Micro-turbine system

Abstract

A micro-turbine system (10) includes a combustor (12) defining an inlet (14) for receiving oxidizing agent, a combustion chamber (16) for combusting the fuel and the oxidizing agent, and an outlet (18) for expelling exhaust gas. The micro-turbine system (10) also includes a turbine machine (20) including a bearing housing (22) defining a bearing housing interior (24) and a lubricant passageway (26), a turbine housing (28) coupled to the bearing housing (22) and defining a turbine housing interior (30), a turbine wheel (32) disposed in the turbine housing interior (24), rotatable about an axis, and in fluid communication with the outlet (18) of the combustor (16). The turbine machine (20) also includes a shaft (34) rotatable with the turbine wheel (32) about the axis, a bearing arrangement (36) disposed about the shaft (34), and an electric machine (38) disposed about the shaft (34) and configured to convert rotational motion of the shaft (34) to electrical energy. The micro-turbine system (10) further includes a restriction valve (40) configured to increase a pressure in the bearing housing interior (24).

Description

MICRO-TURBINE SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to and all the benefits of U.S. Provisional Patent Application No. 63 / 676,646 filed July 29, 2024. which is hereby expressly incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION1. Field of the Invention

[0002] The invention generally relates to a micro-turbine system.2. Description of the Related Art

[0003] Conventional micro-turbine systems commonly include either a reciprocating engine or a combustor to combust a fuel-air mixture. Conventional micro-turbine systems also include a turbine machine having a turbine housing defining a turbine housing interior, a turbine wheel disposed in the turbine housing interior for receiving exhaust gas to rotate the turbine wheel, a bearing housing defining a bearing housing interior, and a shaft disposed in the bearing housing interior and rotatable with the turbine wheel, and an electric machine disposed about the shaft to convert rotational motion of the shaft to electrical energy'. The turbine housings of ty pical micro-turbine systems are at an elevated pressure due to the exhaust gas from the combustor. However, the bearing housings of typical micro-turbine systems are typically not under pressure.

[0004] As such, the turbine machines commonly require a seal disposed about the shaft to seal the turbine housing from the bearing housing. The seal attempts to maintain the pressure differential between the bearing housing and the turbine housing by preventing blow-by of exhaust gas from the turbine housing into the bearing housing. Blow-by of exhaustgas reduces the efficiency of the turbine machine, degrades lubricant present in the bearing housing interior, and must be vented from the lubricant to prevent excessive pressure build-up. However, conventional seals still allow an unacceptable amount of blow-by of exhaust gas into bearing housing interiors. Moreover, in conventional micro-turbine systems including a reciprocating engine, this pressure differential is typically viewed as a necessary outcome because the pressure in the bearing housing is correlated to the pressure in a crankcase of the reciprocating engine and thus must be minimized to avoid negative impacts to performance associated with elevated pressures in the crankcase.

[0005] As such, there remains a need for an improved micro-turbine system.SUMMARY OF THE INVENTION AND ADVANTAGES

[0006] A micro-turbine system for converting fuel to electrical energy includes a combustor defining an inlet for receiving oxidizing agent, a combustion chamber for combusting the fuel and the oxidizing agent, and an outlet for expelling exhaust gas from the combustion chamber. The micro-turbine system also includes a turbine machine. The turbine machine includes a bearing housing defining a bearing housing interior and a lubricant passageway in fluid communication with the bearing housing interior for directing a lubricant to the bearing housing interior. The turbine machine also includes a turbine housing coupled to the bearing housing and defining a turbine housing interior, and a turbine wheel disposed in the turbine housing intenor. The turbine wheel is rotatable about an axis extending longitudinally along the turbine housing and is in fluid communication with the outlet of the combustor.

[0007] The turbine machine further includes a shaft disposed at least partially in the bearing housing interior and rotatable with the turbine wheel about the axis, and a bearing arrangement disposed about the shaft in the bearing housing interior for supporting rotation ofthe shaft. The turbine machine further includes an electric machine disposed about the shaft and configured to convert rotational motion of the shaft to electrical energy. The micro-turbine system further includes a restriction valve configured to increase a pressure in the bearing housing interior.

[0008] By increasing the pressure in the bearing housing interior, any pressure differential between the turbine housing interior and the bearing housing interior is reduced. A reduced pressure differential between the turbine housing interior and the bearing housing interior reduces the amount of blow-by of exhaust gases from the turbine housing interior into the bearing housing interior. Reduced blow-by of exhaust gas increases the efficiency of the turbine machine because more energy from the exhaust gas is available to rotate the turbine wheel and the shaft, and thus the electric machine is able to convert more rotational motion from the shaft to electrical energy, increasing the power output of the electric machine. Moreover, reduced blow-by of exhaust gas limits degradation of the lubricant, increasing the lifespan of the lubricant and preventing potential damage from degraded lubricant to components of the micro-turbine system. Reduced blow-by of exhaust further reduces pressure build-up in the lubricant which must be vented from the lubricant.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

[0010] FIG. 1 is a schematic illustration of a micro-turbine system including a combustor, a turbine machine, a lubricant tank having a vent passageway for expelling pressurized gas from the lubricant tank, and a restriction valve configured to regulate expulsion of pressurized gas through the vent passageway:

[0011] FIG. 2 is a schematic illustration of the micro-turbine system according to another embodiment, with the turbine machine including a bearing housing defining a main drain, and with the micro-turbine system including a restriction valve configured to regulate expulsion of pressurized gas through the main drain;

[0012] FIG. 3 is a schematic illustration of the micro-turbine system according to another embodiment, with the turbine machine incorporated into a turbocharger, and with the restriction valve configured to regulate expulsion of pressurized gas through the vent passageway;

[0013] FIG. 4 is a schematic illustration of the micro-turbine system according to another embodiment, with the turbine machine incorporated into the turbocharger, and with the restriction valve configured to regulate expulsion of pressurized gas through the main drain;

[0014] FIG. 5 is a schematic illustration of the micro-turbine system according to another embodiment, with the micro-turbine system further including a second turbocharger, and with the restriction valve configured to regulate expulsion of pressurized gas through the vent passageway;

[0015] FIG. 6 is a schematic illustration of the micro-turbine system according to another embodiment, with the second turbocharger including a second bearing housing defining a second main drain, and where the micro-turbine system includes a second restriction valve configured to regulate expulsion of pressunzed gas through the second main drain of the second turbocharger;

[0016] FIG. 7 is a schematic illustration of the micro-turbine system according to another embodiment, with the micro-turbine system further including a third turbocharger, and with the restriction valve configured to regulate expulsion of pressurized gas through the vent passageway; and

[0017] FIG. 8 is a schematic illustration of the micro-turbine system according to another embodiment, with the third turbocharger including a third bearing housing defining a third main drain, and where the micro-turbine system includes a third restriction valve configured to regulate expulsion of pressurized gas through the third main drain of the third turbocharger.DETAILED DESCRIPTION OF THE INVENTION

[0018] With reference to the Figures, wherein like numerals indicate like parts throughout the several views, a micro-turbine system 10 for converting fuel to electrical energy includes a combustor 12 defining an inlet 14 for receiving oxidizing agent, a combustion chamber 16 for combusting the fuel and the oxidizing agent, and an outlet 18 for expelling exhaust gas from the combustion chamber 16. The micro-turbine system 10 also includes a turbine machine 20. The turbine machine 20 includes a bearing housing 22 defining a bearing housing interior 24 and a lubricant passageway 26 in fluid communication with the bearing housing interior 24 for directing a lubricant to the bearing housing interior 24. The turbine machine 20 also includes a turbine housing 28 coupled to the bearing housing 22 and defining a turbine housing interior 30, and a turbine wheel 32 disposed in the turbine housing interior 30. The turbine wheel 32 is rotatable about an axis Al extending longitudinally along the turbine housing 28 and is in fluid communication with the outlet 18 of the combustor 12.

[0019] The turbine machine 20 further includes a shaft 34 disposed at least partially in the bearing housing interior 24 and rotatable with the turbine wheel 32 about the axis Al, and a bearing arrangement 36 disposed about the shaft 34 in the bearing housing interior 24 for supporting rotation of the shaft 34. Although not required, the bearing arrangement 36 may include a plurality of rolling elements, a journal bearing, and / or a plain bearing. Other bearing arrangements 36 not specifically recited above are contemplated in thesubject description. The turbine machine 20 further includes an electric machine 38 disposed about the shaft 34 and configured to convert rotational motion of the shaft 34 to electrical energy. The micro-turbine system 10 further includes a restriction valve 40 configured to increase a pressure in the bearing housing interior 24.

[0020] By increasing the pressure in the bearing housing interior 24, any pressure differential between the turbine housing interior 30 and the bearing housing interior 24 is reduced. A reduced pressure differential between the turbine housing interior 30 and the bearing housing interior 24 reduces the amount of blow-by of exhaust gases from the turbine housing interior 30 into the bearing housing interior 24. Reduced blow-by of exhaust gas increases the efficiency of the turbine machine 20 because more energy from the exhaust gas is available to rotate the turbine wheel 32 and the shaft 34, and thus the electric machine 38 is able to convert more rotational motion from the shaft 34 to electrical energy, increasing the power output of the electric machine 38. Moreover, reduced blow-by of exhaust gas limits degradation of the lubricant, increasing the lifespan of the lubricant and preventing potential damage from degraded lubricant to components of the micro-turbine system 10. Reduced blowby of exhaust further reduces pressure build-up in the lubricant which must be vented from the lubricant.

[0021] The turbine machine 20 may further include a seal 42 disposed about the shaft 34 to seal the turbine housing interior 30 from the bearing housing interior 24. The seal 42 may be one or more piston rings, face seals, or labyrinth seals. Reduced pressure differentials between the turbine housing interior 30 and the bearing housing interior 24 further advantageously reduces axial force on the seal 42, particularly on piston rings and face seals, thus also decreasing wear on the seal 42 and increasing the lifespan of the seal 42.

[0022] Although not required, the restriction valve 40 may be configured to increase the pressure in the bearing housing interior 24 to at least 1 bar. It is to be appreciatedthat pressures referred to herein are to be understood as gauge pressures, and not absolute pressures. Thus, it is to be understood that the restriction valve 40 may be configured to increase the pressure in the bearing housing interior 24 to at least 1 bar above atmospheric pressure. Atmospheric pressure is dependent upon the physical location of the micro-turbine system 10 but is generally understood to be approximately 1 bar.

[0023] More specifically, the restriction valve 40 may be configured to increase the pressure in the bearing housing interior 24 to at least 2 bar, at least 3 bar, at least 4 bar, at least 5 bar, at least 6 bar, at least 7 bar, at least 8 bar, at least 9 bar, at least 10 bar, at least 11 bar, or at least 12 bar. In the embodiment with only the turbine machine 20, the combustor 12, and the restriction valve 40, the upper limit of which the restriction valve 40 may be configured to increase the pressure in the bearing housing interior 24 to is to be understood as a pressure in the turbine housing interior 30. Should the restriction valve 40 be configured to increase the pressure in the bearing housing interior 24 to a pressure above that of the turbine housing interior 30, the contents of the bearing housing interior (e g. the lubricant) would be forced into the turbine housing interior 30. That said, it is advantageous for the restriction valve 40 to increase the pressure in the bearing housing interior 24 to be close to, if not equal to, the pressure in the turbine housing interior 30 to reduce the pressure differential between the bearing housing interior 24 and the turbine housing interior 30 as much as possible. As such, the restriction valve 40 may be configured to increase the pressure in the bearing housing interior 24 such that the pressure in the bearing housing interior 24 is less than a pressure in the turbine housing interior 30.

[0024] The restriction valve 40 may be configured to passively increase the pressure in the bearing housing interior 4 to a predetermined pressure. In other words, the restriction valve 40 may be a passive restriction valve unable to variably increase the pressure in the bearing housing interior 24. The predetermined pressure may be at least 1 bar. Morespecifically, the predetermined pressure may be at least 2 bar, at least 3 bar, at least 4 bar, at least 5 bar, at least 6 bar, at least 7 bar, at least 8 bar, at least 9 bar, at least 10 bar, at least 11 bar, or at least 12 bar.

[0025] The micro-turbine system may further include a lubricant tank 44 in fluid communication with the lubricant passageway 26 for retaining the lubricant. The restriction valve 40 may be configured to variably increase the pressure in the bearing housing interior 24 in response to at least one chosen from a pressure in the turbine housing interior 30 and a pressure in the lubricant tank 44. In other words, the restriction valve 40 may be configured to variably increase the pressure in the bearing housing interior 24 in response to the pressure in the turbine housing interior 30, in response to the pressure in the lubricant tank, or in response to both the pressure in the turbine housing interior 30 and the pressure in the lubricant tank 44. The micro-turbine system 10 may further include at least one pressure sensor 46 configured to detect at least one of the pressure in the turbine housing interior 30 and the pressure in the lubricant tank 44. The at least one pressure sensor 46 is in communication with the restriction valve 40 to permit the restriction valve 40 to variably increase the pressure in the bearing housing interior 24. The pressure in the turbine housing interior 30 and the pressure in the lubricant tank 44 may fluctuate during operation of the micro-turbine system 10, such as but not limited to during start-up or through operating points. By variably increasing the pressure in the bearing housing interior 24 in response to either the pressure in the turbine housing interior 30 or the pressure in the lubricant tank 44, the restriction valve 40 is able to prevent the pressure in the bearing housing interior 24 from exceeding the pressure in the turbine housing interior 30 during these fluctuations.

[0026] Although not required, the lubricant tank 44 may include a vent passageway 48 for expelling pressurized gas from the lubricant tank 44. The pressurized gas may include blow-by of exhaust gas from the turbine housing interior 30 into the bearinghousing interior 24. However, the gases already present in the lubricant tank 44 may become pressurized in response to the lubricant tank, and lubricant contained therein, heating during operation of the micro-turbine system 10. As shown in FIGS 1, 3, 5, and 7, the restriction valve 40 may be configured to regulate expulsion of pressurized gas through the vent passageway 48 such that the restriction valve 40 increases the pressure in the bearing housing interior 24.

[0027] In the embodiments where the restriction valve 40 configured to regulate expulsion of pressurized gas through the vent passageway 48, the pressure in the lubricant tank 44 can be correlated to the pressure in the bearing housing interior 24. In these embodiments, it is to be appreciated that the pressure in the lubricant tank 44 may be close to, or even equal to, the pressure in the bearing housing interior 24. Thus, by regulating the expulsion of pressurized gas through the vent passageway 48, the restriction valve 40 is also able to regulate the pressure in the lubricant tank 44 and, indirectly, the pressure in the bearing housing interior 24.

[0028] In other embodiments, as shown in FIGS. 2, 4, 6, and 8, the bearing housing 22 further defines a main drain 50 to permit the lubricant to drain from the bearing housing interior 24. Although not required, in these embodiments the restriction valve 40 is configured to regulate expulsion of pressurized gas in the bearing housing interior 24 through the main drain 50 such that the restriction valve 40 increases the pressure in the bearing housing interior 24. The restriction valve 40 being configured to regulate expulsion of pressurized gas in the bearing housing interior 24 through the main drain 50 permits the restriction valve to more directly regulate the pressure in the bearing housing interior 24 regardless of the pressure in the lubricant tank 44 and regardless of the pressure in other components which may be present in the micro-turbine system 10.

[0029] As shown in FIGS. 3 and 4, the turbine-machine 20 may be incorporated into a turbocharger 52. The turbocharger 52 further includes a compressor housing 54 coupledto the bearing housing 22 and defining a compressor housing interior 56. The turbocharger also further includes a compressor wheel 58 disposed in the compressor housing interior 56 and rotatable with the shaft 34 about the axis Al. The compressor wheel 58 is in fluid communication with the combustion chamber 16. Although not required, the compressor wheel 58 may directly supply the combustion chamber 16 with compressed oxidizing agent. It is to be appreciated that, although only FIGS. 3 and 4 depict the turbocharger 52, the turbocharger 52 may be included in any embodiment shown in FIGS. 5-8 as well. The restriction valve 40 may be configured to increase the pressure in the bearing housing interior 24 such that the pressure in the bearing housing interior 24 is less than both a pressure in the compressor housing interior 56 and a pressure in the turbine housing interior 30. In this way, the restriction valve 40 prevents lubricant from being forced into either, or both, of the compressor housing interior 56 and the turbine housing interior 30. The restriction valve 40 also permits less purge air from the compressor housing interior 56 to be needed to cool the turbine wheel 32.

[0030] The turbocharger 52 may further include a second seal 60 disposed about the shaft 34 to seal the compressor housing interior 56 from the bearing housing interior 24. The seal 42 may be one or more piston rings, face seals, or labyrinth seals. Reduced pressure differentials between the compressor housing interior 56 and the bearing housing interior 24 further advantageously reduces axial force on the second seal 60, particularly on piston rings and face seals, thus also decreasing wear on the second seal 60 and increasing the lifespan of the second seal 60.

[0031] Although depicted in FIGS. 3 and 4 with the compressor housing 54 directly affixed to the bearing housing 22 and with the bearing housing 22 directly affixed to the turbine housing 28, it is to be appreciated that the turbine housing 28 may be directly affixed to the compressor housing 54. and the compressor housing 54 may be directly affixed to the bearing housing 22. Alternatively, it is also to be appreciated that the compressor housing 54may be directly affixed to the turbine housing 28, and the turbine housing 28 may be directly affixed to the bearing housing 22. All arrangements of direct affixation of the turbine housing 28, the compressor housing 54, and the bearing housing 22 as disclosed herein include the turbine housing 28 coupled to the bearing housing 22 and the compressor housing 54 coupled to the bearing housing 22. Moreover, it is also to be appreciated that two or all of the turbine housing 28, the bearing housing 22, and the compressor housing 54 may be unitary with one another.

[0032] As best shown in FIGS. 5 and 6, the micro-turbine system 10 may further include a second turbocharger 62. The second turbocharger 62 includes a second compressor housing 64 defining a second compressor housing interior 66. The turbocharger 52 also includes a second bearing housing 68 coupled to the second compressor housing 64 and defining a second bearing housing interior 70 and a second lubricant passageway 72 in fluid communication with the second bearing housing interior 70 for directing the lubricant to the second bearing housing interior 70. The turbocharger 52 further includes a second turbine housing 74 coupled to the second bearing housing 68 and defining a second turbine housing interior 76. The second turbocharger 62 further includes a second compressor wheel 78 disposed in the second compressor housing interior 66 and rotatable about a second axis A2, a second shaft 80 disposed at least partially in the second bearing housing interior 70 and rotatable with the second compressor wheel 78 about the second axis A2, a second bearing arrangement 82 disposed about the second shaft 80 in the second bearing housing interior 70 for supporting rotation of the second shaft 80, and a second turbine wheel 84 disposed in the second turbine housing interior 76 and rotatable with the second shaft 80 about the second axis A2. Although not required, the second bearing arrangement 82 may include a second plurality of rolling elements, a second journal bearing, and / or a second plain bearing. Other second bearing arrangements 82 not specifically recited above are contemplated in the subjectdescription. Additionally, the second turbocharger 62 may also include a second electric machine 86 disposed about the second shaft 80 and configured to convert at least one of rotational motion of the second shaft 80 to electrical energy and electrical energy to rotational motion of the second shaft 80. The restriction valve 40 is configured to increase a pressure in the second bearing housing interior 70.

[0033] The second turbocharger 62 may further include a third seal 88 disposed about the second shaft 80 to seal the second compressor housing interior 66 from the second bearing housing interior 70. The third seal 88 may be one or more piston rings, face seals, or labyrinth seals. Reduced pressure differentials between the second compressor housing interior 66 and the second bearing housing interior 70 further advantageously reduces axial force on the third seal 88, particularly on piston rings and face seals, thus also decreasing wear on the third seal 88 and increasing the lifespan of the third seal 88. The second turbocharger 62 may also further include a fourth seal 90 disposed about the second shaft 80 to seal the second turbine housing interior 76 from the second bearing housing interior 70. The fourth seal 90 may be one or more piston rings, face seals, or labyrinth seals. Reduced pressure differentials between the second turbine housing interior 76 and the second bearing housing interior 70 further advantageously reduces axial force on the fourth seal 90, particularly on piston rings and face seals, thus also decreasing wear on the fourth seal 90 and increasing the lifespan of the fourth seal 90.

[0034] In the embodiment shown in FIG. 5, the restriction valve 40 is configured to regulate expulsion of pressurized gas through the vent passageway 48 such that the restriction valve 40 increases the pressure in the bearing housing interior 24 and increases the pressure in the second bearing housing interior 70. As such, only a single restriction valve40 is needed to increase the pressure in the bearing housing interior 24 and the second bearing housing interior 70, permitting a simple and cost-effective solution to increasing the pressuresin the bearing housing interior 24 and the second bearing housing interior 70. It is to be appreciated that the restriction valve 40 as shown in FIG. 5 is configured to increase the pressure in the bearing housing interior 24 and increase the pressure in the second bearing housing interior 70 to approximately the same pressure.

[0035] However, in the embodiment shown in FIG. 6, the restriction valve 40 includes a first restriction valve 40 configured to increase the pressure in the bearing housing interior 24 and a second restriction valve 92 configured to increase the pressure in the second bearing housing interior 70. The first restriction valve 40 and the second restriction valve 92 may be independent from one another, and thus the first restriction valve 40 is able to increase the pressure in the bearing housing interior 24 independently of the second restriction valve 92 increasing the pressure of the second bearing housing interior 70. The second bearing housing 68 further defines a second main drain 94 to permit the lubricant to drain from the second bearing housing interior 70, and the second restriction valve 92 may be configured to regulate expulsion of pressurized gas in the second bearing housing interior 70 through the second main drain 94 such that the second restriction valve 92 increases the pressure in the second bearing housing interior 70. It is to be appreciated that the first restriction valve 40 may be configured to regulate expulsion of pressurized gas through either of the main drain 50 of the turbine machine 20 or through the vent passageway 48 when used in combination with the second restriction valve 92 configured to regulate expulsion of pressurized gas through the second main drain 94.

[0036] As shown in FIG.6. the exhaust gas generated in the combustion chamber 16 of the combustor 12 may be directed through the outlet 18 to the second turbine wheel 84 of the second turbocharger 62. thus rotating the second turbine wheel 84. the second shaft 80, and the second compressor wheel 78. The exhaust gas may then be directed from the second turbine wheel 84 to the turbine wheel 32 of the turbine machine 20, thus rotating theturbine wheel 32 and the shaft 34 and permitting the electric machine 38 to convert rotational motion of the shaft 34 to electrical energy. However, energy from the exhaust gas is used to rotate the second turbine wheel 84 and results in the exhaust gas decreasing in pressure. As such, it is to be appreciated that the pressure in the second turbine housing interior 76 is generally higher than the pressure in the turbine housing interior 30.

[0037] The first restriction valve 40 may be configured to increase the pressure in the bearing housing interior 24 to a first pressure, and the second restriction valve 92 may be configured to increase the pressure in the second bearing housing interior 70 to a second pressure greater than the first pressure of the bearing housing interior 24. In other words, to increase efficiency of the micro-turbine system 10, the second restriction valve 92 may be configured to increase the pressure in the second bearing housing interior 70 to a pressure higher than that of the pressure in the bearing housing interior 24. For example, although not required, the first restriction valve 40 may be configured to increase the pressure in the bearing housing interior 24 to at least 1 bar and the second restriction valve 92 may be configured to increase the pressure in the second bearing housing interior 70 to at least 4 bar.

[0038] The second restriction valve 92 may be configured to increase the pressure in the second bearing housing interior 70 such that the pressure in the second bearing housing interior 70 is less than both a pressure in the second compressor housing interior 66 and a pressure in the second turbine housing interior 76. In this way, the second restriction valve 92 prevents lubricant from being forced into either, or both, of the second compressor housing interior 66 and the second turbine housing interior 76. The second restriction valve 92 also permits less purge air from the second compressor housing interior 66 to be needed to cool the second turbine wheel 84.

[0039] Oxidizing agent, such as but not limited to air, may be compressed by the compressor wheel 58 of the turbocharger 52 (if present), directed to the second compressorwheel 78 of the second turbocharger 62, and then directed to the inlet 14 of the combustor 12. In the embodiments where the turbine machine 20 is not incorporated into the turbocharger 52, oxidizing agent may be compressed by the second compressor wheel 78 of the second turbocharger 62 and directed to the inlet 14 of the combustor 12.

[0040] As shown in FIGS. 7 and 8, the micro-turbine system 10 may include a third turbocharger 96. The third turbocharger 96 includes a third compressor housing 98 defining a third compressor housing interior 100. The third turbocharger 96 also includes a third bearing housing 102 coupled to the third compressor housing 98. The third bearing housing 102 defines a third bearing housing interior 104 and a third lubricant passageway 106 in fluid communication with the third bearing housing interior 104 for directing the lubricant to the third bearing housing interior 104. The third turbocharger 96 further includes a third turbine housing 108 coupled to the third bearing housing 102 and defining a third turbine housing interior 110. The third turbocharger 96 further includes a third compressor wheel 112 disposed in the third compressor housing 98 and rotatable about a third axis A3, a third shaft 114 disposed at least partially in the third bearing housing interior 104 and rotatable with the third compressor wheel 112 about the third axis A3, a third bearing arrangement 116 disposed about the third shaft 114 in the third bearing housing interior 104 for supporting rotation of the third shaft 114, and a third turbine wheel 118 disposed in the third turbine housing interior 110 and rotatable with the third shaft 1 14 about the third axis A3. Although not required, the third bearing arrangement 116 may include a third plurality of rolling elements, a third journal bearing, and / or a third plain bearing. Other third bearing arrangements 116 not specifically recited above are contemplated in the subj ect description. Additionally, the third turbocharger 96 may also include a third electric machine 120 disposed about the third shaft 114 and configured to convert at least one of rotational motion of the third shaft 114 to electrical energyand electrical energy to rotational motion of the third shaft 114. The restriction valve 40 is configured to increase a pressure in the third bearing housing interior 104.

[0041] The third turbocharger 96 may further include a fifth seal 122 disposed about the third shaft 114 to seal the third compressor housing interior 100 from the third bearing housing interior 104. The fifth seal 122 may be one or more piston rings, face seals, or labyrinth seals. Reduced pressure differentials between the third compressor housing interior 100 and the third bearing housing interior 104 further advantageously reduces axial force on the fifth seal 122, particularly on piston rings and face seals, thus also decreasing wear on the fifth seal 122 and increasing the lifespan of the fifth seal 122. The third turbocharger 96 may also further include a sixth seal 124 disposed about the third shaft 114 to seal the third turbine housing interior 1 10 from the third bearing housing interior 104. The sixth seal 124 may be one or more piston rings, face seals, or labyrinth seals. Reduced pressure differentials between the third turbine housing interior 110 and the third bearing housing interior 104 further advantageously reduces axial force on the sixth seal 124, particularly on piston rings and face seals, thus also decreasing wear on the sixth seal 124 and increasing the lifespan of the sixth seal 124.

[0042] In the embodiment shown in FIG. 7, the restriction valve 40 is configured to regulate expulsion of pressurized gas through the vent passageway 48 such that the restriction valve 40 increases the pressure in the bearing housing interior 24, increases the pressure in the second bearing housing interior 70, and increases the pressure in the third bearing housing interior 104. As such, only a single restriction valve 40 is needed to increase the pressure in the bearing housing interior 24, the second bearing housing interior 70, and the third bearing housing interior 104, permitting a simple and cost-effective solution to increasing the pressures in the bearing housing interior 24, the second bearing housing interior 70, and the third bearing housing interior 104. It is to be appreciated that the restriction valve 40 as shown in FIG. 5 is configured to increase the pressure in the bearing housing interior 24, increase thepressure in the second bearing housing interior 70, and increase the pressure in the third bearing housing interior 104 to approximately the same pressure.

[0043] However, in the embodiment shown in FIG. 8, the restriction valve 40 includes a first restriction valve 40 configured to increase the pressure in the bearing housing interior 24, a second restriction valve 92 configured to increase the pressure in the second bearing housing interior 70, and a third restriction valve 126 configured to increase the pressure in the third bearing housing interior 104. The first restriction valve 40, the second restriction valve 92, and the third restriction valve 126 may be independent from one another, and thus the first restriction valve 40 is able to increase the pressure in the bearing housing interior 24, the second restriction valve 92 is able to increase the pressure in the second bearing housing interior 70, and the third restriction valve 126 is able to increase the pressure in the third bearing housing interior 104 all independently from one another. The third bearing housing 102 further defines a third main drain 128 to permit the lubricant to drain from the third bearing housing interior 104, and the third restriction valve 126 may be configured to regulate expulsion of pressurized gas in the third bearing housing interior 104 through the third main drain 128 such that the third restriction valve 126 increases the pressure in the third bearing housing interior 104. It is to be appreciated that the first restriction valve 40 may be configured to regulate expulsion of pressurized gas through either of the main drain 50 of the turbine machine 20 or through the vent passageway 48 when used in combination with the second restriction valve 92 configured to regulate expulsion of pressurized gas through the second main drain 94 and the third restriction valve 126 configured to regulate expulsion of pressurized gas through the third main drain 128.

[0044] As shown in FIG.8. the exhaust gas generated in the combustion chamber 16 of the combustor 12 may be directed through the outlet 18 to the third turbine wheel 118 of the third turbocharger 96, thus rotating the third turbine wheel 118, the third shaft114, and the third compressor wheel 112. The exhaust gas may then be directed from the third turbine wheel 118 to the second turbine wheel 84 of the second turbocharger 62, thus rotating the second turbine wheel 84, the second shaft 80, and the second compressor wheel 78. The exhaust gas may then be directed from the second turbine wheel 84 to the turbine wheel 32 of the turbine machine 20, thus rotating the turbine wheel 32 and the shaft 34 and permitting the electric machine 38 to convert rotational motion of the shaft 34 to electrical energy. However, energy from the exhaust gas is used to rotate the third turbine wheel 118 and the second turbine wheel 84 and results in the exhaust gas progressively decreasing in pressure. As such, it is to be appreciated that the pressure in the third turbine housing interior 110 is generally higher than the pressure in the second turbine housing interior 76, and the second turbine housing interior 76 is generally higher than the pressure in the turbine housing 28.

[0045] The first restriction valve 40 may be configured to increase the pressure in the bearing housing interior 24 to a first pressure, the second restriction valve 92 may be configured to increase the pressure in the second bearing housing interior 70 to a second pressure greater than the first pressure of the bearing housing interior 24, and the third restriction valve 126 may be configured to increase the pressure in the third bearing housing interior 104 to a third pressure greater than the second pressure of the second bearing housing interior 70. In other words, to increase efficiency of the micro-turbine system 10, the third restriction valve 126 may be configured to increase the pressure in the third bearing housing interior 104 to a pressure higher than that of the pressure in either the second bearing housing interior 70 and the bearing housing interior 24. For example, although not required, the first restriction valve 40 may be configured to increase the pressure in the bearing housing interior 24 to at least 1 bar. the second restriction valve 92 may be configured to increase the pressure in the second bearing housing interior 70 to at least 4 bar, and the third restriction valve may be configured to increase the pressure in the third bearing housing interior 104 to at least 8 bar.

[0046] The third restriction valve 126 may be configured to increase the pressure in the third bearing housing interior 104 such that the pressure in the third bearing housing interior 104 is less than both a pressure in the third compressor housing interior 100 and a pressure in the third turbine housing interior 110. In this way, the third restriction valve 126 prevents lubricant from being forced into either, or both, of the third compressor housing interior 100 and the third turbine housing interior 110. The third restriction valve 126 also permits less purge air from the third compressor housing interior 100 to be needed to cool the third turbine wheel 118.

[0047] Oxidizing agent, such as but not limited to air, may be compressed by the compressor wheel 58 of the turbocharger 52 (if present), directed to the second compressor wheel 78 of the second turbocharger 62, directed from the second compressor wheel 78 of the second turbocharger 62 to the third compressor wheel 112 of the third turbocharger 96, and then directed to the inlet 4 of the combustor 12. In the embodiments where the turbine machine 20 is not incorporated into the turbocharger 52, oxidizing agent may be compressed by the second compressor wheel 78 of the second turbocharger 62, directed from the second compressor wheel 78 of the second turbocharger 62 to the third compressor wheel 1 12 of the third turbocharger 96, and then directed to the inlet 14 of the combustor 12.

[0048] The micro-turbine system 10 may even include a fourth turbocharger, a fifth turbocharger, or more than five turbochargers constructed and arranged in accordance with the disclosure of the second turbocharger 62 and the third turbocharger 96 as disclosed herein.

[0049] As shown in FIGS. 1-8, the micro-turbine system 10 may further include a pump 130 configured to pump the lubricant from the lubricant tank 44 to the lubricant passageway 26. As shown in FIGS. 5-8. the micro-turbine system 10 may also further include a lubricant manifold 132. The lubricant manifold 132 receives lubricant from the pump 130and directs the lubricant to the lubricant passageway 26, the second lubricant passageway 72, and optionally the third lubricant passageway 106 when present. In the embodiments shown in FIGS. 1, 3, 5, and 7, the restriction valve 40 may be configured to increase the pressure in a closed circuit defined between the lubricant tank 44, the restriction valve 40, the pump 130, the lubricant passageway 26, the bearing housing 22, and optionally the lubricant manifold 132, optionally the second lubricant passageway 72, optionally the second bearing housing interior 70, optionally the third lubricant passageway 106, and optionally the third bearing housing interior 104.

[0050] The restriction valve 40 may be of any suitable construction for increasing pressure, including but not limited to, needle valves, butterfly valves, gate valves, ball valves, orifice plates, or any combination thereof. The micro-turbine system 10 may be free of a reciprocating engine, thus eliminating any concerns with increased pressure in a crankcase of the reciprocating engine.

[0051] The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings, and the invention may be practiced otherwise than as specifically described.

Claims

CLAIMSWhat is claimed is:

1. A micro-turbine system for converting fuel to electrical energy, said microturbine system comprising: a combustor defining an inlet for receiving oxidizing agent, a combustion chamber for combusting the fuel and the oxidizing agent, and an outlet for expelling exhaust gas from said combustion chamber; a turbine machine comprising, a bearing housing defining a bearing housing interior and a lubricant passageway in fluid communication with said bearing housing interior for directing a lubricant to said bearing housing interior; a turbine housing coupled to said bearing housing and defining a turbine housing interior; a turbine wheel disposed in said turbine housing interior, rotatable about an axis extending longitudinally along said turbine housing, and in fluid communication with said outlet of said combustor; a shaft disposed at least partially in said bearing housing interior and rotatable with said turbine wheel about said axis; a bearing arrangement disposed about said shaft in said bearing housing interior for supporting rotation of said shaft; and an electric machine disposed about said shaft and configured to convert rotational motion of said shaft to electrical energy; and a restriction valve configured to increase a pressure in said bearing housing interior.

2. The micro-turbine system as set forth in claim 1, wherein said restriction valve is configured to increase said pressure in said bearing housing interior to at least 1 bar.

3. The micro-turbine system as set forth in any one of claims 1 and 2, wherein said restriction valve is configured to passively increase said pressure in said bearing housing interior to a predetermined pressure.

4. The micro-turbine system as set forth in claim 3, wherein said predetermined pressure is at least 1 bar.

5. The micro-turbine system as set forth in any one of claims 1-4, wherein said restriction valve is configured to increase said pressure in said bearing housing interior such that said pressure in said bearing housing interior is less than a pressure in said turbine housing interior.

6. The micro-turbine system as set forth in any one of claims 1-5 further comprising a lubricant tank in fluid communication with said lubricant passageway for retaining the lubricant, wherein said restriction valve is configured to variably increase said pressure in said bearing housing interior in response to at least one chosen from a pressure in said turbine housing interior and a pressure in said lubricant tank.

7. The micro-turbine system as set forth in claim 6 further comprising at least one pressure sensor configured to detect at least one of said pressure in said turbine housing interior and said pressure in said lubricant tank, with said at least one pressure sensor in communication with said restriction valve to permit said restriction valve to variably increase said pressure in said bearing housing interior.

8. The micro-turbine system as set forth in any one of claims 1-5 further comprising a lubricant tank in fluid communication with said lubricant passageway for retaining the lubricant, wherein said lubricant tank includes a vent passageway for expelling pressurized gas from said lubricant tank, wherein said restriction valve is configured to regulate expulsion of pressurized gas through said vent passageway such that said restriction valve increases said pressure in said bearing housing interior.

9. The micro-turbine system as set forth in any one of claims 1-8, wherein said bearing housing further defines a main drain to permit the lubricant to drain from said bearing housing interior, and wherein said restriction valve is configured to regulate expulsion of pressurized gas in said bearing housing interior through said main drain such that said restriction valve increases said pressure in said bearing housing interior.

10. The micro-turbine system as set forth in any one of claims 1-9, wherein the turbine-machine is incorporated into a turbocharger, and wherein the turbocharger comprises a compressor housing coupled to the bearing housing and defining a compressor housing interior, and a compressor wheel disposed in said compressor housing interior and rotatable with said shaft about said axis.

11. The micro-turbine system as set forth in any one of claims 1-10 further comprising a second turbocharger, said second turbocharger comprising: a second compressor housing defining a second compressor housing interior; a second bearing housing coupled to said second compressor housing, with said second bearing housing defining a second bearing housing interior and a second lubricant passageway in fluid communication with said second bearing housing interior for directing the lubricant to said second bearing housing interior; a second turbine housing coupled to said second bearing housing, with said second turbine housing defining a second turbine housing interior; a second compressor wheel disposed in said second compressor housing interior and rotatable about a second axis; a second shaft disposed at least partially in said second bearing housing interior and rotatable with said second compressor wheel about said second axis; a second bearing arrangement disposed about said second shaft in said second bearing housing interior for supporting rotation of said second shaft; anda second turbine wheel disposed in said second turbine housing interior and rotatable with said second shaft about said second axis, wherein said restriction valve is configured to increase a pressure in said second bearing housing interior.

12. The micro-turbine system as set forth in claim 11 , wherein said restriction valve includes a first restriction valve configured to increase said pressure in said bearing housing interior, and a second restriction valve configured to increase said pressure in said second bearing housing interior.

13. The micro-turbine system as set forth in claim 12, wherein said first restriction valve is configured to increase said pressure in said bearing housing interior to a first pressure, and wherein said second restriction valve is configured to increase said pressure in said second bearing housing interior to a second pressure greater than said first pressure of said bearing housing interior.

14. The micro-turbine system as set forth in any one of claims 12 and 13, wherein said first restriction valve is configured to increase said pressure in said bearing housing interior to at least 1 bar, and wherein said second restriction valve is configured to increase said pressure in said second bearing housing interior to at least 4 bar.

15. The micro-turbine system as set forth in any one of claims 12-14, wherein said second bearing housing further defines a second main drain to permit the lubricant to drain from said second bearing housing interior, and wherein said second restriction valve is configured to regulate expulsion of pressurized gas in said second bearing housing interior through said second main drain such that said second restriction valve increases said pressure in said second bearing housing interior.

16. The micro-turbine system as set forth in any one of claims 11-15, wherein said micro-turbine system further comprises a third turbocharger, said third turbocharger comprising: a third compressor housing defining a third compressor housing interior; a third bearing housing coupled to said third compressor housing, with said third bearing housing defining a third bearing housing interior and a third lubricant passageway in fluid communication with said third bearing housing interior for directing the lubricant to said third bearing housing interior; a third turbine housing coupled to said third bearing housing, with said third turbine housing defining a third turbine housing interior; a third compressor wheel disposed in said third compressor housing and rotatable about a third axis: a third shaft disposed at least partially in said third bearing housing interior and rotatable with said third compressor wheel about said third axis: a third bearing arrangement disposed about said third shaft in said third bearing housing interior for supporting rotation of said third shaft; and a third turbine wheel disposed in said third turbine housing interior and rotatable with said third shaft about said third axis, wherein said restriction valve is configured to increase a pressure in said third bearing housing interior.

17. The micro-turbine system as set forth in claim 16, wherein said restriction valve includes a first restriction valve configured to increase said pressure in said bearing housing interior, a second restriction valve configured to increase said pressure in said second bearing housing interior, and a third restriction valve configured to increase said pressure in said third bearing housing interior.

18. The micro-turbine system as set forth in claim 17, wherein said first restriction valve is configured to increase said pressure in said bearing housing interior to a first pressure, wherein said second restriction valve is configured to increase said pressure in said second bearing housing interior to a second pressure greater than said first pressure of said bearing housing interior, and wherein said third restriction valve is configured to increase said pressure in said third bearing housing interior to a third pressure greater than said second pressure of said second bearing housing interior.

19. The micro-turbine system as set forth in any one of claims 17 and 18, wherein said first restriction valve is configured to increase said pressure in said bearing housing interior to at least 1 bar, wherein said second restriction valve is configured to increase said pressure in said second bearing housing interior to at least 4 bar, and wherein said third restriction valve is configured to increase said pressure in said third bearing housing interior to at least 8 bar.

20. The micro-turbine system as set forth in any one of claims 17-19, wherein said third bearing housing further defines a third main drain to permit the lubricant to drain from said third bearing housing interior, and wherein said third restriction valve is configured to regulate expulsion of pressurized gas in said third bearing housing interior through said third main drain such that said third restriction valve increases said pressure in said third bearing housing interior.

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