GAS TURBINE PROPULSION SYSTEM
A gas turbine propulsion system includes a shroud that defines a fluid flow path. A gas turbine engine in the fluid flow path includes a compressor, a combustor downstream from the compressor, and a turbine downstream from the combustor. An electric generator in the fluid flow path defined by the shroud includes a rotor coaxially aligned with the turbine. A propulsor is upstream from the gas turbine engine, and an electric motor is operably coupled to the propulsor to rotate the propulsor. The propulsor is rotationally isolated from the gas turbine engine so that the propulsor rotates independently from operation of the gas turbine engine.
The present application is a Continuation of U.S. Patent Application entitled “A Gas Turbine Propulsion System,” Ser. No. 17/080,361 filed on Oct. 26, 2020, all of which is hereby incorporated herein by reference in its entirety for all purposes. Any disclaimer that may have occurred during prosecution of the above-referenced application is hereby expressly rescinded.
FIELD OF THE INVENTIONThe present invention generally involves a gas turbine propulsion system. Particular embodiments of the propulsion system may be incorporated into an aircraft as a turboprop or turbofan engine.
BACKGROUND OF THE INVENTIONConventional aircraft propulsion systems often include a gas turbine engine that produces thrust and mechanical power. The gas turbine engine includes a compressor, one or more combustors downstream from the compressor, and a turbine downstream from the combustor(s). Ambient air enters the compressor as a working fluid, and one or more stages of rotating blades and stationary vanes in the compressor progressively increase the pressure of the working fluid. The working fluid exits the compressor and flows to the combustors where it mixes with fuel and ignites to generate combustion gases having a high temperature, pressure, and velocity. The combustion gases flow to the turbine where they produce work by rotating the turbine before exhausting from the turbine to provide thrust. A spool or shaft connects the turbine to a propulsor, such as a propeller or a fan, so that rotation of the turbine drives the propulsor to generate additional thrust.
The efficiency of turboprop and turbofan systems naturally depends on the combined efficiency of the gas turbine engine and associated propulsor. Gas turbine engines are generally more efficient at higher operating speeds or power levels, while propellers and fans are generally more efficient at slower operating speeds or power levels. To enhance the combined efficiency, existing turboprop and turbofan systems may incorporate multiple shafts (spools), gears, and/or a transmission to allow the gas turbine to rotate at substantially higher speeds than the propulsor. However, the multiple shafts, gears, and/or transmissions add substantial weight to an aircraft design. In addition, multiple shafts, gears, and/or transmissions generally require additional support systems, such as lube oil systems, to provide lubrication and cooling, and these additional support systems increase the cost of assembly, maintenance, and repairs. Moreover, the mechanical linkage between the gas turbine engine and the propulsor necessarily limits whatever optimized efficiency is selected to a single operating speed or condition for the gas turbine and propulsor. Therefore, the need exists for an improved propulsion system that enhances the combined efficiency of both the gas turbine engine and the propulsor at multiple speeds and operating conditions.
BRIEF DESCRIPTION OF THE INVENTIONAspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention.
One embodiment of the present invention is a gas turbine propulsion system that includes a shroud that defines a fluid flow path. A gas turbine engine in the fluid flow path includes a compressor, a combustor downstream from the compressor, and a turbine downstream from the combustor. An electric generator in the fluid flow path defined by the shroud includes a rotor coaxially aligned with the turbine. A propulsor is upstream from the gas turbine engine, and an electric motor is operably coupled to the propulsor to rotate the propulsor. The propulsor is rotationally isolated from the gas turbine engine so that the propulsor rotates independently from operation of the gas turbine engine.
An alternate embodiment of the present invention is a gas turbine propulsion system that includes a gas turbine engine having a compressor, a combustor downstream from the compressor, and a turbine downstream from the combustor. An electric generator is operably connected upstream from the gas turbine engine and includes a rotor coaxially aligned with the turbine. A shaft rotatably connects the turbine to the rotor of the electric generator so that the turbine and the rotor rotate at the same speed. A propulsor is upstream from the electric generator, and an electric motor is operably coupled to the propulsor to rotate the propulsor. The propulsor rotates independently from operation of the gas turbine engine.
In yet another embodiment of the present invention, a gas turbine propulsion system includes a shroud that defines a fluid flow path. A gas turbine engine in the fluid flow path includes a compressor, a combustor downstream from the compressor, and a turbine downstream from the combustor. An electric generator is operably connected upstream from the gas turbine engine and includes a rotor. A shaft rotatably connects the turbine to the rotor of the electric generator so that the turbine and the rotor rotate at the same speed. A propulsor is upstream from the gas turbine engine, and an electric motor is operably coupled to the propulsor to rotate the propulsor. The electric motor and the propulsor are rotationally isolated from the gas turbine engine so that the propulsor rotates independently from operation of the gas turbine engine.
Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification.
A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:
Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
As used herein, the terms “first,” “second,” and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. As used herein, the terms “upstream” and “downstream” refer to the location of items with reference to the direction of fluid flow in a fluid pathway. For example, item A is “upstream” from item B and item B is downstream from item A if fluid normally flows from item A to item B. As used herein, “axial” refers to the direction of the longer axis of a component, “radial” refers to the direction perpendicular to the axial direction, and “circumferential” refers to the direction around a component.
Embodiments of the present invention include a gas turbine propulsion system that may be incorporated into any vehicle needing propulsion. For example, the gas turbine propulsion system may be housed in a nacelle and attached to the fuselage or wing of an aircraft. The gas turbine propulsion system generally includes a gas turbine engine and a propulsor. The gas turbine engine generally includes a compressor, a combustor, and a turbine, and the propulsor may be a propeller or a fan enclosed by a shroud or cowling. The propulsor is rotationally isolated from the gas turbine engine so that rotation of the propulsor is completely independent from the gas turbine engine. As used herein, the phrase “rotationally isolated” means that no mechanical coupling exists between two components to transfer rotation between the two components, in this case, the gas turbine engine and the propulsor. As a result, rotation of the propulsor is completely independent from operation of the gas turbine engine, allowing each to operate at its most efficient speed independently from the other.
Particular embodiments of the present invention may include additional design features to reduce the weight, manufacturing cost, and/or maintenance associated with the gas turbine engine. For example, the gas turbine engine may be a single-spool gas turbine engine. As used herein, a “single-spool gas turbine engine” means a gas turbine engine in which a single spool or shaft, which may include multiple segments, connects the turbine to the compressor so that the turbine and compressor rotate at the same speed. The single spool or shaft may also connect the gas turbine engine to an electric generator so that the turbine and electric generator rotate at the same speed. The use of a single spool or shaft reduces the weight and parts associated with the gas turbine engine, simplifying manufacture, maintenance, and repairs compared to multi-spool and/or geared systems. In addition, the reduced weight associated with a single-spool gas turbine engine reduces the need for a separate lube oil system to lubricate and cool the rotating components of the gas turbine engine. As a result, in particular embodiments the gas turbine engine may include non-lubricated bearings and/or an integrally bladed rotor that further reduce manufacturing, maintenance, and repair costs. As used herein, “non-lubricated bearings” means that the bearings are not supplied external lubrication, such as from a lube oil system, during operation of the gas turbine engine.
Gas turbine engines are generally more efficient at higher turbine inlet temperatures which may damage the rotating blades in the turbine. As a result, the rotating blades are often hollow so that cooling may be supplied through the rotor to the hollow rotating blades to prevent damage from the higher turbine inlet temperatures. In the present invention, the rotational isolation between the gas turbine engine 12 and the propulsor 18 allows the gas turbine engine 12 to operate at lower turbine inlet temperatures than what may otherwise be preferred to achieve a desired efficiency for the gas turbine engine 12. The lower turbine inlet temperatures in turn reduce the need for internal cooling to the rotating blades 40 in the turbine 30. As a result, in particular embodiments of the present invention, the rotor 38 in the turbine 30 may be an integrally bladed rotor 38 or “blisk” in which the rotating blades 40 are solid and integrally formed as a solid piece with the rotor 38. The integrally bladed rotor 38 may be manufactured by additive printing, casting, machining from a solid piece of material, or welding individual blades 40 to the rotor 38, as is known in the art. The resulting integrally bladed rotor 38 reduces the complexity, weight, and cost of manufacturing and assembly by avoiding the intricacy of hollow blades, dovetail connections to the rotor, and forced cooling through the rotor and blades.
The gas turbine engine 12 may include one or more spools or shafts that rotationally couple the turbine 30 to the compressor 26, as is known in the art. In a multi-spool gas turbine engine, for example, the compressor and the turbine may each include a high pressure stage and a low pressure stage, and a first spool may connect the high pressure stage of the turbine to the high pressure stage of the compressor, while a second spool may connect the low pressure stage of the turbine to the low pressure stage of the compressor. In this manner, each turbine stage drives the corresponding compressor stage with a separate spool, with one spool inside the other spool.
In the particular embodiment shown in
The single-spool gas turbine engine 12 shown in
The electric generator 14 may be located outside of the shroud 20 or remote from the fluid flow path 24, and the present invention is not limited to a particular location for the electric generator 14 unless specifically recited in the claims. In the particular embodiment shown in
The use of a gas turbine engine to drive an electric generator is known in the art. For example, U.S. Pat. No. 6,962,057 describes a micro gas turbine in which a single-spool gas turbine engine drives a coaxially aligned electric generator to produce 20-100 kW of power. The power output of the electric generator may be increased by increasing the strength of the magnetic field, e.g., by incorporating larger permanent magnets on the rotor. However, the additional mass associated with larger permanent magnets produces larger centrifugal forces that tend to separate the permanent magnets from the rotor, particularly at the high rotational speeds associated with a single-spool gas turbine engine that directly drives the electric generator. Therefore, gas turbine engines that drive higher power output generators generally require multiple spools or shafts, gears, and/or transmissions that allow the electric generator to rotate at substantially lower speeds than the turbine in the gas turbine engine to prevent the centrifugal forces from separating the permanent magnets from the rotor.
In the particular embodiment shown in
The function of the means for holding the permanent magnets 52 in place on the rotor 48 during operation of the gas turbine engine 12, the turbine 30, and/or the turbine rotor 38 is to prevent movement between the rotor 48 and the permanent magnets 52 during operations. The structure for performing this function may be any mechanical coupling with the permanent magnets 52 that prevents the permanent magnets 52 from moving with respect to the rotor 48. For example, the mechanical coupling may be one or more clamps, bolts, screws, or dovetail fittings that mechanically couple some or all of the permanent magnets 52 to the rotor 48. Alternately, the mechanical coupling may be a series of rails or other projections that extend radially from the rotor 48 combined with an overwrap that circumferentially surrounds the permanent magnets 52. The rails or other projections engage with some or all of the permanent magnets 52 to transfer torque between the rotor 48 and the permanent magnets 52 and prevent the permanent magnets 52 from moving circumferentially with respect to the rotor 48. In particular embodiments, the rails or other projections may be contoured, ribbed, tapered, or flanged to match a complementary recess in the permanent magnets 52. The overwrap that circumferentially surrounds the permanent magnets 52 provides sufficient centripetal force against the permanent magnets 52 to offset the centrifugal forces caused by rotation of the rotor 48 to prevent the permanent magnets 52 from moving radially away from the rotor 48. The overwrap may be a fiber or composite material sprayed or wrapped around the outer circumference of the permanent magnets 52. In combination, the rails or projections and overwrap thus securely hold the permanent magnets 52 in contact with the rotor 48 to prevent circumferential and radial movement between the rotor 48 and the permanent magnets 52 during operations.
The embodiments shown in
Alternately, as in
The electric motor 16 provides the sole driving force for the propulsor 18. The electric motor 16 generally includes a rotor 70 and a stator 72, and current flow disrupts a magnetic field between the two to convert electrical energy into mechanical energy, as is known in the art. In the particular embodiment shown in
The electric motor 16 may be located outside of the shroud 20 or remote from the fluid flow path 24, and the present invention is not limited to a particular location for the electric motor 16 unless specifically recited in the claims. In the particular embodiment shown in
The propulsor 18 may be a propeller that rotates outside of the shroud 20 or a fan enclosed by the shroud 20 or cowling. In either event, the propulsor 18 may be either axially offset from or coaxially aligned with the gas turbine engine 12 and/or electric motor 16, depending on the particular design. In the particular embodiment shown in
Referring again to
The embodiments previously described and illustrated with respect to
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
Claims
1. A gas turbine propulsion system, comprising:
- a shroud that defines a fluid flow path;
- a gas turbine engine in said fluid flow path, wherein said gas turbine engine comprises a compressor, a combustor downstream from said compressor, and a turbine downstream from said combustor;
- an electric generator in said fluid flow path defined by said shroud and upstream from said gas turbine engine, wherein said electric generator comprises a rotor coaxially aligned with said turbine;
- a propulsor upstream from said gas turbine engine; and
- an electric motor operably coupled to said propulsor to rotate said propulsor;
- wherein said propulsor is rotationally isolated from said gas turbine engine so that said propulsor rotates independently from operation of said gas turbine engine.
2. The gas turbine propulsion system as in claim 1, wherein said turbine of said gas turbine engine comprises an integrally bladed rotor.
3. The gas turbine propulsion system as in claim 1, wherein said electric motor is coaxially aligned with said electric generator.
4. The gas turbine propulsion system as in claim 1, wherein said propulsor is coaxially aligned with said electric generator.
5. The gas turbine propulsion system as in claim 1, wherein said gas turbine engine is a single-spool gas turbine engine.
6. The gas turbine propulsion system as in claim 1, wherein said gas turbine engine comprises a shaft that rotatably connects said turbine to said rotor of said electric generator so that said turbine and said rotor rotate at the same speed.
7. The gas turbine propulsion system as in claim 6, further comprising a plurality of non-lubricated bearings that rotatably support said shaft.
8. A gas turbine propulsion system, comprising:
- a gas turbine engine, wherein said gas turbine engine comprises a compressor, a combustor downstream from said compressor, and a turbine downstream from said combustor;
- an electric generator operably connected upstream from said gas turbine engine, wherein said electric generator comprises a rotor coaxially aligned with said turbine;
- a shaft that rotatably connects said turbine to said rotor of said electric generator so that said turbine and said rotor rotate at the same speed;
- a propulsor upstream from said electric generator;
- an electric motor operably coupled to said propulsor to rotate said propulsor;
- wherein said propulsor rotates independently from operation of said gas turbine engine.
9. The gas turbine propulsion system as in claim 8, wherein said turbine of said gas turbine engine comprises an integrally bladed rotor.
10. The gas turbine propulsion system as in claim 8, wherein said electric motor is coaxially aligned with said electric generator.
11. The gas turbine propulsion system as in claim 8, wherein said propulsor is coaxially aligned with said electric generator.
12. The gas turbine propulsion system as in claim 8, wherein said gas turbine engine is a single-spool gas turbine engine.
13. The gas turbine propulsion system as in claim 12, further comprising a plurality of non-lubricated bearings that rotatably support said single-spool gas turbine engine.
14. A gas turbine propulsion system, comprising:
- a shroud that defines a fluid flow path;
- a gas turbine engine in said fluid flow path, wherein said gas turbine engine comprises a compressor, a combustor downstream from said compressor, and a turbine downstream from said combustor;
- an electric generator operably connected upstream from said gas turbine engine, wherein said electric generator comprises a rotor;
- a shaft that rotatably connects said turbine to said rotor of said electric generator so that said turbine and said rotor rotate at the same speed;
- a propulsor upstream from said gas turbine engine; and
- an electric motor operably coupled to said propulsor to rotate said propulsor;
- wherein said electric motor and said propulsor are rotationally isolated from said gas turbine engine so that said propulsor rotates independently from operation of said gas turbine engine.
15. The gas turbine propulsion system as in claim 14, wherein said turbine of said gas turbine engine comprises an integrally bladed rotor.
16. The gas turbine propulsion system as in claim 14, wherein said rotor is coaxially aligned with said compressor.
17. The gas turbine propulsion system as in claim 14, wherein said electric motor is coaxially aligned with said electric generator.
18. The gas turbine propulsion system as in claim 14, further comprising a plurality of non-lubricated bearings that rotatably support said shaft.
19. The gas turbine propulsion system as in claim 14, wherein said gas turbine engine is a single-spool gas turbine engine.
Type: Application
Filed: Dec 14, 2022
Publication Date: Apr 20, 2023
Inventors: Francis O'Neill (Jupiter, FL), Anthony A. Hartzheim (Palm Beach Gardens, FL)
Application Number: 18/065,984