U.S. patent application number 14/674177 was filed with the patent office on 2015-07-23 for fabrication of load compressor scroll housing.
The applicant listed for this patent is Hamilton Sundstrand Corporation. Invention is credited to Mark A. Fishburn, Nagendra Narasimha Kedlaya, Jeffrey L. Moore, Donna Jane Reid, Jessica Skaar.
Application Number | 20150204203 14/674177 |
Document ID | / |
Family ID | 47573120 |
Filed Date | 2015-07-23 |
United States Patent
Application |
20150204203 |
Kind Code |
A1 |
Moore; Jeffrey L. ; et
al. |
July 23, 2015 |
FABRICATION OF LOAD COMPRESSOR SCROLL HOUSING
Abstract
A method of fabricating a load compressor scroll housing
includes the steps of forging near net shape parts that are
machined and subsequently welded together. The forged portions are
machined to define specific features of the scroll housing along
with the mating surfaces. An interface between top and bottom
portions is defined within the volute chamber. The weld joint at
the interface provides a finished surface within the volute chamber
such that airflow is not adversely affected and additional machine
process are not required within the volute chamber after formation
of the weld joint.
Inventors: |
Moore; Jeffrey L.; (Alpine,
CA) ; Fishburn; Mark A.; (San Diego, CA) ;
Skaar; Jessica; (San Diego, CA) ; Kedlaya; Nagendra
Narasimha; (San Diego, CA) ; Reid; Donna Jane;
(Escondido, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hamilton Sundstrand Corporation |
Windsor Locks |
CT |
US |
|
|
Family ID: |
47573120 |
Appl. No.: |
14/674177 |
Filed: |
March 31, 2015 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13189691 |
Jul 25, 2011 |
9000324 |
|
|
14674177 |
|
|
|
|
Current U.S.
Class: |
60/805 ;
415/204 |
Current CPC
Class: |
F05D 2230/232 20130101;
B23K 26/24 20130101; Y10T 29/4924 20150115; F01D 9/026 20130101;
F04D 29/4206 20130101; F04D 17/10 20130101; F04D 29/624 20130101;
B23K 15/04 20130101; Y10T 29/49236 20150115 |
International
Class: |
F01D 9/02 20060101
F01D009/02; F04D 29/42 20060101 F04D029/42; F04D 17/10 20060101
F04D017/10 |
Claims
1. A load compressor for an auxiliary power unit comprising: a
scroll housing including a top portion welded to a bottom portion
defining a volute chamber having an outer wall and a annular
passage open to an inner cavity, a welded interface between the top
portion and the bottom portion disposed on the outer wall within
the volute chamber; and an impeller supported for rotation within
the inner cavity.
2. The load compressor for an auxiliary power unit as recited in
claim 1, including a bearing arrangement supported within the
scroll housing for supporting rotation of a shaft, the shaft
supporting rotation of the impeller.
3. The load compressor for an auxiliary power unit as recited in
claim 2, wherein the outer wall of the scroll housing includes a
boss at the location of the welded interface.
4. The load compressor for an auxiliary power unit as recited in
claim 1, wherein the volute chamber comprises an outer wall with
the interface between top and bottom portions being at the outer
wall.
5. The load compressor for an auxiliary power unit as recited in
claim 4, wherein the outer wall comprises an inner surface that is
part of the volute chamber and an outer surface that forms an outer
surface of the scroll housing.
6. The load compressor for an auxiliary power unit as recited in
claim 5, including a finished surface within the volute chamber at
the interface of the first and second mating surfaces.
7. An auxiliary power unit comprising: a turbine engine driving a
shaft; and a load compressor driven by the shaft, the load
compressor including a scroll housing including a top portion
welded to a bottom portion defining a volute chamber having an
outer wall and a annular passage open to an inner cavity, a welded
interface between the top portion and the bottom portion disposed
on the outer wall within the volute chamber, and an impeller
supported for rotation within the inner cavity.
8. The auxiliary power unit as recited in claim 7, including a
bearing arrangement supported within the scroll housing for
supporting rotation of a shaft, the shaft supporting rotation of
the impeller.
9. The auxiliary power unit as recited in claim 8, wherein the
outer wall of the scroll housing includes a boss at the location of
the welded interface.
10. The auxiliary power unit as recited in claim 7, wherein the
volute chamber comprises an outer wall with the interface between
top and bottom portions being at the outer wall.
11. The auxiliary power unit as recited in claim 10, wherein the
outer wall comprises an inner surface that is part of the volute
chamber and an outer surface that forms an outer surface of the
scroll housing.
12. The an auxiliary power unit as recited in claim 7, wherein the
impeller is driven by the shaft.
13. The auxiliary power unit as recited in claim 7, wherein the
turbine engine includes a compressor impeller communicating
compressed air to a combustor surrounding a turbine section, the
combustor communicating a high energy gas stream to the turbine to
drive the shaft.
14. The auxiliary power unit as recited in claim 13, wherein the
shaft comprises a common shaft driving the compressor impeller and
the impeller of the load compressor supported within the inner
cavity.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. application Ser.
No. 13/189,691 filed on Jul. 25, 2011.
BACKGROUND
[0002] This disclosure generally relates to assembly of a load
compressor for an auxiliary power unit. More particularly, this
disclosure relates to fabrication of a load compressor scroll
housing for an auxiliary power unit.
[0003] Aircraft utilize auxiliary power units for inflight
restarting of main engines and to supply compressed air and
electric power during ground operations. An auxiliary power unit
typically includes a small gas turbine engine that drives a load
compressor. The load compressor generates compressed air that can
be used for environmental systems and to aid in starting a main
engine. A load compressor includes an impeller driven by the small
gas turbine engine that generates compressed air guided through a
discharge scroll. The scroll is a volute passage defined by the
load compressor housing that directs compressed air through a
single outlet.
[0004] The volute passage is typically formed through known lost
wax casting processes. Lost wax casting can be inefficient for some
materials and therefore limits the materials utilized for forming
the scroll housing.
SUMMARY
[0005] A disclosed method of fabricating a load compressor scroll
housing includes the steps of forging near net shape parts that are
machined and then welded together. The forged portions are machined
to define specific features of the scroll housing along with the
mating surfaces.
[0006] The load compressor scroll housing includes a volute chamber
and annular passages that receive airflow from an impeller rotating
within a central cavity of the scroll housing. The interface
between top and bottom portions is defined within the volute
chamber. The weld joint at the interface provides a finished
surface within the volute chamber such that airflow is not
adversely affected and additional machining is not required within
the volute chamber after formation of the weld joint. The top and
bottom portions are formed in a near net shape forging process
starting with an aluminum billet. The forging operation from a
billet provides a homogenous material composition of the scroll
housing not reliably obtainable using other processes. An energy
beam is directed through an annular passage into the volute chamber
and against an outer wall to form the desired weld joint. The
finished weld joint provides a desired finish within the volute
chamber that does not adversely alter flow properties.
[0007] These and other features disclosed herein can be best
understood from the following specification and drawings, the
following of which is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic view of an example auxiliary power
unit.
[0009] FIG. 2 is a cross-sectional view of a portion of an example
auxiliary power unit.
[0010] FIG. 3 is a cross section of a load compressor for an
auxiliary power unit.
[0011] FIG. 4 is a sectional view of an example scroll housing for
a load compressor.
[0012] FIG. 5 is a perspective view of a top portion of the scroll
housing.
[0013] FIG. 6 is a schematic view of a bottom portion of the scroll
housing.
[0014] FIG. 7 is a cross-sectional view illustrating welding of the
top and bottom halves of the example scroll housing.
[0015] FIG. 8 is a perspective view of a completed example scroll
compressor housing.
DETAILED DESCRIPTION
[0016] Referring to FIGS. 1 and 2, an example auxiliary power unit
10 includes a gas turbine engine 12 that drives a load compressor
14 and an accessory drive unit 16. The load compressor 14 generates
compressed air that is driven through ducts 18. The gas turbine 12
includes an inlet that draws air into a compressor 42. The
compressor 42 is an impeller that is mounted onto a shaft 40 that
is driven by turbine 44. Air drawn in by the compressor 42 is
driven to combustor 46 where gasses are mixed with the compressed
air and ignited. The ignited gasses produce a gas stream that is
driven against the turbine 44 to drive the compressor 42. Also
mounted on the shaft 40 is an impeller 38 for the load compressor
14. Accordingly, the load compressor 14 is driven by the turbine 44
on the common shaft 40.
[0017] Referring to FIG. 3, with continued reference to FIG. 2, the
load compressor 14 includes a scroll housing 20 that defines a
volute chamber 22. Passage 24 provides for airflow from the
impeller 38 into the volute chamber 22. From the volute chamber 22
the compressed air is driven through the ducts 18 to various units
and accessories that utilize the compressed air. As appreciated,
compressed air is utilized for aircraft environmental control
systems and also to aid in the starting of a main aircraft engine.
Moreover, the terms scroll or volute are also used by those skilled
in the art to describe the example scroll housing 20 and other
structures that gather flow from a diffuser discharge annulus and
deliver that flow to a downstream pipe.
[0018] The example scroll housing 20 is fabricated from a top
portion 50 and a bottom portion 52. The top and bottom portions 50,
52 of the scroll housing 20 define both the volute chamber 22 and
the annular passages 24.
[0019] Scroll housing 20 is fabricated by welding the top portion
50 to the bottom portion 52. It is desired to provide a smooth
surface finish within the volute chamber 22 such that airflow is
not adversely affected by any inconsistencies within the surface
finish. Accordingly, an interface 58 between mating surfaces
defined on the top and bottom portions of the scroll housing 20
provides little interruption of the desired interior surface finish
of the volute chamber 22.
[0020] An outer wall 28 of the volute chamber 22 includes the inner
surface 30 and an outer surface 32. The inner surface and the outer
surface 32 are defined by the outer wall 28. A boss 34 is disposed
at the location of mating surfaces between the top and bottom
portions 50, 52 of the scroll housing 20. The boss 34 provides
additional material for the welded joint interface 58.
[0021] Referring to FIG. 4, with continued reference to FIG. 3, the
scroll housing 20 includes inner annular passage 24 open to an
inner periphery of the inner cavity 36 that defines the space
within which the impeller 38 rotates.
[0022] Referring to FIGS. 5 and 6, the top portion 50 and the
bottom portion 52 of the scroll housing 20 are formed from a
forging operation. An aluminum alloy material is utilized to
fabricate the example top and bottom portions 50, 52 of the example
scroll housing 20. Some aluminum alloys are not compatible with
lost mold casting procedures. In such non-compatible alloys,
differences in the melting temperature of the alloy components
cannot provide for homogenous distribution of elements in a lost
wax molding process and therefore result in undesirable
manufacturing inefficiencies.
[0023] The example scroll housing 20 is fabricated utilizing an
extruded aluminum material. The aluminum material is extruded as a
billet and shaped to a near complete configuration by a forging
operation. After the forging operation is complete, various
features are machined into each of the top and bottom portions 50,
52. Mating surfaces 54 and 56 are formed after forging to define
the weld joint and mating interface 58 between the top and bottom
portions 50, 52 of the scroll housing 20. Other surfaces are also
machined to provide the desired configuration of the completed
scroll housing 20 and include openings for a shaft bearing and also
the inner cavity 36 within which the impeller 38 rotates. Once the
desired machining operations are complete and provide the machine
surfaces within desired tolerances the top and bottom portions are
held together with the mating surfaces 54 and 56 in a desired
alignment.
[0024] Referring to FIG. 7, the now aligned top and bottom portions
50, 52 of the scroll housing 20 are welded utilizing an energy beam
welding method. In this example, an electron beam 62 is utilized
for forming the desired weld joint between the top and bottom
portions 50, 52. In this example, an electron beam welding machine
64 generates an electron beam 62 that is directed through the
passage 24 against the outer wall 28. The electron beam 62 is
guided or directed through the passage 24 against an inner surface
30 of the outer wall 28. The specific location that the electron
beam 62 is directed is the interface 58 between the mating surfaces
54 and 56.
[0025] The directed energy beam provides a weld joint 60 that
creates a substantially finished surface that does not affect the
desired airflow properties through the volute chamber 22. The weld
beam 62 is applied in a continuous manner about the circumference
of the volute chamber 22. This is accomplished by either rotating
the electron beam 62 such that it is directed through the passage
24 or by rotating the assembled top and bottom portions of the
scroll housing 20.
[0026] The electron beam 62 provides a weld joint 60 through the
entire thickness of the outer wall 28 to form the desired joint. On
an outer surface of the outer wall 28, a boss 34 is provided to
further accommodate the weld joint 60. Once the desired weld joint
is completed, the scroll compressor is finish machined to complete
fabrication of the scroll housing 20. As appreciated, although an
electron beam welding process is disclosed other beam welding
processes could also be utilized such as for example laser
welding.
[0027] Referring to FIG. 8, completed scroll housing 20 as
illustrated and includes all the features of a one piece housing
without the inefficiencies caused by the lost wax molding
manufacturing processes.
[0028] Accordingly, the example scroll housing for a load
compressor provides a desired surface finish within the volute
chambers without sacrificing manufacturing inefficiencies.
Moreover, the electron beam welding method allows for the precision
application of a weld joint within the volute chamber without
modification of the part configuration.
[0029] Although an example embodiment has been disclosed, a worker
of ordinary skill in this art would recognize that certain
modifications would come within the scope of this disclosure. For
that reason, the following claims should be studied to determine
the scope and content of this invention.
* * * * *