CN112507476B - Integrated modeling method for variable geometry air inlet channel and engine - Google Patents
Integrated modeling method for variable geometry air inlet channel and engine Download PDFInfo
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Abstract
The invention discloses an integrated modeling method for a variable geometry air inlet channel and an engine, which comprises the following steps: s1, establishing a double-shaft turbofan engine part level model according to a GasTurb characteristic diagram; s2, establishing a variable geometry air inlet throttling characteristic diagram; s3, establishing a variable geometry air inlet channel zero-dimensional model according to the variable geometry air inlet channel throttling characteristic diagram; and S4, performing matching operation on the double-shaft turbofan engine part level model determined in the step S1 and the variable geometry air inlet zero-dimensional model determined in the step S3 to obtain an air inlet and engine integrated model. The invention relates to an integrated modeling method for a variable geometry air inlet and an engine, which solves the problem that the traditional engine model does not consider air inlet adjustment and air inlet resistance. Compared with the traditional fixed-geometry air inlet throttling characteristic, the proposed variable-geometry air inlet throttling characteristic realizes the conversion of the variable-geometry air inlet from a CFD model to a zero-dimensional mathematical model.
Description
Technical Field
The invention relates to the field of modeling and simulation of the state above an aeroengine slow car, in particular to an integrated modeling method for a variable geometry air inlet channel and an engine.
Background
The aeroengine is a very complex aerodynamic thermodynamic process system, and in order to perform good control, prediction and fault diagnosis on the aeroengine, firstly, the characteristics of the aeroengine must be analyzed and measured, and a mathematical model of the aeroengine is established, which is an essential important task in the development process of an engine control system. The mathematical model of the aeroengine has very wide application, and is a precondition and basis for controlling and diagnosing the engine. The aeroengine performance simulation model is established and optimized through the computer, and the method has important significance for shortening the design and test period of the engine numerical control system, reducing the research and development cost, avoiding the test run risk and the like.
The air inlet and the engine are important components of the aircraft propulsion system, when the aircraft propulsion system works, the air inlet and the engine have the problem of flow matching, and only the air inlet and the engine are well matched, the propulsion system can work efficiently. For a supersonic engine, an air inlet channel model with reasonable design can effectively compress incoming gas, so that the performance of the engine is improved. With the continuous development of aeroengine research, the matching of an air inlet channel and an engine and the problem of optimizing 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 flying height, mach number, attack angle and other variable ranges are very large, the air inlet is required to be matched with the flow characteristics of the engine under different working conditions, and the air inlet is enabled to have higher flow coefficient, total pressure recovery coefficient and smaller aerodynamic resistance by carrying out variable geometry adjustment on the air inlet, so that the air inlet and the engine work together in an optimal state. The main mode of air inlet channel regulation is as follows: moving wedge position, adjusting compression face angle, adjusting throat area, adjusting inlet area, and adding bypass system. The establishment of the supersonic speed air inlet/engine integrated part level model is a precondition and foundation for carrying out air inlet/engine integrated comprehensive control.
Disclosure of Invention
In view of the problems of matching of an air inlet and an engine model, the invention adopts air inlet CFD calculation data to establish a zero-dimensional model of the variable geometry air inlet, and establishes an air inlet and engine integrated model through air inlet and engine flow matching, thereby remarkably improving the simulation precision of the engine model and enabling the output characteristic of the model to be closer to that of an actual engine.
In order to achieve the above purpose, the invention provides an integrated modeling method for a variable geometry air inlet channel and an engine, comprising the following steps:
s1, establishing a double-shaft turbofan engine part level model according to a GasTurb characteristic diagram;
s2, performing CFD calculation on the variable geometry air inlet channel to obtain output data, and establishing a variable geometry air inlet channel throttling characteristic diagram according to the output data;
S3, establishing a variable geometry air inlet channel zero-dimensional model according to the variable geometry air inlet channel throttling characteristic diagram;
And S4, performing matching operation on the double-shaft turbofan engine part level model determined in the step S1 and the variable geometry air inlet zero-dimensional model determined in the step S3 to obtain an air inlet and engine integrated model.
Further, in the step S1, the GasTurb characteristic map refers to a characteristic map of a rotating part of the twin-shaft turbofan engine obtained from the gas turbine performance analysis software GasTurb;
the double-shaft turbofan engine part level model refers to: firstly, establishing a mathematical model of each component of the engine according to aerodynamic thermodynamics, and then establishing a component level model of the biaxial turbofan engine 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 the step S2, the CFD calculation of the variable geometry air intake refers to: performing CFD calculation on the variable geometry air inlet under different working conditions by taking matching with the double-shaft turbofan engine part level model as a reference to obtain output data of the variable geometry air inlet, wherein the output data comprises: the outlet total pressure recovery coefficient and the flow coefficient;
The variable geometry port throttle map refers to: and the relation diagram of the outlet total pressure recovery coefficient and the flow coefficient.
Further, the step S3 specifically includes:
Step S301, under the condition of given flight Mach number and altitude, calculating a gas static temperature T S0, a gas static pressure P S0, a gas total temperature T t1 and a gas total pressure P t1 of standard atmospheric air flow after passing through the variable geometry air inlet channel;
Step S302, determining an outlet total pressure recovery coefficient sigma I according to the variable geometry air inlet throttling characteristic diagram and the flow coefficient of the variable geometry air inlet;
step S303, calculating the variable geometry air inlet channel throat gas flow according to an aerodynamic formula, wherein the expression is as follows:
In the formula, k is expressed as a gas adiabatic index, R is expressed as a gas constant, A c is expressed as a capture area of the variable geometry inlet, a cross-sectional area of the variable geometry inlet in a vertical direction is defined, q (lambda 1) is expressed as a variable geometry inlet flow function, Expressed as a variable geometry inlet outlet flow coefficient, P t1 is expressed as the total pressure of the gas as it flows through the variable geometry inlet at standard atmospheric pressure, and T t1 is expressed as the total temperature of the gas as it flows through the variable geometry inlet at standard atmospheric pressure;
Step S304, calculating the outlet gas flow of the variable geometry air inlet channel when the auxiliary air inlet valve and the auxiliary air outlet valve are respectively opened, wherein the expression is as follows:
In the formula, f A (beta) is expressed as an auxiliary inlet valve area, q (lambda th) is expressed as a flow function at the throat of the variable geometry inlet channel, f A (gamma) is expressed as an auxiliary bleed valve area, W ath is expressed as a variable geometry inlet channel gas flow, and W a12,β is expressed as a function of a variable geometry inlet channel outlet gas flow when the auxiliary inlet valve is opened; w a12,γ is a function of the variable geometry inlet outlet gas flow when the auxiliary bleed door is open, P t1 is the total gas pressure at standard atmospheric pressure as gas flows through the variable geometry inlet, and T t1 is the total gas temperature at standard atmospheric pressure as gas flows through the variable geometry inlet.
Further, in the step S4, the matching operation includes: adding an inlet channel outlet and fan inlet flow balance equation into the double-shaft turbofan engine part level model, and adding a preliminary guess value, wherein the preliminary guess value is a variable geometry inlet channel outlet flow coefficient
Further, the step S1 specifically includes:
Step S101, firstly, a characteristic diagram of rotating parts of the double-shaft turbofan engine is obtained from gas turbine performance analysis software GasTurb, and a mathematical model of each part in the double-shaft turbofan engine is built according to aerodynamic thermodynamics, wherein each part comprises the following components: 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 exhaust 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 the biaxial turbofan engine component level model, in which the equation P S6-PS16 =0 is expressed as: a balance equation of the outlet static pressure of the outer culvert and the outlet static pressure of the inner culvert spray pipe; equation W g42-Wa3-Wf-WHcool1-WHcool2 is expressed as: a balance equation of the high pressure turbine inlet gas flow and the compressor outlet gas flow and the fuel flow; equation W g5-Wg42-WLcool1-WLcool2 =0 is expressed as: a balance equation for the low pressure turbine inlet gas flow and the high pressure turbine outlet gas flow and the low pressure turbine bleed gas flow; equation W g9-Wg7 =0 represents the tailpipe inlet gas flow balance equation with afterburner outlet gas flow; equation η HNHT-NC-NEX =0 is expressed as the high-voltage shaft power balance equation; equation η LNLT-NF =0 is expressed as a low-voltage shaft power balance equation.
Step S103, iteratively solving the common working equation by adopting a Newton-Lawson method, and selecting a preliminary guess value, wherein the preliminary guess value comprises: low pressure rotational speed n L, high pressure rotational speed n H, fan pressure ratio pi F, compressor pressure ratio pi C, high pressure turbine drop pressure ratio pi HT, low pressure turbine drop pressure ratio pi LT.
Further, the step S2 specifically includes:
Step S201, simulating the double-shaft turbofan engine part level model obtained in the step S1 to obtain required gas flow of different flight envelope points, and carrying out 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 outlet total pressure recovery coefficient, the flow coefficient, the angles of the second and third compression surfaces of the variable geometry air inlet channel when matched and the opening of the auxiliary air inlet and outlet door;
And S202, constructing a variable geometry air inlet throttling characteristic diagram under different Mach numbers by adopting the flow coefficient and the outlet total pressure recovery coefficient.
Further, the expression of the integrated model of the air inlet channel and the engine is as follows:
In the formula, equation P S6-PS16 =0 is expressed as: a balance equation of the outlet static pressure of the outer culvert and the outlet static pressure of the inner culvert spray pipe; equation W g42-Wa3-Wf-WHcool1-WHcool2 is expressed as: a balance equation of the high pressure turbine inlet gas flow and the compressor outlet gas flow and the fuel flow; equation W g5-Wg42-WLcool1-WLcool2 =0 is expressed as: a balance equation for the low pressure turbine inlet gas flow and the high pressure turbine outlet gas flow and the low pressure turbine bleed gas flow; equation W g9-Wg7 =0 represents the tailpipe inlet gas flow balance equation with afterburner outlet gas flow; equation η HNHT-NC-NEX =0 is expressed as the high-voltage shaft power balance equation; equation η LNLT-NF =0 is expressed as a low-voltage shaft power balance equation.
The beneficial effects of the invention are as follows:
The invention relates to an integrated modeling method for a variable geometry air inlet and an engine, which solves the problem that the traditional engine model does not consider air inlet adjustment and air inlet resistance. Compared with the traditional fixed-geometry air inlet throttling characteristic, the proposed variable-geometry air inlet throttling characteristic realizes the conversion of the variable-geometry air inlet from a CFD model to a zero-dimensional mathematical model. On the basis, the matching of the air inlet channel model and the engine model is considered, and the variable geometry air inlet channel/engine integrated model is established.
Drawings
Fig. 1 is a flow chart of the present invention.
FIG. 2 is a schematic diagram of a variable geometry inlet.
FIG. 3 is a graph of fixed geometry port throttles.
FIG. 4 is a variable geometry port throttle map.
FIG. 5 is a graph comparing engine models at design points and GasTurb steady state simulation results.
FIG. 6 is a graph of steady-state simulation results of an integrated model during inlet air conditioning at non-design point 1.
FIG. 7 is a graph of steady-state simulation results for an integrated model at off-design point 2 air bleed adjustment.
FIG. 8 is a graph of steady-state simulation results of an integrated model during adjustment of the compression surface of the inlet at non-design point 2.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
Referring to fig. 1, fig. 1 discloses the principle of the present invention, and the present invention is mainly divided into two processes of modeling a variable geometry air intake engine and matching the variable geometry air intake engine. The main idea of the invention is to establish a turbofan engine model according to the GasTurb characteristic diagram, establish a variable geometry air inlet throttling characteristic diagram by adopting air inlet CFD calculation data, establish an air inlet zero-dimensional model, and be capable of carrying out two-level and three-level compression surface adjustment and auxiliary air inlet and air outlet adjustment, and establish a variable geometry air inlet and engine integrated model by matching air inlet and engine flow; the embodiment provides an integrated modeling method for a variable geometry air inlet channel and an engine, which comprises the following steps:
s1, establishing a double-shaft turbofan engine part level model according to a GasTurb characteristic diagram;
Specifically, in step S1, the GasTurb characteristic diagram refers to a characteristic diagram of a rotating part of the twin-shaft turbofan engine obtained from gas turbine performance analysis software GasTurb;
The double-shaft turbofan engine component level model refers to: firstly, establishing a mathematical model of each component of the engine according to aerodynamic thermodynamics, and then establishing a component level model of the biaxial turbofan engine 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, a characteristic diagram of rotating parts of the double-shaft turbofan engine is obtained from gas turbine performance analysis software GasTurb, and a mathematical model of each part in the double-shaft turbofan engine is built according to aerodynamic thermodynamics, 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 exhaust 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: an outer culvert outlet static pressure and an inner culvert spray pipe outlet static pressure balance equation; a balance equation of the high pressure turbine inlet gas flow and the compressor outlet gas flow and the fuel flow; a balance equation for the low pressure turbine inlet gas flow and the high pressure turbine outlet gas flow and the low pressure turbine bleed gas flow; an equilibrium equation of the inlet gas flow of the tail pipe and the outlet gas flow of the afterburner; a high-voltage shaft power balance equation; a low-voltage shaft power balance equation; the expression of the coaction equation is:
Equation (1) is a biaxial turbofan engine component level model in which equation P S6-PS16 =0 is expressed as: a balance equation of the outlet static pressure of the outer culvert and the outlet static pressure of the inner culvert spray pipe; equation W g42-Wa3-Wf-WHcool1-WHcool2 is expressed as: a balance equation of the high pressure turbine inlet gas flow and the compressor outlet gas flow and the fuel flow; equation W g5-Wg42-WLcool1-WLcool2 =0 is expressed as: a balance equation for the low pressure turbine inlet gas flow and the high pressure turbine outlet gas flow and the low pressure turbine bleed gas flow; equation W g9-Wg7 =0 represents the tailpipe inlet gas flow balance equation with afterburner outlet gas flow; equation η HNHT-NC-NEX =0 is expressed as the high-voltage shaft power balance equation; equation η LNLT-NF =0 is expressed as a low-voltage shaft power balance equation.
Step S103, adopting Newton-Lawson method to iteratively solve a joint working equation, and selecting a first guess value, wherein the first guess value comprises: when the low-pressure rotating speed n L, the high-pressure rotating speed n H, the fan pressure ratio pi F, the compressor pressure ratio pi C, the high-pressure turbine pressure drop ratio pi HT and the low-pressure turbine pressure drop ratio pi LT are calculated, a group of guess value variables are firstly given to be substituted into an equation set for calculation to obtain a group of error values, then the guess value variables are corrected by the error values, and the error values are calculated and corrected again until the absolute value of the error meets a certain precision requirement.
S2, performing CFD calculation on the variable geometry air inlet channel to obtain output data, and establishing a variable geometry air inlet channel throttling characteristic diagram according to the output data;
Specifically, in step S2, the variable geometry intake CFD calculation data refers to: performing CFD calculation on the variable geometry air inlet channel under different working conditions by taking matching with the double-shaft turbofan engine part level model as a reference to obtain output data of the variable geometry air inlet channel, wherein the output data comprises: the outlet total pressure recovery coefficient and the flow coefficient;
The variable geometry port throttle map refers to: and (3) a relation diagram of the total outlet pressure recovery coefficient and the flow coefficient.
More specifically, step S2 includes:
Step S201, refer to fig. 2, fig. 2 is a schematic structural diagram of a variable geometry air intake duct established in the present invention, the air intake duct adjustable component is a second compression surface, a third compression surface and an auxiliary air intake/exhaust gate, the two-shaft turbofan engine component level model obtained in step S1 is simulated to obtain required gas flow of different flight envelope points, on the premise of meeting the requirement of matching with the required flow of the engine, CFD calculation is performed on the variable geometry air intake duct to obtain output data, and the output data includes: the outlet total pressure recovery coefficient, the flow coefficient, the angles of the second and third compression surfaces of the variable geometry air inlet channel when matched and the opening of the auxiliary air inlet and outlet door; in the subsonic state, the air inlet channel assists in opening the air inlet valve and assists in closing the air outlet valve; in a supersonic state, the air inlet channel assists in closing the air inlet valve and assists in opening the air outlet valve.
In step S202, referring to fig. 3, fig. 3 is a characteristic diagram of an air intake duct published in NASA report, and it can be known that, for an air intake duct with a certain geometric feature, the relationship between the total pressure recovery coefficient and the flow coefficient is determined at the same incoming flow mach number, but the characteristic diagram only characterizes the characteristic of the air intake duct with a certain geometric feature. Therefore, according to the geometry of the variable geometry air intake passage when the variable geometry air intake passage is matched with the engine determined in step S201, the flow coefficient and the total pressure recovery coefficient calculated by the variable geometry air intake passage CFD obtained in step S201 are used to construct a variable geometry air intake passage throttle characteristic diagram under different mach numbers, and specifically, refer to fig. 4.
S3, establishing a variable geometry air inlet zero-dimensional model according to a variable geometry air inlet throttling characteristic diagram;
specifically, step S3 includes:
Step S301, under the condition of given flight Mach number and altitude, calculating a gas static temperature T S0, a gas static pressure P S0, a gas total temperature T t1 and a gas total pressure P t1 of standard atmospheric air flow after passing through a variable geometry air inlet channel;
Step S3011, obtaining the static temperature and static pressure of the inlet air flow of the variable geometry air inlet according to a fitting formula, wherein the expression is as follows:
In the formula (2) and the formula (3), h is expressed as the height of the engine operating point in m.
Step S3012, calculating the total temperature and total pressure of the inlet airflow of the variable geometry inlet according to the mach number of the incoming flow, where the expression is as follows:
Step S302, referring to FIG. 4, determining an outlet total pressure recovery coefficient sigma I according to a variable geometry air inlet throttle characteristic diagram from a flow coefficient of the variable geometry air inlet;
Step S303, calculating the variable geometry inlet channel throat gas flow according to the aerodynamic formula,
More specifically, step S303 includes the steps of:
step S3031, calculating the outlet flow of the variable geometry air inlet channel according to a aerodynamic flow formula;
In the formula (6), k is expressed as a gas insulation index, R is expressed as a gas constant, T t2、Pt2 is expressed as a total inlet outlet temperature total pressure, q (λ 2) is expressed as an inlet outlet flow rate function, and a 2 is expressed as an inlet outlet area, respectively.
Step S3032, calculating the converted flow of the outlet of the variable geometry air inlet channel according to the similarity theorem;
In formula (7), θ=t t2/288.15,δ＝Pt2/101325, the following formula is obtained:
Step S3033, defining according to the flow coefficient of the variable geometry air inlet channel As shown in fig. 2, the variable geometry inlet port outlet port reduces the flow;
step S3034, calculating total temperature and total pressure of the outlet of the variable geometry air inlet passage:
Tt2＝Tt1 (10)
Pt2＝Pt1σI (11)
step S3035, simplifying the inlet outlet reduced flow according to formulas (11), (12) and (13):
Step S3036, calculating the actual flow according to the folded flow of the outlet of the air inlet channel:
In the formula (13), W a12 is expressed as the outlet physical flow of the variable geometry inlet, and when the auxiliary inlet/outlet valve of the variable geometry inlet is closed, according to the flow continuity theorem, the throat flow of the variable geometry inlet:
In the formula (14), k is expressed as a gas adiabatic index, R is expressed as a gas constant, A c is expressed as a capture area of the variable geometry inlet, defined as a cross-sectional area of the variable geometry inlet in a vertical direction, q (lambda 1) is expressed as a variable geometry inlet flow function, Expressed as the variable geometry inlet outlet flow coefficient, P t1 is expressed as the total gas pressure at standard atmospheric pressure as the gas flows through the variable geometry inlet, and T t1 is expressed as the total gas temperature at standard atmospheric pressure as 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 outlet valve are respectively opened, wherein the expression is as follows:
In equations (15) and (16), f A (β) is expressed as auxiliary intake valve area, q (λ th) is expressed as a flow function at the variable geometry intake throat, f A (γ) is expressed as auxiliary bleed valve area, W ath is expressed as variable geometry intake throat gas flow, and W a12,β is expressed as a function of variable geometry intake outlet gas flow when the auxiliary intake valve is open; w a12,γ is a function of the variable geometry inlet outlet gas flow when the auxiliary bleed door is open.
In the step, when the auxiliary intake valve and the auxiliary air release valve are respectively opened, the method for calculating the outlet gas flow of the variable geometry air inlet channel comprises the following steps: where q (lambda th) is expressed as a variable geometry inlet throat flow function, and since the inlet airflow in the variable geometry inlet is compressed by oblique shock waves and normal shock waves, the throat Mach number can reach 1, and q (lambda th) is also 1, it is assumed that the gas flow rates at the auxiliary inlet valve and the air release valve are sonic, and the direction is consistent with the incoming flow.
And S4, performing matching operation on the double-shaft turbofan engine part level model determined in the step S1 and the variable geometry air inlet zero-dimensional model determined in the step S3 to obtain an air inlet and engine integrated model.
Specifically, the matching operation includes: adding an inlet channel outlet and fan inlet flow balance equation into the double-shaft turbofan engine part level model obtained in the step S1, and adding a first guess value, wherein the first guess value is a variable geometry inlet channel outlet flow coefficient
More specifically, the expression of the integrated model of the air inlet channel and the engine is:
In equation (17), equation P S6-PS16 =0 is expressed as: a balance equation of the outlet static pressure of the outer culvert and the outlet static pressure of the inner culvert spray pipe; equation W g42-Wa3-Wf-WHcool1-WHcool2 is expressed as: a balance equation of the high pressure turbine inlet gas flow and the compressor outlet gas flow and the fuel flow; equation W g5-Wg42-WLcool1-WLcool2 =0 is expressed as: a balance equation for the low pressure turbine inlet gas flow and the high pressure turbine outlet gas flow and the low pressure turbine bleed gas flow; equation W g9-Wg7 =0 represents the tailpipe inlet gas flow balance equation with afterburner outlet gas flow; equation η HNHT-NC-NEX =0 is expressed as the high-voltage shaft power balance equation; equation η LNLT-NF =0 is expressed as a low-voltage shaft power balance equation.
In order to verify the effectiveness of the integrated modeling method of the variable geometry air inlet and the engine, steady-state full-digital simulation of an integrated model of the air inlet and the engine under the standard atmospheric condition is carried out in a VC++6.0 environment.
The specific embodiment of the invention takes a certain small bypass ratio double-rotor boosting mixed exhaust turbofan engine 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 state, and the working point 3 is in a supersonic state.
And comparing the multipoint steady-state simulation result of the established engine model at the working point 1 with GasTurb output data, wherein the result is shown in figure 5. The error of the model simulation result and the GasTurb data is less than 1%. Fig. 5 shows that the turbofan engine model was built correctly.
And researching the influence of the adjustment of the auxiliary air inlet valve of the air inlet channel on the integrated model at the working point 2, keeping the angles of the second compression surface and the third compression surface unchanged, closing the auxiliary air release valve, adjusting the opening of the auxiliary air inlet valve to perform steady-state simulation on the integrated model, and simulating results of the thrust of the integrated model and the total pressure recovery coefficient of the air inlet channel are shown in figure 6. When the opening of the auxiliary intake valve is 40 degrees, the total pressure recovery coefficient of the air inlet channel is maximum, the integral model thrust is improved by 1.1% compared with the state without opening the auxiliary intake valve, meanwhile, the total pressure recovery coefficient of the air inlet channel is also larger than the original integral model thrust and the total pressure recovery coefficient of the air inlet channel start to be reduced after the opening of the auxiliary intake valve is continuously increased. The auxiliary intake valve is opened, so that the flow required to flow in 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 air inlet channel is changed into a subcritical state, the air inlet channel generates overflow resistance, and meanwhile, the opening of the auxiliary intake valve is increased to enable the resistance generated by the intake valve to be increased, and the thrust of the integrated model is reduced instead. Therefore, the performance of the model can be improved by the auxiliary air inlet adjustment of the air inlet passage at the working point.
And researching the influence of air inlet auxiliary air release door regulation and second-stage and third-stage compression surface regulation on the integrated model at the working point 3, and closing an air inlet auxiliary air inlet valve. Firstly, the compression surface angle is kept unchanged, and steady simulation is carried out on the integrated model by adjusting the opening of the auxiliary air release door, and the result is shown in fig. 7. When the opening of the auxiliary air release door is 20 degrees, the matching effect of the air inlet channel and the engine is best, the model thrust is maximum, the air inlet channel total pressure recovery coefficient is maintained at a higher level compared with the state that the auxiliary air release door is not opened by 1.3 percent. When the auxiliary air release door is opened, redundant air which is originally required to overflow and be discharged through the inlet of the air inlet channel can be discharged from the air release door, the overflow resistance of the air inlet channel is reduced, and the thrust of the integrated model is increased first; when the opening of the auxiliary air release door is larger than 20 degrees, the increasing amplitude of the air release resistance of the air inlet channel is larger than the decreasing amplitude of the overflow resistance of the air inlet channel, and the thrust of the integrated model is gradually decreased. And the optimal opening of the auxiliary air release door is kept unchanged, the second-stage compression surface and the third-stage compression surface are respectively adjusted, and the steady-state simulation result of the model is shown in figure 8. When the opening of the auxiliary air release door of the air inlet is optimal, the angle of the optimal second-stage compression surface of the air inlet is 5 degrees, the angle of the optimal third-stage compression surface of the air inlet is 4.5 degrees, the total pressure recovery coefficient of the air inlet is maximum at the moment, and the thrust of the integrated model is maximum. When the second compression surface and the third compression surface are gradually increased, the air inlet lip cover detached 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 compression surface angle is continuously increased after the optimal compression surface angle is reached, the air inlet lip cover detached shock wave is completely detached, and the air flow entering the air inlet channel is changed from partial subsonic speed to full subsonic speed, so that the total pressure recovery coefficient of the air inlet channel is gradually reduced. Therefore, the performance of the integrated model of the air inlet and the engine can be improved by carrying out auxiliary air discharge and compression surface adjustment on the air inlet at the working point 3.
The invention relates to an integrated modeling method for a variable geometry air inlet and an engine, which solves the problem that the traditional engine model does not consider air inlet adjustment and air inlet resistance. Compared with the traditional fixed-geometry air inlet throttling characteristic, the proposed variable-geometry air inlet throttling characteristic realizes the conversion of the variable-geometry air inlet from a CFD model to a zero-dimensional mathematical model. On the basis, the matching of the air inlet channel model and the engine model is considered, and the variable geometry air inlet channel and engine integrated model 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 contemplated by those skilled in the art within the technical scope of the present invention should be covered by the scope of the present invention. Therefore, the protection scope of the invention is subject to the protection scope of the claims.
Claims (5)
1. The integrated modeling method for the variable geometry air inlet channel and the engine is characterized by comprising the following steps of:
s1, establishing a double-shaft turbofan engine part level model according to a GasTurb characteristic diagram;
s2, performing CFD calculation on the variable geometry air inlet channel to obtain output data, and establishing a variable geometry air inlet channel throttling characteristic diagram according to the output data;
S3, establishing a variable geometry air inlet channel zero-dimensional model according to the variable geometry air inlet channel throttling characteristic diagram;
S4, matching the double-shaft turbofan engine part level model determined in the step S1 and the variable geometry air inlet zero-dimensional model determined in the step S3 to obtain an air inlet and engine integrated model;
The step S3 specifically includes:
Step S301, under the condition of given flight Mach number and altitude, calculating a gas static temperature T S0, a gas static pressure P S0, a gas total temperature T t1 and a gas total pressure P t1 of standard atmospheric air flow after passing through the variable geometry air inlet channel;
Step S302, determining an outlet total pressure recovery coefficient sigma I according to the variable geometry air inlet throttling characteristic diagram and the flow coefficient of the variable geometry air inlet;
step S303, calculating the variable geometry air inlet channel throat gas flow according to an aerodynamic formula, wherein the expression is as follows:
In the formula, k is expressed as a gas adiabatic index, R is expressed as a gas constant, A c is expressed as a capture area of the variable geometry inlet, a cross-sectional area of the variable geometry inlet in a vertical direction is defined, q (lambda 1) is expressed as a variable geometry inlet flow function, Expressed as a variable geometry inlet outlet flow coefficient, P t1 is expressed as the total pressure of the gas as it flows through the variable geometry inlet at standard atmospheric pressure, and T t1 is expressed as the total temperature of the gas as it flows through the variable geometry inlet at standard atmospheric pressure;
Step S304, calculating the outlet gas flow of the variable geometry air inlet channel when the auxiliary air inlet valve and the auxiliary air outlet valve are respectively opened, wherein the expression is as follows:
In the formula, f A (beta) is expressed as an auxiliary inlet valve area, q (lambda th) is expressed as a flow function at the throat of the variable geometry inlet channel, f A (gamma) is expressed as an auxiliary bleed valve area, W ath is expressed as a variable geometry inlet channel gas flow, and W a12,β is expressed as a function of a variable geometry inlet channel outlet gas flow when the auxiliary inlet valve is opened; w a12,γ is a function of the variable geometry inlet outlet gas flow when the auxiliary bleed door is open, P t1 is the total gas pressure at standard atmospheric pressure as gas flows through the variable geometry inlet, and T t1 is the total gas temperature at standard atmospheric pressure as gas flows through the variable geometry inlet;
In the step S4, the matching operation includes: adding an inlet channel outlet and fan inlet flow balance equation into the double-shaft turbofan engine part level model, and adding a preliminary guess value, wherein the preliminary guess value is a variable geometry inlet channel outlet flow coefficient
The expression of the integrated model of the air inlet channel and the engine is as follows:
In the formula, equation P S6-PS16 =0 is expressed as: a balance equation of the outlet static pressure of the outer culvert and the outlet static pressure of the inner culvert spray pipe; equation W g42-Wa3-Wf-WHcool1-WHcool2 =0 is expressed as: a balance equation of the high pressure turbine inlet gas flow and the compressor outlet gas flow and the fuel flow; equation W g5-Wg42-WLcool1-WLcool2 =0 is expressed as: a balance equation for the low pressure turbine inlet gas flow and the high pressure turbine outlet gas flow and the low pressure turbine bleed gas flow; equation W g9-Wg7 =0 represents the tailpipe inlet gas flow balance equation with afterburner outlet gas flow; equation η HNHT-NC-NEX =0 is expressed as the high-voltage shaft power balance equation; equation η LNLT-NF =0 is expressed as a low-voltage shaft power balance equation.
2. The method for modeling integration of a variable geometry intake and an engine according to claim 1, wherein in step S1, the GasTurb characteristic map is a two-axis turbofan engine rotating member characteristic map obtained from gas turbine performance analysis software GasTurb;
the double-shaft turbofan engine part level model refers to: firstly, establishing a mathematical model of each component of the engine according to aerodynamic thermodynamics, and then establishing a component level model of the biaxial turbofan engine 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 for modeling integration of a variable geometry intake passage and an engine according to claim 2, wherein in step S2, the CFD calculation of the variable geometry intake passage means: performing CFD calculation on the variable geometry air inlet under different working conditions by taking matching with the double-shaft turbofan engine part level model as a reference to obtain output data of the variable geometry air inlet, wherein the output data comprises: the outlet total pressure recovery coefficient and the flow coefficient;
The variable geometry port throttle map refers to: and the relation diagram of the outlet total pressure recovery coefficient and the flow coefficient.
4. The method for modeling integration of a variable geometry intake and an engine according to claim 1, wherein the step S1 specifically includes:
Step S101, firstly, a characteristic diagram of rotating parts of the double-shaft turbofan engine is obtained from gas turbine performance analysis software GasTurb, and a mathematical model of each part in the double-shaft turbofan engine is built according to aerodynamic thermodynamics, wherein each part comprises the following components: 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 exhaust 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 the biaxial turbofan engine component level model, in which the equation P S6-PS16 =0 is expressed as: a balance equation of the outlet static pressure of the outer culvert and the outlet static pressure of the inner culvert spray pipe; equation W g42-Wa3-Wf-WHcool1-WHcool2 =0 is expressed as: a balance equation of the high pressure turbine inlet gas flow and the compressor outlet gas flow and the fuel flow; equation W g5-Wg42-WLcool1-WLcool2 =0 is expressed as: a balance equation for the low pressure turbine inlet gas flow and the high pressure turbine outlet gas flow and the low pressure turbine bleed gas flow; equation W g9-Wg7 =0 represents the tailpipe inlet gas flow balance equation with afterburner outlet gas flow; equation η HNHT-NC-NEX =0 is expressed as the high-voltage shaft power balance equation; equation η LNLT-NF =0 is expressed as a low-voltage shaft power balance equation;
Step S103, iteratively solving the common working equation by adopting a Newton-Lawson method, and selecting a preliminary guess value, wherein the preliminary guess value comprises: low pressure rotational speed n L, high pressure rotational speed n H, fan pressure ratio pi F, compressor pressure ratio pi C, high pressure turbine drop pressure ratio pi HT, low pressure turbine drop pressure ratio pi LT.
5. The method for modeling integration of a variable geometry intake and an engine according to claim 4, wherein the step S2 specifically includes:
Step S201, simulating the double-shaft turbofan engine part level model obtained in the step S1 to obtain required gas flow of different flight envelope points, and carrying out 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 outlet total pressure recovery coefficient, the flow coefficient, the angles of the second and third compression surfaces of the variable geometry air inlet channel when matched and the opening of the auxiliary air inlet and outlet door;
And S202, constructing a variable geometry air inlet throttling characteristic diagram under different Mach numbers by adopting the flow coefficient and the outlet total pressure recovery coefficient.
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