Power supply system for a propulsion system of an aircraft
Patent Information
- Application Number
- EP2023798343
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-11-03
- Filing Date
- 2023-10-23
- Publication Date
- 2025-09-10
AI Technical Summary
Existing energy supply systems for aircraft propulsion systems, particularly those using fuel cell units, face challenges in efficiently managing temperature fluctuations and cooling capacity during changes in load, which can impact the safe and optimized operation of fuel cells.
The energy supply system incorporates a second heat source with a lower optimal operating temperature connected to a fuel cell unit in a common cooling circuit, allowing for recirculation of cooling fluid to maintain optimal temperatures and quickly access stored cooling capacity, especially during load changes, by using a controllable valve and heat exchanger with an actuable inlet.
This configuration ensures the fuel cell unit operates within a safe temperature range, providing rapid access to increased cooling capacity when needed, enhancing power output and operational safety, particularly during landing and start procedures.
Smart Images
Figure 1.1
Abstract
Description
[0001] Energy supply system for an aircraft propulsion system
[0002] DESCRIPTION
[0003] Technical area
[0004] The present invention relates to an energy supply system for a propulsion system of an aircraft.
[0005] State of the art
[0006] The aircraft can, in particular, be a propeller aircraft, whereby the kinetic energy used to generate propulsion can at least be provided in part by an electric motor. The present subject matter is directed to a system intended to supply energy to such an aircraft, which system has a fuel cell unit to deliver electrical power. This system can comprise a fuel cell stack, also referred to as a stack, in which a plurality of plate-shaped fuel cells are arranged next to one another in a stacking direction and thus connected in series. During operation, reaction gases, e.g., water and (atmospheric) oxygen, can flow through the fuel cell stack, thereby delivering electrical power. This is intended to illustrate an advantageous application environment, but does not initially limit the subject matter in its generality.
[0007] Description of the invention
[0008] The present invention is based on the technical problem of providing an advantageous energy supply system.
[0009] This is achieved according to the invention with the energy supply system according to claim 1. This system comprises, in addition to the fuel cell unit (= first heat source), a second heat source, wherein the heat sources are connected in a common cooling circuit with a heat exchanger. A first optimal operating temperature T op ti of the first heat source (fuel cell unit) is above a second optimal operating temperature T opt 2 of the second heat source, and in addition, a recirculation circuit is assigned to the first heat source (fuel cell unit). Through this circuit, a cooling fluid that has already been used to cool the first heat source (fuel cell unit) in a respective pass can be or is used again, at least in part, to cool the first heat source before passing through the heat exchanger.
[0010] The cooling circuit can thus be operated at a temperature below the optimal temperature for the operation of the fuel cell unit (T op ti), whereby a slightly higher temperature can be set locally for the fuel cell unit through recirculation (the first optimal operating temperature T opti accordingly). In this case, cooling capacity is "stored" in the cooling circuit with respect to the fuel cell unit, which can be called up in particular at relatively short notice. If, for example, there is a load change, i.e. if the fuel cell unit delivers more electrical power and, conversely, needs to be cooled more effectively, the proportion recirculated during normal operation can be reduced, for example in the system according to the invention, and the cooling capacity for the fuel cell unit can be increased accordingly. Since this cooling capacity is already present in the system or circuit, i.e. does not have to be "generated" by, for example, adapted operation of the heat exchanger, it can be available relatively quickly. This can be particularly advantageous with regard to fuel cells, for example by helping to ensure their safe operation and / or operation that is optimized with regard to power output.
[0011] Preferred embodiments can be found in the dependent claims and the entire disclosure, whereby the presentation of the features does not always distinguish in detail between device and method or use aspects; in any case, the disclosure is to be read implicitly with regard to all claim categories. If, for example, the advantages of the energy supply system in a certain operating mode are described, this is to be understood at the same time as a disclosure of a corresponding operating method, just as the description of a certain operating mode is to be read as a reference to an energy supply system set up for this purpose. In the cooling circuit, the heat sources and the heat exchanger are connected to one another, e.g. the heat sources are connected to the heat exchanger in series. Relative to one another, the heat sources can, however, be arranged, for example,can also be arranged in parallel. Irrespective of these details, within the scope of the present disclosure, the "interconnected" or "connected" refers to a corresponding fluidic connection (piping) through which the cooling fluid can flow during operation. Due to the circuit architecture, the cooling system as a whole is designed for repeated flow through the individual components with the same cooling fluid, which is why, according to the main claim, reference is made to the passage through the heat exchanger after cooling the first heat source.
[0012] During operation, the cooling fluid can, of course, flow continuously through the entire system; however, if one considers a single volume element, this will repeatedly pass through the heat exchanger and the first and / or second heat source (depending on the recirculated portion, also the first heat source several times). Generally, specifications regarding the relative positioning of the individual components in the cooling circuit, i.e., "upstream" and "downstream," refer to the flow direction of the cooling fluid during operation. Thus, an "upstream" component is flowed through by a respective volume unit of cooling fluid before a "downstream" component.
[0013] For example, the cooling circuit may also contain a reservoir in which cooling fluid can be collected and stored for subsequent circulation. Generally, "a" and "an" are to be read as indefinite articles throughout this disclosure unless expressly stated otherwise, and thus always as "at least one" or "at least one," respectively. Thus, the cooling circuit may also contain, for example, more than one heat exchanger and / or more than two heat sources.
[0014] In detail, a first cooling section of the cooling circuit is assigned to the first heat source, wherein this first cooling section can generally also be provided as an external cooling element relative to the first heat source. While this can functionally dissipate heat from the fuel cell unit, e.g., due to a thermally conductive system, it is not further integrated with it. In a preferred embodiment, however, the first cooling section extends through the fuel cell unit, in particular through a channel structure defined by the fuel cells. In detail, a respective fuel cell can, for example, have a so-called bipolar plate, which defines a channel structure for the cooling fluid (and typically also for the reaction gas(es).
[0015] Regardless of whether the first cooling section is external or integrated, the recirculation circuit connects an outlet of the first cooling section to an inlet thereof. This can generally offer advantages even in a static arrangement, regardless of any adjustment of the recirculated portion, because it allows two different temperatures to be achieved in the same cooling circuit. However, a controllable valve is preferably provided in the recirculation circuit, with which the recirculated portion can be adjusted. The energy supply system can then, for example, have a controller configured to control the controllable valve accordingly to change the recirculated portion depending on the operating state (normal operation, etc., see below for details).
[0016] According to a preferred embodiment, the second heat source comprises or is an electronic control unit, preferably a motor control unit of an electric motor of the drive. A semiconductor-based electronic control unit can have a lower optimal operating temperature than the fuel cell unit and thus permit the above-described mode of operation with a cooling circuit that is "subcooled" compared to the fuel cell unit. Alternatively, the second heat source can generally also be, for example, a voltage converter or an electric motor, such as the propulsion-generating engine itself or an auxiliary motor of the power supply or general on-board system of the aircraft, such as a compressor motor.
[0017] In general, the heat exchanger can be used to extract thermal energy from the cooling fluid, which is then dissipated via an external material or fluid flow. The ambient air flowing past during operation, i.e., during flight, preferably feeds the external fluid flow; it can be "collected," for example, on the fuselage of the aircraft or on or in the propulsion unit. The heat exchanger has an actuatable inlet, meaning that the external fluid flow fed into the heat exchanger for heat dissipation can be adjusted, i.e., throttled or increased as needed. This can be achieved, for example, with a flap, aperture, or an adjustable inlet grille. Regardless of these details, the actuatable inlet can allow advantageous operation in that the inlet is opened during a landing maneuver, which results in increased cooling performance and, at the same time, greater air resistance.
[0018] In other words, at least part of the kinetic energy is converted into cooling power, whereby by increasing the portion conducted through the recirculation circuit, the temperature of the fuel cell unit can nevertheless be kept within an adequate range, thus avoiding a temperature drop identical to that of the cooling circuit. For a semiconductor-based control unit, the optimal operating temperature (T opt2) may be higher than temporarily set in the cooling circuit, but the control unit can still be operated safely even at lower temperatures. As a result, the described cooling during the landing process maintains cold in the cooling circuit, which can generally be advantageous for a subsequent takeoff process, but especially with regard to a possible go-around maneuver. This is because more electrical power is temporarily drawn from the fuel cell unit, which, in turn, requires more cooling (more than during normal operation, e.g., under cruise conditions).
[0019] As already mentioned above, in a preferred embodiment, a reservoir for the cooling fluid is also provided in the cooling circuit, in which the cooling fluid can be collected and then recirculated. Preferably, the reservoir is located downstream of the first and / or second heat source and upstream of the heat exchanger in the cooling circuit.
[0020] According to a preferred embodiment, the first and second optimal operating temperatures differ by at least 5 K. In absolute values, the first optimal operating temperature can be, for example, approximately 70 °C and the second optimal operating temperature approximately 60 °C, e.g., each with a fluctuation range of + / - 3 °C, preferably + / - 2 °C. Independent of these details, possible upper limits of the difference between the optimal operating temperatures can be, for example, at most 20 K, 15 K, or 10 K.
[0021] According to a preferred embodiment, the energy supply system has a controller or control unit, which can be, for example, in the form of a microcontroller as a separate controller or functionally integrated into a higher-level computer system of the aircraft. Regardless of the specific implementation, commands for initiating a specific operation of the energy supply system are stored in the control unit. Using a corresponding command structure, the controller can be configured, in particular, to operate the first heat source at a first temperature Ti and the second heat source at a second temperature T2, which is lower than the first temperature.
[0022] Preferably, the first temperature essentially corresponds to the first optimal operating temperature, and the second temperature essentially corresponds to the second optimal operating temperature. The controller can adjust the first temperature, for example, by adjusting the recirculated portion, and / or the second temperature, for example, by controlling the heat exchanger. For this purpose, temperatures measured at one or more points in the cooling circuit can also be incorporated into the controller, meaning the controller can be connected to one or more temperature sensors.
[0023] The invention also relates to an aircraft with a power supply system disclosed herein, in particular an aircraft, for example a propeller aircraft. Its propulsion system, which may, for example, comprise at least one drive unit with an electric motor and a propeller, but is usually even multi-engined, such as a DO 228, is supplied with electrical power by the fuel cell unit of the power supply system.
[0024] The invention also relates to a method for operating a presently disclosed energy supply system or aircraft, wherein the first heat source is operated at a first temperature and the second heat source is operated at a second temperature. Preferably, as explained above with regard to the control, the first and second temperatures substantially correspond to the respective optimal operating temperature (e.g., with a deviation of at most + / -3 K or + / -2 K). Conversely, the optimal operating temperatures do not have to be reached exactly; even an approximation can allow adequate operation.
[0025] In a preferred embodiment, at least temporarily, i.e. at least in one operating state, a cooling fluid already used to cool the fuel cell unit is fed back to the first cooling section through the recirculation circuit, i.e. used to cool the fuel cell unit before it passes through the heat exchanger. As explained in detail above, this sets a higher temperature for the fuel cell unit than for the cooling circuit. Preferably, the recirculated portion is changed over time, i.e., it is greater in a first operating state than in a second operating state. The first operating state can, in particular, correspond to normal operation, e.g., flight at cruising altitude (cruise condition). The second operating state, on the other hand, can correspond to a takeoff or go-around maneuver, in which a higher electrical power and, consequently, more intensive cooling are temporarily required.
[0026] The heat exchanger has an actuatable inlet (see above), which is opened during a landing procedure. This allows cooling capacity to be "stored" in the cooling circuit; see the above comments for details.
[0027] The invention also relates to the use of a propulsion system of an aircraft, see above for possible details, together with a power supply system described here.
[0028] Short description of the drawings
[0029] In the following, the invention is explained in more detail using an exemplary embodiment, whereby the individual features within the scope of the independent claims can also be essential to the invention in other combinations and no distinction is made in detail between the different claim categories.
[0030] In detail,
[0031] Figure 1 shows a schematic representation of an energy supply system according to the invention;
[0032] Figure 2 shows a propulsion system of an aircraft together with an energy supply system according to Figure 1;
[0033] Figure 3 shows a schematic representation of an aircraft with a propulsion system according to Figure 2.
[0034] Preferred embodiment of the invention
[0035] Figure 1 shows an energy supply system 1 comprising a first heat source 11 and a second heat source 12, as well as a heat exchanger 13, which are connected to one another in a cooling circuit 14. In detail, the first heat source 11 is a fuel cell unit 21, and the second heat source 12 is a control unit 22, specifically an engine control unit 32; see Figure 2 for details. Furthermore, a reservoir 15 is provided in the cooling circuit 14, in which a cooling fluid 16 can be collected during operation before being recirculated through the cooling circuit 14. A flow direction 17 of the cooling circuit 14 is indicated by arrows.
[0036] In the heat exchanger 13, the cooling fluid 16 is cooled, thus heat is dissipated by an external fluid flow 18. An inlet 13.1 of the heat exchanger 13 is actuatable, thus allowing the flow of the external fluid flow 18 to be adjusted. Downstream of the heat exchanger 13, the first and second heat sources 11, 12 are cooled by the cooling fluid 16. The first heat source 11 has a first optimal operating temperature T op ti and the second heat source 12 a second optimal operating temperature T opt 2, which is lower than the first optimal operating temperature. A recirculation circuit 19 is assigned to the first heat source 11, through which a cooling fluid already used to cool the first heat source 11 can be partially recirculated through the first cooling section 14.1, thus being used again to cool the first heat source 11.
[0037] This allows a second temperature T2 to be set in the cooling circuit 14, which, for example, essentially corresponds to the second optimal operating temperature and is lower than the first optimal operating temperature. Due to the partial recirculation, a first temperature Ti can nevertheless be set for the first heat source 11, which is greater than the second temperature T2 and, for example, essentially corresponds to the first optimal operating temperature. The recirculated portion is preferably adjustable, for which purpose a controllable valve 20 can be provided in the recirculation circuit 19, which is controlled by a controller 5. For further operating details, in particular concerning the actuatable inlet 13.1 of the heat exchanger 13, reference is made to the introduction to the description.
[0038] Figure 2 shows the energy supply system 1 only schematically, but illustrates its connection to a drive system 40. This has an electric motor 41 that drives a propeller 42, with the electrical power P for this being provided by the fuel cell unit 21. This is constructed from several stacks 21.1-21.4, which in turn each contain a plurality of fuel cells (not shown in detail). Together with the motor control unit 32, which controls the electric motor 41, the fuel cell unit 21 forms the two heat sources 11, 12, which are linked to one another in the energy supply system 1 in the manner explained with reference to Figure 1.
[0039] Figure 3 shows a schematic plan view of an aircraft 50, specifically an airplane 51. The propulsion system 40 in this case comprises two engines 41.1, 41.2 with a respective propeller 42.1, 42.2, which in this example are arranged on the wings 55 of the aircraft 51. LIST OF REFERENCE SYMBOLS
[0040] Energy supply system 1
[0041] Control 5 first heat source 11 second heat source 12
[0042] Heat exchanger 13
[0043] Entrance 13.1
[0044] Cooling circuit 14 first cooling section 14.1
[0045] Reservoir 15
[0046] Cooling fluid 16
[0047] Flow direction 17
[0048] Fluid flow 18
[0049] Recirculation circuit 19
[0050] Fuel cell unit 21
[0051] Stacks 21.1-21.4
[0052] Control unit 22
[0053] Engine control unit 32
[0054] Drive system 40
[0055] Electric motor 41
[0056] Engines 41.1, 41.2
[0057] Propeller 42
[0058] Propellers 42.1, 42.2
[0059] Engine control unit 32
[0060] Aircraft 50
[0061] Airplane 51
[0062] Wing 55
Claims
CLAIMS Energy supply system (1) for a drive system (40) of an aircraft (50), comprising a first heat source (11) in the form of a fuel cell unit (21), a second heat source (12) and a heat exchanger (13), wherein the first and the second heat source (11, 12) and the heat exchanger (13) are connected to one another in a cooling circuit (14) for conducting a cooling fluid (16), and wherein the first heat source (11) has a first optimum operating temperature T op ti and the second heat source (12) has a second optimal operating temperature T op t 2 , where the first optimal operating temperature T op ti greater than the second optimal operating temperature T op t 2 is, T op t 1 > T opt 2, wherein the first heat source (11) in the cooling circuit (14) is assigned a recirculation circuit (19), through which cooling fluid (16) already used during operation to cool the first heat source (11) can be used again to cool the first heat source (11) before passing through the heat exchanger (13), and wherein the heat exchanger (13) has an actuatable inlet (13.1). Energy supply system (1) according to claim 1, wherein a first cooling section (14.1) of the cooling circuit (14) is assigned to the first heat source (11), wherein the first cooling section (14.1) passes through the fuel cell unit (21). Energy supply system (1) according to claim 1 or 2, wherein the second heat source (12) comprises an electronic control unit (22). Energy supply system (1) according to claim 3, wherein the electronic control unit (22) is a motor control unit (32) of an electric motor (41) which is connected to the fuel cell unit (21) for supplying electrical power P. Energy supply system (1) according to one of the preceding claims, comprising a reservoir (15) for the cooling fluid (16), which is arranged in the cooling circuit (14). Energy supply system (1) according to one of the preceding claims, wherein the first optimal operating temperature T op ti is at least 5 K higher than the second optimum operating temperature T opt 2. Energy supply system (1) according to one of the preceding claims, comprising a controller (5) which is configured to operate the first heat source (11) at a first temperature Ti and the second heat source (12) at a second temperature T2, where Ti is greater than T2, Ti > T2. Aircraft (50), in particular an airplane (51), comprising an energy supply system (1) according to one of the preceding claims. Method for operating an aircraft (50) according to claim 8, comprising an energy supply system (1) according to one of claims 1 to 7, in which the first heat source (11) is operated at a first temperature Ti and the second heat source (12) at a second temperature T2, where Ti is greater than T2, Ti > T2, and in which the actuatable inlet (13.1) is opened during a landing operation in order to accumulate cooling power in the energy supply system (1) before a new takeoff or go-around operation.
10. The method according to claim 9, wherein at least temporarily and at least partially a cooling fluid (16) already used for cooling the first heat source (11) is passed through the recirculation circuit (19) before passing through the heat exchanger (13) and is used again for cooling the first heat source (11).
11. The method according to claim 10, wherein a portion of the cooling fluid (16) recirculated through the recirculation circuit (19) is greater in a first operating state than in a second operating state.
12. The method according to claim 11, wherein the first operating state corresponds to a normal operation.
13. Use of a propulsion system (40) of an aircraft (50) with a Energy supply system (1) according to one of claims 1 to 7, in particular in a method according to one of claims 10 to 12.