System and method for providing cooling air within a vehicle

Abstract

Vehicle cooling air supply system and method A system and method for supplying cooled air to a vehicle, such as an aircraft, is disclosed. The system includes an air cycle machine (ACM) configured to compress and cool a flow of air to generate a cooled flow of air, an air flow path configured to direct the cooled air from the ACM to one or more portions of the vehicle, and a phase change material (PCM) heat exchanger positioned to further cool the air before it reaches at least one of the one or more portions of the vehicle in addition to the cooling provided by the ACM.

Description

[Technical Field]

[0001] The present invention relates to a system for supplying cooling air to a vehicle, such as an aircraft. In particular, the present invention relates to a system comprising an air cycle machine, such as an electric air cycle machine (E-ACM). [Background technology]

[0002] Vehicles typically include air cooling systems that can be used to remove heat from specific portions or areas of the vehicle as needed. For example, air may be supplied to the driver or passenger compartment to help maintain the environment within a comfortable temperature range for any human occupants. Air cooling can be used in other portions of the vehicle as well, for example, to remove waste heat generated by electronic components such as avionics components in an aircraft.

[0003] To increase the effectiveness of such systems, an air cycle machine (ACM) can be used to lower the temperature of the air before supplying it to the portion of the vehicle requiring cooling. An ACM operates by compressing air, passing the compressed air through a heat exchanger to remove excess heat generated by the compression, and then expanding the compressed air to further reduce its temperature. In this manner, the ACM can provide a flow of cooled air. However, ACMs can struggle to provide sufficient cooling under peak load conditions, especially in situations where a high mass flow rate of cool air is required. Therefore, it is desirable to provide an improved system for supplying cooled air within a vehicle. Summary of the Invention

[0004] According to a first aspect of the present invention, there is provided a system for supplying cooled air within a vehicle, the system comprising: an air cycle machine (ACM) comprising: an air compression stage arranged to receive and compress a flow of air to produce a flow of compressed air; a heat exchange stage arranged to cool the compressed air; and an air expansion stage arranged to expand the air received from the heat exchange stage to output a flow of cooled air having a temperature lower than a temperature of the air received by the air compression stage; an air flow path configured to direct the cooled air from the ACM to one or more portions of the vehicle; and a phase change material (PCM) heat exchanger arranged to further cool the air before it reaches at least one of the one or more portions of the vehicle, in addition to the cooling provided by the ACM.

[0005] In some embodiments according to the first aspect, the system comprises a controller configured to control the extent to which the PCM heat exchanger further reduces the temperature of the cooling air depending on the load on the system.

[0006] In some embodiments according to the first aspect, the system comprises: a first bypass flow path configured to allow at least a portion of air flowing along the air flow path to bypass the PCM heat exchanger; and a flow control mechanism operable to control a flow rate of air along the first bypass flow path relative to a flow rate of air passing through the PCM heat exchanger, wherein the controller is configured to control the flow control mechanism in response to a load on the system to control an extent to which the PCM heat exchanger further reduces a temperature of the cooled air before the cooled air reaches at least a portion of the vehicle.

[0007] In some embodiments according to the first aspect, the controller is configured to receive first temperature information indicative of a first temperature of the air at a first point along the air flow path upstream of at least one portion of the vehicle and second temperature information indicative of a second temperature of the air at a second point along the air flow path downstream of the at least one portion of the vehicle, a difference between the first temperature and the second temperature indicative of a load on a system associated with the at least one portion of the vehicle, and wherein the controller is configured to control the extent to which the PCM heat exchanger further reduces the temperature of the cooling air in response to the first temperature information and the second temperature information.

[0008] In some embodiments according to the first aspect, the one or more portions of the vehicle comprise at least a first portion and a second portion, and the air flow path is configured for cooled air to pass from the ACM through the first portion to the second portion, wherein the first point along the air flow path is a point upstream of the first portion and the second point along the air flow path is a point downstream of the second portion, and the controller is configured to receive third temperature information indicative of a third temperature of the air at a third point along the air flow path between the first portion and the second portion, wherein a difference between the first temperature and the third temperature is indicative of a load of a system associated with the first portion of the vehicle, and a difference between the second temperature and the third temperature is indicative of a load of a system associated with the second portion of the vehicle, and wherein the controller is configured to control an extent to which the PCM heat exchanger further reduces the temperature of the cooled air in response to the third temperature information in addition to the first temperature information and the second temperature information.

[0009] In some embodiments according to the first aspect, the controller is configured to determine a first load associated with a first portion of the vehicle based on the first and third temperature information, determine a second load associated with a second portion of the vehicle based on the second and third temperature information, and determine a load on the system based on the determined first and second loads.

[0010] In some embodiments according to the first aspect, the one or more portions of the vehicle comprise at least a first portion and a second portion, the air flow path is configured such that cooled air passes from the ACM through the first portion to the second portion, the first point along the air flow path is a point upstream of the first portion, and a difference between the first temperature and the second temperature indicates a total load on a system associated with both the first portion and the second portion of the vehicle.

[0011] In some embodiments according to the first aspect, one or more portions of the vehicle include one or more electronic components, and the controller is configured to receive power information indicative of a level of power currently supplied to the one or more electronic components, and to control the extent to which the PCM heat exchanger further reduces the temperature of the cooling air in response to the received power information.

[0012] In some embodiments according to the first aspect, the controller is configured to increase a velocity of airflow through the PCM heat exchanger to cool the phase change material of the PCM heat exchanger.

[0013] In some embodiments according to the first aspect, the one or more portions of the vehicle comprise at least a first portion and a second portion, and the air flow path is configured such that cooled air passes from the ACM through the first portion to the second portion, and wherein the PCM heat exchanger is disposed along the air flow path between the first portion and the second portion to cool the air received from the first portion before it reaches the second portion.

[0014] In some embodiments according to the first aspect, the PCM heat exchanger is positioned along an air flow path between the ACM and one or more portions of the vehicle to further cool the cooled air flow from the ACM before the cooled air flow reaches the one or more portions.

[0015] In some embodiments according to the first aspect, the PCM heat exchanger is connected between the air compression stage of the ACM and the air expansion stage of the ACM to further cool the compressed air flow before it reaches the air expansion stage.

[0016] In some embodiments according to the first aspect, the one or more portions of the vehicle comprise at least a first portion and a second portion, the air flow path is configured such that cooled air passes from the ACM through the first portion to the second portion, and the PCM heat exchanger comprises: a first PCM heat exchanger disposed along the air flow path between the first portion and the second portion to cool the air received from the first portion before it reaches the second portion; or a second PCM heat exchanger disposed along the air flow path between the ACM and the first portion to further cool the cooled air flow from the ACM before it reaches the first portion; or a third PCM heat exchanger connected between the air compression stage of the ACM and the air expansion stage of the ACM to further cool the compressed air flow before it reaches the air expansion stage, wherein the system further comprises at least one other heat exchanger among the first, second, and third heat exchangers.

[0017] In some embodiments according to the first aspect, the one or more portions of the vehicle comprise at least a first portion and a second portion, the air flow path configured to allow cooled air to pass from the ACM through the first portion to the second portion, and the system comprises a second bypass flow path configured to allow at least a portion of the cooled air from the ACM to bypass the first portion such that at least a portion of the cooled air can flow from the ACM to the second portion without passing through the first portion.

[0018] In some embodiments according to the first aspect, the air flow path is a recirculation air flow path configured to return air from one or more portions of the vehicle to an air compression stage of the ACM to recirculate air within the vehicle.

[0019] In some embodiments according to the first aspect, the air cycle machine is an electric air cycle machine (E-ACM).

[0020] In some embodiments according to the first aspect, the E-ACM is a closed-loop E-ACM.

[0021] According to a second aspect of the present invention there is provided a vehicle comprising a system according to the first aspect.

[0022] In some embodiments according to the second aspect, the vehicle is an aircraft.

[0023] In some embodiments according to the second aspect, the one or more portions of the vehicle comprise at least a cockpit and one or more avionics compartments housing one or more avionics components.

[0024] In some embodiments according to the second aspect, the first portion of the vehicle comprises a cockpit and the second portion of the vehicle comprises one or more avionics compartments.

[0025] According to a third aspect of the present invention, there is provided a method of supplying cooled air within a vehicle, the method comprising: using an air cycle machine (ACM) to generate a flow of cooled air, the ACM comprising an air compression stage arranged to compress air to generate a flow of compressed air, a heat exchange stage arranged to cool the compressed air, and an air expansion stage arranged to expand air received from the heat exchange stage to output a flow of cooled air having a temperature lower than a temperature of the air received by the air compression stage; directing cooled air from the air expansion stage of the ACM around an air flow path from the ACM to one or more portions of a vehicle; and using a phase change material (PCM) heat exchanger to further cool the air before it reaches at least one of the one or more portions of the vehicle, in addition to the cooling provided by the ACM. [Brief explanation of the drawings]

[0026] Embodiments of the present invention will now be described, by way of example only, with reference to the drawings, in which: [Figure 1] FIG. 1 illustrates a system for providing cooling air within a vehicle according to an embodiment of the present invention, the system comprising a phase change material (PCM) heat exchanger positioned to cool a flow of air passing from the cockpit to the avionics compartment. [Figure 2] FIG. 2 illustrates a system for providing cooled air within a vehicle in accordance with an embodiment of the present invention, the system including a PCM heat exchanger positioned to cool airflow passing from an electric air cycle machine (E-ACM) to the cockpit. [Figure 3] FIG. 3 illustrates a system for providing cooled air within a vehicle according to an embodiment of the present invention, the system including a PCM heat exchanger positioned to cool the flow of air passing from the compressor to the turbine of an E-ACM. [Figure 4] FIG. 4 illustrates a system for providing cooling air within a vehicle, the system including multiple PCM heat exchangers, in accordance with an embodiment of the present invention. [Figure 5] FIG. 5 illustrates a system including a mechanism for controlling the degree of cooling provided by a phase change material heat exchanger, according to an embodiment of the present invention. [Figure 6] FIG. 6 is a flow chart illustrating a method for providing cooling air in a vehicle according to an embodiment of the present invention. [Figure 7] FIG. 7 is a cross-sectional view of a PCM heat exchanger according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] According to embodiments of the present invention, systems and methods are provided for providing cooled air within a vehicle. Such systems and methods may involve using an air cycle machine (ACM) to compress, cool, and expand a flow of air to provide a cooled air flow that can be used to cool portions of the vehicle. In the following detailed description, embodiments of the present invention are described in the context of a system for providing cooled air to an aircraft, where the cooled air is used to provide cooling to portions of the aircraft, including the cockpit and avionics components. The aircraft may be, for example, a fixed-wing aircraft, a rotorcraft, or an airship.

[0028] However, as will become apparent from the following description, the principles disclosed herein are not limited to systems for cooling cockpits or avionics components. Thus, in some embodiments of the present invention, a system such as that described below with reference to the drawings may be used to cool other portions of an aircraft other than the cockpit and avionics components.

[0029] Furthermore, embodiments of the present invention are not limited to use in aircraft and may be used to cool portions of vehicles other than aircraft. In some embodiments of the present invention, systems and methods similar to those described below may be used to provide cooling air to other types of vehicles other than aircraft, for example, land vehicles such as trains, automobiles, trucks, buses, and armored vehicles, or marine vehicles such as ships, boats, and submarines. Similarly, although embodiments of the present invention are described below with respect to closed-loop systems comprising closed-loop electric air cycle machines (E-ACMs), the principles disclosed herein may also be applied to open-loop systems and other types of ACMs other than electric ACMs. Accordingly, the following description should be read in this context.

[0030] 1, a system 100 for providing cooled air within a vehicle is illustrated, in accordance with an embodiment of the present invention. System 100 includes an ACM 110, an air flow path 120, a phase change material (PCM) heat exchanger 150, and a controller 160. ACM 110 is configured to provide a flow of cooled air, by which is meant air at a lower temperature than the temperature of the air at the inlet side of ACM 110 before it is compressed within ACM 110.

[0031] In this embodiment, the ACM 110 is an E-ACM comprising an air compression stage 112 in the form of a compressor arranged to receive and compress a flow of air to generate a flow of compressed air, a heat exchange stage 114 arranged to cool the compressed air, and an air expansion stage 116 in the form of a turbine arranged to expand the air received from the heat exchange stage 114 to output a flow of cooled air. Any suitable form of compression may be used in the air compression stage 112 of the ACM 110, including single-state compression or multi-stage compression. For example, the air compression stage 112 may comprise one or more axial or centrifugal compressors.

[0032] In the air expansion stage of this embodiment, the turbine 116 can also help push the cooled air around the airflow path 120. In some embodiments, instead of a turbine, the air expansion stage 116 may simply comprise an expansion chamber into which compressed air is supplied from the heat exchange stage 114, allowing the compressed air to expand and cool. In such embodiments, in the absence of a turbine, an alternative mechanism can be provided to force the cooled air around the airflow path. For example, one or more fans can be disposed around the airflow path 120 to push or draw air along the airflow path 120.

[0033] The E-ACM 110 includes one or more electric motors 118 configured to rotate the compressor 112 and the turbine 116 to compress and expand the airflow, respectively. However, as noted above, other embodiments of the present invention may use different forms of ACMs other than an E-ACM. Thus, in some embodiments, the E-ACM 110 shown in FIG. 1 may be replaced by another type of ACM that uses a different power source to drive the air compression stage 112 and / or the air expansion stage 116, in which case one or more electric motors 118 may be omitted. For example, in some embodiments, the air compression stage 112 and / or the air expansion stage 116 may be powered by bleed air, e.g., by supplying the bleed air to a second turbine connected to the shaft of the compressor 112 to rotate the compressor 112, instead of using one or more electric motors 118. In this context, "bleed air" refers to a separate stream of compressed air that is extracted from the compressor of a gas turbine, such as a gas turbine in an aircraft jet engine.

[0034] 1, airflow path 120 is configured to direct air from turbine 116 of E-ACM 110 to a first portion 130 of the vehicle and then to a second portion 140 of the vehicle. In this embodiment, the vehicle is an aircraft, first portion 130 is the cockpit, and second portion 140 is one or more avionics compartments. The term "avionics" may broadly refer to any electronic components installed in an aircraft.

[0035] In this embodiment, air flow path 120 is configured to direct air from one or more portions of the vehicle, in this case cockpit 130 and avionics compartment 140, back to air compression stage 112 of E-ACM 110 to recirculate air within the vehicle. Thus, air flow path 120 in this embodiment may be referred to as a recirculation air flow path. Similarly, system 100 may be referred to as a closed-loop system, and E-ACM 110 may be referred to as a closed-loop E-ACM.

[0036] In other embodiments, the air flow path may not return air from one or more portions of the vehicle to the air compression stage of the ACM. Instead, the air compression stage of the ACM may draw air from a different source, for example, from outside the vehicle. Similarly, warm air that has passed through one or more portions of the vehicle may be exhausted outside the vehicle rather than captured and returned to the ACM. Such a system may be referred to as an open-loop system, and in such a system, the ACM may be referred to as an open-loop ACM.

[0037] One drawback of ACM-based cooling systems is that the ACM can struggle to efficiently provide sufficient cooling under peak load conditions, especially in situations where high mass flow rates of cool air are required. For example, when the vehicle is a high-performance aircraft capable of performing advanced maneuvers at high speeds, such as a fighter jet, the thermal load on parts of the vehicle can vary significantly from moment to moment depending on the motion of the aircraft. As just one example, when an aircraft rapidly accelerates to supersonic speeds, frictional heating of the cockpit's glass canopy can significantly increase the thermal load on the cockpit. At other times, the thermal load on the cockpit can be much lower.

[0038] To increase the maximum achievable mass flow rate, one potential solution is to modify the ACM to increase the maximum achievable throughput of the air compression and expansion stages, for example, by using larger compressors and turbines, which may require changes to the heat exchangers to increase their cooling capacity. However, the drawback of this approach is the increased size, mass, cost, and complexity of the ACM.

[0039] Thus, embodiments of the present invention take a different approach to enabling system 100 to continue providing a high mass flow rate of cool air even under peak load conditions by using a phase change material (PCM) heat exchanger to further cool the air before it reaches the vehicle portion, in addition to the cooling provided by the ACM. PCM heat exchanger 150 comprises a phase change material capable of absorbing heat from the air flowing along air flow path 120. Specifically, a phase change material is a material that absorbs heat in a process that changes from one phase of matter to another, for example, from solid to liquid or from liquid to gas. One example of a phase change material that may be used in PCM heat exchangers according to embodiments of the present invention is paraffin wax. However, embodiments of the present invention are not limited to paraffin wax-based PCM heat exchangers; in other embodiments, PCM heat exchangers may use different phase change materials. For example, in some embodiments, the PCM heat exchanger phase change material may comprise one or more of a salt, an organic solution, a hydrated salt, or any other suitable material.

[0040] For phase change materials that transition from solid to liquid, the material absorbs an amount of energy at least equal to the latent heat of fusion. For phase change materials that transition from liquid to gas, the material absorbs an amount of energy at least equal to the latent heat of vaporization. Phase change materials can also absorb additional thermal energy due to heating of the material before or after the phase change occurs, in which case the amount of additional energy absorbed is equal to the specific heat capacity of the material multiplied by its mass in kilograms and the temperature rise in degrees Celsius (Delta T). In some embodiments, the phase change material may be selected to undergo both transitions within PCM heat exchanger 150, i.e., solid to liquid, followed by liquid to gas, over the temperature range expected to be experienced by PCM heat exchanger 150 under typical operating conditions of the vehicle in which the system is installed. This can increase the total amount of energy that can be absorbed by the phase change material.

[0041] After some or all of the phase change material absorbs energy from the air flowing along airflow path 120 and undergoes a phase change, the phase change material can later release the absorbed thermal energy to the external environment, thereby cooling the phase change material back to its original state. In this manner, the phase change material in PCM heat exchanger 150 can temporarily increase the cooling capacity of system 100 when needed under peak load conditions. In other words, system 100 including PCM heat exchanger 150 can, in this embodiment, absorb more thermal energy from portions of a vehicle, such as the aircraft cockpit 130 and avionics compartment 140, compared to a similar system including only E-ACM 110 without PCM heat exchanger 150.

[0042] The PCM heat exchanger 150 in this embodiment is a closed system, meaning that the PCM heat exchanger 150 contains a quantity of phase change material sealed within the PCM heat exchanger 150. In another embodiment, the PCM heat exchanger 150 may be designed to operate as an open system, meaning that some or all of the phase change material can escape from the PCM heat exchanger 150 during operation of the system 100. As a result, because the amount of phase change material in the PCM heat exchanger 150 decreases over time, the PCM heat exchanger 150 may be configured so that the phase change material can be periodically replenished as needed, for example, by opening the housing of the PCM heat exchanger 150 and filling the PCM heat exchanger 150 with more phase change material.

[0043] In this embodiment, the system includes a controller 160 configured to control the extent to which PCM heat exchanger 150 further reduces the temperature of the cooling air depending on the load on the system. In other words, controller 160 can control the rate at which thermal energy from air flowing along airflow path 120 is absorbed by PCM heat exchanger 150. This control function of controller 160 may be implemented via any suitable mechanism, an example of which is described below with reference to FIG. 5.

[0044] One advantage of actively controlling the rate at which PCM heat exchanger 150 absorbs thermal energy is that PCM heat exchanger 150 can be used to absorb excess energy only under peak load conditions. In this way, controller 160 can ensure that the phase change material remains relatively cool at other times, and therefore can absorb greater amounts of energy when peak load conditions occur.

[0045] To this end, controller 160 may be configured to monitor one or more variable parameters indicative of the current load of system 100 and control the extent to which PCM heat exchanger 150 further reduces the temperature of the cooling air in response to the monitored one or more parameters. In this embodiment, system 100 includes first, second, third, and fourth temperature sensors 162, 164, 166, and 168, and controller 160 is configured to receive first, second, third, and fourth temperature information indicative of the temperatures measured by first, second, third, and fourth temperature sensors 162, 164, 166, and 168, respectively. As described below, the controller can use this information to determine when and how to adjust the rate at which thermal energy is absorbed by PCM heat exchanger 150. As will become apparent from the description below, in some embodiments, one or more of first, second, third, and fourth temperature sensors 162, 164, 166, and 168 may be omitted. Furthermore, in some embodiments, the controller 160 may not receive such temperature information, in which case the system 100 may not include a temperature sensor.

[0046] 1 , in this embodiment, first temperature sensor 162 is configured to measure a temperature at a first point along airflow path 120 upstream of a portion of the vehicle that is cooled using the flow of cooling air provided by E-ACM 110, which in this embodiment includes cockpit 130 and one or more avionics compartments 140. Controller 160 receives first temperature information from first temperature sensor 162 that is indicative of the temperature measured at the first point.

[0047] Second temperature sensor 164 is configured to measure the temperature at a second point along airflow path 120 downstream of the portion of the vehicle that is cooled using the flow of cooling air provided by E-ACM 110, which in this embodiment includes cockpit 130 and one or more avionics compartments 140. Controller 160 receives second temperature information from second temperature sensor 164 that is indicative of the temperature measured at the second point.

[0048] Third temperature sensor 166 is configured to measure the temperature at a third point along airflow path 120, and fourth temperature sensor 168 is configured to measure the temperature at a fourth point along airflow path 120. The third and fourth points are both upstream of one or more avionics compartments 140 and downstream of cockpit 130. The third point is a point between cockpit 130 and PCM heat exchanger 150, i.e., a point upstream of PCM heat exchanger 150. The fourth point is a point between PCM heat exchanger 150 and one or more avionics compartments 140, i.e., a point downstream of PCM heat exchanger 150.

[0049] The controller 160 receives third temperature information from the third temperature sensor 166, which indicates the temperature measured at the third point. The controller 160 also receives fourth temperature information from the fourth temperature sensor 166, which indicates the temperature measured at the fourth point.

[0050] Controller 160 can use the first, second, third, and fourth temperature information to calculate temperature differences, or "deltas," across various portions of system 100 and control the rate at which thermal energy is absorbed by PCM heat exchanger 150 in response to the calculated temperature differences. The temperature difference across a portion of system 100, for example, a portion of the vehicle such as cockpit 130 or avionics compartment 140, or a portion of the cooling system such as PCM heat exchanger 150, indicates a load on the system associated with that portion of the system.

[0051] In some embodiments, controller 160 can control the degree to which energy is absorbed by PCM heat exchanger 150 in response to the difference between a first temperature and a second temperature, which is indicative of the total load on systems associated with both cockpit 130 and one or more avionics compartments 140. For example, controller 160 can use the first and second temperature information to detect when the temperature difference across cockpit 130, PCM heat exchanger 150, and one or more avionics compartments 140 exceeds a first threshold and respond by increasing the rate at which energy is absorbed by PCM heat exchanger 150. The first threshold may be set to a value of the temperature difference expected to occur under certain load conditions, for example, peak load conditions that the vehicle may be expected to experience during normal operation.

[0052] In some embodiments, the controller 160 can use temperature measurements, such as the first, second, third, and / or fourth temperature information, to determine when to increase the flow of air through the PCM heat exchanger 150 to cool the phase change material. This process, sometimes referred to as “priming” the PCM heat exchanger 150, occurs when the phase change material is at a higher temperature than the temperature of the air flowing through the PCM heat exchanger 150. For example, in a scenario where the phase change material in the PCM heat exchanger 150 was previously used to absorb heat from the air flowing around the air flow path 120, thereby providing additional cooling, some or all of the phase change material may change state (e.g., from solid to liquid) and, as a result, may not be able to efficiently absorb more heat. By cooling the phase change material back to its original state, e.g., from liquid back to solid, the controller 160 can prime the PCM heat exchanger 150 so that it can more effectively cool the air the next time additional cooling is needed (e.g., during a subsequent peak load event). In some such embodiments, PCM heat exchanger 150 can include a sensor positioned to provide PCM temperature information indicative of a current temperature of the phase change material, and controller 160 can determine, based on the PCM temperature information, to increase the rate of airflow through PCM heat exchanger 150. For example, controller 160 can compare the PCM temperature information with third temperature information to determine whether the temperature of the air exiting cockpit 130 is lower than the current temperature of the phase change material, and can increase the rate of airflow through PCM heat exchanger 150 in response to determining that the temperature of the air exiting cockpit 130 is lower than the current temperature of the phase change material.

[0053] In this embodiment, the system is configured to supply cooled air to multiple portions of the vehicle, specifically a first portion (cockpit 130) and a second portion (one or more avionics compartments 140). In such an embodiment, controller 160 may be configured to receive third and / or fourth temperature information in addition to the first and / or second temperature information, allowing controller 160 to calculate individual temperature differences across each of the portions 130, 140 to which cooled air is supplied. In some such embodiments, one of third and fourth temperature sensors 166, 168 may be omitted, based on the fact that the temperature at the third point may be very close to or even identical to the temperature measured at the fourth point when PCM heat exchanger 150 is absorbing little or no energy. However, measuring the temperature separately at both the third and fourth points has the advantage that the controller 160 can still determine the exact temperature delta of each of the cockpit 130 and one or more avionics compartments 140 when the PCM heat exchanger 150 is absorbing energy from the air flowing along the airflow path 120 to create a measurable temperature difference across the PCM heat exchanger 150.

[0054] Controller 160 may utilize the received temperature information, such as the first, second, third, and fourth temperature information, in various ways. By way of example, in some embodiments, controller 160 may use the received temperature information to calculate one or more temperature differences, or deltas, across portions of the system as described above and adjust the rate at which heat is absorbed by the PCM-HE in response to the measured temperature differences. In some embodiments, controller 160 is configured to determine a first load associated with a first portion of the vehicle (e.g., cockpit 130) based on the first and third temperature information, determine a second load associated with a second portion of the vehicle (e.g., one or more avionics compartments 140) based on the second and third temperature information, and determine a load on the system based on the determined first and second loads.

[0055] In another embodiment, the temperature information may be used as input to a predetermined control algorithm, for example, an artificial intelligence (AI) algorithm trained to map multiple input temperature measurements to one or more outputs for use in controlling a mechanism that regulates the rate at which energy is absorbed by PCM heat exchanger 150. In this approach, the received temperature information may be used by controller 160 without explicitly calculating a temperature delta. As a further example, in some embodiments, one or more temperature measurements may be compared to corresponding setpoint values ​​and used as input to an appropriate control algorithm, for example, a proportional-integral-derivative (PID) algorithm.

[0056] 1, in which controller 160 actively controls the degree of cooling provided by PCM heat exchanger 150 depending on received temperature information. In some embodiments, controller 160 can take other information into account instead of or in addition to temperature information when controlling the degree of cooling provided by PCM heat exchanger 150. For example, in one such embodiment, controller 160 is configured to receive power information indicative of a level of power currently being supplied to one or more electronic components of the vehicle, such as avionics components housed within one or more avionics compartments 140. For example, as shown in FIG. 1, controller 160 may be communicatively linked to the electrical power systems of one or more avionics compartments 140 to receive the power information. Controller 160 may control the extent to which PCM heat exchanger 160 further reduces the temperature of the cooling air in response to the received power information, for example, by increasing the rate at which PCM heat exchanger 160 absorbs energy from the cooling air in response to an increase in the level of power supplied to one or more electronic components as indicated by the power information.

[0057] 1, in which the controller 160 actively controls the degree of cooling provided by the PCM heat exchanger 150, or in other words, the rate at which energy is absorbed by the PCM heat exchanger 150. However, in other embodiments of the invention, the system may be configured such that the PCM heat exchanger operates passively, meaning that the phase change material naturally absorbs heat from the air flowing through the PCM heat exchanger without any mechanism for controlling the rate at which heat is absorbed by the phase change material.

[0058] In the embodiment shown in FIG. 1 , airflow path 120 is configured to pass cooled air from E-ACM 110 through a first portion of the vehicle, in this case cockpit 130, to a second portion of the vehicle, in this case one or more avionics compartments 140, and PCM heat exchanger 150 is disposed along airflow path 120 between first portion 130 and second portion 140. In this manner, PCM heat exchanger 150 cools the air received from first portion 130 before it reaches second portion 140. This arrangement may be particularly advantageous when there is a requirement that the cooled air entering second portion 140 not exceed a second threshold temperature. That is, if the load on first portion 130 of the vehicle increases significantly and the air exiting first portion 130 exceeds the second threshold, the additional cooling provided by PCM heat exchanger 150 can return the temperature of the air on airflow path 120 to below the second threshold before the air reaches second portion 140 of the vehicle.

[0059] In this embodiment, the system 100 further includes a cockpit bypass flowpath 122 configured to allow at least a portion of the cooled air from the E-ACM 110 to bypass the cockpit 130. In this manner, at least a portion of the cooled air can flow from the E-ACM 110 to one or more avionics compartments 140 without passing through the cockpit 130. As shown in FIG. 1 , the air traveling along the cockpit bypass flowpath 122 mixes with air exiting the cockpit 130 before traveling onward through the PCM heat exchanger 150 and then to the one or more avionics compartments 140. This can provide an additional mechanism to help maintain the temperature of the air supplied to the one or more avionics compartments 140 below a second threshold. In some embodiments, the cockpit bypass flowpath 122 may be omitted, such that all air traveling along the air flowpath 120 must pass through the cockpit 130.

[0060] Depending on the embodiment, system 100 may include a mechanism for adjusting the relative flow rates of air through cockpit 130 and cockpit bypass flowpath 122, or the relative flow rates may be fixed (i.e., not adjustable). In embodiments in which a mechanism for adjusting the relative flow rates is provided, controller 160 may control the mechanism to maintain the temperature of the air at the fourth point below the second threshold by increasing or decreasing the flow rate through cockpit bypass flowpath 122 as needed.

[0061] In general, in embodiments of the present invention, a PCM heat exchanger may be used in any system in which cooled air from an ACM is supplied to one or more portions of a vehicle to provide additional cooling capacity in addition to that provided by the ACM. In the embodiment shown in FIG. 1 , the PCM heat exchanger 150 is located between the cockpit 130 and one or more avionics compartments 140 to provide additional cooling to the cooled airflow after it passes through the cockpit 130 and before it passes through the one or more avionics compartments 140. However, in other embodiments, the PCM heat exchanger 150 may be located at a different point in the system so that the PCM heat exchanger 150 is still effective in providing additional cooling in addition to that provided by the ACM. Examples of other such embodiments are shown in FIGS. 2, 3, and 4.

[0062] Similar to system 100 of FIG. 1, systems 200, 300, 400 shown in FIGS. 2, 3, and 4 each include an E-ACM 210, 310, 410, an airflow path 220, 320, 420 configured to supply cooling air from the E-ACM 210, 310, 410 to one or more avionics compartments 240, 340, 440 via a cockpit 230, 330, 430, a PCM heat exchanger 250, 350, 452, 454, 456 configured to provide additional cooling in addition to the cooling provided by the E-ACM 210, 310, 410, and a controller 260, 360 configured to adjust the rate at which energy is absorbed by the PCM heat exchanger 250, 350, 452, 454, 456. The E-ACMs 210, 310, 410 each include an air compression stage 212, 312, 412, a heat exchange stage 214, 314, 414, an air expansion stage 216, 316, 416, and an electric motor 218, 318, 418. The systems 200, 300, 400 also each include a cockpit bypass flowpath 222, 322, 422 configured to allow at least a portion of the cooling air from the E-ACMs 210, 310, 410 to bypass the cockpit 230, 330, 430.

[0063] The function of each of these portions in systems 200, 300, 400 is similar to the function of the corresponding portion in system 100 of Figure 1, and for the sake of brevity, a detailed description will not be repeated here. It will be understood that the system shown in Figure 4 also includes a controller similar to controller 160 described above with reference to Figure 1, but that for the sake of clarity, the controller is not shown in Figure 4.

[0064] 2 differs from system 100 of FIG. 1 in that PCM heat exchanger 250 is positioned to cool the airflow passing from E-ACM 210 to cockpit 230. In other words, PCM heat exchanger 250 is positioned upstream of cockpit 230 along airflow path 220. An advantage of this positioning is that the temperature of the air supplied to cockpit 230 can be further reduced, which can be particularly advantageous when the vehicle is operating at high ambient temperatures.

[0065] System 300 of FIG. 3 differs from system 100 of FIG. 1 in that a PCM heat exchanger 350 is connected between air compression stage 312 of E-ACM 310 and air expansion stage 316 of E-ACM 310 to further cool the compressed air stream before it reaches air expansion stage 316. Depending on the embodiment, PCM heat exchanger 350 may be connected upstream of heat exchange stage 314 of E-ACM 310 or downstream of heat exchange stage 314 of E-ACM 310. In effect, in this configuration, PCM heat exchanger 350 acts to supplement heat exchange stage 314 of E-ACM 310. Thus, PCM heat exchanger 350 serves to further reduce the temperature of the compressed air supplied to air expansion stage 316 of E-ACM 310, thereby further reducing the temperature of the cooled air stream exiting air expansion stage 316.

[0066] System 400 of FIG. 4 differs from system 100 of FIG. 1 in that system 400 includes first, second, and third PCM heat exchangers 452, 454, 456. First PCM heat exchanger 452 is located in a similar position to that shown in FIG. 1 and functions in a similar manner to PCM heat exchanger 150 of FIG. 1. Second PCM heat exchanger 454 is located in a similar position to that shown in FIG. 2 and functions in a similar manner to PCM heat exchanger 250 of FIG. 2. Third PCM heat exchanger 456 is located in a similar position to that shown in FIG. 3 and functions in a similar manner to PCM heat exchanger 350 of FIG. 3. In some embodiments similar to the embodiment shown in FIG. 4, one of first, second, and third PCM heat exchangers 452, 454, 456 may be omitted, such that the system includes only two PCM heat exchangers. In other embodiments, more than three PCM heat exchangers can be provided in a single system, for example, by connecting additional PCM heat exchangers in series or parallel with any of the first, second, and third PCM heat exchangers 452, 454, 456 shown in FIG. 4.

[0067] Referring now to Figure 5, a system including a mechanism for controlling the degree of cooling provided by a PCM heat exchanger is illustrated, according to one embodiment of the present invention. As indicated by the reference numerals in Figure 5, the mechanism may be used to control the degree of cooling provided by any of the PCM heat exchangers 150, 250, 350, 452, 454, 456 of the systems 100, 200, 300, 400 described above with reference to Figures 1-4, and may be controlled by the respective controllers 160, 260, 360.

[0068] The system includes a PCM heat exchanger bypass flow path 522 configured to allow at least a portion of the air flowing along the air flow path 120, 220, 320, 420 to bypass the PCM heat exchangers 150, 250, 350, 452, 454, 456. The system further includes a flow control mechanism 524, e.g., a valve, operable to control the flow rate of air along the PCM heat exchanger bypass flow path 522 relative to the flow rate of air through the PCM heat exchangers 150, 250, 350, 452, 454, 456. The controller 160, 260, 360 is configured to control the flow control mechanism 524 in response to a load on the system, e.g., by opening or closing a valve, to control the extent to which the PCM heat exchangers 150, 250, 350, 452, 454, 456 further reduce the temperature of the cooling air flowing along the air flow path 120, 220, 320, 420. In addition to allowing the controller 160, 260, 360 to dynamically adjust the degree of cooling provided by the PCM heat exchanger 150, 250, 350, 452, 454, 456, the combination of the PCM heat exchanger bypass flow path 522 and flow control mechanism 524 allows the airflow along the air flow path 120, 220, 320, 420 to bypass the PCM heat exchanger 150, 250, 350, 452, 454, 456 when additional cooling is not needed, thereby avoiding the pressure drop that might otherwise occur when the airflow is directed through the PCM heat exchanger 150, 250, 350, 452, 454, 456.

[0069] In the embodiment of FIG. 5, the mechanism for controlling the degree of cooling provided by the PCM heat exchanger comprises a PCM heat exchanger bypass flow path 522 in combination with a flow control mechanism 524 . In other embodiments, different mechanisms may be provided to control the degree of cooling provided by the PCM heat exchanger. For example, in some embodiments, a mechanism may be configured to physically move the PCM heat exchanger into or out of the airflow path. For example, in one such embodiment, a mechanism may be configured to rotate, slide, or otherwise move the PCM heat exchanger out of the airflow path when it is not needed. Depending on the implementation, the mechanism may further be configured to replace the PCM heat exchanger with an appropriate length of duct or similar component, as needed, to fill the gap in the airflow path where the PCM heat exchanger was previously located. The mechanism may be controlled to return the PCM heat exchanger to the airflow path when additional cooling is needed.

[0070] Referring now to FIG. 6, a flowchart illustrating a method for providing cooled air within a vehicle according to one embodiment of the present invention is illustrated. The method corresponds to the method for operating any of the systems described above with reference to FIGS. 1 through 5. First, in step 602, an ACM is used to generate a flow of cooled air. Then, in step 604, the cooled air is directed from an air expansion stage of the ACM around an air flow path from the ACM to one or more portions of the vehicle. In step 606, in addition to the cooling provided by the ACM, a PCM heat exchanger is used to further cool the air before it reaches at least one of the one or more portions of the vehicle. It will be appreciated that because the ACM can operate continuously, in practice, steps 602, 604, and 606 may be performed simultaneously for different portions of the air flow within the system.

[0071] Referring now to FIG. 7, a cross-sectional view of a PCM heat exchanger according to one embodiment of the present invention is shown. The PCM heat exchanger illustrated in FIG. 7 may be used as the PCM heat exchangers 150, 250, 350, 452, 454, and 456 of the previously described embodiments. In this embodiment, the PCM heat exchanger is configured similarly to a plate-fin heat exchanger and includes a housing 752 through which air can flow from one end of the PCM heat exchanger to the other, and multiple plates disposed within the housing 752. The housing 752 may be configured to connect to the air flow paths 120, 220, 320, and 420 at either end. For example, the housing 752 may be configured to have a size and shape similar to the ducts used in the air flow paths 120, 220, 320, and 420, facilitating installation of the PCM heat exchanger 150, 250, 350, 452, 454, and 456 in series with the air flow paths 120, 220, 320, and 420. Although FIG. 7 shows the housing having a circular cross-section, it should be understood that in other embodiments the housing may have a cross-section of any shape, for example a square or rectangular cross-section.

[0072] The plates divide the space within the housing 752 into one or more airflow sections and one or more phase change material sections 754, 756, 758, with each phase change material section 754, 756, 758 containing a quantity of phase change material. In the embodiment shown in Figure 7, cross-hatching is used to illustrate the phase change material sections 754, 756, 758, with the spaces between the phase change material sections 754, 756, 758 comprising airflow sections through which air can pass.

[0073] The plates may be non-planar, having surface features such as corrugations as shown in Figure 7, and / or fins or other protrusions, to increase the surface area in contact with the air flowing through the airflow section. In this way, the efficiency of heat transfer from the air to the phase change material may be increased.

[0074] It should be understood that the PCM heat exchanger illustrated in Figure 7 is merely one example of a manager in which the PCM heat exchangers 150, 250, 350, 452, 454, 456 may be implemented, and that in other embodiments, the PCM heat exchangers 150, 250, 350, 452, 454, 456 may be configured differently than that shown in Figure 7. For example, in some embodiments, the phase change material may be provided in the form of a partial or complete layer disposed around the outside of the housing such that, when viewed in cross section, the phase change material forms a partial or complete ring around the housing.

[0075] Although particular embodiments of the invention have been described herein with reference to the drawings, it will be understood that many variations and modifications can be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. 1. A system for providing cooling air within a vehicle, comprising: an air cycle machine (ACM) comprising: an air compression stage arranged to receive and compress a flow of air to produce a flow of compressed air; a heat exchange stage arranged to cool the compressed air; and an air expansion stage arranged to expand the air received from the heat exchange stage to output a flow of cooled air having a temperature that is lower than a temperature of the air received by the air compression stage; an air flow path configured to direct the cooled air from the ACM to one or more portions of the vehicle; and a phase change material (PCM) heat exchanger positioned to further cool the air before it reaches at least one of the one or more portions of the vehicle in addition to the cooling provided by the ACM.

2. The system of claim 1 , comprising a controller configured to control the extent to which the PCM heat exchanger further reduces the temperature of the cooling air depending on a load on the system.

3. a first bypass flow path configured to allow at least a portion of the air flowing along the air flow path to bypass the PCM heat exchanger; a flow control mechanism operable to control the flow rate of air along the first bypass flow path relative to the flow rate of air passing through the PCM heat exchanger; 3. The system of claim 2, wherein the controller is configured to control the flow control mechanism in response to a load on the system to control the extent to which the PCM heat exchanger further reduces the temperature of the cooled air before it reaches at least a portion of the vehicle.

4. the controller is configured to receive first temperature information indicative of a first temperature of the air at a first point along the air flow path upstream of at least a portion of the vehicle and second temperature information indicative of a second temperature of the air at a second point along the air flow path downstream of at least a portion of the vehicle, a difference between the first temperature and the second temperature indicative of a load on the system associated with at least a portion of the vehicle; 4. The system of claim 2 or 3, wherein the controller is configured to control the extent to which the PCM heat exchanger further reduces the temperature of the cooling air in response to the first temperature information and the second temperature information.

5. the one or more portions of the vehicle include at least a first portion and a second portion, and the air flow path is configured to pass the cooled air from the ACM through the first portion to the second portion; wherein the first point along the air flow path is a point upstream of the first portion and the second point along the air flow path is a point downstream of the second portion, the controller is configured to receive third temperature information indicative of a third temperature of the air at a third point along the air flow path between the first portion and the second portion, a difference between the first temperature and the third temperature indicative of a load on the system associated with the first portion of the vehicle, and a difference between the second temperature and the third temperature indicative of a load on the system associated with the second portion of the vehicle; 5. The system of claim 4, wherein the controller is configured to control the extent to which the PCM heat exchanger further reduces the temperature of the cooling air in response to the third temperature information in addition to the first temperature information and the second temperature information.

6. 6. The system of claim 5, wherein the controller is configured to determine a first load associated with the first portion of the vehicle based on the first and third temperature information, determine a second load associated with the second portion of the vehicle based on the second and third temperature information, and determine the load on the system based on the determined first and second loads.

7. the one or more portions of the vehicle include at least a first portion and a second portion, and the air flow path is configured to pass the cooled air from the ACM through the first portion to the second portion; 5. The system of claim 4, wherein the first point along the air flow path is a point upstream of the first portion, and a difference between the first temperature and the second temperature indicates a total load on the system associated with both the first portion and the second portion of the vehicle.

8. 8. The system of claim 2, wherein the one or more portions of the vehicle comprise one or more electronic components, and the controller is configured to receive power information indicative of a level of power currently supplied to the one or more electronic components, and to control the extent to which the PCM heat exchanger further reduces the temperature of the cooling air in response to the received power information.

9. 9. The system of claim 2, wherein the controller is configured to increase a flow rate of airflow through the PCM heat exchanger to cool a phase change material of the PCM heat exchanger.

10. 10. The system of any one of claims 1 to 9, wherein the one or more portions of the vehicle comprise at least a first portion and a second portion, and the air flow path is configured such that the cooled air passes from the ACM through the first portion to the second portion, and wherein the PCM heat exchanger is positioned along the air flow path between the first portion and the second portion to cool the air received from the first portion before it reaches the second portion.

11. 10. The system of claim 1, wherein the PCM heat exchanger is positioned along the air flow path between the ACM and the one or more portions of the vehicle to further cool the cooled air flow from the ACM before the cooled air flow reaches the one or more portions.

12. 10. The system of claim 1, wherein the PCM heat exchanger is connected between the air compression stage of the ACM and the air expansion stage of the ACM to further cool the compressed air flow before it reaches the air expansion stage.

13. the one or more portions of the vehicle include at least a first portion and a second portion, the air flow path is configured to pass the cooled air from the ACM through the first portion to the second portion, and the PCM heat exchanger is a first PCM heat exchanger disposed along the air flow path between the first portion and the second portion to cool the air received from the first portion before the air reaches the second portion; or a second PCM heat exchanger disposed along the air flow path between the ACM and the first portion to further cool the cooled air flow from the ACM before it reaches the first portion; or a third PCM heat exchanger connected between the air compression stage of the ACM and the air expansion stage of the ACM to further cool the compressed air stream before it reaches the air expansion stage; 10. The system of claim 1, wherein the system further comprises at least one other heat exchanger among the first, second, and third heat exchangers.

14. the one or more portions of the vehicle include at least a first portion and a second portion, the air flow path is configured to pass the cooled air from the ACM through the first portion to the second portion, and the system comprises:

14. The system of claim 1, comprising a second bypass flow path configured to allow at least a portion of the cooling air from the ACM to bypass the first portion such that at least a portion of the cooling air can flow from the ACM to the second portion without passing through the first portion.

15. 15. The system of claim 1, wherein the air flow path is a recirculation air flow path configured to return air from the one or more portions of the vehicle to the air compression stage of the ACM to recirculate air within the vehicle.

16. The system according to any one of claims 1 to 15, wherein the air cycle machine is an electric air cycle machine (E-ACM).

17. The system of claim 16 when dependent on claim 15, wherein the E-ACM is a closed-loop E-ACM.

18. A vehicle comprising a system according to any one of claims 1 to 17.

19. 20. The vehicle of claim 18, wherein the vehicle is an aircraft.

20. The one or more portions of the vehicle include at least: The cockpit and 20. The vehicle of claim 19, further comprising one or more avionics compartments housing one or more avionics components.

21. 21. The vehicle of claim 20 when dependent on any of claims 5, 6, 7, 10, 13, and 14, wherein the first portion of the vehicle comprises the cockpit and the second portion of the vehicle comprises the one or more avionics compartments.

22. 1. A method for providing cooling air within a vehicle, comprising: using an air cycle machine (ACM) to generate a flow of cooled air, the ACM comprising: an air compression stage arranged to compress air to generate a flow of compressed air; a heat exchange stage arranged to cool the compressed air; and an air expansion stage arranged to expand air received from the heat exchange stage to output the flow of cooled air having a temperature that is lower than a temperature of the air received by the air compression stage; directing the cooling air from the air expansion stage of the ACM around an air flow path from the ACM to one or more portions of the vehicle; In addition to the cooling provided by the ACM, using a phase change material (PCM) heat exchanger to further cool the air before it reaches at least one of the one or more portions of the vehicle.

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