Patent Application
20150093232
The present invention relates generally to a compressor, and more particularly to a rotor of a supersonic compressor.
Compressors are used to compress fluids and are widely used in systems ranging from refrigeration units to jet engines. During operation, the compressor applies mechanical energy to a fluid at lower pressure to raise pressure of the fluid to higher pressure. Compression of the fluid is ether performed in a single stage or in multiple stages. Currently available compression technology varies from centrifugal compression systems to mixed flow compression systems, to axial flow compression systems. The performance of the compressor may be measured by a pressure ratio of the fluid before and after a compression stage. Typically, the pressure ratio achieved in single stage compression is relatively low. Higher pressure ratios are achievable by multistage compression. However, compressors having multiple stages tend to be large, complex and of high cost.
Supersonic compressors are believed to overcome some of the limitations of conventional compressors. In such supersonic compressors, compression is performed by contacting an inlet fluid with a moving rotor having a plurality of rotor vanes which moves the inlet fluid from a low pressure side of the rotor to a high pressure side of the rotor. Generally, in such supersonic compressors, the velocity of the fluid at the high pressure side of the rotor is reduced to subsonic velocity due to generation of a normal shockwave within flow channels defined by the plurality of rotor vanes. An interaction of the normal shockwave with a boundary layer in the flow channels results in a local flow separation of the compressed fluid. Such local flow separation results in reduction of an overall operating efficiency of the compressor. Thus, there is a need for an enhanced supersonic compressor.
In accordance with one exemplary embodiment, a supersonic compressor rotor is disclosed. The supersonic compressor rotor includes a first rotor disk and a second rotor disk. Further, the supersonic compressor rotor includes a first set of rotor vanes coupled to and disposed between the first and second rotor disks and defining together with the first and second rotor disks, a first set of flow channels. The supersonic compressor rotor further includes a second set of rotor vanes coupled to and disposed between the first and second rotor disks and defining together with the first and second rotor disks, a second set of flow channels. The first set of rotor vanes is disposed offset from the second set of rotor vanes and the first set of flow channels and the second set of flow channels are configured such that each flow channel of the first set of flow channels is in fluid communication with at least one flow channel of the second set of flow channels. Further, the supersonic compressor rotor includes a plurality of compression ramps configured such that each compression ramp is disposed on a rotor vane surface opposite an adjacent rotor vane surface.
In accordance with one exemplary embodiment, a supersonic compressor is disclosed. The supersonic compressor includes a casing having a fluid inlet and a fluid outlet and a rotor shaft. Further, the supersonic compressor includes at least one supersonic compressor rotor disposed within the casing. The supersonic compressor rotor includes a first rotor disk and a second rotor disk coupled to the first rotor disk and the rotor shaft. Further, the supersonic compressor rotor includes a first set of rotor vanes coupled to and disposed between the first and second rotor disks and defining together with the first and second rotor disks, a first set of flow channels. The supersonic compressor rotor further includes a second set of rotor vanes coupled to and disposed between the first and second rotor disks and defining together with the first and second rotor disks, a second set of flow channels. The first set of rotor vanes is disposed offset from the second set of rotor vanes and the first set of flow channels and the second set of flow channels are configured such that each flow channel of the first set of flow channels is in fluid communication with at least one flow channel of the second set of flow channels. Further, the supersonic compressor rotor includes a plurality of compression ramps configured such that each compression ramp is disposed on a rotor vane surface opposite an adjacent rotor vane surface.
In accordance with one exemplary embodiment, a method of compressing a fluid is disclosed. The method includes introducing a first fluid into at least one flow channel of a first set of flow channels of a supersonic compressor rotor configured to be driven by a shaft. Further, the method includes performing a first compression of the first fluid in the at least one flow channel of the first set of flow channels, to produce a second fluid. The method further includes introducing the second fluid into at least one flow channel of a second set of flow channels of the supersonic compressor rotor. Further, the method includes performing a second compression of the second fluid in the at least one flow channel of the second set of flow channels, to produce a further compressed second fluid. The further compressed second fluid is characterized by a higher pressure than the second fluid, the first set of first flow channels is defined by adjacent rotor vanes of a first set of rotor vanes, the second set of second flow channels is defined by adjacent rotor vanes of a second set of rotor vanes, each flow channel of the first set and second set of flow channels is further defined by a compression ramp disposed on a rotor vane surface opposite an adjacent rotor vane surface, and the first set and second set of rotor vanes are coupled to and disposed between a first rotor disk and a second rotor disk.
These and other features and aspects of embodiments of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
While only certain features of embodiments of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as fall within the spirit of the invention.
As used herein, the term a “supersonic compressor” is referred to a compressor comprising a supersonic compressor rotor. The supersonic compressor may include one or more supersonic compressor rotors configured to compress a fluid which flows radially inward or outward between a plurality of rotor vanes disposed between a pair of rotor disks. In such a supersonic compressor, the fluid is transported from a low pressure side of a fluid conduit to between the plurality of rotor vanes and then to a high pressure side of the fluid conduit.
The supersonic compressor rotor is referred to as “supersonic” because such a rotor comprises compression ramps and is designed to rotate about an axis at higher speeds such that a flow of fluid, encountering a compression ramp of the rotor, has a relative fluid velocity, which is supersonic. The relative fluid velocity may be defined as a vector sum of a rotor velocity at a leading edge of the compression ramp and a fluid velocity just prior to encountering the leading edge of the compression ramp. Additionally, the relative fluid velocity may also be referred to as a “local supersonic inlet velocity” which in certain embodiments is a combination of an inlet fluid velocity and a tangential speed of the compressor rotor at a fluid inlet of the compressor. The supersonic compressor rotors are operated at very high tangential speeds, for example tangential speeds in a range of 250 meters/second to 800 meters/second.
In one embodiment, the exemplary supersonic compressor may be used within a larger system, for example a gas turbine engine or a jet engine. The overall size and weight of a gas turbine engine may be reduced due to the enhanced compression ratios attainable by the supersonic compressor. Embodiments discussed herein enhance the efficiency of the supersonic compressor by restricting generation of normal shockwaves at the downstream end of each rotor vane of the second set of rotor vanes. Further, the embodiments detailed above decreases the propensity of the compressed fluid to experience a local flow separation due to a weaker interaction of a boundary layer with the normal shock waves.
Embodiments discussed herein disclose rotors for supersonic compressors and a method of compressing a fluid. In one or more embodiments, the present invention provides a supersonic compressor comprising a supersonic compressor rotor. The supersonic compressor rotor includes two sets of rotor vanes disposed between a pair of rotor disks. The first set of rotor vanes and the pair of rotor disks defines a first set of flow channels. The second set of rotor vanes and the pair of rotor disks defines a second set of flow channels. Further, a plurality of compression ramps is configured such that each compression ramp is disposed on a rotor vane surface opposite an adjacent rotor vane surface. The compression ramps are configured to generate oblique shockwaves within each flow channel of the first set and second set of flow channels. Further, in such supersonic compressors, the generation of a normal shockwave is restricted to an end of each flow channel of the second set of flow channels. The normal shockwave causes reduction in velocity of the compressed fluid to a subsonic velocity only at the end of each flow channel of the second set of flow channels.
In the illustrated exemplary embodiment, the intake section 102 includes an inlet guide vane assembly 126 comprising one or more inlet guide vanes 128 for directing a first fluid 224 from the fluid inlet 116 to the compressor section 104. The compressor section 104 includes at least one supersonic compressor rotor 130 that is coupled to the rotor shaft 112. The supersonic compressor rotor 130 is configured for radial compression of the first fluid 224 and includes a first rotor disk 136, a second rotor disk 138, and a first set and a second set of rotor vanes 162, 164. In the illustrated embodiment, the supersonic compressor 100 is configured for a single stage compression of the first fluid 224. The discharge section 106 includes an outlet guide vane assembly 132 having one or more outlet guide vanes 133 for directing a compressed second fluid 226 from the compressor section 104 to the fluid outlet 118. The drive assembly 108 drives the supersonic compressor rotor 130 via the rotor shaft 112. In other embodiments, the compressor section 104 may include more than one supersonic compressor rotor 130 and be configured for a multi stage compression of the first fluid 224.
In the exemplary embodiment, the fluid inlet 116 defines a flow path for the first fluid 224 from a fluid source 124 to the intake section 102. The first fluid 224 may be any fluid such as, for example a gas or a gas mixture. The intake section 102 defines a flow path for the flow of first fluid 224 from the fluid inlet 116 to the compressor section 104. The compressor section 104 compresses the first fluid 224 and discharges the compressed second fluid 226 to the discharge section 106. The outlet guide vane assembly 132 of the discharge section 106 defines a flow path for the compressed second fluid 226 from the supersonic compressor rotor 130 to the fluid outlet 118. The fluid outlet 118 feeds the compressed second fluid 226 to an output system 134 such as, for example, a turbine engine system, a fluid treatment system, and/or a fluid storage system.
In the illustrated exemplary embodiment, the first rotor disk 136 includes a first radial surface 144a, a second radial surface 146a, and a body 163a extending between the first radial surface 144a and the second radial surface 146a. The body 163a has an inner surface 140a and an outer surface 142a.
In the illustrated exemplary embodiment, the second rotor disk 138 includes a first radial surface 144b, a second radial surface 146b, and a body 163b extending between the first radial surface 144b and the second radial surface 146b. The body 163b has an inner surface 140b and an outer surface 142b. The second rotor disk 138 further includes an end wall 148 coupled to the second radial surface 146b. Further, the end wall 148 is coupled to a plurality of rotor support struts 160 which are in turn coupled to the rotor shaft 112. In the exemplary embodiment, the first rotor disk 136 is coupled to the second rotor disk 138 via the first set and second set of rotor vanes 162, 164. In certain other embodiments, the first rotor disk 136 may be directly coupled to the rotor shaft 112 for example via the plurality of rotor support struts 160. It should be noted herein that the coupling of the rotor shaft 112 to the first rotor disk 136 or the second rotor disk 138 may vary depending on the application and design criteria.
In the illustrated exemplary embodiment, a first circumferential axis 166 serves as a geometric reference for positioning the first set of rotor vanes 162. For example, in one embodiment, the first circumferential axis 166 passes through a midpoint 168 of each rotor vane 162. It should be noted that first circumferential axis 166 is defined between the first radial surface 144a and the second radial surface 146a of the first rotor disk 136 and between the first radial surface 144b and the second radial surface 146b of the second rotor disk 138. Each rotor vane 162 is spaced apart from adjacent vanes 162 by a gap F1. In the illustrated embodiment, the first set of rotor vanes 162 includes six rotor vanes, each of which has a leading edge 178 and a trailing edge 180. The leading edge 178 is positioned proximate to the first radial surfaces 144a, 144b of the first and second rotor disks 136, 138 respectively. Similarly, the trailing edge 180 is positioned proximate to second and third circumferential axes 150a, 150b of the first and second rotor disks 136, 138 respectively. In the embodiment shown, the second circumferential axis 150a is defined along a set of midpoints between the first radial surface 144a and the second radial surface 146a of the first rotor disk 136. Similarly, the third circumferential axis 150b is defined along a set of midpoints between the first radial surface 144b and the second radial surface 146b of the second rotor disk 138. In the illustrated exemplary embodiment, each rotor vane 162 includes a pressure side vane surface 182 and a suction side vane surface 184. In one embodiment, at least one rotor vane 162 comprises only one compression ramp 176. In the embodiment shown, each rotor vane 162 comprises one compression ramp 176 on the pressure side vane surface 182 opposite to the suction side vane surface 184 of adjacent rotor vanes 162. Specifically, compression ramp 176 is positioned at the leading edge 178 of each rotor vane 162. Further, each rotor vane 162, has a vane inner side 206, a vane outer side 208, and a height 244a measured from the vane inner side 206 and the vane outer side 208.
In the illustrated exemplary embodiment, a fourth circumferential axis 188 serves as a geometric reference for positioning the second set of rotor vanes 164. For example, in one embodiment, the fourth circumferential axis 188 passes through a midpoint 186 of each rotor vane 164. Each rotor vane 164 is spaced apart from adjacent vanes 164 by a gap S1. In the illustrated embodiment, the second set of rotor vanes 164 includes six rotor vanes, each of which has a leading edge 190 and a trailing edge 192. The leading edge 190 is positioned proximate to the trailing edge 180 of each adjacent rotor vane 162. It should be noted herein that the term “proximate” means there are no intervening vanes between the leading edge 190 and the trailing edge 180. Similarly, the trailing edge 192 is positioned proximate to the second radial surfaces 146a, 146b of the first and second rotor disks 136, 138 respectively. In the illustrated exemplary embodiment, each rotor vane 164 includes a pressure side vane surface 194 and a suction side vane surface 196. In one embodiment, at least one rotor vane 164 comprises only one compression ramp 198. In the embodiment shown, each rotor vane 164 comprises a compression ramp 198 on the pressure side vane surface 194 opposite to the suction side vane surface 196 of adjacent rotor vanes 164. Specifically, compression ramp 198 is positioned at the leading edge 190 of each rotor vane 164. Further, each rotor vane 164, has a vane inner side 209, a vane outer side 211, and a height 244b measured from the vane inner side 209 and the vane outer side 211. It should be noted herein that the number of rotor vanes in the first set of rotor vanes 162 and the second set of rotor vanes 164 are same
In the illustrated exemplary embodiment, the compression ramps 176, 198 are integral to the first set and second set of rotor vanes 162, 164 respectively. Rotor vanes comprising such integral compression ramps can be manufactured for example, by casting from a molten metal or by machining the rotor vane from a single piece of metal. In certain other embodiments, the compression ramps 176, 198 are not integral to the first set and second set of rotor vanes 162, 164 respectively. In such embodiments, each rotor vane and the corresponding compression ramp are created separately and later joined.
In the illustrated exemplary embodiment, each rotor vane 162 is disposed offset by a distance 200 from adjacent rotor vane 164. It should be noted herein that the term “offset” means the leading edge 190 of each rotor vane 164 is disposed by an “offset distance” from the trailing edge 180 of adjacent rotor vane 162. In the exemplary embodiment, the offset distance 200 may be in a range of 1 percent to 15 percent of a diameter of the first set of rotor vanes 162, at the leading edge 178. The offset distance 200 between the first set of rotor vanes 162 and the second set of rotor vanes 164 may vary depending on the application and design criteria.
In the exemplary embodiment, each rotor vane 162 has a height 244a equal to approximately one-tenth of the length of each rotor vane 162. Each rotor vane 164 has a height 244b equal to approximately one-sixth of the length of each rotor vane 164. Each rotor vane 164 has a length equal to about three-fourths of the length of adjacent rotor vane 162.
In certain embodiments, the supersonic compressor rotor 130 may be manufactured using any suitable materials for example, aluminum, aluminum alloys, steel, steel alloys, nickel alloys, and titanium alloys, depending on design requirements. In some embodiments, composite structures may also be used which combine the relative strengths of several different materials including those listed above and non-metallic materials. The compressor casings, inlet guide vanes, and outlet guide vanes may be made of any suitable material including cast iron. In certain embodiments, supersonic compressor rotor components may be prepared by metal casting techniques and/or machining.
In the illustrated exemplary embodiment, a first set of flow channels 210 is defined by adjacent rotor vanes 162 and the first and second rotor disks 136, 138. Similarly, a second set of flow channels 212 is defined by adjacent rotor vanes 164 and the first and second rotor disks 136, 138. More particularly, each flow channel 210 is formed between the pressure side vane surface 182 of each rotor vane 162 and the suction side vane surface 184 of adjacent rotor vane 162. Similarly, each flow channel 212 is formed between the pressure side vane surface 194 of each rotor vane 164 and the suction side vane surface 196 of adjacent rotor vane 164.
The plurality of rotor support struts 160 are coupled to the rotor shaft 112 and the second rotor disk 138 via the end wall 148. The first rotor disk 136 is coupled to the second rotor disk 138 via the first set and second set of rotor vanes 162, 164.
When the drive shaft 112 is rotated, the first fluid 224 introduced through the fluid inlet 116 (as shown in
The further compressed second fluid 226 then exits along a direction 227 via the high pressure side 220 of the fluid conduit 216. The further compressed second fluid 226 within the high pressure side 220 of the fluid conduit 216 may be used to perform work.
The supersonic compressor 100 is configured for an outside-in compression of the first fluid 224. During operation, the rotation of the supersonic compressor rotor 130 directs the flow of the first fluid 224 from the first radial surfaces 144a, 144b of the first and second rotor disks 136, 138 respectively, through the first set and second set of flow channels 210, 212 (e.g. as shown in
The first pair of rotor vanes 228 defines a first inlet opening 230, a first outlet opening 232, and the flow channel 210. Each flow channel 210 extends between the first inlet opening 230 and the first outlet opening 232 and defines a first flow path represented by arrow 234. The first inlet opening 230 is defined between an inlet edge 238a positioned at the leading edge 178 of each rotor vane 162 and an inlet edge 238b positioned perpendicularly from the inlet edge 238a on adjacent rotor vane 162. Thus, an imaginary line between inlet edges 238a and 238b will be perpendicular to the surface of the rotor vane 162. The first outlet opening 232 is defined between an outlet edge 240a positioned at the trailing edge 180 of each rotor vane 162 and an outlet edge 240b positioned perpendicularly from the outlet edge 240a on adjacent rotor vane 162. Each flow channel 210 is sized, shaped, and oriented to direct the first fluid 224 along the first flow path 234 from the first inlet opening 230 to the first outlet opening 232
The second pair of rotor vanes 231 defines a second inlet opening 246, a second outlet opening 248, and the flow channel 212. Each flow channel 212 extends between the second inlet opening 246 and the second outlet opening 248 and defines a second flow path represented by arrow 250. The second inlet opening 246 is defined between an inlet edge 252a positioned at the leading edge 190 of each rotor vane 164 and an inlet edge 252b positioned perpendicularly from the inlet edge 252a on adjacent rotor vane 164. The second outlet opening 248 is defined between an outlet edge 254a positioned at the trailing edge 192 of each rotor vane 164 and an outlet edge 254b positioned perpendicularly from the outlet edge 254a on adjacent rotor vane 164. Each flow channel 212 is sized, shaped, and oriented to channel the second fluid 225 along the second flow path 250 from the second inlet opening 246 to the second outlet opening 248.
In the illustrated exemplary embodiment, at least one compression ramp 176 is positioned within each flow channel 210. Specifically, compression ramp 176 is positioned between the first inlet opening 230 and the first outlet opening 232, and is sized, shaped, and oriented to generate during operation, one or more oblique shockwaves 258 within each flow channel 210. Similarly, at least one compression ramp 198 (also shown in
During operation of the supersonic compressor rotor 130, intake section 102 (as shown in
In the exemplary embodiment, each flow channel 212 has a second cross-sectional area 282 that varies with the width of the flow channel 212 along the second flow path 250. Specifically, each flow channel 212 has a second minimal cross-sectional area 282a proximate to an end of the compression ramp 198. It should be noted herein that the term “second minimal cross-sectional area” refers to a minimum width of the flow channel 212, for the second fluid 225 to flow through the flow path 250. The second minimal cross-sectional area 282a of each flow channel 212 may also be referred as a “second throat region”.
In the illustrated embodiment, the second minimal cross-sectional area 282a is smaller than the first minimal cross-sectional area 278a so as to further enhance the compression of the second fluid 225 in the flow channel 212. Each flow channel 210 includes a first converging portion 292 and a first diverging portion 294. Each flow channel 212 includes a second converging portion 296 and a second diverging portion 298.
The location of the compression ramps 176, 198 defines throat regions 278a, 282a of the flow channels 210, 212 of the supersonic compressor rotor 130. In an embodiment, one or more compression ramps 176 may be disposed on the pressure side vane surface 182 of each rotor vane 162. Similarly, one or more compression ramps 198 may be disposed on the pressure side vane surface 194 of each rotor vane 164. In certain other embodiments, each rotor vane 162, 164 may include more than one compression ramps 176, 198 respectively. In such embodiments, the compression ramps 176, 198 may be positioned on either or both rotor vane surfaces 182, 184 and 194, 196.
During operation of the supersonic compressor rotor 130, the first fluid 224 is directed into the first inlet opening 230 at a relative velocity, which is supersonic. The first fluid 224 entering each flow channel 210, contacts the compression ramp 176 to generate the oblique shockwave 258 at the leading edge 178 of each rotor vane 162. Specifically, a first oblique shockwave 258a contacts the surface of adjacent rotor vane 162 and a second oblique shockwave 258b is reflected back therefrom at an oblique angle α1.
As the first fluid 224 passes through the first flow channel 210, i.e. through the first converging portion 292 and the first diverging portion 294, the velocity of the first fluid 224 may be marginally reduced but remains supersonic. The pressure of the first fluid 224 is increased generating the second fluid 225. The second fluid 225 enters at least one flow channel 212 via the second inlet opening 246 (as shown in
As the second fluid 225 passes through at least one flow channel 212 i.e. in the second diverging portion 298, a normal shockwave 302 is generated in each flow channel 212. Then, the second fluid 225 flows into a subsonic diffusion zone 309, thereby generating a subsonic flow of the second fluid 225. It should be noted herein that the normal shockwave 302 is oriented along a perpendicular direction 304 relative to the second flow path 250, resulting in reduction of the velocity of the second fluid 225 to a subsonic velocity. In some other embodiments, the normal shockwave 302 may not be generated depending on the design and operating condition of the supersonic compressor 100.
Conventionally, use of a single set of longer rotor vanes results in a strong interaction of a boundary layer with normal shock waves. In accordance with the embodiments of the present invention, provision of two sets of relatively shorter rotor vanes 162, 164 instead of a single set of longer rotor vane, results in generation of weak oblique shockwaves 258, 259, thereby reducing the pressure losses. Additionally, the supersonic compressor rotor 130 having the two sets of rotor vanes 162, 164 results in formation of thinner boundary layers and thereby making the boundary layers more resistant to separation due to a weaker interaction with the normal shock waves 302 and hence resulting in lower pressure losses.
In the illustrated exemplary embodiment, each rotor vane 162 includes two compression ramps 176, 177. Specifically, compression ramp 176 is disposed on the pressure side vane surface 182 and compression ramp 177 is disposed on the suction side vane surface 184. More specifically, compression ramp 176 is positioned at the leading edge 178 and compression ramp 177 is positioned at a mid-region 179 of each rotor vane 162. Each rotor vane 164 includes the compression ramp 198 at the leading edge 190 of the pressure side vane surface 194. It should be noted herein that the term “pressure side vane surface” refers to the longer surface of a rotor vane and the term “suction side vane surface” refers to the shorter surface of the rotor vane. Fluid pressure at the pressure side vane surface is higher than fluid pressure at the suction side vane surface. The second converging portion 296 of each flow channel 212 (as shown in
In the illustrated exemplary embodiment, the compression ramp 176 is configured to generate the oblique shockwave 258 in response to the flow of the first fluid 224 so as to produce the second fluid 225. The second fluid 225 is expanded to generate an expanded second fluid 299, as the second fluid 225 passes through the first diverging portion 294. The compression ramp 177 is configured to generate an additional oblique shockwave 258 in response to the flow of the first fluid 224 so as to reduce the expansion of the second fluid 225 exiting the first diverging portion 294.
The compression ramps 398, 399 are configured to generate the oblique shockwaves 359 at the leading edge 390 on both the pressure side vane surface 394 and suction side vane surface 396, in response to a flow of a second fluid 325. Such oblique shockwaves 359 further enhances compression of the second fluid 325 in between the rotor vanes 364 which are further reflected from adjacent rotor vanes 362.
In accordance with the embodiments of the present invention, the supersonic compressor of the present disclosure can achieve higher pressure ratios by further compressing the compressed fluid between the second set of rotor vanes. The provision of the first set and second set of rotor vanes of the supersonic compressor rotor results in lower pressure losses between the rotor vanes, thereby increasing the efficiency of the supersonic compressor.
