Abstract: A turbomachine engine and gear assembly is provided. The engine includes a first power input component rotatable along a first direction relative to the engine centerline axis, a second power input component rotatable along a second direction relative to the engine centerline axis, a power output component rotatable relative to the engine centerline axis, a static component fixed relative to a circumferential direction relative to a gear assembly centerline axis, and a gear assembly. The gear assembly includes a first rotatable gear operably coupled to the first power input component at a first interface. The first rotatable gear is operably coupled to the static component at a static component interface. The static component interface is configured to react against the first rotatable gear to rotate the first rotatable gear relative to the gear assembly centerline axis. The power output component is operably coupled to the first rotatable gear.

Abstract: A bottoming cycle power system includes a turbine-generator. The turbine-generator includes a turbo-expander and turbo-compressor disposed on a turbo-crankshaft. The turbo-expander is operable to rotate the turbo-crankshaft as a flow of exhaust gas from a combustion process passes through the turbo-expander. The turbo-compressor is operable to compress the flow of exhaust gas after the exhaust gas passes through the turbo-expander. An exhaust gas heat exchanger includes first and second flow paths operable to exchange heat therebetween. The first flow path is operable to receive the flow of exhaust gas from the turbo-expander prior to the exhaust gas being compressed by the turbo-compressor. The second flow path is operable to receive the flow of exhaust gas from the turbo-compressor after the exhaust gas has been compressed by the turbo-compressor.

Abstract: A method of and apparatus for desalinating sea water using geothermal energy. A low voltage (such as less than 0.9V) is applied to a hydrogen generating catalysts to generate hydrogen and oxygen, wherein geothermal heat is used as a heat source. The hydrogen and oxygen are used to drive a gas turbine to generate electricity. The oxygen and hydrogen are transported away and combusted to generate heat and pure water, as such salt are separated from the pure water.

Abstract: Systems and methods are disclosed for controlling surge margin in the compressor section of a gas turbine engine. Bypass ports on a first compressor section and second compressor section lead to a bypass conduit. An auxiliary turbine and discharge conduit are positioned in the bypass conduit. Fluid flow from the compressor sections into the bypass conduit via the bypass ports is controlled by bypass control valves.

Abstract: A lower pressure tap is connected to a first heat exchanger to be cooled by cooling air, and then to a selection valve. The selection valve selectively delivers the lower pressure tap air to a boost compressor. The lower pressure tap air downstream of the boost compressor is connected to cool the at least one turbine. The selection valve also selectively delivers a portion of the lower pressure tap air across a first cooling turbine, and to a line associated with an air delivery system for a cabin on an associated aircraft. A portion of the air downstream of the first cooling turbine is connected to a second cooling turbine, and air downstream of the second cooling turbine is connected for use in a cold loop A method of operating an air supply system is also disclosed.

Abstract: Various systems and methods are provided for a turbocharger system. In one example, system for use with a power generator having a rotary machine including a combustor comprises: a heat exchanger positioned to receive exhaust gases from the combustor; and a turbocharger system, comprising: a low pressure turbocharger including a low pressure turbine adapted to receive gas flow from the heat exchanger and a low pressure compressor adapted to supply compressed air to the heat exchanger; a high pressure turbocharger including a high pressure turbine adapted to receive gas flow from the heat exchanger and a high pressure compressor adapted to receive gas flow from the low pressure compressor and supply compressed air to the rotary machine; and a second combustor adapted to inject exhaust gases into a flow path arranged between the heat exchanger and an inlet to each of the high pressure turbine and the low pressure turbine.

Abstract: The present disclosure provides a turbine engine, comprising a core turbine engine comprising a turbine and a compressor adapted to be driven by the turbine via a rotor; as accessory gearbox connected with the rotor; and a flexible shaft having a first end connected with the accessory gearbox and a second end extending toward outside for being coupled to an external power source.

Abstract: Bleed air systems for use with aircraft and related methods are disclosed. An example apparatus includes a compressor having a compressor inlet, a compressor outlet, and a first drive shaft. The compressor outlet is to be fluidly coupled to a system of an aircraft that receives pressurized air, and the compressor inlet is to receive bleed air from a low-pressure compressor of an engine of the aircraft. The example apparatus includes a gearbox operatively coupled to the first drive shaft to drive the compressor. The gearbox is to be operatively coupled to and powered by a second drive shaft extending from the engine. The example apparatus also includes a clutch disposed between the first drive shaft and the gearbox to selectively disconnect the first drive shaft from the gearbox.

Abstract: A compressed air energy storage power generation device equipped with: a compressor mechanically connected to a motor; a first pressure storage tank storing compressed air from the compressor; an expansion device driven by compressed air from the tank; a generator mechanically connected to the expansion device; a first heat exchanger that exchanges heat between a heat medium and the compressed air supplied from the compressor to the tank; a second heat exchanger that exchanges heat between the heat medium and the compressed air supplied from the tank to the expansion device; a pressure sensor that detects the state of charge (SOC) of the tank; SOC adjustment units that adjusts the SOC; and a control device. The control device controls the SOC adjustment units such that the detected SOC is within an optimal SOC range while satisfying the requested power.

Abstract: A compressed air energy storage power generation device equipped with: a compressor mechanically connected to a motor; a first pressure storage tank storing compressed air from the compressor; an expansion device driven by compressed air from the tank; a generator mechanically connected to the expansion device; a first heat exchanger that exchanges heat between a heat medium and the compressed air supplied from the compressor to the tank; a second heat exchanger that exchanges heat between the heat medium and the compressed air supplied from the tank to the expansion device; a pressure sensor that detects the state of charge (SOC) of the tank; SOC adjustment units that adjusts the SOC; and a control device. The control device controls the SOC adjustment units such that the detected SOC is within an optimal SOC range while satisfying the requested power.

Abstract: A gas turbine engine comprises a main compressor section having a high pressure compressor with a downstream most end, and more upstream locations. A turbine section has a high pressure turbine. A first tap taps air from at least one of the more upstream locations in the main compressor section, passing the tapped air through a first heat exchanger and then to a cooling compressor. A second tap taps air from a location closer to the downstream most end than the location of the first tap, and the first and second taps mix together and are delivered into the high pressure turbine. The cooling compressor is positioned downstream of the first heat exchanger, and upstream of a location where air from the first and second taps mix together.

Abstract: Systems and methods for cooling a core flow-path of a compressor section of a gas turbine engine are provided. In various embodiments, a cooling system for a gas turbine engine may comprise a valve system located radially outward from an engine case, the valve system being coupled between an air duct and the engine case, the valve system having an actuation device configured to at least one of open or close a valve in response to a command from an electronic engine controller, wherein cooling air from the air duct can pass through the valve system and enter the engine case into a high pressure compressor plenum when the valve system is in an open position.

Abstract: A method and system providing an airflow to a wing anti-ice system includes receiving an airflow from an outside air supply, compressing the airflow via an electric compressor, controlling a temperature of the airflow from the electric air compressor via a heat exchanger in fluid communication with the electric compressor and the wing anti-ice system, and providing the airflow to the wing anti-ice system via the heat exchanger.

Abstract: A control device for fuel cell includes, comprising a compressor configured to supply cathode gas to a fuel cell, a driving device including at least two compressor driving sources including a drive motor and a driving body using a power source other than the drive motor, the driving device configured to drive the compressor by the driving sources; and a control unit. The control unit configured to control a state of the power source on the basis of an operating state of the fuel cell, and the control unit selects the driving source to be used out of the compressor driving sources on the basis of the state of the power source.

Abstract: Bleed air systems for use with aircraft and related methods are disclosed. An example apparatus includes a compressor having a compressor inlet and a compressor outlet. The compressor is to be driven by a drive shaft extending from an engine of an aircraft. The example apparatus also includes a first passageway to fluidly couple a first low-pressure bleed air port from the engine to the compressor inlet and a second passageway to fluidly couple the compressor outlet to a system of the aircraft.

Abstract: A clearance control apparatus providing compressed cooling air to a turbine casing in a gas turbine, the apparatus including: a cooling gas passage extending through an inner annular shell of the turbine casing; a cooling gas conduit connected to a compressor of the gas turbine and to the turbine casing, wherein the cooling gas conduit receives compressed air from the compressor and delivers the compressed air to the turbine casing, and wherein the cooling gas conduit is in fluid communication with the cooling gas passage, and a heat exchanger connected to the cooling gas conduit and to a fuel conduit delivering fuel to a combustor of the gas turbine, wherein the heat exchanger transfers heat from the cooling gas to the fuel.

Abstract: A cryogenic fuel system for an aircraft having a turbine engine with a compressor section and a combustion chamber, including a tank for storing cryogenic fuel, a supply line operably coupling the tank to the combustion chamber and a pump coupling the tank to the supply line to pump the cryogenic fuel at high pressure through the supply line where the pump is operably coupled to the compressor such that operation of the turbine engine drives the pump and a method for delivering fuel in a fuel system to a turbine engine.

Abstract: A tip turbine engine includes an axial compressor having a plurality of airfoils compressing core airflow. The airfoils include bleed air openings on their suction side surfaces. The bleed air openings prevent separation of the compressed airflow, which permits each airfoil stage to perform increased compression without separation of the airflow. As a result, the number of stages can be reduced, thereby shortening the overall length of the turbine engine.

Abstract: A power generation system includes: a first gas turbine system including a first turbine component, a first integral compressor and a first combustor to which air from the first integral compressor and fuel are supplied, the first combustor arranged to supply hot combustion gases to the first turbine component, and the first integral compressor having a flow capacity greater than an intake capacity of the first combustor and/or the first turbine component, creating an excess air flow. A second gas turbine system may include similar components to the first except but without excess capacity in its compressor. A control valve system controls flow of the excess air flow from the first gas turbine system to the second gas turbine system. A cooling fluid injector may be coupled to the excess air flow path for injecting a cooling fluid such as water or steam into the excess air flow.

Abstract: A power electronics cooling system includes a ram air fan with one or more blades and a ram air fan motor connected via an output shaft. The ram air fan draws in air and passes it across a heat exchanger to cool one or more cooling liquids. One or more pumps pressurize and pump the cooling liquids to various electronic components, including one or more motor controllers. The pumps may be mechanically or electrically coupled to the output shaft of the ram air fan, such that the motor of the ram air fan provides energy to the pumps.

Abstract: An integrated power and thermal management system for a turbine-powered aircraft is provided. The system may comprise a power turbine, compressor, first cooling turbine, second cooling turbine, and electrical motor-generator disposed on a primary shaft. The compressor may be disposed on the primary shaft to motivate a system airflow and operably joined to the power turbine. The first cooling turbine may be rotatably disposed on the primary shaft in selective fluid communication with the compressor. The second cooling turbine may be rotatably disposed on the primary shaft in selective fluid communication with the first cooling turbine.

Abstract: A method for estimating a speed of an induction motor includes applying a voltage to the induction motor and measuring a current of the induction motor. A current fast fourier transform (FFT) of the current is then determined and a slip of the induction motor is calculated based on the current FFT. A speed of the induction motor is then estimated based on the slip of the induction motor.

Abstract: The present invention is relative to a engine apparatus comprising a combustion engine, a low pressure compressor connected to a high pressure turbine. The apparatus also comprises a low pressure turbine and a high pressure compressor. The engine apparatus according to the invention comprises an electrical torque converter comprising at least an electric generator connected so as to be driven by said low pressure turbine and a first electric motor connected so as to drive said high pressure compressor. The torque converter also comprises electronic conversion means suitable to convert the electric energy produce by said electric generator and to power supply and control at least said first electric motor.

Abstract: An apparatus is provided for supplying electrical power and cooling for an aircraft. The apparatus includes a cooling turbine coupled to a shaft, a compressor coupled to the shaft, and including an input for receiving engine bleed air or ambient air, and an output for discharging compressed air, a flywheel coupled to the shaft, a power turbine coupled to the shaft, and a starter generator coupled to the shaft between the compressor and the power turbine.

Abstract: A method and architecture for recovery of energy in an aircraft, both at altitude and on the ground, and recovering thermal energy from an exhaust. An architecture for recovery of energy includes an auxiliary power unit APU including an exhaust nozzle and a gas generator including a shaft transmitting power to a load compressor. The compressor supplies compressed air via a supply duct to an ECS air conditioning system of a passenger cabin. A recovery turbocharger is connected, directly or via a transmission case, to the shaft of the APU. The turbocharger includes a recovery turbine powered by a downstream branch of a conduit mounted on a heat exchanger fitted to the nozzle. The conduit includes an upstream branch connected to channels connecting air outlets of the cabin and the compressor. A second exchanger can be mounted between the supply duct and the cabin outlet channel.

Abstract: Steam turbine system and control system therefor are provided. In one embodiment, a steam turbine system includes an auxiliary turbine in fluid communication with an IP turbine via an auxiliary turbine inlet conduit branch of an IP exhaust conduit. A heat exchanger system may remove heat from an IP exhaust steam, and may add the removed heat to water flowing through a boiler feed-water conduit to a boiler of the steam turbine system.

Abstract: A counter rotating helico-axial pump is provided, the pump comprising: (a) an inner rotor comprising a plurality of outwardly extending helico-axial impeller vanes; (b) a hollow outer rotor comprising a plurality of inwardly extending helico-axial impeller vanes; (c) a single driving device configured to drive the inner rotor or the hollow outer rotor; and (d) a force transmission coupling joining the inner rotor and the hollow outer rotor and configured to permit rotation of the inner rotor and hollow outer rotor in opposite directions; wherein at least a portion of the inner rotor is disposed within the hollow outer rotor, and wherein the inner rotor, the hollow outer rotor and the helico-axial impeller vanes define a fluid flow path, and wherein the inner rotor and hollow outer rotor are configured such that at least some of adjacent helico-axial impeller vanes are configured to rotate in opposite directions.

Abstract: An apparatus performs a power cycle involving expansion of compressed air utilizing high pressure (HP) and low pressure (LP) air turbines located upstream of a gas turbine. The power cycle involves heating of the compressed air prior to its expansion in the HP and LP air turbines. Taking into consideration fuel consumption to heat the compressed air, particular embodiments may result in a net production of electrical energy of ˜2.2-2.5× an amount of energy consumed by substantially isothermal air compression to produce the compressed air supply. Although pressure of the compressed air supply may vary over a range (e.g. as a compressed air storage unit is depleted), the gas turbine may run under almost constant conditions, facilitating its integration with the apparatus. The air turbines may operate at lower temperatures than the gas turbine, and they may include features of turbines employed to turbocharge large reciprocating engines.

Abstract: In one embodiment, a system is provided that includes a first gas turbine engine. The first gas turbine engine has a first compressor configured to intake air and to produce a first compressed air and a first combustor configured to combust a first mixture to produce a first combustion gas. The first mixture has a first fuel, at least a first portion of the first compressed air, and a second combustion gas from a second gas turbine engine. The first gas turbine engine also includes a first turbine configured to extract work from the first combustion gas.

Abstract: This is a system that stores energy by compressing atmospheric air and confining it in tanks or caverns, combining the thermodynamic cycle followed by the atmospheric air (Brayton cycle) with another thermodynamic cycle followed by an auxiliary fluid, that is confined in the same cavern within a membrane, following two sections of a Rankine cycle, one during the air compression and entry into the cavern process and the other during the air outlet and turbininig process, using heat from the exhaust gases from the turbine as a heat source for an additional Rankine cycle, and being able to use the tanks or caverns for making an extra constant volume heating of compressed air and I or of the auxiliary fluid

Abstract: The present application provides an integrated bottoming cycle system for use with a gas turbine engine. The integrated bottoming cycle system described herein may include a compressor/pump, a cooling circuit downstream of the compressor/pump, a bottoming cycle heat exchanger, a heating circuit downstream of the bottoming cycle heat exchanger, and a number of turbine components in communication with the cooling circuit and/or the heating circuit to maximize the overall plant efficiency and economics.

Abstract: A method and apparatus for generation of electric power employing fuel and air staging in which a first stage gas turbine and a second stage partial oxidation gas turbine power operated in parallel. A first portion of fuel and oxidant are provided to the first stage gas turbine which generates a first portion of electric power and a hot oxidant. A second portion of fuel and oxidant are provided to the second stage partial oxidation gas turbine which generates a second portion of electric power and a hot syngas. The hot oxidant and the hot syngas are provided to a bottoming cycle employing a fuel-fired boiler by which a third portion of electric power is generated.

Abstract: A rotor disk for a gas turbine engine is disclosed and formed to enable operation at high rotational speeds in a high temperature environment. The rotor disk is formed to include a bore, a live rim diameter and an outer diameter related to each other according to defined relationships.

Abstract: An apparatus performs a power cycle involving expansion of compressed air utilizing high pressure (HP) and low pressure (LP) air turbines located upstream of a gas turbine. The power cycle involves heating of the compressed air prior to its expansion in the HP and LP air turbines. Taking into consideration fuel consumption to heat the compressed air, particular embodiments may result in a net production of electrical energy of ˜2.2-2.5× an amount of energy consumed by substantially isothermal air compression to produce the compressed air supply. Although pressure of the compressed air supply may vary over a range (e.g. as a compressed air storage unit is depleted), the gas turbine may run under almost constant conditions, facilitating its integration with the apparatus. The air turbines may operate at lower temperatures than the gas turbine, and they may include features of turbines employed to turbocharge large reciprocating engines.

Abstract: A turbofan engine includes a fan, a compressor section, a combustor in fluid communication with the compressor section, a turbine section in fluid communication with the combustor, a shaft configured to be driven by the turbine section and coupled to the compressor section through a first torque load path, and a speed reduction mechanism configured to be driven by the shaft through a second torque load path separate from the first load path for rotating the fan.

Abstract: Systems and methods for accelerating droop response in a combined cycle power plant are provided. According to one embodiment if the disclosure, a system may include a controller and a processor communicatively coupled to the controller. The processor may be configured to receive frequency variation data associated with a frequency variation of an electrical grid, determine, based at least in part on the frequency variation data, a target operational level of the combined cycle power plant and the droop response associated with the target operational level, calculate a variable compensation value, and apply the variable compensation value to the droop response until the target operational level is reached.

Abstract: A gas turbine engine includes a shaft defining an axis of rotation. An outer turbine rotor directly drives the shaft and includes an outer set of blades. An inner turbine rotor has an inner set of blades interspersed with the outer set of blades. The inner turbine rotor is configured to rotate in an opposite direction about the axis of rotation from the outer turbine rotor. A gear system couples the inner turbine rotor to the shaft and is configured to rotate the inner set of blades at a faster speed than the outer set of blades. The gear system is mounted to a mid-turbine frame.

Abstract: A gas turbine engine includes a shaft defining an axis of rotation. An inner rotor directly drives the shaft and includes an inner set of blades. An outer rotor has an outer set of blades interspersed with the inner set of blades. The outer rotor is configured to rotate in an opposite direction about the axis of rotation from the inner rotor. A gear system is engaged to the outer rotor and is positioned upstream of the inner set of blades.

Abstract: One embodiment of the present invention is a unique gas turbine engine. Another embodiment is a unique variable cycle gas turbine engine. Another embodiment is a unique adaptive fan system for a variable cycle turbofan engine having at least one turbine. Another embodiment is a unique method for operating a variable cycle gas turbine engine. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for gas turbine engines and related systems.

Abstract: A gas turbine includes a compressor with a plurality of pressure plates, a combustor downstream from the compressor, and a turbine downstream from the combustor and axially aligned with the compressor. The combustor produces combustion gases that flow to the turbine. A first manifold connected to the combustor contains a first process gas for combustion in the combustor. A second manifold connected upstream of the turbine contains a second process gas, and a portion of the second process gas flows to the plurality of pressure plates.

Abstract: A turboprop propulsion unit includes at least one pusher propeller 5, 6 driven by an aircraft gas-turbine engine, with the aircraft gas-turbine engine being arranged in front of the pusher propeller 5, 6 in a direction of flight. A turbine outlet area 9 is arranged at the front in the direction of flight and a compressor area 14 faces towards the pusher propeller 5, 6.

Abstract: A bi-modal turbine assembly is provided for use in conjunction with a gas turbine engine. In one embodiment, the bi-modal turbine assembly includes a housing assembly having a flow passage therethrough, a turbine wheel rotatably mounted in the housing assembly and positioned so as to be driven by pressurized air flowing through the flow passage, an output shaft rotatably mounted in the housing assembly, and first and second gear trains disposed in the housing assembly. A switching device is also disposed in the housing assembly and configured to mechanically couple: (i) the first gear train between the turbine wheel and the output shaft in a first operational mode, and (ii) the second gear train between the turbine wheel and the output shaft in a second operational mode.

Abstract: A method for assembling a rotary machine includes providing at least one combustor assembly that includes at least one fuel nozzle. The method also includes coupling at least one fuel source to the at least one combustor assembly. The method further includes coupling at least one solvent-based purge system in flow communication with the at least one combustor assembly.

Abstract: A gas turbine system (1A) includes a gas turbine unit (2) and a cooling fluid generator (5). The gas turbine unit (2) includes a first compressor (21) and a first expansion turbine (23) coupled to each other by a first shaft (22), a combustor (26), and a fuel tank (30). A fuel held in the fuel tank (30) circulates through a fuel circulation passage (31). A working fluid that has a pressure increased by the first compressor (1) is extracted from the gas turbine unit (2). The cooling fluid generator (5) includes a cooler (55) for cooling, with the fuel flowing through the fuel circulation passage (31), the working fluid that has been extracted from the gas turbine unit (2), and a second expansion turbine (53) for expanding the working fluid that has flowed out of the cooler (55).

Abstract: A representative gas turbine includes: a high pressure spool; a high pressure compressor; a high pressure turbine mechanically coupled to the high pressure spool; a lower pressure spool; a lower pressure turbine mechanically coupled to the lower pressure spool; a fan having a first set of fan blades and a second set of fan blades, the second set of fan blades being located downstream of the first set of fan blades and being operative to rotate at a rotational speed corresponding to a rotational speed of the lower pressure spool; and a gear assembly mechanically coupled to the lower pressure spool and engaging the first set of fan blades such that rotation of the lower pressure spool rotates the first set of fan blades at a lower rotational speed than the rotational speed of the second set of fan blades.

Abstract: An representative gas turbine includes: a first annular gas flow path; a second annular gas flow path located radially outwardly from the first gas flow path; in series order, a multi-stage fan, radially inboard portions of a first set of high pressure compressor blades, a second set of high pressure compressor blades, a combustion section and a high pressure turbine, positioned along the first gas flow path; and in series order, the multi-stage fan and radially outboard portions of the first set of high pressure compressor blades, positioned along the second gas flow path such that the inboard portions of the first set of high pressure compressor blades, the second set of high pressure compressor blades, the combustion section and the high pressure turbine are not positioned along the second gas flow path.

Abstract: A method for providing cooling and power is provided. The method includes providing a cooling unit that includes a first turbine rotatably coupled to a generator by a first shaft and providing a power unit that includes a second turbine rotatably coupled to a compressor by a second shaft. The method further includes coupling the power unit in flow communication with the cooling unit to form a turbine assembly, wherein the first shaft and the second shaft are independently rotatable relative to one another.

Abstract: A Compressed Air Energy Storage (CAES) system includes a first combustion turbine assembly (42) having a shaft (52) coupled to a motor (54), a compressor (44) and a debladed turbine element (46). A second combustion turbine assembly (68) has a shaft (74) coupled to an electrical generator (80), a turbine (70) and a debladed compressor (72). A first interconnection (58) is from an output of the compressor (44) of the first combustion turbine assembly to an air storage (66). A second interconnection (87) is from the air storage to the turbine (70) of the second combustion turbine assembly for producing power. An expander (88) and an electrical generator (94) are provided. A third interconnection (90) is from the air storage (66) to the expander (88). A source of heat preheats compressed air in the third interconnection. A fourth interconnection (96) is from the expander to the turbine (70).

Abstract: A method of increasing output of a combined cycle power plant with supplemental duct firing from a heat recovery steam generator (HRSG) during select periods includes guiding a reheat steam flow to at least one reheat attemperator fluidly connected to the HRSG during the select period. The method further includes increasing reheat attemperation water flow through the at least one reheat attemperator, decreasing a set point temperature of the at least one reheat attemperator for the select period to a lower set point temperature, and raising power output of the combined cycle power plant during the select period.

Abstract: An ACAES system operable in a compression mode and an expansion mode of operation is disclosed and includes a compressor system configured to compress air supplied thereto and a turbine system configured to expand compressed air supplied thereto, with the compressor system including a compressor conduit and the turbine system including a turbine conduit. The ACAES system also includes a plurality of thermal energy storage (TES) units positioned on the compressor and turbine conduits and configured to remove thermal energy from compressed air passing through the compressor conduit and return thermal energy to air passing through the turbine conduit. The compressor conduit and the turbine conduit are arranged such that at least a portion of the plurality of TES units operate at a first pressure state during the compression mode of operation and at a second pressure state different from the first pressure state during the expansion mode of operation.