Aircraft ground support air conditioning unit with cooling air flow control doors

A system and method of supplying conditioned air to an aircraft environmental control system during ground support operations that uses at least one flow control door to control the flow of cooling air through a heat exchanger. The heat exchanger removes heat from a flow of compressed air supplied to the system. The temperature of the conditioned compressed air is controlled by selectively positioning the flow control door, which regulates cooling air flow through the heat exchanger.

FIELD OF THE INVENTION

The present invention relates to environmental control systems for aircraft and, more particularly, to a modular air conditioning ground unit for supplying conditioned air to an aircraft environmental control system during ground support operations.

BACKGROUND OF THE INVENTION

Aircraft main engines not only provide propulsion for the aircraft, but in many instances may also be used to drive various other rotating components such as, for example, generators and pumps. The main engines may also be used to supply compressed air to the aircraft's environmental control system, which may be used to supply temperature-controlled air to both the aircraft cabin and to electronic equipment within the aircraft.

When an aircraft is on the ground and its main engines are not being used, an alternative power source may be used to supply power for ground support operations. In addition, during some ground support operations, an external supply of cooling and heating air may be used to supply temperature-controlled air to the cabin and aircraft equipment. For some type of aircraft ground support applications, most notably military aircraft ground support applications, a ground cart may be used to supply electrical power to the aircraft and compressed air to an air conditioning system module. The air conditioning module in turn may supply temperature-controlled air to the aircraft cabin and the aircraft's electronic equipment.

One particular air conditioning system module that may be used during aircraft ground support operations receives high temperature (e.g., ≧300° F.) compressed air supplied by the ground cart, and conditions the compressed air to a predetermined temperature. The air conditioning system module may be used in at least two modes, a cooling mode, to supply cool air, or a heating mode, to supply warm air. To do so, the air conditioning system module may include a primary heat exchanger, a condenser, a moisture separator, and one or more cooling turbines. Typically, this air conditioning system module is designed so that when it is operating in the cooling mode it will supply cool air at a predetermined desired temperature for a given, predetermined design ambient temperature. For example, the system may be designed to supply cooling air at a temperature no higher than 55° F. when the ambient temperature is 125° F. Thus, when actual ambient temperature is below the design ambient temperature, the air conditioning system may supply cooling air that is less than 55° F.

In some instances, supplying air to an aircraft at less than 55° F. may not be desirable. Moreover, in some instances, it may be desirable to supply heating air to an aircraft at temperatures of up to 200° F. Hence, the air conditioning system module may include a bypass flowpath for use in the heating mode. The bypass flowpath allows a portion of the high temperature compressed air to flow around the primary heat exchanger, and back into the cooled compressed air stream that is exhausted from the primary heat exchanger. For example, a valve may be installed in a bypass duct, and the valve may be positioned to control hot compressed air bypass flow rate, to thereby control the temperature exiting the primary heat exchanger, and in turn controlling the temperature of the air being supplied by the air conditioning system module.

Although the above-described system and method for controlling air temperature to an aircraft during ground support operations, in both a cooling mode and a heating mode is effective, it suffers certain drawbacks. For example, it can be difficult to consistently control the temperature of the air by feeding a portion of the hot compressed air back into the compressed air that has been cooled. In addition, the cost of the air conditioning system module may be increased because high temperature ductwork and a high temperature valve may be needed to implement the compressed air bypass flow path.

Hence, there is a need for a system and method of providing conditioned air to an aircraft environmental control system during ground support operations that does not use hot compressed air to control air supply temperature when ambient temperature is below the maximum design temperature and/or is less costly than presently known systems and methods. The present invention addresses one or more of these needs.

SUMMARY OF THE INVENTION

The present invention provides a system and method of supplying conditioned air to an aircraft environmental control system during ground support operations that is simple, efficient, and does not adversely affect system costs.

In one embodiment, and by way of example only, a temperature-controlled air supply system for use with an aircraft on the ground and for connection to a compressed air source includes a primary air flow passage, a first heat exchanger, and an inlet door. The primary air flow passage has an inlet port and an outlet port. The inlet port is coupled to receive a flow of primary air. The first heat exchanger has at least a first fluid flow path and a second fluid flow path. The first fluid flow path is fluidly coupled in series with the primary air flow passage, and the second flow path is coupled to receive a flow of compressed air from the compressed air source. The first heat exchanger is adapted to transfer heat from the compressed air to the primary air and to supply conditioned compressed air and warmed primary air. The inlet door is mounted on the inlet port and selectively moveable between an open and a closed position to control primary air flow rate through the primary air flow passage, whereby primary air flow rate through the first heat exchanger is controlled to thereby control conditioned compressed air temperature.

In yet another exemplary embodiment, a method of supplying conditioned compressed air at a predetermined temperature to at least one section of an aircraft during ground support operations is provided. The method includes the steps of flowing compressed air through a first heat exchanger flow path and controlling primary air flow rate through an inlet port and a second heat exchanger flow path that cools the compressed air by selectively positioning at least one air inlet door that is mounted on the inlet port, whereby the predetermined temperature of the conditioned compressed air is controlled.

Other independent features and advantages of the preferred air conditioning system will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

A simplified schematic representation of a ground cart100with a modular aircraft ground support air conditioning unit200mounted thereon is depicted inFIG. 1. The ground cart100includes a housing102and varying numbers of rotationally mounted wheels104, which allow the cart100to be readily transported to one or more aircraft. Various systems and components may be mounted within the housing102to supply power and compressed air for ground support operations. In the depicted embodiment, an auxiliary power unit (APU)106is shown. It should be appreciated that other systems and components may also be installed in the ground cart100, but for the sake of clarity and ease of description, only a single APU is depicted.

The general operation and configuration of turbine APUs is well-known in the industry. In the depicted embodiment, APU106includes a combustor108, a power turbine112, and a compressor114. During APU operation, the combustor receives fuel116from a fuel source (not illustrated) and supplies high energy air to the power turbine112causing it to rotate. The power turbine112includes a shaft118that may be used to drive a generator (not illustrated) for supplying electrical power, and to drive the compressor114. The compressor114draws in ambient air122, compresses it, and supplies compressed air124to the air conditioning module200. It should be appreciated that the present embodiment is not limited to use with an APU as the compressed air source, and that various other devices and systems for supplying compressed air to the air conditioning module200may also be used. For example, a diesel or other type of engine driving a compressor or other engine-compressor types, or any type of stationary compressor, may also be used to provide compressed air.

The air conditioning module200receives the compressed air124from the APU106, and primary cooling air126from a source such as, for example, ambient air, that is drawn into and through the air conditioning module200. The air conditioning module200functions to supply temperature-controlled air128to, for example, the environmental control system (ECS) in an aircraft. To accomplish this function, the air conditioning module200, as depicted more clearly in schematic form inFIG. 2, includes a first heat exchanger202, a second heat exchanger204, a water separator206, a cooling turbine208, and a primary air flow passage212.

The primary air flow passage212receives a flow of primary cooling air126, via an inlet port215, and exhausts a flow of warmed primary cooling air227, via an outlet port218. One or more flow control doors127are positioned in the inlet port215. The flow control doors127are moveable and may thus be selectively positioned to control the flow of primary cooling air126through the primary air flow passage212. In the depicted embodiment, a plurality of flow doors127are used to control primary air flow rate. It will be appreciated that the flow control doors127are not limited to doors, but may also be any one of numerous flow control components including, but not limited to, one or more gates, one or more dampers, or one or more moveable orifices, that may regulate the flow of primary cooling air126through the primary air flow passage212. Moreover, a single flow control door127could be used rather than multiple doors, and the one or more flow control doors127could be positioned on the primary air flow passage outlet port218.

A fan228draws the primary cooling air126into the air conditioning module200through the primary air flow passage212. In the depicted embodiment, the fan228is positioned within the air conditioning module200to “pull” the uncompressed cooling air126through the first heat exchanger202. It will be appreciated that the fan228could also be positioned within the air conditioning module200to “push” the uncompressed cooling air126through the first heat exchanger202. Alternatively, the fan228may be eliminated if an outside power source is used to move air through the primary air flow passage212.

The first heat exchanger202includes at least two flow paths. The first fluid flow path201is fluidly coupled in series in the primary air flow passage212. The second fluid flow path203is coupled to receive the compressed air124supplied from the APU106. As the primary cooling air126flows through the first fluid flow path201, it cools the compressed air124as it flows through the second fluid flow path203. Thus, the first heat exchanger202not only receives the primary cooling air126and the compressed air124, it also supplies warmed primary cooling air236and conditioned compressed air234.

The conditioned compressed air234that exits the first heat exchanger second flow path203is directed through the second heat exchanger204. In the second heat exchanger204, the conditioned compressed air234from the first heat exchanger202is further cooled by another flow of air. Specifically, air244that is exhausted from the cooling turbine208is also directed through the second heat exchanger204, and is used to further cool the conditioned compressed air234from the first heat exchanger202. The cooling turbine exhaust air that is warmed by the compressed air in the second heat exchanger204flows out the temperature-controlled air supply port216, which supplies the temperature-controlled air128to, for example, an aircraft.

The further conditioned compressed air238flowing out of the second heat exchanger204may contain moisture. Therefore, this air is directed through the moisture separator206. The moisture separator206may be any one of numerous devices known now, or provided in the future, for removing moisture from a flowing gas. In a particular preferred embodiment, the moisture separator206is the type that removes moisture by centrifugally separating free water droplets from the air flow, and exhausting the free water. Thereafter, the dry, further conditioned compressed air242that exits the moisture separator206is directed into the cooling turbine208. This air242impinges upon rotating blades (not illustrated) in the cooling turbine208, causing the blades to rotate. As the air impinges on the rotating blades, work is extracted from the air, cooling the air even further. As noted above, the air244exhausted from the cooling turbine208is then directed through the second heat exchanger204where it is warmed and directed out the temperature-controlled air outlet port216, supplying the temperature-controlled air128.

The temperature of the air that exits the temperature-controlled air outlet port216is determined by the temperature of the conditioned compressed air234that exits the first heat exchanger202. Moreover, the temperature of the conditioned compressed air234can be controlled by controlling the flow of primary cooling air126through the first heat exchanger202. The flow of primary cooling air126through the first heat exchanger202may in turn be controlled by controlling the flow of the primary cooling air126entering the inlet port215, which may be controlled by selectively positioning various ones of the inlet doors127. Hence, the temperature of the temperature-controlled air128exiting the outlet port216may be controlled by controlling the position of the air inlet doors127.

Various control schemes can be used to selectively position the air inlet doors127, including various manual and automatic control schemes. In the embodiment depicted inFIG. 2, the inlet doors are selectively positioned manually. However, in the embodiment shown inFIG. 3, an automatic control scheme is used. With this embodiment, a temperature sensor246is positioned in the temperature-controlled air outlet port216. The temperature sensor246may be any one of numerous sensors including, but not limited to, a capillary bulb temperature sensor, a resistance temperature detector (RTD), a thermocouple, or an optical temperature sensor. The temperature sensor246supplies a signal248representative of the temperature of the air128exiting the temperature-controlled air outlet port216to a controller250. The controller250processes the temperature signal248and supplies one or more appropriate control signals252to one or more actuators254that are coupled to the inlet doors127. The control signals252cause the actuators254to position the inlet doors127, as necessary, so that the temperature of the air128exiting the temperature-controlled air outlet port216achieves the desired temperature.

It should be appreciated that the position of the temperature sensor246is not limited to the temperature-controlled air outlet port216, but could instead be located in any one of numerous positions downstream of the first heat exchanger202. For example, the temperature sensor246could be positioned so that it directly senses the temperature of the conditioned compressed air234exiting the first heat exchanger202. It will be appreciated that in any one of the numerous positions, the temperature sensor246will supply a temperature signal representative of the temperature of the conditioned compressed air234exiting the first heat exchanger202. It will additionally be appreciated that the inlet door actuators254could be any one of numerous types of actuators including, but not limited to, pneumatic, hydraulic, and electric. Various automatic control schemes may be used as needed for particular applications and configurations.

In another alternative configuration, which is illustrated inFIG. 4, the air conditioning module may additionally include a bypass flow passage214that is fluidly coupled in parallel with the primary air flow passage212. In the depicted embodiment, the bypass flow passage214includes an inlet port222in fluid communication with the primary air flow passage inlet port215, and an outlet port224in fluid communication with the primary air flow passage outlet port218. It will be appreciated that this configuration is only exemplary of a particular preferred embodiment, and that various other configurations can be used, including the one depicted in phantom inFIG. 4, in which an alternative bypass flow passage inlet223is in fluid communication with the source of the primary cooling air126may be used.

A bypass valve226is mounted on the bypass flow passage214. The bypass valve226may be any one of numerous known valve designs presently known in the art, or developed in the future, but the presently preferred valve design is a butterfly valve. The bypass valve226is selectively moveable between a closed and an open position, and it may be positioned to further control the flow rate of primary cooling air126through the first heat exchanger202. Similar to the air inlet doors127, the bypass valve226may be positioned using various manual and automatic control schemes. In the depicted embodiment, an automatic control scheme is used, and the same controller250and temperature sensor246that are used to control the air inlet doors127are used to control the bypass valve226. It will be appreciated, however, that a separate temperature sensor and controller could be used to control the bypass valve226.

The air conditioning module200may be configured to operate in either a cooling mode or a heating mode. In the cooling mode, the air conditioning module200can supply conditioned compressed air at a temperature of about 55° F. or less, when ambient temperature is at or below 125° F. In the heating mode, the air conditioning module can supply conditioned compressed air at a temperature up to about 200° F., when ambient temperature is at or above approximately −40° F. In a particular preferred embodiment, the air inlet doors127remain in a full-open position when operating the air conditioning module200in the cooling mode, and are moved out of the full-open position, to control primary air flow when operating the air conditioning module200in the heating mode. In a particular preferred embodiment, primary air flow is controlled using a combination of both the air inlet doors127and the bypass valve226. However, it should be appreciated that the air conditioning module200could be operated and configured such that the air inlet doors127are used to control primary air flow in either, or both, the cooling and heating modes, and with or without the bypass valve226.

The temperature control system and method implemented in the air conditioning module allows the temperature of the air supplied by the module to be more precisely and more easily controlled, and to supply the air at temperatures of up to 200° F. when ambient temperature is as low as −40° F. In addition, because high temperature and/or pressure ductwork and valves are not needed, the system and method reduce the cost of the air conditioning module as compared to present configurations.