Abstract: A convertible gas turbine propulsion system operates in multiple output modes. The convertible gas turbine propulsion system comprises a gas generator, a first power turbine, a secondary propulsion system and an exhaust duct. The gas generator is configured to produce exhaust gas. The first power turbine is aligned with the gas generator to receive the exhaust gas. The secondary propulsion system is in series with the gas generator and the first power turbine. The exhaust duct coaxially extends from the first power turbine to the secondary propulsion system. The exhaust duct includes an exhaust port for opening the exhaust duct to ambient air pressure and permitting exhaust gas to bypass the secondary propulsion system. In various embodiments of the invention, the first power turbine is connected to a first rotary propulsion system, and the secondary propulsion system comprises a second power turbine or a nozzle.

Abstract: A pulse detonation combustor assembly contains at least one PDC tube, a mechanical air flow valve which directs an air flow into the PDC tube, where the mechanical air flow assembly changes a rate of the air flow into the PDC tube during a fill stage of the PDC tube. The assembly also contains a fuel flow control valve which directs fuel to the PDC tube and changes the rate of the fuel flow into PDC tube. By controlling the flow of the fuel and air into the PDC tube the equivalence ratio profile of the PDC tube can be tailored and controlled.

Abstract: The present invention describes a hybrid rocket motor that includes a first solid reactant and at least one thrust nozzle and at least one moveable combustion control member within the hybrid rocket motor that restricts the contact of a first fluid reactant in the combustion chamber. In this way, it is then possible to regulate the exposure of the solid reactant to the fluid reactant and thus control thrust.

Abstract: A pourable opaque centerport for solid propellant rocket motors and method for applying the same are disclosed. The pourable centerport inhibitor for solid propellant rocket motors has a curing system that includes a prepolymer and a curing agent. The prepolymer and the curing agent are combined to form a pourable polymeric binder that cures into an amorphous solid. The pourable centerport inhibitor also includes an opaque agent. The pourable centerport inhibitor may also include a plasticizer. The plasticizer, the prepolymer, and the curing agent are preferably the same type that is in the solid propellant with which it will be used in conjunction.

Abstract: Spacecraft thrusters capable of dual-mode operation, and a method of applying s propulsion to a spacecraft using a dual-mode thruster are provided. In one embodiment, the thrusters of the current invention can operate as a chemical motor to provide high thrust and low propellant exhaust velocity to achieve fast maneuverability, or as an electric propulsion thruster to provide low thrust and high exhaust velocity to perform maneuvers with a minimal amount of propellant.

Abstract: An auxiliary power unit disclosed. The auxiliary power unit includes an exhaust passage configured to direct a flow of exhaust from a primary mover, a catalyst substrate disposed within the exhaust passage, and a heater configured to heat the catalyst substrate. The auxiliary power unit also includes a cooling jacket associated with the exhaust passage. The auxiliary power unit further includes a thermo-electric device disposed between the cooling jacket and the exhaust passage. The thermo-electric device is configured to generate electrical power from a temperature gradient created by the heater and the cooling jacket when the primary mover is non-operational.

Abstract: The invention relates to a process for manufacturing a porous silicon carbide structure of the honeycomb type, said process being characterized in that it comprises the following steps: forming of a paste from a mixture of silicon carbide grains, the diameter d50 of which is between 5 ?m and 300 ?m, of an organic binder and of an inorganic pore former, in the form of particles based on silica, the overall porosity of said particles being greater than 70%; forming of a honeycomb-shaped green plastic monolith; drying of said monolith; and firing of the monolith at a temperature greater than 2100° C. The structure obtained by the process may be used as catalytic support in an exhaust line of a diesel or petrol engine or as particulate filter in an exhaust line of a diesel engine.

Abstract: In a metering apparatus for the metered introduction of a first medium into an exhaust gas system of an internal combustion engine, which includes a conditioning apparatus in which also a second medium is introduced via a dispensing apparatus which is connected to the conditioning apparatus and via which the first medium and the second medium are introduced into the exhaust gas system, a supply unit for supplying a third medium, which is different from the second medium in its physical properties and/or its chemical composition, is connected to the conditioning apparatus for cleaning of the conditioning apparatus and the dispensing apparatus from constituent parts of the first medium by the third medium or a mixture of the second and the third medium.

Abstract: A system for detecting when a gas concentration sensor has drifted or failed is disclosed. The system has a first gas concentration sensor configured to detect a first gas concentration and generate a corresponding first signal. The system also has a second gas concentration sensor configured to detect a second gas concentration and generate a corresponding second signal. In addition, the system has a controller in communication with the first and second gas concentration sensors. Based on the first and second signals, the controller is configured to provide an out-of-tolerance gas concentration sensor warning.

Abstract: An engine (12) has an exhaust system (16) containing a diesel particulate filter (DPF 20) and timer-based warning structure (30) for detecting and indicating particulate overloading of the DPF as the engine runs.

Abstract: The ECU performs an on-board diagnosis for a NOx sensor. The diagnosis is carried out when an exhaust system of an engine is fully cooled after shut-down of the engine. The diagnosis is carried out after a temperature in the exhaust passage is lowered to an ambient temperature. In the diagnosis proceeding, the ECU activates a heater attached on the NOx sensor. The ECU detects a heating performance of the heater and determines whether the heating performance is sufficient or not. The NOx sensor is in a stable condition after the engine system is fully cooled. Therefore, it is possible to perform the diagnosis while eliminating or suppressing influences of operating conditions of the engine system and a residual heat in the exhaust system.

Abstract: A deviation amount of a downstream air-fuel ratio sensed with a downstream air-fuel ratio sensor, which senses an air-fuel ratio of exhaust gas downstream of a catalyst, from a target air-fuel ratio is integrated during a period in which the downstream air-fuel ratio continuously shows deviations from the target air-fuel ratio while main feedback control and sub feedback control are performed based on outputs of an upstream air-fuel ratio sensor and the downstream air-fuel ratio sensor respectively. The thus-calculated continuous deviation amount of the downstream air-fuel ratio (deterioration degree of exhaust gas purification rate) is compared with an abnormality determination value to determine existence/nonexistence of an abnormal state where the exhaust gas purification rate is deteriorated by an air-fuel ratio variation among cylinders (i.e., state where control center of main feedback control has shifted).

Abstract: An exhaust treatment system is provided having a tank configured to store a supply of reductant. The system also has a heat source configured to heat the reductant and a diverter valve configured to regulate the heat source.

Abstract: A method is provided for operating a diesel engine with reduced emissions. The method comprises combusting a first biodiesel blend fuel in a diesel engine resulting in the production of diesel exhaust gases containing NOx. The diesel exhaust gases are admixed with a second biodiesel blend fuel, and the second biodiesel blend fuel is hydrolyzed to form reducing agents. The diesel exhaust gases containing NOx are passed through an NOx-reducing catalyst to reduce the NOx through a selective catalytic reduction reaction with the reducing agents. The invention further provides a method for operating a diesel engine with reduced emissions, comprising combusting a first biodiesel blend fuel in a diesel engine resulting in the production of diesel exhaust gases containing NOx. A second biodiesel blend fuel is converted in a fuel processor thereby forming reducing agents, and the diesel exhaust gases are admixed with the reducing agents.

Abstract: A pulse attenuator for the EGR line of an internal combustion engine in which a main flow path has a pair of branch flow paths extending from the upstream portion of a venturi. The branch flow paths have a precisely determined length so as to reintroduce pulses back to the main flow path in a way that smoothes the flow. The pulses may be reconnected to the main flow path downstream of the point at which they are extracted or at the same point. The length of the branch passages may be different to provide attenuation of pulses at different engine rpms.

Abstract: A motor vehicle exhaust system has at least a first housing for a pollution control element, a nozzle in the housing and a ventilation path into the housing through which outside air is drawn into the exhaust system for mixing with an exhaust flow following the nozzle.

Abstract: An exhaust system to remove exhaust from an engine of a vehicle may include a first exhaust member to conduct the exhaust from the engine of the vehicle to the atmosphere and a source of pressurized fluid which may be air or gas to conduct the pressurized fluid to the first exhaust member to cool the exhaust from the engine of the vehicle. The source of pressurized fluid may be a blower, and the source of pressurized fluids may be a air dam. The blower may be connected to a battery of the vehicle, and the blower may include a sensor to determine if a predetermined speed has been reached to allow ram air input or to warn of back pressure, high temperature or current flow. The sensor may inactivate the blower when the predetermined speed has been reached. The source of pressurized fluid may be compressed air, and the source of the pressurized fluid may be refrigerated air.

Abstract: The invention concerns an exhaust conduit (1) comprising an outer tube (3) and an inner tube (2) positioned inside the outer tube (3) so as to delimit, between those two tubes (2, 3), a peripheral volume (4) inside which is implanted a material (5) for thermal insulation of said conduit (1) and at one first end (6) of said conduit (1), first means (8) for connection to a first exhaust element and at a second end (7) of said conduit (1), second means (9) for connecting said pipe (1) to a second exhaust element comprised in said exhaust line. Said conduit (1) is characterized in that it comprises, proximate its second end (7), means (10) for preventing exhaust gases circulating inside the inner tube (2) from penetrating into the peripheral volume (4) delimited by said inner tube (2) and the outer tube (3).

Abstract: An air gap insulated exhaust manifold includes several inlet tubes which are fit into one another so as to be movable relative to each other and complement each other so as to constitute a collecting chamber. The inlet tubes are surrounded by an outlet tube, an air gap resulting between the inlet and outlet tubes. Two shell-type intermediate plates are provided in this air gap and complement each other so as to constitute a hollow body, which prevents that any leakage flows directly hit the outlet tube. The intermediate plates are produced by deep-drawing a pimpled foil.

Abstract: A cooling liner having a liner hot sheet formed as a relatively thick iso-grid structure having iso-grid ribs, which extend from a surface between the ribs. A multitude of metering sheets are mounted directly to the liner hot sheet surface. Each metering sheet is mounted to the iso-grid to define a multitude of discrete chambers. A seal is located in a pattern along a subset of the iso-grid ribs to further segregate the surface covered by each metering sheet into a further number of discrete subchambers. Each metering sheet includes a multitude of metering sheet apertures and the surface between the iso-grid ribs of the liner hot sheet include a multitude of hot sheet apertures. By varying the ratio between the number of metering sheet apertures and the number of hot sheet apertures, the pressure in each chamber is defined to efficiently maintain the minimum desired pressure ratio across the hot sheet without undue wastage of cooling airflow.

Abstract: A system is described for storing, delivering and recovering energy, provided with a cylinder-piston assembly for absorbing a mass-induced load, which assembly is in fluid connection with a pressure source. The effective surface area of the piston of the cylinder-piston assembly is variable. The cylinder-piston assembly consists of, for instance, a number of cylinders connected in parallel, which can be selectively powered by the pressure source.

Abstract: A hydraulic power steering system that maintains proportional pressure control between an input side of a gear and assist pressures internal to the steering gear by relying upon a control valve. A pressure differential is maintained between the input side of a gear and assist pressures internal to the steering gear throughout certain events. Those events include running the pump to fully charge the accumulator, idling the pump after fully charging the accumulator, discharging pressure from the fully charged accumulator at an onset of a steering event having a demand for steering load, recovering the discharged pressure of the accumulator by running the pump after turning on the pump at the onset of the steering event, and opening the relief valve in the valve manifold during the steering event.

Abstract: A variable capacity pump and two variable capacity motors are connected in a closed circuit. First to fourth drive gears are fitted to motor shafts of the variable capacity motors via clutches. A first driven gear, which meshes with the first and third drive gears, and a second driven gear which meshes with the second and fourth drive gears are fitted to an output shaft. Equivalent capacities of the variable capacity motors are made different. Control is exerted such that the capacities are decreased to zero in order of equivalent capacities. To decrease the capacity of each variable capacity motor, the gear change ratio of the variable capacity motor the capacity of which has decreased to zero is changed to decrease the equivalent capacity and, at the same time, the capacity is increased to maximum. This increases the gear change ratio for the continuously variable transmission and controls acceleration.

Abstract: The invention provides a hydraulic inerter mechanism, including: a hydraulic cylinder; a hydraulic motor connected to the hydraulic cylinder, with an output shaft thereon for converting the motion of the hydraulic cylinder from rectilinear motion to rotary motion; and an inertia body disposed on the output shaft. In operation, an external force applied to the inerter mechanism causes displacement of the piston, thereby pushing working fluid inside the hydraulic cylinder to generate a pressure difference between an inlet and an outlet of a hydraulic motor. The differential pressure consequently drives the hydraulic motor to rotate, and then the output shaft further drives the inertia body to rotate, thereby attaining inerter characteristics.

Abstract: A hydraulic control apparatus for marine reversing gear assembly for watercraft includes a pressure reducing valve 22 for adjusting the pressure of a working oil supplied from a working oil supply pump 1, and supplying the working oil to forward and reverse clutches 2a, 2f; a proportional electromagnetic valve 21 for controlling the supply of the working oil to a pilot chamber of the pressure reducing valve 22; and a spring-type switching valve 23 for switching to a circuit for supplying the working oil to a control piston chamber for controlling a set spring force of the pressure reducing valve 22 or to a circuit for draining the working oil from the control piston chamber; wherein a pressure output from the proportional electromagnetic valve 21 acts upon the switching valve 23 as a pilot pressure; and wherein, when the pilot pressure falls below a predetermined value, the switching valve switches to the circuit for supplying the working oil to the control piston chamber via the spring of the switching valve

Abstract: A rotary heat engine having a cylinder and a rotor having a rotating shaft rotatably placed in the cylinder. The cylinder has a heat receiving section for supplying heat to the inside of the cylinder and a heat radiating section for radiating heat from the inside. The engine also has an engine section body and an operation liquid storage section. A vaporized gas supply channel and a gas recovery channel communicating with the inside of the cylinder are provided, respectively, on the heat receiving section side and heat radiating section side of the cylinder in the engine section body. The operation liquid storage section is between the vaporized gas supply channel and the gas collection channel in order to aggregate and liquefy recovered gas and is installed such that both channels fluidly communicate with each other. Also, the operation liquid storage section has a heat insulation dam provided with a through hole for preventing backflow of fluid flowing inside.

Abstract: An exhaust gas turbocharger for an internal combustion engine has a compressor arranged in an intake tract of an internal combustion engine for precompression of air passing through the intake tract to the compressor. A switchable air guiding device is arranged upstream of the compressor, wherein the switchable air guiding device supplies an air flow to the compressor in at least two different ways. The air guiding device has at least two components, wherein the at least two components are substantially made from plastic material.

Abstract: In an exhaust manifold for an internal combustion engine including a central part with tow exhaust gas flow ducts extending from the central part in opposite directions for collecting exhaust gas from first and respectively second cylinder groups of the engine, the center part includes a first control valve for controlling the exhaust gas flow from the first and the second cylinder groups to first and second turbine inlet flow passages, a second control valve for controlling the exhaust gas pressure and a third control valve for controlling the exhaust gas recirculation rate.

Abstract: A natural gas compression system is provided. The system may include a natural gas compressor configured to compress, and thereby pump, natural gas through a pipeline. The system may also include a natural gas burning engine, operatively coupled to the gas compressor, the engine being supplied with air by an induction system. The induction system may include a supercharger driven by the engine and configured to compress intake air and a turbocharger downstream from the supercharger and driven by exhaust gases produced by the engine. The induction system may also include a supercharger compressor bypass configured to selectively recirculate a portion of the compressed output of the supercharger upstream of the supercharger.

Abstract: In a turbocompound engine drive including an engine with a crankshaft, an exhaust gas turbine operatively connected to the crankshaft via a reduction gear structure and a hydrodynamic clutch providing together for a power transmission path between the engine a freewheel is integrated into the power transmission path between the turbine and the crankshaft of the engine for disconnecting the turbine from the engine when the turbine speed is lower than the comparable engine speed to prevent the turbine from being driven by the engine.

Abstract: A system for generating energy which utilizes motive chemicals 40 with boiling point temperatures in the range of ?5° C. to 45° C. These temperatures are within the typical range of temperatures found near or at the earth's surface. Heat is transferred from the surroundings to a boiling chamber 10 and then the motive chemical. Vapor pressure is generated which turns a gas turbine 14. The motive chemical passes through the turbine and condenses in the condensation chamber 14, at ambient air, ground or fluid temperatures using no supplemental energy source. The condensation chamber returns the motive chemical to its liquid state. Gravity acting on the motive chemical drives a fluid turbine 24. The fluid is returned to a holding chamber 26. When the motive chemical is depleted in the boiling chamber, the motive chemical is transferred from the holding chamber to the boiling chamber and the cycle begins again.

Abstract: A power generating system comprises a water supply system for supplying water; a solar heating device having a water inlet and a water outlet; the water inlet being connected to the water supply system; the solar heating device receiving water from the water supply system and then the water being preheated in the solar heating device; a steam generating device connected to the water outlet of the solar heating device for storing hot water preheated from the solar heating device; a hydrogen-fuel generating device for electrolyzing water into hydrogen and oxygen as fuels; a combustion heating device for reheating hot water from the steam generating device; the fuel of the combustion heating device being hydrogen and oxygen from the hydrogen-fuel generating device; and a steam electric-power generator receiving steam from the steam generating device for generating electric power and then the electric power being outputted.

Abstract: An integrated energy production system and carbon dioxide reaction system for enhancing the energy efficiency and minimizing greenhouse gas emissions of thermally activated power production methods. The system utilizes heat of reaction from the carbon dioxide reaction system to directly reduce the fuel requirements of the thermally activated power production method. The system, when utilizing a reverse fuel cell, achieves concurrent carbon dioxide sequestration resulting from the fuel combustion.

Abstract: A gas turbine combustor. The gas turbine combustor may include a central combustion nozzle with a catalyst therein and a number of outer combustion nozzles surrounding the central combustion nozzle.

Abstract: A premixing device is provided. The premixing device includes a fuel inlet configured to introduce a fuel within the premixing device and an air inlet configured to introduce air within the premixing device. The premixing device also includes a plurality of swirler vanes configured to provide a swirl movement to the fuel and/or air to facilitate mixing of the fuel and air to form a gaseous pre-mix, wherein a shape of each of the plurality of swirler vanes is selected to control an axial velocity profile of the fuel and/or air within the premixing device.

Abstract: Embodiments for an apparatus and associated method for reducing the residence time in a gas turbine combustor are disclosed. The embodiments of the present invention comprise a fuel nozzle that extends to a downstream plane of an end cap for a combustion liner where the axial distance of the premixer is reduced, however the swirl for mixing the fuel and air, is increased. As a result, the mixing of the fuel and air is essentially unchanged, thereby allowing higher air pressures and operating temperatures within the premixer without inducing auto-ignition.

Abstract: An apparatus and method of providing a gas turbine combustor having increased combustion stability and reducing pressure drop across a gas turbine combustor is disclosed. A plurality of vanes is fixed to a flow sleeve radially between the flow sleeve and a combustion liner. The plurality of vanes serve to direct a flow of air entering the region between the flow sleeve and combustion liner in a substantially axial direction, such that components of tangential velocity are removed thereby providing a more uniform flow of air the combustion chamber and reducing the amount of pressure lost due attempting to straighten the airflow by pressure drop alone.

Abstract: An outer liner of a combustor of a gas turbine engine includes a plurality of liner regions arranged adjacent one another and separated by boundary lines; and a plurality of air admission holes formed in the liner regions. The air admission holes within each liner region form a V-pattern.

Abstract: A gas-turbine lean combustor includes a combustion chamber (2) and a fuel nozzle (1) which includes a pilot fuel injection (17) and a main fuel injection (18). The main fuel injection (18) includes central recesses (23) for a controlled inhomogeneous fuel injection, the number of said recesses on the circumference ranging from 8 to 40 and said recesses having an angle of inclination ?2 in circumferential direction of 10°??2?60° and an axial angle of inclination ?1 relative to the combustor axis (4) between ?10°??1?90°.

Abstract: The present invention improves the reliability of a combusting system including multiple combustors and improves an environmental performance thereof. The invention includes a device that delays the start time of fuel injection from a fuel nozzle of a combustor including a ignitor from the start time of fuel injection from a fuel nozzle of the combustor not including the ignitor.

Abstract: A burner for a gas-turbine engine has a frustoconical burner shell, at least two swirler arrangements, which are connected to the shell and are spaced apart around the circumference of the shell between its two ends, and a combustion chamber disposed downstream of a wider end of the shell. Each of the swirler arrangements includes an air swirler and a pre-combustion chamber disposed downstream of the air swirler, and a longitudinal axis of each swirler arrangement intersects a line parallel to, and spaced apart from, the longitudinal axis of the shell. The swirler arrangements are preferably connected to the shell at the same axial point.

Abstract: A gas turbine engine includes an accessory gearbox within an engine pylori. The accessory components may be mounted within the engine pylori to save weight and space within the core nacelle as well as provide a relatively lower temperature operating environment.

Abstract: Certain embodiments disclosed herein are directed to devices for cooling. In certain examples, a thermoelectric device comprising a substrate and a superlattice coupled to the substrate is disclosed. In some examples, the superlattice includes a first semi-conducting material and a second semi-conducting material coupled to the first semi-conducting material to provide an interface between the first and second semi-conducting materials.

Abstract: Systems and methods for cooling the contents within a portable case, such as a transit case, using a thermoelectric air conditioner. Thermoelectric air conditioners are used with, and mounted on or in, a transit case for maintaining a desired air temperature within the transit case. In one embodiment, the thermoelectric air conditioner can be incorporated, concealed within the housing and/or cover of the transit case. In this embodiment, the thermoelectric air conditioner is protected by the design of the case, the mounting arrangement, the shock-mounted frame, etc. Alternatively, the thermoelectric air conditioner is mounted partially internal and partially external to the transit case. In another embodiment, the thermoelectric air conditioner is mounted external to the transit case.

Abstract: A refrigerant system control software upgrades are remotely downloaded over information carrying media. The software upgrades can be timed to occur when the Internet traffic is low. Once the upgrade has been received, a verification test may be performed for the refrigerant system components affected by the software upgrade. The test is monitored, and the results are sent back to the remote location such that the remote location can ensure the software upgrade was successful.

Abstract: Rapid chilling apparatus for beverages comprising a receptacle (2) adapted to accommodate beverage containers (3) of differing length, and cooling means adapted to cool down said receptacle (2), wherein said receptacle (2) comprises a plurality of electrodes (4) arranged in succession one after the other along an inner surface (5) of said receptacle (2), said inner surface (5) being adapted to support a container (3) in such manner that the electrodes (4) turn out as being distributed along the whole length of the container (3), said electrodes (4) being connected to circuit means (6) adapted to detect and measure the capacitance value on each electrode (4) as brought about by the presence of a container (3) made of a conductive material in proximity of the same electrode (4) so as to determine the actual length of the container (3), or, in the case of a container (3) made of a non-conductive material, said capacitance value as brought about by the presence, inside the container, of beverage liquid in proximi

Abstract: Disclosed is a device for the transport of temperature sensitive products including an insulated container, an insulated lid, a fastener to secure the lid to the container, an active heat exchanger, a thermal circuit to circulate heat exchange, a temperature sensor read by a temperature regulating circuit that maintains a temperature range, a power source, and a support frame that arranges the elements of the device with the overall center of mass at a location adapted for transport and storage of the device. Disclosed is also a method of transport for temperature sensitive products including securing the temperature sensitive product within an insulated container with a lid, removing heat from the container to maintain a temperature range, strapping the device onto the user's back and adjusting to the shape of the user, freeing both hands during transport of the device, and minimizing hindrances to user mobility caused by the device.

Abstract: An apparatus for maintaining the freshness of foods is provided. The apparatus comprises first and second electrodes spaced oppositely to a predetermined distance, a voltage generator unit applying voltage between the first electrode and the second electrode, heat transfer means connected to the first electrode or the second electrode to absorb heat from the space between the first electrode and the second electrode, and a temperature control unit controlling the heat transfer means such that the space between the first electrode and the second electrode is of predetermined temperature, whereby the heat transfer means is connected to the electrode for voltage application, so that both the application of electric field and the temperature regulation are advantageously obtained using a single electrode without installing a separate device for temperature regulation.

Abstract: A defrost indicator is configured such that the process of freezing and defrosting the defrost indicator places the defrost indicator into a state that is not completely reversed by refreezing, so that one can detect whether the defrost indicator defrosted and refroze or never defrosted by observing its current state. In an embodiment, the defrost indicator is initially placed in a first state before being frozen (e.g., upside down with fluid in an upper chamber). Freezing the defrost indicator places it in a second state (e.g., with the fluid frozen in the upper chamber). Then when the defrost indicator is defrosted, the defrost indicator is placed into a third state that is different than the first state (e.g., right-side-up with liquid fluid in the lower chamber). If the defrost indicator is again frozen, the defrost indicator is placed into a fourth state (e.g., the fluid frozen in the lower chamber).

Abstract: An air-conditioning system capable of reducing traffic of signals and effectively performing control and management operations without causing heavy traffic is obtained. In an air-conditioning system including one or more indoor units 200, one or more outdoor units 100, and a centralized control apparatus 300 and performing signal communication, a transmission relay 400 is provided between a first transmission line 500 to which the one or more outdoor units 100 and the centralized control apparatus 300 are connected and a second transmission line 510 to which one or more indoor units 200 constituting a group are connected, the transmission relay 400 relays a signal between the first transmission line 500 and the connected second transmission line 510.