A variable cycle engine thermal management system model and modeling method thereof

Abstract

The present invention discloses a variable cycle engine thermal management system model and a modeling method thereof. The thermal management system model includes several subsystem models and a flight mission parameter input module. The several subsystem models include a variable cycle engine subsystem model and other subsystem models. The flight mission parameter input module is used to determine the engine working state and the thermal load size of the engine subsystem by given input parameters. The several subsystem models are coupled to each other based on the mass and energy transfer relationship, and the node temperatures of other subsystem models are obtained according to the input parameters. According to the component models of the subsystems, the thermal management system model is obtained by coupling, and then by setting simulation calculation parameters, the change characteristics of the system node temperature can be effectively analyzed. Simulation calculations are performed for the engine in different working modes and at different operating points, and the influence of the engine subsystem on the node temperatures of other subsystems is analyzed, so that the steady-state working state of the system can be effectively monitored.

Description

Technical Field

[0001] The invention relates to a variable cycle engine, and in particular to a variable cycle engine thermal management system model and a modeling method thereof. Background Art

[0002] Advanced fighter jets are developing towards high maneuverability, stealth, and cruise economy. The performance of the engine directly affects the overall performance of the aircraft. The variable cycle engine changes its thermodynamic cycle parameters by adjusting the variable geometry mechanism, so that the engine has good performance in a wider flight envelope, which can provide advanced fighter jets with good maneuverability and long-range cruise economy. It is one of the most promising engines at present. However, the number and power of airborne equipment are constantly increasing, and the thermal load of the whole machine has doubled, which seriously affects the performance improvement of the whole machine. Therefore, it is necessary to study the comprehensive thermal / energy management system to solve the thermal problems faced by advanced engines.

[0003] At present, the research on variable cycle engines focuses on the engine itself, mainly involving the research on component-level modeling and simulation methods, control laws, modal conversion, and the influence of variable geometry mechanisms on engine performance. Few literatures mention the research on its integrated thermal management system. As one of the advanced research directions of aviation engines, the design technology of various aspects of variable cycle engines is not yet mature. Preliminary research on the design technology of the integrated thermal management system of variable cycle engines is exploratory and can provide a certain reference for the research on the thermal management system of variable cycle engines. Summary of the invention

[0004] Purpose of the invention: In view of the above shortcomings, the present invention provides a variable cycle engine thermal management system model that comprehensively considers the variable cycle engine and the airborne system and studies the energy transfer mechanism between the engine and related subsystems.

[0005] The present invention also provides a modeling method for a variable cycle engine thermal management system model.

[0006] Technical solution: To solve the above problems, the present invention adopts a variable cycle engine thermal management system model, including several subsystem models and a flight mission parameter input module. The several subsystem models include a variable cycle engine subsystem model and other subsystem models. The flight mission parameter input module is used to give the input parameters of the variable cycle engine subsystem model, determine the engine working state, and determine the size of the engine subsystem thermal load; the several subsystem models are coupled with each other based on the mass and energy transfer relationship, and the node temperatures of other subsystem models are obtained according to the input parameters of the variable cycle engine subsystem model.

[0007] Furthermore, the flight mission parameters include flight parameters such as the current engine flight altitude, flight Mach number, and adjustable mechanism parameters for determining the engine operating mode.

[0008] The present invention also adopts a modeling method for a variable cycle engine thermal management system, comprising the following steps:

[0009] (1) Construct the overall structure of the thermal management system; according to the composition of the variable cycle engine system, the working principles of each subsystem and the energy matching relationship, the thermal management system model is divided into three layers: components, subsystems and the overall system. The overall system includes several subsystems, and each subsystem includes several components;

[0010] (2) Establish a variable cycle engine subsystem model based on the working characteristics of the variable cycle engine and the functional characteristics of each component;

[0011] (3) Based on the energy transfer relationship between subsystems in the thermal management system, and in accordance with the functions, structural characteristics, and component mathematical models of the subsystems, the subsystem models of the thermal management system other than the variable cycle engine subsystem are established;

[0012] (4) Establishing a flight mission parameter input module based on the relationship between the variable cycle engine subsystem thermal load and the flight mission parameters;

[0013] (5) Based on the mass and energy transfer relationship between the variable cycle engine subsystem and other subsystems, combined with the flight mission parameter input module, a multi-system coupled thermal management system model is built.

[0014] Furthermore, the variable cycle engine subsystem model includes aerodynamic thermodynamic models of various components of the variable cycle engine, a variable geometry mechanism characteristic calculation model of the variable cycle engine, and a common working equation solution model of the engine.

[0015] Furthermore, the aerodynamic thermodynamic models of the various components of the variable cycle engine include an aerodynamic thermodynamic model of the air inlet, thermodynamic models of the compression components and turbine components, and a thermodynamic model of the combustion chamber.

[0016] Furthermore, the inlet aerodynamic thermodynamic model includes:

[0017] Total temperature at the inlet:

[0018] Total pressure at the inlet:

[0019] Air flow velocity at the inlet section:

[0020] Total pressure at the inlet port outlet: P t,2 =σ i ×Pt,1

[0021] Total temperature at the inlet outlet: T t,2 =T t,1

[0022] Among them, T s,0 is the static temperature of the atmosphere, k is the adiabatic index, Ma is the Mach number, P s,0 is the atmospheric static pressure, Ma0 is the Mach number given in the atmospheric environment, R is the gas constant, σ i is the total pressure recovery coefficient at the inlet outlet.

[0023] Furthermore, the thermodynamic models of the compression component and the turbine component include:

[0024] Total temperature at compression component outlet:

[0025] Total pressure at the outlet of compression components: P t,C,out =P t,C,in ×π

[0026] Power consumed by the compression component: N C =W a,in ×c p (T t,C,out -T t,C,in )

[0027] Turbine component outlet temperature:

[0028] Total pressure at turbine component outlet: P t,T,out =P t,T,in / π

[0029] Work output of turbine components: N T =W g,out ×c' P ×(T t,T,in -T t,T,out )

[0030] Among them, T t,C,in is the total temperature at the inlet of the compression part, P t,C,in is the total pressure at the inlet of the compression component, T t,T,in is the total temperature at the turbine component inlet, P t,T,in is the total pressure at the turbine component inlet, π is the component pressure ratio, η is the component efficiency, W a,in is the actual inlet air flow of the compression component, c p is the specific heat capacity of air in the compression part, k is the air adiabatic index, W g,out is the actual outlet gas flow of the turbine component, c' p is the specific heat capacity of gas in turbine components, k' is the gas adiabatic index;

[0031] Furthermore, in the variable geometry mechanism characteristic calculation model of the variable cycle engine, the variable mechanism blade angle is adjusted according to different working states.

[0032] Furthermore, the engine common working equation solution model includes a steady-state mathematical model and a dynamic mathematical model;

[0033] The steady-state mathematical model includes: fan and CDFS flow balance, high-pressure turbine inlet section flow balance, low-pressure turbine inlet section flow balance, tail nozzle flow balance, rear mixing chamber static pressure balance, high-pressure shaft power balance, and low-pressure shaft power balance;

[0034] The dynamic mathematical model:

[0035] The high-pressure shaft power balance equation is not satisfied, but the rotor dynamics equation of the pressure rotor is satisfied:

[0036]

[0037] At the same time, the low-pressure shaft power balance equation is not satisfied, but the rotor dynamics equation of the low-pressure rotor is satisfied:

[0038]

[0039] Among them, N HT is the high pressure turbine power, η HT is the high pressure turbine efficiency, N CDFS Core driver fan level power, N HC is the high pressure compressor power, N ext To extract work power, J h is the high pressure rotor moment of inertia, n h is the high pressure rotor speed, N LT is the low-pressure turbine power, η LT is the low-pressure turbine efficiency, N F1 is the power of the external fan, N F2 is the power of the internal fan, J l is the low pressure rotor moment of inertia, n l is the low pressure rotor speed.

[0040] Furthermore, other subsystem models in the thermal management system include a fuel subsystem model, a lubricating oil subsystem model, and an environmental control subsystem model; the fuel subsystem model includes a fuel tank mass conservation model, a fuel tank energy conservation model, cross-flow heat exchanger efficiency, pump effective power, outlet temperature through the pump, and outlet pressure through the pump; the lubricating oil subsystem model includes lubricating oil cooling high / low pressure shaft heat and lubricating oil temperature; the environmental control subsystem includes the mass flow rate of bleed air and the temperature of ram air.

[0041] Beneficial effect: Compared with the prior art, the significant advantage of the present invention is that a thermal management system model is obtained by coupling the component models of the variable cycle engine subsystem and related subsystems. Based on the obtained thermal management system model, simulation calculation parameters are set, which can effectively analyze the changing characteristics of the system node temperature. Simulation calculations are performed on the engine in different working modes and at different operating points to analyze the influence of the engine subsystem on the node temperatures of other subsystems, so as to effectively monitor the steady-state working state of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic diagram of the overall structure of the integrated thermal management system of the medium-variable cycle engine of the present invention;

[0043] Figure 2 It is a schematic diagram of the structure of the fuel subsystem in the present invention;

[0044] Figure 3 It is a schematic diagram of the structure of the lubricating oil subsystem in the present invention;

[0045] Figure 4 It is a schematic diagram of the structure of the environmental control subsystem in the present invention;

[0046] Figure 5 It is a Simulink diagram of the coupling simulation model of the whole machine system of the present invention;

[0047] Figure 6 The influence of altitude and Mach number on the fuel temperature at the combustion chamber inlet;

[0048] Figure 7 In dual-fill mode, the flight altitude is 6000m, and the temperature of the fuel subsystem node changes with the Mach number;

[0049] Figure 8 In dual-containment mode, the flight altitude is 6000m, and the temperature of the lubricating oil subsystem node changes with the Mach number;

[0050] Fig. 9 In single culvert mode, the flight altitude is 12000m, and the temperature of the fuel subsystem node changes with the Mach number;

[0051] Fig.10 It is a single culvert mode, the flight altitude is 12000m, and the node temperature of the lubricating oil subsystem changes with the Mach number. DETAILED DESCRIPTION

[0052] Example 1

[0053] like Figures 1 to 4As shown, a variable cycle engine thermal management system model in this embodiment takes a dual-external variable cycle engine as the research object, builds a multi-system coupled thermal management system model, studies the steady-state characteristics of its thermal management system, analyzes the influence of the engine subsystem on the node temperatures of other subsystems under different working modes, and monitors the steady-state working state of the system. The thermal management system model includes: a variable cycle engine subsystem, a fuel subsystem, a lubricating oil subsystem and an environmental control subsystem model, and a flight mission parameter input module; the flight mission parameter input module is used to give the input parameters of the variable cycle engine subsystem model, determine the engine working state, and determine the size of the engine subsystem thermal load; several subsystem models are coupled to each other, and the node temperatures of other subsystem models are obtained according to the input parameters of the variable cycle engine subsystem model.

[0054] The thermal management system model is divided into three layers: components, subsystems and overall system. The thermal management system is composed of several subsystems, and each subsystem is composed of several components. The thermal management system model considers the main composition of the thermal management system, the working principle of each subsystem, and the energy input and output relationship of each subsystem. The thermal management system has a clear structure and good versatility and extensibility.

[0055] The variable cycle engine subsystem model includes the aerodynamic thermodynamic model of engine components, the component characteristic interpolation calculation model, the variable geometry mechanism characteristic calculation model, and the engine common working equation steady-state and dynamic solution model. Based on the variable cycle engine subsystem model, the working parameters of each component of the engine subsystem and the subsystem thermal load can be obtained.

[0056] According to the working characteristics of the variable cycle engine, the models of other subsystems of thermal management are obtained. According to the structural characteristics, functions and working principles of different components in the thermal management subsystem, the calculation models including the fuel subsystem, lubricating oil subsystem and environmental control subsystem are obtained. The relevant subsystems work in coordination with the engine subsystem, and the thermal load of the overall system is transferred between each subsystem. The component models of other subsystems of thermal management include the fuel tank model, heat exchanger model, pump model and air induction model of the environmental control subsystem.

[0057] The flight mission parameter input module includes flight parameters such as the current engine flight altitude, flight Mach number, and adjustable mechanism parameters that determine the engine operating mode. Adjustable mechanism parameters include variable mechanism blade angles and duct ejector opening sizes. The engine steady-state parameters are set according to calculation requirements. The engine steady-state parameters include engine design point calculation parameters and non-design point typical operating condition calculation parameters. By giving different flight mission parameters, the engine operating state is determined, the overall system energy matching relationship is analyzed, and the system heat load is reasonably transferred, utilized, and dissipated.

[0058] Based on the above subsystem-level models, according to the mass and energy transfer relationship between subsystems, the thermal management system model is obtained by multi-system coupling. The mass flow and energy transfer relationship between subsystems in the thermal management system coupling model realize real-time data transmission through the interface. Set the flight mission parameters, adjust the fuel volume, keep the low-pressure rotor speed constant, and analyze the characteristics of the variable cycle engine thermal management system under different working modes and different operating points according to the thermal management system model.

[0059] Example 2

[0060] The constant-pressure specific heat and adiabatic isentropic index of the gas do not change with temperature; the total flow pressure loss of the gas is calculated by the loss coefficient; the flow of the working fluid in the engine is quasi-one-dimensional flow; only the key components of the system are considered during the system modeling process; the thermal load of the hydraulic oil and the thermal load of the electronic equipment are simplified to fixed values.

[0061] A modeling method for a variable cycle engine thermal management system in this embodiment includes the following steps:

[0062] (1) Construct the overall structure of the thermal management system; according to the composition of the variable cycle engine system, the working principle of each subsystem and the energy matching relationship, the thermal management system model mainly includes the variable cycle engine subsystem, fuel subsystem, lubricating oil subsystem and environmental control subsystem, such as Figure 1 As shown, the subsystems work together, and the energy of the overall system is transferred, utilized, and dissipated between the systems. The engine subsystem, as a source of power energy, is also the main part of the thermal load of the thermal management system. The lubricating oil subsystem absorbs the thermal load of the engine subsystem and exchanges heat with other subsystems through the heat exchanger. The fuel subsystem provides sufficient fuel in real time and acts as the main heat sink to absorb the thermal load of other systems. The environmental control subsystem is used to maintain a constant cabin temperature and cool precision electronic equipment.

[0063] The modeling assumptions are that the constant pressure specific heat and adiabatic isentropic index of the gas do not change with the change of temperature; the total pressure loss of the gas flow is calculated by the loss coefficient; the flow of the working fluid in the engine is a quasi-one-dimensional flow; only the key components of the system are considered during the system modeling process; the thermal load of the hydraulic oil and the thermal load of the electronic equipment are simplified to fixed values. Based on the modular modeling method, the thermal management system model is divided into three layers: components, subsystems and the overall system. The overall system includes several subsystems, and each subsystem includes several components;

[0064] Definition and description of the main parameters used:

[0065]

[0066]

[0067] (2) Establish a variable cycle engine subsystem model to calculate the operating parameters of each component of the engine subsystem and the thermal load of the engine subsystem. According to the operating characteristics of the variable cycle engine and the functional characteristics of each component, the variable cycle engine subsystem calculation model is established by obtaining the characteristic parameters of the variable cycle engine and using Matlab / Simulink software. The established model includes the engine component level model and the engine common working equation solution model.

[0068] (2.1) Aero-thermodynamic model of engine components

[0069] 1) Intake duct

[0070] The air temperature at sea level is T0 = 288.15K, and the corresponding air pressure is P0 = 101.325kPa. Calculate the atmospheric temperature and pressure.

[0071]

[0072]

[0073] By static temperature T s,0 and static pressure P s,0 And given the flight Mach number Ma, calculate the inlet total temperature and total pressure:

[0074]

[0075] The air flow velocity at the inlet section is:

[0076] Total pressure at the inlet port outlet: P t2 =σ i ×P t1

[0077] Total pressure recovery coefficient at the inlet outlet σ i , can be estimated approximately as follows:

[0078]

[0079] Total temperature at the inlet outlet: T t,2 =T t,1

[0080] 2) Compression and turbine component models

[0081] Relative conversion speed of components:

[0082]

[0083] According to the reduced speed n cor , the characteristic auxiliary line β is interpolated in the characteristic diagram to obtain the inlet equivalent flow rate, pressure ratio and efficiency.

[0084] W cor,map =f(n cor ,β)

[0085] π map =f(n cor ,β)

[0086] η map =f(n cor ,β)

[0087] Due to the lack of real component characteristic data, the typical characteristic diagram can be scaled using the design point parameters to establish it. In the component characteristic curve diagram, at the same auxiliary working line value and reduced speed value as the design point, the characteristic diagram reduced flow W is interpolated. cor,map,d , pressure ratio π map,d , efficiency η map,d , calculate the component characteristic curve scaling factor.

[0088] Equivalent flow: Pressure ratio: efficiency:

[0089] Actual import flow:

[0090] Component pressure ratio: π=C π (π map -1)+1

[0091] Component efficiency: η = C η η ,map

[0092] Total temperature at compression component outlet:

[0093] Total pressure at the outlet of compression components: P t,C,out =P t,C,in ×π

[0094] Power consumed by the compression component: N C =W a,in ×c p (T t,C,out -T t,C,in )

[0095] Turbine component outlet temperature:

[0096] Total pressure at turbine component outlet: P t,T,out =P t,T,in / π

[0097] Work output of turbine components: N T =W g,out ×c' P×(T t,T,in -T t,T,out )

[0098] Among them, T t,C,in is the total temperature at the inlet of the compression part, P t,C,in is the total pressure at the inlet of the compression component, T t,T,in is the total temperature at the turbine component inlet, P t,T,in is the total pressure at the turbine component inlet, π is the component pressure ratio, η is the component efficiency, W a,in is the actual inlet air flow of the compression component, c p is the specific heat capacity of air in the compression part, k is the air adiabatic index, W g,out is the actual outlet gas flow of the turbine component, c' p is the specific heat capacity of the gas in the turbine component, and k' is the gas adiabatic index.

[0099] 3) Combustion chamber

[0100] Known inlet total temperature T t,31 , total inlet pressure P t,31 , fuel mass flow rate W fuel,b , inlet air mass flow rate W a,31 , total pressure loss coefficient σ at the combustion chamber design point b,d , design point combustion chamber efficiency η b,d .

[0101] Export flow: W a,4 =W a,31 +W fuel,b

[0102] Total pressure at combustion chamber outlet: P t,4 =P t,31 ×σ b

[0103] Combustion chamber total pressure recovery coefficient:

[0104] Total outlet temperature T t,4 :

[0105] Combustion chamber efficiency η b :log(1-η b )=a+b×log(Ω / Ω d )

[0106] Combustion efficiency η b Related to the combustion chamber load Ω, it is defined as:

[0107] (2.2) Calculation model of variable geometry mechanism characteristics

[0108] In addition to adjustable modes, the variable cycle engine also uses variable geometry compression components and variable geometry turbine components. According to different working conditions, the angle of the variable mechanism blades is adjusted, allowing it to distribute airflow over a larger range to adapt to multi-mode and multi-working conditions.

[0109] The influence of blade angle on the characteristics of variable mechanisms is generally estimated using an empirical formula:

[0110] π=(π map -1)×(1+α·c π / 100)+1

[0111] W=W map ×(1+α·c W / 100)

[0112] η=η map ×[1-c η (α / 100) 2 ]

[0113] At the design state point, the variable mechanism blade angle is set to 0°. When the engine deviates from the design point, the variable blade angle is adjusted. The influence of the blade angle on the component mass flow, pressure ratio, efficiency and other characteristic parameters under the current situation needs to be calculated through approximate equations to obtain the non-design point characteristic curve, and then interpolation is performed to calculate the component characteristic parameters under the current blade angle.

[0114] (2.3) Engine joint working equation solution model

[0115] The engine joint working equation is a set of equations that reflects the joint working state of various engine components. The joint working equation is divided into steady-state joint working equation and dynamic joint working equation, which mainly include flow balance, static pressure balance and power balance equation. When the engine is working dynamically, the power balance equation is replaced by the rotor dynamics equation.

[0116] 1) Steady-state mathematical model

[0117] Fan and CDFS flow balance: W a,2,in -W a,13 -W a,21 =0

[0118] High-pressure turbine inlet cross-sectional flow balance: W g,4 -W a,3,out -W fuel =0

[0119] Low-pressure turbine inlet cross-sectional flow balance: W g,45,in -W g,45 =0

[0120] Tail nozzle flow balance: Wg,9 -W g,8 =0

[0121] Static pressure balance of rear mixing chamber: P s,163 -P s,63 =0

[0122] High-pressure shaft power balance equation: N HT η HT -N CDFS -N HC -N ext =0

[0123] Low-pressure shaft power balance equation: N LT η LT -N F1 -N F2 =0

[0124] 2) Dynamic mathematical model

[0125] When the operating parameters change, the engine is in an unbalanced state, and the power balance equations of the high and low pressure shafts will no longer be satisfied. Therefore, the power balance equation is replaced by the rotor dynamics equations of the high and low pressure rotors:

[0126]

[0127]

[0128] Combined with the speed at the previous moment, the rotor speed at the next moment is calculated:

[0129]

[0130] (3) Establish models of other subsystems of thermal management. Based on the energy transfer relationship between subsystems in the thermal management system, and in accordance with the functions, structural characteristics, and component mathematical models of the subsystems, establish models of other subsystems of the thermal management system except the variable cycle engine subsystem. The other subsystem models established include the fuel subsystem model, the lubricating oil subsystem model, and the environmental control subsystem model.

[0131] (3.1) Fuel subsystem model

[0132] The fuel subsystem mainly includes the fuel tank, fuel pump, fuel filter, heat exchanger, fuel distributor and valve. When the fuel flows, the space inside the fuel tank is large and the flow speed is slow. It is assumed that there is no phase change during the flow process.

[0133] 1) Fuel tank

[0134] Fuel tank mass conservation equation:

[0135]

[0136] In the formula, Fuel consumption quality, and are the inlet and outlet mass flow rates of the fuel tank respectively.

[0137] Fuel tank energy conservation equation:

[0138]

[0139] Where M0 is the initial fuel mass in the tank, T fuel is the fuel temperature, Fuel consumption quality, and are the inlet and outlet mass flows of the fuel tank respectively, Exchange heat for fuel.

[0140] 2) Heat exchanger

[0141] A single-phase single-flow cross-flow heat exchanger in which the two fluids are non-mixed is used, and the model is built according to the efficiency-number of heat transfer units (η-NTU) method.

[0142] Calculate the number of heat transfer units NTU based on the given heat exchanger heat transfer area and heat transfer coefficient:

[0143]

[0144] Empirical formula for calculating the efficiency of cross-flow heat exchanger:

[0145]

[0146] Heat exchanger efficiency definition:

[0147]

[0148] In the formula, Φ is the heat flow, subscript 1 represents the hot side, 2 represents the cold side, min represents the minimum value, max represents the maximum value, superscript ' represents the inlet, and ' represents the outlet. According to the heat flow of the fluid on both sides of the heat exchanger, the outlet parameters of the fluid on both sides are calculated by the above formula.

[0149] 3) Pump

[0150] Ignoring the pump's rotational inertia, a quasi-steady-state calculation model for the pump was established. According to the flow rate entering the pump, the effective pressure head H and total efficiency η under the volume flow rate were interpolated on the characteristic curve. pump .

[0151] H=f(V pump ,n)η pump =f(V pump ,n)

[0152] Pump effective power Ne :N e =V pump ρHg

[0153] Outlet temperature through the pump:

[0154] Outlet pressure through the pump:

[0155] (3.2) Lubricating oil subsystem model establishment

[0156] The lubricating oil subsystem mainly includes the lubricating oil tank, lubricating oil pump, fuel / lubricating oil heat exchanger and lubricating oil / air heat exchanger.

[0157] The lubricating oil circulates without generating loss, therefore, the mass flow rate at the lubricating oil tank outlet is equal to the mass flow rate at the tank inlet, and the mass of the lubricating oil in the tank remains unchanged.

[0158] Lubricating oil cools high and low pressure shaft heat The calculation formula is:

[0159]

[0160] Where, T hotpart is the hot end component temperature, T oil It is the lubricating oil temperature at the oil filter outlet.

[0161] Lubricating oil temperature calculation:

[0162]

[0163] In the formula, is the lubricating oil quality of the heat exchange node.

[0164] (3.3) Establishment of environmental control subsystem model

[0165] The environmental control subsystem includes the bleed air flow control valve, bleed air / air heat exchanger, bleed air / fuel heat exchanger, cooling turbine, and cockpit electronic equipment compartment.

[0166] The mass flow of bleed air is controlled by valves depending on the heat load in the cockpit or electronics compartment.

[0167]

[0168] Where, T Cockpit is the cockpit temperature, which is generally the comfortable temperature for human body and is maintained between 288 and 300K. in is the air temperature entering the electronic equipment compartment, set to 275K, Q Cockpit is the heat load of the cabin.

[0169] Ram air temperature Tr It is related to the flight altitude H and the Mach number Ma, and the relationship is as follows:

[0170]

[0171] The ram air first cools the fuel entering the fuel return tank in the fuel circuit, and then exchanges heat with the compressor exhaust. The cooled exhaust passes through the air / fuel heat exchanger and enters the cooling turbine for further cooling.

[0172] (4) According to the relationship between the variable cycle engine subsystem thermal load and the flight mission parameters, a flight mission parameter input module is established; this module is used to determine the engine subsystem thermal load given the input parameters of the simulation calculation. The flight mission parameters include the current engine flight altitude, flight Mach number and other flight parameters as well as the adjustable mechanism parameters that determine the engine operating mode. The adjustable mechanism parameters include the variable mechanism blade angle and the duct ejector opening size. The engine steady-state simulation parameters can be set according to the simulation calculation requirements. The engine steady-state simulation parameters include the engine design point parameters and the non-design point typical operating condition parameters. By giving different flight mission parameters, the engine operating state is determined, the overall system energy matching relationship is analyzed, and the system thermal load is reasonably transferred, utilized and dissipated.

[0173] (5) Based on the above subsystem-level models, according to the mass and energy transfer relationship between the variable cycle engine subsystem and other subsystems, combined with the flight mission parameter input module, a multi-system coupled thermal management system model is built to analyze the steady-state characteristics of the thermal management system. Set the flight mission parameters and the system steady-state simulation calculation parameters, perform simulation calculations for the engine in different working modes and at different operating points, analyze the influence of the engine subsystem on the node temperature of other subsystems, and monitor the steady-state working status of the system.

[0174] Taking the steady-state simulation calculation of the variable cycle engine thermal management system as an example, the implementation process of the present invention is described in detail.

[0175] According to the modeling method of the present invention, based on the general simulation platform Matlab / Simulink, according to the structural characteristics, functions, working principles and flow heat transfer mechanisms of different components in each subsystem, based on the basic relationship between the mass conservation equation and the energy conservation equation, a modeling system is constructed from three levels: component level, subsystem level and system level. Figure 5 The coupled simulation model of the whole machine system shown in the figure performs steady-state calculation on the simulation model and analyzes the regular characteristics of the subsystem node temperature changing with the working conditions under different working modes of the variable cycle engine, which can be used to monitor the steady-state working state of the system.

[0176] Set steady-state simulation parameters, set the electronic equipment heat load to 50kW, hydraulic system heat load to 30kW, lubricating oil system heat load to 10kW, cockpit heat load to 5kW; the initial total fuel volume of the fuel tank is 3000kg, the initial fuel temperature is 300K, and the fuel tank outlet flow rate is 5kg / s; the initial total lubricating oil volume of the lubricating oil tank is 50kg, the initial lubricating oil temperature is 300K, and the lubricating oil tank outlet flow rate is 5kg / s. The system steady-state calculation includes design point and non-design point calculations. The design point flight altitude H = 0m, and the flight Mach number Ma = 0. For the non-design point calculation parameters, select the flight altitudes of 6000m and 12000m respectively, the flight Mach number range is 0~1.6Ma, and the change from subsonic to supersonic speeds, and perform calculations for the two working modes of double culvert mode and single culvert mode respectively.

[0177] Figure 6 The fuel temperature at the combustion chamber inlet changes. At the same altitude, the fuel temperature increases with the increase of Mach number. At the same flight Mach number, the fuel temperature decreases with the increase of altitude. The main reason is that the change of fuel temperature is mainly affected by the thermal load of the engine subsystem. When the Mach number increases and the altitude decreases, while keeping the low-pressure rotor speed constant, the temperature and pressure of the engine inlet air increase, the relative conversion speed of the low-pressure rotor decreases, and the fan inlet equivalent flow rate decreases slightly. The actual inlet flow rate increases with the increase of the temperature and pressure of the inlet air. At this time, the fuel flow required by the combustion chamber increases, and the workload of each engine component increases, resulting in an increase in the temperature of the entire system.

[0178] Figure 7-8 The figure shows the change of the node temperature of the fuel and lubricating oil subsystem with the Mach number in the dual-sump mode of the engine at a flight altitude of 6000m. At the same altitude, it increases with the increase of the Mach number. This is because the control law of the engine is to keep the low-pressure shaft speed constant. At the same altitude, the inlet flow of the engine increases with the increase of the Mach number, and the fuel flow required for combustion in the combustion chamber increases. At the same time, the engine intake temperature and pressure increase, and the heat load of the engine subsystem increases, resulting in the temperature of each subsystem. At the same altitude, the return oil temperature of the system increases with the increase of the Mach number. The temperature rises faster after supersonic speed because the temperature of the ram air rises sharply with the increase of the Mach number.

[0179] Figure 9-10 The figure shows the change of node temperature of fuel and lubricating oil subsystem with Mach number in single sump mode. In single sump mode, the temperature change pattern of subsystem node is similar to that in dual sump mode, but the overall temperature is lower than that in dual sump mode. This is because the flight altitude is higher in single sump mode and the lower ambient air temperature has a certain cooling effect on the system, resulting in a decrease in the overall temperature.

[0180] From the steady-state simulation calculation results, it is known that at the same flight altitude, the temperature of the fuel subsystem and the lubricating oil subsystem increases with the increase of the Mach number, and at the same Mach number, it decreases with the increase of the flight altitude, which is consistent with the actual working conditions of the variable cycle engine. According to the modeling method of the present invention, the energy transfer matching relationship of each subsystem is analyzed, and a simulation calculation model of multi-system coupling is built, which can be used to guide the design technology research of the variable cycle engine thermal management system.

Claims

1. A modeling method for a variable cycle engine thermal management system, characterized in that: The following steps are involved: (1) Construct the overall structure of the thermal management system; according to the composition of the variable cycle engine system, the working principles of each subsystem and the energy matching relationship, the thermal management system model is divided into three layers: components, subsystems and the overall system. The overall system includes several subsystems, and each subsystem includes several components; (2) Establishing a variable cycle engine subsystem model based on the working characteristics of the variable cycle engine and the functional characteristics of each component; the variable cycle engine subsystem model includes an aerodynamic thermodynamic model of each component of the variable cycle engine, a variable geometry mechanism characteristic calculation model of the variable cycle engine, and a model for solving the engine common working equation; the aerodynamic thermodynamic model of each component of the variable cycle engine includes an aerodynamic thermodynamic model of the intake duct, a thermodynamic model of the compression component and the turbine component, and a thermodynamic model of the combustion chamber; The inlet aerodynamic thermodynamic model includes: Total temperature at the inlet: Total pressure at the inlet: Air flow velocity at the inlet section: Total pressure at the inlet port outlet: P t,2 =σ i ×P t,1 Total temperature at the inlet outlet: T t,2 =T t,1 Among them, T s,0 is the static temperature of the atmosphere, k is the adiabatic index, Ma is the Mach number, P s,0 is the atmospheric static pressure, Ma0 is the Mach number given in the atmospheric environment, R is the gas constant, σ i is the total pressure recovery coefficient at the inlet outlet; The compression and turbine component thermodynamic models include: Total temperature at compression component outlet: Total pressure at the outlet of compression components: P t,C,out =P t,C,in ×π Power consumed by the compression component: N C =W a,in ×c p (T t,C,out -T t,C,in ) Turbine component outlet temperature: Total pressure at turbine component outlet: P t,T,out =P t,T,in / π Work output of turbine components: N T =W g,out ×c' P ×(T t,T,in -T t,T,out ) Among them, T t,C,in is the total temperature at the inlet of the compression part, P t,C,in is the total pressure at the inlet of the compression component, T t,T,in is the total temperature at the turbine component inlet, P t,T,in is the total pressure at the turbine component inlet, π is the component pressure ratio, η is the component efficiency, W a,in is the actual inlet air flow of the compression component, c p is the specific heat capacity of air in the compression part, k is the air adiabatic index, W g,out is the actual outlet gas flow of the turbine component, c' p is the specific heat capacity of gas in turbine components, k' is the gas adiabatic index; The engine common working equation solution model includes a steady-state mathematical model and a dynamic mathematical model; The steady-state mathematical model includes: fan and CDFS flow balance, high-pressure turbine inlet section flow balance, low-pressure turbine inlet section flow balance, tail nozzle flow balance, rear mixing chamber static pressure balance, high-pressure shaft power balance equation, and low-pressure shaft power balance equation; The dynamic mathematical model includes: The high-pressure shaft power balance equation is not satisfied, but the rotor dynamics equation of the pressure rotor is satisfied: At the same time, the low-pressure shaft power balance equation is not satisfied, but the rotor dynamics equation of the low-pressure rotor is satisfied: Among them, N HT is the high pressure turbine power, η HT is the high pressure turbine efficiency, N CDFS Core driver fan level power, N HC is the high pressure compressor power, N ext To extract work power, J h is the high pressure rotor moment of inertia, n h is the high pressure rotor speed, N LT is the low-pressure turbine power, η LT is the low-pressure turbine efficiency, N F1 is the power of the external fan, N F2 is the power of the internal fan, J l is the low pressure rotor moment of inertia, n l is the low pressure rotor speed; (3) Based on the energy transfer relationship between subsystems in the thermal management system, and in accordance with the functions, structural characteristics, and component mathematical models of the subsystems, the subsystem models of the thermal management system other than the variable cycle engine subsystem are established; (4) Establishing a flight mission parameter input module based on the relationship between the variable cycle engine subsystem thermal load and the flight mission parameters; (5) Based on the mass and energy transfer relationship between the variable cycle engine subsystem and other subsystems, combined with the flight mission parameter input module, a multi-system coupled thermal management system model is built.

2. The modeling method according to claim 1, characterized in that: In the variable geometry mechanism characteristic calculation model of the variable cycle engine, the variable mechanism blade angle is adjusted according to different working states.

3. The modeling method according to claim 2, characterized in that: Other subsystem models in the thermal management system include a fuel subsystem model, a lubricating oil subsystem model, and an environmental control subsystem model; the fuel subsystem model includes a fuel tank mass conservation model, a fuel tank energy conservation model, cross-flow heat exchanger efficiency, pump effective power, outlet temperature through the pump, and outlet pressure through the pump; the lubricating oil subsystem model includes lubricating oil cooling high / low pressure shaft heat and lubricating oil temperature; the environmental control subsystem includes the mass flow rate of bleed air and the temperature of ram air.

4. A variable cycle engine thermal management system using the modeling method of the variable cycle engine thermal management system according to any one of claims 1 to 3, characterized in that: It includes several subsystem models and a flight mission parameter input module. The several subsystem models include a variable cycle engine subsystem model and other subsystem models. The flight mission parameter input module is used to determine the engine working state and the thermal load size of the engine subsystem by giving the input parameters of the variable cycle engine subsystem model; The several subsystem models are coupled to each other based on mass and energy transfer relationships, and the node temperatures of other subsystem models are obtained according to the input parameters of the variable cycle engine subsystem model.

5. The variable cycle engine thermal management system according to claim 4, characterized in that: The flight mission parameters include the current engine flight altitude, the flight Mach number, and adjustable mechanism parameters for determining the engine operating mode.

Images