Deswirl mechanisms and roller bearings in an axial thrust equalization mechanism for liquid cryogenic turbomachinery

Abstract

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.

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.