HYDRAULICALLY SUPPORTED FACE SEAL

A hydraulically supported seal including a seal plate operatively coupled with a seal, the seal being supported by a seal carrier within a housing; a piston having a piston shaft, the piston being in operative communication with the seal opposite the seal plate, the piston shaft being disposed through the housing through a piston receiver formed in the housing; a cylinder operatively coupled to the piston opposite the seal; and wherein the piston is hydraulically biased by a hydraulic fluid within the cylinder.

BACKGROUND

The present disclosure is directed to a high pressure cylinder integrated into a housing for a face seal to improve sealing with use of a very high pressure CO2 working fluid system.

Waste heat recovery systems are configured to capture the thermal energy in the engine exhaust and transfer the thermal energy to a working fluid, such as supercritical CO2 or air. The working fluid is then sent through a thermodynamic cycle to produce power in the form of electricity or mechanical motion. This power is used to supplement engine thrust.

The use of supercritical CO2 as a working fluid in the waste heat recovery system requires very high pressure systems and resultant pressure differentials across sealing surfaces (1,000 psi).

As seen inFIGS.1to3typical face seals include a seal plate interacting with a carbon seal supported by a carbon carrier in a housing.FIG.1shows a bearing compartment with a face seal highlighted.FIG.2andFIG.3show a seal plate A proximate a low pressure Plow section. A carbon seal B is adjacent the seal plate A on the high pressure Phighsection. A carbon carrier C supports the carbon seal B. A damper D is coupled to a biasing member or spring S. The carbon seal B is biased by the mechanical spring S, such as a bellows spring or coil spring. The forces mustered by the bellows spring have a fixed limited range (100-150 psi) and can degrade over time.

What is needed is an improved face seal system capable of withstanding very high pressure differentials.

SUMMARY

In accordance with the present disclosure, there is provided a hydraulically supported seal comprising a seal plate operatively coupled with a seal, the seal being supported by a seal carrier within a housing; a piston having a piston shaft, the piston being in operative communication with the seal opposite the seal plate, the piston shaft being disposed through the housing through a piston receiver formed in the housing; a cylinder operatively coupled to the piston opposite the seal; and wherein the piston is hydraulically biased by a hydraulic fluid within the cylinder.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the seal plate is between a high-pressure section and a low-pressure section opposite the high-pressure section.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the seal is adjacent the seal plate on the low-pressure side of the seal plate.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the piston shaft within the piston receiver is sealed by a non-rotating secondary seal.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the hydraulically supported seal further comprising a hydraulic circuit fluidly coupled to the cylinder, the hydraulic circuit configured to pressurize the cylinder.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include secondary seals seal the piston and the cylinder interface.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the hydraulically supported seal further comprising a controller employed to maintain the hydraulic circuit pressure which maintains a seal face integrity.

In accordance with the present disclosure, there is provided a system for hydraulically supporting a seal in a supercritical carbon dioxide (sCO2) turbomachine comprising a supercritical carbon dioxide turbomachine seal plate operatively coupled with a seal, the seal being supported by a seal carrier within a housing located in the supercritical carbon dioxide turbomachine; a piston having a piston shaft, the piston being in operative communication with the seal opposite the seal plate, the piston shaft being disposed through the housing through a piston receiver formed in the housing; a cylinder operatively coupled to the piston opposite the seal; and

a hydraulic circuit containing a hydraulic fluid fluidly coupled to the cylinder, the hydraulic circuit configured to pressurize the cylinder, wherein the piston is hydraulically biased by the hydraulic fluid within the cylinder.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the system for hydraulically supporting a seal in a supercritical carbon dioxide turbomachine, further comprising a controller employed to maintain the hydraulic circuit pressure which maintains a seal face integrity.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the seal plate is between a high-pressure section and a low-pressure section.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the hydraulic circuit can be pressurized by a pump.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the system for hydraulically supporting a seal in a supercritical carbon dioxide turbomachine, further comprising a variable restrictor fluidly coupled to the hydraulic circuit and employed to regulate pressure in the hydraulic circuit.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the system for hydraulically supporting a seal in a supercritical carbon dioxide turbomachine, further comprising a controller operatively coupled to the hydraulic circuit and employed to maintain the hydraulic circuit pressure which maintains a sealing force.

In accordance with the present disclosure, there is provided a process for hydraulically supporting a seal comprising operatively coupling a seal plate with a seal; supporting the seal with a seal carrier within a housing; providing a piston having a piston shaft, the piston being in operative communication with the seal opposite the seal plate, disposing the piston shaft through a piston receiver formed in the housing; operatively coupling a cylinder to the piston opposite the seal; fluidly coupling a hydraulic circuit containing a hydraulic fluid to the cylinder; and hydraulically biasing the piston with the hydraulic fluid within the cylinder.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the process further comprising operatively coupling a controller with the hydraulic circuit; and employing the controller to maintain the hydraulic circuit pressure which maintains a seal face integrity.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the process further comprising sealing the interface between the piston and the cylinder with secondary seals.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the process further comprising fluidly coupling a variable restrictor to the hydraulic circuit; and employing the variable restrictor to regulate pressure in the hydraulic circuit.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the process further comprising pressurizing the hydraulic circuit with a pump.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include wherein the controller can be in communication with a supervisory controller.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the process further comprising providing engine operational conditions as control input to the hydraulic circuit to maintain the sealing forces acting on the carbon seal throughout at least one engine operating cycle.

Other details of the hydraulically supported seal are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements.

DETAILED DESCRIPTION

FIG.4schematically illustrates a gas turbine engine20. The gas turbine engine20is disclosed herein as a two-spool turbofan that generally incorporates a fan section22, a compressor section24, a combustor section26and a turbine section28. The fan section22may include a single-stage fan42having a plurality of fan blades43. The fan blades43may have a fixed stagger angle or may have a variable pitch to direct incoming airflow from an engine inlet. The fan42drives air along a bypass flow path B in a bypass duct13defined within a housing15such as a fan case or nacelle, and also drives air along a core flow path C for compression and communication into the combustor section26then expansion through the turbine section28. A splitter29aft of the fan42divides the air between the bypass flow path B and the core flow path C. The housing15may surround the fan42to establish an outer diameter of the bypass duct13. The splitter29may establish an inner diameter of the bypass duct13. Although depicted as a two-spool turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with two-spool turbofans as the teachings may be applied to other types of turbine engines including three-spool architectures.

The low speed spool30generally includes an inner shaft40that interconnects, a first (or low) pressure compressor44and a first (or low) pressure turbine46. The inner shaft40is connected to the fan42through a speed change mechanism, which in the exemplary gas turbine engine20is illustrated as a geared architecture48to drive the fan42at a lower speed than the low speed spool30. The inner shaft40may interconnect the low pressure compressor44and low pressure turbine46such that the low pressure compressor44and low pressure turbine46are rotatable at a common speed and in a common direction. In other embodiments, the low pressure turbine46drives both the fan42and low pressure compressor44through the geared architecture48such that the fan42and low pressure compressor44are rotatable at a common speed. Although this application discloses geared architecture48, its teaching may benefit direct drive engines having no geared architecture. The high speed spool32includes an outer shaft50that interconnects a second (or high) pressure compressor52and a second (or high) pressure turbine54. A combustor56is arranged in the exemplary gas turbine20between the high pressure compressor52and the high pressure turbine54. A mid-turbine frame57of the engine static structure36may be arranged generally between the high pressure turbine54and the low pressure turbine46. The mid-turbine frame57further supports bearing systems38in the turbine section28. The inner shaft40and the outer shaft50are concentric and rotate via bearing systems38about the engine central longitudinal axis A which is collinear with their longitudinal axes.

The low pressure compressor44, high pressure compressor52, high pressure turbine54and low pressure turbine46each include one or more stages having a row of rotatable airfoils. Each stage may include a row of static vanes adjacent the rotatable airfoils. The rotatable airfoils and vanes are schematically indicated at47and49.

The engine20may be a high-bypass geared aircraft engine. The bypass ratio can be greater than or equal to 10.0 and less than or equal to about 18.0, or more narrowly can be less than or equal to 16.0. The geared architecture48may be an epicyclic gear train, such as a planetary gear system or a star gear system. The epicyclic gear train may include a sun gear, a ring gear, a plurality of intermediate gears meshing with the sun gear and ring gear, and a carrier that supports the intermediate gears. The sun gear may provide an input to the gear train. The ring gear (e.g., star gear system) or carrier (e.g., planetary gear system) may provide an output of the gear train to drive the fan42. A gear reduction ratio may be greater than or equal to 2.3, or more narrowly greater than or equal to 3.0, and in some embodiments the gear reduction ratio is greater than or equal to 3.4. The gear reduction ratio may be less than or equal to 4.0. The fan diameter is significantly larger than that of the low pressure compressor44. The low pressure turbine46can have a pressure ratio that is greater than or equal to 8.0 and in some embodiments is greater than or equal to 10.0. The low pressure turbine pressure ratio can be less than or equal to 13.0, or more narrowly less than or equal to 12.0. Low pressure turbine46pressure ratio is pressure measured prior to an inlet of low pressure turbine46as related to the pressure at the outlet of the low pressure turbine46prior to an exhaust nozzle. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present invention is applicable to other gas turbine engines including direct drive turbofans. All of these parameters are measured at the cruise condition described below.

A significant amount of thrust is provided by the bypass flow B due to the high bypass ratio. The fan section22of the engine20is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet (10,668 meters). The flight condition of 0.8 Mach and 35,000 ft (10,668 meters), with the engine at its best fuel consumption—also known as “bucket cruise Thrust Specific Fuel Consumption (‘TSFC’)”—is the industry standard parameter of pounds-mass per hour lbm/hr of fuel flow rate being burned divided by pounds-force lbf of thrust the engine produces at that minimum point. The engine parameters described above, and those in the next paragraph are measured at this condition unless otherwise specified.

“Low fan pressure ratio” is the pressure ratio across the fan blade43alone, without a Fan Exit Guide Vane (“FEGV”) system. A distance is established in a radial direction between the inner and outer diameters of the bypass duct13at an axial position corresponding to a leading edge of the splitter29relative to the engine central longitudinal axis A. The low fan pressure ratio is a spanwise average of the pressure ratios measured across the fan blade43alone over radial positions corresponding to the distance. The low fan pressure ratio can be less than or equal to 1.45, or more narrowly greater than or equal to 1.25, such as between 1.30 and 1.40. “LOW corrected fan tip speed” is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram °R)/(518.7°R)]0.5. The “low corrected fan tip speed” can be less than or equal to 1150.0 ft/second (350.5 meters/second), and greater than or equal to 1000.0 ft/second (304.8 meters/second).

Referring now toFIG.5, there is illustrated an exemplary hydraulically supported seal100. The hydraulically supported seal10includes a seal plate12. The seal plate112is proximate a high pressure section Phigh. On the opposite side of the high pressure section Phighis a low pressure section Plow such as ambient pressure. The pressure differential between Phighand Plow can be one thousand pounds per square inch (1,000 psi). A seal114is adjacent the seal plate112on the low pressure side of the seal plate112. A seal carrier116is coupled to the seal114and supporting the seal114within a housing118.

A piston120is in operative communication with the seal114. The piston120includes a shaft121that is disposed through the housing118through a piston receiver122. The piston receiver122can be sealed by a non-rotating secondary seal124. The piston120is coupled to a cylinder126opposite the seal114. Secondary seals124can also seal the piston120and cylinder126interface.

The piston120is hydraulically biased by a hydraulic fluid128within the cylinder126. The cylinder126can be pressurized by a regulated hydraulic circuit130.

The hydraulic circuit130can be pressurized by a variety of pumps132, such as a gearbox driven pump, variable speed pump, variable displacement pump, and the like. In an exemplary embodiment, a variable restrictor134can be employed to regulate pressure in the hydraulic circuit130.

A controller136can be employed to maintain the hydraulic circuit130pressure which then maintains the seal face integrity. The controller136can be in communication with a supervisory controller138such as a Full Authority Digital Engine Controller (FADEC). Engine operational conditions can provide control input to the hydraulic circuit130to maintain the sealing forces140acting on the carbon seal114operational throughout the various engine operating cycles. In an exemplary embodiment, a supercritical carbon dioxide (sCO2) turbomachine can be employed along with the disclose hydraulically supported seal.

A technical advantage of the disclosed hydraulically supported seal includes the capacity to increase or decrease the sealing forces to maintain a balanced seal.

Another technical advantage of the disclosed hydraulically supported seal includes the capacity to apply high sealing forces to the seal to maintain seal integrity.

Another technical advantage of the disclosed hydraulically supported seal includes separation of the high-pressure supercritical CO2 from hydraulic fluid, thus eliminating cross-contamination.

There has been provided a hydraulically supported seal. While the hydraulically supported seal has been described in the context of specific embodiments thereof, other unforeseen alternatives, modifications, and variations may become apparent to those skilled in the art having read the foregoing description. Accordingly, it is intended to embrace those alternatives, modifications, and variations which fall within the broad scope of the appended claims.