A portion of the disclosure of this patent document contains material that is subject to copyright protection. The applicant no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
This invention relates to a high efficiency, novel gas compressor in which saving of power as well as improved compression performance and durability are attained by the use of supersonic shock compression of process gas. Compressors of that character are particularly useful for compression of air, refrigerants, steam, and hydrocarbons.
A continuing demand exists for simple, highly efficient and inexpensive gas compressors as may be useful in a wide variety of gas compression applications. This is because many gas compression applications could substantially benefit from incorporating a compressor that offers a significant efficiency improvement over currently utilized designs. In view of increased energy costs, particularly for both for electricity and for natural gas, it would be desirable to attain significant cost reduction in gas compression. Importantly, it would be quite advantageous to provide a novel compressor which provided improvements (1) with respect to operating energy costs, (2) with respect to reduced first cost for the equipment, and (3) with respect to reduced maintenance costs. Fundamentally, particularly from the point of view of reducing long term energy costs, this would be most effectively accomplished by attaining gas compression at a higher overall cycle efficiency than is currently known or practiced industrially. Thus, the important advantages of a new gas compressor design providing the desirable features of improved efficiency, particularly at part load operation, can be readily appreciated.
We have now invented a gas compressor based on the use of a driven rotor having a compression ramp traveling at a local supersonic inlet velocity (based on the combination of inlet gas velocity and tangential speed of the ramp) which compresses inlet gas against a stationary sidewall. In using this method to compress inlet gas, the supersonic compressor efficiently achieves high compression ratios while utilizing a compact, stabilized gasdynamic flow path. Operated at supersonic speeds, the inlet stabilizes an oblique/normal shock system in the gasdyanamic flow path formed between the rim of the rotor, the strakes, and a stationary external housing.
Efficiency can be further enhanced by using a pre-swirl inlet compressor wheel prior to entry of gas to the supersonic compression ramp. Such pre-swirl inlet compression wheel (a) provides an initial pressure boost over incoming (often ambient atmospheric pressure, in the case of air compression) gas pressure, and (b) energizes inlet gas in a counter swirling direction to impart an initial velocity vector on the inlet gas so as to increase apparent mach number when the inlet gas is ingested by the supersonic compression ramp.
By use of a gas bypass valve arrangement, the low pressure compressed gas output (i.e., mass flow rate) from the pre-swirl compressor unit can be turned down as necessary while maintaining high rotating velocity (utilizing a fixed shaft speed, i.e., constant rotating velocity where necessary or desirable), such as is necessary when utilizing constant speed compressor drive apparatus, while maintaining minimal output loads. Moreover, this technique allows maintenance of relatively high efficiency compression with good turn down capability, since the supersonic compressor wheel continues to operate at an efficient high speed condition.
The structural and functional elements incorporated into this novel compressor design overcomes significant and serious problems which have plagued earlier attempts at supersonic compression of gases in industrial applications. First, at the Mach numbers at which my device operates (in the range from about Mach 1.5 or lower to about Mach 4.0), the design minimizes aerodynamic drag. This is accomplished by both careful design of the shock geometry, as related to the rotating compression ramp and the stationary wall, as well as by effective use of a boundary layer control and drag reduction technique. Thus, the design minimizes parasitic losses to the compression cycle due to the drag resulting simply from rotational movement of the rotor. This is important commercially because it enables a gas compressor to avoid large parasitic losses that undesirably consume energy and reduce overall efficiency.
Also, more fundamentally, this compressor design can develop high compression ratios with very few aerodynamic leading edges. The individual leading edges of the thousands of rotor and stator blades in a conventional high pressure ratio compressor, especially as utilized in the gas turbine industry, contribute to the vast majority of the viscous drag loss of such systems. However, in that the design of the novel gas compressor disclosed herein utilizes, in one embodiment, less than five individual aerodynamic leading edges subjected to stagnation pressure, viscous losses are significantly reduced, compared to conventional gas compression units heretofore known or utilized. As a result, the novel compressor disclosed and claimed herein has the potential to be up to ten percentage points more efficient than a conventional gas turbine compressor, when compared at competing compression ratios in the range from about ten to one (10:1) to about thirty to one (30:1).
Second, the selection of materials and the mechanical design of rotating components avoids use of excessive quantities or weights of materials (a vast improvement over large rotating mass bladed centrifugal compressor designs). Yet, the design provides the necessary strength, particularly tensile strength where needed in the rotor, commensurate with the centrifugal forces acting on the extremely high speed rotating components.
Third, the design provides for effective mechanical separation of the low pressure incoming gas from the exiting high pressure gases, while allowing gas compression operation along a circumferential pathway.
This novel design enables the use of lightweight components in the gas compression pathway. To solve the above mentioned problems, we have now developed compressor design(s) which overcome the problems inherent in the heretofore known apparatus and methods known to me which have been proposed for the application of supersonic gas compression in industrial applications. Of primary importance, we have now developed a low drag rotor which has one or more gas compression ramps mounted at the distal edge thereof. A number N of peripherally, preferably partially helically extending strakes S partition the entering gas flow sequentially to the inlet to a first one of the one or more gas compression ramps, and then to a second one of the one or more gas compression ramps, and so on to an Nth one of the one or more gas compression ramps. Each of the strakes S has an upstream or inlet side and a downstream or outlet side. For rotor balance and gas compression efficiency purposes, in one embodiment the number X of gas compression ramps R and the number of strakes N are the same positive integer number, and in such embodiment, N and X is at least equal to two. In an embodiment shown herein, the number of strakes N and the number X of gas compression ramps R are both equal to three. The compressed gases exiting from each of the one or more gas compression ramps is effectively prevented from “short circuiting” or returning to the inlet side of subsequent gas compression ramps by the strakes S. More fundamentally, the strakes S act as a large screw compressor fan or pump to move compressed gases along with each turn of the rotor.
To accommodate the specific strength requirements of high speed rotating service, various embodiments for an acceptable high strength rotor are feasible. In one embodiment, the rotor section may comprise a carbon fiber disc. In another, it may comprise a high strength steel hub. In each case, the gas compression ramps and strakes S may be integrally provided, or rim segments and gas compression modules may be releasably and replaceably affixed to the rotor.
Attached at the radial edge of the rotor are one or more of the at least one gas compression ramps. The gas compression ramps are situated so as to engage and to compress that portion of the entering gas stream which is impinged by the gas compression ramp upon its rotation, which in one embodiment, is about the aforementioned drive shaft. The compressed gases escape rearwardly from the gas compression ramp, and decelerate and expands outwardly into a gas expansion diffuser space or volute, prior to entering a compressed gas outlet nozzle.
Finally, many variations in the gas flow configuration and in provision of the inlet gas pre-swirl compression, and in providing outlet gas passageways, may be made by those skilled in the art without departing from the teachings hereof. Finally, in addition to the foregoing, my gas compressor is simple, durable, and relatively inexpensive to manufacture and to maintain.
In order to enable the reader to attain a more complete appreciation of the invention, and of the novel features and the advantages thereof, attention is directed to the following detailed description when considered in connection with the accompanying drawings, wherein:
The foregoing figures, being merely exemplary, contain various elements that may be present or omitted from actual implementations depending upon the circumstances. An attempt has been made to draw the figures in a way that illustrates at least those elements that are significant for an understanding of the various embodiments and aspects of the invention. However, various other elements of the supersonic gas compressor, especially as applied for different variations of the functional components illustrated, embodiments, may be utilized in order to provide a robust supersonic gas compression unit still within the overall teachings of the present invention, and the legal equivalents thereof.
Referring now to the drawing,
One or more helical strakes S are provided adjacent each one of the one or more supersonic compression ramps R. An outwardly extending wall portion Sw of each of the one or more strakes S extends outward from at least a portion of the outer surface portion 38 of its respective rotor 30 or 32 along a height HH (see
For rotor 30 or 32 balance purposes, we prefer that the number X of gas compression ramps R and the number N of strakes S be the same positive integer number, and that N and X each be at least equal to two. In one embodiment, N and X are equal to three as illustrated herein. The strakes S1 through SN allow feed of gas to each gas compression ramp R without appreciable bypass of the compressed high pressure gas to the entering low pressure gas. That is, the compressed gas is effectively prevented by the arrangement of strakes S from “short circuiting” and thus avoids appreciable efficiency losses. This strake feature can be better appreciated by evaluating the details shown in
As seen in
For improving efficiency, each of the one or more gas compression ramps R has one or more boundary layer bleed ports B. In the configuration illustrated in
As depicted in
For improved efficiency and operational flexibility, the compressor 20 may be designed to further include a first inlet casing 100 and a second inlet casing 102 having therein, respectively, first 104 and second 106 pre-swirl impellers. These pre-swirl impellers 104 and 106 are located intermediate the low pressure gas inlets 24 and 26, and their respective first 30 or second 32 rotors. Each of the pre-swirl impellers 104 and 106 are configured for compressing the low pressure inlet gas LP to provide an intermediate pressure gas stream P at a pressure intermediate the pressure of the low pressure inlet gas LP and the high pressure outlet gas HP, as noted in
Also, for improving efficiency, the gas compressor 20 can be provided in a configuration wherein, downstream of the pre-swirl impellers 104 and 106, but upstream of the one or more gas compression ramps R on the respective rotors 30 and 32, a plurality of inlet guide vanes, are provided, a first set 110 or 110′ before first rotor 30 and a second set 112 or 112′ before second rotor 32. The inlet guide vanes 110′ and 112′ as illustrated in
In one embodiment, as illustrated, the pre-swirl impellers 104 and 106 can be provided in the form of a centrifugal compressor wheel. As illustrated in
In
With (or without) the aid of pre-swirl impellers 104 and 106, it is important that the apparent velocity of gas entering the one or more gas compression ramps R is in excess of Mach 1, so that the efficiency of supersonic shock compression can be exploited. However, to increase efficiency, it would be desirable that the apparent velocity of gas entering the one or more gas compression ramps R be in excess of Mach 2. More broadly, the apparent velocity of gas entering the one or more gas compression ramps R can currently practically be between about Mach 1.5 and Mach 3.5,although wider ranges are certainly possible within the teachings hereof.
As depicted in
The compressor 20 provides an ideal apparatus for the compression of various gases, including (a) air, (b) refrigerant, (c) steam, and (d) hydrocarbons. In various applications, it has been calculated that compressor 20 is capable of providing compression of a selected gas at an isentropic efficiency in excess of ninety (90) percent, as is graphically illustrated in
For assuring operation at high rotational speed, to achieve high apparent Mach number at the inlet of each of the one or more gas compression ramps R, a high strength rotor 30 or 32 is provided. In one embodiment, such rotors include a high strength central disc. As illustrated in
The compressor 20 disclosed herein allows practice of unique methods of compressing gases. Practice of such methods involves providing one or more gas compression ramps on a rotor which is rotatably secured for high speed rotary motion with respect to stationary housing having an inner surface. Each of the one or more gas compression ramps is provided with an inlet, low pressure gas stream. The low pressure gas is compressed between one of the one or more gas compression ramps and the inner surface of the stationary housing which is located circumferentially about the rotor, to generate a high pressure gas therefrom. To achieve gas compression, and to avoid bypass of the compressed gas back to the entering low pressure gas stream, one or more helical, substantially radially extending strakes are provided along the periphery of the rotor. Each on of the one or more strakes S is provided adjacent to one of the one or more gas compression ramps R. At least a portion of each of the one or more strakes S extends outward from at least a portion of an outer surface portion of the rotor to a point adjacent to the inner surface of the stationary housing. The rotor is driven by application of mechanical power to an input shaft operatively connected to the rotor, and thus to each of the one or more gas compression ramps. In one embodiment, the apparent inlet velocity of the one or more gas compression ramps, i.e., the approach speed between incoming gas and the opposing motion of a selected gas compression ramp R, is at least Mach 1.5. More broadly, the apparent inlet velocity of the one or more gas compression ramps is between Mach 1.5 and Mach 4. At the design point in one embodiment, the apparent inlet velocity of said gas compression ramps is approximately Mach 3.5.
This method of gas compression allows high efficiency compression of a variety of commonly compressed gases, including (a) air, (b) steam, (c) refrigerant, and (d) hydrocarbons. Some important applications include compression of air, natural gas, refrigerants in refrigeration and air conditioning, applications, and steam in various services.
Overall, the designs incorporated into compressor 20 provide for minimizing aerodynamic drag, by minimizing the number of leading edge surfaces subjected to stagnation pressure within the compressor. In one embodiment, as illustrated herein, the number of leading edge surfaces subjected to stagnation pressure is less than five. And, each of the one or more gas compression ramps are circumferentially spaced equally apart so as to engage a supplied gas stream substantially free of turbulence from the previous passage through a given circumferential location of any one said one or more gas compression ramps. The cross sectional areas of each of the one or more gas compression ramps can be sized and shaped to provide a desired compression ratio. Further, the helical strakes can be offset at a preselected angle delta, and wherein the angle of offset matches the angle of offset of each one of the one or more gas compression ramps, and wherein so that the angles match to allow gas entering the one or more gas compression ramps to be at approximately the same angle as the angle of offset, to minimize inlet losses.
The rotors 30 and 32 are rotatably secured in an operating position by a fixed support stationary housing or casing 22 in a manner suitable for extremely high speed operation of the rotors 30 and 32, such as rotation rates in the range of 10,000 to 20,000 rpm, or even up to 55,000 rpm, or higher. In this regard, bearing assemblies must provide adequate bearing support for high speed rotation and thrust, with minimum friction, while also sealing the operating cavity, so as to enable provision of a vacuum environment adjacent the rotor disc, to minimize drag. The detailed bearing and lubrication systems may be provided by any convenient means by those knowledgeable in high speed rotating machinery, and need not be further discussed herein. However, note that in the embodiment shown in
It is to be appreciated that the various aspects and embodiments of a supersonic gas compressor, and the method of operating such devices as described herein are an important improvement in the state of the art. The novel supersonic gas compressor is simple, robust, reliable, and useful for work in various gas compression applications. Although only a few exemplary embodiments have been described in detail, various details are sufficiently set forth in the drawings and in the specification provided herein to enable one of ordinary skill in the art to make and use the invention(s), which need not be further described by additional writing in this detailed description.
Importantly, the aspects and embodiments described and claimed herein may be modified from those shown without materially departing from the novel teachings and advantages provided by this invention, and may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Therefore, the embodiments presented herein are to be considered in all respects as illustrative and not restrictive. As such, this disclosure is intended to cover the structures described herein and not only structural equivalents thereof, but also equivalent structures. Numerous modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention(s) may be practiced otherwise than as specifically described herein. Thus, the scope of the invention(s), as set forth in the appended claims, and as indicated by the drawing and by the foregoing description, is intended to include variations from the embodiments provided which are nevertheless described by the broad interpretation and range properly afforded to the plain meaning of the claims set forth below.
This application is a Continuation-In-Part of prior U.S. patent application Ser. No. 10/672,719, filed Sep. 25, 2003 now abandoned, entitled SUPERSONIC GAS COMPRESSOR, (assigned of record on Apr. 22, 2004 and May 3, 2004 and recorded on May 11, 2004 at Reel/Frame 015313/0771 to Ramgen Power Systems, Inc. of Bellevue, Wash.), which utility application claimed priority from prior U.S. Provisional Patent Application Ser. No. 60/414,793, filed on Sep. 26, 2002, the disclosures of which are incorporated herein in their entirety by this reference, including the specification, drawings, and claims of each application.
This invention was made with United States Government support under Contract No. DE-FC026-00NT40915 awarded by the United States Department of Energy. The U.S. Government has certain rights in the invention.
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Number | Date | Country | |
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Parent | 10672719 | Sep 2003 | US |
Child | 11087336 | US |