IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
UP-0034608
(2008-02-20)
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등록번호 |
US-7856834
(2011-02-24)
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발명자
/ 주소 |
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출원인 / 주소 |
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대리인 / 주소 |
McAndrews, Held & Malloy, Ltd.
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인용정보 |
피인용 횟수 :
7 인용 특허 :
121 |
초록
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A centrifugal compressor assembly for compressing refrigerant in a 250-ton capacity or larger chiller system comprising a motor, preferably a compact, high energy density motor or permanent magnet motor, for driving a shaft at a range of sustained operating speeds under the control of a variable spe
A centrifugal compressor assembly for compressing refrigerant in a 250-ton capacity or larger chiller system comprising a motor, preferably a compact, high energy density motor or permanent magnet motor, for driving a shaft at a range of sustained operating speeds under the control of a variable speed drive. Another embodiment of the centrifugal compressor assembly comprises a mixed flow impeller and a vaneless diffuser sized such that a final stage compressor operates with an optimal specific speed range for targeted combinations of head and capacity, while a non-final stage compressor operates above the optimum specific speed of the final stage compressor. Another embodiment of the centrifugal compressor assembly comprises an integrated inlet flow conditioning assembly comprising a flow conditioning nose, a plurality of inlet guide vanes and a flow conditioning body that positions inlet guide vanes to condition flow of refrigerant into an impeller to achieve a target approximately constant angle swirl distribution with minimal guide vane turning.
대표청구항
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I claim: 1. A mixed flow impeller for use in compressing refrigerant in a multistage centrifugal compressor assembly having a final stage compressor and a non-final stage compressor, said mixed flow impeller comprising: an impeller hub, an impeller shroud, and a plurality of impeller blades arrange
I claim: 1. A mixed flow impeller for use in compressing refrigerant in a multistage centrifugal compressor assembly having a final stage compressor and a non-final stage compressor, said mixed flow impeller comprising: an impeller hub, an impeller shroud, and a plurality of impeller blades arranged for approximately constant relative diffusion in the mixed flow impeller, the mixed flow impeller having a nominal diameter less than a maximum diameter at a multistage centrifugal compressor assembly capacity and sized to meet a target flow and a target head such that the final stage compressor has a final stage specific speed within an optimum specific speed range for the final stage compressor and the non-final stage compressor has a non-final stage specific speed that exceeds the final stage specific speed. 2. The mixed flow impeller of claim 1 wherein said mixed flow impeller with a nominal diameter has an exit pitch angle, measured from an axis of rotation of the impeller, within a range from 20 to 90 degrees relative to an axis of rotation of the impeller. 3. The mixed flow impeller of claim 1 wherein the mixed flow impeller further comprises a wall profile defined by the impeller hub and the impeller shroud for the mixed flow impeller with the maximum diameter and coincident with a wall profile of a vaneless diffuser downstream of the mixed flow impeller. 4. The mixed flow impeller of claim 1 wherein the mixed flow impeller has an internal surface machined, cast, coated, finished or a combination thereof to less than about 125 RMS. 5. The mixed flow impeller of claim 1 wherein the mixed flow impeller has an external surface machined, cast, coated, finished or a combination thereof to less than about 125 RMS. 6. The mixed flow impeller of claim 1 wherein the mixed flow impeller has an external surface and an internal surface, said external surface and internal surface machined, cast, coated, finished or a combination thereof to less than about 125 RMS. 7. The mixed flow impeller of claim 1 wherein the mixed flow impeller comprises a non-final stage mixed flow impeller housed in a non-final stage compressor housing and a final stage mixed flow impeller housed in a final stage compressor housing; said non-final stage mixed flow impeller and said final stage mixed flow impeller are configured in a back-to-back relation; wherein a motor is mounted in a housing between the non-final stage compressor housing and the final stage compressor housing. 8. A method for sizing an impeller and a diffuser for a multistage compressor having a final stage compressor and a non-final stage compressor, the method comprising the steps of: a. casting for each compressor stage a mixed flow impeller with a maximum diameter for a speed within a range of operating speeds of the multistage compressor; said mixed flow impeller further comprising an impeller hub, an impeller shroud, and plurality of impeller blades arranged for approximately constant relative diffusion in the impeller; b. trimming the mixed flow impeller from the maximum diameter to a nominal diameter for each compressor stage to set an impeller exit pitch angle within a range from 20 to 90 degrees relative to the axis of rotation of the impeller, said trimming of the mixed flow impeller for each compressor stage to meet a target flow and a target head such that the final stage compressor has a final stage specific speed within an optimum specific speed range for the final stage compressor and the non-final stage compressor has a non-final stage specific speed that exceeds the final stage specific speed; and c. machining a vaneless diffuser having a wall profile coincident with a wall profile defined by the impeller hub and the impeller shroud for the mixed flow impeller with the maximum diameter. 9. The method for sizing of claim 8 wherein the trimming step further comprises trimming such that a line intersects a mean diameter of and is perpendicular to a line axissymetric an axis of rotation of the impeller. 10. The method for sizing of claim 8 wherein the trimming step further comprises trimming an angle cutback for the mixed flow impeller with a mixed flow exit angle. 11. The method for sizing of claim 8 wherein the trimming step further comprises trimming at a constant radius for the mixed flow impeller with a radial flow exit angle. 12. The method for sizing of claim 8 wherein the casting step further comprises providing an internal and an external surface of the mixed flow impeller to less than about 125 RMS. 13. The method for sizing of claim 8 further comprising the step of finishing an internal surface and an external surface of the mixed flow impeller by machining, coating, or a combination thereof to less than about 125 RMS. 14. A chiller system comprising: an evaporator; a condenser; and a multistage centrifugal compressor for compressing refrigerant; the evaporator, the condenser; and the multistage centrifugal compressor connected in a closed loop; said multistage centrifugal compressor further comprising: a. a shaft; b. a motor mounted in a motor housing; said motor for driving the shaft at a range of sustained operating speeds; c. a variable speed drive for varying operation of the motor within the range of sustained operating speeds; d. a final stage compressor and a non-final stage compressor mounted on the shaft; each compressor comprises: i. a compressor housing; said compressor housing having a compressor inlet for receiving the refrigerant and a compressor outlet for delivering the refrigerant; and ii. a mixed flow impeller in fluid communication with said compressor inlet and said compressor outlet, the mixed flow impeller mounted to said shaft being operable to compress refrigerant and further comprising: an impeller hub, an impeller shroud, and a plurality of impeller blades arranged for approximately constant relative diffusion in the mixed flow impeller, the mixed flow impeller having a nominal diameter less than a maximum diameter at a multistage centrifugal compressor capacity and sized to meet a target flow and a target head such that the final stage compressor has a final stage specific speed within an optimum specific speed range for the final stage compressor and the non-final stage compressor has a non-final stage specific speed that exceeds the final stage specific speed. 15. The chiller system of claim 14 wherein the refrigerant is R-123, R-134a or R-22 in liquid, gas, or multiple phases. 16. The chiller system of claim 14 wherein the refrigerant is an azeotrope, a zeotrope or a mixture or blend thereof in liquid, gas, or multiple phases. 17. The chiller system of claim 14 further comprising a vaneless diffuser having a wall profile coincident with a wall profile defined by the impeller hub and the impeller shroud for the mixed flow impeller with the maximum diameter. 18. The chiller system of claim 17 wherein each stage compressor further comprises an external volute forming a circumferential flow path around each said compressor housing for receiving refrigerant from the vaneless diffuser. 19. The chiller system of claim 18 wherein the external volute has a centroid radius greater than a centroid radius of the vaneless diffuser. 20. The chiller system of claim 14 wherein the mixed flow impeller with a nominal diameter has an exit pitch angle, measured from an axis of rotation of the impeller, within a range from 60 to 90 degrees relative to the axis of rotation of the impeller. 21. The chiller system of claim 14 further comprising an economizer connected in the closed refrigerant loop. 22. The chiller system of claim 14 further comprising a coaxial economizer connected in the closed loop, wherein said coaxial economizer further comprises: a. an inner housing and an outer housing having a common longitudinal axis; said outer housing having an inlet for receiving a refrigerant from a stage of a multistage compressor and an outlet for conveying a refrigerant to a downstream stage of the multistage compressor; b. a flow chamber forming a fluid flow path about the inner housing; c. a flash chamber for flashing refrigerant in a liquid state to a gas state; and d. a flow passage between the flash chamber and the flow chamber for conveying a flashed gas from the flash chamber to the flow chamber; wherein the flashed gas conveyed from the flash chamber and the refrigerant received from the inlet of the outer housing mix along the fluid flow path toward the outlet of the outer housing. 23. The chiller system of claim 22 wherein the inner housing is defined by the condenser and the outer housing is defined by an economizer. 24. The chiller system of claim 22 wherein the inner housing is defined by the evaporator and the outer housing is defined by an economizer. 25. The chiller system of claim 14 wherein the variable speed drive is a variable frequency drive configured to vary operation of the motor within the range of sustained operating speeds. 26. The chiller system of claim 14 wherein the motor is an induction motor. 27. The chiller system of claim 14 wherein the motor comprises a compact, high energy density motor. 28. The chiller system of claim 27 wherein the compact, high energy density motor comprises a permanent magnet motor of high energy density magnetic materials of at least 20 Mega Gauss Oersted. 29. The chiller system of claim 27 wherein the range of sustained operating speeds for the compact, high energy density motor is within about 4,000 revolutions per minute to about 20,000 revolutions per minute for a R-134a refrigerant. 30. The chiller system of claim 27 wherein the range of sustained operating speeds for the compact, high energy density motor is within about 4,000 revolutions per minute to about 8,600 revolutions per minute for a R-123 refrigerant. 31. The chiller system of claim 14 wherein the motor has a horsepower in the range of about 125 to about 2500. 32. The chiller system of claim 14 wherein the multistage centrifugal compressor has a capacity within the range of about 250 tons and 2000 tons. 33. The chiller system of claim 14 wherein at least one mixed flow impeller has an internal surface machined, cast, coated, finished or a combination thereof to less than about 125 RMS. 34. The chiller system of claim 14 wherein at least one mixed flow impeller has an external surface machined, cast, coated, finished or a combination thereof to less than about 125 RMS. 35. The chiller system of claim 14 wherein a non-final stage compressor housing is positioned in a back-to-back relation with a final stage compressor housing; and the motor is disposed between the non-final stage compressor housing and the final stage compressor housing. 36. The chiller system of claim 14 wherein the non-final stage compressor of the multistage centrifugal compressor is configured to discharge the refrigerant into a coaxial economizer. 37. The chiller system of claim 14 wherein the final stage compressor of the multistage centrifugal compressor is configured to discharge into the condenser of a coaxial economizer. 38. The chiller system of claim 37 wherein the condenser comprises tube bundles, said tube bundles are arranged approximately tangentially to a flow direction of the refrigerant discharged from the final stage compressor outlet. 39. The chiller system of claim 14 wherein the final stage compressor inlet of the final stage compressor receives the refrigerant from a second suction pipe defining a fluid flow path that is in fluid communication with a coaxial economizer. 40. The chiller system of claim 39 wherein the second suction pipe further comprises a swirl reducer positioned in the second suction pipe such that the refrigerant has a swirling flow upstream of the swirl reducer and a substantially axially flow downstream of the swirl reducer. 41. The chiller system of claim 39 wherein the second suction pipe receives the refrigerant from a conformal draft pipe; the conformal draft pipe forming a circumferential flow path around and being connected to the coaxial economizer. 42. The chiller system of claim 41 wherein the conformal draft pipe has a wrap angle around the coaxial economizer, said wrap angle is about 180 degrees. 43. The chiller system of claim 14 wherein at least one compressor stage further comprises an inlet flow conditioning assembly for conditioning refrigerant upstream of the mixed flow impeller comprising: a. an inlet flow conditioning housing positioned within the compressor and upstream of an impeller housed in the compressor; the inlet flow conditioning housing forming a flow conditioning channel having a channel inlet in fluid communication with a channel outlet; b. a flow conditioning body having a first body end, an intermediate portion and a second body end; said flow conditioning body being substantially centrally positioned along a length of the flow conditioning channel; the flow conditioning body is arranged coincident to a flow conditioning nose at the first body end and coincident to an impeller hub of the mixed flow impeller at the second body end, said flow conditioning body having a streamline curvature with a radius relative to an axis of rotation of the impeller that exceeds a radius of the impeller hub; and c. a plurality of inlet guide vanes positioned between said channel inlet and channel outlet; said plurality of inlet guide vanes being rotatably mounted on a support shaft at a location along the flow conditioning body where the radius relative to the axis of rotation of the mixed flow impeller exceeds the radius of the impeller hub. 44. The chiller system of claim 43 wherein the inlet flow conditioning assembly further comprises a strut including a first strut end and a second strut end, the first strut end attached to the flow conditioning nose and the second strut end attached to the inlet flow conditioning housing. 45. The chiller system of claim 44 wherein the inlet flow conditioning assembly further comprises at least two struts.
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