Aircraft heat management system scheme based on model predictive control

Abstract

The invention discloses an aircraft heat management system scheme based on model predictive control, which is characterized in that on the basis of model prediction, existing fuel oil and coolant on an aircraft are used as aircraft heat sinks, airborne equipment and an electronic system are cooled, and meanwhile, the temperature of the fuel oil can also be increased; according to the method, fuel oil is controlled to sequentially pass through a liquid cooling system heat exchanger and a fuel oil-hydraulic oil heat exchanger for heat interaction, then the fuel oil is divided into a backflow part and a fuel supply part, the backflow part is controlled to directly flow back into a fuel oil tank, and the fuel supply part is controlled to enter an engine after entering a fuel oil-lubricating oil heat exchanger. And the fuel oil temperature is controlled by adjusting the flow of the backflow part, so that the fuel oil temperature is stabilized at an ideal temperature.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aircraft design, in particular to a kind of aircraft heat management system scheme based on model predictive control. BACKGROUND

[0002] With the continuous development of modern aviation technology, the performance of modern aircraft is also rapidly improved. However, with the significant improvement of aircraft performance, the aircraft is required to have higher maneuverability, thus causing the heat production of airborne equipment and various subsystems of the aircraft to also increase sharply. At the same time, the high performance required by modern aircraft causes the heat dissipation capacity of the aircraft skin to decrease, causing the average temperature of the entire cabin to rise sharply. Therefore, a comprehensive consideration is needed to design a set of aircraft heat management method for the heat dissipation and cooling requirements of aircraft subsystems and airborne equipment and the ability of aircraft fuel to improve combustion efficiency after preheating, so that the waste heat generated during flight can be efficiently utilized.

[0003] In order to meet the cooling requirements of the aircraft, three processing schemes are currently proposed: first, more ram air is extracted, and more engine power is introduced to introduce a large amount of ram air, which requires larger skin openings and more engine shaft power consumption; second, more cold sources are carried, which requires many disposable cold sources, and the carrying of cold sources increases the takeoff weight of the aircraft, resulting in an increase in energy consumption per mile of the aircraft; third, use the existing fluid in the aircraft as a heat sink, use the existing fuel and coolant on the aircraft, and the onboard low-temperature fuel needs to be preheated before entering the engine. The heat source is distributed relatively scattered on the aircraft, and much of the waste heat is discharged into the air without being utilized, and the fuel and coolant are used to absorb this part of the heat, which requires the aircraft to have a complete liquid management and control system.

[0004] Based on the above problems, the present application uses the idea in the third scheme, adopts a model predictive control method, and designs an automatic control heat management system scheme that can accurately meet the temperature control requirements of modern aircraft while minimizing the heat deposition of the return oil, realizes the reasonable distribution of aircraft heat, and achieves the full utilization of heat energy. SUMMARY

[0005] In order to overcome the above problems, the present inventors have made intensive research and designed an aircraft heat management system scheme based on model predictive control, in which, based on model prediction, the existing fuel and coolant on the aircraft are used as the aircraft heat sink, the temperature of the fuel is also raised while the on-board equipment and electronic systems are cooled, in the method, the fuel is controlled to sequentially pass through the liquid cooling system heat exchanger and the fuel-hydraulic oil heat exchanger to exchange heat, and then the fuel is divided into a return flow part and a fuel supply part, the return flow part is controlled to directly flow back to the fuel tank, and the fuel supply part enters the fuel-lubricating oil heat exchanger and then enters the engine, the fuel temperature is controlled by adjusting the flow rate of the return flow part, so that it is stabilized at the ideal temperature, thereby achieving the present application.

[0006] Specifically, the purpose of the present application is to provide an aircraft heat management system scheme based on model predictive control, in which the following operations are continuously and sequentially performed:

[0007] Step 1, control the fuel to flow out of the fuel tank, and the flow rate is q f0 ,

[0008] Step 2, control the fuel to enter the liquid cooling system heat exchanger HX1 and exchange heat with the liquid cooling medium in the liquid cooling system heat exchanger HX1;

[0009] Step 3, control the fuel to enter the fuel-hydraulic oil heat exchanger HX2 and exchange heat with the liquid cooling medium in the fuel-hydraulic oil heat exchanger HX2;

[0010] Step 4, divide the fuel into two parts, i.e. a return flow part and a fuel supply part, control the return flow part to directly flow back to the fuel tank, the flow rate of the return flow part is q r ; the fuel supply part enters the fuel-lubricating oil heat exchanger HX3 and exchanges heat with the liquid cooling medium in the fuel-lubricating oil heat exchanger HX3, and then flows to the engine as fuel for combustion; the flow rate of the fuel supply part is q f0 -q r .

[0011] Wherein, the flow rate q r of the return flow part is controlled in real time to control the temperature T f3 of the fuel supply part flowing out of the fuel-lubricating oil heat exchanger HX3 and the temperature T 3out of the hot side flow output flowing out of the fuel-lubricating oil heat exchanger HX3.

[0012] Wherein, the flow rate q r of the return flow part is controlled in real time so that T f3 reaches 116.06℃ and T 3out reaches 132℃.

[0013] wherein the flow rate q of the return flow portion r Real-time is obtained by iteration of the following equation (I):

[0014]

[0015] wherein T3 represents the input temperature of the hot side fluid in the fuel-lubricant heat exchanger HX3;

[0016] q3 represents the input flow rate of the hot side fluid in the fuel-lubricant heat exchanger HX3;

[0017] T f2 represents the input temperature of the cold side fluid in the fuel-lubricant heat exchanger HX3, i.e. the temperature of the fuel supply portion when entering the fuel-lubricant heat exchanger HX3;

[0018] (q f0 -q r ) represents the input flow rate of the cold side fluid in the fuel-lubricant heat exchanger HX3, i.e. the flow rate of the fuel supply portion;

[0019] A represents the heat exchange area in the fuel-lubricant heat exchanger HX3;

[0020] k represents the heat exchange coefficient in the fuel-lubricant heat exchanger HX3;

[0021] C p represents the specific heat capacity of the hot side fluid in the fuel-lubricant heat exchanger HX3;

[0022] C pf represents the specific heat capacity of the fuel;

[0023] C represents the heat capacity of the hot side fluid in the fuel-lubricant heat exchanger HX3;

[0024] C f represents the heat capacity of the fuel;

[0025] t represents the time step;

[0026] T 3out represents the output temperature of the hot side fluid flowing out of the fuel-lubricant heat exchanger HX3;

[0027] T f3 represents the temperature of the fuel supply portion flowing out of the fuel-lubricant heat exchanger HX3, i.e. the output temperature of the cold side fluid;

[0028] δT 3out represents the change amount of the output temperature of the hot side fluid in the fuel-lubricant heat exchanger HX3;

[0029] δT f3 represents the change amount of the output temperature of the cold side fluid in the fuel-lubricant heat exchanger HX3;

[0030] δq r represents the change amount of the flow rate of the return flow portion.

[0031] wherein the change amount δT of the hot-side fluid output temperature in the fuel-lubricant heat exchanger HX3 3out obtained by measuring the difference of the hot-side fluid output temperature in the fuel-lubricant heat exchanger HX3 in the last two time steps, and the initial value is 0.

[0032] wherein the change amount δT of the cold-side fluid output temperature in the fuel-lubricant heat exchanger HX3 f3 obtained by measuring the difference of the cold-side fluid output temperature in the fuel-lubricant heat exchanger HX3 in the last two time steps, and the initial value is 0.

[0033] wherein the change amount δq of the flow rate of the return flow portion r obtained by the following formula (two):

[0034] δq r = q r - q r '(two)

[0035] wherein q r 'represents the flow rate of the return flow portion in the last time step, and the initial value is 0.

[0036] The present application has the beneficial effects including:

[0037] (1) According to the aircraft heat management system scheme based on model predictive control provided by the present application, the heat generated in the airborne electronic equipment, hydraulic oil and lubricant is fully utilized to warm up the fuel, and at the same time, the coolant of the airborne electronic equipment, the hydraulic oil and the lubricant are cooled by the fuel, so as to coordinate the heat balance in the aircraft body and maximize the performance of the flight in all aspects.

[0038] (2) According to the aircraft heat management system scheme based on model predictive control provided by the present application, the flow rate of the return flow portion is obtained in real time by an online optimization method, so that the final fuel temperature of the system can be continuously stabilized, and at the same time, the change of the control effect of the system can be ensured to be not drastic. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 showing the overall working flowchart of the aircraft heat management system scheme based on model predictive control of the present application;

[0040] Figure 2 showing the temperature curve of the fuel supply portion flowing out of the fuel-lubricant heat exchanger HX3, i.e. the cold-side fluid output temperature, with time in the embodiment and the comparative example of the present application;

[0041] Figure 3 The curves showing the change in output temperature of the hot edge fluid flowing out of the fuel-lubricating oil heat exchanger HX3 over time are shown in the embodiments and comparative examples of this application. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present invention will become clearer and more apparent.

[0043] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0044] This invention provides a model predictive control-based aircraft thermal management system solution, such as... Figure 1 As shown in the figure, the following operations are continuously executed sequentially in this system scheme: that is, the following steps are performed once in each time step to complete the thermal management work of that time step;

[0045] Step 1: Control the flow of fuel from the fuel tank, with a flow rate of q. f0 The q f0 Generally, the flow rate is relatively large, sufficient to meet the fuel consumption required for normal flight; preferably, the aircraft can be divided into multiple flight modes based on fuel consumption, and a corresponding flow rate q is set for each flight mode. f0 ;

[0046] Step 2: Control the fuel to enter the liquid cooling system heat exchanger HX1 and exchange heat with the liquid cooling medium in the liquid cooling system heat exchanger HX1; The liquid cooling system heat exchanger in this application includes multiple electronic devices in the aircraft, and the electronic devices are equipped with a liquid cooling system. The coolant of the liquid cooling system flows centrally to a preset position to form the liquid cooling system heat exchanger. In this application, fuel is used to replace the coolant of the liquid cooling system for cooling.

[0047] Step 3: Control the fuel to enter the fuel-hydraulic oil heat exchanger HX2 and exchange heat with the liquid cooling medium in the fuel-hydraulic oil heat exchanger HX2; The fuel-hydraulic oil heat exchanger in this application includes the hydraulic system in the aircraft, and fuel is used to replace the coolant in the conventional hydraulic system in this application.

[0048] Step 4: Divide the fuel into two parts: a return section and a combustion supply section. Control the return section to flow directly back into the fuel tank. The flow rate of the return section is q. r; the fuel supply portion enters the fuel-oil heat exchanger HX3, exchanges heat with the liquid cooling medium in the fuel-oil heat exchanger HX3, and then flows to the engine as fuel for combustion; the flow rate of the fuel supply portion is q f0 -q r .

[0049] The fuel-oil heat exchanger in the present application includes a lubricating oil system in an airplane, and the fuel is used to replace the coolant in the conventional lubricating oil.

[0050] In the present application, a fuel pump is arranged in front of the combustion chamber of the engine to provide power for the fuel flow, so that a sufficient amount of fuel enters the combustion chamber in real time according to the plan. Preferably, a branch pipeline of the oil pipe is further arranged near the fuel pump, which directly leads to the fuel tank, and can guide the excess fuel into the fuel tank through the branch pipeline when the flow rate of the fuel supply portion is greater than the required fuel of the combustion chamber.

[0051] In a preferred embodiment, the flow rate q r of the return flow portion is controlled in real time to control the temperature T f3 of the fuel supply portion flowing out of the fuel-oil heat exchanger HX3 and the hot side fluid output temperature T 3out .

[0052] Preferably, the flow rate q r of the return flow portion is controlled in real time to make T f3 reach 116.06℃, and make T 3out reach 132℃.

[0053] In a preferred embodiment, the flow rate q r of the return flow portion is obtained in real time by iteration according to the following formula (I) before starting to perform the heat control work of this time step:

[0054]

[0055] Wherein, T3 represents the input temperature of the hot side fluid in the fuel-oil heat exchanger HX3;

[0056] q3 represents the input flow rate of the hot side fluid in the fuel-oil heat exchanger HX3, which is monitored and obtained by setting a flow meter in the lubricating oil pipeline;

[0057] T f2 represents the input temperature of the cold side fluid in the fuel-oil heat exchanger HX3, i.e. the temperature of the fuel supply portion entering the fuel-oil heat exchanger HX3;

[0058] (q f0 -q r) represents the cold side fluid input flow rate of the fuel-lubricant heat exchanger HX3, i.e. the flow rate of the fuel supply part;

[0059] A represents the heat exchange area in the fuel-lubricant heat exchanger HX3;

[0060] k represents the heat exchange coefficient in the fuel-lubricant heat exchanger HX3;

[0061] C p represents the specific heat capacity of the hot side fluid in the fuel-lubricant heat exchanger HX3;

[0062] C pf represents the specific heat capacity of the fuel;

[0063] C represents the heat capacity of the hot side fluid in the fuel-lubricant heat exchanger HX3;

[0064] C f represents the heat capacity of the fuel;

[0065] t represents the time step, generally taking a value of 0.01 seconds;

[0066] T 3out represents the output temperature of the hot side fluid flowing out of the fuel-lubricant heat exchanger HX3;

[0067] T f3 represents the temperature of the fuel supply part flowing out of the fuel-lubricant heat exchanger HX3, i.e. the output temperature of the cold side fluid;

[0068] δT 3out represents the change amount of the output temperature of the hot side fluid in the fuel-lubricant heat exchanger HX3;

[0069] δT f3 represents the change amount of the output temperature of the cold side fluid in the fuel-lubricant heat exchanger HX3;

[0070] δq r represents the change amount of the flow rate of the return part.

[0071] In the scheme, a plurality of temperature sensors are arranged in the fuel pipeline, the electronic equipment liquid cooling pipeline, the hydraulic oil pipeline and the lubricant pipeline, so that the temperature at each position can be monitored in real time;

[0072] Preferably, the change amount δT of the output temperature of the hot side fluid in the fuel-lubricant heat exchanger HX3 is determined according to the following formula: 3out The change amount δT of the output temperature of the hot side fluid in the fuel-lubricant heat exchanger HX3 is obtained by measuring the difference between the output temperatures of the hot side fluid in the fuel-lubricant heat exchanger HX3 in the last two time steps, and the initial value is 0, i.e. the value is 0 in the case where there are no last two time steps.

[0073] Preferably, the variation amount δT of the cold edge fluid output temperature in the fuel-lubricating oil heat exchanger HX3 f3 The difference value of the cold edge fluid output temperature in the fuel-lubricating oil heat exchanger HX3 in the last two time steps is obtained by measurement, and the initial value is 0, i.e. the value is 0 in the absence of the last two time steps.

[0074] Preferably, the variation amount δq of the flow rate of the return flow portion r Obtained by the following formula (two):

[0075] δq r = q r -q r ′(two)

[0076] Wherein, q r ′ represents the flow rate of the return flow portion in the last time step, and the initial value is 0.

[0077] Embodiment

[0078] Model building is carried out in simulink, and oil tank, liquid cooling system heat exchanger, fuel-hydraulic oil heat exchanger, fuel-lubricating oil heat exchanger and connecting pipeline are set. The flow rate of fuel is controlled by the aircraft heat management method based on model predictive control, so as to expect that the fuel temperature is stabilized at 116.06℃ as soon as possible.

[0079] The specific control process is as follows:

[0080] Step 1, control the fuel to flow out from the fuel tank, and the flow rate is q f0 ,

[0081] Step 2, control the fuel to enter the liquid cooling system heat exchanger HX1 and exchange heat with the liquid cooling medium in the liquid cooling system heat exchanger HX1;

[0082] Step 3, control the fuel to enter the fuel-hydraulic oil heat exchanger HX2 and exchange heat with the liquid cooling medium in the fuel-hydraulic oil heat exchanger HX2;

[0083] Step 4, divide the fuel into two parts, i.e. return flow portion and fuel supply portion, control the return flow portion to flow back to the fuel tank directly, and the flow rate of the return flow portion is q r ; the fuel supply portion enters the fuel-lubricating oil heat exchanger HX3 and exchanges heat with the liquid cooling medium in the fuel-lubricating oil heat exchanger HX3, and then flows to the engine as fuel for combustion; the flow rate of the fuel supply portion is q f0 -q r .

[0084] The flow rate q r of the return flow portion is obtained by iteration in real time by the following formula (one):

[0085]

[0086] wherein T3 represents the input temperature of the hot side fluid in the fuel-lubricant heat exchanger HX3;

[0087] q3 represents the input flow rate of the hot side fluid in the fuel-lubricant heat exchanger HX3;

[0088] T f2 represents the input temperature of the cold side fluid in the fuel-lubricant heat exchanger HX3, i.e. the temperature of the fuel supply portion when entering the fuel-lubricant heat exchanger HX3;

[0089] (q f0 -q r ) represents the input flow rate of the cold side fluid in the fuel-lubricant heat exchanger HX3, i.e. the flow rate of the fuel supply portion;

[0090] A represents the heat exchange area in the fuel-lubricant heat exchanger HX3;

[0091] k represents the heat exchange coefficient in the fuel-lubricant heat exchanger HX3;

[0092] C p represents the specific heat capacity of the hot side fluid in the fuel-lubricant heat exchanger HX3;

[0093] C pf represents the specific heat capacity of the fuel;

[0094] C represents the heat capacity of the hot side fluid in the fuel-lubricant heat exchanger HX3;

[0095] C f represents the heat capacity of the fuel;

[0096] t represents the time step;

[0097] T 3out represents the output temperature of the hot side fluid flowing out of the fuel-lubricant heat exchanger HX3;

[0098] T f3 represents the temperature of the fuel supply portion flowing out of the fuel-lubricant heat exchanger HX3, i.e. the output temperature of the cold side fluid;

[0099] δT 3out represents the change in the output temperature of the hot side fluid in the fuel-lubricant heat exchanger HX3; obtained by measuring the difference in the output temperature of the hot side fluid in the fuel-lubricant heat exchanger HX3 in the last two time steps, and the initial value is 0;

[0100] δT f3represents the change in the temperature of the hot side fluid output from the fuel-lubricant heat exchanger HX3, and is obtained by the following formula (two):

[0101] δq r represents the change in the flow rate of the return flow portion, and is obtained by the following formula (two):

[0102] δq r = q r - q r ′(two)

[0103] wherein q r ′ represents the flow rate of the return flow portion in the previous time step, and has an initial value of 0.

[0104] The obtained temperature curve of the hot side fluid output from the fuel-lubricant heat exchanger HX3 over time is shown in FIG. 6. Figure 2

[0105] The obtained temperature curve of the hot side fluid output from the fuel-lubricant heat exchanger HX3 over time is shown in FIG. 6. Figure 3

[0106] Comparative Example

[0107] The model was built in simulink, and the oil tank, liquid cooling system heat exchanger, fuel-hydraulic oil heat exchanger, fuel-lubricant heat exchanger, and connecting pipeline were set to be consistent with those in the embodiment. The flow rate of the fuel was controlled by a classical PID control method, so as to expect that the fuel temperature is stabilized at 116.06℃ as soon as possible.

[0108] The classical PID control method is the PID control method described in (Mexican) Ivan D. Diaz Rodriguez, (Korean) Han Sang-gin, (American) Shankar P. Bhatnagar; Chen Yong, Wang Long, Li Hongbo, Zhou Yang, Feng Haoming translation. PID controller analysis design [M]. Beijing: National Defense Industry Press, 2023.

[0109] The obtained temperature curve of the hot side fluid output from the fuel-lubricant heat exchanger HX3 over time is shown in FIG. 6. Figure 2

[0110] The obtained temperature curve of the hot side fluid output from the fuel-lubricant heat exchanger HX3 over time is shown in FIG. 6. Figure 3

[0111] Figure 2 In FIG. 6, the red curve is the T f3 ​​​​The output curve, the black solid line is the T of the system after the model-based predictive control method for aircraft thermal management in the embodiment is added f3 The output curve, it can be found that the controller designed by using the classical PID control method has a large overshoot before the temperature is stabilized to the ideal state, that is, the relative stability of the PID controller is lower than that of the model-based predictive control method for aircraft thermal management; the system under the PID controller approaches the stable state at 8s, while the system under the model-based predictive control method for aircraft thermal management in the embodiment can quickly reach the stable state within 3s, the response speed is fast, and the final steady-state output value is larger than that of the system under the PID controller, and is closer to the ideal temperature value.

[0112] Figure 3 The output curve, the black solid line is the T of the system after the model-based predictive control method for aircraft thermal management in the embodiment is added 3out The output curve, the black solid line is the T of the system after the model-based predictive control method for aircraft thermal management in the embodiment is added 3out The output curve, it can be found that the controller designed by using the classical PID control method has a large overshoot before the temperature is stabilized to the ideal state, that is, the relative stability of the PID controller is lower than that of the model-based predictive control method for aircraft thermal management; the system under the PID controller approaches the stable state at 8s, while the system under the model-based predictive control method for aircraft thermal management in the embodiment can quickly reach the stable state within 3s, the response speed is fast, and the final steady-state output value is larger than that of the system under the PID controller, and is closer to the ideal temperature value.

[0113] The above describes the present application in combination with preferred embodiments, but these embodiments are only exemplary and are used for illustration only. On this basis, various substitutions and improvements can be made to the present application, and these all fall within the protection scope of the present application.

Claims

1. A model predictive control based aircraft thermal management system scheme, characterized in that, The method continuously performs the following operations in sequence: Step 1, the fuel flow from the fuel tank is controlled at a rate of q f0 , Step 2, control the fuel into the liquid cooling system heat exchanger (HX1) and exchange heat with the liquid cooling medium in the liquid cooling system heat exchanger (HX1); Step 3, control the fuel into the fuel-hydraulic oil heat exchanger (HX2) and exchange heat with the liquid cooling medium in the fuel-hydraulic oil heat exchanger (HX2); Step 4, the fuel oil is divided into two parts, a return part and a fuel supply part, the return part is directly controlled to flow back to the fuel tank, the flow rate of the return part is q r ; the fuel supply part enters the fuel-lubricating oil heat exchanger (HX3), exchanges heat with the liquid cooling medium in the fuel-lubricating oil heat exchanger (HX3), and then flows to the engine for combustion as fuel; the flow rate of the fuel supply part is q f0 -q r .

2. The model predictive control-based aircraft thermal management system scheme according to claim 1, characterized in that, by controlling in real time the flow rate q of the return flow r to control the temperature T of the fuel supply portion flowing out from the fuel-lubricant heat exchanger (HX3) f3 and the hot side fluid output temperature T flowing out from the fuel-lubricant heat exchanger (HX3) 3out .

3. The model predictive control-based aircraft thermal management system scheme according to claim 2, characterized in that, By controlling in real time the flow q of the backflow section r So that T f3 Reaches 116.06°C, so that T 3out Reaches 132°C.

4. The model predictive control-based aircraft thermal management system scheme according to claim 2, characterized in that, the flow rate q of the reflux portion r Real time is obtained by iterating the following equation (one): wherein T3 represents the input temperature of the hot side fluid in the fuel-lubricating oil heat exchanger (HX3); q3 represents the input flow rate of the hot side fluid in the fuel-lubricating oil heat exchanger (HX3); T f2 Tin represents the cold side fluid input temperature in the fuel-lubricant heat exchanger (HX3), i.e. the temperature of the fuel supply portion entering the fuel-lubricant heat exchanger (HX3); (q f0 -q r ) represents the fuel-lubricant heat exchanger (HX3) cold side fluid input flow rate, i.e. the fuel supply portion flow rate; A represents the heat exchange area in the fuel-lubricating oil heat exchanger (HX3); k represents the heat exchange coefficient in the fuel-lubricating oil heat exchanger (HX3); C p Cp,hot represents the specific heat capacity of the hot side fluid in the fuel-lubricant heat exchanger (HX3); C pf Cp represents the specific heat capacity of the fuel; C represents the heat capacity of the hot side fluid in the fuel-lubricating oil heat exchanger (HX3); C f Cp represents the heat capacity of the fuel; t represents the time step; T 3out represents the hot side fluid output temperature out of the fuel-lubricant heat exchanger (HX3); T f3 Tfuel_out represents the temperature of the fuel supply portion flowing out of the fuel-lubricant heat exchanger (HX3), i.e. the cold side fluid output temperature; δT 3out represents the amount of change in the hot side fluid output temperature in the fuel-lubricant heat exchanger (HX3); δT f3 represents the amount of change in the cold side fluid output temperature in the fuel-lubricant heat exchanger (HX3); δq r represents the amount of change in the flow rate of the reflux portion.

5. The model predictive control-based aircraft thermal management system scheme according to claim 3, characterized in that, the variation δT of the hot side fluid output temperature in the fuel-lubricant heat exchanger (HX3) 3out obtained by measuring the difference between the hot side fluid output temperatures in the fuel-lubricant heat exchanger (HX3) in the last two time steps, with initial value 0.

6. The model predictive control-based aircraft thermal management system scheme according to claim 3, characterized in that, the amount of change δT of the cold edge fluid output temperature in the fuel-lubricant heat exchanger (HX3) f3 obtained by measuring the difference of the cold edge fluid output temperature in the fuel-lubricant heat exchanger (HX3) in the last two time steps, with initial value 0.

7. The model predictive control-based aircraft thermal management system scheme according to claim 3, characterized in that, The amount of change δq of the flow rate of the reflux portion r Obtained by the following equation (two) δq r = q r - q r ′ (two) where q r qrepresents the flow rate of the backflow portion in the previous time step, and its initial value is 0.

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