A heat sink dynamic control method for an aircraft thermal management system based on heat exchange capacity prediction

Abstract

The application discloses a heat sink dynamic control method of an aircraft thermal management system based on heat exchange capacity prediction, and belongs to the field of aircraft thermal management. The method of the application firstly constructs a heat exchange capacity prediction model, and then performs heat sink dynamic control of the aircraft thermal management system based on heat exchange capacity prediction. The application can match the optimal fuel heat sink flow according to the operating condition, improve the utilization efficiency of the heat sink, and is beneficial to the safe, stable and efficient operation of the thermal management system. The heat exchange capacity prediction algorithm based on the heat exchanger directly solves the required fuel heat sink flow through parameters such as inlet temperature, and does not need a feedback link, so that the control response speed is fast.

Description

Technical Field

[0001] This invention belongs to the field of aircraft thermal management, specifically relating to a dynamic control method for heat sinks in an aircraft thermal management system based on heat exchange capacity prediction. Background Technology

[0002] Traditional aircraft thermal management systems use fuel as the primary heat sink. A portion of the fuel, drawn from the fuel supply manifold and pressurized by a cooling pump, enters heat exchange devices such as fuel-liquid heat exchangers, fuel-hydraulic oil heat exchangers, and fuel-lubricating oil heat exchangers. These devices cool the heat transfer media, including coolant, hydraulic oil, and lubricating oil. The heated fuel is then sent to the engine for combustion or returned to the fuel consumption compartment. Cooling fuel is primarily controlled by a constant flow rate, maintaining the fuel flow at a relatively constant value or switching between a few constant values, resulting in a simplistic control model. When the heat load fluctuates significantly, the fuel flow cannot be adjusted promptly. This leads to two problems: excessive power consumption due to over-fuel supply and the risk of overheating failure due to insufficient fuel supply.

[0003] With the development of aviation technology, the heat generation of various airborne electronic, electrical, and actuation devices is constantly increasing. The efficient and stable operation of the aircraft thermal management system has become one of the key factors affecting aircraft system performance. How to change the traditional constant flow operation mode and dynamically control the fuel heat sink according to the operating conditions to improve the heat sink utilization efficiency is an urgent problem to be solved in the field of aircraft thermal management. Summary of the Invention

[0004] The purpose of this invention is to provide a dynamic control method for the heat sink of an aircraft thermal management system based on heat exchange capacity prediction. This method dynamically adjusts the flow distribution of the fuel heat sink based on heat load fluctuations and changes in fuel heat sink temperature, fully utilizes its heat absorption potential, meets temperature control requirements, and improves the thermal management capability of the aircraft thermal management system.

[0005] The technical solution of the present invention:

[0006] A dynamic control method for heat sink in an aircraft thermal management system based on heat transfer capacity prediction, comprising the following steps:

[0007] Step 1: Construct a heat exchange capacity prediction model.

[0008] The heat transfer models of the various heat exchangers in the aircraft are as follows:

[0009]

[0010] In the formula, Q represents the heat exchanger's heat transfer capacity; e represents the heat exchanger's efficiency; C min T represents the smaller of the heat capacity flow rates of the hot and cold working fluids in the heat exchanger, where the heat capacity flow rate is defined as the product of the working fluid flow rate m and the specific heat Cp; h_in T represents the inlet temperature of the hot fluid.c_in This refers to the inlet temperature of the cold fluid (fuel heat sink).

[0011] Define the overall efficiency E of the heat exchanger.

[0012]

[0013] Substituting equation (2) into equation (1), we get:

[0014]

[0015] Equation (3) shows that, under given temperature boundary conditions, the heat exchanger's heat transfer capacity depends on its overall efficiency, E. From heat transfer theory and the definition of overall heat exchanger efficiency, when the heat exchanger's structural parameters remain constant, E is mainly related to the mass flow rate m of the hot and cold fluids. c m h Therefore, constructing a predictive model for the heat exchanger's heat transfer capacity involves establishing E and m. c and m h The functional relationship between them.

[0016] Based on heat exchanger test data, E and m were obtained under various operating conditions. c and m h Furthermore, a model characterizing the heat exchanger's heat transfer capacity is established using a data fitting algorithm as follows:

[0017]

[0018] in, Indicate E about and A model regarding the heat exchanger's heat transfer capacity. express about and A model regarding the heat exchanger's heat exchange capacity.

[0019] Step 2: Dynamic control of the heat sink in the aircraft thermal management system based on heat exchange capacity prediction.

[0020] Based on the functions characterizing the heat exchanger's heat transfer capacity in equations (4) and (5) and Determine the required mass flow rate of the fuel oil heat sink (i.e., the cold fluid in the heat exchanger). The purpose of adjusting the fuel oil heat sink mass flow rate is to minimize the heat sink mass flow rate to avoid oversupply and improve heat sink utilization efficiency. Specifically, the control objective is to maximize the outlet temperature of the hot and cold fluids in the heat exchanger. The method to achieve this is as follows:

[0021] First, the mass flow rate m of the hot and cold fluids at time t. c (t), m h(t) Substitute into the function characterizing the heat exchanger's heat transfer capacity The predicted value of the overall efficiency E of the heat exchanger is obtained from the calculation. pred (t); combined with the inlet temperature value T of the hot and cold fluids c_in (t) and T h_in Substituting (t) into equation (3), we obtain the predicted heat exchange rate Q. pred (t); Set the outlet temperature of the cold fluid (heat sink) to its upper temperature limit T. c_max Calculate the mass flow rate (m) of the cold fluid (heat sink) at the next moment. c_1 (t+1) is:

[0022]

[0023] in, This indicates the specific heat capacity of a cold fluid;

[0024] Then, the outlet temperature of the hot fluid is set to its upper temperature limit T. h_max The overall efficiency setpoint E of the heat exchanger is calculated based on the heat balance relationship of the heat fluid and equation (3). set (t),

[0025]

[0026] in, This indicates the specific heat capacity of a hot fluid;

[0027] The current thermal fluid mass flow rate m at time t h (t) and the overall efficiency setpoint of the heat exchanger E set (t) Substitute into the function characterizing the heat exchanger's heat transfer capacity The mass flow rate of the cold fluid (heat sink) at the next moment is calculated as m. c_2 (t+1).

[0028] Finally, to ensure that the outlet temperatures of both the hot and cold fluids do not exceed their upper temperature limits, the mass flow rate of the heat sink (cold fluid) at the next moment is determined to be the larger of the two calculated values ​​above, namely:

[0029]

[0030] Find the difference between the current flow rate of the heat sink (cold fluid) and the calculated value based on the heat transfer capacity prediction.

[0031]

[0032] If Δm c If the error is outside the allowable range, the thermal management system needs to be controlled and adjusted using a PID control algorithm: when the heat sink flow rate difference Δm cWhen the difference is greater than zero, the valve opening or pump speed needs to be increased to improve the heat sink flow rate; when the heat sink flow rate difference Δm c When the flow rate is less than zero, the valve opening or pump speed needs to be reduced to decrease the heat sink flow rate.

[0033] Furthermore, in the dynamic control method for heat sink of the aircraft thermal management system for predicting heat exchange capacity, the changes in fluid physical properties are ignored, and parameters such as density and specific heat are considered to be constants.

[0034] Furthermore, the thermal management system can be flexibly adjusted based on the system architecture and PID algorithm, such as adjusting valve opening and pump speed.

[0035] The beneficial effects of this invention are:

[0036] (1) Matching the optimal fuel heat sink flow rate according to the operating conditions improves the heat sink utilization efficiency and is conducive to the safe, stable and efficient operation of the thermal management system.

[0037] (2) The heat exchange capacity prediction algorithm based on the heat exchanger directly solves the required fuel heat sink flow rate through parameters such as inlet temperature, without the need for feedback, and the control response speed is fast. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the thermal management system of an aircraft.

[0039] Figure 2 This is a schematic diagram of a heat exchanger on an aircraft.

[0040] In the diagram: 1: Variable frequency cooling pump; 2: Fuel-coolant heat exchanger; 3: Fuel-hydraulic oil heat exchanger; 4: Fuel-lubricating oil heat exchanger; 5: First adjustable flow valve; 6: Second adjustable flow valve; 7: Third adjustable flow valve. Detailed Implementation

[0041] The following describes the specific implementation of the present invention in further detail, taking a certain aircraft thermal management system as an example.

[0042] Aircraft use various types of heat exchangers as heat exchange devices, such as fuel-coolant heat exchangers, fuel-hydraulic oil heat exchangers, and fuel-lubricating oil heat exchangers. Figure 1 The thermal management system for an aircraft includes a variable frequency cooling pump 1, a fuel-coolant heat exchanger 2, a fuel-hydraulic oil heat exchanger 3, a fuel-lubricating oil heat exchanger 4, a first adjustable flow valve 5, a second adjustable flow valve 6, and a third adjustable flow valve 7. The variable frequency cooling pump 1 draws fuel from the aircraft's fuel supply manifold and then divides it into three parallel fuel branches. The fuel flowing through each fuel branch is collected and then returned to the fuel supply manifold.

[0043] against Figure 1The aircraft thermal management system shown employs a dynamic control method for the fuel heat sink based on heat transfer capacity prediction to dynamically allocate the flow rate of the fuel heat sink. The steps are as follows:

[0044] Step 1: Construct a heat exchange capacity prediction model.

[0045] Predictive models for the heat exchange capacity of fuel-coolant heat exchanger 2, fuel-hydraulic oil heat exchanger 3, and fuel-lubricating oil heat exchanger 4 in the aircraft thermal management system are established. The heat exchange processes in each heat exchanger are as follows: Figure 2 As shown, high-temperature hot fluids such as coolant, hydraulic oil, and lubricating oil transfer heat to the relatively cooler fuel. The fuel absorbs heat, heats up, and then enters the engine for combustion, thus dissipating heat from the engine. The heat exchange models for each heat exchanger are as follows:

[0046]

[0047] In the formula, Q represents the heat exchanger's heat transfer capacity; e represents the heat exchanger's efficiency; C min T represents the smaller of the heat capacity flow rates of the hot and cold working fluids in the heat exchanger, where the heat capacity flow rate is defined as the product of the working fluid flow rate m and the specific heat Cp; h_in T is the inlet temperature of the hot fluids (coolant, hydraulic oil, and lubricating oil). c_in This is the inlet temperature of the cold fluid (fuel).

[0048] To facilitate data processing when constructing the heat exchanger capacity prediction model, the overall efficiency E of the heat exchanger is defined.

[0049]

[0050] Substituting equation (2) into equation (1), we get:

[0051]

[0052] As shown in equation (3), under given temperature boundary conditions, the heat exchange capacity of a heat exchanger mainly depends on its overall efficiency E. From heat transfer theory and the definition of overall heat exchanger efficiency, it can be seen that when the structural parameters of the heat exchanger remain unchanged, E is mainly related to the mass flow rate m of the hot and cold fluids. c m h Therefore, constructing a predictive model for the heat exchanger's heat transfer capacity involves establishing E and m. c and m h The functional relationship between them.

[0053] Based on heat exchanger test data, E and m were obtained under various operating conditions. c and m h Furthermore, a model characterizing the heat exchanger's heat transfer capacity can be established using neural networks or other effective data fitting algorithms, as follows:

[0054]

[0055] in, Indicate E about and A model regarding the heat exchanger's heat transfer capacity. express about and A model regarding the heat exchanger's heat transfer capacity; for example, using historical data to separately... and , and As inputs to the neural network model, E, The two trained neural network models can be represented by formulas (4) and (5) as the output of the neural network model.

[0056] for Figure 1 For the thermal management system of an aircraft shown, predictive models for the heat exchange capacity of fuel-coolant heat exchanger 2, fuel-hydraulic oil heat exchanger 3, and fuel-lubricating oil heat exchanger 4 are established respectively. The predictive model for the heat exchange capacity of fuel-coolant heat exchanger 2 is as follows:

[0057]

[0058] In the formula m ry1 (t), m lqy (t) represents the fuel and coolant mass flow rates of the fuel-coolant heat exchanger 2, respectively.

[0059] The prediction model for the heat exchange capacity of the fuel-hydraulic oil heat exchanger is as follows:

[0060]

[0061] In the formula m ry2 (t), m yy (t) represents the mass flow rates of fuel and coolant in the fuel-hydraulic oil heat exchanger 3, respectively.

[0062] The prediction model for the heat exchange capacity of fuel-oil heat exchanger 4 is as follows:

[0063]

[0064] In the formula m ry3 (t), m hy (t) represents the mass flow rates of fuel and coolant in the fuel-oil heat exchanger 4, respectively.

[0065] Step 2: Dynamic control of the heat sink in the aircraft thermal management system based on heat exchange capacity prediction.

[0066] Based on the heat exchange capacity prediction models of fuel-coolant heat exchanger 2, fuel-hydraulic oil heat exchanger 3, and fuel-lubricating oil heat exchanger 4 in step 1, the required fuel heat sink mass flow rate for each heat exchanger is calculated. The purpose of adjusting the fuel heat sink mass flow rate is to minimize the heat sink mass flow rate to avoid excessive heat sink supply and improve heat sink utilization efficiency. Specifically, the control objective is to maximize the outlet temperature of the hot and cold fluids in the heat exchanger, which is achieved as follows:

[0067] First, the mass flow rate m of the hot and cold fluids at time t. ry1 (t), m lqy (t), m ry2 (t), m yy (t), m ry3 (t), m hy (t) Substitute the functions F1(·), F2(·), and F3(·) that characterize the heat exchanger capacity to obtain the predicted comprehensive efficiency E of fuel-coolant heat exchanger 2, fuel-hydraulic oil heat exchanger 3, and fuel-lubricating oil heat exchanger 4. 1_pred (t), E 2_pred (t), E 3_pred (t); combined with the inlet temperatures T of the coolant, hydraulic oil, and lubricating oil. lqy_in (t), T yy_in (t), T hy_in (t) and the fuel inlet temperature T of each heat exchanger ry1_in (t), T ry2_in (t), T ry3_in Substituting (t) into equation (3), we obtain the predicted heat exchange rate Q. 1_pred (t), Q 2_pred (t), Q 3_pred (t); Set the fuel outlet temperature to its upper temperature limit T. ry_max Calculate the fuel mass flow rate (m) of fuel-coolant heat exchanger 2, fuel-hydraulic oil heat exchanger 3, and fuel-lubricating oil heat exchanger 4 at the next moment. ry1_1 (t+1), m ry2_1 (t+1), m ry3_1 (t+1) are respectively:

[0068]

[0069] in, Indicates the specific heat capacity of fuel;

[0070] Then, the outlet temperatures of the coolant, hydraulic oil, and lubricating oil were set to their respective upper temperature limits, T. lqy_max T yy_max T hy_maxBased on the thermal balance relationship of the heat fluid and equation (3), the overall efficiency setpoint E of fuel-coolant heat exchanger 2, fuel-hydraulic oil heat exchanger 3 and fuel-lubricating oil heat exchanger 4 is calculated. 1_set (t), E 2_set (t), E 3_set (t),

[0071]

[0072] in, Indicates the specific heat capacity of the coolant. Indicates the specific heat capacity of hydraulic oil. Indicates the specific heat capacity of lubricating oil;

[0073] The mass flow rates m of coolant, hydraulic oil, and lubricating oil at time t. lqy (t), m yy (t), m hy (t) and the overall efficiency setpoint of the heat exchanger E 1_set (t), E 2_set (t), E 3_set Substituting (t) into the functions G1(·), G2(·), and G3(·) that characterize the heat exchanger's heat transfer capacity, we can obtain the fuel mass flow rate m at the next moment. ry1_2 (t+1), m ry2_2 (t+1), m ry3_2 (t+1).

[0074] Finally, to ensure that the coolant, hydraulic oil, lubricating oil, and fuel all do not exceed their upper temperature limits, the fuel mass flow rate at the next moment is determined to be the larger of the two calculated values ​​mentioned above, namely:

[0075]

[0076] Find the difference between the current fuel mass flow rate and the calculated value based on the heat exchange capacity prediction for fuel-coolant heat exchanger 2, fuel-hydraulic oil heat exchanger 3, and fuel-lubricating oil heat exchanger 4.

[0077]

[0078] If Δm ry1 Δm ry2 Δm ry3 If the error is outside the allowable range, the thermal management system needs to be controlled and adjusted using a PID control algorithm.

[0079] When Δm ry1 Δm ry2 Δm ry3 When the sum of the three is greater than zero, increase the speed of the variable frequency cooling pump 1 to increase the total mass flow rate of the fuel heat sink in the entire thermal management system; when Δm ry1 Δmry2 Δm ry3 When the sum of the three is less than zero, reduce the speed of the variable frequency cooling pump 1 to increase the total mass flow rate of the fuel heat sink in the entire thermal management system.

[0080] When the mass flow rate difference of the heat sink is Δm ry1 When the value is greater than zero, the opening of the first adjustable flow valve 5 needs to be increased to improve the fuel heat sink mass flow rate of the fuel-coolant heat exchanger 2; when the heat sink mass flow rate difference Δm ry1 When the flow rate is less than zero, the opening of the first adjustable flow valve 5 needs to be reduced to decrease the mass flow rate of the fuel heat sink in the fuel-coolant heat exchanger 2.

[0081] When the mass flow rate difference of the heat sink is Δm ry2 When the value is greater than zero, the opening of the second adjustable flow valve 6 needs to be increased to improve the fuel heat sink mass flow rate of the fuel-hydraulic oil heat exchanger 3; when the heat sink mass flow rate difference Δm ry2 When the flow rate is less than zero, the opening of the second adjustable flow valve 6 needs to be reduced to decrease the mass flow rate of the fuel heat sink in the fuel-hydraulic oil heat exchanger 3.

[0082] When the mass flow rate difference of the heat sink is Δm ry3 When the value is greater than zero, the opening of the third adjustable flow valve 7 needs to be increased to improve the fuel heat sink mass flow rate of the fuel-oil heat exchanger 4; when the heat sink mass flow rate difference Δm ry3 When the flow rate is less than zero, the opening of the third adjustable flow valve 7 needs to be reduced to decrease the mass flow rate of the fuel heat sink in the fuel-oil heat exchanger 4.

[0083] The above description pertains only to a specific aircraft thermal management system architecture. In reality, the heat sink dynamic control method for aircraft thermal management systems based on heat transfer capacity prediction, as described in this invention, is applicable to various aircraft thermal management systems with different architectures. It should be noted that in practical applications, those skilled in the art can make several improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention.

Claims

1. A dynamic control method for heat sinks in an aircraft thermal management system based on heat transfer capacity prediction, characterized in that, The steps are as follows: Step 1: Construct a heat exchange capacity prediction model; The heat exchange models of the various heat exchangers in the aircraft are as follows: In the formula, Q represents the heat exchanger's heat transfer capacity; e represents the heat exchanger's efficiency; C min T represents the smaller of the heat capacity flow rates of the hot and cold working fluids in the heat exchanger, where the heat capacity flow rate is defined as the product of the working fluid flow rate m and the specific heat Cp; h_in T represents the inlet temperature of the hot fluid. c_in This refers to the inlet temperature of the cold fluid. Define the overall efficiency E of the heat exchanger. Substituting equation (2) into equation (1), we get: Equation (3) shows that, under given temperature boundary conditions, the heat exchanger's heat transfer capacity depends on its overall efficiency E. From heat transfer theory and the definition of overall heat exchanger efficiency, when the heat exchanger's structural parameters remain constant, E is mainly related to the mass flow rate m of the hot and cold fluids. c m h Therefore, constructing a heat exchanger heat exchanger capacity prediction model involves establishing E and m. c and m h Functional relationship between them; Based on heat exchanger test data, E and m were obtained under various operating conditions. c and m h Furthermore, a model characterizing the heat exchanger's heat transfer capacity is established using a data fitting algorithm as follows: in, Indicate E about and A model regarding the heat exchanger's heat transfer capacity. express about and A model regarding the heat exchanger's heat transfer capacity; Step 2: Dynamic control of the heat sink in the aircraft thermal management system based on heat exchange capacity prediction; Based on the functions characterizing the heat exchanger's heat transfer capacity in equations (4) and (5) and Determine the required fuel heat sink mass flow rate. The purpose of adjusting the fuel heat sink mass flow rate is to minimize the heat sink mass flow rate to avoid excessive heat sink supply and improve heat sink utilization efficiency. Specifically, the control objective is to maximize the outlet temperature of the hot and cold fluids in the heat exchanger. The method to achieve this is as follows: First, the mass flow rate m of the hot and cold fluids at time t. c (t), m h (t) Substitute into the function characterizing the heat exchanger's heat transfer capacity The predicted value of the overall efficiency E of the heat exchanger is obtained from the calculation. pred (t); combined with the inlet temperature value T of the hot and cold fluids c_in (t) and T h_in Substituting (t) into equation (3), we obtain the predicted heat exchange rate Q. pred (t); Set the cold fluid outlet temperature to its upper temperature limit T. c_max Calculate the mass flow rate m of the cold fluid at the next moment. c_1 (t+1) is: in, This indicates the specific heat capacity of a cold fluid; Then, the outlet temperature of the hot fluid is set to its upper temperature limit T. h_max The overall efficiency setpoint E of the heat exchanger is calculated based on the heat balance relationship of the heat fluid and equation (3). set (t): in, This indicates the specific heat capacity of a hot fluid; The current thermal fluid mass flow rate m at time t h (t) and the overall efficiency setpoint of the heat exchanger E set (t) Substitute into the function characterizing the heat exchanger's heat transfer capacity The mass flow rate of the cold fluid at the next moment is obtained from the calculation. c_2 (t+1); Finally, to ensure that the outlet temperatures of both the hot and cold fluids do not exceed their upper temperature limits, the heat sink mass flow rate at the next moment is determined to be the larger of the two calculated values ​​mentioned above, namely: Calculate the difference between the current heat sink flow rate and the calculated value based on the heat exchange capacity prediction. If Δm c If the error is outside the allowable range, the thermal management system needs to be controlled and adjusted using a PID control algorithm: when the heat sink flow rate difference Δm c When the difference is greater than zero, the valve opening or pump speed needs to be increased to improve the heat sink flow rate; when the heat sink flow rate difference Δm c When the flow rate is less than zero, the valve opening or pump speed needs to be reduced to decrease the heat sink flow rate.

2. The method for dynamic control of heat sink in an aircraft thermal management system based on heat transfer capacity prediction according to claim 1, characterized in that, In the dynamic control method for heat sink of aircraft thermal management system based on heat exchange capacity prediction, the changes in fluid physical parameters are ignored, and density and specific heat are considered to be constants.

3. The method for dynamic control of heat sink in aircraft thermal management system based on heat transfer capacity prediction according to claim 1, characterized in that, The thermal management system can be flexibly adjusted based on the system architecture and PID algorithm, such as adjusting valve opening and regulating pump speed.

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