Patent Application
20120201657
The present disclosure on relates generally to gas turbine engine systems and specifically to a method and apparatus that can provide control of power turbine over-speed and engine braking to a vehicle.
There is a growing requirement for alternate fuels for vehicle propulsion. These include fuels such as natural gas, bio-diesel, ethanol, butanol, hydrogen and the like. Means of utilizing fuels needs to be accomplished more efficiently and with substantially lower carbon dioxide emissions and other air pollutants such as NOxs.
The gas turbine or Brayton cycle power plant has demonstrated many attractive features which make it a candidate for advanced vehicular propulsion. Gas turbine engines have the advantage of being highly fuel flexible and fuel tolerant. Additionally, these engines burn fuel at a lower temperature than reciprocating engines so produce substantially less NOxs per mass of fuel burned.
However, the gas turbine does not allow the normal “engine braking” or “compression braking” feature that is extensively used in piston-type engines. The utility of these engines, especially for use in large vehicles such as Class 8 trucks, can be substantially improved by providing an engine braking capability analogous to the Jacobs brake used by piston engine powered trucks.
In addition, configurations of gas turbine engines which employ a free power turbine require additional means to control over-speeding of the free power turbine. Such over-speeding can occur in vehicle or other applications, for example, when the load is abruptly reduced or disconnected.
U.S. Pat. No. 3,817,343 “Installation for Brake of Motor Vehicles Which Are Driven from a Gas Turbine” discloses a means for the braking of motor vehicles which are driven by a gas turbine engine comprising a free output or free power turbine, by means of a rotary compressor that is arranged in or parallel to the transmission and is in the power path from the free working turbine to the driven wheels. U.S. Pat. No. 3,817,343 does not teach how to control the braking force of the braking compressor nor how to utilize the output of the braking compressor for recovering useful energy.
There thus remains a need for compact, controllable engine braking apparatus to improve engine braking performance so as to assist the vehicle's foundation braking system. There is also a need, for vehicles powered by gas turbine engines, for a means of over-speed control of the free power turbine.
Accordingly, it is an object of the present disclosure to provide an engine braking system, especially for vehicles powered by a gas turbine. The engine braking system of the present disclosure allows for control of auxiliary engine braking force; control of over-speed of the power turbine; generation of air used for quenching hot recuperator gases to assist in engine turndown; and further includes means of recovering some or all of the braking energy of the engine braking system.
As mentioned, U.S. Pat. No. 3,817,343 teaches use of a rotary compressor which can act as an auxiliary braking systems on large vehicles such as Class 8 trucks. U.S. Pat. No. 3,817,343 does not teach how to control the braking force nor does it teach how to utilize the energy dissipated by the braking compressor.
Several braking devices are disclosed. These include energy dissipative devices such as, for example, a compressor, an electrical generator, a fluid pump system and an eddy current brake or clutch. The present disclosure includes several methods of controlling the engine braking force of a braking device. Such control devices disclosed herein include (1) a continuously variable transmission (“CVT”); (2) an electrical generator and an optional thermal storage device; (3) an eddy current clutch; and (4) a fluid pump system. As can be appreciated, the various control devices may be controlled automatically by an appropriate control algorithm which is responsive to the data from various shaft rpms, free power turbine rpms and braking instructions.
One of these control methods utilizes an eddy current clutch. An innovative configuration of eddy current clutch based on a brushless alternator is disclosed.
Additional innovations disclosed herein include vehicle braking systems that utilize some or all the braking features to recoup a portion of braking energy available with either or both of a hybrid transmission and a braking compressor.
It is noted that the engine braking system of the present disclosure is a form of dynamic braking since the braking force applied to the vehicle only exists when the vehicle is in motion and when the engine braking system is caused to be connected to the vehicle's drive train.
These and other advantages will be apparent from the disclosure contained herein.
In one embodiment, a vehicle is disclosed comprising a gas turbine engine and a transmission, the gas turbine engine comprising at least one turbo-compressor spool assembly, wherein the at least one turbo-compressor spool assembly comprises a compressor in mechanical communication with a turbine, the turbine outputting a gas, and a free power turbine in fluid communication with the turbine, the free power turbine being driven by the outputted gas, a system comprising a braking device in mechanical communication with the free power turbine and the transmission to at least one of dissipate energy of the free power turbine and provide a braking force to the vehicle, wherein at least one of the following is true: (a) the braking device comprises a compressor selectively mechanically engaged and disengaged from the free power turbine and/or the transmission of the vehicle by a clutch assembly: (b) the braking device comprises a continuously variable transmission; (c) the braking device comprises an electrical generator configured to generate a selected amount of electrical energy; (d) the braking device comprises at least one of an eddy current clutch and an eddy current brake; and (e) the braking device comprises a fluid pump circuit.
In another embodiment, a method is disclosed system for a vehicle comprising a gas turbine engine and a transmission comprising at least one turbo-compressor spool assembly, the at least one turbo-compressor spool assembly comprising a compressor in mechanical communication with a turbine, the turbine outputting a gas, a free power turbine in fluid communication with the turbine, the free power turbine being driven by the outputted gas, and a braking device in mechanical communication with the free power turbine and the transmission, the method comprising performing at least one of the following steps: (a) in response to a sensed revolutions-per-minute of the free power turbine, selectively engaging and disengaging a braking device from mechanical communication with the free power turbine, the braking device retarding rotation of the free power turbine; (b) in response to a sensed braking request of the vehicle, selectively engaging and disengaging a braking device from mechanical communication with the free power turbine, the braking device providing a braking force to the vehicle; (c) varying, by an continuously variable transmission, a gear ratio continuously between first and second gear ratios, the gear ratio being for a mechanical linkage between a braking device and the clutch assembly; (d) generating, by an electrical generator, a selected amount of electrical energy to provide at least one of a selected amount of retardation force against rotation of the free power turbine and a selected amount braking force to the vehicle; (e) applying torque by at least one of an eddy current brake and eddy current clutch to provide at least one of a selected amount of retardation force against rotation of the free power turbine and a selected amount braking force to the vehicle; and (f) intermittently operating a fluid pump in mechanical communication with the free power turbine to provide at least one of a selected amount of retardation force against rotation of the free power turbine and a selected amount braking force to the vehicle.
In yet another embodiment, a vehicle is disclosed, comprising an engine, a transmission, a braking device to maintain or reduce the ground velocity of the vehicle; and at least one of the following braking device control devices: 1) a continuously variable transmission positioned mechanically with respect to the braking device, the transmission and the engine, 2) an electrical generator configured to generate a selected amount of electrical energy to provide a selected amount of retardation force against rotation of a shaft of the engine, 3) at least one of an eddy current clutch and eddy current brake positioned mechanically with respect to the braking device, the transmission and the engine, and a pump and restrictor valve in fluid communication with the braking device.
In another embodiment, a tangible or non-transient computer readable medium is disclosed comprising microprocessor-executable instructions operable to perform at least the following steps: a) sensing at least one of a revolutions per minute (“rpms”) of a free power turbine, at least one of an on and off state of a braking device clutch, at least one of an on and off state of a transmission clutch, and a braking device control setting; b) based on the sensed at least one of a revolutions per minute (“rpms”) of a free power turbine, at least one of an on and off state of a braking device clutch, at least one of an on and off state of a transmission clutch, and a braking device control setting, determining that the free power turbine requires over-speed control; c) in response to step (b), disengaging the transmission clutch and engaging the braking device clutch; d) reducing the rpms of the free power turbine by controlling an amount of energy dissipation of the braking device; e) during step (d), sensing rpms of the free power turbine and reducing the rpms of the free power turbine until the rpms of the free power turbine are reduced to less than or equal to a selected value; and f) when the rpms of the free power turbine are less than the selected value, disengaging the braking device clutch.
In another embodiment, a tangible or non-transient computer readable medium is disclosed comprising microprocessor-executable instructions operable to perform at least the following steps: a) sensing at least one of an on and off state of braking device clutch, at least one of an on and off state of a transmission clutch, a vehicle ground velocity, a transmission gear setting, and a braking device control setting; b) based on the sensed at least one of a vehicle ground velocity, at least one of an on and off state of a braking device clutch, at least one of an on and off state of a transmission clutch, and a braking device control setting, determining that engine braking is required; c) in response to step (b), engaging the braking device clutch and engaging the transmission clutch for engine braking; d) increasing a vehicle braking force opposing a direction of motion of the vehicle by controlling an amount of energy dissipation of the braking device; e) during step (d), sensing a vehicle ground velocity and applying the engine braking force until the vehicle ground velocity is less than or equal to a selected value; and f) when the vehicle ground velocity is less than or equal to the selected value, disengaging the braking device clutch.
The above-described embodiments and configurations are neither complete nor exhaustive. As will be appreciated, other embodiments of the invention are possible utilizing, alone or in combination, one or more of the features set forth above or described in detail below.
The following definitions are used herein:
The term “a” or “an” entity refers to one or more of that entity. As such, the terms “a” (or “an”), “one or more” and “at least one” can be used interchangeably herein. It is also to be noted that the terms “comprising”, “including”, and “having” can be used interchangeably.
The term automatic and variations thereof, as used herein, refers to any process or operation done without material human input when the process or operation is performed. However, a process or operation can be automatic, even though performance of the process or operation uses material or immaterial human input, if the input is received before performance of the process or operation. Human input is deemed to be material if such input influences how the process or operation will be performed. Human input that consents to the performance of the process or operation is not deemed to be “material”.
A bell housing is a term for the portion of the transmission that covers the flywheel and the clutch or torque converter of the transmission on vehicles powered by internal combustion engines. This housing is bolted to the engine block and derives its name from the bell-like shape that its internal components necessitate. The starter motor is usually mounted here, and engages with a ring gear on the flywheel. On the opposite end to the engine is usually bolted to the gearbox. The above is the normal arrangement for an in-line transmission system for a conventional rear wheel drive or all wheel drive vehicle. The arrangement for a transverse mounted engine and transmission for a front wheel drive vehicle has the gear box and differential below the engine and consequently the bell housing is a simple cover for the flywheel.
A bull gear is the larger of two gears that are in engagement. The smaller gear is usually referred to as a pinion gear.
A brushless alternator is composed of two alternators built end-to-end on one shaft. Smaller brushless alternators may look like one unit but the two parts are readily identifiable on the large versions. The larger of the two sections is the main alternator and the smaller one is the exciter. The exciter has stationary field coils and a rotating armature (power coils). The main alternator uses the opposite configuration with a rotating field and stationary armature. A bridge rectifier, called the rotating rectifier assembly, is mounted on a plate attached to the rotor. Neither brushes nor slip rings are used, which reduces the number of wearing parts. The main alternator has a rotating field as described above and a stationary armature (power generation windings). Varying the amount of current through the stationary exciter field coils varies the 3-phase output from the exciter. This output is rectified by a rotating rectifier assembly, mounted on the rotor, and the resultant DC supplies the rotating field of the main alternator and hence alternator output. The result of all this is that a small DC exciter current indirectly controls the output of the main alternator.
As used herein, a clutch is a device used to connect or disconnect flow of power from one part of a transmission from another. For example, in a typical reciprocating engine vehicle, the clutch is the mechanism in the drive train that connects the engine crankshaft to or disconnects it from the gearbox thus with the remainder of the drive train.
The term computer-readable medium as used herein refers to any tangible or non-transient storage and/or transmission medium that participate in providing instructions to a processor for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media includes, for example, NVRAM, or magnetic or optical disks. Volatile media includes dynamic memory, such as main memory. Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, or any other magnetic medium, magneto-optical medium, a CD-ROM, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, a solid state medium like a memory card, any other memory chip or cartridge, a carrier wave as described hereinafter, or any other medium from which a computer can read. A digital file attachment to e-mail or other self-contained information archive or set of archives is considered a distribution medium equivalent to a tangible or non-transient storage medium. When the computer-readable media is configured as a database, it is to be understood that the database may be any type of database, such as relational, hierarchical, object-oriented, and/or the like. Accordingly, the disclosure is considered to include a tangible or non-transient storage medium or distribution medium and prior art-recognized equivalents and successor media, in which the software implementations of the present disclosure are stored.
A Continuously Variable Transmission or CVT has a low gear ratio and a high gear ratio with infinitely many ratios in-between. The advantage of a CVT is the ability to keep the engine's RPMs in their optimum power output range for all operating conditions. A vehicle with a CVT transmission can be readily diagnosed with software. Unlike traditional automatic transmissions, continuously variable transmissions don't have a gearbox with a set number of gears, which means they don't have interlocking toothed wheels. The most common type of CVT operates on a pulley system that allows an infinite variability between highest and lowest gears with no discrete steps or shifts. Other types of CVTs include toroidal and hydrostatic.
DC bus means DC link and the terms may be used interchangeably.
The terms determine, calculate and compute and variations thereof, as used herein, are used interchangeably and include any type of methodology, process, mathematical operation or technique.
A differential connects a drive shaft to axles. While the differential may provide gear reduction, its primary purpose is to change the direction of rotation.
A drive train is the part of a vehicle or power generating machine that transmits power from the engine to the driven members, such as the wheels on a vehicle, by means of any combination of belts, fluids, gears, flywheels, electric motors, clutches, torque converters, shafts, differentials, axles and the like.
An eddy current brake is a type of electromagnetic brake in which torque is applied to a rotating shaft by means of eddy currents induced by a magnetic field set up by a conductor carrying direct current in a fixed member forming one side of the brake and inducing an opposing current in a conductor in a rotating member forming the other side of the brake.
An eddy current clutch is a type of electromagnetic clutch in which torque is transmitted by means of eddy currents induced by a magnetic field set up by a conductor carrying direct current in a member forming one side of the clutch and inducing an opposing current in a conductor in a rotating member forming the other side of the clutch.
An energy storage system refers to any apparatus that acquires, stores and distributes mechanical or electrical energy which is produced from another energy source such as a prime energy source, a regenerative braking system, a third rail and a catenary and any external source of electrical energy. Examples are a battery pack, a bank of capacitors, a pumped storage facility, a compressed air storage system, an array of a heat storage blocks, a bank of flywheels or a combination of storage systems.
An engine is a prime mover and refers to any device that uses energy to develop mechanical power, such as motion in some other machine. Examples are diesel engines, gas turbine engines, microturbines, Stirling engines and spark ignition engines.
An engine braking device as used herein is an auxiliary braking apparatus that dissipates engine power when engaged. When engaged, the engine braking device may dissipate power from the engine when the transmission clutch is not engaged and may increase vehicle braking force when the transmission clutch is engaged.
A free power turbine as used herein is a turbine which is driven by a gas flow and whose rotary power is the principal mechanical output power shaft. A free power turbine is not connected to a compressor in the gasifier section, although the free power turbine may be in the gasifier section of the gas turbine engine. A power turbine may also be connected to a compressor in the gasifier section in addition to providing rotary power to an output power shaft.
The foundation braking system of a vehicle, as used herein, comprise the drum and/or disc brakes associated with all or most of the wheels of a vehicle.
A gear box as used herein is a housing that includes at least one gear set. Typically, a gear box on a vehicle includes switchable gear sets to provide multiple gear ratios, with the ability to switch between them as speed varies. Directional (forward and reverse) control may also be provided. This switching may be done manually or automatically.
A gear set as used herein is a single ratio gear assembly.
Jake brake or Jacobs brake describes a particular brand of engine braking system. It is used generically to refer to engine brakes or compression release engine brakes in general, especially on large vehicles or heavy equipment. An engine brake is a braking system used primarily on semi-trucks or other large vehicles that modifies engine valve operation to use engine compression to slow the vehicle. They are also known as compression release engine brakes.
A mechanical-to-electrical energy conversion device refers an apparatus that converts mechanical energy to electrical energy or electrical energy to mechanical energy. Examples include but are not limited to a synchronous alternator such as a wound rotor alternator or a permanent magnet machine, an asynchronous alternator such as an induction alternator, a DC generator, and a switched reluctance generator. A traction motor is a mechanical-to-electrical energy conversion device used primarily for propulsion.
The term module as used herein refers to any known or later developed hardware, software, firmware, artificial intelligence, fuzzy logic, or combination of hardware and software that is capable of performing the functionality associated with that element. Also, while the disclosure is presented in terms of exemplary embodiments, it should be appreciated that individual aspects of the disclosure can be separately claimed
A permanent magnet motor is a synchronous rotating electric machine where the stator is a multi-phase stator like that of an induction motor and the rotor has surface-mounted permanent magnets. In this respect, the permanent magnet synchronous motor is equivalent to an induction motor where the air gap magnetic field is produced by a permanent magnet. The use of a permanent magnet to generate a substantial air gap magnetic flux makes it possible to design highly efficient motors. For a common 3-phase permanent magnet synchronous motor, a standard 3-phase power stage is used. The power stage utilizes six power transistors with independent switching. The power transistors are switched in ways to allow the motor to generate power, to be free-wheeling or to act as a generator by controlling frequency.
Over-speed control of a free power turbine means control of the rpms of a free power turbine by preventing the rpms from increasing beyond a selected value. Typically, a free power turbine will over-speed if the gas driving the turbine remains on while the load (transmission or electrical generator for example) is rapidly or abruptly turned off.
A pinion is the smaller of two gears that are in engagement. The larger gear is usually referred to as a bull gear.
A planetary gear (also known as an epicyclic gear) is a gear system consisting of one or more outer gears, or planet gears, revolving about a central, or sun gear (also known as a sun pinion). Typically, the planet gears are mounted on a planet carrier plate which itself may rotate relative to the sun gear. Planetary gearing systems also incorporate the use of an outer ring gear or orbit gear which meshes with the planet gears. In this gear system, the sun gear engages all three planet gears simultaneously. All three are attached to a planet carrier plate, and they engage the inside of the ring gear. Because there are three planet gears instead of one, the arrangement is extremely rugged. The output shaft may be attached to the ring gear, and the planet carrier may be held stationary. Alternately the output shaft may be attached to the planet carrier and the ring gear may be held stationary. Planetary gear sets can produce different gear ratios depending on which gear is used as the input, which gear is used as the output and which gear is held stationary. For instance, if the input is the sun gear the ring gear is held stationary and the output shaft is attached to the planet carrier, a particular gear ratio is obtained. In this case, the planet carrier and planets orbit the sun gear, so instead of the sun gear having to rotate six times for the planet carrier to rotate once, it has to spin seven times. This is because the planet carrier circles the sun gear once in the same direction as it was spinning, subtracting one revolution from the sun gear. So in this case, a 7:1 reduction is obtained. If the sun gear is held stationary and the output is from the planet carrier and the input is to the ring gear, a 1.17:1 gear reduction would be obtained.
A prime power source refers to any device that uses energy to develop mechanical or electrical power, such as motion in some other machine. Examples are diesel engines, gas turbine engines, microturbines, Stirling engines, spark ignition engines and fuel cells.
A power control apparatus refers to an electrical apparatus that regulates, modulates or modifies AC or DC electrical power. Examples are an inverter, a chopper circuit, a boost circuit, a buck circuit or a buck/boost circuit.
Power density as used herein is power per unit volume (watts per cubic meter).
A recuperator is a heat exchanger that transfers heat through a network of tubes, a network of ducts or walls of a matrix wherein the flow on the hot side of the heat exchanger is typically exhaust gas and the flow on cold side of the heat exchanger is typically gas (for example, air or a fuel-air mixture) entering the combustion chamber.
Regenerative braking is the same as dynamic braking except the electrical energy generated is recaptured and stored in an energy storage system for future use.
Specific power as used herein is power per unit mass (watts per kilogram).
Spool means a group of turbo machinery components on a common shaft.
A thermal energy storage module is a device that includes either a metallic heat storage element or a ceramic heat storage element with embedded electrically conductive wires. A thermal energy storage module is similar to a heat storage block but is typically smaller in size and energy storage capacity.
As used herein, a transmission is the part of a vehicle or power generating machine that transmits power from the output shaft of an engine to a drive shaft by means of any combination of belts, fluids, gears, flywheels, electric generators, clutches, torque converters and the like. A transmission may be a manual transmission or an automatic transmission. A transmission may be an all-mechanical apparatus or an apparatus with both mechanical and electrical components. The latter may also be called a hybrid transmission. In British usage, the term transmission typically refers to the whole drive train, including gearbox, clutch, drive shaft, differential and axles. In American usage for reciprocating engines, the transmission is often taken to be the gearbox between the clutch assembly in the bell housing and the drive shaft. The more general definition is used herein (power transmission apparatuses from the output shaft of an engine to a drive shaft) unless specifically defined otherwise.
A traction motor is a motor used primarily for propulsion such as commonly used in a locomotive. Examples are an AC or DC induction motor, a permanent magnet motor and a switched reluctance motor.
A turbine is any machine in which mechanical work is extracted from a moving fluid by expanding the fluid from a higher pressure to a lower pressure.
Turbine Inlet Temperature (TIT) as used herein refers to the gas temperature at the outlet of the combustor which is closely connected to the inlet of the high pressure turbine and these are generally taken to be the same temperature.
A turbo-compressor spool assembly as used herein refers to an assembly typically comprised of an outer case, a radial compressor, a radial turbine wherein the radial compressor and radial turbine are attached to a common shaft. The assembly also includes inlet ducting for the compressor, a compressor rotor, a diffuser for the compressor outlet, a volute for incoming flow to the turbine, a turbine rotor and an outlet diffuser for the turbine. The shaft connecting the compressor and turbine includes a bearing system.
Any reference to a braking compressor is assumed to include other dissipating apparatuses such as electric motors or other mechanical, fluid, magnetic, electrical and/or electromagnetic devices that consume energy.
The phrases “at least one”, “one or more”, and “and/or” are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B and C”, “at least one of A, B, or C”, “one or more of A, B, and C”, “one or more of A, B, or C” and “A, B, and/or C” means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together.
The preceding is a simplified summary of the disclosure to provide an understanding of some aspects of the disclosure. This summary is neither an extensive nor exhaustive overview of the disclosure and its various aspects, embodiments, and/or configurations. It is intended neither to identify key or critical elements of the disclosure nor to delineate the scope of the disclosure but to present selected concepts of the disclosure in a simplified form as an introduction to the more detailed description presented below. As will be appreciated, other aspects, embodiments, and/or configurations of the disclosure are possible utilizing, alone or in combination, one or more of the features set forth above or described in detail below.
The present disclosure may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the disclosure. In the drawings, like reference numerals refer to like or analogous components throughout the several views
a and 5b illustrate an example, in end view, of how a braking compressor can be geared.
a and 15b illustrate how a planetary gear system can be used for control of a braking compressor.
a and 20b are flow charts for free power turbine over-speed control.
a and 21b are flow charts for engine braking control.
A preferred engine type is a high efficiency gas turbine engine because it typically has lower NOx emissions, is more fuel flexible, fuel tolerant and has lower maintenance costs. For example, an intercooled recuperated gas turbine engine in the 10 kW to 750 kW range is available with thermal efficiencies above 40%. A schematic of an intercooled recuperated gas turbine engine is shown in
Variations of this engine architecture may include a reheater and/or thermal energy storage devices such as described, for example, in U.S. patent application Ser. No. 13/175,564, entitled “Improved Multi-Spool Intercooled Recuperated Gas Turbine” and U.S. patent application Ser. No. 12/777,916, entitled “Gas Turbine Energy Storage and Conversion System”, both of which are incorporated herein by reference.
U.S. Pat. No. 3,817,343 entitled “Installation for Brake of Motor Vehicles Which Are
Driven from a Gas Turbine” teaches a rotary compressor which acts as a dissipating apparatus that can convert shaft power into an air discharge by converting mechanical energy into kinetic and heat energy of a gas, namely air. This apparatus can have utility for braking systems on vehicles, especially large vehicles such as Class 8 trucks. The dissipating compressor disclosed in U.S. Pat. No. 3,817,343 does not teach how to control the braking force nor does it teach how to utilize the energy dissipated by the braking compressor.
Braking Compressor Locations
In
In this disclosure, a braking compressor is often used to illustrate a braking device that can dissipate energy either from an over-speeding free turbine or to provide the effect of engine braking. As can be appreciated, other dissipating apparatuses can be used to dissipate energy either from an over-speeding free turbine or to provide the effect of engine braking. These include electric generators, pump systems, eddy current brakes and clutches or other mechanical, fluid, magnetic, electrical and/or electromagnetic devices that consume energy.
The method and apparatus of the present disclosure can be adapted to either a vehicle powered by a gas turbine engine, by a reciprocating piston engine or indeed any engine. If applied to an engine running in the rpm range of 10,000 rpm or less, increasing gears will normally be required to engage a braking compressor in order for the braking power to be developed by an auxiliary compressor which, for a reasonable size, will be more compact and efficient at higher rpms, typically in the range of about 40,000 rpm to about 150,000 rpm.
An innovation of the present disclosure is the use of one or more control devices and methods to control the amount of energy dissipated by a braking compressor or other energy dissipating braking device. As can be appreciated, it may be desirable to dissipate large or small amounts of energy depending on the speed of the vehicle and the desired braking force. Hard braking at high speeds while going down hill can require large amounts of braking energy to be dissipated by an engine braking system in addition to that dissipated by the foundation braking system. Light braking at low speeds can be provided by the foundation braking system or by engine braking. The latter may be preferred since it may save undue wear and tear on the foundation braking system.
Another advantage of these control methods is that they may be used to route some of the engine braking energy to energy storage devices rather than simply dissipating this energy.
Such control devices disclosed herein include (1) a continuously variable transmission (“CVT”); (2) an electrical generator and an optional thermal storage device; (3) an eddy current clutch; and (4) a fluid pump system. The control devices can be operated automatically by a computer to provide the desired amount of braking force, for example, in response to the vehicle operator depressing a brake petal. In the case of the electrical generator or fluid pump system, these may be used both to dissipate braking energy as well as control the amounts and rate of braking energy dissipation.
Additional innovations disclosed herein include vehicle braking systems that utilize some or all the braking features to recoup a portion of braking energy available with either or both of a hybrid transmission and an energy dissipating braking apparatus.
In the present disclosure relating to a braking compressor, attention will be focused on the design of subsonic compressors. The braking compressor of the present disclosure can be a single centrifugal compressor, a two-stage centrifugal compressor, or a centrifugal and axial compressor combination. As an example, consider a vehicle with a 375 kW engine. In order to provide significant engine braking, a braking compressor would have to dissipate power in the range of about 150 kW to about 400 kW. To achieve this range of power dissipation in a compact apparatus, a compressor system capable of a pressure ratio in the range of about 6:1 to about 12:1 would normally be required.
In the following, the present disclosure is illustrated for a braking compressor. As can be appreciated, the same gearing and control methods can be applied to other energy dissipating devices such, as for example, an electrical generator or a fluid pump.
In normal driving mode, clutch assembly 51 is engaged so that power from free power turbine 8 is transmitted to wheels 55 by the drive train. Clutch assembly 51 may be disengaged when the engine is idling or when the engine is turned off In normal driving mode, clutch assembly 11 is usually disengaged. If free power turbine 8 is sensed to be over-speeding, then clutch assembly 11 may be engaged to control free power turbine over-speeding by extracting energy. Over-speeding can occur when the load on the free power turbine is abruptly decreased or removed.
In braking mode, clutch assembly 51 may be engaged or disengaged. In braking mode, when clutch assembly 51 is disengaged, clutch assembly 11 may be engaged to prevent free power turbine from over-speeding which can occur when the its load is abruptly removed. In braking mode, when clutch assembly 51 is engaged, clutch assembly 11 may be engaged to transmit braking energy back through the drive train to the braking compressor, thereby providing engine braking in the same way that a Jacobs brake provides additional braking for a reciprocating engine.
It was stated previously that clutch assembly 11 may be optional. With clutch assembly 11 disengaged, there is no parasitic load on the free power turbine when braking compressor 12 is not required. It is possible to eliminate clutch assembly 11 and use the outlet nozzle of the braking compressor to control braking. When not required, the outlet nozzle can be opened fully so that there is substantially no load and therefore substantially no energy extracted by the braking compressor. The rotor or rotors of the braking compressor apparatus can be allowed to rotate with substantially no pressure differential until braking is required and this will result in a small parasitic load on the free power turbine. For engine braking or control of free power turbine over-speed, the outlet nozzle on the braking compressor can be closed to extract energy at a selected rate with or without clutch assembly 11 as part of the system. Eliminating clutch assembly 11 would result in a small parasitic load to the vehicles engine. Thus, if overall engine and transmission efficiency are to be optimized, then retaining clutch assembly 11 would be preferable, especially if the vehicle is a long haul vehicle.
As can be appreciated, a braking compressor can also be used in conjunction with a hybrid transmission or an all electric transmission. A hybrid transmission is considered to be a transmission that can be operated as an electrical transmission or a mechanical transmission, depending on vehicle speed. For example, the free power turbine can drive an electrical generator and the electrical generator can drive a traction motor. At higher speeds, the electrical generator and traction motor can be locked up so that the transmission becomes a purely mechanical transmission. For any type of transmission, free power turbine 8 can be connected to a pinion and bull gear arrangement such as pinions 43, 44 and bull gear 41 to utilize a braking compressor for engine braking and free power turbine over-speed control.
As can be appreciated, the amount of braking force supplied by either or both of an inlet and outlet vanes of the braking compressor may be controlled automatically by an appropriate control algorithm which is responsive to the data from various shaft rpms, free power turbine rpms and brake pedal force.
As will be described in FIGS. 7,9,12 and 16,
If a braking compressor is used, the output air from the braking compressor can be discharged to the atmosphere, or it can be used to charge a pneumatic storage tank, or it can be used for quenching hot recuperator gases to assist in engine turndown. In the latter case, as the vehicle is braking, the cool output air from the braking compressor can be injected into the exhaust flow upstream of the entrance to the hot side of the recuperator (see
In normal driving mode, clutch assembly 51 is engaged so that power from free power turbine 8 is transmitted to wheels 55 by the drive train. Clutch assembly 51 may be disengaged when the engine is idling or when the engine is turned off. In normal driving mode, clutch assembly 11 is usually disengaged. If free power turbine 8 is sensed to be over-speeding, then clutch assembly 11 may be engaged to control free power turbine over-speeding by extracting energy. Over-speeding can occur when the load on the free power turbine is abruptly decreased or removed. The CVT may be controlled to provide a light to heavy braking action by continuously varying the CVT gear ratio as described below.
In braking mode, clutch assembly 51 may be engaged or disengaged. In braking mode, when clutch assembly 51 is disengaged, clutch assembly 11 may be engaged to prevent free power turbine from over-speeding which can occur when the load is abruptly removed. In braking mode, when clutch assembly 51 is engaged, clutch assembly 11 may be engaged to transmit braking energy back through the drive train to the braking compressor via CVT 15, thereby providing a continuously variable engine braking in the same way that a Jacobs brake provides such braking for a reciprocating engine. The increasing gearbox may be optional and is typically used to provide higher compressor rpms and additional braking energy at low speeds.
Consider the schematic of
A CVT has a low gear ratio and a high gear ratio with infinitely many ratios in-between. For example, the lowest gear ratio may be 0.2:1 and the highest about 1.2:1. Thus the total range of gear ratios is about 6:1 from lowest to highest.
Consider a large vehicle at a speed of about 70 mph. The wheel axles 54 would rotate at 588 rpms for a 40-inch wheel diameter. With a differential gear ratio of 3, the main drive shaft 52 would rotate at 1,765 rpms. In high gear (1:1), shaft 64 would rotate at 12,353 rpms and shaft 62 at 86,471 rpms. If CVT 15 is in its lowest gear setting (0.2:1), then shaft 67 rotates at 17,394 rpms. If gear box 16 is set at 2:1, then the braking compressor would rotate at 34,588 rpms which would be considered light braking.
Now consider the same vehicle at a speed of about 10 mph. The wheel axles 54 would rotate at 84 rpms. The main drive shaft 52 would rotate at 252 rpms. In low gear (4:1), shaft 64 would rotate at 7,059 rpms and shaft 62 at 49,412 rpms. If CVT 15 is in its highest gear setting (1.2:1), then shaft 67 rotates at 59,294 rpms. If gear box 16 is set at 2:1, then the braking compressor would rotate at 118,589 rpms which would be considered heavy braking.
As can be appreciated, the gear settings may be controlled automatically by an appropriate control algorithm which is responsive to the data from various shaft rpms, free power turbine rpms and brake pedal force.
Control Using a Electrical Generator and Thermal Energy Storage Module
In this example, the discharge air from braking compressor 12 is used to dissipate heat stored in TES unit 72. As can be appreciated, the electrical energy from generator 19 may be dissipated by other means such as, for example, a dynamic braking grid located elsewhere on the vehicle and whose energy can be dissipated by air flow past the vehicle.
In the configuration of
In the example of
In normal driving mode, clutch assembly 51 is engaged so that power from free power turbine 8 is transmitted to wheels 55 by the drive train. Clutch assembly 51 may be disengaged when the engine is idling or when the engine is turned off In normal driving mode, clutch assembly 11 is usually disengaged. If free power turbine 8 is sensed to be over-speeding, then clutch assembly 11 may be engaged to control free power turbine over-speeding by extracting energy. Over-speeding can occur when the load on the free power turbine is abruptly decreased or removed. The high speed generator 19 may be controlled to provide a light to heavy braking action by continuously varying the applied excitation.
In braking mode, clutch assembly 51 may be engaged or disengaged. In braking mode, when clutch assembly 51 is disengaged, clutch assembly 11 may be engaged to prevent free power turbine from over-speeding which can occur when the load is abruptly removed. In braking mode, when clutch assembly 51 is engaged, clutch assembly 11 may be engaged to transmit braking energy back through the drive train to the braking compressor via the high speed generator 19, thereby providing a continuously variable engine braking force in the same way that a Jacobs brake provides such braking for a reciprocating engine. An increasing gearbox between the high speed generator and the braking compressor may be used if the rpm capability of the high speed generator is too low.
As can be appreciated, the thermal energy storage module need not be present, especially if the electrical output of the high speed generator is used to provide auxiliary power, charge an energy storage system or if a dynamic braking grid already exists.
As can be appreciated, the amount of excitation applied to the electrical generator may be controlled automatically by an appropriate control algorithm which is responsive to the data from various shaft rpms, free power turbine rpms and brake pedal force.
As can be further appreciated, the braking compressor 12 can be eliminated and generator 19 can be used as the energy dissipation device. Control of braking power and energy would be by the amount of excitation applied to the generator. The output of the generator can be re-directed to charge a battery or to a TES device located inside the pressure boundary of the gas turbine engine or to a dynamic braking grid.
Control Using an Eddy Current Clutch Assembly
Eddy current clutches are well-known. The following is an innovative approach to an eddy current clutch based on a brushless alternator. A brushless alternator is composed of two alternators built end-to-end on one shaft.
As the DC current in exciter field coil 2 is increased, an AC current is induced in rotating exciter armature 3. This AC current is rectified in diode board 4 and causes a DC current in main field coil 5. The DC current in main field coil 5 then induces eddy currents in main armature 6. Main armature 6 may be a wound coil or it may be a solid block of conductor (for example aluminum which is an excellent conductor and is low density). The eddy currents induced in main armature 6 cause a rotational force in main armature 6 which tends rotate main armature 6 so as to reduce these eddy currents. As main armature 6 rotates, its housing 10 and hence output shaft 7 rotate with it. As the current in exciter field coil 2 is increased further, main armature 6 which is connected to housing 10 and output shaft 7 rotates faster and faster until it is rotating almost as fast as input shaft 1. Typically the output shaft can be caused to rotate within a few percent of the rotation speed of the input shaft. Thus by varying the DC control 11, the slippage between the input and output shaft can be varied between full disengagement to almost complete lock-up (1 or 2% slippage).
It is also possible to reverse the generator of
In normal driving mode, clutch assembly 51 is engaged so that power from free power turbine 8 is transmitted to wheels 55 by the drive train. Clutch assembly 51 may be disengaged when the engine is idling or when the engine is turned off. In normal driving mode, eddy current clutch assembly 11 is usually fully disengaged. If free power turbine 8 is sensed to be over-speeding, then eddy current clutch assembly 11 may be partially or fully engaged to control free power turbine over-speeding by extracting energy. Over-speeding can occur when the load on the free power turbine is abruptly decreased or removed. The eddy current clutch assembly may be controlled to provide a light to heavy braking action by continuously varying the current to the eddy current clutch assembly.
In braking mode, clutch assembly 51 may be engaged or disengaged. In braking mode, when clutch assembly 51 is disengaged, eddy current clutch assembly 11 may be engaged to prevent free power turbine from over-speeding which can occur when the load is abruptly removed. In braking mode, when clutch assembly 51 is engaged, eddy current clutch assembly 11 may be fully or partially engaged to transmit braking energy to the braking compressor, thereby providing a continuously variable engine braking in the same way that a Jacobs brake provides such braking for a reciprocating engine. The increasing gearbox may be optional and is typically used to provide higher compressor rpms and additional braking energy at low speeds, depending on the rpm range of the eddy current clutch system.
As can be appreciated, the degree of engagement of the eddy current clutch assembly may be controlled automatically by an appropriate control algorithm which is responsive to the data from various shaft rpms, free power turbine rpms and brake pedal force.
The heated oil is subsequently cooled in heat exchanger 3 and returned to oil reservoir 4. Thus by controlling the flow restriction provided by valve 2, the amount of work required by pump 1 can be controlled. The advantage of this system, in addition to providing additional engine braking power and/or controlling the rpms of the braking compressor, is that it can be formed by components already existing in the engine's oil lubrication system. For example, the heat exchanger for cooling the oil and the reservoir can be pre-existing components of an engine lubricating system.
In normal driving mode, clutch assembly 51 is engaged so that power from free power turbine 8 is transmitted to wheels 55 by the drive train. Clutch assembly 51 may be disengaged to idle the engine or when the engine is turned off. In normal driving mode, clutch assembly 11 is usually disengaged. If free power turbine 8 is sensed to be over-speeding, then clutch assembly 11 may be engaged to control free power turbine over-speeding by extracting energy. Over-speeding can occur when the load on the free power turbine is abruptly decreased or removed. The fluid pump 49 may be controlled to provide a light to heavy braking action by continuously varying the torque it applies to the outside of the ring gear of the planetary gear system.
In braking mode, clutch assembly 51 may be engaged or disengaged. In braking mode, when clutch assembly 51 is disengaged, clutch assembly 11 may be engaged to prevent free power turbine from over-speeding which can occur when the load is abruptly removed. In braking mode, when clutch assembly 51 is engaged, clutch assembly 11 may be engaged to transmit braking energy back through the drive train to the braking compressor, with control of the braking compressor rotational speed being provided by the amount of torque applied to the ring gear of the planetary gear system 48. This system thereby provides a continuously variable engine braking in the same way that a Jacobs brake provides such braking for a reciprocating engine. The drive input to the planetary gear set is determined by the desired gear ratio to match the rpm range of low speed bull gear 42 with the rpm range of the sun pinion.
Consider an example of a planetary gear set with a sun pinion having 30 teeth, four planet gears having 15 teeth each, and the ring gear having 150 teeth on its inner ring. When the ring gear is free wheeling, the sun gear rotates at 6 times the rotational speed of the planet carrier. When the ring gear is fixed and stationary, the sun gear rotates at 3 times the rotational speed of the planet carrier. Thus by controlling the torque applied to the outside of the ring gear by the fluid pump, the rotational speed of the braking compressor can be varied by a factor of 2 which means its retarding force can be varied by the square of its rotational speed or by a factor of 4.
A particular advantage of the configuration of
As can be appreciated, the degree of engagement of the fluid pump applied to the outside of the ring gear be controlled automatically by an appropriate control algorithm which is responsive to the data from various shaft rpms, free power turbine rpms and brake pedal force.
As can be further appreciated, the braking compressor 12 can be eliminated and fluid pump 49 can be used as the energy dissipation device. Control of braking power and energy would be by the restrictor valve in the fluid circuit. As noted previously, the work done by the pump and the heating of the oil are the mechanisms for energy dissipation of the pump system.
In normal driving mode, clutch assembly 43 is engaged so that power from free power turbine 8 is transmitted to the vehicles wheels by the drive train. Clutch assembly 43 may be disengaged when the engine is idling or when the engine is turned off. In normal driving mode, clutch assembly 13 is usually disengaged. If free power turbine 8 is sensed to be over-speeding, then clutch assembly 13 may be engaged to control free power turbine over-speeding by extracting energy by means of braking compressor 12. The compressed air provided by braking compressor 12 may be discarded or it may be used to pressurize air reservoir 46 which is part of a pneumatic braking system 45 for the vehicle. The capability to provide compressed air as just described is applicable to either a mechanical, hybrid or all-electrical transmission.
In braking mode, clutch assembly 43 may be engaged or disengaged. In braking mode, when clutch assembly 43 is disengaged, clutch assembly 13 may be engaged to prevent free power turbine from over-speeding which can occur when the its load is abruptly removed. In braking mode, when assemblies 43 and 13 are engaged, energy is transmitted to the braking compressor, thereby providing engine braking in the same way that a Jacobs brake provides such braking for a reciprocating engine. As can be appreciated, any of the control devices disclosed herein (continuously variable transmission; an electrical generator and a thermal storage device; an eddy current clutch assembly; a fluid pump system; or any combination of these) may be included with the braking compressor for control purposes. If a hybrid or electrical transmission is used, then electrical energy generated by braking may be used to charge a battery or battery pack 12; heat a thermal storage element 13; operate pneumatic pump 47; and/or operate a control motor 10 on the high pressure spool (comprised of compressor 3 and turbine 6) or low the pressure spool (comprised of compressor 1 and turbine 7). Such a thermal energy storage device is disclosed in U.S. patent application Ser. No. 12/777, 916 entitled “Gas Turbine Energy Storage and Conversion System”. Such a turbine spool control motor is disclosed in U.S. patent application Ser. No. 13/175,564 entitled “Improved Multi-spool Intercooled Recuperated Gas Turbine” and is incorporated herein by reference.
In normal driving mode, clutch assembly 43 is engaged so that power from free power turbine 8 is transmitted to the vehicles wheels by the drive train. Clutch assembly 43 may be disengaged when the engine is idling or when the engine is turned off. In normal driving mode, clutch assembly 13 is usually disengaged. If free power turbine 8 is sensed to be over-speeding, then clutch assembly 13 may be engaged to control free power turbine over-speeding by extracting energy by means of braking compressor 12. The compressed air provided by braking compressor 12 may be discarded or it may be used to pressurize air reservoir 46 which is part of a pneumatic braking system 45 for the vehicle. The capability to provide compressed air as just described is applicable to either a mechanical, hybrid or all-electrical transmission.
In braking mode, clutch assembly 43 may be engaged or disengaged. In braking mode, when clutch assembly 43 is disengaged, clutch assembly 13 may be engaged to prevent free power turbine from over-speeding which can occur when the load is abruptly removed. In braking mode, when clutch assemblies 43 and 13 are engaged, energy is transmitted to the braking compressor, thereby providing engine braking in the same way that a Jacobs brake provides such braking for a reciprocating engine. This configuration shows a control system described previously in
In normal driving mode, clutch assembly 43 is engaged so that power from free power turbine 8 is transmitted to the vehicles wheels by the drive train. Clutch assembly 43 may be disengaged when the engine is idling or when the engine is turned off In normal driving mode, eddy current clutch assembly 25 is usually disengaged. If free power turbine 8 is sensed to be over-speeding, then eddy current clutch assembly 25 may be engaged to control free power turbine over-speeding by extracting energy by means of braking compressor 12. The compressed air provided by braking compressor 12 may be discarded or it may be used to pressurize air reservoir 46 which is part of a pneumatic braking system 45 for the vehicle. The capability to provide compressed air as just described is applicable to either a mechanical, hybrid or all-electrical transmission.
In braking mode, clutch assembly 43 may be engaged or disengaged. In braking mode, when clutch assembly 43 is disengaged, eddy current clutch assembly 25 may be engaged to prevent free power turbine from over-speeding which can occur when the its load is abruptly removed. In braking mode, when clutch assemblies 43 and 25 are engaged, energy is transmitted to the braking compressor, thereby providing engine braking in the same way that a Jacobs brake provides such braking for a reciprocating engine. This configuration shows a control system described previously in
In the braking systems of
a and 20b is a flow chart for free power turbine over-speed control. Over-speed control can be implemented by an on-board computer that automatically interrogates the appropriate sensors, such as for example, free turbine rpms, the status or on/off state of the engine braking clutch and the transmission clutch, and control means for the braking device. In step 2001, the free power turbine control routine is initiated. In step 2002, the rpms of the free power are determined. In step 2003, if the rpms of the free power are not excessive, then the free power turbine control routine is terminated in step 2099. In step 2003, if the rpms of the free power are determined to be excessive, then the procedure moves to step 2004. If it is determined in step 2004 that the engine braking clutch is not engaged, then the engine braking clutch is engaged in step 2005 and the procedure moves to step 2006. If it is determined in step 2004 that the engine braking clutch is engaged, then the procedure moves directly to step 2006. If it is determined in step 2006 that the transmission clutch is engaged, then the transmission clutch is disengaged in step 2007 and the procedure moves to step 2008. The transmission clutch is disengaged since the rpms of the free power turbine would otherwise be controlled by the speed of the vehicle if the transmission clutch is engaged. The only effective way to reduce over-speed of the free power turbine is to disengage the transmission clutch so that the braking device can reduce the rpms of the free power turbine without have to slow down the entire vehicle.
In step 2008, the amount of engine braking to reduce the rpms of the free power turbine to acceptable levels is determined. In step 2009, the amount of engine braking force to reduce the rpms of the free power turbine to acceptable levels is applied by controlling the amount of engine braking force applied by the engine braking device. In step 2010, if the rpms of the free power turbine are no longer excessive, then the braking clutch is disengaged in step 2011 and the free power turbine control routine is terminated in step 2099. In step 2010, if the rpms of the free power are still determined to be excessive, then the procedure moves to back to step 2008 where the amount of engine braking to reduce the rpms of the free power turbine to acceptable levels is again determined.
a and 21b is a flow chart for engine braking control. Engine braking control can be implemented by an on-board computer that automatically interrogates the appropriate sensors, such as for example, braking requests and free turbine rpms, the status of the engine braking clutch and the transmission clutch, and control means for the braking device. In step 2101, the engine braking control routine is initiated. In step 2102, any engine braking request is determined, for example, by sensing the motion of a brake pedal or by a command to implement engine braking. If there is no engine braking request or an engine braking is over ridden (for example by a GPS monitor sensing a restricted area for engine braking), the vehicle braking procedure is terminated in step 2109. If a valid engine braking is request is determined in step 2103 then the procedure moves to step 2104. If it is determined in step 2104 that the transmission clutch is not engaged, then the transmission clutch is engaged in step 22105 and the procedure moves to step 2106 where the engine braking clutch is engaged. If it is determined in step 2104 that the transmission clutch is engaged, then the procedure moves directly to step 2106 where the engine braking clutch is engaged. In step 2107, the amount of engine braking is determined. In step 2108, the selected amount of engine braking is applied. In step 2109, if it is determined that engine braking is no longer required, then the braking clutch is disengaged in step 2110 and the engine braking routine is terminated in step 2199. In step 2109, if it is determined that engine braking is still required, then the procedure moves to back to step 2107 where the amount of engine braking is again determined.
The exemplary systems and methods of this disclosure have been described in relation to preferred aspects, embodiments, and configurations. Modifications and alterations will occur to others upon a reading and understanding of the preceding detailed description. It is intended that the disclosure be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof. To avoid unnecessarily obscuring the present disclosure, the preceding description omits a number of known structures and devices. This omission is not to be construed as a limitation of the scopes of the claims. Specific details are set forth to provide an understanding of the present disclosure. It should however be appreciated that the present disclosure may be practiced in a variety of ways beyond the specific detail set forth herein.
Furthermore, while the exemplary aspects, embodiments, and/or configurations illustrated herein show the various components of the system collocated, certain components of the system can be located remotely, at distant portions of a distributed network, such as a LAN and/or the Internet, or within a dedicated system. Thus, it should be appreciated, that the components of the system can be combined in to one or more devices or collocated.
Also, while the flowcharts have been discussed and illustrated in relation to a particular sequence of events, it should be appreciated that changes, additions, and omissions to this sequence can occur without materially affecting the operation of the disclosed embodiments, configuration, and aspects.
A number of variations and modifications of the disclosures can be used. As will be appreciated, it would be possible to provide for some features of the disclosures without providing others.
The present disclosure, in various embodiments, includes components, methods, processes, systems and/or apparatus substantially as depicted and described herein, including various embodiments, sub-combinations, and subsets thereof. Those of skill in the art will understand how to make and use the embodiments, aspects and configurations after understanding the present disclosure. The present disclosure, in various embodiments, includes providing devices and processes in the absence of items not depicted and/or described herein or in various embodiments hereof, including in the absence of such items as may have been used in previous devices or processes, for example for improving performance, achieving ease and\or reducing cost of implementation.
The foregoing discussion of the disclosure has been presented for purposes of illustration and description. The foregoing is not intended to limit the disclosure to the form or forms disclosed herein. In the foregoing Detailed Description for example, various features of the disclosure are grouped together in one or more embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed disclosure requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate preferred embodiment of the disclosure.
Moreover though the description of the disclosure has included description of one or more embodiments and certain variations and modifications, other variations and modifications are within the scope of the disclosure, e.g., as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative embodiments to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter
The present application claims the benefits, under 35 U.S.C. §119(e), of U.S. Provisional Application Ser. No. 61/440,746 entitled “Gas Turbine Engine Braking Method” filed on Feb. 8, 2011, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61440746 | Feb 2011 | US |
