Claims
- 1. A method for separating an initial gas mixture of different molecular weight gas molecules on the basis of molecular weight of the different components of the mixture, comprising the steps of
- introducing the gas mixture to be separated into a separation zone, rotatably moving at least one curved hydrodynamically smooth porous surface in said separation zone with a relative velocity v.sub.w with respect to said gas mixture under non-turbulent conditions to provide a thin laminar boundary layer of said gas mixture adjacent said hydrodynamically smooth porous surface having a boundary layer displacement thickness .delta..sub.1, to provide an acceleration field having a strength of at least about 1.times.10.sup.5 g immediately adjacent said thin laminar boundary layer, passing heavier molecular weight gas components through said thin laminar boundary layer with a differential sedimentation velocity of different molecular weight components through said thin laminar boundary layer which is largest for the highest molecular weight gas component, such that the highest molecular weight gas component is preferentially concentrated at said hydrodynamically smooth porous surface, and
- conducting gas from immediately adjacent said hydrodynamically smooth porous surface which is preferentially concentrated in the highest molecular weight gas component through said porous surface to produce a separated higher molecular weight gas fraction which is enriched in said heaviest molecular weight gas component with respect to the composition of said initial gas mixture.
- 2. A method in accordance with claim 1 wherein said gas mixture comprises a major proportion of a light lubricant gas and a minor proportion of heavier molecular weight gas components to be separated.
- 3. A method in accordance with claim 2 wherein said hydrodynamically smooth surface is a concave curved surface zone of an airfoil blade, and wherein said accelerative field is a centrifugal field of strength
- v.sub.w.sup.2 /(r.sub.o -.delta..sub.1)
- wherein r.sub.o is the radius of curvature of said porous surface at the point of centrifugal field calculation.
- 4. A method in accordance with claim 3 wherein the sedimentation time through the boundary layer for the heavier molecular weight components to be separated does not exceed the effective collision time for said heavier molecular weight components.
- 5. A method in accordance with claim 3 wherein said gas is conducted through said porous surface at an effective suction velocity u.sub.s at the porous surface, which does not exceed the sedimentation velocity through said thin laminar boundary layer of the heaviest molecular weight component to be separated.
- 6. A method in accordance with claim 3 wherein said hydrodynamically smooth porous surface has a substantially nonselective pore size less than about 2.5 times said displacement thickness .delta..sub.1.
- 7. A method in accordance with claim 3 wherein the product of the mean free path of the said heavier molecular weight gas components to be separated, times the persistence of velocity factor therefor, integrally summed through said thin laminar boundary layer, is maintained greater than the mean distance of particle travel through said thin laminary boundary layer to said porous surface.
- 8. A method in accordance with claim 3 wherein a plurality of said porous surfaces are provided on a plurality of said concave surface zones of at least one turbomechanical blade row of airfoil blades.
- 9. A method in accordance with claim 8 wherein a plurality of said turbomechanical blade rows is provided in an axial turbomechanical compressor array having a plurality of compressor stages comprising alternating rotor and stator blade rows, and wherein the compression ratio per stage does not exceed about 1.2.
- 10. A method in accordance with claim 8 wherein a plurality of said turbomechanical blade rows is provided in an axial turbine array comprising alternating rotor and stator blade row stages.
- 11. A method in accordance with claim 10 wherein the rate at which heavier seed gases are conducted through the porous surfaces at each blade unit stage is in the range of from about 10 to about 50 mole percent of the axial flow rate of said heavier gas components to the respective blade unit.
- 12. A method in accordance with claim 8 wherein the ratio of average blade speed to the speed of gas conducted along the direction of the axis of rotation is at least about 2.
- 13. A method in accordance with claim 8 wherein said lubricant gas is selected from the group consisting of helium and hydrogen, wherein said higher molecular weight components to be separated are an isotopic mixture of UF.sub.6, and wherein the molar ratio of lubricant gas to UF.sub.6 is at least about 20:1.
- 14. A method in accordance with claim 13 wherein said porous surfaces have a nonselective pore size which does not exceed about 2.5 times said displacement thickness .delta..sub.1.
- 15. A method in accordance with claim 14 wherein the mean sedimentation time of said heavier molecular weight gas components to pass through said thin laminar boundary layer is less than the mean time between collisions between said heavier molecular weight components in passing through said thin laminar boundary layer.
- 16. A method in accordance with claim 13 wherein the radius of curvature of r.sub.o of said curved surface zones is less than about 2 centimeters.
- 17. A method in accordance with claim 13 wherein said centrifugal field is at least about 1.times.10.sup.6 g.
- 18. A method in accordance with claim 17 wherein the product of the mean free path of the said heavier molecular weight gas components to be separated, times the persistence of velocity factor therefor, integrally summed through said thin laminar boundary layer, is maintained greater than the mean distance of particle travel through said thin laminary boundary layer to said porous surface.
- 19. A method in accordance with claim 13 wherein said gas is conducted through said porous surface at an effective suction velocity u.sub.s at the porous surface, which suction velocity does not exceed the sedimentation velocity through said thin laminary boundary layer of the heaviest molecular weight component to be separated.
- 20. A method in accordance with claim 19 wherein said effective suction velocity u.sub.s at said porous surfaces is greater than about 1.18.times.10.sup.-4 of the relative velocity v.sub.w, and wherein the sedimentation velocity u.sub.o of the heaviest gas molecule through the boundary layer exceeds the effective suction velocity u.sub.s.
- 21. A method in accordance with claim 20 wherein said boundary layer thickness .delta..sub.1 is less than 1.times.10.sup.2 of said radius of curvature r.sub.o of said curved porous surface zones.
- 22. A method in accordance with claim 3 wherein the mean sedimentation time of said heavier molecular weight gas components to pass through said thin laminar boundary layer is less than the mean time between collisions between said heavier molecular weight components in passing through said thin laminar boundary layer.
Parent Case Info
This application is a continuation of copending application Ser. No. 824,515 filed Aug. 15, 1977, now U.S. Pat. No. 4,193,775, which is a continuation-in-part of application Ser. No. 708,939 filed July 22, 1976, now abandoned.
US Referenced Citations (8)
Foreign Referenced Citations (1)
Number |
Date |
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530646 |
Jul 1931 |
DE2 |
Continuations (1)
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Number |
Date |
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Parent |
824515 |
Aug 1977 |
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Continuation in Parts (1)
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708939 |
Jul 1976 |
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