Turbine inter-spool energy transfer system

An inter-spool energy transfer system is provided and includes a first spool, a second spool, which includes components that are rotatable at a different speed as compared to components of the first spool and an inter-spool interface system coupled to at least one of the components of the first spool and at least one of the components of the second spool. The inter-spool interface system includes a controller, which is configured to supply power to one of the first and second spools and to draw power from the other of the first and second spools.

BACKGROUND OF THE DISCLOSURE

The subject matter disclosed herein relates to an energy transfer system and, more particularly, to a turbine inter-spool energy transfer system.

For multi-spool engines, whether those engines are provided in vehicles, aircraft or ground-based systems, the engines generally include a power shaft, a compressor or “gas generator”, a combustor, a gas generator turbine, a power turbine and a compressor shaft. During operation, inlet air is compressed in the gas generator to produce compressed air. This compressed air is then mixed with fuel and combusted in the combustor to produce a working fluid. The working fluid is directed to the gas generator turbine in which the working fluid is expanded to generate power that is used to drive rotations of the compressor shaft. Such rotations drive, for example, inlet air compression operations of the gas generator. The working fluid is then transmitted to the power turbine in which the working fluid is expanded further to generate additional power that is used to drive rotations of the power shaft in order to power gearboxes, fans, or other aircraft systems.

For such engines, an operational problem exists in that it is often the case that engine power will be limited by one parameter (e.g. speed or temperature) while having margin with respect to other parameters. As such, there exists untapped potential for increasing engine power without increases to speed or temperature limits of the engine.

BRIEF DESCRIPTION OF THE DISCLOSURE

According to one aspect of the disclosure, an inter-spool energy transfer system is provided and includes a first spool, a second spool, which includes components that are rotatable at a different speed as compared to components of the first spool and an inter-spool interface system coupled to at least one of the components of the first spool and at least one of the components of the second spool. The inter-spool interface system includes a controller, which is configured to supply power to one of the first and second spools and to draw power from the other of the first and second spools.

In accordance with additional or alternative embodiments, a power connection is provided between the controller and one or more of the aircraft electrical systems, hydraulic systems, compressed air systems, and mechanical systems.

In accordance with additional or alternative embodiments, the first spool is a core spool including a gas generator, a gas generator turbine and a compressor shaft and the second spool is a power spool including a power shaft and a power turbine.

According to one aspect of the disclosure, an inter-spool energy transfer system is provided for use in a vehicle including an electrical system. The system includes a first spool, a second spool, which includes components that are rotatable at a lesser speed as compared to components of the first spool and an inter-spool interface system coupled to at least one of the components of the first spool and at least one of the components of the second spool. The inter-spool interface system includes a controller configured to supply power to the electrical system by transferring torque from the first spool to the second spool and draw power from the electrical system by transferring torque from the second spool to the first spool.

In accordance with additional or alternative embodiments, a power connection is provided between the controller and the electrical system.

In accordance with additional or alternative embodiments, the first spool is a core spool including a gas generator, a gas generator turbine and a compressor shaft and the second spool is a power spool including a power shaft and a power turbine.

In accordance with additional or alternative embodiments, the inter-spool interface system is coupled to the power shaft and the gas generator.

In accordance with additional or alternative embodiments, the inter-spool interface system includes a planetary gear system.

In accordance with additional or alternative embodiments, the inter-spool interface system includes an electrical interface.

In accordance with additional or alternative embodiments, the inter-spool interface system includes a torque converter and the torque converter includes one or more of a mechanical, fluidic, fluid-mechanical, electro-mechanical, pneumatic and electronic torque converter.

In accordance with additional or alternative embodiments, the inter-spool energy transfer system is coupled to the power spool.

In accordance with additional or alternative embodiments, energy is transferred from the first spool to the second spool in order to increase available power without increasing first spool speed and energy is transferred from the second spool to the first spool in order to increase available power without increasing engine temperature.

In accordance with additional or alternative embodiments, energy is transferred from the first spool to the second spool or from the second spool to the first spool in order to control engine efficiency.

In accordance with additional or alternative embodiments, energy is transferred from the first spool to the second spool or from the second spool to the first spool in order to increase engine power response rate.

In accordance with additional or alternative embodiments, a transfer of power is initiated and initially maintained in anticipation of a transient power demand with power transfer being subsequently reduced to increase a power response rate for power demands.

DETAILED DESCRIPTION OF THE DISCLOSURE

As will be described below, an inter-spool energy transfer system is provided for use with multi-spool engines to transfer energy between turbine stages in order to optimize overall engine performance (i.e., power, thrust, operating characteristics, etc.). The inter-spool energy transfer system may be usable for optimization of turbine performance for fixed wing (fan, prop, jet), rotary wing, ground vehicles (tanks, trains), electric power stations and/or any other end use which uses (primarily) multi-spool turbines. The inter-spool energy transfer system can make use of core load to slow down a free turbine (i.e., a gas generator turbine spool in a turbo-shaft engine) when the free turbine reaches its speed limit. This allows additional fuel to be added to the turbine until the engine produces more power and simultaneously operates at speed and temperature limits.

Alternatively, when the engine reaches its temperature limit with free turbine speed margin (i.e., a gas generator speed margin), the inter-spool energy transfer system can use aircraft or engine power to spin-up the free turbine to increase mass-flow and increase pressure/thermodynamic efficiency. This allows more fuel to be added and thus more power to be extracted when the engine would otherwise be operating on a T45 limit. Meanwhile, when the engine is operating in a low power mode, power may be transferred from the power spool to the free turbine to increase the free turbine speed such that the engine power response to a quick increase in power may be improved. Additionally, energy may be transferred between the power spool and the free turbine in order to control the engine to be either more or less efficient. Also, the inter-spool energy transfer system may be used to inject energy into the engine from aircraft electric, hydraulic or compressed air power systems or to extract energy out of the engine to power these aircraft systems.

With reference toFIG. 1, an engine of a vehicle such as an aircraft or a helicopter is provided. The engine includes a power shaft1, a compressor or “gas generator”2, a combustor3, a gas generator turbine4, a power turbine5and a compressor shaft6. During operation of the engine, inlet air is compressed in the gas generator2to produce compressed air. This compressed air is then mixed with fuel and combusted in the combustor3to produce a working fluid. The working fluid is directed to the gas generator turbine4in which the working fluid is expanded to generate power that is used to drive rotations of the compressor shaft6. Such rotations drive, for example, inlet air compression operations of the gas generator2. The working fluid is then transmitted to the power turbine5in which the working fluid is expanded further to generate additional power that is used to drive rotations of the power shaft1.

Although the engine described above is similar to a turbo-shaft engine, the description provided herein is not limited to any particular engine configuration. Indeed, the description provided herein may be applicable to any multi-spool turbine engine such as, but is not limited to, turbo-shaft engines, turbo-jets, turbo-fans, turbo-prop aircraft, turbo-shaft helicopters, 3+ spool turbines and ground-based power turbines.

With reference toFIGS. 2-4, it will be understood that the gas generator2, the gas generator turbine4and the compressor shaft6combine to form a core spool7(seeFIG. 2) and that the power shaft1and the power turbine5combine to form a power spool8(seeFIG. 3). As shown inFIG. 4, an inter-spool interface system9may be provided with a first end coupled to the power shaft1and a second end opposite the first end coupled to a compressor or front portion of the gas generator2.

With reference toFIG. 5and, in accordance with embodiments, the inter-spool interface system9may be provided as a planetary gear system that connects the power shaft1to the compressor or front portion of the gas generator2. That is, as shown inFIG. 5, the inter-spool interface system9may include a ring gear10, a planet gear11, a planet carrier12and a sun gear13. The ring gear10is coupled to the power shaft1and the sun gear13is coupled to the compressor or front portion of the gas generator2. The planet gear11is integrally connected to and supported by the planet carrier12and is interposed between the ring gear10and the sun gear13. The inter-spool interface system9further includes a planet carrier drive system14, a controller20, a power line21and power and control connection22. The controller20is electrically powered by way of and accepts commands from the power and control connection22and is capable of providing power to or extracting power from planet carrier drive system14by way of power line21.

In the embodiment ofFIG. 5, the planetary gear system can be used to couple the core spool7and the power spool8together so as to provide power to or draw power from the carrier drive system14and to thereby transfer power between the core spool7and the power spool8as an electronic torque converter. The power input/draw is controlled by the controller20(which is most likely an electronic controller but could be generalized to controlling electric, mechanical, pneumatic or fluidic power supply to the planet carrier12in order to affect torque transfer) and the power and control connection22connects to the aircraft systems. The power and control functions of the power and control connection22may be formed of multiple lines but is depicted inFIG. 5as one line for ease of illustration.

When the controller20is supplying power to the power and control connection22, the supply of power can be used to power electrical systems of the aircraft and thereby reduce power draws by other generators as applicable as in a case of a hybrid engine powered helicopter, for example. The supply of power can also be used to charge batteries or be wasted. In any case, when the controller20is supplying power to the power and control connection22, since the gas generator2usually spins faster than the power shaft1, the inter-spool interface system9will be transferring torque from the gas generator2to the power shaft1while at the same time supplying electrical power out on the power and control connection22. The controller20can thus make use of core spool7loading to slow down the gas generator2and to thereby allow additional fuel to be added to the gas generator2so that the gas generator2can generate more power until the engine reaches a state where it is simultaneously operating at speed and temperature limits.

Conversely, when the controller20is drawing power from the power and control connection22, the supply of power may be drawn from generators elsewhere in the aircraft power system and, in any case, since the gas generator2is usually spinning faster than the power shaft1, the inter-spool interface system9will be transferring torque from the power shaft1to the gas generator2. In this case, electrical power can be used by the controller20to spin-up the gas generator2to increase mass-flow and to increase pressure/thermodynamic efficiency and to thereby allow more power to be extracted from the power spool8while adjusting fuel to maintain the engine at the temperature limit.

Similarly, when the engine is operating in a low power state, the controller20may command an increase gas generator2operating speed to maintain a higher speed than thermodynamic equilibrium would otherwise dictate as discussed above. With the core spool7operating at a higher speed, the core would not need to accelerate as far in order to enable the engine to produce the desired power and the power required to maintain the gas generator2operating speed at a higher than thermodynamic equilibrium may be progressively shed as the gas generator2accelerates. The combination of these two actions will result in a faster net power delivery response than would otherwise be possible to be provided by the engine without the inter-spool interface system9. Additionally, when a transient drop in engine power is commanded, the controller20may maintain the engine gas generator2speed at a high speed such that subsequent demands for increased power may be accomplished at a fast rate. Also, when in a low power state (i.e., not on an engine limit), the controller20may control transfer of power between the core spool7and the power spool8in order to control and either increase or decrease the efficiency of the engine.

With reference toFIG. 6and, in accordance with alternative embodiments, the inter-spool interface system9may be provided as an electrical interface. Here, the controller20drives rotations of the power shaft1by transmitting electrical power to a first motor-generator61by way of first power line23. Conversely, the controller20receives from the first motor-generator61, by way of the first power line23, electrical power generated by the first motor-generator61from rotations of the power shaft1(i.e., the power spool8). In addition, the controller20drives operations of the gas generator2by transmitting electrical power to a second motor-generator62by way of second power line24. Conversely, the controller20receives from the second motor-generator62, by way of the second power line24, electrical power generated by the second motor-generator62from operations of the gas generator2(i.e., the core spool7). As such, the controller20may control the flow of electrical power between the first and second motor-generators61and62and thus transfer energy between the core spool7and power spool8.

In accordance with further embodiments, the controller20may be connected to aircraft systems via the power and control connection22where the controller20may extract a net electrical power from one or more of the first and second power lines23and24to power aircraft systems via the power and control connection22. Additionally, the controller20may receive power via the power and control connection22in order to drive one or more of first and second motor-generators61and62.

With reference toFIG. 7and, in accordance with alternative embodiments, the inter-spool interface system9may be provided as a generalized torque converter system. Here, the controller20controls torque converter70to drive rotations of the power shaft1by transmitting power to a power shaft accessory gearbox71by way of first power line23and torque-converter70. Conversely, the torque converter70may receive power from the power shaft accessory gearbox71by way of the first power line23. In addition, the controller20controls torque converter70to drive operations of the gas generator2by transmitting power to a core spool accessory gearbox72by way of second power line24and the torque converter70. Conversely, the torque converter70may receive power from the core spool accessory gearbox72by way of the second power line24. As such, the controller20may command the torque converter70to transfer torque and power between the core spool7and the power spool8.

In accordance with further embodiments, the controller20may be connected to aircraft systems via the power and control connection22where the controller20may extract torque or power from torque converter70via one or more of the first and second power lines23and24to power aircraft systems via the power and control connection22. Additionally, the controller20may receive power via the power and control connection22in order to drive one or more of power shaft accessory gearbox71and core spool accessory gearbox72via the first and second power lines23and24and torque converter70.

With reference toFIG. 8and with continuing reference toFIG. 7, the inter-spool interface system9may be generalized such that the torque converter70interface with the power spool8and the power shaft1may connect indirectly through an aircraft drivetrain accessory gearbox81. This aircraft drivetrain accessory gearbox81may incorporate a mechanical drive system85connected to the turbine engine. In this configuration, power is transferred directly between aircraft drivetrain accessory gearbox81and core spool accessory gearbox72via torque converter70. Under certain embodiments, the first power line23may provide the power functions of the power and control line22.

With reference toFIGS. 4-8, any number of over-run clutches and clutch engagement systems and associated control systems may be utilized at the interface of the inter-spool interface system9with the core spool7and the power spool8in order to engage or disengage the inter-spool interface system9with/from the core spool7and the power spool8. These clutches have been excluded from the figures and discussion for clarity.

For brevity and clarity, the disclosure herein described an engine with two spools (i.e., a turbine engine with a core spool7and a power spool8). The core spool7and power spool8may be generalized to be a first spool and second spool of the engine. Additionally, in general, this first and second spool may represent any two selected spools for turbine engines incorporating more than two spools.