spark-ignition
reciprocating-piston internal combustion engines with quality
control or quantity control to boost the power output or improve
the quality of the exhaust gas by using compressed air to improve
cylinder charging and the utilization of the expansion energy of
the combustion gases.
[0003] Exhaust turbochargers are well-proven auxiliary devices.
They are of simple design and have a long life. They generally
comprise an exhaust turbine with a fixed blade geometry that drives
a radial compressor. While the exhaust turbine is a hydrodynamic
machine which works well together with the radial compressor, both
units combined as an exhaust gas turbocharger have an operating
behavior, which is different from that of a reciprocating-piston
internal combustion engine. The turbocharger behavior can be
adapted only with difficulty to the requirements of the
reciprocating-piston internal combustion engine. If the exhaust
turbocharger is designed for the full-load range of the
reciprocating-piston internal combustion engine, the delivery
pressure in the low-speed range is inadequate because of a reduced
mass flow of exhaust gas and reduced gas velocity through the
exhaust turbine. If, on the other hand, the exhaust turbocharger is
designed for the low-speed range of the reciprocating-piston
internal combustion engine, the flow volume in the full-load range
is too high, making it necessary to discharge an excessive quantity
of exhaust gas via a bypass valve in order to avoid exceeding the
desired boost pressure. This results in considerable losses of
efficiency.
[0004] To mitigate the conflict of objects described above, exhaust
turbochargers with variable blade geometry are used. EP 0 598 174
A1 describes an exhaust turbocharger for an internal combustion
engine, the exhaust turbine of which has a rotor that is surrounded
by a gas flow distributor with an at least partially diagonal gas
flow through it and with a spiral inlet guide duct. The inlet guide
duct includes an outlet zone in the form of an annular nozzle, in
which a variable guide vane structure is arranged. When the
internal combustion engine is at full load, the flow cross-section
of the guide vane structure is completely open. During part load
operation of the internal combustion engine, the guide vane
structure is partially closed for reducing the flow cross-section
by a rotating a part of the guide vane structure. These measures
enable the speed of the exhaust gas turbine to be maintained at a
high level also in the part-load range or even the low-speed range
of the internal combustion engine, despite the reduced volume flow,
and thus extend the effective operating range at the exhaust
gas-turbine end of the exhaust turbocharger. When the internal
combustion engine is being operated at full load, the throttling
effect of the guide vane structure can be used as an engine
brake.
[0005] DE 196 45 388 A1 discloses an exhaust turbine in which a
guide vane structure is disposed axially in an annular space
between a spiral inlet duct and a rotor. At its free end, the guide
vane structure has a cover ring, which covers an annular gap
between the turbine casing and an inner guide of the guide vane
structure, when the guide vane structure is in a retracted
position. This permits also a control of the inlet flow cross
section with effects comparable to those described above.
[0006] The rotor of the exhaust gas turbine is highly stressed,
especially in a braking mode. Upon rotation of the rotor, the rotor
blades are subjected to pulses according to the number of guide
vanes in the guide vane structure. As a result, the rotor blades
and the rotor may be excited into vibration, which stresses the
components and the mounting thereof.
[0007] It is the principal object of the invention to reduce the
stresses to which the rotor blades, the rotor and the mounting
thereof are subjected.
SUMMARY OF THE INVENTION
[0008] In an exhaust turbine of a turbocharger with a rotor mounted
rotatably in a turbine casing having a spiral inlet duct with a
guide vane structure including guide vanes arranged around the
rotor and extending essentially tangentially to an outer and inner
imaginary circular surface areas in the inflow zone and,
respectively, the outflow zone of the guide vane structure, at
least the trailing edges but preferably also the leading edges of
the guide vanes extend at an angle to an axial line of the
imaginary circular surface areas, thereby providing for a uniform
loading of the rotor.
[0009] Since the front and particularly the trailing ends of the
guide vanes are disposed at an angle with respect to an axial line,
the pressure pulses of the exhaust gas are distributed to the rotor
blades over an increased angular range, and the loading of the
individual rotor blades is reduced as the rotor is acted upon in an
almost uniform manner. It is furthermore possible to stagger the
sequence of pulses by giving the guide vanes different lengths thus
avoiding excitation either of the rotor blades or of the guide
vanes in the resonant frequency range.
[0010] According to another refinement of the invention, the guide
vanes are connected to one another by cover rings disposed at the
axial ends of the vanes. These rings also ensure that an annular
gap in the turbine casing is closed as much as possible by simple
means and, furthermore, they stabilize the thin-walled guide vanes.
Vibrations in the region of the guide vane structure are thereby
avoided.
[0011] The invention will become more readily apparent from the
following description of a preferred embodiment thereof described
below on the basis of the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 shows a partial longitudinal section through a
turbine casing of an exhaust turbine with a retracted guide vane
structure,
[0013] FIG. 2 shows in an axial cross-sectional view an axially
slideable guide vane structure, and
[0014] FIG. 3 is a cross-sectional view taken along line III-III of
FIG. 2.
DESCRIPTION OF A PREFERRED EMBODIMENT
[0015] FIG. 1 shows an exhaust gas turbine with a casing including
a dual-flow spiral inlet duct 3, which opens into an annular space
4. Adjoining this annular space 4 in the radial direction is a
rotor 5 of the exhaust gas turbine 1, which is provided with rotor
blades 6. Exhaust gases flow through the rotor 5 into an axially
aligned outlet duct 31 and, in the process, drive the rotor 5,
which is connected by a shaft 32 to an impeller (not shown
specifically) of a radial compressor to form a turbocharger as it
is well known in the art.
[0016] An annular axial slide 30, which carries a guide vane
structure 7 with guide vanes 8 to 12, is provided in an annular gap
25 between the turbine casing 2 and an inner guide member 26. These
guide vanes have different circumferential lengths 13 to 17 for
preventing the occurrence of resonant vibration during operation.
Cover rings 18 and 19 connect the axial ends of the guide vanes 8
to 12 to one another and stabilize the vanes. At the same time, the
outer cover ring 18 covers the annular gap 25 when the axial slide
30 is retracted (FIG. 1) While the inner cover ring 19 covers the
annular gap 25 in the operational position of the guide vane
structure.
[0017] At the end of the axial slide 30 remote from the guide vane
structure 7, there are slide lugs 28, by means of which the axial
slide 30 is guided circumferentially in an axially displaceable
manner in guide slots 29 of the inner guide member 26. A sliding
sleeve 27, which engages the axial slide 30 in the annular space 4
or moves it out of the annular space 4 acts on the end of the slide
lugs 28 (FIG. 1).
[0018] The guide vanes 8 to 12 extend essentially tangentially
between an imaginary outer circular surface 20 and an imaginary
inner circular surface 21 (FIG. 3). In the direction of the inlet
duct 3, the guide vanes 8 to 12 have leading edges 24, while they
have trailing edges 23 in the direction of the rotor 5. The
trailing edges 23 and the leading edges 24 extend at an angle .PHI.
with an axial line 22 on the inner circular surface 23 and the
outer circular surface 20, with the result that the gap between the
guide vanes 8 to 12 extends at an oblique angle to the axial line
22 and hence to the leading edges of the rotor blades 6 of the
rotor 5. The shock loading on the rotor blades 6 is thereby greatly
reduced and the rotor 5 is acted upon in an essentially uniform
manner.
* * * * *