The present invention relates generally to continuous axial flow compressors and, more particularly, to axial flow positive displacement compressors and worm and screw compressors.
Compressors are widely used in many applications such as in gas generators in gas turbine engines. Continuous axial flow compressors are utilized in a wide range of applications owing to a combination of desirable attributes such as high mass flow rate for a given frontal area, continuous near steady fluid flow, reasonable adiabatic efficiency, and the ability to operate free from aerodynamic stall and aeromechanical instability over a wide range of conditions. It is a goal of compressor and gas turbine manufacturers to have light-weight, compact, and highly efficient axial flow compressors. It is another goal to have as few parts as possible in the compressor to reduce the costs of manufacturing, installing, refurbishing, overhauling, and replacing the compressor. Therefore, it is desirable to have a compressor that improves on all of these characteristics.
A continuous axial flow positive displacement compressor also referred to as a worm compressor includes an inlet axially spaced apart and upstream from an outlet. The worm compressor includes a compressor assembly including inner and outer bodies extending from the inlet to the outlet. The inner and outer bodies have offset inner and outer axes, respectively. The compressor assembly has first and second sections in serial downstream flow relationship. Either or both bodies may be rotatable. In one embodiment of the compressor, the inner body is rotatable about the inner axis within the outer body. The outer body may be rotatably fixed or rotatable about the outer axis. The inner and outer bodies have intermeshed inner and outer helical blades wound about inner and outer axes, respectively. The inner and outer helical blades extend radially outwardly and inwardly, respectively.
The helical blades have first and second twist slopes in the first and second sections of the compressor assembly, respectively. A twist slope is defined as the amount of rotation of a cross-section of the helical element per unit distance along an axis. The first twist slopes are less than the second twist slopes. The helical blades in the first section have a sufficient number of turns to trap charges of gas in the first section during the compressor's operation. In one embodiment of the compressor, the number of turns is sufficient to mechanically trap the charges of gas. In another embodiment of the compressor, the number of turns is sufficient to dynamically trap the charges of gas. The helical blades in the second section have a sufficient number of turns to ensure that the leading edge of the charge is not exposed to the conditions downstream of the compressor until the trailing edge of the charge has crossed the compression plane, thereby completing the compression process.
Illustrated in
The core engine 118 includes in downstream serial flow relationship the worm compressor 8, a combustor 7, and a high pressure turbine 9 (HPT) having high pressure turbine blades 11 drivingly connected to the worm compressor 8 by a high pressure shaft 5. Combustion gases are discharged from the core engine 118 into a low pressure turbine (LPT) 120 having low pressure turbine rotor blades 122. The low pressure turbine rotor blades 122 are drivingly attached to a row of circumferentially spaced apart fan rotor blades 130 of the fan 108 in the fan section 112 by a low pressure shaft 132 to form a low pressure spool 134 circumscribing an engine centerline 136. The worm compressor 8 may be used in other applications including, but not limited to, ground based industrial and marine gas turbine engines.
Referring to
Either or both bodies may be rotatable and, if both bodies are rotatable, they rotate in the same circumferential direction, i.e. either clockwise or counterclockwise, but at different rotational speeds determined by a fixed relationship. If only one body is rotatable, then the other body is fixed. In one embodiment of the generator, the inner body 12 is rotatable about the inner axis 16 within the outer body 14 and the outer body 14 may be rotatably fixed or rotatable about the outer axis 18.
The inner and outer bodies 12, 14 have intermeshed inner and outer helical elements wound about the inner and outer axes 16, 18, respectively. The elements are inner and outer helical blades 17, 27 having inner and outer helical surfaces 21, 23, respectively. The inner helical blades 17 extend radially outwardly from a hollow inner hub 51 of the inner body 12 and the outer helical blades 27 extend radially inwardly from an outer shell 53 of the outer body 14. An inner helical edge 47 along the inner helical blade 17 sealingly engages the outer helical surface 23 of the outer helical blade 27 as they rotate relative to each other. An outer helical edge 48 along the outer helical blade 27 sealingly engages the inner helical surface 21 of the inner helical blade 17 as they rotate relative to each other.
Illustrated in
An alternative configuration of the inner and outer bodies 12, 14 is illustrated in cross-section in
Referring to
The twist slope A of the inner element in each of the sections is different from the twist slope A of the outer element. The ratio of the twist slope A of the outer body 14 to the twist slope A of the inner body 12 is equal to the ratio of the number of inner helical blades 17 blades on the inner body 12 to the number of outer helical blades 27 on the outer body 14. The first twist slopes 34 in the first section 24 are less than the second twist slopes 36 in the second section 26. The helical elements may also be described in terms of helical angle. The helical elements have constant first and second helical angles corresponding to the constant first and second twist slopes 34, 36, in the first and second sections 24, 26, respectively.
Referring again to
For the fixed outer body 14 embodiment, the inner body 12 is cranked relative to the outer axis 18 so that as it rotates about the inner axis 16, the inner axis 16 orbits about the outer axis 18 as illustrated in
The inner body 12 rotates about the inner axis 16 with an inner body rotational speed 74 equal to its orbital speed 76 divided by the number of inner body lobes. The number of inner lobes are equal the number of blades. If the inner body 12 rotates in the same direction as its orbital direction, a 2 lobed outer body configuration is used. If the inner body 12 rotates in an opposite orbital direction, a 4 lobed outer body configuration is used. In a first embodiment the inner and outer bodies 12, 14 are both rotatable and the outer body 14 rotates about the outer axis 18 at 1.5 times the rotational speed that the inner body 12 rotates about the inner axis 16. The outer body 14 rotates at a speed equal to the rotational speed of the inner body 12 times the number of lobes on the inner body divided by the number of lobes on the outer body 14.
The twist slopes of the outer body 14 are equal to the twist slopes of the inner body 12 times the number of inner body lobes N divided by the number of outer body lobes M. For the configuration illustrated in
The continuous axial flow positive displacement compressor, referred to herein as a worm compressor 8, may be used in a wide range of applications and provides high mass flow rate for a given frontal area, continuous near steady fluid flow, and reasonable efficiency over a wide range of operating conditions. It is light-weight and highly efficient and has far fewer parts as compared to other axial compressors which in turn reduces the costs of manufacturing, installing, refurbishing, overhauling, and replacing the compressor. The first embodiment provides a first mode of the compressor's operation disclosed herein in which the inner and outer bodies 12, 14 both rotate about the inner and outer axes 16, 18, respectively. The first mode avoids introducing a centrifugal rotor whirl effect on a support of the compressor and core engine. In a second embodiment the outer body 14 remains static and the inner body 12 simultaneously orbits the outer body's geometric center which is the outer axis 18 and spins about the instantaneous inner body's geometric center which is the inner axis 16. The second embodiment provides a second mode of the compressor's operation disclosed in which there is only a single rotor rotating potentially simplifying the mechanical design process.
The continuous axial flow positive displacement compressor, referred to herein as a worm compressor 8, may be used in a wide range of applications and provides reasonably high mass flow rate for a given frontal area, continuous near steady fluid flow, and is expected to provide reasonable efficiency over a wide range of operating conditions. Because the worm compressor operates in a positive displacement mode, it will provide compression levels that are nearly independent of rotor speed over a wide operating range. In thermal engines and other applications, this feature provides a distinct advantage over conventional axial flow compressors, for which compression ratios are directly related to rotor speed. Positive displacement operation also reduces or eliminates aerodynamic stall effects which allows the compressor to be run off-design at compression ratios well above a conventional stall line with the only ill effect being degradation of adiabatic efficiency. The worm compressor is expected to be light-weight, highly efficient, and have far fewer parts than conventional axial compressors which in turn reduces the costs of manufacturing, installing, refurbishing, overhauling, and replacing the compressor.
While there have been described herein what are considered to be preferred and exemplary embodiments of the present invention, other modifications of the invention shall be apparent to those skilled in the art from the teachings herein and, it is therefore, desired to be secured in the appended claims all such modifications as fall within the true spirit and scope of the invention. Accordingly, what is desired to be secured by Letters Patent of the United States is the invention as defined and differentiated in the following claims.
The Government has rights to this invention pursuant to Contract No. NAS3-01135 awarded by the NASA.
Number | Name | Date | Kind |
---|---|---|---|
1892217 | Moineau | Dec 1932 | A |
2553548 | Canazzi et al. | May 1951 | A |
2615436 | Pawl | Oct 1952 | A |
3938915 | Olofsson | Feb 1976 | A |
4144001 | Streicher | Mar 1979 | A |
4179250 | Patel | Dec 1979 | A |
RE30400 | Zimmern | Sep 1980 | E |
4482305 | Natkai et al. | Nov 1984 | A |
4500259 | Schumacher | Feb 1985 | A |
4802827 | Fujiwara et al. | Feb 1989 | A |
4818197 | Mueller | Apr 1989 | A |
4863357 | Olofsson | Sep 1989 | A |
5017087 | Sneddon | May 1991 | A |
5195882 | Freeman | Mar 1993 | A |
5605124 | Morgan | Feb 1997 | A |
5692372 | Whurr | Dec 1997 | A |
5960711 | Nordin | Oct 1999 | A |
6155807 | Fenton | Dec 2000 | A |
6217304 | Shaw | Apr 2001 | B1 |
6332271 | Hampel | Dec 2001 | B1 |
6651433 | George, Jr. | Nov 2003 | B1 |
6705849 | Zhong et al. | Mar 2004 | B2 |
6905319 | Guo | Jun 2005 | B2 |
20040005235 | Didin | Jan 2004 | A1 |
20040208740 | Hubbard | Oct 2004 | A1 |
20050089414 | Ohman | Apr 2005 | A1 |
20050169789 | Okada | Aug 2005 | A1 |
20050223734 | Smith et al. | Oct 2005 | A1 |
20050226758 | Hossner | Oct 2005 | A1 |
20070137173 | Murrow et al. | Jun 2007 | A1 |
20070137174 | Murrow et al. | Jun 2007 | A1 |
Number | Date | Country |
---|---|---|
302 877 | Dec 1991 | EP |
627 041 | Sep 1999 | EP |
805 743 | Apr 2000 | EP |
1 132 618 | Sep 2001 | EP |
1 500 819 | Jan 2005 | EP |
787711 | Sep 1935 | FR |
427475 | Apr 1935 | GB |
89284 | May 1937 | SE |
1567804 | May 1990 | SU |
WO9747886 | Dec 1997 | WO |
Number | Date | Country | |
---|---|---|---|
20070175202 A1 | Aug 2007 | US |