Abstract: A closed cycle Stirling cryogenic cooler, typically utilizing a noble gas (He or like) as a working fluid and containing a pneumatically driven expander interconnected with a low frequency pressure wave generator using a flexible transfer line or conduit, wherein the pressure wave generator includes a sealed gas discharge cavity containing the pressurized working fluid and a plurality of discharge electrodes which are electrically isolated, protrude through the walls of the cavity and are electrically connected to the high frequency pulse voltage supply, thus producing the glow discharge resulting in a cloud of cold plasma, making a so-called “plasmanized gas piston”.

Abstract: The present invention describes a novel integration between wind and solar thermal renewable energy technologies. An existing wind turbine consisting of a hub and blades is operated by the power generated from a waterless solar thermal system (using high pressure, high temperature air) during periods of low wind availability. The solar thermal system consist of a heliostat field, solar air receiver panels, a thermal energy storage tank and a Pelton wheel assembly system for converting thermal energy of air into kinetic energy of the power shaft of the wind turbine. The thermal energy converting system consists of a plurality of supersonic air nozzles acting as stator, producing supersonic air jets to interact with a rotating Pelton wheel. A thermal storage system provides means for energy dispatchability. The proposed integrated system is capable of generating a stable renewable energy with minimum intermittency.

Abstract: An engine supplied with compressed air includes a main drive piston (1) driving a crankshaft (5) and one active expansion chamber (13) of a variable volume allowing work to be produced and which is connected, by a passage (6), with the volume contained in the driving cylinder (2). The passage (6) includes a shutter (7) thus allowing the active expansion chamber to be isolated from or to be placed in contact with the dead volume, in such a manner that the engine works according to a four-phase thermodynamic cycle: * an isothermal expansion without work; * a transfer-slight expansion with work known as quasi-isothermal; * a polytropic expansion with work; * an exhaust at ambient pressure.

Abstract: The present disclosure details a thermoacoustic driven compressor having a pressurized housing, which contains within a thermoacoustic engine and a working gas, coupled to a positive displacement reciprocating compressor. The thermoacoustic driven compressor generates scalable compressed air from a given heat source.

Abstract: An external combustion engine provided with a pipe-shaped main container with a heating portion and a cooling portion, an output part converting displacement of the liquid part of said working fluid generated due to the change in volume of said working fluid accompanying generation and condensation of said steam to mechanical energy for output, a venturi provided at a communicating part of the main container and an auxiliary container, a communicating member forming a communicating passage bypassing the venturi and communicating the main container and the auxiliary container, and a shutting means for closing the communicating passage at the time of normal operation and opening the communicating passage at the time of startup, wherein at the time of startup, the pressure loss at the communicating passage becomes smaller than a saturated steam pressure at the temperature of the heating portion.

Abstract: An actuator device including: a case housing an expandable material, a moving part that can move in translation as a result of the expansion and/or contraction of the expandable material, and a heater to heat the expandable material. The device also includes: a position sensor which measures the current position of the aforementioned moving part; and a positioner to position the moving part, including a controller acting on the above-mentioned heater according to the current measured position.

Abstract: Systems, methods, and apparatus relating to the use of Stirling engine technology to convert heat, such as from solar radiation, to mechanical work or electricity. Apparatus, systems, components, and methods relating to energy converting apparatus are described herein. In one aspect, the invention relates to the field alignment of panels and the assembly of a concentrator. In another aspect, a passive balancer is used in combination with a ring frame and other moving masses to reduce engine forces and vibration on the structure of the energy converting apparatus while maintaining properly constrained alignment of various suspended masses. In yet another aspect, the invention relates to various over-insolation control and management strategy to prevent overheating of the energy converting apparatus or components and subsystems thereof.

Abstract: An apparatus includes a substrate having a top surface, a substantially regular array of raised structures located over the top surface, and a layer located on the top surface between the structures. Distal surfaces of the structures are farther from the top surface than remaining portions of the structures. The layer is able to contract such that the distal surfaces of the structures protrude through the layer. The layer is able to swell such that the distal surfaces of the structures are closer to the top surface of the substrate than one surface of the layer.

Abstract: A compact cryocooler includes a gas compression piston (304) supported for reciprocal linear translation along a first longitudinal axis (308) and a gas displacing piston (362) supported for reciprocal linear translation along a second longitudinal axis (366). The first longitudinal axis (308) and second longitudinal axis (366) are substantially orthogonal. A rotary motor (302) rotates a rotor (324) and associated motor shaft (320) about a motor rotation axis (328) disposed substantially parallel with the second longitudinal axis (366). Motor shaft (320) first and second mounting features (336, 340) traverse first and second eccentric paths around the motor rotation axis. A first drive coupling couples the first mounting feature (336) with the gas compression piston (304) and delivers a reciprocal linear translation along the first longitudinal axis (308) thereto.

Abstract: An energy recovery system for a pipe manufacturing process is shown. A compression or injection molding operation is used to form a sealing gasket which is used in the subsequent pipe manufacturing operation. A Stirling engine cycle is used to recover heat during the gasket manufacture. The Stirling engine is driven by waste heat from the mold members or other associated parts of the injection or compression molding apparatus. The recovered waste heat is used to subsequently heat the female pipe end which is being belled in the pipe manufacturing process.

Abstract: A heat engine enclosed in a housing has two chambers maintained at different temperatures. The first chamber (“hot chamber”) receives heat energy from an external power source. The second chamber (“cold chamber”) is connected to the hot chamber by two conduits, such that a fluid (e.g., air, water, or any other gas or liquid) filling the two chambers can circulate between the two chambers. The expansion of the fluid in the hot chamber and the compression of the fluid in the cold chamber drive a turbine to provide a power output. The fluid may be pressurized to enhance efficiency. In one embodiment, the turbine propels an axle in a rotational motion to transmit the power output of the heat engine to an electrical generator outside of the heat engine's housing. In one embodiment, the turbine includes a first set of blades and a second set of blades located in the hot chamber and the cold chamber, respectively.

Abstract: Disclosed is a heat engine following an intermediate form between an ideal Carnot engine and a Stirling engine and having high thermal efficiency. The heat engine includes a cylinder in which operating gas is filled; a high temperature heater which heats a front end part of the cylinder and thermally expands the operating gas; a low temperature cooler which cools a rear end part of the cylinder and contracts the operating gas; and a piston which is accommodated inside the cylinder to rectilinearly reciprocate as the operating gas is thermally expanded and contracted, and includes a heat opening to make the operating gas directly contact the high temperature heater or the low temperature cooler.

Abstract: A solar energy-based water heating and power generating module includes a factory-fabricated compound module panel usable as a cover panel for building, car or ship and capable of absorbing solar energy for heating water flowing in a water chamber and a circulation pipe, and a power generator formed of a field magnet set, an oscillator and a coil and actuated by a temperature difference energy to generate heat.

Abstract: A power generation system includes a heat source, a primary heat engine and a secondary heat engine. The primary heat engine has a hot heat exchanger thermally coupled to the heat source and a cold heat exchanger. The secondary heat engine has a hot heat exchanger thermally coupled to the cold heat exchanger of the primary heat engine and a cold heat exchanger configured to reject waste heat.

Abstract: An actuator includes features that reduce the energy drawn from the engine by reducing and/or eliminating the flow requirement during normal operating conditions. A normally closed cooling orifice opens responsive to an elevated temperature to allow cooling fluid flow. Once the temperature returns to normal ranges, the thermally expanding material retracts and the valve returns to a closed position to stop cooling flow.

Abstract: An energy harvesting system comprises a first region having a first temperature and a second region. A conduit is located at least partially within the first region. A heat engine configured for converting thermal energy to mechanical energy includes a shape memory alloy forming at least one generally continuous loop. The shape memory alloy is disposed in heat exchange contact with the first region and the second region. The shape memory alloy is driven to rotate around at least a portion of the conduit by the response of the shape memory alloy to the temperature difference between the first region and the second region. At least one pulley is driven by the rotation of the shape memory alloy, and the at least one pulley is operatively connected to a component to thereby drive the component.

Abstract: A high efficiency generator is provided using a Stirling engine to amplify an acoustic wave by heating the gas in the engine in a forward mode. The engine is coupled to an alternator to convert heat input to the engine into electricity. A plurality of the engines and respective alternators can be coupled to operate in a timed sequence to produce multi-phase electricity without the need for conversion. The engine system may be operated in a reverse mode as a refrigerator/heat pump.

Abstract: The invention relates to fluidic oscillators including compressed gas driven pumps and liquid piston and thermoacoustic heat engines and heat pumps in which the intention is to generate large amplitude oscillations by eliminating the dependence of the oscillations on inertia. According to the principle embodiment represented by circuit 200 pressure or temperature variations 27? drive pressure variations in vessel 11? causing a flow of further working fluid between vessel 11? and load 12? wherein useful work is consumed. Said flow varies out of phase with said pressure variations in vessel 11? by a first phase angle determined by inter alia the dissipative load 12? and the capacity of vessel 11?.

Abstract: An uplock assembly for retaining and releasing landing gear systems, said uplock assembly comprising: a thermal actuator comprising: a chamber configured to contain expansible material therein; a heating mechanism coupled to said chamber for heating said expansible material and causing volumetric expansion thereof; a piston slidably coupled to said chamber and adapted to extend in response to said volumetric expansion; and an uplock release mechanism releasably engaged by said piston when extended such that said engaged uplock release mechanism causes the release of said landing gear.

Abstract: A 4-cycle Stirling engine is for carrying out thermal power processes or heat power and cold and heat pumping processes with two double piston units which move with a phase offset to each other.

Abstract: When an actuator is driven, a stationary element continuously generates a pressing force for spreading in a radial direction such that the stationary element is relatively retracted into movable elements positioned at both ends of the stationary element. As a result, a distance between the movable elements adjacent to each other is reduced, and a contracting operation is performed. When the actuator is not driven, only a relatively low frictional force is generated between the moving elements and the stationary element. Hence, the movable elements and the stationary element can change relative position by small external force.

Abstract: A thermo-electro-acoustic engine comprises a sealed body having a regenerator, hot and cold heat exchangers, an acoustic source, and an acoustic energy converter. An acoustic pressure wave is generated in a gas in the region of the regenerator. The converter converts a portion of the acoustic pressure into electrical energy. A portion of the electrical energy is used to drive the acoustic source. The acoustic source is controllably driven to produce acoustic energy which constructively adds to that of the acoustic pressure wave in the region of the regenerator. The remaining electrical energy produced by the converter is used external to the engine, such as to drive a load or for storage. The resonant frequency of the engine and the frequency of the energy output can be controlled electronically or electromechanically, and is not limited solely by the physical structure of the engine body and its elements.

Abstract: The present invention provides an electricity generation device using hot gas engine. The device contains a closed container filled with high-pressure gas. The container has an outlet which is connected to a pneumatic or hydraulic cylinder. Hot and cold fluids are sprayed alternatively and repeatedly into the closed container to heat up or cool down the high-pressure gas. As the high-pressure gas expands or contracts, a piston rod of the cylinder is pushed and pulled back and forth so as to produce electricity continuously.

Abstract: An apparatus for locomotion includes an elongate body member defining a longitudinal axis and having oppositely disposed first and second body ends separated by a body lumen. A power source is operative to selectively provide motive power to the apparatus by changing a lateral cross-sectional area of the body member in at least one actuation location to produce at least one peristaltic wave propagated through the body member substantially along the longitudinal axis. The peristaltic wave is a substantially smooth wave. The peristaltic wave causes the body member to interact with an ambient environment and provide longitudinally oriented locomotion to the apparatus. A method for locomotion is also described.

Abstract: A cryogenic self powered system includes a cooled chamber having a hot face and a cold face; a power generator coupled to the hot face and the cold face to generate electricity therefrom; and a working fluid coupled to the cooled chamber and to the power generator.

Abstract: A solar thermal powered aircraft powered by heat energy from the sun. A heat engine, such as a Stirling engine, is carried by the aircraft body for producing power for a propulsion mechanism, such as a propeller. The heat engine has a thermal battery in thermal contact with it so that heat is supplied from the thermal battery. A solar concentrator, such as reflective parabolic trough, is movably connected to an optically transparent section of the aircraft body for receiving and concentrating solar energy from within the aircraft. Concentrated solar energy is collected by a heat collection and transport conduit, and heat transported to the thermal battery. A solar tracker includes a heliostat for determining optimal alignment with the sun, and a drive motor actuating the solar concentrator into optimal alignment with the sun based on a determination by the heliostat.

Abstract: A concentrating solar receiver that maximizes the amount of solar energy available for conversion to electricity that utilizes a primary reflector, a secondary reflector and a fresnel lens to both reflect and refract solar rays to a thermal cycle engine receiver which converts solar energy to mechanical energy which is in turn converted into electrical energy using an electric generator. The configuration creates focal points that protect the thermal cycle engine receiver from high temperatures and provides uniform density of solar energy within the thermal cycle engine receiver. The solar receiver is moved in response to a sun tracking sensor using a vertical and a horizontal drive motor. The thermal cycle engine and the electric generator, representing the majority of mass, are centered on the vertical support and are low to the ground.

Abstract: Systems and devices for storing mechanical energy in a spring motor or the like are described. In one implementation, an energy storage device includes an elastic rope, a spool and a control mechanism. The elastic rope is reversibly deformable from a relaxed state to a stretched state for storing mechanical energy. The spool is coupled to the elastic rope, and is configured to maintain the elastic rope in the stretched state while the elastic rope is wound around the spool. The control mechanism is coupled to the spool and is configured to allow the spool to rotate in response to the elastic rope relaxing from the stretched state to the relaxed state for retrieval of stored mechanical energy. In some implementations, the elastic rope may be formed from an elastomer wrapped with a fiber made from carbon nanotubes or other synthetic strengthening material.

Abstract: An external combustion engine 10 is disclosed, wherein a container 11 sealed with a working medium adapted to flow in a liquid state includes a heating unit 13 for generating a vapor of the working medium 12 by heating part of the working medium, and a cooling unit 14 for liquefying by cooling the vapor. The volume of the working medium 12 is changed by the generation and liquefaction of the vapor, and the displacement of the liquid portion of the working medium 12 caused by the volume change of the working medium 12 is converted into and output as mechanical energy. The heating unit 13 is structured so that inner members 51a, 53a arranged on the inside and outer members 51b, 53b arranged on the outside are bonded to each other. The outer members 51b, 53b are made of a second material higher in heat resistance than the first material of the inner members 51a, 53a. Further, the thickness of the inner members 51a, 53a is not smaller than the thermal penetration depth ? of the first material.

Abstract: A method of generating motion from a cool region that is proximal to a warm region, the cool region and the warm region defining a temperature range. The method uses an article of phase change material having a warm-to-cold phase transition and a cold-to-warm phase transition, both within the temperature range. This article is exposed to the cool region, thereby causing the phase change material to change size. When the warm-to-cold phase transition is substantially complete, this is detected. In response to this detection the article is exposed to the warm region, thereby causing the phase change material to change size. When this transition is substantially complete, the cycle is restarted with exposure to the cool region.

Abstract: A machine such as an external combustion engine in an electrical power and heat cogeneration unit comprises multiple cylinders, each driving an independent load or being independently driven, and a balance shaft comprising one or more off-centre balancing mass(es) to counteract rocking motion created by the piston motion and thereby assist in dynamically balancing the machine.

Abstract: An intermediate duct (108) is connected between first and second positive displacement machines (104, 106). An inlet duct (107) is connected to the first positive displacement machine (104). An outlet duct (109) is connected to the second positive displacement machine (106). A heater (102) raises the temperature and pressure of a gaseous working fluid in the intermediate duct (108). There is a kinematic connection (111) between the first and second positive displacement machines (104, 106) and the arrangement is such that, in operation, the first positive displacement machine (104) causes the working fluid to flow through the intermediate duct (108) to the second positive displacement machine (106), the heated working fluid drives the second positive displacement machine (106), and the second positive displacement machine (106) drives the first positive displacement machine (104) via the kinematic connection (111). The positive displacement machines include at least one orbiting piston.

Abstract: An external combustion engine includes: a main container sealed with a working fluid in a liquid state adapted to flow; a heater for heating a portion of the working fluid in the main container and generating the vapor of the working fluid; a cooler for cooling and liquefying the vapor; an output unit for outputting by converting the displacement of the liquid portion of the working fluid generated by the volume change of the working fluid due to the generation and liquefaction of the vapor into mechanical energy; and an auxiliary container communicating with the main container. The heater, the cooler and the output unit are arranged in order, in the direction of displacement of the working fluid. The working fluid is sealed in the auxiliary container which communicates with the portion of the main container nearer the output unit than the cooler.

Abstract: An external combustion engine comprises a container (11) with a working liquid (12) sealed therein in a state adapted to flow, a heater (13) for heating and vaporizing the working liquid (12) in the container (11), and a cooler (14) for cooling and liquefying the vapor of the working liquid (12) heated and vaporized by the heater (13). The displacement of the working liquid (12) caused by the vapor volume change is output as mechanical energy by being converted into the mechanical energy. A pressure regulating liquid (18) is sealed in a pressure regulating container (16) communicating with the container (11). A pressure regulating unit (19) regulates the internal pressure (Pt) of the pressure regulating container (16).

Abstract: An external combustion engine provided with a plurality of evaporators and stabilized in output and efficiency, that is, an engine provided with at least one main container, a plurality of evaporators heating the working medium to evaporate, condensers cooling the vapor of the working medium evaporated at the evaporators to make it condense, an output part communicated with the other end of the main container and converting displacement of a liquid part of the working medium occurring due to fluctuations in volume of the working medium accompanying evaporation and condensation of the working medium to mechanical energy for output, a single main container pressure adjusting means adjusting an internal pressure of the main container, and controlling means for controlling the main container pressure adjusting means based on a lowest temperature in the temperatures of the plurality of evaporators constituting a minimum evaporator temperature.

Abstract: An expansion circuit comprising a working medium and a decompression unit for converting thermal energy of a combustion engine into electrical energy by expanding the working medium, wherein the decompression unit is part of an air-conditioning circuit as a compressor for compressing a working medium. The decompression unit runs in the same direction during expansion of a working medium and during compression of a working medium.

Abstract: A fluid delivery device is provided. The device comprises an internal container, an external container and a first delivery pipe. The internal container has a first space for containing a fluid to be delivered. The external container substantially surrounds the internal container to form a substantially sealed second space between the internal container and the external container, wherein the second space is for an assistant liquid. The assistant liquid is heated to raise the pressure in the second space, and then, the internal container is pressed, thereby driving the fluid out along the first delivery pipe.

Abstract: A piston apparatus which configures an air bearing by introducing a compressed working media into an inside of a piston, and ejecting the working media from plural holes arranged on a circumferential portion of the piston into a clearance between the piston and the cylinder, which prevents a back-flow of the working media in the piston to a working space, and which readily secures reliability and longevity is provided.

Abstract: A thermodynamic machine including a closed circuit for the circulation of a refrigerant fluid, a heat exchanger, a cold inlet, and at the exchanger output, a hot outlet, at least one first variable-volume enclosure acting on a mobile member communicating its movement to an output system, and a cooler. According to the invention, the machine further includes at least one variable-volume enclosure controlled by the output system by being interposed between the cold inlet of the circuit and the cooler outlet, with such a chamber providing, for an operating cycle of the enclosure, reinjection of liquid into the exchanger to maintain the pressure at the hot outlet of the circuit at a substantially constant value.

Abstract: An annular burner assembly having an annular burner mesh. An annular gas/air supply duct supplies a combustible gas/air mixture to the burner mesh in a substantially axial direction. A flow modifier is provided in the vicinity of the burner and has a plurality of fins each extending in a substantially radial plane to define a plurality of passages arranged circumferentially around the supply duct to substantially laminarise the gas/air mixture. The fins provide a thermal link from the burner to a location radially away from the burner. The burner assembly is particularly suited to a Stirling engine.

Abstract: In an engine driven by liquefied gas, such as liquefied nitrogen or air, inlet means (31, 33) admits drive fluid to an expansion chamber defined by the volume between two relatively movable members (1, 28) guided for movement in a repetitive cycle by guide means (38, 40). The inlet means also allows a heat exchange liquid to be admitted to the chamber in which the liquid is in intimate contact with the drive fluid and gives up heat energy to the expanding drive fluid. The cooled heat-exchange liquid is withdrawn from the chamber, heated and re-circulated to the chamber. Part of said cycle includes a time period during which there is substantially no relative movement between the members (1, 28) and during which the chamber volume is maintained at or close to its minimum volume, the heat-exchange liquid and drive fluid being admitted to the chamber during said time period.

Abstract: A heat exchanger includes: a cylindrical member made of metal as an outer shell body; a corrugated fin that is made of metal and that is attached to the cylindrical member as a heat exchanging member; and a coating layer formed on at least one of a surface of the cylindrical member and a surface of the corrugated fin. The corrugated fin is pressure-contacted to the cylindrical member. The heat exchanger can be provided, for example, to a heat absorbing portion or a heat dissipating portion of a Stirling engine.

Abstract: An object of the present invention is to provide a thermo-element having a simple structure, an improved durability and a good response characteristic, by improving heat conduction of wax serving as a thermally expandable component and by improving a diaphragm. The wax serving as the thermally expandable component is blended with small pieces of metal, such as metal powder and metal foil, and a low-melting point alloy having a melting point equal to or higher than a melting point of the wax, which are melted and mixed together in the wax, so as to improve the heat conduction and thus response characteristic of the wax. Further, a thick sealing member comprises a piston insertion bore formed in a central portion of the thick sealing member, a thick portion having a high thickness between the piston insertion bore and a sealing portion arranged in an outer peripheral region of the thick sealing member, the thick portion being easily deformable.

Abstract: A power cycle generator includes a central processor, a liquid storage unit, a heating unit, and a condensing unit. The central processor receives a signal and activates a compressor which forces out liquid substance in the liquid storage unit. The liquid substance is ejected out through an atomizer as an atomized object which is filled into the heating unit having a heat exchanger. Simultaneously, the atomized object is evaporated through a solar cell into high pressure air flow blowing toward a gas turbine which transmits proper torque through a gear box to a generator for producing electricity. The high pressure air flow is converted into a liquid-gas mixture through the condensing unit, and is compressed and transmitted to the liquid storage unit through the compressor, thus forming a continuous cycle between a liquid state and a gaseous state, and acquiring free electricity and heat through solar energy.

Abstract: A dielectrophoretic heat engine with temperature-dependent dielectric matter and energy conversion method exploiting the thermodielectrophoretic effect for effectively and efficiently converting thermal energy into work or other useful forms at any physical size or scale.

Abstract: In the pressure oscillation generator 1, self-excited vibration is generated in a work transfer tube 30 by heating a heat input section 22 and also a resonator 50 is resonated, and when a work is inputted into a heat exchanger 20, the work is amplified by the heat exchanger 20, and is transferred to the heat transfer tube 30 and is then outputted to an output section 40. Because of the configuration, an outputted work can be amplified to a work larger than the inputted work, so that, by using a portion of the outputted work as energy for driving the cylinder 10, the pressure oscillation generator 1 can continuously be driven only by heating and without using electric energy generated by a large scale solar system or the like, which enables substantial size reduction of the pressure oscillation generator 1.

Abstract: A power generation system including a housing defining a cavity and having an inlet for receiving a fluid that is used to cool and pressurize the cavity and an outlet for removing the fluid from the cavity. The system also may include a rotor having a first end positioned within the cavity of the housing and a second end, a plurality of bearings, positioned to contact the rotor, for providing radial support to the rotor, and a turbine connected to the second end of the rotor. Further, the system may include a heat sink positioned within the cavity and between the housing and the rotor, an electronic component attached to the heat sink, and a reaction chamber for receiving the fluid from the outlet and for producing a substance that is directed to the turbine causing it to rotate.

Abstract: A two-cycle hot-gas engine comprising an expansion piston in a heatable cylinder member and a compression piston in a coolable cylinder member. The expansion piston and the compression piston are disposed along a common axis.

Abstract: A flow rate control valve includes a second substrate having a flexible thin film and interposed between a first substrate having a heating mechanism and a third substrate having a sealing section. The first substrate and the second substrate close an internal space formed adjacent to the heating mechanism and filled with an expandable material. The sealing section and the flexible thin film function together as a valve. The heating mechanism heats and expands the expandable material whose pressure is detected by pressure-detecting sensors. The detected pressure value is fed back to a control mechanism of the heating mechanism for opening/closing a fluid flow passage and controlling the valve opening degree.

Abstract: Stirling engine which may be used as a heat pump, which consists of a hot half and a cold half. Both halves are connected by two lines which constitute a counterflow heat exahnger or in which a counterflow heat exchanger is mounted. Moreover, a mutual shaft, to which in the hot half a large and a small piston are mounted and to which in the cold half a large and a small piston are mounted, connects both parts. For every up or down going movement of the shaft, a complete Stirling cycle is performed. If desired, the shaft may be replaced by a hydraulic interconnection.