|Publication number||US20070036662 A1|
|Application number||US 11/499,265|
|Publication date||Feb 15, 2007|
|Filing date||Aug 4, 2006|
|Priority date||Aug 5, 2005|
|Publication number||11499265, 499265, US 2007/0036662 A1, US 2007/036662 A1, US 20070036662 A1, US 20070036662A1, US 2007036662 A1, US 2007036662A1, US-A1-20070036662, US-A1-2007036662, US2007/0036662A1, US2007/036662A1, US20070036662 A1, US20070036662A1, US2007036662 A1, US2007036662A1|
|Inventors||Fabio Pesola, Paolo Marchese, Dario Caenazzo|
|Original Assignee||C.R.F Societa Consortilla Per Azioni|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (13), Classifications (9), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims benefit under 35 U.S.C. §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.
1. Field of the Invention
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.
2. Description of Related Art
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.
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.
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.
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.
According to the disclosure, this object is achieved by a multistage motor-compressor for the compression of a fluid.
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.
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:
With reference to
The low-pressure stage 6 comprises a low-pressure impeller, which henceforth will be called the primary impeller 8 (
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.
According to the variant in
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.
The high-pressure stage 7 of the motor-compressor 5 comprises a high-pressure impeller, which henceforth will be called the secondary impeller 21 (
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.
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.
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
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.
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 (
The motor-compressor 5 also comprises a conveyor 39 with an outer wall 40 and a central opening 41 (
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 (
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.
The transfer ducts 44 are advantageously placed on the outside of the casing 32 and are each formed by two segments 46 and 47 (
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.
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.
In the illustrated embodiment, the two impellers 8 and 21 are coaxial and are driven by a single electric motor 15. In
According to the variant in
The functioning of the motor-compressor 5 is as follows.
By making the two impellers 8 and 21 rotate in the direction of the arrows 63 and 64 (
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.
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.
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|U.S. Classification||417/350, 417/423.5|
|Cooperative Classification||F04D29/441, F04D25/06, F04D17/12|
|European Classification||F04D25/06, F04D17/12, F04D29/44C|
|Oct 26, 2006||AS||Assignment|
Owner name: C.R.F. SOCIETA CONSORTILE PER AZIONI, ITALY
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:PESOLA, FABIO;MARCHESE, PAOLO;CAENAZZO, DARIO;REEL/FRAME:018461/0202
Effective date: 20061019