CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of the filing date of United States Provisional

Patent Application No. 62/962,292, filed January 17, 2020, the disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] Rotating shafts are utilized in many different machines and are typically used to transfer power from one machine element to another machine element. For example, a driveshaft in an automobile transfers power generated by an internal combustion engine to wheels of the automobile in order to propel it in the desired direction. Similarly, a drive shaft in a ship transfers power generated by the ship’s engine to a propeller.

[0003] Since the purpose of machine shafts involves their rotation, they are typically mounted to the machine via one or more bearings that allow for rotational freedom of movement. One type of bearing is a rolling bearing which may include a stator, rotor, and rolling bearing elements. The rotor typically rotates with the shaft while the stator is mounted to the machine so that it is rotationally stationary relative to the shaft and rotor. The rolling bearing elements, such as ball rollers, spherical rollers, cylindrical rollers, and the like are positioned in a raceway between the stator and rotor. In operation, the rolling elements roll within the raceway which allows the rotor and shaft to rotate relative to the stator. Grease may be provided within the bearing’s raceway and be self-contained therein to help reduce friction and alleviate wear. While grease may be suitable for some applications, it is not suitable for many applications particularly those involving high speed operations and high temperature environments, such as those involving gas turbine engines and turbochargers, for example. [0004] Gas turbines are commonly used in electric power generation and aircraft propulsion and typically include a compressor, combustor, and a turbine. Air drawn into a gas turbine is compressed by the compressor. The compressed air is then mixed with fuel and combusted by the combustor which results in a high temperature energetic exhaust that can be upwards of thousands of degrees Celsius. This energetic exhaust drives the turbine which in turn drives the compressor which is commonly connected to the turbine via a shaft. This highly energetic process can result in the rotation of the shaft at tens of thousands of revolutions per minute (“RPM”). For example, large scale turbine engines commonly found in commercial aviation and industrial power generation typically operate at upwards of 15,000 RPM. In contrast, ship driveshafts and automobile driveshafts, which are typically mounted via greased bearings, respectively operate at hundreds of RPM and a few thousand RPM.

[0005] Certain lubrication systems, such as total-loss oil systems and circulating-oil systems, address the deficiencies of self-contained bearing lubricants like that of grease. Total- loss oil systems provide a constant supply of fresh lubricant. Shortly after the lubricant is injected into a bearing and used to cool, clean, and lubricate the bearing, the lubricant is ejected from the bearing where it is promptly discarded. For example, in the case of a gas turbine, oil is commonly ejected from a bearing into the combustor where it is burned away. In contrast, circulating-oil or closed-loop oil systems recuperate and recycle the oil for continuous use. [0006] While such systems have been satisfactory for traditional applications, such as large-scale turbines found in commercial aviation and industrial power generation, they have not been satisfactory in more recent developments in power generation. In recent years, there has been a desire to miniaturize power generation for various applications. For example, the advent of unmanned aerial vehicles (“UAV”) has generated demand for small scale engines, such as microturbines, that are capable of feats of long endurance. This has widespread application in both the public and private sectors, such as, for example, land management and wildfire control. In this regard, total-oil loss systems are not practical as the aircraft’ s endurance becomes tied to the amount of oil it can carry. Moreover, the more oil that is carried by the aircraft, the greater its weight which itself reduces the aircraft’s ability to carry a useful payload, efficiency and endurance.

[0007] Another factor that has proven problematic in microturbine development is its extreme operating conditions. Similar to large scale turbines, gas microturbines combust fuel at thousands of degrees Celsius. However, microturbine shafts operate at hundreds of thousands of RPM, which is much greater than the tens of thousands of RPM rotation speeds of traditional gas turbines. For example, gas microturbines are routinely operated from about 20,000 RPM to about 500,000 RPM with many existing microturbines having operating speeds at about 200,000 RPM. Such extreme speeds has made the use of rolling bearings in microturbines difficult and, in some cases, impossible to use effectively particularly where long endurance is paramount and has introduced design difficulties with respect to shaft operation. [0008] One such difficulty is shaft vibration. Turbine assemblies are often carefully balanced to limit undesirable and detrimental vibration responses. However, perfect balance is nearly impossible to achieve. In this regard, each turbine shaft has multiple resonant frequencies which each produce amplified stress imposing vibrations at various RPM. Such vibrations can be avoided by operating the shaft at an RPM below or above that required to reach a particular resonant frequency. However, considering the required operating envelopes and high operating speeds of microturbine shafts, this is not possible. As such, gas microturbines must operate through multiple resonant frequencies and do so without damaging the aircraft. However, rolling bearings are commonly stiff in a radial direction and thereby act as a conduit to transfer vibrations from the shaft to the engine’s housing and to the airframe. Additionally, the rigidity of such bearings can induce additional stresses on the shaft as it vibrates. In this regard, the airframe and shaft become susceptible to damage particularly over multiple cycles of use.

[0009] Moreover, the high operating speeds of gas microturbines generates significant centrifugal force which has the tendency to drive lubricant away from the bearing’s rolling elements potentially creating dry spots increasing the risk of failure. In addition, where it is desirable to circulate lubricant through a bearing and recycle the lubricant for further use, such as in circulating-oil systems, the bearing must be sealed so that lubricant passing through it is not ejected to the internal engine environment and lost. However, traditional seals used in large scale turbines have been found to be lacking in this regard in the context of gas microturbines particularly considering the high operating speeds of such engines. In addition, such high operating speeds generates significant frictional heat beyond that found in bearings of traditional engines such that traditional cooling solutions have also been found to be lacking. Furthermore, the working space for oil distribution equipment is limited considering the small size of microturbines relative to traditional large scale turbines rendering oil distribution system arrangements found in large scale turbines inapplicable to microturbines. As such, mechanical rolling bearings and circulating-oil systems serving the same have not been effectively implemented in gas microturbines to date. Because of these difficulties, some microturbines utilize air bearings. However, air bearing supports are not viable for aviation applications due to the g-forces experienced by the aircraft during flight which displaces the rotating assembles so that they contact the engine’s static components often with catastrophic results. Therefore, further improvements are desirable. SUMMARY OF THE INVENTION

[0010] A gas microturbine that has a power output of about 3.5 kW to about 1000 kW and includes a shaft, a turbine, a compressor, a combustor, a housing, a first bearing, and a closed-loop oil distribution system. The turbine is coupled to the shaft. The turbine has a peripheral diameter of about 25 mm to about 300 mm. The compressor is also coupled to the shaft. The compressor has a peripheral diameter of about 25 mm to about 300 mm. The combustor is disposed downstream of the compressor and upstream of the turbine. The housing encapsulates the compressor, turbine, shaft, and combustor. The first bearing has a stator, a rotor, and a plurality of bearing elements. The stator is coupled to the housing. The rotor is coupled to the shaft, and the bearing elements are disposed between the stator and rotor within a raceway defined between the rotor and stator. The closed-loop oil distribution system has an oil reservoir, an oil-supply circuit, an oil-scavenge circuit, and a pump. The oil reservoir is configured to contain a provision of oil. The oil-supply circuit has an inlet in communication with the oil reservoir and a first outlet in communication with the raceway of the first bearing. The oil-scavenge circuit has a first inlet in communication with the raceway of the first bearing and an outlet in communication with the oil reservoir. The pump is coupled to either the oil- supply circuit or the oil-scavenge circuit and is configured to pump oil from the oil reservoir through the oil supply circuit to the first outlet of the oil- supply circuit and from the first inlet of the oil-scavenge circuit back to the oil reservoir.

[0011] Additionally, the closed-loop oil distribution system may include a cooling jacket in contact with the first bearing for transferring heat therefrom. The oil- supply circuit may have a second outlet in communication with the cooling jacket for supplying oil to the cooling jacket. The oil-scavenge circuit may have a second inlet in communication with the cooling jacket for transporting oil away from the cooling jacket. The gas microturbine may further include a compressed air source and an air- supply circuit. The air- supply circuit may be in communication with the compressed air source and may be coupled to the first outlet of the oil-supply circuit. The first outlet of the oil-supply circuit may include a nozzle such that oil passing through the oil supply circuit mixes with air passing through the air-supply circuit and is atomized by the nozzle so as to provide an air-oil mist into the raceway of the first bearing. The outlet of the oil- supply circuit may include a plurality of venturis. The plurality of venturis may include a first venturi that has a taper angle of one to two degrees. The first venturi and nozzle may be in series with each other. [0012] Continuing with this aspect, the oil- scavenge circuit may include a deaerator configured to remove air introduced into the oil-scavenge circuit via the first inlet thereof. The oil-supply circuit, oil-scavenge circuit, and air-supply circuit may respectively include a first oil-supply manifold, a first oil-scavenge manifold, and a first air-supply manifold. The first oil- supply manifold, first air-supply manifold, and first air-supply manifold may each be ring shaped and positioned about the shaft such that oil and air respectively flow through such manifolds about the shaft. The oil-supply circuit and oil-scavenge circuit may include a plurality of conduits in communication with the first oil-supply and first oil-scavenge manifolds, respectively, such that oil is distributed to and from the first oil-supply and first oil- scavenge manifolds via the conduits.

[0013] The closed-loop oil distribution system may also include a manifold body. The manifold body may be positioned about the shaft. The manifold body may at least partially define the first oil- supply manifold, the first oil-scavenge manifold, and first air- supply manifold. The manifold body may interface with the housing and may include a first set of damping pockets formed therein. The first set of damping pockets may be configured to receive oil therein so as to provide an oil cushion at the interface of the first manifold body and housing for damping vibrations produced by the shaft. A first damping pocket may be positioned between the first oil-supply and first oil-scavenge manifolds. The manifold body may interface with the stator and may define a second set of damping pockets at the body-stator interface. The damping pockets may be configured to receive oil therein so as to provide an oil cushion at the interface of the manifold body and stator for damping vibrations produced by the shaft. Each of the damping pockets of the first and second sets of damping pockets may be circumferential grooves that extend about a central axis of the manifold body. At least some of the conduits and the nozzle may be formed within and defined by the manifold body.

[0014] The microturbine may also include a second bearing coupled to the shaft and a second oil-supply manifold and a second oil-scavenge manifold in communication with the second bearing. Also, a plurality of bridging conduits may form a portion of the oil-supply circuit and may carry oil from the first oil-supply manifold to the second oil-supply manifold. At least one of the bridging conduits may form a portion of the oil-scavenge circuit and may carry oil from the first oil-scavenge manifold to the second oil-scavenge manifold.

[0015] The microturbine may further include a first- side purge seal and a second- side purge seal. The first-side purge seal may be coupled to the shaft and positioned at a first side of the first bearing so as to at least partially occlude a first side of the bearing raceway. The second-side purge seal may be coupled to the shaft and may be positioned at a second side of the first bearing so as to at least partially occlude a second side of the bearing raceway. The second- side purge seal may include an oil sling surface concavely curved so as to redirect oil passing through the raceway of the bearing toward the first inlet of the oil-scavenge circuit. The second-side purge seal may be at an opposite side of the bearing from that of the nozzle. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings in which:

[0017] FIG. 1A is a cutaway perspective view of a gas microturbine according to an embodiment of the present disclosure.

[0018] FIG. IB is a perspective view of a compressor, turbine, shaft, and a portion of a closed-loop oil distribution system of the gas microturbine of FIG. 1A according to an embodiment of the present disclosure.

[0019] FIG. 2 is a schematic representation of the gas microturbine of FIG. IB and the closed-loop oil distribution system thereof.

[0020] FIG. 3A is a front perspective view of an oil supply circuit of the closed loop- oil distribution system of the gas microturbine of FIG. 1A in accordance with an embodiment of the present disclosure.

[0021] FIG. 3B is a rear perspective view of the oil supply circuit of FIG. 3A in conjunction with bearings of the gas microturbine.

[0022] FIG. 4A is a front perspective view of an oil scavenge circuit of the closed-loop oil distribution system of the gas microturbine of FIG. 1A in accordance with an embodiment of the present disclosure.

[0023] FIG. 4B is a rear perspective view of the oil scavenge circuit of FIG. 4A including the bearings of FIG. 3B.

[0024] FIG. 5 is a front perspective view of an air volume representing an air supply circuit of the closed-loop oil distribution system of the gas microturbine of FIG. 1A in accordance with an embodiment of the present disclosure. [0025] FIG. 6 is a perspective view of a manifold body of the closed-loop distribution oil system of the gas microturbine of FIG. 1A in accordance with an embodiment of the present disclosure.

[0026] FIG. 7 is a perspective view of a rotary purge seal of the closed-loop oil distribution system of the gas microturbine of FIG. 1A in accordance with an embodiment of the present disclosure.

[0027] FIG. 8A is a perspective view of a configuration of the oil-supplyand oil- scavenge circuits and the air volume representing the air- supply circuit in the gas microturbine of FIG. 1A.

[0028] FIG. 8B is a perspective view of the air volume representing the air-supply circuit, purge seals, and shaft of the gas microturbine of FIG. 1A.

[0029] FIG. 9A is a partial side-view showing the compressor and shaft of the gas micro turbine of FIG. 1A.

[0030] FIG. 9B is a cross-sectional view taken along Section B-B of FIG. 9A.

[0031] FIG. 9C is an enhanced view of detail C of FIG. 9B.

[0032] FIG. 9D is a cross-sectional view taken along line D-D of FIG. 9B including the housing of the gas microturbine of FIG. 1 A.

[0033] FIG. 9E is an enhanced view of detail E of FIG. 9D including the housing of the gas microturbine of FIG. 1A.

[0034] FIG. 9F is a cross-sectional view taken along line F-F of FIG. 9B including the housing of the gas microturbine of FIG. 1 A.

[0035] FIG. 10 is a perspective view of a wetted volume of an air-oil mist generated by the closed-loop oil distribution system of the gas microturbine of FIG. 1 A.

DETAILED DESCRIPTION

[0036] FIGs. lA-10 depicts an exemplary gas microturbine engine 10 according to an embodiment of the present disclosure. Microturbine 10 generally includes a housing 12, compressor 50, turbine 70, shaft 60, combustor 16, bearings 150, closed-loop oil distribution system, and a full authority digital engine control 40 (“FADEC”). While not shown, in some embodiments, a generator may be coupled to shaft to generate electricity to charge a battery and/or provide on-demand electricity.

[0037] As indicated, engine 10 is a microturbine. As such, it is a combustion engine that is capable of burning a range of gaseous or liquid fuels in a process defined by the Brayton thermodynamic cycle, also known as a Joule cycle. In addition, microturbine 10 is capable of generating a useful power output of about 3.5 kilowatts to about 1000 kilowatts, exhibits shaft speeds of between about 20,000 RPM and about 500,000 RPM during normal operation, and has a total mass of (i.e., combined mass of the fossil fuel burning components) between 1 kg to 250 kg.

[0038] As shown in FIG. IB, compressor 50 is a single-stage compressor that includes a hub 52 and a plurality of vanes 54 extending therefrom. Also, turbine 70 is a single-stage turbine that includes a hub 72 and a plurality of turbine blades 74 extending radially outwardly from hub 72. While compressor 50 and turbine 70 are each depicted as single stage within microturbine 10, it is contemplated that, in some embodiments, gas microturbine 10 may include a plurality of compressor stages and/or a plurality of turbine stages. Since engine 10 is a microturbine, it exhibits certain characteristics, such as those mentioned above. Another feature that is indicative of a microturbine is the peripheral diameter (maximum diameter) of the engine’s compressor and/or turbine which ranges from about 25 mm to about 300 mm. In this regard, compressor 50 and turbine 70 each have a peripheral diameter of about 25 mm to about 300 mm.

[0039] Shaft 60 includes a cylindrical center portion 62, tapered portions 64, and end portions or shank portions 66, as best shown in FIGs. IB and 9F. Tapered portions 64 are located between cylindrical center portion 62 and respective end portions 66. End portions 66 are also cylindrical and include a plurality of step-downs in diameter which forms first and second annular shoulders 66a-b (see FIG. 9F). As shown, center portion 62 has a larger diameter than the maximum diameter of each end portion 66.

[0040] Combustor 16 can be any type of combustor, such as a can-type or annular-type, for example. As such, combustor 16 includes one or more combustion chambers that each include a fuel injector (not shown) connected to a fuel source 18, as illustrated in FIG. 2. Combustor 16 is in fluid communication with compressor 50 and turbine 70. In this regard, combustor 16 is positioned downstream of compressor 50 and upstream of the turbine 70 such that compressed air produced by the compressor 50 can be introduced into combustor 16, and exhaust gas produced by combustor 16 can be expelled from combustor 16 and flowed over turbine blades 74 to induce rotation of shaft 60.

[0041] Microturbine 10 includes two bearings 150a-b, as shown in FIGs. 3B and 4B.

However, more than two bearings are contemplated, such as three or four bearings, for example. Each bearing 150a-b is a rolling bearing that includes a stator 152, a rotor 154, and a plurality of rolling elements 158 ( see e.g., FIG. 9E). In the embodiment depicted, rolling elements 158 are ball rollers or ball bearings. However, other types of rolling elements are contemplated, such as spherical rollers, cylindrical rollers, and the like. Rolling elements 158 are positioned within a raceway 156 between stator 152 and rotor 154. As shown in FIG. 9E, rotor 154 is positioned concentrically and internally offset from stator 152 such that the raceway 156 has an annular opening at opposite sides of bearing 150. As described in more detail below, an air-oil mist is sprayed into raceway 156 through one of such annular openings via the oil-distribution system in order to lubricate and clean bearing elements 158 during operation.

[0042] The circulating-oil or closed-loop oil distribution system includes an oil reservoir 20, a pump 30, an oil-supply circuit 200, an oil-scavenge circuit 300, an air-supply circuit 400, manifold blocks 110, and rotary purge seals 120, 130. Oil reservoir 20 is configured to hold a provision of oil. As described in more detail below, the oil distribution system transports oil in a closed loop from oil reservoir 20 to bearings 150a-b and from bearings 150a- b back to reservoir 20 so that the oil can be reused. In this regard, oil distribution system conserves the oil provision so that microturbine 10 can remain operational for extended periods of time.

[0043] Oil-supply circuit 200, as best shown in FIGs. 2, 3A, and 3B, is configured to supply oil to each bearing 150a-b in microturbine 10 in order to clean, cool, and lubricate such bearings. Oil-supply circuit 200 generally includes oil-supply manifolds 210 and a plurality of oil-supply conduits. In the depicted embodiment, microturbine 10 includes a first or front oil- supply manifold 210a and a second or rear oil- supply manifold 210b. However, in some embodiments, more than two oil-supply manifolds 210 may be provided depending on how many bearings 150 are utilized. Each oil-supply manifold 210a-b is ring/annular shaped and extends about a center axis thereof. In this regard, oil can circulate in a loop along each oil- supply manifold 210a-b. Such configuration helps create redundancy as each oil-supply manifold 210a-b can be fed by multiple conduits and simultaneously feed several other conduits.

[0044] The plurality of oil-supply conduits includes one or more inlet conduits 202, one or more bridging conduits 204, and one more outlet assemblies 220. As shown in FIGs. IB, 2, 3A and 3B, inlet conduits 202 includes a first and second inlet conduit 202a-b that are in communication with front oil-supply manifold 210a. However, in some embodiments inlet conduits 202a-b may communicate with rear manifold 210b. Such inlet conduits 202a-b may be directly connected to oil reservoir 20. Alternatively, inlet conduits 202a-b may be indirectly connected to oil reservoir 20 via pump 30, as illustrated in FIG. 2. In either circumstance, each inlet conduit 202a-b defines an inlet to oil-supply circuit 200. As such, in the particular embodiment depicted, first and second inlet conduits 202a-b are in a parallel arrangement (as opposed to a series arrangement) such that they provide redundancy in the event one conduit 202 becomes inoperable. As such, where further redundancy is desired, further inlet conduits 202 may be provided in parallel to feed oil-supply manifold 210a. However, it is contemplated that only one inlet conduit 202 may be provided.

[0045] As depicted in FIGs. 3 A and 3B, oil-supply circuit 200 includes a plurality of oil-supply outlet assemblies 220. More specifically, oil-supply circuit 200 includes first, second, and third oil-supply outlet assemblies 220a-c respectively coupled to each of the rear and front manifolds 210a-b and arranged at 120-degree intervals about a central axis defined by each manifold 210. While each manifold 210 has three outlet assemblies 210a-c coupled thereto, more or less of such assemblies 220 is contemplated. However, this arrangement provides for redundancy in that if one or more of outlet assemblies 220 becomes inoperable, each manifold 210 can continue to feed the operational assemblies 220. In this regard, outlet assemblies 220a-c are arranged in parallel.

[0046] Outlet assemblies 220a-c are each configured to supply oil to a respective bearing cooling jacket 330a-b (see FIGs. 4A and 4B) and an air-oil mist to a respective bearing raceway 156. In this regard, each outlet assembly 220a-c includes a first oil-supply outlet 230 and a second oil-supply outlet 240. As best shown in FIG. 9E, second oil-supply outlet 240 is coupled to and in communication with a respective oil-supply manifold 210 at one end thereof and with a cooling jacket 330 at another end thereof.

[0047] As also detailed in FIG. 9E, first oil-supply outlet 230 includes an intermediate conduit 231, an air-oil mist supply conduit 233, a plurality of venturis 234, and a nozzle 238. Intermediate conduit 231 is coupled to second oil- supply outlet 240 and extends therefrom. Air-oil mist supply conduit 233 is coupled to intermediate conduit 231 and extends therefrom in a direction transverse to intermediate conduit 231. Air-oil mist supply conduit 233 includes an air inlet aperture 232 at one end thereof and nozzle at the other end 238. As described in more detail below, air inlet aperture 232 communicates with air-supply circuit 400 such that oil flowing through first oil-supply outlet 230 is mixed with compressed air and atomized by nozzle 238 so as to form an air-oil mist. To assist in such atomization, first oil-supply outlet 230 includes first and second venturis 234a-b which are configured to accelerate the flow of oil toward nozzle 238. In this regard, first and second venturis 234a-b are upstream of nozzle 238 and each define an axis where the axis of first venturi 234a is angled relative to second venturi 234b. In addition, the axes of such venturis 234a-b are coplanar. Moreover, nozzle 238 is angled relative to first and second venturis 234a-b. This arrangement of venturis 234a-b and nozzle 238 is particularly beneficial as it helps maintain a continuous atomizing flow even in zero g environments.

[0048] Bridging conduits 204a-c extend in a front-rear direction and bridge front and rear manifolds 210a-b so that oil can be distributed from front manifold 210a to rear manifold 210b. Of course, in other embodiments where inlet conduits 202a-b feed rear manifold 210b, oil would be distributed from rear manifold 210b to front manifold 210a. Each bridging conduit 204a-c intersects and is coupled to a second oil-supply outlet 240 at each of front and rear manifolds 210a-b, as best shown in FIGs. 3 A and 3B. Since the depicted embodiment includes three oil-supply outlet assemblies 220a-c for each oil-supply manifold 210a-b, there are correspondingly three bridging conduits 204a-c. As such, where oil-distribution system includes more or less oil-supply outlet assemblies 220, there would respectively be more or less bridging conduits 204. Again, this provides redundancy in the event one or more bridging conduits 204a-c become inoperable, the remainder can continue to supply oil to the rear oil- supply manifold 210b.

[0049] Oil-scavenge circuit 300, as best shown in FIGs. 2, 4A, and 4B, is configured to recuperate oil taken up from oil reservoir 20 by the oil- supply circuit 200 and to return such oil back to the oil reservoir 20 so that it may be recycled. Oil-scavenge circuit 300 generally includes oil-scavenge manifolds 310, a plurality of conduits, a deaerator 90, and an oil filter 80. Microturbine 10, as shown, includes a first or front oil-scavenge manifold 310a and a second or rear oil-scavenge manifold 310b. However, in some embodiments, more than two oil-scavenge manifolds 310 may be provided depending on how many bearings 150 are utilized. Each oil-scavenge manifold 310a-b is ring/annular shaped and extends about a center axis thereof. In this regard, oil can circulate in a loop through each oil-scavenge manifold 310a- b. [0050] The plurality of oil-scavenge conduits includes one or more outlet conduits 302, one or more bridging conduits 304, and one more inlet assembly 320. As shown in FIGs. IB, 2, 4A and 4B, microturbine 10 includes first and second outlet conduit 302a-b that are in communication with front oil-scavenge manifold 310a. However, in some embodiments outlet conduits 302a-b may communicate directly with rear manifold 310b. Such outlet conduits 302a-b may be directly connected to oil reservoir 20. However, oil filter 80 and deaerator 90 are connected to such outlet conduits 302a-b so as to respectively filter the oil and to remove any compressed air in the conduits 302a-b that may have entered therein from the air-oil mist. While more or less oil-scavenge outlet conduits 302 may be provided, two are depicted in parallel to each other such that each conduit 302 defines an oil-scavenge circuit outlet and such that they provide redundancy in the event one conduit 302 becomes inoperable. As such, where further redundancy is desired, further oil-scavenge outlet conduits 302 may be provided in parallel to feed oil-supply manifold 310a. However, only one outlet conduit 302 may be provided. Although pump 30 is shown in FIG. 2 as being coupled to inlet conduits 202a-b of oil-supply circuit 200, it is contemplated that pump 30 may be alternatively coupled to outlet conduits 302a-b.

[0051] As shown in FIGs. 4A and 4B, oil-scavenge circuit 300 includes a plurality of oil-scavenge inlet assemblies 320. In the particular embodiment depicted, a first and second oil-scavenge inlet assembly 320a-b are respectively coupled to the rear and front oil-scavenge manifolds 310a-b and arranged about a central axis defined by each manifold 310a-b. While each manifold 310a-b includes two inlet assemblies 320a-b coupled thereto, more or less of such assemblies 320 is contemplated. However, more than one oil-scavenge inlet assembly 320 provides for redundancy. As such, inlet assemblies 320a-b are arranged in parallel such that the inoperability of one does not affect the other.

[0052] Oil-scavenge inlet assemblies 320a-b are each configured to transfer oil from a respective bearing cooling jacket 330a-b and oil from raceway 156 from a respective bearing 150a-b. In this regard, each oil-scavenge inlet assembly 320a-b includes a first oil-scavenge inlet 340 and a second oil-scavenge inlet 354. As best shown in FIG. 9F, first oil-scavenge inlet 340 is coupled to and in communication with a respective oil-scavenge manifold 310a at one end thereof and in communication with bearing 156 raceway at another end thereof.

[0053] Second oil-scavenge inlet 350 forms a crescent shaped aperture that communicates with cooling jacket 330 and an intermediate conduit 355 that couples the crescent shaped aperture 350 with the first oil-scavenge inlet 340. In this regard, oil exiting cooling jacket 330 and oil and air exiting raceway 156 can be transported to one or both manifolds 310a-b for distribution through oil-scavenge circuit 300. It is noted that each first oil-scavenge inlet 340 lies in a plane defined by its respective oil-scavenge manifold 310 while each second oil-scavenge outlet 350 is offset from such plane in a front-rear direction. This is generally because cooling jackets 330a-b in the assembled microturbine 10 are offset from oil- scavenge manifolds 310a-b.

[0054] Oil-scavenge bridging conduits 304a-b extend in a front-rear direction and bridge the front and rear oil-scavenge manifolds 3 lOa-b so that oil can be distributed from rear manifold 310b to front manifold 310a. Of course, in other embodiments where oil-scavenge outlet conduits 302a-b are coupled to rear manifold 310b, oil would be distributed from front manifold 310a to rear manifold 310b. In the depicted embodiment, each bridging conduit 304a- b is coupled to an oil-scavenge inlet assembly 320 at each of the front and rear manifolds 310a- b, as best shown in FIGs. 4A and 4B. Since the depicted embodiment includes two oil-scavenge inlet assemblies 320a-b per each oil-scavenge manifold 310a-b, there are correspondingly two oil-scavenge bridging conduits 304a-b. As such, where oil-distribution system includes more or less oil-scavenge inlet assemblies 320, there would respectively be more or less bridging conduits 304.

[0055] Air- supply circuit 400 generally includes an air source, air- supply manifolds

410, air-supply conduits, and an air-tunnel or shaft tunnel air volume 420. In the embodiment depicted, the air source is compressor 50 which supplies bleed air 55 therefrom to air-supply circuit, as illustrated in FIG. 2. However, other embodiments may include a separate compressor dedicated to air-supply circuit 400.

[0056] Similar to oil-supply and oil-scavenge manifolds 210, 310, air-supply manifolds

410 are ring/annular shaped and extend about a central axis thereof. Micro turbine 10 includes a first and second air- supply manifold 410a-b. However, in other embodiments, more air- supply manifolds 410 may be provided depending on the number of bearings 150.

[0057] The plurality of air- supply conduits includes a bridging air- supply conduit 404 and an air-tunnel conduit 406. Bridging conduit 404 is in communication with both the first and second air- supply manifolds 410a-b. Air- tunnel conduit 406 is coupled to bridging conduit 404 and extends therefrom to air tunnel 420. [0058] Air tunnel 420 is defined by housing 12 and shaft 60, as best shown in FIGs. 9D and 9F. In this regard, air tunnel 420 is volume of air that surrounds shaft and extends along shaft from front and rear bearings 150a-b. Compressed air is supplied to air tunnel 420 via air- tunnel conduit 406 so that the compressed air circulates through air tunnel 420. This compressed air helps provide cooling to shaft 60 and to bearings 150a-b. In addition, the compressed air provides a positive pressure that helps seal bearings 150a-b to prevent oil from inadvertently escaping and being lost to the engine’s internal environment.

[0059] FIGs. IB, 6, and 9A-9F depict manifold blocks or manifold bodies 110.

Microturbine 10 includes a first or front manifold block 110a and a second or rear manifold block 110b, as best shown in FIG. IB. Each manifold block 110 is ring/annular shaped and generally includes an interior side and exterior side. The interior side defines an opening that is sized to receive a bearing 150 and shaft 60 therein. Manifold block 110 also includes a flange 114 at one side thereof that partially extends radially inwardly into the opening.

[0060] The exterior side of each manifold block includes a plurality of circumferential grooves or recesses that extend into an outer surface of manifold block 110 such that each groove forms one of the manifolds 210, 310, 410 previously described herein. For example, with regard to front side manifold block 110a, a first groove forms oil-supply manifold 210a, a second groove forms oil-scavenge manifold 310a, and a third groove forms air-supply manifold 410a, as best shown in FIGs. 6 and 9E. The exterior side of manifold block 110a also includes a plurality of damping grooves or damping pockets 112 that extend into the outer surface of manifold block 110a. Such damping grooves 112 form a first set of damping grooves which are positioned such that a first damping groove 112a is positioned adjacent oil-scavenge manifold 310a, a second damping groove 112b is positioned between oil-scavenge manifold 310a and oil-supply manifold 210a, and a third damping groove 112c is positioned between oil-supply manifold 210a and air-supply manifold 410a, as best shown in FIG. 9E.

[0061] The interior side of manifold block 110a includes a groove that forms the cooling jacket 310a as best shown in FIGs. 9C and 9E. The interior side of manifold block 110a also includes second set of damping grooves or damping pockets 116, as best shown in FIG. 9E. Damping grooves 116 are arranged such that they flank cooling jacket 330a. Damping grooves 112a-c and 116 are configured to receive oil therein to provide a cushion at the interior and exterior interfaces of manifold block 110a to dampen vibrations generated by the high speed rotation of shaft 60. [0062] Each manifold block 110 also includes several components of oil-supply, oil- scavenge, and air-supply circuits 200, 300, 400. As shown in FIGs. 9A-9F, manifold block 110a includes each of oil-supply outlet assembly 220a-c (see FIG. 9E), oil-scavenge input assembly 320a-b (see FIG. 9F), and portions 204’, 304’, 404’ of oil-supply, oil-scavenge, and air-supply bridging conduits 204, 304, 404. These features have been previously described. However, it is noted that the portion 404’ of air-supply bridging conduit 404 that is formed within manifold block 110a extends entirely through manifold block 110a from one side to the other in order to feed air-supply manifold 410a, as shown in FIG. 9D. It is also noted that oil- mist supply conduit 233 extends radially within flange 114 while nozzle 238 opens through flange 114 in a relatively front-rear direction. This arrangement allows nozzle 238 to be directed into a bearing raceway 156, as is described further below.

[0063] The exemplary manifold block 110 described herein may be formed layer-by- layer using an additive layer manufacturing (AFM), i.e., 3D printing, process so that no separate connection mechanism is necessary to bring together any aspect of such device. In addition, as described and as shown, the portions of bridging conduits 204, 304, 404 that extend between manifold blocks llOa-b are each separate components that are separately connected to manifold blocks llOa-b. However, in other embodiments of microturbine 10, bridging conduits 204, 304, 404 may be formed together in a single, monolithic component that may be coupled to each manifold block llOa-b. In this regard, a bridging sleeve (not shown) may be additively manufactured using an AFM process to have a solid monolithic construction with passageways extending therethrough in the arrangement of bridging conduits 204, 304, 404 as is shown in FIG. 8.

[0064] In some examples, AFM processes are powder-bed based and involve one or more of selective laser sintering (SFS), selective laser melting (SFM), and electron beam melting (EBM). Other methods of AFM, which can be used to form the herein described manifold blocks 110 and/or bridging sleeve, include binder jet printing in which a temporary binding material is selectively deposited layer-by-layer in conjunction with a powder bed to form a green part that is later sintered in a sintering oven to remove the binding material and sinter the bound powder to create a permanent shape.

[0065] When employing powder-bed based technologies, articles are produced in layer- wise fashion according to a predetermined digital model of such articles by heating, e.g., using a laser or an electron beam, or temporarily binding multiple layers of powder that are dispensed one layer at a time. Such powders are preferably metallic and may include stainless steel, titanium, and the like. The powder is sintered in the case of SLS technology and melted in the case of SLM technology, by the application of laser energy that is directed in raster-scan fashion to portions of the powder layer corresponding to a cross section of the article. After the sintering, melting, or binding of the powder on one particular layer, an additional layer of powder is dispensed, and the process repeated, with sintering, melting, or binding taking place between the current layer and the previously laid layers until the article is complete. The powder layers similarly may be heated with EBM technology.

[0066] Each bearing 150 is provided with a pair of rotary purge seals 120, 130. As described, microturbine 10 includes first and second bearings 150a-b. Thus, microturbine 10 includes first and second pairs of rotary purge seals 120, 130. Each pair of rotary purge seals includes a first side seal 120 and a second side seal 130. Thus, for the front side bearing 150a, first side seal 120 is a rear side seal 120a and the second side seal 130 is a front side seal 130a. Each rotary purge seal 120, 130 is made from a metallic material such as stainless steel, titanium, and the like, for example.

[0067] FIGs 7 and 9D-9F depict the first side seal 120. First side seal 120 is annular shaped and includes a first portion or hub 128, a second portion or flange 126, and an opening 126 extending through hub 128 which is sized to receive an end portion 66 of shaft 60. Hub 128 projects from flange 126 in a front-rear direction which forms an oil-sling surface 121 that extends along hub 128 and flange 126 at one side of seal 120. Such oil-sling surface 121 has a concavely curved portion 124 and a planar portion 125. Concavely curved portion 124 is intersected by planar portion 125 where planar portion 125 extends from a radial periphery of flange 126 in a direction substantially perpendicular with a central axis of rotary seal 120, as best shown in FIG. 9E. Oil-sling surface 121 redirects oil exiting raceway 156 of bearing 150 toward manifold block 110 and an oil-scavenge inlet 350, as described further below. Flange 126 defines a radial periphery of seal 120 and includes a cylindrical peripheral or seal surface 122 at the periphery which includes a plurality of circumferential blades that each extend about the central axis. In this regard, peripheral surface 122 is a bladed surface. Such blades may be angled in a direction away from hub 128, such as at an angle of about 1 to 3 degrees, for example, and interface with housing 12 to help seal raceway 156 from air and oil leakage. [0068] FIGs. 9D-9F depict second side seal 130. Second side seal 130 is annular shaped and includes a first portion or hub 138, a second portion or flange 136, and an opening extending therethrough sized to receive an end portion 66 of shaft 60. Hub 138 projects from flange 136 in a front-rear direction such that hub 138 exhibits a cylindrical seal surface 132 that includes a plurality of circumferential blades that each extend about the central axis. In addition, flange 136 defines a radial periphery of seal 130 and includes a cylindrical peripheral or seal surface 134 at the periphery which includes a plurality of circumferential blades that each extend about the central axis. In this regard, seal surface 132 of hub 138 forms a first bladed surface and seal surface 134 of flange 136 forms a second bladed surface. The blades of first and second bladed surfaces 132, 134 may be angled in the same direction. For example, the blades of first bladed surface 132 may extend in a direction toward flange 136 at an angle of about 1 to 3 degrees, and the blades of second bladed surface 134 may extend in a direction away from hub at an angle of about 1 to 3 degrees. In the embodiment depicted, the blades of first bladed surface 132 extend at 1 degree while the blades of second bladed surface 134 extend at 2 degrees.

[0069] As assembled, compressor 50, turbine 70, rotors 154 of front and rear bearings

150a-b, and rotary purge seals 120, 130 are connected to shaft 60 and form a rotating assembly. Other elements, such as housing 12, manifold blocks llOa-b, and stators 152 of front and rear bearings 150a-b comprise a static assembly. The arrangement of compressor 50, front bearing 150a, and rotary purge seals 120a, 130a relative to shaft is depicted in FIGs. 9D-9F. In this arrangement, first seal 120a is press-fit to end portion 66 of shaft 60 such that hub 128 abuts first annular shoulder 68a of shaft 60 and flange 126 extends radially outwardly therefrom. Front bearing 110a is connected to shaft 60 such that rotor 70 is positioned against hub 128 of first seal 120a and is press-fit to end portion 66 of shaft 60. Second seal 130a is press-fit to end portion 66 of shaft 60 such that hub 138 abuts rotor 154 of bearing 150a and is positioned adjacent to or abuts second shoulder 68b of shaft 60. Flange 136 extends radially outwardly such that bladed seal surface 134 interfaces with housing 12 to form an air-tight seal therebetween, as shown in FIG. 9E. Compressor 70 is also press-fit to end portion 66 of shaft 60 and second seal 130a.

[0070] Front manifold block 110a is positioned over bearing 150a and seal 120a such that bearing 150a and seal 120a are surrounded by manifold block 110a. Additionally, manifold block 110a is mounted to stator 152 such that cooling jacket 330a and damping grooves 116 interface with a peripheral surface of stator 152. Manifold block 110a is also mounted to housing 12 at the exterior side thereof such that damping grooves 112a-c and oil-supply, oil- scavenging, and air-supply manifolds 210, 310, 410 interface with housing 12, as best shown in FIG. 9E. Damping grooves 112a-c at the interfaces of stator 152 and housing 12 help damp vibrations produced by shaft 60. Flange 114 of manifold block 110a is positioned against a side of stator 152 and between stator 152 and flange 136 of seal 130a. In this regard, flange 136 at least partially defines air-supply manifold 410a, as shown in FIG. 9E. Flange 114 of manifold block 110a extends radially inwardly such that it partially overlaps raceway 156 at the front side of bearing 150a and such that nozzle 238 is directed toward raceway 156 so that an air-oil mist may be sprayed therein. Flange 114 also interfaces with first seal surface 132 of seal 130a. In this regard, bladed seal surface 132 contacts flange 114 to seal the front side of raceway 156 to prohibit air and oil from escaping through this interface. In addition, manifold block 110a is positioned over first seal 120a so that first oil-scavenge inlets 340 are aligned with oil-sling surface 121 such that oil escaping raceway 156 may be slung by oil-sling surface 121 into first oil-scavenge inlets 340.

[0071] A portion of housing 12 is positioned between manifold blocks llOa-b and seals 120a-b, respectively. In this regard, bladed seal surface 122 of seals 120a-b interface housing 12 and rotates relative thereto. Air tunnel 420 is defined between housing 12 and shaft 60 and between seals 120a-b. . In this regard, air shaft 402 provides compressed air at an opposite side of seals 120a-b from raceways 156 of bearings 150a-b, respectively. This provides positive air pressure at the rear side of bearing 150a and front side of bearing 150b, which helps prevent oil from escaping into micro turbine’s internal environment.

[0072] The rear of microturbine 10 is arranged similar to that of the front with the notable exception being that turbine 70 is connected to the rear end portion 66 of the shaft 60. [0073] As illustrated in FIG. 8, oil-supply, oil-scavenge, and air-supply manifolds

210a, 310a, 410a are positioned about front bearing 150a such that air manifold 410a is closest to compressor 50 and oil-supply manifold 210a is positioned between oil-scavenge and air- supply manifolds 310a, 410a. Similarly, oil-supply, oil-scavenge, and air-supply manifolds 210b, 310b, 410b are positioned about rear bearing 150b such that air manifold 410b is closest to turbine 70 and oil-supply manifold 210b is positioned between oil-scavenge and air-supply manifolds 310b, 410b. Bridging conduits 204, 304, 404 and air tunnel 420 extend in a front- rear direction over shaft 60 and couple to front and rear mounting blocks llOa-b in order to pass air and oil back and forth between the front and rear of microturbine 10. [0074] Microturbine 10 is started up such that compressor 50 feeds compressed air into combustor 16 where it is combusted and exhausted over turbine 70 in order to drive shaft 60 at upwards of 500,000 RPM. In operation, pump 30 pumps oil from oil reservoir 20 through oil- supply inlet conduits 202a-b to front oil-supply manifold 210a, as illustrated in FIG. 2. FADEC 40, which may be a commercially available FADEC, controls pump 30 and monitors the oil’s condition. Oil enters into front oil-supply manifold 210a via oil-supply inlet conduits 202a-b and is circulated within oil-supply manifold 210a in a circular loop about front bearing 150(a). Oil that circulates within manifold 210a is expelled from manifold 210a into each of the oil- supply outlet assemblies 220 and oil-supply bridging conduits 204. Oil is then passed through first oil-supply inlet 230 toward nozzle 238 thereof where it is mixed with compressor bleed air that is supplied via air-supply manifold 410a. This oil is atomized into an air-oil mist which is sprayed into raceway 156 of front bearing 150a in order to clean, cool, and lubricate bearing elements 158. Oil is also passed through second oil-supply outlets 240 into cooling jacket 330a which surrounds stator 152 in order to further cool bearing 150a. Oil that is expelled from front manifold 210a into bridging conduits 204 is transported in a rear direction into rear oil- supply manifold 210b where it is similarly transported into oil-supply outlet assemblies 220 at the rear manifold 210b and into raceway 156 of rear bearing 150b and cooling jacket 330b thereof. FIG. 10 depicts the volumes at the front and rear bearings 150a-b that are wetted by the oil-air mist produced by oil- supply circuit 200.

[0075] The oil from the air-oil mist that is sprayed into raceway 156 of rear bearing

150b eventually accumulates into larger droplets which are slung by oil-sling surface 121 of seal 120b into first oil-scavenge inlets 340 where the oil is then transported to rear oil-scavenge manifold 310b and oil-scavenge bridging conduits 304. Air is also introduced into oil-scavenge circuit 300 via such inlets 340. This air is removed from oil-scavenge circuit 300 via deaerator 90. Oil that circulates through cooling jacket 330b of rear bearing is transported from therefrom into second oil-scavenge inlet 350 and similarly distributed to rear-oil scavenge manifold 310b and bridging conduits 304. Oil that is transported via oil-scavenge bridging conduits 304 is transported to the front oil-scavenge manifold 310a where it is combined with oil expelled from raceway 156 of front bearing 150a and cooling jacket 330a thereof in a similar manner as that just described. From there, the oil is transported from front oil-scavenge manifold 310a to oil- scavenge outlet conduits 302a-b which then transports the oil to oil reservoir 20. Along the way, the oil is filtered via oil filter 80 and oil-scavenge circuit 300 is deaerated by deaerator 90. Once the oil reaches the oil reservoir 20, the oil has cycled through the closed loop of the oil-distribution system and can be cycled continuously through the oil-distribution system during operation of microturbine 10 as just described.

[0076] As shaft 60 rotates, turbine 70, compressor 50, purge seals 120, 130 and bearing stators 154 rotate along with it. In the event shaft produces vibrations, such vibrations are damped at the manifold block and housing interface and at the bearing and manifold block interface via damping grooves 112 and 116, respectively. Damping grooves 112 and 116 contain oil therein which help facilitate such damping. This oil is introduced into damping grooves 112 and 116 via oil-supply circuit 200.

[0077] Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.