Field of the Invention

[0001] This invention relates to liquid ring pumps, and more particularly to liquid ring pumps in which at least portions of the pump have textured surfaces to reduce fluid frictional losses in the pumps.

Background

[0002J In conventional liquid ring pumps, a rotor is rotatably mounted in a stationary annular housing so that the rotor axis is eccentric to the central axis of the housing. The rotor has blades which extend parallel to the rotor axis and which project outward radially from the rotor axis so that the blades are equally spaced in the circumferential direction around the rotor. A quantity of pumping liquid (usually water) is maintained in the housing so that as the rotor rotates, the rotor blades engage the liquid and form it into an annular ring inside the housing. Because the housing is eccentric to the rotor, the liquid ring is also eccentric to the rotor. This means that on one side of the pump (the so-called intake zone), the liquid between adjacent rotor blades is moving radially outward away from the rotor hub, while on the other side of the pump (the so-called compression zone), theJiquid between adjacent rotor blades is moving radially inward toward the rotor hub. A gas intake is connected to the intake zone so that gas to be pumped is pulled into the spaces between adjacent rotor blades where the liquid is moving radially outward. A gas discharge is connected to the compression zone so that gas compressed by the liquid moving radially inward can be discharged from the pump.

[0003] It is known that a major cause of energy loss in liquid ring pumps is fluid friction between the fluids within the pump and the design/configuration of the "wetted area" (the surface area inside of the pump exposed to fluid, such as the working liquid forming the liquid ring and/or the gas being pumped) of the pump due to drag.

[0004] The promise of drag reduction over solid surfaces is one that has captured the attention of researchers for years. In one exemplary approach, it is known that the aerodynamic drag of a surface may be reduced by applying a "texture" to the otherwise smooth surface. This can be seen, for example, in the dimples of a golf ball. The texture reduces the skin friction drag of solids moving through fluids (e.g., aircraft, ships, cars, etc.), and of fluids moving along solids (e.g., pipe flow, etc.). SUMMARY

[0005] Embodiments of this invention provide a liquid ring pump in which at least portions of the pump have textured surfaces to reduce fluid friction losses in the pump. The surfaces of the interior of the pump in contact with a fluid can be configured to provide for drag reduction. In one aspect, at least a portion of at least one surface of the interior of the pump in contact with a fluid can be configured to modify the fluid boundary layer on the surface. In another aspect, at least a portion of at least one surface of the interior of the pump in contact with a fluid can be configured to control separation of the fluid boundary layer.

[0006] In one aspect, a method is provided for reducing frictional losses in a liquid ring pump. In another aspect, the liquid ring pump can comprise a stationary housing having an annular peripheral wall extending between a front plate and a rear plate and a rotor positioned therein the housing. In another aspect, a drive shaft can be rotatably mounted therein the stationary housing, and an end of the drive shaft can extend through the rear plate. The rotor can be mounted to the drive shaft. In another aspect, the rotor can comprise an annular hub and a plurality of blades extending radially outward from the hub. In still another aspect, at least portions of the pump that contact a fluid, such as the rotor hub, the blades of the rotor, an inner periphery of the annular peripheral wall, and the like, can define a texture configured to reduce drag as the fluid passes over the textured surface, thereby reducing frictional losses. In another aspect, the liquid ring pump can further comprise a rotating or stationary sleeve or liner inside the housing. In such an arrangement, the texture can be defined on the inner and/or outer surfaces of the rotating sleeve.

[0007] Other systems, methods, features, and advantages of the liquid ring pump of the present application will be or become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate certain aspects of the instant invention and together with the description, serve to explain, without limitation, the principles of the invention. Like reference characters used herein indicate like parts throughout the several drawings. [0009] FIG. 1 is a cross-sectional view of an illustrative liquid ring pump of a flat sided design. It is of course contemplated that aspects of the present application can also apply to conical liquid ring pump designs.

[0010] FIG. 2 is a cross-sectional view of the pump of FIG.1 taken along line 2-2 of FIG. 1.

[0011] FIG. 3 is a cross-sectional view of an illustrative liquid ring pump having a liner.

[0012] FIG. 4 illustrates a textured surface of the present application, according to one aspect.

[0013] FIG. 5 is a cross-sectional view of a textured surface, according to one aspect.

[0014] FIG. 6 is a plan view of a portion of an array of dimples of a textured surface, according to one aspect.

DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention can be understood more readily by reference to the following detailed description, examples, drawings, and claims, and their previous and following description. However, before the present devices, systems, and/or methods are disclosed and described, it is to be understood that this invention is not limited to the specific devices, systems, and/or methods disclosed unless otherwise specified, as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

[0016] The following description of the invention is provided as an enabling teaching of the invention in its best, currently known embodiment. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made to the various aspects of the invention described herein, while still obtaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be obtained by selecting some of the features of the present invention without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations to the present invention are possible and can even be desirable in certain circumstances and are a part of the present invention. Thus, the following description is provided as illustrative of the principles of the present invention and not in limitation thereof. [0017] As used in the specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a dimple" includes two or more such dimples, and the like.

[0018] Ranges can be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as "about" that particular value in addition to the value itself. For example, if the value " 10" is disclosed, then "about 10" is also disclosed. It is also understood that when a value is disclosed that "less than or equal to" the value, "greater than or equal to the value" and possible ranges between values are also disclosed, as appropriately understood by the skilled artisan. For example, if the value "10" is disclosed then "less than or equal to 10" as well as "greater than or equal to 10" is also disclosed. It is also understood that throughout the application, data is provided in a number of different formats and that this data represents endpoints and starting points, and ranges for any combination of the data points. For example, if a particular data point "10" and a particular data point "15" are disclosed, it is understood that greater than, greater than or equal to, less than, less than or equal to, and equal to 10 and 15 are considered disclosed as well as between 10 and 15. It is also understood that each unit between two particular units are also disclosed. For example, if 10 and 15 are disclosed, then 1 1 , 12, 13, and 14 are also disclosed.

[0019] As used herein, the terms "optional" or "optionally" mean that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

[0020] The present invention can be understood more readily by reference to the following detailed description of embodiments of the invention and the Examples included therein and to the Figures and their previous and following description.

[0021] Although the principles of this invention are equally applicable to different types of fluid pumps and/or compressors, such as positive displacement pumps, centrifugal pumps, and the like, this invention will be described in the context of liquid ring pumps. Similarly, W

although the principles of this invention are equally applicable to pumps having any number of intake and compression zones alternating in the circumferential direction around the pump, the invention will be described in the context of pumps having only one intake zone and one compression zone in the circumferential direction. The invention is also applicable to any stage or stages of multistage pumps (i.e., pumps which discharge gas from one stage to the intake of another stage), but again, the invention will be fully understood from the following explanation of its application to single-stage pumps.

[0022] A conventional flat sided liquid ring pump 10 is illustrated in Figures 1 -3. The pump comprises a stationary housing 12 having an annular peripheral wall 14 extending between substantially parallel, spaced, front (or port) plate 16 and rear plate 18. In conventional conical and cylindrically ported liquid ring pump designs, the annular peripheral wall 14 of the housing can extend between a front and rear rotor shroud 29, 28 and cone (or cylinder) seat arrangement. The pump further comprises a rotor 20 rotatably mounted in the housing 12 by means of a drive shaft 22 which extends through the rear plate 18. The shaft and rotor can be driven to rotate about a longitudinal axis of the shaft by any suitable drive means (not shown), such as an electric motor and the like.

[0023] The rotor 20 comprises an annular rotor hub 24 connected to the drive shaft 22, a plurality of blades 26 extending radially outward from the hub in planes substantially parallel to the axis of the shaft 22, and a disc-like rear shroud 28 also extending radially outward from the hub in a plane substantially perpendicular to the axis of drive shaft 22 so as to connect the rear portions of all of the rotor blades 26. The rotor can further comprise a disc-like front shroud 29 connecting the front portion of the blades 26. The rotor 20 can be held on the shaft 22 by a rotor locking nut 23b. The rotor 20 is located eccentrically in the housing 12 so that an outer periphery 21 of the rotor is closer to an inner periphery 15 of the annular housing wall 14 at some positions than at others. Although the rotor blades are shown as being substantially straight in Figures 1 and 2, the blades 26 can alternatively be curved or hooked either forward or backward relative to the direction of rotor rotation in the manner known to those skilled in the art.

[0024] A quantity of working liquid is maintained in the housing 12 so that when the rotor 20 is rotated as indicated by the arrow 30 in Figure 1, the rotor blades 26 engage the working liquid and form it into a re-circulating annular ring around the inner periphery 15 of annular housing wall 14. The approximate inner boundary or surface of this liquid ring is represented in Figures 1 and 2 by the dashed lines 32. [0025] As can be seen in Figure 1, because the rotor 20 is mounted eccentrically relative to the housing wall 14, and hence is also eccentric to the liquid ring, the rotor blades 26 extend farther into the liquid in some positions that they do in other positions. For example, on the left-hand side of the pump as viewed in Figure 1 , the inner surface 32 of the liquid ring gradually diverges from the rotor hub 24 in the direction of rotor rotation. Accordingly, in that portion of the pump (known as the gas intake zone) the working spaces bounded by adjacent rotor blades 26, the rotor hub 24, and the inner surface 32 of the liquid ring gradually increase in volume in the direction of rotor rotation. On the right-hand side of the pump as viewed in Figure 1 , the inner surface 32 of the liquid ring gradually converges toward rotor hub 24 in the direction of rotor rotation. Accordingly, in that portion of the pump (known as the gas compression zone) the working spaces bounded by adjacent rotor blades 26, the rotor hub 24, and the inner surface 32 of the liquid ring gradually decrease in volume in the direction of rotor rotation.

[0026] In operation, gas to be pumped is admitted to the intake zone of the pump via an intake port 34 in the front plate 1 on flat sided liquid ring pump designs. In conical liquid ring pumps, instead of the front plate 16, ports can be defined in a conical member which protrudes into the rotor with a matching taper and controlled clearances. Similarly, in cylindrically ported liquid ring pumps, instead of the front plate 16, ports can be defined in a cylindrical member which protrudes into the rotor with controlled clearances. The gas can be supplied to the pump via intake conduit 44 and intake plenum 42. The gas is pulled into the pump by the expansion of the working spaces in the intake zone, and is subsequently compressed by the contraction of the working spaces in the compression zone. The compressed gas is then discharged from the pump via a discharge port 36 in the front plate 16. The compressed gas can be conveyed from the pump via discharge plenum 46 and discharge conduit 48.

[0027] In another embodiment, the liquid ring pump 10 can further comprise an annular liner 70 comprising a cylindrical body disposed inside the housing 12 adjacent the inner periphery 15 of the annular housing wall 14 so that the liner is free to rotate about the longitudinal axis of the shaft 22. In one aspect, the liner can be a rotating liner or a stationary liner. The liner has an inner surface 72 configured to contact the working liquid and an outer surface 74 adjacent the inner periphery 15 of the annular housing wall 14.

[0028] A source of energy loss, and therefore inefficiency, in liquid ring pumps is fluid friction between the re-circulating liquid ring and the surfaces of the pump in contact with the liquid ring, including the inner periphery 15 of the housing wall 14, and portions of the blades 26 of the rotor. If a liner 70 is present, fluid friction between the re-circulating liquid ring and the surfaces of the pump 10 in contact with the liquid ring, including an inner surface of the liner and portions of the blades 26 of the rotor can be a source of energy loss.

Additionally, in the case when a liner is present, fluid friction can be present between an outer surface 74 of the liner 70 and the inner periphery 15 of the annular housing wall as the liner rotates. A further source of energy loss, and therefore inefficiency, in liquid ring pumps is fluid friction between the gas being pumped and the surfaces of the pump in contact with the gas, including portions of the rotor blades 26 and the rotor hub 24, the intake port 34, the discharge port 36, associated conduits, and the like.

[0029J In one aspect, surface treatments can be applied to any or all of the surfaces of the pump 10 in contact with a fluid (the wetted surfaces), such as for example and without imitation, the inner periphery 15 of the housing wall, the rotor hub, the blades of the rotor, the inner and/or outer surfaces of the liner 70, and the like. In another aspect, the surface treatment can comprise a texture comprising a plurality of dimples 50. In still another aspect, the texture can comprise a plurality of cavities, grooves, slots, notches, and the like.

[0030] In one aspect, as illustrated in Figure 4, each dimple of the plurality of dimples can be substantially spherical in shape. Figure 5 illustrates a cross-sectional view of a plurality of dimples having a substantially spherical shape, according to one aspect. It is contemplated, however, that the dimples 50 can be other shapes, such as riblets, polyhedrons, ellipsoids, paraboloids, hyperboloids of revolution, and the like. In still another aspect, it is contemplated that the dimple shapes, when view in cross-section, can be substantially square, substantially rectangular, substantially trapezoidal, and the like. In another aspect, at least a first dimple or first plurality of dimples can have a first shape (such as spherical), and at least a second dimple or second plurality of dimples can have a second shape (such as ellipsoid). Thus, the plurality of dimples 50 can comprise any number of dimples with each dimple having a different shape or the same shape as the other dimples.

[0031] In another aspect, each dimple 50 of the plurality of dimples can have a size (such as, a diameter, for a spherical-shaped dimple) of about 0.185 inches. However, it is contemplated that each dimple can have a size less than or greater than 0.185 inches. For example, each dimple can have a size of about 0.005 inches, 0.010 inches, 0.020 inches, 0.030 inches, 0.040 inches, 0.050 inches, 0.060 inches, 0.070 inches, 0.080 inches, 0.090 inches, 0.100 inches, 0.1 10 inches, 0.120 inches, 0.130 inches, 0.140 inches, 0.150 inches, 0.160 inches, 0.170 inches, 0.180 inches, 0.190 inches, 0.200 inches, 0.210 inches, 0.220 inches, 0.230 inches, 0.240 inches, 0.250 inches, 0.260 inches, 0.270 inches, 0.280 inches, 0.290 inches, 0.300 inches, 0.320 inches, 0.340 inches, 0.360 inches, 0.380 inches, 0.400 inches, 0.420 inches, 0.440 inches, 0.460 inches, 0.480 inches, 0.500 inches, 0.550 inches, 0.600 inches, 0.650 inches, 0.700 inches, 0.750 inches, 0.800 inches, 0.850 inches, 0.900 inches, 0.950 inches, 1.000 inches or greater than 1.000 inches. In another aspect, it is contemplated that each dimple of the plurality of dimples can have the same size or a different size than other dimples 50. Thus, in one aspect, the plurality of dimples can comprise any number of dimples with each dimple having a different size or the same size as the other dimples.

[0032] In another aspect, each dimple of the plurality of dimples can have a depth of about 0.038 inches. However, it is contemplated that each dimple can have a depth less than or greater than 0.038 inches. For example, each dimple 50 can have a depth of about 0.002 inches, 0.004 inches, 0.006 inches, 0.008 inches, 0.010 inches, 0.012 inches, 0.014 inches, 0.016 inches, 0.018 inches, 0.020 inches, 0.022 inches, 0.024 inches, 0.026 inches, 0.028 inches, 0.030 inches, 0.032 inches, 0.034 inches, 0.036 inches, 0.038 inches, 0.040 inches, 0.042 inches, 0.044 inches, 0.046 inches, 0.048 inches, 0.050 inches, 0.055 inches, 0.060 inches, 0.065 inches, 0.070 inches, 0.075 inches, 0.080 inches, 0.085 inches, 0.090 inches, 0.095 inches, 0.100 inches, 0.125 inches, 0.150 inches, 0.175 inches, 0.200 inches, 0.225 inches, 0.250 inches, 0.275 inches, 0.300 inches, 0.325 inches, 0.350 inches, 0.375 inches, 0.400 inches, 0.425 inches, 0.450 inches, 0.475 inches, 0.500 inches or greater than 0.500 inches. In another aspect, it is contemplated that each dimple of the plurality of dimples can have the same depth or a different depth than other dimples 50. Thus, in one aspect, the plurality of dimples can comprise any number of dimples with each dimple having a different depth or the same depth as the other dimples.

[0033] In another aspect, the surface can have a dimple density (dimples per unit area) of about 26.5 dimples per square inch ("d/in ² "). However, it is contemplated that the surface can have a dimple density of less than or greater than 26.5 d/in ² . For example, the surface can have a dimple density of about 0.5 d/in ² , 1 d/in ² , 2 d/in ² , 3 d/in ² , 4 d/in ² , 5 d/in ² , 7.5 d/in ² , 10 d/in ² , 12.5 d/in ² , 15 d/in ² , 17.5 d/in ² , 20 d/in ² , 22.5 d/in ² , 25 d/in ² , 27.5 d/in ² , 30 d/in ² , 32.5 d/in ² , 35 d/in ² , 37.5 d/in ² , 40 d/in ² , 42.5 d/in ² , 45 d/in ² , 50 d in ² , 55 d/in ² , 60 d/in ² , 65 d/in ² , 70 d/in ² , 75 d/in ² , 80 d/in ² , 85 d/in ² , 90 d/in ² , 95 d/in ² , 100 d/in ² , 125 d/in ² , 150 d/in ² , 175 d/in ² , 200 d/in ² or greater than 200 d/in ² . In one aspect, dimple density can depend 201

on dimple size, however, the dimple arrangement and spacing between dimples can also affect dimple density.

[0034] In one aspect, the spacing between each dimple 50 of the plurality of dimples can be about 0.015 inches. However, it is contemplated that the spacing between each dimple of the plurality of dimples can be less than or greater than 0.015 inches. For example, the spacing between each dimple can be about 0.002 inches, 0.004 inches, 0.006 inches, 0.008 inches, 0.010 inches, 0.012 inches, 0.014 inches, 0.016 inches, 0.018 inches, 0.020 inches, 0.022 inches, 0.024 inches, 0.026 inches, 0.028 inches, 0.030 inches, 0.032 inches, 0.034 inches, 0.036 inches, 0.038 inches, 0.040 inches, 0.042 inches, 0.044 inches, 0.046 inches, 0.048 inches, 0.050 inches, 0.055 inches, 0.060 inches, 0.065 inches, 0.070 inches, 0.075 inches, 0.080 inches, 0.085 inches, 0.090 inches, 0.095 inches, 0.100 inches, 0.125 inches, 0.150 inches, 0.175 inches, 0.200 inches, 0.225 inches, 0.250 inches, 0.275 inches, 0.300 inches, 0.325 inches, 0.350 inches, 0.375 inches, 0.400 inches, 0.425 inches, 0.450 inches, 0.475 inches, 0.500 inches, or greater than 0.500 inches. In another aspect, it is contemplated that the spacing between each dimple 50 of the plurality of dimples can vary from one dimple to another dimple. Thus, in one aspect, the spacing between a first and second dimple can be different that the spacing between the second and a third dimple.

{0035] In one aspect, the plurality of dimples 50 can be arranged in an array 52 having a plurality of substantially linear rows 54 of dimples, as illustrated in Figures 4 and 6. In another aspect, dimples of adjacent successive rows can be substantially offset in a direction perpendicular to the linear rows, also as illustrated in Figures 4 and 6. In another aspect, dimples 50 of adjacent successive rows can be substantially aligned in a direction perpendicular to the linear rows.

[0036] In another aspect, the plurality of dimples 50 can be arranged in other patterns, such as for example and without limitation, riblets, tetrahedral, pentahedral, hexahedral, heptahedral, triacontahedron, icosahedral, and dodecahedral. In still another aspect, the plurality of dimples can be arranged randomly on the desired surface of the pump 10. In another aspect, a first pattern of dimples can be formed on at least a portion of a surface of the pump, and a second pattern of dimples 50 can be formed on at least a portion of a surface of the pump. Thus, it is contemplated that the plurality of dimples 50 can be arranged in the same pattern and/or different patterns on surfaces of the pump.

[0037] As previously discussed, each dimple of the plurality of dimples can have a predetermined depth, size, and/or shape, according to one aspect. It is also contemplated that, the plurality of dimples 50 could comprise a plurality of varying sized or shaped dimples. In another aspect, each dimple of the plurality of dimples can vary in respective scale and/or shape. For example and not meant to be limiting, adjacent dimples 50 could have different relative scaled dimensions. Thus, a "large" dimple can be adjacent a "small" dimple, such that a front view could be of a row of the adjoining dimples that have an inverse staggered saw tooth appearance.

[0038] In one aspect, the surface texture can be applied to at least portions of any or all of the wetted surfaces of the pump 10. For example, the plurality of dimples 50 can be applied to the inner periphery 15 of the housing wall, portions of the blades of the rotor, the inner and/or outer surfaces of the liner 70, if present, the rotor hub 24, the intake and discharge ports, and/or associated conduits.

[0039] In another aspect, the surface texture can be applied to at least portions of any or all of the wetted surfaces of the pump 10 in order to reduce factional losses between the fluids therein the pump and the wetted surface of the pump by about 1%, 2%, 3%, 4%, 5%,6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%,40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%. In another aspect, the surface texture can be dimensioned to reduce frictional losses between the fluids therein the pump and the wetted surface of the pump by about 1%, 2%, 3%, 4%, 5%,6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%,40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%.

[0040] In one aspect, the textured surfaces of the pump 10 in contact with a fluid can act as a means of controlling separation of the boundary layer. In another aspect, the textured surfaces of the pump in contact with a fluid can act as a means of controlling separation of the boundary layer by forming at least one embedded cavity vortex therein each dimple 50 such that the vortices generated influence localized ring velocity, reduce viscous drag and improve pump efficiency. The formation of embedded cavity vortices, or small localized regions of separation within the surface, allow the outer boundary layer flow to skip over the dimples in the textured surface. Thus, the use of textured surfaces, capable of imposing partial-slip flow conditions at the surface due to the formation of embedded vortices, can ^* achieve drag reduction via separation control. In another aspect, the effect of the textured surface acts to reduce fluid drag over the textured surfaces of the pump 10, thereby increasing the efficiency of the pump.

[0041] The preceding description is provided as an enabling teaching in its best, currently known embodiment. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made to the various aspects of the invention described herein, while still obtaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be obtained by selecting some of the features of the present invention without utilizing other features. The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or acts for performing the functions in combination with other claimed elements as specifically claimed.

[0042] Accordingly, those who work in the art will recognize that many modifications and adaptations to the present invention are possible and can even be desirable in certain circumstances and are a part of the present invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. Thus, the preceding description is provided as illustrative of the principles of the present invention and not in limitation thereof. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.