CN112507476A - Integrated modeling method for variable-geometry air inlet and engine - Google Patents
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Abstract
The invention discloses an integrated modeling method of a variable geometry air inlet and an engine, which comprises the following steps: step S1, establishing a double-shaft turbofan engine component level model according to the GasTurb characteristic diagram; step S2, establishing a variable geometry air inlet throttling characteristic diagram; s3, establishing a variable geometry air inlet zero-dimensional model according to the variable geometry air inlet throttling characteristic diagram; and S4, matching the biaxial turbofan engine component level model determined in the step S1 and the variable geometry air inlet channel zero-dimensional model determined in the step S3 to obtain an air inlet channel and engine integrated model. The invention designs an integrated modeling method of a variable geometry air inlet and an engine, which solves the problem that the traditional engine model does not consider air inlet regulation and air inlet resistance. Compared with the traditional fixed geometry air inlet throttling characteristic, the variable geometry air inlet throttling characteristic realizes the conversion of a variable geometry air inlet from a CFD (computational fluid dynamics) model to a zero-dimensional mathematical model.
Description
Technical Field
The invention relates to the field of modeling and simulation of the state of an aircraft engine above a slow vehicle, in particular to an integrated modeling method of a variable geometry air inlet and an engine.
Background
The aircraft engine is a very complex pneumatic thermodynamic process system, and in order to perform good control, prediction and fault diagnosis on the aircraft engine, the characteristics of the aircraft engine must be analyzed and measured firstly, and a mathematical model of the aircraft engine is established, which is an essential important task in the development process of an engine control system. The aircraft engine mathematical model has a very wide application, and is a premise and a basis for implementing control and diagnosis on the engine. The performance simulation model of the aircraft engine is established and optimized through the computer, and the method has important significance for shortening the design and test period of the numerical control system of the engine, reducing the research and development cost, avoiding the test risk and the like.
The air inlet channel and the engine are important components of the aircraft propulsion system, when the aircraft propulsion system works, the air inlet channel and the engine have the flow matching problem, and the propulsion system can work efficiently only if the air inlet channel and the engine are well matched. For a supersonic engine, a reasonably designed air inlet channel model can effectively compress incoming flow gas, and the performance of the engine is improved. With the continuous development of the research of the aero-engine, the matching of the air inlet and the engine and the optimization problem of the comprehensive performance become more and more important contents of the research in the field of engine control. Because the actual engine works under different working conditions, the change ranges of the flying height, the Mach number, the attack angle and the like are very large, the air inlet channel needs to be matched with the flow characteristics of the engine under different working conditions, and the air inlet channel is subjected to variable geometry adjustment, so that the air inlet channel has higher flow coefficient, total pressure recovery coefficient and smaller aerodynamic resistance, and the air inlet channel and the engine work together in the optimal state. The main ways of air inlet duct regulation are: the position of the wedge surface is moved, the angle of the compression surface is adjusted, the area of the throat is adjusted, the area of the inlet is adjusted, and a bypass system is added. Establishing a supersonic speed air inlet/engine integrated component level model is a premise and a basis for carrying out integrated control on the air inlet/engine.
Disclosure of Invention
In view of the above, the invention aims to provide an integrated modeling method for a variable geometry air inlet and an engine, which mainly aims to use a small bypass ratio dual-rotor boost mixed exhaust turbofan engine as a research object, and aims at the problem of matching of an air inlet and an engine model, an air inlet CFD (computational fluid dynamics) calculation data is adopted to establish a variable geometry air inlet zero-dimensional model, and an air inlet and engine integrated model is established through matching of the air inlet and the engine flow, so that the simulation precision of the engine model is remarkably improved, and the output characteristic of the model is closer to that of an actual engine.
In order to achieve the above object, the present invention provides an integrated modeling method for a variable geometry air inlet and an engine, comprising the following steps:
step S1, establishing a double-shaft turbofan engine component level model according to the GasTurb characteristic diagram;
step S2, performing CFD calculation on the variable geometry air inlet to obtain output data, and establishing a variable geometry air inlet throttling characteristic diagram according to the output data;
s3, establishing a variable geometry air inlet zero-dimensional model according to the variable geometry air inlet throttling characteristic diagram;
and S4, matching the biaxial turbofan engine component level model determined in the step S1 and the variable geometry air inlet channel zero-dimensional model determined in the step S3 to obtain an air inlet channel and engine integrated model.
Further, in the step S1, the GasTurb characteristic map is a characteristic map of the two-shaft turbofan engine rotating member obtained from gas turbine performance analysis software GasTurb;
the component-level model of the double-shaft turbofan engine refers to: firstly, a mathematical model of each component of the engine is established according to pneumatic thermodynamics, and then a component-level model of the double-shaft turbofan engine is established according to a static pressure balance equation and a flow balance equation of adjacent components and a power balance equation of a rotating component.
Further, in step S2, the performing CFD calculation on the variable geometry intake duct includes: and the matching of the component-level model of the double-shaft turbofan engine is used as a reference, the CFD calculation is carried out on the variable geometry air inlet channel under different working conditions, and the output data of the variable geometry air inlet channel is obtained and comprises: the total pressure recovery coefficient and the flow coefficient of the outlet;
the variable geometry air inlet throttling characteristic diagram is as follows: and the outlet total pressure recovery coefficient and the flow coefficient are in a relational graph.
Further, step S3 specifically includes:
step S301, under the condition of given flight Mach number and altitude, calculating the static temperature T of the standard atmospheric air after passing through the variable geometry air inlet channelS0Hydrostatic pressure PS0And total gas temperature Tt1And total pressure P of gast1；
Step S302, determining an outlet total pressure recovery coefficient sigma according to the flow coefficient of the variable geometry air inlet channel according to the variable geometry air inlet channel throttling characteristic diagramI；
Step S303, calculating the throat gas flow of the variable geometry air inlet according to a gas dynamics formula, wherein the expression is as follows:
in the formula, k is a gas adiabatic exponent, R is a gas constant, AcExpressed as the capture area of the variable geometry inlet, defined as the cross-sectional area of the inlet of the variable geometry inlet in the vertical direction, q (lambda)1) Expressed as a function of inlet flow to the variable geometry inlet,
expressed as the variable geometry inlet exit flow coefficient, Pt1Expressed as the gas flowing through the variable geometry at standard atmospheric pressureTotal pressure of gas in inlet channel, Tt1Expressed as the total gas temperature at standard atmospheric pressure when gas flows through the variable geometry inlet;
step S304, calculating the outlet gas flow of the variable geometry air inlet channel when the auxiliary air inlet valve and the auxiliary air release valve are respectively opened, wherein the expression is as follows:
in the formula, fA(β) is expressed as the auxiliary intake valve area, q (λ)th) Expressed as a flow function at the throat of a variable geometry inlet, fA(γ) is expressed as the auxiliary bleed valve area, WathExpressed as variable geometry inlet throat gas flow, Wa12,βExpressed as a function of the variable geometry port outlet gas flow when the auxiliary intake valve is open; wa12,γExpressed as a function of the variable geometry outlet gas flow of the inlet when the auxiliary bleed valve is open, Pt1Expressed as the total gas pressure, T, at standard atmospheric pressure, at which the gas flows through the variable-geometry inlett1Expressed as the total temperature of the gas as it flows through the variable geometry inlet at standard atmospheric pressure.
Further, in the step S4, the matching operation includes: adding an inlet duct outlet and fan inlet flow balance equation into the double-shaft turbofan engine component level model, and adding an initial guess value which is a variable geometry inlet duct outlet flow coefficient
Further, the step S1 specifically includes:
step S101, firstly, obtaining a characteristic diagram of a rotating part of the double-shaft turbofan engine from gas turbine performance analysis software GasTurb, and establishing a mathematical model of each part in the double-shaft turbofan engine according to aerodynamic mechanics, wherein each part comprises: the device comprises a fan, a gas compressor, a combustion chamber, a high-pressure turbine, a low-pressure turbine, an outer duct, a mixing chamber, an afterburner and a tail nozzle; then establishing an engine bleed air model;
step S102, establishing a common working equation of each component, wherein the expression of the common working equation is as follows:
the formula is a component-level model of the two-shaft turbofan engine, in which formula, equation PS6-P S160 is expressed as: a balance equation of the static pressure of the outer duct outlet and the static pressure of the inner duct nozzle outlet; equation Wg42-Wa3-Wf-WHcool1-WHcool2Expressed as: a balance equation of the sum of the inlet gas flow of the high-pressure turbine, the outlet gas flow of the compressor and the fuel flow; equation Wg5-Wg42-WLcool1-W Lcool20 is expressed as: the balance equation of the sum of the low-pressure turbine inlet gas flow, the high-pressure turbine outlet gas flow and the low-pressure turbine bleed air flow; equation Wg9-Wg7The balance equation of the inlet gas flow of the tail nozzle and the outlet gas flow of the afterburner is expressed as 0; equation ηHNHT-NC-NEXThe equation is expressed as a high-pressure shaft power balance equation; equation ηLNLT-NFAnd 0 is expressed as a low-pressure shaft power balance equation.
Step S103, solving the common working equation by adopting Newton-Lafferson method iteration, and selecting a primary guess value, wherein the primary guess value comprises the following steps: low voltage speed nLHigh voltage rotation speed nHPressure ratio of fanFPressure ratio of compressorCHigh pressure turbine pressure drop ratio piHTLow pressure turbine pressure drop ratio piLT。
Further, the step S2 specifically includes:
step S201, simulating the component-level model of the double-shaft turbofan engine obtained in step S1 to obtain the required gas flow of different flight envelope points, and performing CFD calculation on the variable geometry air inlet channel on the premise of meeting the requirement of matching with the required flow of the engine to obtain output data, wherein the output data comprises: the total pressure recovery coefficient of the outlet, the flow coefficient, the angles of the second and third-stage compression surfaces of the variable-geometry air inlet channel during matching and the opening degree of the auxiliary air inlet/outlet valve;
and S202, constructing a variable geometry air inlet channel throttling characteristic diagram under different Mach numbers by adopting the flow coefficient and the total outlet pressure recovery coefficient.
Further, the expression of the intake duct and engine integrated model is as follows:
in the formula, equation PS6-P S160 is expressed as: a balance equation of the static pressure of the outer duct outlet and the static pressure of the inner duct nozzle outlet; equation Wg42-Wa3-Wf-WHcool1-WHcool2Expressed as: a balance equation of the sum of the inlet gas flow of the high-pressure turbine, the outlet gas flow of the compressor and the fuel flow; equation Wg5-Wg42-WLcool1-W Lcool20 is expressed as: the balance equation of the sum of the low-pressure turbine inlet gas flow, the high-pressure turbine outlet gas flow and the low-pressure turbine bleed air flow; equation Wg9-Wg7The balance equation of the inlet gas flow of the tail nozzle and the outlet gas flow of the afterburner is expressed as 0; equation ηHNHT-NC-NEXThe equation is expressed as a high-pressure shaft power balance equation; equation ηLNLT-NFAnd 0 is expressed as a low-pressure shaft power balance equation.
The invention has the beneficial effects that:
the invention designs an integrated modeling method of a variable geometry air inlet and an engine, which solves the problem that the traditional engine model does not consider air inlet regulation and air inlet resistance. Compared with the traditional fixed geometry air inlet throttling characteristic, the variable geometry air inlet throttling characteristic realizes the conversion of a variable geometry air inlet from a CFD (computational fluid dynamics) model to a zero-dimensional mathematical model. On the basis, matching of the air inlet model and the engine model is considered, and a variable-geometry air inlet/engine integrated model is established.
Drawings
FIG. 1 is a flow chart of the present invention.
FIG. 2 is a schematic view of a variable geometry inlet configuration.
FIG. 3 is a fixed geometry port throttle map.
FIG. 4 is a graph of variable geometry port throttle characteristics.
FIG. 5 is a graph comparing the engine model at the design point and the GasTurb steady state simulation results.
FIG. 6 is a graph of the steady-state simulation result of the integrated model during intake air conditioning of the intake passage at the non-design point 1.
FIG. 7 is a graph of the steady-state simulation result of the integrated model when the air inlet duct is subjected to air release regulation at the non-design point 2.
FIG. 8 is a graph of the steady-state simulation result of the integrated model when the air inlet compression surface of the non-design point 2 is adjusted.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. 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.
Example 1
Referring to fig. 1, fig. 1 discloses the principle of the present invention, which is mainly divided into two processes of variable geometry inlet engine modeling and variable geometry inlet engine matching. The method mainly comprises the steps of establishing a turbofan engine model according to a GasTurb characteristic diagram, establishing a variable geometry air inlet throttling characteristic diagram by adopting air inlet CFD (computational fluid dynamics) calculation data, establishing an air inlet zero-dimensional model, performing two-level and three-level compression surface adjustment and auxiliary air inlet and outlet adjustment, and establishing a variable geometry air inlet and engine integrated model by matching air inlets with engine flow; the embodiment provides an integrated modeling method for a variable geometry air inlet and an engine, which comprises the following steps:
step S1, establishing a double-shaft turbofan engine component level model according to the GasTurb characteristic diagram;
specifically, in step S1, the GasTurb characteristic map is a characteristic map of the two-shaft turbofan engine rotating member obtained from gas turbine performance analysis software GasTurb;
the two-shaft turbofan engine component level model refers to: firstly, a mathematical model of each component of the engine is established according to pneumatic thermodynamics, and then a component-level model of the double-shaft turbofan engine is established according to a static pressure balance equation and a flow balance equation of adjacent components and a power balance equation of a rotating component.
More specifically, step S1 includes:
step S101, firstly, obtaining a characteristic diagram of a rotating part of the double-shaft turbofan engine from gas turbine performance analysis software GasTurb, and establishing a mathematical model of each part in the double-shaft turbofan engine according to aerodynamic mechanics, wherein each part comprises: the device comprises a fan, a gas compressor, a combustion chamber, a high-pressure turbine, a low-pressure turbine, an outer duct, a mixing chamber, an afterburner and a tail nozzle; then establishing an engine bleed air model;
step S102, establishing a common working equation of each component, wherein the common working equation specifically comprises 3 flow balance equations, 1 static pressure balance equation and 2 power balance equations, and the common working equation comprises the following steps: the balance equation of the static pressure of the outlet of the outer duct and the static pressure of the outlet of the inner duct spray pipe is obtained; a balance equation of the sum of the inlet gas flow of the high-pressure turbine, the outlet gas flow of the compressor and the fuel flow; the balance equation of the sum of the low-pressure turbine inlet gas flow, the high-pressure turbine outlet gas flow and the low-pressure turbine bleed air flow; a balance equation of the inlet gas flow of the tail nozzle and the outlet gas flow of the afterburner; a high-pressure shaft power balance equation; a low-pressure shaft power balance equation; the expression of the common working equation is:
equation (1) is a two-axis turbofan engine component level model, in which equation PS6-P S160 is expressed as: a balance equation of the static pressure of the outer duct outlet and the static pressure of the inner duct nozzle outlet; equation Wg42-Wa3-Wf-WHcool1-WHcool2Expressed as: a balance equation of the sum of the inlet gas flow of the high-pressure turbine, the outlet gas flow of the compressor and the fuel flow; equation Wg5-Wg42-WLcool1-W Lcool20 is expressed as: the balance equation of the sum of the low-pressure turbine inlet gas flow, the high-pressure turbine outlet gas flow and the low-pressure turbine bleed air flow; equation Wg9-Wg7The balance equation of the inlet gas flow of the tail nozzle and the outlet gas flow of the afterburner is expressed as 0; equation ηHNHT-NC-NEXThe equation is expressed as a high-pressure shaft power balance equation; equation ηLNLT-NFAnd 0 is expressed as a low-pressure shaft power balance equation.
Step S103, a common working equation is iteratively solved by adopting a Newton-Lawson method, and an initial guess value is selected, wherein the initial guess value comprises the following steps: low voltage speed nLHigh voltage rotation speed nHPressure ratio of fanFPressure ratio of compressorCHigh pressure turbine pressure drop ratio piHTLow pressure turbine pressure drop ratio piLTWhen calculating, a set of guess variables are first given and substituted into the equation set to calculate to obtain a set of error values, then the guess variables are corrected by the error values, and calculation and correction are performed again until the absolute values of the errors meet certain precision requirements.
Step S2, performing CFD calculation on the variable geometry air inlet to obtain output data, and establishing a variable geometry air inlet throttling characteristic diagram according to the output data;
specifically, in step S2, the CFD calculation data of the variable geometry intake duct is: by taking the matching with the component-level model of the double-shaft turbofan engine as a reference, CFD calculation is carried out on the variable geometry air inlet channel under different working conditions, and output data of the variable geometry air inlet channel are obtained, wherein the output data comprise: the total pressure recovery coefficient and the flow coefficient of the outlet;
the variable geometry air inlet throttling characteristic diagram is as follows: and (3) a relationship diagram of the total pressure recovery coefficient of the outlet and the flow coefficient.
More specifically, step S2 includes:
step S201, referring to fig. 2, fig. 2 is a schematic structural diagram of the variable geometry air intake duct established in the present invention, where the adjustable components of the air intake duct are the second and third-level compression surfaces and the auxiliary intake/exhaust valves, the component-level model of the dual-axis turbofan engine obtained in step S1 is simulated to obtain the required gas flow rates of different flight envelope points, and on the premise of satisfying the matching with the required flow rate of the engine, CFD calculation is performed on the variable geometry air intake duct to obtain output data, where the output data includes: the total pressure recovery coefficient of the outlet, the flow coefficient, the angles of the second and third-stage compression surfaces of the variable-geometry air inlet channel during matching and the opening degree of the auxiliary air inlet/outlet valve; in a subsonic speed state, an air inlet passage assists an air inlet valve to be opened, and an auxiliary air outlet valve to be closed; in a supersonic speed state, the auxiliary air inlet valve of the air inlet passage is closed, and the auxiliary air release valve is opened.
Step S202, referring to fig. 3, fig. 3 is an air inlet characteristic diagram published in the NASA report, and it can be known that, for an air inlet with a certain geometric characteristic, when the incoming flow mach number is the same, the relationship between the total pressure recovery coefficient and the flow coefficient is determined, but the characteristic diagram can only represent the characteristic of the fixed geometric air inlet. Therefore, according to the geometry determined in step S201 when the variable geometry intake duct is matched with the engine, a variable geometry intake duct throttling characteristic map under different mach numbers is constructed by using the flow coefficient and the total pressure recovery coefficient calculated by the variable geometry intake duct CFD obtained in step S201, and specifically, refer to fig. 4.
S3, establishing a variable geometry air inlet zero-dimensional model according to the variable geometry air inlet throttling characteristic diagram;
specifically, step S3 includes:
step S301, under the condition of given flight Mach number and altitude, calculating the static temperature T of the standard atmospheric air after passing through the variable geometry air inlet channelS0Hydrostatic pressure PS0And total gas temperature Tt1And total pressure P of gast1；
Step S3011, obtaining static temperature and static pressure of inlet airflow of the variable geometry air inlet according to a fitting formula, wherein the expression is as follows:
in equations (2) and (3), h is expressed in m as the height of the engine operating point.
Step S3012, calculating total temperature and total pressure of inlet airflow of the variable geometry air inlet according to the incoming flow Mach number, wherein the expression is as follows:
step S302, referring to FIG. 4, according to the variable geometry air inlet throttling characteristic diagram, determining an outlet total pressure recovery coefficient sigma according to the flow coefficient of the variable geometry air inletI；
Step S303, calculating the throat gas flow of the variable geometry air inlet according to a gas dynamics formula,
more specifically, step S303 includes the steps of:
step S3031, calculating the outlet flow of the variable geometry air inlet according to a gas dynamic flow formula;
in the formula (6), k is represented by a gas adiabatic index, R is represented by a gas constant, and T is represented byt2、Pt2Respectively expressed as total pressure of inlet outlet total temperature, q (lambda)2) Denoted as air intake ductOutlet flow function, A2Expressed as port exit area.
Step S3032, calculating the reduced flow of the outlet of the variable geometry air inlet according to a similar theorem;
in the formula (7), θ ═ Tt2/288.15，δ＝Pt2101325 to give the formula:
step S3033, defining according to variable geometry air inlet channel flow coefficient
As shown in fig. 2, the outlet of the variable geometry inlet is reduced in flow;
step S3034, calculating the total temperature and pressure of the outlet of the variable geometry air inlet channel:
Tt2＝Tt1 (10)
Pt2＝Pt1σI (11)
step 3035, simplifying the inlet outlet reduced flow according to the formulas (11), (12) and (13):
step 3036, calculating the actual flow according to the converted flow at the outlet of the air inlet:
in the formula (13), Wa12The physical flow of the outlet of the variable geometry air inlet is represented, and when the auxiliary air inlet and outlet valve of the variable geometry air inlet is closed, the throat flow of the variable geometry air inlet is changed according to the flow continuous theorem:
in the formula (14), k represents a gas adiabatic index, R represents a gas constant, and AcExpressed as the capture area of the variable geometry inlet, defined as the cross-sectional area of the inlet of the variable geometry inlet in the vertical direction, q (lambda)1) Expressed as a function of inlet flow to the variable geometry inlet,
expressed as the variable geometry inlet exit flow coefficient, Pt1Expressed as the total pressure of the gas, T, at standard atmospheric pressure, as it flows through a variable geometry inlett1Expressed as the total gas temperature at standard atmospheric pressure when the gas flows through the variable geometry inlet;
step S304, calculating the outlet gas flow of the variable geometry air inlet channel when the auxiliary air inlet valve and the auxiliary air release valve are respectively opened, wherein the expression is as follows:
in the formula (15) and the formula (16), fA(β) is expressed as the auxiliary intake valve area, q (λ)th) Expressed as a flow function at the throat of a variable geometry inlet, fA(γ) is expressed as the auxiliary bleed valve area, WathExpressed as variable geometry inlet throat gas flow, Wa12,βExpressed as variable geometry intake when the auxiliary intake valve is openA function of outlet gas flow; wa12,γExpressed as a function of the variable geometry port outlet gas flow when the auxiliary bleed valve is open.
In the step, the method for calculating the outlet gas flow of the variable geometry air inlet channel when the auxiliary inlet valve and the auxiliary exhaust valve are respectively opened comprises the following steps: in the formula, q (lambda)th) Expressed as a variable geometry air inlet throat flow function, because the entering air flow in the variable geometry air inlet is compressed by oblique shock waves and normal shock waves, the throat Mach number can reach 1 usually, so q (lambda)th) Also 1, so assuming the gas flow velocity at the auxiliary intake and exhaust valves is sonic, the direction coincides with the incoming flow.
And S4, matching the biaxial turbofan engine component level model determined in the step S1 and the variable geometry air inlet channel zero-dimensional model determined in the step S3 to obtain an air inlet channel and engine integrated model.
Specifically, the matching operation includes: adding an inlet duct outlet and fan inlet flow balance equation into the double-shaft turbofan engine part-level model obtained in the step S1, and adding an initial guess value, wherein the initial guess value is a variable geometry inlet duct outlet flow coefficient
More specifically, the expression of the intake passage and engine integration model is as follows:
in formula (17), equation PS6-P S160 is expressed as: a balance equation of the static pressure of the outer duct outlet and the static pressure of the inner duct nozzle outlet; equation Wg42-Wa3-Wf-WHcool1-WHcool2Expressed as: a balance equation of the sum of the inlet gas flow of the high-pressure turbine, the outlet gas flow of the compressor and the fuel flow; equation Wg5-Wg42-WLcool1-W Lcool20 is expressed as: low pressure turbine inlet gas flow and high pressure turbine outlet gas flowAnd a low pressure turbine bleed air flow; equation Wg9-Wg7The balance equation of the inlet gas flow of the tail nozzle and the outlet gas flow of the afterburner is expressed as 0; equation ηHNHT-NC-NEXThe equation is expressed as a high-pressure shaft power balance equation; equation ηLNLT-NFAnd 0 is expressed as a low-pressure shaft power balance equation.
In order to verify the effectiveness of the integrated modeling method for the variable geometry air inlet and the engine, the steady-state all-digital simulation of the integrated model of the air inlet and the engine under the standard atmospheric condition is carried out in the VC + +6.0 environment.
The specific embodiment of the invention takes a double-rotor boosting mixed exhaust turbofan engine with a certain small bypass ratio as a simulation object. Three working points of the engine in different states are tested, wherein the working point 1 is in a design point state, the working point 2 is in a subsonic speed state, and the working point 3 is in a supersonic speed state.
The multi-point steady state simulation results of the established engine model at operating point 1 were compared with GasTurb output data, and the results are shown in fig. 5. The errors of the model simulation result and GasTurb data are both less than 1%. FIG. 5 shows that the turbofan engine model was correctly established.
The influence of the adjustment of the auxiliary intake valve of the intake passage on the integrated model is researched at the working point 2, the angles of the second and third-level compression surfaces are kept unchanged, the auxiliary exhaust valve is closed, the opening of the auxiliary intake valve is adjusted to perform steady-state simulation on the integrated model, and the simulation result of the coefficient of recovery of the thrust of the integrated model and the total pressure of the intake passage is shown in FIG. 6. When the opening degree of the auxiliary inlet valve is 40 degrees, the total pressure recovery coefficient of the inlet channel is the largest, the thrust of the integrated model is the largest, compared with the state of not opening the auxiliary inlet valve, the thrust of the model is increased by 1.1%, meanwhile, the total pressure recovery coefficient of the inlet channel is also larger than that of the original state, and the thrust of the model and the total pressure recovery coefficient of the inlet channel start to be reduced after the opening degree of the auxiliary inlet valve is continuously increased. When the auxiliary intake valve is opened, the flow which needs to flow from the inlet of the air inlet channel is reduced, the state of the air inlet channel is close to the critical state from the supercritical state, the loss of the air inlet channel is reduced, and the thrust of the integrated model is increased; when the opening of the auxiliary intake valve is larger than 40 degrees, the state of the intake passage is changed into a subcritical state, the overflow resistance is generated by the intake passage, meanwhile, the opening of the auxiliary intake valve is increased, so that the resistance generated by the intake valve is increased, and the thrust of the integrated model is reduced on the contrary. Therefore, the performance of the model can be improved by the air inlet auxiliary air inlet adjustment at the working point.
And at a working point 3, the influence of the air inlet passage auxiliary air release valve regulation and the second-stage and third-stage compression surface regulation on the integrated model is researched, and the air inlet passage auxiliary air inlet valve is closed. Firstly, the angle of the compression surface is kept unchanged, and the opening of the auxiliary air release valve is adjusted to perform steady-state simulation on the integrated model, and the result is shown in fig. 7. When the opening of the auxiliary air release valve is 20 degrees, the matching effect of the air inlet channel and the engine is the best, the model thrust is the largest, the state is improved by 1.3 percent compared with the state without opening the auxiliary air release valve, and the total pressure recovery coefficient of the air inlet channel is maintained at a higher level. When the auxiliary bleeding valve is opened, redundant gas which is originally required to be discharged through overflow of the inlet of the air inlet channel can be discharged from the bleeding valve, the overflow resistance of the air inlet channel is reduced, and the thrust of the integrated model is increased firstly; when the opening of the auxiliary air bleeding valve is larger than 20 degrees, the air bleeding resistance of the air inlet channel is increased to a degree larger than the reduction degree of the overflow resistance of the air inlet channel, and the thrust of the integrated model is gradually reduced. Keeping the optimal opening of the auxiliary air release valve unchanged, respectively adjusting the second-stage compression surface and the third-stage compression surface, and obtaining a model steady-state simulation result as shown in FIG. 8. When the opening degree of the auxiliary air release valve of the air inlet channel is optimal, the angle of the optimal second-stage compression surface of the air inlet channel is 5 degrees, the angle of the optimal third-stage compression surface is 4.5 degrees, the total pressure recovery coefficient of the air inlet channel is the largest at the moment, and the thrust of the integrated model is the largest. When the second and third-stage compression surfaces are gradually increased, the air inlet lip cover stripping shock wave gradually leaves from the inner side of the lip, the air flow can be decelerated and pressurized through the expansion wave area, the secondary strong compression wave disappears, the total pressure recovery coefficient of the air inlet channel can gradually rise, when the angle of the compression surface is continuously increased after the optimal compression surface angle is reached, the air inlet lip cover stripping shock wave is completely stripped, the air flow entering the air inlet channel is changed from partial subsonic velocity to all subsonic velocity, and therefore the total pressure recovery coefficient of the air inlet channel is gradually reduced. Therefore, auxiliary air bleeding and compression surface adjustment of the air inlet at the working point 3 can improve the performance of the air inlet and engine integrated model.
The invention designs an integrated modeling method of a variable geometry air inlet and an engine, which solves the problem that the traditional engine model does not consider air inlet regulation and air inlet resistance. Compared with the traditional fixed geometry air inlet throttling characteristic, the variable geometry air inlet throttling characteristic realizes the conversion of a variable geometry air inlet from a CFD (computational fluid dynamics) model to a zero-dimensional mathematical model. On the basis, the matching of the air inlet model and the engine model is considered, and an integrated model of the variable-geometry air inlet and the engine is established.
It should be noted that the above is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes and substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (8)
1. An integrated modeling method for a variable geometry air inlet and an engine is characterized by comprising the following steps:
step S1, establishing a double-shaft turbofan engine component level model according to the GasTurb characteristic diagram;
step S2, performing CFD calculation on the variable geometry air inlet to obtain output data, and establishing a variable geometry air inlet throttling characteristic diagram according to the output data;
s3, establishing a variable geometry air inlet zero-dimensional model according to the variable geometry air inlet throttling characteristic diagram;
and S4, matching the biaxial turbofan engine component level model determined in the step S1 and the variable geometry air inlet channel zero-dimensional model determined in the step S3 to obtain an air inlet channel and engine integrated model.
2. The method of claim 1, wherein in step S1, the GasTurb characteristic map is a characteristic map of a two-shaft turbofan engine rotating member obtained from gas turbine performance analysis software GasTurb;
the component-level model of the double-shaft turbofan engine refers to: firstly, a mathematical model of each component of the engine is established according to pneumatic thermodynamics, and then a component-level model of the double-shaft turbofan engine is established according to a static pressure balance equation and a flow balance equation of adjacent components and a power balance equation of a rotating component.
3. The method of claim 2, wherein in step S2, the CFD calculation for the variable geometry intake duct is: and the matching of the component-level model of the double-shaft turbofan engine is used as a reference, the CFD calculation is carried out on the variable geometry air inlet channel under different working conditions, and the output data of the variable geometry air inlet channel is obtained and comprises: the total pressure recovery coefficient and the flow coefficient of the outlet;
the variable geometry air inlet throttling characteristic diagram is as follows: and the outlet total pressure recovery coefficient and the flow coefficient are in a relational graph.
4. The method for integrally modeling the variable geometry intake duct and the engine according to claim 3, wherein the step S3 specifically includes:
step S301, under the condition of given flight Mach number and altitude, calculating the static temperature T of the standard atmospheric air after passing through the variable geometry air inlet channelS0Hydrostatic pressure PS0And total gas temperature Tt1And total pressure P of gast1；
Step S302, determining an outlet total pressure recovery coefficient sigma according to the flow coefficient of the variable geometry air inlet channel according to the variable geometry air inlet channel throttling characteristic diagramI；
Step S303, calculating the throat gas flow of the variable geometry air inlet according to a gas dynamics formula, wherein the expression is as follows:
in the formula, k representsIs a gas adiabatic index, R is a gas constant, AcExpressed as the capture area of the variable geometry inlet, defined as the cross-sectional area of the inlet of the variable geometry inlet in the vertical direction, q (lambda)1) Expressed as a function of inlet flow to the variable geometry inlet,
expressed as the variable geometry inlet exit flow coefficient, Pt1Expressed as the total gas pressure, T, at standard atmospheric pressure, at which the gas flows through the variable-geometry inlett1Expressed as the total gas temperature at standard atmospheric pressure when gas flows through the variable geometry inlet;
step S304, calculating the outlet gas flow of the variable geometry air inlet channel when the auxiliary air inlet valve and the auxiliary air release valve are respectively opened, wherein the expression is as follows:
in the formula, fA(β) is expressed as the auxiliary intake valve area, q (λ)th) Expressed as a flow function at the throat of a variable geometry inlet, fA(γ) is expressed as the auxiliary bleed valve area, WathExpressed as variable geometry inlet throat gas flow, Wa12,βExpressed as a function of the variable geometry port outlet gas flow when the auxiliary intake valve is open; wa12,γExpressed as a function of the variable geometry outlet gas flow of the inlet when the auxiliary bleed valve is open, Pt1Expressed as the total gas pressure, T, at standard atmospheric pressure, at which the gas flows through the variable-geometry inlett1Expressed as the total temperature of the gas as it flows through the variable geometry inlet at standard atmospheric pressure.
5. A variable geometry inlet according to claim 4 andan integrated modeling method of an engine, characterized in that in the step S4, the matching operation includes: adding an inlet duct outlet and fan inlet flow balance equation into the double-shaft turbofan engine component level model, and adding an initial guess value which is a variable geometry inlet duct outlet flow coefficient
6. The method for modeling the variable geometry intake duct and the engine as a whole as claimed in claim 5, wherein the step S1 specifically comprises:
step S101, firstly, obtaining a characteristic diagram of a rotating part of the double-shaft turbofan engine from gas turbine performance analysis software GasTurb, and establishing a mathematical model of each part in the double-shaft turbofan engine according to aerodynamic mechanics, wherein each part comprises: the device comprises a fan, a gas compressor, a combustion chamber, a high-pressure turbine, a low-pressure turbine, an outer duct, a mixing chamber, an afterburner and a tail nozzle; then establishing an engine bleed air model;
step S102, establishing a common working equation of each component, wherein the expression of the common working equation is as follows:
the formula is a component-level model of the two-shaft turbofan engine, in which formula, equation PS6-PS160 is expressed as: a balance equation of the static pressure of the outer duct outlet and the static pressure of the inner duct nozzle outlet; equation Wg42-Wa3-Wf-WHcool1-WHcool2Expressed as: a balance equation of the sum of the inlet gas flow of the high-pressure turbine, the outlet gas flow of the compressor and the fuel flow; equation Wg5-Wg42-WLcool1-WLcool20 is expressed as: the balance equation of the sum of the low-pressure turbine inlet gas flow, the high-pressure turbine outlet gas flow and the low-pressure turbine bleed air flow; equation Wg9-Wg7The balance equation of the inlet gas flow of the tail nozzle and the outlet gas flow of the afterburner is expressed as 0; equation ηHNHT-NC-NEXThe equation is expressed as a high-pressure shaft power balance equation; equation ηLNLT-NFThe equation is expressed as a low-pressure shaft power balance equation;
step S103, solving the common working equation by adopting Newton-Lafferson method iteration, and selecting a primary guess value, wherein the primary guess value comprises the following steps: low voltage speed nLHigh voltage rotation speed nHPressure ratio of fanFPressure ratio of compressorCHigh pressure turbine pressure drop ratio piHTLow pressure turbine pressure drop ratio piLT。
7. The method for modeling the variable geometry intake duct and the engine in an integrated manner as claimed in claim 6, wherein the step S2 specifically comprises:
step S201, simulating the component-level model of the double-shaft turbofan engine obtained in step S1 to obtain the required gas flow of different flight envelope points, and performing CFD calculation on the variable geometry air inlet channel on the premise of meeting the requirement of matching with the required flow of the engine to obtain output data, wherein the output data comprises: the total pressure recovery coefficient of the outlet, the flow coefficient, the angles of the second and third-stage compression surfaces of the variable-geometry air inlet channel during matching and the opening degree of the auxiliary air inlet/outlet valve;
and S202, constructing a variable geometry air inlet channel throttling characteristic diagram under different Mach numbers by adopting the flow coefficient and the total outlet pressure recovery coefficient.
8. The method of claim 7, wherein the expression of the integrated model of the intake passage and the engine is as follows:
in the formula, equation PS6-PS160 is expressed as: a balance equation of the static pressure of the outer duct outlet and the static pressure of the inner duct nozzle outlet; equation Wg42-Wa3-Wf-WHcool1-WHcool2Expressed as: a balance equation of the sum of the inlet gas flow of the high-pressure turbine, the outlet gas flow of the compressor and the fuel flow; equation Wg5-Wg42-WLcool1-WLcool20 is expressed as: the balance equation of the sum of the low-pressure turbine inlet gas flow, the high-pressure turbine outlet gas flow and the low-pressure turbine bleed air flow; equation Wg9-Wg7The balance equation of the inlet gas flow of the tail nozzle and the outlet gas flow of the afterburner is expressed as 0; equation ηHNHT-NC-NEXThe equation is expressed as a high-pressure shaft power balance equation; equation ηLNLT-NFAnd 0 is expressed as a low-pressure shaft power balance equation.
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