Deswirl mechanisms and roller bearings in an axial thrust equalization mechanism for liquid cryogenic turbomachinery
Vane, fin, and hole arrangements establish a predetermined reduced swirl at the inlet of mechanical seals and the inlet of a variable axial orifice gap which act in harmony as an axial thrust equalizing system for use in liquid cryogenic turbines and pumps. In said establishment the stiffness, damping, and inertia in said seal in conjunction with said variable orifice gap is manipulated, including the destabilizing cross-coupled stiffness which is reduced. Said seal is of either labyrinth annular type formed by a plurality of teeth, annular smooth, or a plurality diamond annular surface pattern. Said variable orifice gap is smooth. Liquid for the axial thrust equalizing seal is initially bled from the main to pass through a preset deswirl mechanism. The deswirl mechanism consists of either a plurality of vanes, fins, grooves, or circular holes that guide liquid radial inward before passing through said mechanical seal. After exiting the seal said liquid passes through a second deswirl mechanism consisting of a plurality of vanes, fins, or grooves before entering a variable axial orifice gap. The variable orifice moves in axial position to variably restrict balancing liquid and generate backpressure in the pressure chamber to balance the axial thrust caused by a plurality of impellers on the same single shaft. After passing through the variable orifice the bleed liquid can pass past a sealed lubricated roller bearing for heat exchange to cool said bearing with the cryogenic liquid along grooves in a bearing liner. Alternatively the liquid can also pass directly through an open unsealed bearing for cooling.
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This Application is related to U.S. Provisional Patent Application Ser. No. 60/920,618 filed Mar. 29, 2007 entitled DESWIRL MECHANICS AND ROLLER BEARINGS IN AN AXIAL THRUST EQUALIZATION MECHANISM FOR LIQUID CRYOGENIC TURBOMACHINERY, which is incorporated herein by reference in its entirety, and claims any and all benefits to which it is entitled therefrom.
FIELD OF THE INVENTIONThe present invention relates to liquid cryogenic centrifugal pumps and turbines of the submerged motor or generator type.
BACKGROUND OF THE INVENTIONVertical cryogenic submerged motor pumps and submerged generator turbines operate in the liquefied cryogenic gases industry. They are most prominent in the liquid hydrocarbon industry for liquefied natural gas, liquefied ethane gas, and liquefied propane gas. U.S. Pat. No. 5,659,205 to Weisser, which is hereby incorporated by reference in its entirety herein, teaches that due to the low cryogenic temperatures this style of pump and turbine operates with the axial thrust of the rotating assembly totally equalized to zero. U.S. Pat. No. 6,441,508 to Hylton is also hereby incorporated by reference in its entirety herein.
To achieve this, a conventional axial thrust equalizing mechanism such as shown in
The power rating of liquid cryogenic pumps and turbines in high pressure applications continues to grow as motivated by customer demands. This translates to higher power concentration machinery. So the axial thrust mechanism must balance larger thrust levels. Greater radial thrust levels are also experienced which the seals must react to avoid overly larger shaft deflections and overly large shaft diameters to compensate. Thus, means are sought to increase the stiffness of impeller flow induced reaction forces to stiffen the shaft. Increasing the shaft damping is also beneficial. Benckert, H., et al. teach in “Flow Induced Spring Coefficients of Labyrinth Seals for Application in Rotor Dynamics” published 1980, which is hereby incorporated by reference in its entirety, that means are also sought to reduce the well documented destabilizing cross-coupled stiffness in the mechanical seals. Overall increasing the stiffness and damping while decreasing the cross-coupled stiffness will reduce rotordynamic whirl and vibrations. This can be seen from first principles with the equation of motion applied to a rotating assembly experiencing small displacements δ in the x and y direction written as follows:
Note: Both the direct coupled and cross coupled terms are represented in the stiffness (k), damping (c), and inertia mass (m) matrix. For small displacements, the coefficients in these equations are taken as linear. Separating the forcing contributions in the absolute reference frame results in the following:
The force contributions are dividing into steady and unsteady. The unsteady force contribution is further subdivided into whirl and none whirl portions. The whirl contribution will be taken as a circular orbit that experiences small periodic displacements of δ in x and y so δ=δo+iy and δ=δo exp(iωwt). In this relation, ωw is the impeller whirl frequency. Now, expanding the previous equation for the whirl terms gives the following:
It is now more convenient and intuitive to write this equation in dimensionless form as follows:
The * designates use of the dimensionless quantities with F*=F/πρR23B2ω2, x*=x/R2, dx*/dt=(dx/dt)/R2ω, and dx2*/dt=(d2x/dt2)/R2ω2. The dimensionless stiffness, damping and added mass coefficients used are k*ij=kij/πρR22B2ω2, c*ij=cij/πρR22B2ω, m*ij=mij/πρR22B2. This expression gives the x, y component of the forces but the greater interest for turbomachinery vibrations lies in the tangential and radial forces from the rotating assembly center. So we convert to polar coordinates with F*r+iF*θ=(F*x+iF*y)exp(−iωwt) and get the following equation:
Now the rotation of the coefficients about the x, y axis is taken with isometry, which most whirl related test data supports, meaning the terms with subscript xx equal the yy terms and the subscript xy terms equal the negative yx terms. This then gives the following equation:
For the circumferential force if F*θ is negative, in the reverse direction of the impeller whirl rotation, an impeller whirl stabilizing force is experienced. If F*θ is positive, in the direction of whirl, this destabilizes the impeller by eliciting greater whirl. The stability boundary is found by taking the value of F*θ=0 and mxy as negligible in the previous equation to give ωw/ω=k*xy/c*xx as the whirl ratio limit. Taking mxy as negligible with respect to the stiffness and damping is reasonable for most but not all rotordynamic problems, although it does illustrate the origins of the whirl ratio limit. In dimensional form, this tangential whirl ratio limit as a stability condition then simplifies to the following:
Therefore, the tangential stability whirl ratio limit is a balance between cross coupled stiffness forces kxy that drive the whirl and damping forces cxxω that oppose the whirl. For a constant angular frequency with a whirl larger than (ωw/ω)θ limit, the tangential force acts in a stabilizing manner. For a constant angular frequency with a whirl smaller than (ωw/ω)θ limit the tangential force acts in a destabilizing manner, unless the whirl orbit is backwards in which case this is stabilizing. Hence the desire to decrease the cross-coupled stiffness kxy (and increase the direct damping) is beneficial for improved whirl stability and reduced rotordynamic vibrations. Applying this finding, several research institutions and patents such as U.S. Pat. No. 5,190,440 to Maier have applied swirl brakes to labyrinth seals in high temperature gas compressors.
It is this premise applied in conjunction with a thrust equalization mechanism that is unique for liquid cryogenic pumps and turbines. In so doing the benefit of a reduced destabilizing cross-coupled stiffness in the seal and balance mechanism is gained. Further, the direct coupled stiffness kxx is increased in the seal along with an increase in the direct coupled cxx damping. The reduced swirl in the variable orifice of the balance mechanism also provides an improved equalization of the axial thrust with unwanted flow separation regions avoided in the orifice gap. So several advancements in thrust balancing devices for liquid cryogenic pumps and turbines are addressed with the claims of this patent.
Accordingly, there are provided herein several unique improvements to the axial thrust equalizing mechanism which address the deficiencies of preswirl in the prior art of submerged motor liquid cryogenic pumps and turbines. The invention reduces the destabilizing cross-coupled stiffness while concurrently increasing the direct coupled stiffness and direct coupled damping in the mechanical seals. This is achieved within the framework of an improved axial thrust equalization. The seals themselves consist of either labyrinth type, smooth type, or surface pattern type such as diamond surface mesh. Holes are also claimed to locally inject fluid with zero swirl and stop any residual swirling liquid seal flow.
Another embodiment provides deswirl fins, vanes or grooves upstream of the variable orifice used for the thrust equalization. These ensure the variable orifice receives liquid with adjusted prespecified preswirl which may be zero with the flow directed primarily radially. This avoids fluid instabilities including separation near the orifice which can suddenly collapse or form giving the thrust balance system a rapid change in balance position. The predominately radial flow liquid direction also improves the capacity of balancing higher thrust levels needed for more powerful pumps and turbines.
A further embodiment provides both a sealed and unsealed roller bearing operating in conjunction with the axial thrust equalizing mechanism and the deswirl devices. Currently unsealed roller bearings are the prior art. Sealed bearings packed with lubricants are not used in cryogenic applications for fear of freezing. Recent advances in synthetic grease now make available unfrozen grease down to temperatures of −60° C. This is applicable to liquid propane and butane pumps and turbines, particularly in situations where the fluid is dirty and can cause reduced bearing life for an unsealed bearing. For situations where the fluid temperature is lower, a bearing heater and sensor are embodied which briefly preheat the frozen grease before start-up. After start-up, the bearing heater may no longer be needed as the bearing itself may generate sufficient heat.
A last embodiment provides deswirl vanes, fins, or holes on the seals on the plurality of impeller eyes and interstages. These are also useful to reduce the cross-coupled stiffness while concurrently increasing the direct coupled stiffness and direct coupled damping. Surface patterns such as diamond mesh are also utilized with a smooth rotating surface and a inlet deswirl mechanism for the same rotordynamic benefit.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.
Benefits and features of the invention are made more apparent with the following detailed description of a presently preferred embodiment thereof in connection with the accompanying drawings, wherein like reference numerals are applied to like elements.
The description that follows is presented to enable one skilled in the art to make and use the present invention, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principals discussed below may be applied to other embodiments and applications without departing from the scope and spirit of the invention. Therefore, the invention is not intended to be limited to the embodiments disclosed, but the invention is to be given the largest possible scope which is consistent with the principals and features described herein.
It will be understood that while numerous preferred embodiments of the present invention are presented herein, numerous of the individual elements and functional aspects of the embodiments are similar. Therefore, it will be understood that structural elements of the numerous apparatus disclosed herein having similar or identical function may have like reference numerals associated therewith.
Referring to
The case of a centrifugal pump is described realizing the reverse flow equivalent nature of a centrifugal turbine for which the claims also hold. It will be understood that for purposes of the current application, an LNG pump may be used to increase the pressure of the liquid LNG, while a turbine may act to lower the pressure of the liquid LNG. While the terms “pump” and “turbine” may be used interchangeably in certain portions of the current application, in general the primary differences between the two are described as follows: In the case of an LNG pump used to increase the pressure of the liquid LNG, flow of the main stream of liquid LNG will be into the pump at fluid inlet 25, across impeller portion 2 located toward the radial periphery of the assembly, across return vane 5, down and up through diffuser housing 3 and out the exhaust 4 at a higher pressure than at the fluid inlet 25. Flow is from LEFT to RIGHT through the pump. Conversely, in the case of a turbine which lowers the overall pressure of the liquid LNG, flow is from RIGHT to LEFT through the turbine.
The centrifugal pump comprises a rotatable shaft 1 rotating a plurality of impellers 2 with fluid leaving the impeller to be diffused in the diffuser 3 and then passed to exhaust lines 4 which surround a submerged motor housing 10. Fluid enters the impeller eye from a return-vane 5 enclosed in a diffuser housing 6 all of which are encompassed in a pump housing 7. The preceding impeller hub leakage is contained with an annular mechanical hub seal 8 which consists of a labyrinth and a smooth seal arrangement. The impeller eye is sealed with a mechanical shroud seal 9 using a shroud labyrinth or smooth seal arrangement. The impeller is circumferentially locked to the rotatable shaft with a key 14 and axially a locknut 12. Behind the highest pressure impeller is the axial thrust equalizing mechanism consisting of a high pressure chamber 150 and mechanical seal 100 through which pressurized fluid passes to the low pressure chamber 204 and thrust plate 200. After passing through this low pressure chamber an axial variable orifice gap 203 is traverse by the thrust equalizing liquid and passes into the thrust plate pocket 16 from where it exits the pocket through motor housing holes 19 or through the roller bearing 17 or through the bearing liner cooling holes 300. The roller bearing is axially limited in travel with a locknut 15 and washer 22 and spacer 23. Liquid which passes through the roller bearing or bearing linear then passes through a motor housing bushing 21 before entering the submerged cryogenic motor or generator cavity 20.
The destabilizing cross-coupled stiffness is a large influence on the forces that arise in mechanical seals and if too large can lead to excessive synchronous and subsynchronous vibrations in centrifugal pump and turbines.
The deswirl mechanisms claim in this invention serve two purposes. Firstly they act to deswirl liquid at the inlet of the mechanical seals which make up part of the thrust equalizing mechanism. Secondly the deswirl mechanisms at the inlet of the variable axial orifice gap, also part of the axial thrust equalizing mechanism, removes unwanted circumferential liquid velocity to avoid flow separation pockets which gives a more stable axial thrust equalization than conventional liquid cryogenic systems. Together the mechanical seals and variable axial orifice gap act in harmony to equalize the axial thrust on the rotating shaft. The present invention provides means for achieving the desirable inlet swirl reduction at two key locations in the axial thrust equalizing mechanism of cryogenic pumps and turbines.
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The foregoing description is intended to illustrate the present invention. Those of ordinary skill will be able to envisage certain additions, deletions or modifications to the described embodiments which do not depart from the spirit or scope of the invention as defined by the claims herein.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Although any methods and materials similar or equivalent to those described can be used in the practice or testing of the present invention, the preferred methods and materials are now described. All publications and patent documents referenced in the present invention are incorporated herein by reference.
While the principles of the invention have been made clear in illustrative embodiments, there will be immediately obvious to those skilled in the art many modifications of structure, arrangement, proportions, the elements, materials, and components used in the practice of the invention, and otherwise, which are particularly adapted to specific environments and operative requirements without departing from those principles. The appended claims are intended to cover and embrace any and all such modifications, with the limits only of the true purview, spirit and scope of the invention.
Claims
1. A pump with thrust equalizing mechanism for liquid cryogenic materials capable of operating at cryogenic liquid temperatures, the pump comprising, in part, a housing, a low pressure annular chamber in said housing to contain a low pressure liquid, a high pressure annular chamber in said housing to contain high pressure liquid, a rotating shaft concentric in said housing, said rotatable shaft constituting a rotatable element with a plurality of pump impellers mounted and rotating on a shaft connected to a submerged electric motor or generator, a liquid flow driven through a mechanical seal by a pressure difference from said high pressure chamber to said low pressure chamber, a first deswirl mechanism located inside said high pressure chamber arranged upstream of said mechanical seal to preset the preswirl of the liquid thrust equalizing flow that enters said seal to a predetermined predominantly radial inward direction, said first deswirl mechanism having largest radius inlet exposed to said high pressure chamber inlet, said first deswirl mechanism having outlet exposed to said mechanical seal inlet, such that said first deswirl mechanism deswirls said liquid thrust balancing flow swirl which was imparted by said rotating impeller to provide said seal with a preset inlet liquid flow swirl which may be zero in radial inward direction only, said mechanical seal exits liquid to said low pressure chamber, and a second deswirl mechanism positioned concentric with the rotatable shaft, said second deswirl mechanism arranged in a radial orientation upstream of an variable axial clearance to permit impeller rotation about said shaft center.
2. The pump of claim 1, wherein the first deswirl mechanism comprises a plurality of vanes arranged about the circumference along the said rotatable shaft center, the plurality of vanes lying oriented in predetermined flow directions relative the location of the rotatable shaft center.
3. The pump of claim 2, wherein the plurality of vanes are pivotable and can be locked into place in a predetermined position.
4. The pump of claim 3, further comprising a controller and associated actuator, wherein the associated actuator can be used to control the direction of the plurality of pivotable vanes.
5. The pump of claim 1, wherein the first deswirl mechanism comprises a plurality of fins arranged about the circumference along the said rotatable shaft center, the plurality of fins lying oriented in predetermined flow directions relative the location of the rotatable shaft center.
6. The pump of claim 5, wherein the plurality of fins are pivotable and can be locked into place in a predetermined position.
7. The pump of claim 6, further comprising a controller and associated actuator, wherein the associated actuator can be used to control the direction of the plurality of pivotable fins.
8. The pump of claim 1, wherein the first deswirl mechanism comprises a plurality of grooves arranged about the circumference along the said rotatable shaft center, the plurality of grooves lying oriented in predetermined flow directions relative the location of the rotatable shaft center.
9. The pump of claim 1, further comprising a primary plurality of liquid flow bypass passageway holes exiting said high pressure chamber, each of said liquid flow bypass passageway holes extending downstream to said seal with injection of deswirled liquid into the seal near said seal inlet at some intermediate pressure between that in said low high chamber and said low pressure chamber, said primary plurality of bypass holes having a predetermined radius.
10. The pump of claim 9, further comprising a second plurality of liquid flow bypass passageway holes exiting said high pressure chamber, each of said liquid flow bypass passageway holes extending downstream to said seal with injection of deswirled liquid into the seal near said seal inlet at some intermediate pressure between that in said low high chamber and said low pressure chamber, said second plurality of bypass holes having a second predetermined radius.
11. The pump of claim 1, wherein the mechanical seal is an annular mechanical seal to achieve pressure drop from said high pressure chamber to said low pressure chamber across said seal with rotating and stationary portions which is dependant on liquid flow rate through said seal, said seal rotating portion is a rotating labyrinth annulus positioned concentric with said rotatable shaft mounted on the highest pressure impeller stage, said labyrinth annulus consists of a plurality of circumferential grooved teeth with land and valley lengths, said seal stationary portion is smooth, distance between the rotating and stationary seal is the wear ring clearance wherein said liquid pressure drop results.
12. The pump of claim 1, wherein the mechanical seal is an annular mechanical seal to achieve pressure drop from said high pressure chamber to said low pressure chamber across said mechanical seal with rotating and stationary portions which is dependant on liquid flow rate through said seal, said seal rotating portion is a smooth annulus positioned concentric with said rotatable shaft mounted on the highest pressure impeller stage, said seal stationary portion is a diamond surface pattern to act as a circumferential liquid flow deswirl mechanism, the distance between the rotating and diamond surface pattern stationary seal is the wear ring clearance wherein said liquid pressure drop results.
13. The pump of claim 9, wherein the mechanical seal is an annular mechanical seal to achieve pressure drop from said high pressure chamber to said low pressure chamber across said seal with rotating and stationary portions which is dependant on liquid flow rate through said seal, said seal rotating portion is a rotating labyrinth annulus positioned concentric with said rotatable shaft mounted on the highest pressure impeller stage, said labyrinth annulus consists of a plurality of circumferential grooved teeth with land and valley lengths, said seal stationary portion is smooth, distance between the rotating and stationary seal is the wear ring clearance wherein said liquid pressure drop results.
14. The pump of claim 10, wherein the mechanical seal is an annular mechanical seal to achieve pressure drop from said high pressure chamber to said low pressure chamber across said seal with rotating and stationary portions which is dependant on liquid flow rate through said seal, said seal rotating portion is a rotating labyrinth annulus positioned concentric with said rotatable shaft mounted on the highest pressure impeller stage, said labyrinth annulus consists of a plurality of circumferential grooved teeth with land and valley lengths, said seal stationary portion is smooth, distance between the rotating and stationary seal is the wear ring clearance wherein said liquid pressure drop results.
15. The pump of claim 11 further comprising a second deswirl mechanism downstream of said liquid pressure drop apparatus comprising a plurality of fins to preset and adjust rotational swirl of said thrust equalizing liquid which exits said upstream seal and enters said low pressure chamber, itself upstream of a variable axial orifice gap.
16. The pump of claim 12 further comprising a second deswirl mechanism downstream of said liquid pressure drop apparatus comprising a plurality of fins to preset and adjust rotational swirl of said thrust equalizing liquid which exits said upstream seal and enters said low pressure chamber, itself upstream of a variable axial orifice gap.
17. The pump of claim 11 further comprising a second deswirl mechanism downstream of said liquid pressure drop apparatus comprising a plurality of vanes to preset and adjust rotational swirl of said thrust equalizing liquid which exits said upstream seal and enters said low pressure chamber, itself upstream of a variable axial orifice gap.
18. The pump of claim 12 further comprising a second deswirl mechanism downstream of said liquid pressure drop apparatus comprising a plurality of vanes to preset and adjust rotational swirl of said thrust equalizing liquid which exits said upstream seal and enters said low pressure chamber, itself upstream of a variable axial orifice gap.
19. The pump of claim 11 further comprising a second deswirl mechanism downstream of said liquid pressure drop apparatus comprising a plurality of grooves to preset and adjust rotational swirl of said thrust equalizing liquid which exits said upstream seal and enters said low pressure chamber, itself upstream of a variable axial orifice gap.
20. The pump of claim 12 further comprising a second deswirl mechanism downstream of said liquid pressure drop apparatus comprising a plurality of grooves to preset and adjust rotational swirl of said thrust equalizing liquid which exits said upstream seal and enters said low pressure chamber, itself upstream of a variable axial orifice gap.
21. The pump of claim 20 wherein the liquid cryogenic apparatus further comprises an axial gap of variable axial gap size capable of axial movement acting as a variable orifice to constitute a variable liquid flow restriction based on the axial location of said rotating shaft, the axial gap comprising a rotating and stationary smooth surface with a variable axial orifice gap, said rotating surface coupled to the neighboring highest pressure impeller, said rotating surface able to move axially acting as the variable side of a variable orifice, said rotating surface making up one side of a radially orientated axial gap, said stationary surface as the other side of a radially orientated variable axial orifice gap.
22. The pump of claim 21 further comprising a variable pressure chamber controlled with said variable axial orifice gap, the variable pressure chamber further comprising the second deswirl mechanism.
23. The pump of claim 22 further comprising a liquid cryogenic roller bearing assembly functioning in tandem and conjunction with said first and second liquid deswirl mechanisms and said variable axial orifice gap, the roller bearing assembly comprising an unsealed roller bearing cooled with thrust equalizing liquid flow flushing through, said unsealed bearing lubricated with a dry impregnated lubricant bearing cage, said unsealed bearing accepting a fraction of the thrust equalizing liquid from said variable orifice mechanism with remaining unwanted liquid flow bypassing, said unsealed bearing located concentric with outer race inside a bearing liner with a small radial clearance of between about 10 μm and about 60 μm to permit said unsealed bearing to move axially with said variable orifice gap, said bearing liner is fixed in a stationary housing.
24. The pump of claim 22 further comprising a liquid cryogenic roller bearing assembly functioning in tandem and conjunction with said first and second deswirl mechanisms and said variable axial orifice gap, the roller bearing assembly comprising a sealed roller bearing packed permanently with low temperature lubricant, said sealed bearing located with outer race concentric inside a bearing liner with a small radial clearance of between about 10 μm and about 60 μm to permit said sealed bearing to move axially with said variable orifice mechanism, said sealed bearing accepting no through liquid flow, said bearing liner fixed in a stationary housing, said bearing liner further having a plurality of grooved axial slots about the circumference to pass a fraction of liquid flow from said variable orifice mechanism for cooling, said sealed roller bearing apparatus with a bearing start-up heater located near said bearing liner, bearing temperature sensor mounted circumferentially about 180 degrees or more or less from said bearing heater, the pump further comprising a start-up delay control system whereby said bearing heater is activated to preheat said roller bearing lubricant to a predetermined temperature before start-up is permitted.
25. The pump of claim 22, wherein the cryogenic liquid mechanical seal assembly comprises a plurality of impeller eye wear rings functioning in conjunction and harmony with the first and second deswirl mechanisms as part of the thrust equalizing mechanism, the thrust equalizing mechanism comprising a rotating labyrinth seal with a plurality of circumferential grooved teeth on the rotating impeller wear ring, the thrust equalizing mechanism further comprising a stationary smooth surface which together with said rotating wear ring forms a radial clearance gap to seal impeller shroud leakage fluid, the thrust equalizing mechanism further comprising a plurality of tertiary deswirl mechanisms upstream of the seal.
26. The pump of claim 22, wherein the cryogenic liquid mechanical seal assembly comprises a plurality of impeller eye wear rings functioning in conjunction and harmony with the first and second deswirl mechanisms as part of the thrust equalizing mechanism in cryogenic liquids comprising a rotating annular smooth seal on the rotating impeller or rotating impeller wear ring, a stationary diamond pattern mesh surface which together with said rotating wear ring forms a radial clearance gap to seal impeller shroud leakage liquid and deswirl liquid in the clearance gap, the thrust equalizing mechanism further comprising a plurality of deswirl mechanisms upstream of the seal.
27. The pump of claim 1 further comprising a cryogenic liquid mechanical seal assembly on the plurality of impeller interstage bushings and wear rings functioning in conjunction and harmony with first and second deswirl mechanisms as part of the thrust equalizing mechanism, the mechanical seal assembly comprising a stationary smooth surface annular wear ring mounted in a fixed housing, a rotating labyrinth seal with a plurality of circumferential grooved teeth on a rotating impeller or rotating impeller annular wear ring which together with said stationary wear ring forms a radial clearance gap to seal interstage return liquid, the thrust equalizing mechanism further comprising a plurality of tertiary deswirl upstream of the seal.
28. A pump of claim 1 further comprising a cryogenic liquid mechanical seal assembly on the plurality of impeller interstage bushings and wear rings functioning in conjunction and harmony with first and second deswirl mechanisms as part of the thrust equalizing mechanism, the mechanical seal assembly comprising a stationary diamond pattern mesh surface on an annular surface seal, a rotating smooth surface on the impeller or impeller wear ring which together with said stationary wear ring forms a radial clearance gap to seal interstage return liquid, a plurality of tertiary deswirl mechanisms upstream of the seal.
Type: Application
Filed: Feb 2, 2008
Publication Date: Jan 1, 2009
Applicant: Ebara International Corporation (Sparks, NV)
Inventor: Kevin A. Kaupert (Reno, NV)
Application Number: 12/012,541
International Classification: F01D 3/00 (20060101); F04B 17/03 (20060101); F04D 29/56 (20060101); F04D 27/00 (20060101);