U.S. patent application number 11/499265 was filed with the patent office on 2007-02-15 for multistage motor-compressor for the compression of a fluid.
This patent application is currently assigned to C.R.F Societa Consortilla per Azioni. Invention is credited to Dario Caenazzo, Paolo Marchese, Fabio Pesola.
Application Number | 20070036662 11/499265 |
Document ID | / |
Family ID | 37742711 |
Filed Date | 2007-02-15 |
United States Patent
Application |
20070036662 |
Kind Code |
A1 |
Pesola; Fabio ; et
al. |
February 15, 2007 |
Multistage motor-compressor for the compression of a fluid
Abstract
A motor-compressor is provided that includes a first compression
stage with a primary impeller and at least one delivery duct, a
second compression stage with a secondary impeller spinning in a
predetermined direction of rotation, and at least one transfer duct
placed so as to put the delivery duct in communication with a fluid
conveyor for the second stage. The transfer duct is shaped in a way
to create a fluid flow entering the conveyor with a substantially
helical course and a direction of rotation opposite to the
direction of rotation of the secondary impeller.
Inventors: |
Pesola; Fabio; (Orbassano,
IT) ; Marchese; Paolo; (Orbassano, IT) ;
Caenazzo; Dario; (Orbassano, IT) |
Correspondence
Address: |
Charles N.J. Ruggiero;Ohlandt, Greeley, Ruggiero & Perle, L.L.P.
10th Floor
One Landmark Square
Stamford
CT
06901-2682
US
|
Assignee: |
C.R.F Societa Consortilla per
Azioni
|
Family ID: |
37742711 |
Appl. No.: |
11/499265 |
Filed: |
August 4, 2006 |
Current U.S.
Class: |
417/350 ;
417/423.5 |
Current CPC
Class: |
F04D 17/12 20130101;
F04D 25/06 20130101; F04D 29/441 20130101 |
Class at
Publication: |
417/350 ;
417/423.5 |
International
Class: |
F04B 17/00 20060101
F04B017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 5, 2005 |
IT |
TO2005A 000558 |
Feb 10, 2006 |
EP |
06101557.4 |
Claims
1. A multistage motor-compressor for compression of a fluid,
comprising: a first compression stage having a primary impeller and
at least one delivery duct, a second compression stage having a
secondary impeller spinning in a first direction of rotation and a
fluid conveyor, and at least one transfer duct placing said at
least one delivery duct in communication with said fluid conveyor,
said at least one transfer duct being shaped in a way to create a
fluid flow entering said fluid conveyor with a substantially
helical course and with a direction of rotation opposite to said
first direction of rotation.
2. The motor-compressor according to claim 1, wherein said second
compression stage comprises at least one axial inlet duct for said
fluid flow, said fluid conveyor having an inlet opening for said
fluid flow, said inlet opening being in communication with said at
least one transfer duct and with said at least one axial inlet
duct.
3. The motor-compressor according to claim 2, wherein said at least
one delivery duct comprises a pair of diametrically opposed
delivery ducts, said fluid conveyor comprising a pair of
diametrically opposed inlet openings, each inlet opening of said
pair of inlet openings being in communication with a respective
delivery duct of said pair of delivery ducts via a separate
transfer duct.
4. The motor-compressor according to claim 2, wherein said at least
one delivery duct comprises three delivery ducts set at 120.degree.
to each other, said fluid conveyor comprising three inlet openings
set at 120.degree. to each other, each inlet opening of said three
inlet openings being in communication with a respective delivery
duct of said three delivery ducts via a separate transfer duct.
5. The motor-compressor according to claim 3, wherein said primary
and secondary impellers are driven by a driving device inside a
casing, said separate transfer ducts being placed on an outside of
said casing.
6. The motor-compressor according to claim 3, wherein each of said
separate transfer ducts comprises: a first section connected to
said respective delivery duct and substantially tangential to said
primary impeller, a second section connected to said fluid conveyor
and substantially tangential to said secondary impeller, and a
longitudinal intermediate section.
7. The motor-compressor according to claim 6, wherein each of said
separate transfer ducts further comprises a substantially helical
section placed between said first tangential section and said
intermediate section, and a curved section placed between said
second tangential section and said intermediate section.
8. The motor-compressor according to claim 7, wherein each of said
separate transfer ducts is subdivided into two segments, each
segment of said two segments comprising a portion of said
intermediate section and a flange for connection with the other
segment of said two segments.
9. The motor-compressor according to claim 3, wherein said separate
transfer ducts are each shaped in a way to create said fluid flow
exiting from said delivery ducts with a substantially helical
course and with a third direction of rotation concordant with a
direction of rotation of said primary impeller.
10. The motor-compressor according to claim 5, wherein said driving
device comprise a first electric motor for driving said primary
impeller and a second electric motor for driving said secondary
impeller.
11. The motor-compressor according to one of the claims 5, wherein
said driving device comprises a common electric motor for said
primary and secondary impellers.
12. The motor-compressor according to claim 11, wherein said
primary and secondary impellers are coaxial.
13. The motor-compressor according to claim 12, wherein said
primary and secondary impellers are fixed on two opposite ends of a
shaft of said common electric motor.
14. The motor-compressor according to claim 11, wherein said
primary and secondary impellers spin around two axes that are
coplanar and which form a predetermined angle.
15. The motor-compressor according to claim 11, further comprising
a drive transmission group placed between said common electric
motor and said primary impeller and/or said secondary impeller.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit under 35 U.S.C. .sctn.119(a)
of Italian Patent Application No. T)2005A 000558, filed Aug. 5,
2005 and European Patent Application No. 06101557.4, filed Feb. 10,
2006, the entire contents of both of which are incorporated herein
by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This disclosure refers to a multistage motor-compressor for
the compression of a fluid, for motor vehicles for example. In
particular, the disclosure refers to a two-stage motor-compressor
for the supply of pressurized air to fuel cell systems.
[0004] 2. Description of Related Art
[0005] Motor-compressors of the above-stated type are well known,
in which the first-stage scroll is connected to a tangential first
section of a transfer duct, while a second axial or radial section
of the transfer duct is connected to a fluid conveyor for the
second-stage scroll. In the case where the second section is axial,
the fluid flow entering the conveyor undergoes abrupt changes of
direction, giving rise to a drop in flow pressure, high operational
power consumption and reduced efficiency for the
motor-compressor.
[0006] In the case in which the second section of the transfer duct
is radial, it is normally shaped to create a helical flow with the
same direction of rotation as that of the second-stage impeller.
This radial connection has the drawback of reduced efficiency and a
low compression ratio at high flow rates.
[0007] Multistage motor-compressors are also known, in which the
impellers are arranged in series on the same output side of the
driving electric motor's shaft. Since the two impellers are
cantilever mounted on the shaft, the latter is subject to stress,
which reduces the operating speed.
BRIEF SUMMARY OF THE INVENTION
[0008] The object of the disclosure is that of embodying a
two-stage motor-compressor, which is highly reliable, eliminating
the drawbacks and increasing the performance of motor-compressors
of known art.
[0009] According to the disclosure, this object is achieved by a
multistage motor-compressor for the compression of a fluid.
[0010] According to a variant of the disclosure, the impellers of
the two stages are fixed on two opposite ends of the shaft of a
common driving electric motor, for which the motor-compressor is
able to operate at high speeds.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0011] For a better understanding of the disclosure, a preferred
embodiment is described herein, provided by way of example with the
aid of the enclosed drawings, in which:
[0012] FIG. 1 is a right-hand perspective view of a two-stage
motor-compressor according to a first variant of the
disclosure,
[0013] FIG. 2 is a left-hand perspective view of the
motor-compressor in FIG. 1,
[0014] FIG. 3 is a diametrical section of the motor-compressor in
FIG. 1,
[0015] FIG. 4 is a view along line IV-IV in FIG. 3,
[0016] FIG. 5 is a view along line V-V in FIG. 3,
[0017] FIG. 6 is a left-hand perspective view of part of the
motor-compressor in FIG. 1,
[0018] FIG. 7 is a left-hand perspective view of another part of
the motor-compressor in FIG. 1,
[0019] FIG. 8 is a right-hand perspective view of a further part of
the motor-compressor in FIG. 1,
[0020] FIGS. 9 and 10 are two due perspective views similar to that
in FIG. 2, regarding two variants of the motor-compressor, and
[0021] FIG. 11 is a graph of the motor-compressor's compression
ratio.
DETAILED DESCRIPTION OF THE INVENTION
[0022] With reference to FIGS. 1 and 2, reference 5 generically
indicates a multistage motor-compressor for the compression of a
fluid, for motor vehicles for example. In particular, the
motor-compressor 5 is of the type with two stages 6 and 7, low
pressure and high pressure respectively, and is suitable for the
supply of pressurized air in a fuel cell system or for supplying
air to internal combustion engines, or for any system in which
compressed air is required.
[0023] The low-pressure stage 6 comprises a low-pressure impeller,
which henceforth will be called the primary impeller 8 (FIG. 3).
The primary impeller 8 rotates around an axis A and is preceded by
a fixed ogival portion 9, placed inside a low-pressure scroll,
which henceforth will be called the primary scroll 10. The primary
impeller 8 is fixed on one end 15' of a shaft of an electric motor
15. The primary impeller 8 also comprises a series of substantially
radial, shaped blades 11, of known type.
[0024] The primary scroll 10 is composed of a shaped casing 12,
connected in a removable manner, via bolts and at least one
half-ring 13, to a fixed plate 20 carried on an external casing 32
of the motor 15, which has a substantially cylindrical shape. The
shaped casing 12 has a central air-inlet opening 14 to the
low-pressure stage 6. The primary scroll 10 also has at least one
curved, fluid-delivery duct 16, which has a substantially spiral
shape placed substantially on plane P perpendicular to axis A.
[0025] According to the variant in FIGS. 1-8, the primary scroll 10
is equipped with three curved ducts 16 arranged at 120.degree. to
each other, for the purpose of having a balanced load on the
primary scroll 10. The fixed plate 20 of the motor 15, together
with the shaped casing 12 of the primary scroll 10, form an annular
chamber 17 in communication with the curved ducts 16. On one side,
the annular chamber 17 is in communication with the central opening
14, through an annular inlet opening 18 facing towards axis A,
while on the other side it is in communication with the curved
ducts 16 through corresponding outlet openings 19, facing towards
the outside of the annular chamber 17.
[0026] The shaped blades 11 of the impeller 8 are suitable for
conveying incoming air from the central opening 14 to the curved
ducts 16. The axial direction of the airflow to be compressed is
optimized by the ogival portion 9. In order to convey compressed
air from the impeller 8, each curved duct 16 has an increasing
section from the outlet opening 19 of the annular chamber 17 to the
outlet opening 25, which is defined by the terminal radial section
of the curved duct 16. The spiral shape of the curved duct 16
induces a fluid flow that turns in the same direction of rotation
as the impeller 8.
[0027] The high-pressure stage 7 of the motor-compressor 5
comprises a high-pressure impeller, which henceforth will be called
the secondary impeller 21 (FIG. 3), rotating around its axis. This
axis can advantageously coincide with axis A of the primary
impeller 8. The secondary impeller 21 is fixed on the end 15'' of
the shaft of the motor 15 opposite from that of the primary
impeller 8, thereby providing a balanced load on the shaft of the
motor 15 such that the group of impellers 8 and 21 can be spun at
high speed.
[0028] The secondary impeller 21 is equipped with its own ogival
portion 22, suitable for optimizing the direction of the axial
flow. The ogival portion 22 is placed inside a high-pressure
scroll, which henceforth will be called the secondary scroll 23.
The secondary impeller 21 also comprises a series of substantially
radial, shaped blades 24.
[0029] The secondary scroll 23 is composed of a shaped casing 26
connected in a removable manner, via bolts and at least one
half-ring 27, to another fixed plate 33, carried on the external
casing 32 of the motor 15. The shaped casing 26 of the secondary
scroll 23 has a sleeve 31 with a central air-inlet opening 28 to
the high-pressure stage 7.
[0030] In addition, the secondary scroll 23 has at least one curved
duct 29, substantially placed on another plane R perpendicular to
axis A. The secondary scroll 23 (see also FIG. 7) advantageously
has just one curved duct 29, which also has a substantially spiral
course and terminates with a straight section 30. The spiral of the
curved duct 29 is such as to generate a fluid flow that also turns
in the same direction as the secondary impeller 21.
[0031] The fixed plate 33 together with the shaped casing 26 forms
an annular chamber 34, one side of which is in communication with
the central opening 28, through an annular inlet opening 36 facing
towards axis A. On the other side, the annular chamber 34 is in
communication with the curved duct 29, through an opening 37 facing
towards the outside, which forms the inlet opening of the curved
duct 29. The shaped blades 24 of the impeller 21 are suitable for
conveying incoming air from the central opening 28 to the annular
chamber 34.
[0032] In order to convey compressed air entering through the
central opening 28 in the annular chamber 34, the curved duct 29
has an increasing section from the portion adjacent to its inlet
opening 37 to a corresponding outlet opening 38 (FIG. 5) defined by
the terminal radial section of the curved duct 29, which is equal
to that of the straight section 30.
[0033] The motor-compressor 5 also comprises a conveyor 39 with an
outer wall 40 and a central opening 41 (FIG. 3), in which the
sleeve 31 of the secondary scroll 23 engages in a sealed manner.
The conveyor 39 is also provided with three inlet openings 42
associated with the three outlet openings 25 of the curved ducts 16
of the primary scroll 10. The three inlet openings 42 are also
arranged at 120.degree. to each other. A corresponding transfer
duct, generically indicated by reference 44, is placed between each
outlet opening 25 of the primary scroll 10 and the corresponding
inlet opening 42 of the conveyor 39.
[0034] According to the disclosure, each transfer duct 44 is shaped
so as to create a flow entering the conveyor 39 with a
substantially helical course and a direction of rotation opposite
to the direction of rotation of the secondary impeller 21. In
particular, each transfer duct 44 comprises a first section 52
(FIGS. 1, 4 and 6) connected to the corresponding curved duct 16
and substantially tangential to the primary impeller 8, a second
section 56 (FIGS. 2, 5 and 8) connected to the corresponding
opening 42 of the conveyor 39 and substantially tangential to the
secondary impeller 21, and a longitudinal intermediate section 54
and 57.
[0035] The second tangential section 56 of the transfer duct 44 and
the corresponding opening 42 of the conveyor 39 are positioned in a
manner to generate the said helical course of the flow, with an
opposite direction of rotation to that of the impeller 21.
Furthermore, each transfer duct 44 comprises a first connector
section 53, substantially helical in form and placed between the
first tangential section 52 and the intermediate section 54 and 57.
Each transfer duct also comprises a second curved connector section
58 placed between the second tangential section 56 and the
intermediate section 54 and 57.
[0036] The transfer ducts 44 are advantageously placed on the
outside of the casing 32 and are each formed by two segments 46 and
47 (FIGS. 1 and 2), connected in a removable manner to the primary
scroll 10 and the conveyor 39 respectively. The two segments 46 and
47 terminate with corresponding flanges 48 and 49, which mate
together on a plane S (FIG. 3) perpendicular to axis A, and are
connected to each other in a sealed and removable manner, for
example by bolts 51.
[0037] The segment 46 of each transfer duct 44 comprises the said
first section 52, the corresponding substantially helical
connection section 53, and a straight portion 54, which forms a
portion 54 of the intermediate section 54 and 57. In turn, the
segment 47 of each transfer duct 44 comprises the said second
section 56, the curved connection section 58 and another straight
portion 57 of the intermediate section 54 and 57.
[0038] All of the ducts 16, 29 and 44 of the motor-compressor 5 are
outwardly sealed to support the pressurized fluid, via toroidal
gaskets for example, pastes or in any other known manner. The
shaped casing 12 of the primary scroll 10 is provided with a series
of cooling ribs or fins 59. Similarly, the shaped casing 26 of the
secondary scroll 23 and the conveyor 39 are provided with
corresponding series of cooling ribs or fins 61 and 62. The fins
59, 61 and 62 serve to increase the heat-exchange surface area with
the external environment, to cool the compressed fluid efficiently,
increasing the density and therefore increasing the efficiency of
the motor-compressor 5. The transfer ducts 44 have an elliptic
section to contain the radial bulk of the motor-compressor 5.
[0039] In the illustrated embodiment, the two impellers 8 and 21
are coaxial and are driven by a single electric motor 15. In FIGS.
4 and 5, the arrows 63 and 64 represent the direction of rotation
of the motor 15, while the black arrows on the transfer ducts 44
represent the flow of fluid. FIG. 4 clearly shows that the
direction of rotation of the flow in the segments 46 is consistent
with that of the motor 15 (arrow 63), while FIG. 5 shows that the
direction of rotation of the flow in the sections 57 of the
segments 47 is opposite to that of the motor 15 (arrow 64).
[0040] According to the variant in FIG. 9, the motor-compressor 5
comprises just one delivery duct 16 and just one transfer duct 44
to the conveyor 39. According to the variant in FIG. 10, the
motor-compressor 5 comprises two delivery ducts 16 and two transfer
ducts 44, placed diametrically opposite each other. Thus, the two
variants have a number of outlets 25 for the scroll 10 and inlets
42 to the conveyor 39 equal to the number of transfer ducts 44. The
shape of the transfer ducts 44 in FIGS. 9 and 10 is identical to
that of the transfer ducts 44 in FIG. 2. In FIGS. 9 and 10 parts
that are the same or similar to those in FIG. 2 are indicated with
the same reference numbers, and so the two variants will not be
described any further.
[0041] FIG. 11 shows a curve 66 of the compression ratio
.quadrature. as a function of flow Q of the motor-compressor 5. In
the case of transfer ducts 44 able to generate a helical flow that
is totally consistent with the rotation of the motor 15, a
predetermined compression curve 66 is obtained. If instead the
second section 56 of each transfer duct 44 provokes an opposite
helical flow to that of the motor 15, the outcome is a displacement
of the curve 66 to the right in FIG. 11, which indicates that a
greater compression ratio is achieved at high flow-rates.
[0042] The functioning of the motor-compressor 5 is as follows.
[0043] By making the two impellers 8 and 21 rotate in the direction
of the arrows 63 and 64 (FIGS. 4 and 5), the fluid entering from
the central opening 14 of the casing 12 (see also FIG. 3) is
propelled by the blades 11 into the curved ducts 16 of the scroll
10, undergoing a first compression. Exiting from the outlet
openings 25 of the curved ducts 16, the fluid flow, indicated in
FIGS. 3-5 by black arrows on the various ducts, is channelled into
the transfer ducts 44 and is introduced, through the inlet openings
42, into the conveyor 39 with a helical motion that turns in the
opposite direction to the direction of rotation of the motor 15.
The conveyor 39 then channels the fluid flow, via the central
opening 28 of the sleeve 31, to the inlet opening 37 of the
secondary scroll 23, where it undergoes a second compression
imparted by the secondary impeller 21 and then passes into the
curved duct 29 of the secondary scroll 23. Finally, the pressurized
fluid is conveyed to where utilized by the straight section 30.
[0044] From what has been seen above, the advantages of the
motor-compressor 5 according to the disclosure with respect to
motor-compressors of known art are evident. In particular, the
transfer ducts 44 avoid energy loss in the flow and improve the
efficiency of the motor-compressor 5. Furthermore, the fixing of
the two impellers 8 and 21 on the two ends 15' and 15'' of the
shaft of the common motor 15 renders operation of the impellers 8
and 21 well balanced, avoiding the generation of vibration and
thereby allowing an increase in the speed of rotation.
[0045] It is intended that various modifications and refinements
can be made to the above-described motor-compressor 5 without
departing from the scope of the claims. For example, each transfer
duct 44 could be in a single piece, and be connected to the scroll
10 and to the conveyor 39 in a removable manner, via a bolted
flange for example. In addition, the two impellers 8 and 21 could
be spun by independent electric motors and the respective axes A
could be parallel, oblique or coplanar, but with a predetermined
angle formed between them. In this case as well, the two impellers
8 and 21 are preferably rotated by a common electric motor,
possibly via at least one drive transmission group, of known
type.
* * * * *