CN114154242A - Aircraft thermal management system optimization method and system - Google Patents
Aircraft thermal management system optimization method and system Download PDFInfo
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Abstract
The invention relates to an aircraft thermal management system optimization method and system, comprising the following steps: s1: acquiring aircraft parameters; s2: determining an initial value of a cold cycle and an initial flow of a high-temperature heat source; s3: calculating the preliminary temperature and pressure of the thermodynamic cycle of the air refrigeration system; s4: determining the mass flow of the air refrigeration working medium and the heat exchange capacity of each heat exchanger; s5: optimizing the geometric dimension of the heat exchanger; s6: calculating the resistance of the heat exchanger; s7: judging whether the temperature and pressure of each point of the refrigeration system are matched, if so, executing the next step; s8: if not, correcting; s9: calculating air entraining demand, turbine power output, compressor power consumption, fuel oil demand and heat exchanger weight; s10: calculating the total equivalent mass; s11: judging whether the total equivalent mass is minimum, if so, ending; s12: if not, updating the optimization variable value until the total equivalent mass is minimum. The method not only optimizes the thermodynamic cycle, but also optimizes the performance loss of the engine caused by the heat management system.
Description
Technical Field
The invention relates to the field of aircraft optimization design, in particular to an optimization method and system for an aircraft thermal management system.
Background
With the development of multi-electrochemical and electronic equipment integration technologies of aircrafts, the airborne heat load and energy requirements are in an exponential trend, and particularly, the requirements of airborne systems on cold sources are increased greatly due to the carrying of high-energy equipment such as laser weapons and electronic countermeasure platforms. Aircraft thermal management systems have become important support systems for heavily loaded aircraft, the primary function being to provide cooling and some electrical power to the aircraft. The heat is transferred from the low-temperature heat source to the high-temperature heat sink by the heat exchanger under the action of the compressor and the turbine through adjusting bleed air from an engine or an air inlet channel through an open/closed refrigeration cycle. In the traditional component-level optimization design based on the refrigeration cycle, the refrigeration cycle efficiency, the entropy production and the like are taken as optimization targets, and only the thermodynamic process of the refrigeration cycle is optimized, but the influence of the system on the performance of an aircraft engine cannot be evaluated. However, the air-entraining amount, the self weight of the system, the energy consumption and the like all affect the performance of the engine, and the optimization of a thermal management system is difficult to realize by pure component level optimization. Compared with the traditional component-level optimization design, the two-step optimization design method considers the idea of aircraft integration design more, and realizes the overall design of cooperative consideration of the thermodynamic characteristics of the system and the performance of the engine.
Disclosure of Invention
The invention aims to provide an aircraft thermal management system optimization method and system, which not only optimize thermodynamic cycle, but also optimize engine performance loss caused by a thermal management system, and are beneficial to the integrated design of the thermal management system and an aircraft.
In order to achieve the purpose, the invention provides the following scheme:
a method of optimizing an aircraft thermal management system, the method of optimizing comprising:
s1: acquiring the flight altitude, Mach number, refrigerating capacity and power supply demand of an aircraft;
s2: determining an initial value of a cold cycle and an initial flow of a high-temperature heat source; the initial value of the cold cycle is: compressor outlet temperature and system minimum pressure;
s3: calculating the initial temperature and pressure of the thermodynamic cycle of the air refrigeration system based on the initial value of the cold cycle and the initial flow of the high-temperature heat source;
s4: determining the mass flow of the air refrigeration working medium and the heat exchange capacity of each heat exchanger based on the preliminary temperature and the pressure of the thermodynamic cycle of the air refrigeration system;
s5: optimizing the geometric dimension of the heat exchanger by taking the minimum mass of the heat exchanger as a target;
s6: calculating the resistance of the heat exchanger based on the geometric dimension of the heat exchanger;
s7: judging whether the temperature and pressure of each point of the refrigeration system are matched, and if so, executing the next step;
s8: if not, correcting the pressure of the air refrigeration system, and returning to the step S3;
s9: calculating the air entraining demand, the turbine power output, the compressor power consumption, the fuel oil demand and the heat exchanger weight;
s10: calculating the total equivalent mass;
s11: judging whether the total equivalent mass is minimum, if so, ending;
s12: if not, the optimization variable value is updated, and the step S2 is returned until the total equivalent mass is minimum.
Optionally, the air refrigeration system thermodynamic cycle includes: closed air refrigeration system thermodynamic cycle and open air refrigeration system thermodynamic cycle.
Optionally, with the goal of minimizing the mass of the heat exchanger, the following formula is specifically adopted to optimize the geometric dimension of the heat exchanger:
determining an objective function:
wherein M isHXRepresents the total mass of the heat exchanger, kg;
representing an optimal design variable matrix:
scwidth of the cold fluid side fin, hcFor the height in the cold fluid side fincFor the staggered length of the cold fluid side fins, tf,cThickness of the cold fluid side fin, tcThickness of cold fluid side baffle plate, shWidth of the side fin of the hot fluid, hhIs the height in the hot fluid side fin, /)hFor the staggered length of the cold fluid side fins, tf,hThickness of the cold fluid side fin, thIs the cold fluid side baffle thickness, L is the non-flow direction length;
the constraint conditions are as follows:
LB for optimal design variable matrix
UB is an optimally designed variable matrix
Upper limit matrix of, Δ PcPressure drop, Δ P, of cold fluid side heat exchangermax,cMaximum pressure drop, Δ P, of cold fluid side heat exchangerhPressure drop, Δ P, of the heat exchanger on the hot fluid sidemax,hThe maximum pressure drop of the heat exchanger on the heat fluid side.
Optionally, the calculating the resistance of the heat exchanger based on the geometric dimension of the heat exchanger specifically includes the following steps:
using formulas
Calculating the equivalent diameter of the heat exchanger, wherein s is the width of the fin, h is the inner height of the fin, l is the staggered length of the fin, and tfIs the fin thickness;
calculating Re based on the equivalent diameter of the heat exchanger:
wherein v is the fluid flow rate and η is the fluid viscosity; ρ is the fluid density;
calculating the resistance of the heat exchanger based on the Re:
wherein, gmIs the mass flow rate of the fluid; a. thecAnd AaThe calculated flow cross-sectional areas are for the core of the heat exchanger and for each local resistance, respectively.
Based on the above method in the present invention, the present invention further provides an aircraft thermal management system optimization system, including:
the data acquisition module is used for acquiring the flight altitude, Mach number, refrigerating capacity and power supply demand of the aircraft;
the assignment module is used for determining an initial value of a cold cycle and an initial flow of a high-temperature heat source; the initial values of the cold cycle are: compressor outlet temperature and system minimum pressure;
the preliminary temperature and pressure calculation module of the thermodynamic cycle of the air refrigeration system is used for calculating the preliminary temperature and pressure of the thermodynamic cycle of the air refrigeration system based on the initial value of the cold cycle and the initial flow of the high-temperature heat source;
the air refrigeration working medium mass flow and heat exchange capacity determination module is used for determining the mass flow of the air refrigeration working medium and the heat exchange capacity of each heat exchanger based on the preliminary temperature and pressure of the thermodynamic cycle of the air refrigeration system;
the optimization module is used for optimizing the geometric dimension of the heat exchanger by taking the minimum mass of the heat exchanger as a target;
the resistance calculation module is used for calculating the resistance of the heat exchanger based on the geometric dimension of the heat exchanger;
the first judgment module is used for judging whether the temperature and the pressure of each point of the refrigerating system are matched or not, and if so, executing the next step;
the correction module is used for correcting the pressure of the air refrigeration system and returning the pressure to the preliminary temperature and pressure calculation module of the thermodynamic cycle of the air refrigeration system when the pressure of the air refrigeration system is not matched with the pressure of the air refrigeration system;
the device comprises a bleed air demand, turbine power output, compressor power consumption, fuel oil demand and heat exchanger weight calculation module, a heat exchanger weight calculation module and a control module, wherein the bleed air demand, the turbine power output, the compressor power consumption, the fuel oil demand and the heat exchanger weight calculation module are used for calculating the bleed air demand, the turbine power output, the compressor power consumption, the fuel oil demand and the heat exchanger weight;
the total equivalent mass calculating module is used for calculating the total equivalent mass;
the second judgment module is used for judging whether the total equivalent mass is minimum or not, and if so, ending the process;
and the updating optimization module is used for updating the optimization variable value and returning to the assignment module until the total equivalent quality is minimum.
Optionally, the air refrigeration system thermodynamic cycle includes: closed air refrigeration system thermodynamic cycle and open air refrigeration system thermodynamic cycle.
Optionally, the optimization module specifically adopts the following formula:
determining an objective function:
wherein M isHXRepresents the total mass of the heat exchanger, kg;
representing an optimal design variable matrix:
scwidth of the cold fluid side fin, hcFor the height in the cold fluid side fincFor the staggered length of the cold fluid side fins, tf,cThickness of the cold fluid side fin, tcThickness of cold fluid side baffle plate, shWidth of the side fin of the hot fluid, hhIs the height in the hot fluid side fin, /)hFor the staggered length of the cold fluid side fins, tf,hThickness of the cold fluid side fin, thIs a cold fluidSide baffle thickness, L is the length in the non-flow direction;
the constraint conditions are as follows:
LB for optimal design variable matrix
UB is an optimally designed variable matrix
Upper limit matrix of, Δ PcPressure drop, Δ P, of cold fluid side heat exchangermax,cMaximum pressure drop, Δ P, of cold fluid side heat exchangerhPressure drop, Δ P, of the heat exchanger on the hot fluid sidemax,hThe maximum pressure drop of the heat exchanger on the heat fluid side.
Optionally, the resistance calculation module specifically includes the following steps:
using formulas
Calculating the equivalent diameter of the heat exchanger, wherein s is the width of the fin, h is the inner height of the fin, l is the staggered length of the fin, and tfIs the fin thickness;
calculating Re based on the equivalent diameter of the heat exchanger:
wherein v is the fluid flow rate and η is the fluid viscosity; ρ is the fluid density;
calculating the resistance of the heat exchanger based on the Re:
wherein, gmIs the mass flow rate of the fluid; a. thecAnd AaThe calculated flow cross-sectional areas are for the core of the heat exchanger and for each local resistance, respectively.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
1) the two-step optimization design method not only optimizes the design of the refrigeration cycle, but also optimizes the overall performance of the heat management system;
2) the aim of minimum fuel compensation loss, total takeoff weight or equivalent mass of the same type of the aircraft is to optimally design different system architectures without being constrained by the type of the system architecture;
3) the method is simple and the calculation speed is high.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive labor.
FIG. 1 is a flow chart of a method for optimizing an aircraft thermal management system according to an embodiment of the invention;
FIG. 2 is a schematic structural diagram of an aircraft thermal management system optimization system according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide an aircraft thermal management system optimization method and system, which not only optimize thermodynamic cycle, but also optimize engine performance loss caused by a thermal management system, and are beneficial to the integrated design of the thermal management system and an aircraft.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
According to the method, a two-step optimization design of a heat management system is carried out according to the flight altitude, the Mach number, the refrigerating capacity requirement and the power supply requirement of an aircraft, wherein the first optimization design is an air refrigerating cycle optimization design based on the minimization of the quality of a heat exchanger; the second step of optimization design is based on the thermal management system optimization design of aircraft fuel compensation loss minimization; the first step of optimization design is part of the second step of optimization design.
The first step of optimization design takes the minimum quality of the air refrigeration cycle heat exchanger as a target, and the optimized variable is the geometric structure size of the heat exchanger; the second step of optimization design aims at the minimum of aircraft fuel compensation loss, total takeoff weight or equivalent mass of the same type, and the optimization variables are a certain temperature, a certain pressure and high-temperature heat source mass flow of the air refrigeration cycle in the first step of optimization design, namely the outlet temperature of a compressor and the minimum pressure of the refrigeration cycle, namely under the condition that the refrigeration capacity and the low-temperature heat source temperature are fixed, the thermodynamic working condition of the air refrigeration cycle can be determined by arbitrarily determining a certain temperature and a certain pressure.
Fig. 1 is a flowchart of an aircraft thermal management system optimization method according to an embodiment of the present invention, and as shown in fig. 1, the method includes:
the first step of the optimization design mainly comprises the steps of S1-S8, and specifically comprises the following steps:
s1: and acquiring the flight altitude, Mach number, refrigerating capacity and power supply demand of the aircraft.
S2: determining an initial value of a cold cycle and an initial flow of a high-temperature heat source; the initial value of the cold cycle is: compressor outlet temperature and system minimum pressure.
Step S2 is to assign an initial value of the optimized variable in the second step, and the assigned initial value can be divided into two aspects, that is, to assign an initial value of the cold cycle, to retrieve the outlet temperature of the compressor and the minimum pressure of the system, and to assign an initial flow of the high temperature heat source.
S3: and calculating the initial temperature and pressure of the thermodynamic cycle of the air refrigeration system based on the initial value of the cold cycle and the initial flow of the high-temperature heat source.
The step is that the preliminary temperature and pressure design is carried out on the thermodynamic cycle of the air refrigeration system according to the refrigerating capacity. In this step, the thermodynamic cycle of the air refrigeration system can be divided into two parts, namely, the thermodynamic cycle of the closed air refrigeration system and the thermodynamic cycle of the open air refrigeration system.
The closed air refrigeration cycle system comprises a high-temperature heat source heat exchanger HHX, a heat regenerator, a low-temperature heat source heat exchanger LHX and a pair of turbo compressors, wherein air subjected to pressurization and temperature rise by the compressors firstly exchanges heat with the high-temperature heat source heat exchanger, the air subjected to heat exchange enters the heat regenerator to carry out heat regeneration, the air subjected to heat regeneration enters the turbines to be cooled and expanded, the gas subjected to temperature reduction and expansion by the turbines enters the low-temperature heat source heat exchanger to carry out heat exchange, the air subjected to heat exchange enters the compressors again through the heat regenerator to be pressurized and heated, and the thermodynamic cycle of the closed air refrigeration system is completed.
For the refrigerating capacity and the flight condition, the air refrigerating cycle structure and the temperature and pressure at each point can be determined according to the following process.
Firstly, the highest temperature of a system is set according to the initial flow of a high-temperature heat source, the lowest pressure of the system is determined according to the flight ascending limit and the system tightness, and then the refrigerating capacity and the efficiency of a high-temperature heat source heat exchanger HHX are set according to the formula Q ═ Cminε Δ T (wherein, CminThe heat capacity of the hot side and the cold side of the heat exchanger is smaller, and the heat capacity of the hot side of the high-temperature heat source heat exchanger HHX is generally designed to be larger so as to increase the temperature drop of the cold side; epsilon represents the efficiency of the heat exchanger, delta h is the enthalpy difference of the inlet and the outlet on the same side of the heat exchanger, and delta T is the temperature difference of the inlet on the different side of the heat exchanger) to obtain the HHX outlet temperature of the heat exchanger of the high-temperature heat source, and the preset relevant size and formula are utilized to estimate
Pressure drop of the low-temperature heat source heat exchanger LHX is estimated to obtain outlet pressure of the low-temperature heat source heat exchanger LHX, efficiency of the heat regenerator RHX is set, turbine inlet temperature and compressor inlet temperature are calculated by the formula, and pressure ratio of the compressor can be calculated according to the formula
And (4) calculating. Using estimated given correlation dimensions and equations
Estimating the pressure drop of the heat regenerator RHX, calculating to obtain the compressor inlet pressure, namely the RHX outlet pressure, and then estimating the given related size and formula
The pressure drop of the high-temperature heat source heat exchanger HHX is estimated, the inlet and outlet pressure of the heat regenerator RHX is obtained through calculation, namely the pressure of each point of the system and the expansion ratio of the turbine are determined, and the outlet temperature of the turbine can be calculated according to the formula
And obtaining the mass flow of the air refrigeration working medium, and finally obtaining the heat exchange quantity of the high-temperature heat source heat exchanger HHX and the heat regenerator RHX. And finishing the preliminary temperature and pressure design of the thermodynamic cycle of the closed air refrigeration system.
In the thermodynamic cycle of the closed air refrigerating system, the preliminary design result is the temperature and pressure of each point in the thermodynamic cycle of the air refrigerating system according to the outlet temperature T of the turbinetoutThe formula Q ═ C is firstly utilized along with the refrigerating capacity, the inlet temperature of the high-temperature heat source, the allowable temperature limit of the low-temperature heat source and the lowest pressure of the systemminCalculating heat exchange quantity of heat exchanger by using epsilon delta T
Mass flow of air refrigerating working medium can be calculated
(CminThe heat capacity of the hot side of the heat exchanger HHX is usually designed to be larger so as to increase the temperature drop of the cold side; epsilon represents the efficiency of the heat exchanger, delta h is the enthalpy difference between the inlet and the outlet at the same side of the heat exchanger, and delta T is the temperature difference between the inlet at the different side of the heat exchanger), the heat exchange quantity of each heat exchanger can also be obtained by the methodAnd (6) calculating.
The thermodynamic cycle of the open air refrigeration system is composed of two high-temperature heat source heat exchangers, a heat regenerator, a low-temperature heat source heat exchanger and a pair of turbo compressors, wherein a system air source leads air from an engine compressor or ram air, the air source is cooled once by one high-temperature heat source heat exchanger, the air is heated and compressed by the compressors and then cooled secondarily by the other high-temperature heat source heat exchanger, the cooled air is reheated by the heat regenerator and then enters the turbines for cooling and expansion, the expanded air is subjected to heat exchange by the low-temperature heat source heat exchanger, the heat-exchanged air enters the heat regenerator again and enters the cabin through the heat regenerator, and the thermodynamic cycle of the open air refrigeration system is completed.
Firstly, calculating the temperature of a high-temperature heat source inlet according to the initial flow of a high-temperature heat source, the temperature of bleed air and the pressure, then making a difference between the temperature of bleed air and the temperature of the high-temperature heat source inlet, determining whether a high-temperature heat source heat exchanger HHX1 is needed, if the difference between the temperature of bleed air and the temperature of the high-temperature heat source inlet is smaller than the minimum heat exchange temperature difference, not needing the high-temperature heat source heat exchanger HHX1, and directly determining the outlet temperature and the pressure of the high-temperature heat source heat exchanger HHX 1; if the difference value between the heat exchange temperature difference value and the heat exchange temperature difference value is larger than or equal to the minimum heat exchange temperature difference value, the efficiency of the high-temperature heat source heat exchanger HHX1 needs to be set, and the estimated given related size and formula are utilized
The heat exchanger pressure drop is estimated to determine the outlet temperature pressure of heat exchanger HHX 1. Setting the outlet temperature of a compressor according to the inlet temperature of a high-temperature heat source heat exchanger, then making a difference between the outlet temperature and the inlet temperature of the compressor, if the difference is less than or equal to 0, the outlet pressure of the compressor is inlet pressure, if the difference is greater than 0, the outlet pressure of the compressor can be calculated by using a related formula according to the pressure ratio of the compressor, then the inlet temperature and the inlet pressure of a heat regenerator are sequentially determined by HHX2 design efficiency and estimated pressure drop, so far, the working condition of a turbine cannot be determined, the working condition needs to be determined by a cabin, the outlet pressure of the cabin is external atmospheric environment pressure, the inlet pressure of the cabin can be determined according to the pressure drop of the cabin, and then the outlet temperature and the outlet pressure of the heat regenerator and the LHX outlet temperature of the low-temperature heat source heat exchanger are calculated according to the RHRx efficiency and the estimated pressure dropPressure, inlet temperature of the chamber, using estimated relative dimensions and equations
Estimating the pressure drop of the low-temperature heat source heat exchanger to obtain the outlet pressure of the turbine so as to obtain the working pressure ratio of the turbine
And calculating the temperature supplied to the low-temperature heat source heat exchanger, wherein the temperature at the outlet of the turbine is the temperature supplied to the low-temperature heat source heat exchanger, and the preliminary temperature and pressure design of the thermodynamic cycle of the open air refrigeration system is finished.
S4: and determining the mass flow of the air refrigeration working medium and the heat exchange capacity of each heat exchanger based on the preliminary temperature and the pressure of the thermodynamic cycle of the air refrigeration system.
In the thermodynamic cycle of the open air refrigerating system, the result of the preliminary design is the temperature and pressure of each point in the thermodynamic cycle of the air refrigerating system, and according to the outlet temperature and refrigerating capacity of the turbine, the inlet temperature of the high-temperature heat source, the temperature and pressure of the air source of the bleed air, the allowable temperature limit of the low-temperature heat source and the environmental pressure, the formula Q ═ C is firstly utilizedminCalculating heat exchange amount of heat exchanger by epsilon delta T, and reusing
Mass flow of air refrigerating working medium can be calculated
(CminThe heat capacity of the hot side and the cold side of the heat exchanger is smaller, and the hot side heat capacity of the high-temperature heat source heat exchanger HHX is generally designed to be larger so as to increase the temperature drop of the cold side; epsilon represents the efficiency of the heat exchanger, delta h is the enthalpy difference of the inlet and the outlet on the same side of the heat exchanger, and delta T is the temperature difference of the inlet on the different side of the heat exchanger).
S5: and optimizing the geometric dimension of the heat exchanger by taking the minimum mass of the heat exchanger as a target.
And after the steps are finished, performing first-step optimization design in the step with the aim of minimizing the mass of the heat exchanger. In this step, the heat exchanger structure will directly affect the operating state of the refrigeration system, and the operating state of the refrigeration system provides design parameters for the heat exchanger design process.
In the lightweight design, the optimized heat exchangers are all heat exchangers involved in the circulation, and the geometric structure size of the heat exchanger is taken as the optimization variable (the width of a fin s, the height in the fin h, the staggered length of the fin l and the thickness of the fin t)fPlate interval b, baffle thickness t and non-flow direction length L),
the lightweight design problem of the heat exchanger is a single-target optimization problem, and the minimum total mass of the heat exchanger is taken as a target, namely min (M)HX) The objective function is expressed as:
wherein M isHXRepresents the total mass of the heat exchanger, kg;
representing an optimal design variable matrix (the matrix is composed of the above optimal variables):
and solving an optimized design variable matrix consisting of optimized variables on the cold side and the hot side of the heat exchanger through related constraint conditions.
scWidth of the cold fluid side fin, hcFor the height in the cold fluid side fincFor the staggered length of the cold fluid side fins, tf,cThickness of the cold fluid side fin, tcThickness of cold fluid side baffle plate, shWidth of the side fin of the hot fluid, hhIs the height in the hot fluid side fin, /)hFor the staggered length of the cold fluid side fins, tf,hThickness of the cold fluid side fin, thThe thickness of the cold fluid-side separator is L, and the length in the non-flow direction is L.
Restraint stripAnd setting an upper limit matrix UB and a lower limit matrix LB of each structural parameter according to the processing mode and the installation condition of the heat exchanger. Secondly, it is necessary to restrict the upper limit Δ P of the pressure loss in the heat exchangermax. Thus, the confinement conditions can be represented by the following formula:
LB is as described above
UB is the above
Upper limit matrix of, Δ PcPressure drop, Δ P, of cold fluid side heat exchangermax,cMaximum pressure drop, Δ P, of cold fluid side heat exchangerhPressure drop, Δ P, of heat exchanger on heat flow sidemax,hIs the maximum pressure drop of the heat exchanger at the hot fluid side (the circulating side is the hot fluid side, and the non-circulating side is the cold fluid side)
The single-target optimization design method adopts a Sequential Quadratic Programming (SQP) method, and uses a 'fminc' function in related software to convert the nonlinear optimization problem into a plurality of Quadratic Programming sub-problems for solving, so as to obtain the optimal solution of the problem.
S6: based on the geometry of the heat exchanger, the resistance of the heat exchanger is calculated.
After the step S5 is finished, the process proceeds to step S6, the resistance of the heat exchanger is calculated according to the optimal solution obtained in the step S5, and the formula is firstly used
Calculating the equivalent diameter of the heat exchanger, and then carrying out the flow area AcAssignment of and utilization of formulas
(v is the fluid flow rate and η is the fluid viscosity) and then using the formula
S7: and judging whether the temperature and the pressure of each point of the refrigeration system are matched, and if so, executing the next step.
After completion of step S6, the process proceeds to step S7 to determine whether the temperatures and pressures at the respective points in the refrigeration system match. According to the pressure drop of the heat exchanger calculated in the step S6, matching with the estimated pressure drop of each heat exchanger in the thermodynamic cycle of the air refrigeration system in the step S3, if the pressure drop is matched, ending the first-step optimization design, and entering the step S9, wherein the initial value given by the first-step air refrigeration cycle, the outlet temperature of the compressor, the minimum pressure of the system and the initial flow of the high-temperature heat source are used as input conditions of the second-step optimization design;
and if not, the step S8 is carried out to correct the pressure of the air refrigeration system, the step S3 is returned to carry out iterative calculation on the lowest pressure of the system until the temperature and the pressure of each point of the refrigeration system are matched, and the step S9 is carried out to take the initial value of the outlet temperature of the compressor, the minimum pressure of the system and the initial flow of the high-temperature heat source given by the air refrigeration cycle in the first step as the input conditions of the optimized design in the second step.
S8: if not, the pressure of the air-cooling system is corrected, and the process returns to step S3.
The second step of the optimization design mainly comprises the steps of S9-S12, and specifically comprises the following steps:
s9: calculating bleed air demand, turbine power output, compressor power consumption, fuel demand and heat exchanger weight.
After the first-step optimization design is finished, the second-step optimization design is started, step S9 is carried out according to the first-step optimization design result to calculate the air-entraining demand, the turbine power output, the compressor power consumption, the fuel oil demand and the heat exchanger weight, the air-entraining demand is the mass flow of the air refrigeration working medium, the calculation method is given in step S4, and the turbine power output can be given by a formula
The power consumption of the compressor can be obtained by calculation according to the formula
Obtaining the fuel demand, determining the fuel demand by the flight condition, calculating the heat exchange efficiency of the heat exchanger according to the heat exchange quantity of the heat exchanger, the mass flow of the fluid on the cold side and the hot side, the temperature and the pressure to obtain the number of heat transfer units and further obtain the number of single-side heat transfer units, obtaining the mass flow rate in the heat exchanger according to the number of the single-side heat transfer units and the resistance of the heat exchanger obtained in the step S6 to obtain the flow area, obtaining the difference between the flow area obtained here and the flow area assigned in the step S6, and obtaining the weight M of the heat exchanger if the difference is less than or equal to 0.00001HXIf not, the flow areas assigned in step S6 are iteratively added until the flow area difference meets the requirement, using the above-mentioned method
The mass of the heat exchanger is determined.
S10: the total equivalent mass is calculated.
Then, the step 12 is carried out to calculate the total equivalent mass; according to the air-entraining demand utilization formula
Calculating the corresponding compensation loss of the bleed air, and obtaining the turbine mass M according to the power output of the turbineTAnd using formulas
Calculating out corresponding compensation loss, and obtaining the mass M of the compressor according to the power consumption of the compressorCAnd using formulas
Calculating the corresponding compensation loss, and utilizing a formula according to the fuel oil demand
Calculating the compensation loss corresponding to the fuel oil consumption according to the mass M of the heat exchangerHXUsing formulas
And calculating the corresponding compensation loss.
S11: and judging whether the total equivalent mass is minimum, if so, ending.
Then, step S11 is performed to determine whether the total equivalent mass is minimum, and further determine whether the target value of the second step of the optimization design satisfies the preset optimal condition.
If the preset optimal condition is met, ending; if the preset optimal conditions are not met, the step S12 is entered to update the optimized variable values of the second step of the optimized design, namely the outlet temperature of the compressor, the minimum pressure of the system and the initial flow of the high-temperature heat source, and the step S2 is returned to perform iterative calculation to repeat the optimization process until the optimal conditions are met.
The algorithms used in the first-step optimization design and the second-step optimization design can be optimization design algorithms such as a step-by-step quadratic programming method, a non-dominated sorting genetic algorithm with an elite strategy and the like.
S12: if not, the optimization variable value is updated, and the step S2 is returned until the total equivalent mass is minimum.
Fig. 2 is a schematic structural diagram of an aircraft thermal management system optimization system according to an embodiment of the present invention, and as shown in fig. 2, the system includes:
the data acquisition module is used for acquiring the flight altitude, Mach number, refrigerating capacity and power supply demand of the aircraft;
the assignment module is used for determining an initial value of a cold cycle and an initial flow of a high-temperature heat source; the initial values of the cold cycle are: compressor outlet temperature and system minimum pressure;
the preliminary temperature and pressure calculation module of the thermodynamic cycle of the air refrigeration system is used for calculating the preliminary temperature and pressure of the thermodynamic cycle of the air refrigeration system based on the initial value of the cold cycle and the initial flow of the high-temperature heat source;
the air refrigeration working medium mass flow and heat exchange capacity determination module is used for determining the mass flow of the air refrigeration working medium and the heat exchange capacity of each heat exchanger based on the preliminary temperature and pressure of the thermodynamic cycle of the air refrigeration system;
the optimization module is used for optimizing the geometric dimension of the heat exchanger by taking the minimum mass of the heat exchanger as a target;
the resistance calculation module is used for calculating the resistance of the heat exchanger based on the geometric dimension of the heat exchanger;
the first judgment module is used for judging whether the temperature and the pressure of each point of the refrigerating system are matched or not, and if so, executing the next step;
the correction module is used for correcting the pressure of the air refrigeration system and returning the pressure to the preliminary temperature and pressure calculation module of the thermodynamic cycle of the air refrigeration system when the pressure of the air refrigeration system is not matched with the pressure of the air refrigeration system;
the device comprises a bleed air demand, turbine power output, compressor power consumption, fuel oil demand and heat exchanger weight calculation module, a heat exchanger weight calculation module and a control module, wherein the bleed air demand, the turbine power output, the compressor power consumption, the fuel oil demand and the heat exchanger weight calculation module are used for calculating the bleed air demand, the turbine power output, the compressor power consumption, the fuel oil demand and the heat exchanger weight;
the total equivalent mass calculating module is used for calculating the total equivalent mass;
the second judgment module is used for judging whether the total equivalent mass is minimum or not, and if so, ending the process;
and the updating optimization module is used for updating the optimization variable value and returning to the assignment module until the total equivalent quality is minimum.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (8)
1. A method of optimizing an aircraft thermal management system, the method comprising:
s1: acquiring the flight altitude, Mach number, refrigerating capacity and power supply demand of an aircraft;
s2: determining an initial value of a cold cycle and an initial flow of a high-temperature heat source; the initial value of the cold cycle is: compressor outlet temperature and system minimum pressure;
s3: calculating the initial temperature and pressure of the thermodynamic cycle of the air refrigeration system based on the initial value of the cold cycle and the initial flow of the high-temperature heat source;
s4: determining the mass flow of the air refrigeration working medium and the heat exchange capacity of each heat exchanger based on the preliminary temperature and the pressure of the thermodynamic cycle of the air refrigeration system;
s5: optimizing the geometric dimension of the heat exchanger by taking the minimum mass of the heat exchanger as a target;
s6: calculating the resistance of the heat exchanger based on the geometric dimension of the heat exchanger;
s7: judging whether the temperature and pressure of each point of the refrigeration system are matched, and if so, executing the next step;
s8: if not, correcting the pressure of the air refrigeration system, and returning to the step S3;
s9: calculating the air entraining demand, the turbine power output, the compressor power consumption, the fuel oil demand and the heat exchanger weight;
s10: calculating the total equivalent mass;
s11: judging whether the total equivalent mass is minimum, if so, ending;
s12: if not, the optimization variable value is updated, and the step S2 is returned until the total equivalent mass is minimum.
2. The aircraft thermal management system optimization method of claim 1, wherein the air refrigeration system thermodynamic cycle comprises: closed air refrigeration system thermodynamic cycle and open air refrigeration system thermodynamic cycle.
3. The aircraft thermal management system optimization method according to claim 2, characterized in that, with the aim of minimizing the mass of the heat exchangers, the following formula is used in particular for optimizing the geometric dimensions of the heat exchangers:
determining an objective function:
wherein M isHXRepresents the total mass of the heat exchanger, kg;
representing an optimal design variable matrix:
scwidth of the cold fluid side fin, hcFor the height in the cold fluid side fincFor the staggered length of the cold fluid side fins, tf,cThickness of the cold fluid side fin, tcThickness of cold fluid side baffle plate, shWidth of the side fin of the hot fluid, hhIs the height in the hot fluid side fin, /)hFor the staggered length of the cold fluid side fins, tf,hThickness of the cold fluid side fin, thIs the cold fluid side baffle thickness, L is the non-flow direction length;
the constraint conditions are as follows:
LB for optimal design variable matrix
UB is an optimally designed variable matrix
Upper limit matrix of, Δ PcPressure drop, Δ P, of cold fluid side heat exchangermax,cMaximum pressure drop, Δ P, of cold fluid side heat exchangerhPressure drop, Δ P, of heat exchanger on heat flow sidemax,hThe maximum pressure drop of the heat exchanger on the heat fluid side.
4. The aircraft thermal management system optimization method according to claim 1, wherein said calculating the resistance of a heat exchanger, based on the geometry of said heat exchanger, comprises in particular the following steps:
using formulas
Calculating the equivalent diameter of the heat exchanger, wherein s is the width of the fin, h is the inner height of the fin, l is the staggered length of the fin, and tfIs the fin thickness;
calculating Re based on the equivalent diameter of the heat exchanger:
wherein v is the fluid flow rate and η is the fluid viscosity; ρ is the fluid density;
calculating the resistance of the heat exchanger based on the Re:
wherein, gmIs the mass flow rate of the fluid; a. thecAnd AaRespectively a heat exchanger core andcalculated cross-sectional flow area at each local resistance.
5. An aircraft thermal management system optimization system, the optimization system comprising:
the data acquisition module is used for acquiring the flight altitude, Mach number, refrigerating capacity and power supply demand of the aircraft;
the assignment module is used for determining an initial value of a cold cycle and an initial flow of a high-temperature heat source; the initial value of the cold cycle is: compressor outlet temperature and system minimum pressure;
the preliminary temperature and pressure calculation module of the thermodynamic cycle of the air refrigeration system is used for calculating the preliminary temperature and pressure of the thermodynamic cycle of the air refrigeration system based on the initial value of the cold cycle and the initial flow of the high-temperature heat source;
the air refrigeration working medium mass flow and heat exchange capacity determination module is used for determining the mass flow of the air refrigeration working medium and the heat exchange capacity of each heat exchanger based on the preliminary temperature and pressure of the thermodynamic cycle of the air refrigeration system;
the optimization module is used for optimizing the geometric dimension of the heat exchanger by taking the minimum mass of the heat exchanger as a target;
the resistance calculation module is used for calculating the resistance of the heat exchanger based on the geometric dimension of the heat exchanger;
the first judgment module is used for judging whether the temperature and the pressure of each point of the refrigeration system are matched or not, and if so, executing the next step;
the correction module is used for correcting the pressure of the air refrigeration system when the pressure is not matched with the pressure, and returning the pressure to the preliminary temperature and pressure calculation module of the thermodynamic cycle of the air refrigeration system;
the device comprises a bleed air demand, turbine power output, compressor power consumption, fuel oil demand and heat exchanger weight calculation module, a power consumption calculation module and a heat exchanger weight calculation module, wherein the bleed air demand, the turbine power output, the compressor power consumption, the fuel oil demand and the heat exchanger weight calculation module are used for calculating the bleed air demand, the turbine power output, the compressor power consumption, the fuel oil demand and the heat exchanger weight;
the total equivalent mass calculating module is used for calculating the total equivalent mass;
the second judgment module is used for judging whether the total equivalent mass is minimum or not, and if so, ending the process;
and the updating optimization module is used for updating the optimization variable value and returning to the assignment module until the total equivalent mass is minimum if the optimization variable value is not the same as the total equivalent mass.
6. The aircraft thermal management system optimization system of claim 5, wherein the air refrigeration system thermodynamic cycle comprises: closed air refrigeration system thermodynamic cycle and open air refrigeration system thermodynamic cycle.
7. The aircraft thermal management system optimization system of claim 6, wherein the optimization module employs in particular the following formula:
determining an objective function:
wherein M isHXRepresents the total mass of the heat exchanger, kg;
representing an optimal design variable matrix:
scwidth of the cold fluid side fin, hcFor the height in the cold fluid side fincFor the staggered length of the cold fluid side fins, tf,cThickness of the cold fluid side fin, tcThickness of cold fluid side baffle plate, shWidth of the side fin of the hot fluid, hhIs the height in the hot fluid side fin, /)hFor the staggered length of the cold fluid side fins, tf,hThickness of the cold fluid side fin, thIs the cold fluid side baffle thickness, L is the non-flow direction length;
the constraint conditions are as follows:
LB for optimal design variable matrix
UB is an optimally designed variable matrix
Upper limit matrix of, Δ PcPressure drop, Δ P, of cold fluid side heat exchangermax,cMaximum pressure drop, Δ P, of cold fluid side heat exchangerhPressure drop, Δ P, of heat exchanger on heat flow sidemax,hThe maximum pressure drop of the heat exchanger on the heat fluid side.
8. The aircraft thermal management system optimization system of claim 5, wherein the drag calculation module comprises in particular the steps of:
using formulas
Calculating the equivalent diameter of the heat exchanger, wherein s is the width of the fin, h is the inner height of the fin, l is the staggered length of the fin, and tfIs the fin thickness;
calculating Re based on the equivalent diameter of the heat exchanger:
wherein v is the fluid flow rate and η is the fluid viscosity; ρ is the fluid density;
calculating the resistance of the heat exchanger based on the Re:
wherein, gmIs the mass flow rate of the fluid; a. thecAnd AaThe calculated cross-sectional flow areas for the core and each local resistance are provided separately.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114997597A (en) * | 2022-05-12 | 2022-09-02 | 南京航空航天大学 | Evaluation method of aircraft thermal management system |
| CN116526590A (en) * | 2023-06-26 | 2023-08-01 | 中国航空工业集团公司金城南京机电液压工程研究中心 | Electric heating integrated system of on-board high-power equipment and management method |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114997597A (en) * | 2022-05-12 | 2022-09-02 | 南京航空航天大学 | Evaluation method of aircraft thermal management system |
| CN114997597B (en) * | 2022-05-12 | 2023-07-18 | 南京航空航天大学 | Evaluation method of aircraft thermal management system |
| CN116526590A (en) * | 2023-06-26 | 2023-08-01 | 中国航空工业集团公司金城南京机电液压工程研究中心 | Electric heating integrated system of on-board high-power equipment and management method |
| CN116526590B (en) * | 2023-06-26 | 2023-09-01 | 中国航空工业集团公司金城南京机电液压工程研究中心 | Electric heating integrated system of on-board high-power equipment and management method |
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