Method for analyzing margin of feedback signal of key output and servo control loop of turbofan engine

Abstract

The application discloses a method for analyzing the margin of key output and servo control loop feedback signal of a turbofan engine, which comprises the following steps: based on an engine component model, the model is simplified by combining provided measured parameters, so as to establish a physical model for providing the margin; initial parameters are selected by the parameters for which the margin is provided, and balance equations under limited measured parameters are established by considering the provided measured parameters and the physical relationship between the parameters; and the designed physical model for providing the margin is used to provide the margin of key output parameters and servo control loop feedback signal in the full envelope range. The physical model for providing the margin established by the application omits time-consuming turbine component calculation and simplifies the remaining components, so that the calculation real-time performance is improved; the margin accuracy of the key output parameters is high, the margin of the servo control feedback signal can provide a reference for the FADEC system, and has a certain positive promoting effect on the design of the FADEC system margin.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine modeling and simulation, specifically involving a method for resolving the analytical redundancy of feedback signals in the key outputs and servo control loops of a turbofan engine. Background Technology

[0002] The FADEC (Fast-Independent Controller) system for aero-engines, centered on a digital electronic controller, incorporates electronic sensors and electronically controlled actuators. It boasts high computational accuracy, strong logic capabilities, and fast processing speed, exhibiting significant advantages. However, with the widespread application of FADEC systems, inherent safety shortcomings have become apparent. To address this issue, high-precision analytical redundancy output parameters are established across the entire engine envelope based on measurable engine state parameters to provide analytical redundancy and further enhance the accuracy of the FADEC system. Furthermore, addressing the lack of analytical redundancy in the servo control feedback signals of current aero-engine FADEC systems, such as the main fuel metering valve displacement, compressor guide vane angle, and nozzle angle, the current engine control variables are estimated based on measurable engine state parameters. These estimated engine control variables are then used as the analytical redundancy of the FADEC system's servo control feedback signals. Summary of the Invention

[0003] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a method based on partially measurable parameters of the engine (low-pressure speed N). L High pressure and high speed N H A method for providing high-precision analytical redundancy parameters for the FADEC system (low-pressure turbine outlet total temperature T5, low-pressure turbine outlet total pressure P5, and compressor outlet static pressure Ps3).

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A method for resolving redundancy in the feedback signal of key output and servo control loop of a turbofan engine includes the following steps:

[0006] Step A) Simplify the component-level model by using measurable state parameters and the physical relationships between parameters, thereby obtaining the analytical redundancy model of key output parameters and the analytical redundancy model of servo control feedback signal based on the physical model;

[0007] Step B) involves selecting initial values ​​for the established key output resolution model and servo control feedback signal resolution model, establishing balance equations using measurable state parameters, iteratively solving the balance equations, and then obtaining the resolution of the key output parameters and servo control feedback signal.

[0008] Preferably, the analytical redundancy model in step A) includes a simplified mathematical model of the rotating component, and the values ​​calculated by the simplified mathematical model of the rotating component are the flow rate and the total temperature and total pressure at the outlet.

[0009] Preferably, the analytical redundancy model in step A) includes simplified mathematical models of the inner and outer bypass ducts; the value calculated by the simplified mathematical model of the outer bypass duct is the static pressure at the outlet of the outer bypass duct, and the aerodynamic thermodynamic formula for the outer bypass duct is as follows:

[0010] Ps 16 =f3(0,T) 16 ,P 16 W 16 A 16 )

[0011] Where f3 is the function for calculating static pressure, W 16 P 16 T 16 Ps 16 These are the flow rate, pressure, temperature, and static pressure at the outlet of the outer duct, respectively. 16 Let be the geometric area of ​​the outer duct outlet.

[0012] The value calculated by the simplified mathematical model of the inner duct is the static pressure at the outlet of the inner duct. The formula for calculating the static pressure at the outlet of the inner duct is shown below:

[0013]

[0014] Among them, W fb It is the main fuel flow rate, W 22 W6 is the fan outlet flow rate, F6 is the internal turbine outlet flow rate, T6 and P6 are the low-pressure turbine outlet temperature and pressure, which are measured values, and A6 is the internal turbine outlet geometric area.

[0015] Preferably, the analytical redundancy model in step A) includes a simplified mathematical model of the tail nozzle, and the value calculated by the simplified mathematical model of the tail nozzle is the outlet flow rate.

[0016] Preferably, the key output parameter includes the low-pressure rotational speed N. L High pressure and high speed N H Low-pressure turbine outlet total temperature T5, low-pressure turbine outlet total pressure P5, and servo control feedback signal main fuel flow W fb Throat area A8; Low-pressure speed N L High pressure and high speed N H The initial values ​​of the initial parameters, including the low-pressure turbine outlet total temperature T5, the low-pressure turbine outlet total pressure P5, and the servo control feedback signal throat area A8, are estimated based on the input conditions, including the main fuel flow rate W. fb Select based on the current main fuel flow rate W fbThe initial guess value under the current state is obtained by interpolation calculation using similar conversion criteria; the servo control feedback signal is the main fuel flow rate W. fb The initial guess of the initial parameters is based on the measured value N of the high-voltage rotor speed. Hr The selection is based on the current measured value N of the high-voltage rotor speed. Hr The initial guess value under the current state is obtained by interpolation calculation using similar conversion criteria.

[0017] Preferably, based on the initial guesses of the key output parameters, and combined with the measured parameters and the physical relationships between the parameters, an equilibrium equation is established for the same number of finite measurement parameters. The specific equilibrium equation is shown in the following formula:

[0018] (1) Static pressure balance between the outlet of the outer bypass duct and the outlet of the inner bypass duct:

[0019] Ps 16 / Ps6-1.0=0

[0020]

[0021] (2) Balance between the tail nozzle outlet flow rate and the afterburner outlet flow rate:

[0022] W9 / W7-1.0=0

[0023] (3) Flow balance between the first three stages and the last six stages of the compressor:

[0024] W 3X / W in -1.0 = 0

[0025] (4) Balance between compressor outlet static pressure and actual value:

[0026] PS3 / PS 3r -1.0 = 0

[0027] Among them, Ps 16 Ps6 is the static pressure at the outlet of the outer bypass duct, W9 is the static pressure at the outlet of the inner bypass duct, W7 is the flow rate at the outlet of the afterburner, and W... 3X W is the outlet flow rate of the first three stages of the compressor. in Ps is the inlet flow rate of the sixth stage after the compressor, Ps3 is the static pressure at the compressor outlet, and Ps is the static pressure at the outlet. 3r This is the measured value of the static pressure at the compressor outlet.

[0028] Preferably, the servo control feedback signal is the compressor guide vane angle afa, and the initial value of the initial parameter of the compressor guide vane angle afa is selected as the fan pressure ratio π. fan Compressor inlet flow rate W comp Guide vane angle afa, compressor first three-stage pressure ratio π compi The pressure ratio π of the last six stages of the compressorcomp The specific equilibrium equation is shown below:

[0029] (1) Static pressure balance between the outlet of the outer bypass duct and the outlet of the inner bypass duct:

[0030] Ps 16 / Ps6-1.0=0

[0031]

[0032] (2) Balance between the tail nozzle outlet flow rate and the afterburner outlet flow rate:

[0033] W9 / W7-1.0=0

[0034] (3) Balance between compressor outlet static pressure and actual value:

[0035] PS3 / PS 3r -1.0 = 0

[0036] (4) Flow rate of the first three stages of the compressor and W comp Traffic balancing:

[0037] W comp / W 3X -1.0 = 0

[0038] (5) The flow rates of the last six stages of the compressor are balanced with those of the first three stages:

[0039] W 3X / W in -1.0 = 0.

[0040] Preferably, the Newton-Raphson method is used to iteratively solve the equilibrium equations.

[0041] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0042] (1) The analytical redundancy model used in this invention is based on the simplified design of the engine component-level model. Compared with the component-level model, it saves the time-consuming thermodynamic calculation of the turbine component, thus ensuring a certain level of real-time performance.

[0043] (2) This invention combines a component-level model, which has good applicability and strong adaptability within the entire envelope range and can provide good analytical redundancy parameters. Attached Figure Description

[0044] Figure 1 This is a flowchart providing a solution for resolving redundancy parameters;

[0045] Figure 2 This is a structural diagram of a certain type of twin-rotor turbofan engine;

[0046] Figure 3 This is the simulation result of the analytical redundancy value of the key output parameter tracking component-level model when the throttle lever is pushed hard at the operating point H=0km and Ma=0. (a) is the low-pressure speed N. L (b) represents the high-pressure rotational speed N. H (c) Total temperature at the low-pressure turbine outlet, T5; (d) Total pressure at the low-pressure turbine outlet, P5.

[0047] Figure 4 This is the simulation result of the analytical redundancy value of the key output parameter tracking component-level model when the throttle lever is slowly pushed under the working condition H=0km and Ma=0. (a) is the low-pressure speed N. L (b) represents the high-pressure rotational speed N. H (c) is the total temperature T5 at the low-pressure turbine outlet, and (d) is the total pressure P5 at the low-pressure turbine outlet.

[0048] Figure 5 This is the simulation result of the analytical redundancy value of the key output parameter tracking component-level model when the throttle lever is pushed hard at the operating point H=10km and Ma=0.8. (a) is the low-pressure speed N L (b) represents the high-pressure rotational speed N. H (c) is the total temperature T5 at the low-pressure turbine outlet, and (d) is the total pressure P5 at the low-pressure turbine outlet.

[0049] Figure 6 This is the simulation result of the analytical redundancy value of the key output parameter tracking component-level model when the throttle lever is slowly pushed under the operating condition H=10km and Ma=0.8. (a) is the low-pressure speed N L (b) represents the high-pressure rotational speed N. H (c) is the total temperature T5 at the low-pressure turbine outlet, and (d) is the total pressure P5 at the low-pressure turbine outlet.

[0050] Figure 7 The simulation results of the analytical redundancy value of the key output parameter tracking component-level model are shown in the figure. (a) is the low-pressure speed N. L (b) represents the high-pressure rotational speed N. H (c) is the total temperature T5 at the low-pressure turbine outlet, and (d) is the total pressure P5 at the low-pressure turbine outlet.

[0051] Figure 8 The simulation results of the analytical redundancy value of the key output parameter tracking component-level model are shown in the figure when the throttle lever is slowly pushed under the operating conditions of H=11km and Ma=1.5. (a) is the low-pressure speed N. L (b) represents the high-pressure rotational speed N. H (c) is the total temperature T5 at the low-pressure turbine outlet, and (d) is the total pressure P5 at the low-pressure turbine outlet.

[0052] Figure 9 It is the main fuel flow rate W fb Simulation results of the analytical redundancy parameter tracking the input parameter at three working points: (a) H=0km, Ma=0, rapid throttle push; (b) H=0km, Ma=0, slow throttle push; (c) H=10km, Ma=0.8, rapid throttle push; (d) H=10km, Ma=0.8, slow throttle push; (e) H=11km, Ma=1.5, rapid throttle push; (f) H=11km, Ma=1.5, slow throttle push.

[0053] Figure 10 The simulation results show the analytical redundancy parameter tracking the input parameter of the throat area A8 under three working conditions: (a) throat area changes rapidly when H=0km and Ma=0, (b) throat area changes slowly when H=0km and Ma=0, (c) throat area changes rapidly when H=10km and Ma=0.8, (d) throat area changes slowly when H=10km and Ma=0.8, (e) throat area changes rapidly when H=11km and Ma=1.5, and (f) throat area changes slowly when H=11km and Ma=1.5.

[0054] Figure 11 The simulation results show the analytical redundancy parameter tracking input parameters of the compressor guide vane angle afa at three operating points: (a) guide vane angle abruptly changes when H=0km and Ma=0; (b) guide vane angle gradually changes when H=0km and Ma=0; (c) guide vane angle abruptly changes when H=10km and Ma=0.8; (d) guide vane angle gradually changes when H=10km and Ma=0.8; (e) guide vane angle abruptly changes when H=11km and Ma=1.5; and (f) guide vane angle gradually changes when H=11km and Ma=1.5. Detailed Implementation

[0055] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings.

[0056] The present invention first simplifies the component-level model of the engine by using measurable state parameters and the physical relationships between these parameters, thereby obtaining an analytical redundancy model based on the physical model. Next, initial values ​​are selected for the established analytical redundancy model, and equilibrium equations are established using the measurable state parameters. The Newton-Raphson method is then used for iterative solving to obtain the analytical redundancy of key output parameters and servo control feedback signals. A flowchart providing the analytical redundancy parameter scheme is available. Figure 1 .

[0057] The specific embodiment of the present invention takes the low-pressure speed N, a key output parameter of a certain type of turbofan engine, as an example. L High pressure and high speed N HLow-pressure turbine outlet total temperature T5, low-pressure turbine outlet total pressure P5, and servo control feedback signal main fuel flow W fb Taking the throat area A8 and compressor guide vane angle afa as examples to provide analytical margin, Figure 2 The diagram shows the structure of a certain type of dual-rotor turbofan engine. The method for resolving the analytical redundancy of the key output parameters and servo control loop feedback signals includes the following steps:

[0058] Step A) Based on the engine component-level model, using the provided measurable parameters and the physical relationships between the parameters, the component-level model is simplified and a simplified mathematical model of the analytical redundancy of the key output parameters and servo control feedback signals is established.

[0059] Step B), design the key output parameter: low-pressure speed N L High pressure and high speed N H Low-pressure turbine outlet total temperature T5, low-pressure turbine outlet total pressure P5, and servo control feedback signal main fuel flow W fb The analytical redundancy scheme for the throat area A8 and the compressor guide vane angle afa was proposed and verified by simulation.

[0060] The detailed steps of step A) are as follows:

[0061] Step A1) Establish a simplified mathematical model of the rotating component.

[0062] Compared to the mathematical models of rotating components in conventional component-level models, the simplified mathematical model of rotating components in this analytical redundancy component-level model eliminates the need for turbine component calculations. Therefore, the power conservation equation is omitted from the equilibrium equations. Consequently, in the fan and compressor components, no power calculations are required; only the flow rate and total temperature and pressure at the outlet need to be calculated. Taking the compressor component as an example, the aerodynamic thermodynamic formulas used in the analytical redundancy model of rotating components are introduced below.

[0063] Calculate the similar equivalent speeds of compressor components:

[0064]

[0065] Interpolating the compressor characteristic curve yields the actual flow rate and efficiency of the compressor.

[0066]

[0067] Where f1 and f2 are interpolation functions for flow rate and efficiency, C mcomp and C ηcomp These are the flow correction factor and the efficiency correction factor, π. c This refers to the compressor pressure ratio.

[0068] Compressor outlet total pressure P3:

[0069] P3 = P25 ×π c

[0070] Compressor outlet total temperature T3:

[0071]

[0072] Among them, H 25 H1 is the compressor inlet enthalpy, H2 is the compressor outlet enthalpy, and H3 is the compressor outlet enthalpy. 3,id For the ideal enthalpy at the compressor outlet, S 25 S is the compressor inlet entropy. 3,id Let be the ideal entropy at the compressor outlet.

[0073] After considering the venting gas, the compressor outlet flow rate is:

[0074]

[0075] Among them, W D It is the total bleed air flow rate of the intermediate and final stages of the compressor.

[0076] The compressor outlet static pressure is:

[0077] Ps3 = f3(0,T3,P3,W3,A3)

[0078] Where f3 is the static pressure calculation function, and A3 is the compressor outlet geometric area.

[0079] Step A2) Establish a simplified mathematical model of the inner and outer ducts.

[0080] The equilibrium equations utilize the static pressure conservation of the inner and outer ducts, so only the static pressure needs to be calculated in the simplified model of the inner and outer ducts, reducing the complexity and corresponding time consumption.

[0081] In establishing the simplified mathematical model of the bypass duct component, the most important parameter is the static pressure at the bypass outlet. Therefore, the calculation of other parameters of the bypass duct can be omitted, and the aerodynamic thermodynamic formula of the bypass duct mainly adopts the following formula:

[0082] The specific calculation expression for the airflow parameters at the outlet of the bypass duct is as follows:

[0083] Ps 16 =f3(0,T) 16 ,P 16 W 16 A 16 )

[0084] Among them, W 16 P 16 T 16 Ps 16 These are the flow rate, pressure, temperature, and static pressure at the outlet of the outer duct, respectively. 16Let be the geometric area of ​​the duct outlet.

[0085] When establishing the simplified mathematical model of the inner duct, since the calculation of the combustion chamber and turbine components is avoided, the static pressure at the inner duct outlet only needs to be calculated based on the measured values ​​of the total temperature and total pressure at the inner duct outlet, which greatly reduces the corresponding time consumption. The formula for calculating the static pressure is shown below:

[0086] Calculate the static pressure at the outlet of the cavity:

[0087]

[0088] Among them, W fb It is the main fuel flow rate, W 22 W6 is the fan outlet flow rate, F6 is the internal turbine outlet flow rate, T6 and P6 are the low-pressure turbine outlet temperature and pressure, which are measured values, and A6 is the internal turbine outlet geometric area.

[0089] Step A3) Establish a simplified mathematical model of the tail nozzle.

[0090] To further reduce the time consumption of the established analytical redundancy model, the aerodynamic and thermodynamic calculations for the tail nozzle are simplified. The aerodynamic and thermodynamic calculation process used in the first iteration of each step is shown in the following equation:

[0091] Total pressure P9, total temperature T9, and critical static pressure P at the nozzle exit s9,cr :

[0092]

[0093] outlet static pressure P s9 Outlet airflow Ma:

[0094]

[0095]

[0096] Export flow W9:

[0097]

[0098] Where q(Ma) and K m satisfy:

[0099]

[0100] During the remaining iterations, when the initial value of the disturbance is guessed, since the disturbance amount is extremely small, it will not have much impact on the state judgment of the tail nozzle. Therefore, there is no need to recalculate the static pressure and Mach number to judge the state of the tail nozzle. In addition, there is no need to calculate the exit section parameters during the iteration process, only the flow rate needs to be calculated. Therefore, during the disturbance process, only the formula for calculating the exit flow rate W9 needs to be used.

[0101] Step A4) Establish simplified mathematical models for other components.

[0102] The intake duct component is used to capture incoming airflow, provide inlet flow, and ensure the normal operation of the core engine. Its construction method is similar to that of the component-level model, and the formulas used are also the same as those for the intake duct of the component-level model, so they will not be elaborated here.

[0103] The function of the mixing chamber component is to uniformly mix the internal and external bypass gas flows, thereby improving gas utilization efficiency. In the analytical redundancy model, the main task is to calculate the outlet flow rate, pressure, and temperature. Therefore, compared to the component-level model, only the formulas for calculating the outlet flow rate, temperature, and pressure in the mixing chamber need to be retained.

[0104] The afterburner can further increase the gas temperature before the exhaust nozzle, thereby increasing the exhaust velocity and thus improving engine thrust. In the analytical redundancy model, only the outlet flow rate, pressure, and temperature need to be calculated; therefore, only the formulas for calculating the outlet flow rate, pressure, and temperature need to be retained.

[0105] The detailed steps of step B) are as follows:

[0106] Step B1), design the key output parameter low-pressure speed N L High pressure and high speed N H Low-pressure turbine outlet total temperature T5, low-pressure turbine outlet total pressure P5, and servo control feedback signal main fuel flow W fb A8 resolution margin scheme for throat area.

[0107] Step B1.1) involves selecting initial parameters and initial guess values ​​based on the parameters that require resolution margin.

[0108] Based on the physical model established in the previous step for providing key output parameters and servo control feedback signal resolution redundancy, the selection of initial parameters should refer to the parameters that require resolution redundancy at this time, as shown in Table 1.

[0109] When the parameter requiring resolution margin is the key output parameter, the low-pressure speed N L High pressure and high speed N H When the low-pressure turbine outlet total temperature T5, the low-pressure turbine outlet total pressure P5, and the servo control feedback signal throat area A8 are given, the initial guess values ​​of the initial parameters are based on the input conditions, namely the main fuel flow rate W. fb Select based on the current main fuel flow rate W fb The initial guess value under the current state is obtained by interpolation calculation using similar conversion criteria.

[0110] When the parameter requiring resolution redundancy is the servo control feedback signal, the main fuel flow rate W... fbAt that time, the initial guess of the initial parameters is based on the measured value N of the high-voltage rotor speed. Hr The selection is based on the current measured value N of the high-voltage rotor speed. Hr The initial guess value under the current state is obtained by interpolation calculation using similar conversion criteria.

[0111] Table 1. Key Output Parameters and Initial Parameters Selected for Resolution Redundancy of Some Servo Control Feedback Signals

[0112]

[0113] Where, π fan Indicates the fan pressure ratio, π compi π represents the pressure ratio of the first three stages of the compressor. comp This represents the pressure ratio of the last six stages of the compressor. Since the guide vane angles (afa) of the first three stages of the compressor in this type of turbofan engine are adjustable, while the guide vane angles of the last six stages are not, for ease of modeling, the pressure ratio (π) of the first three stages of the compressor is selected during modeling. compi and the subsequent six-stage pressure ratio π comp The flow balance equation is used as a constraint between them.

[0114] Step B1.2): Based on the selected initial parameters, and combined with the measured parameters and the physical relationships between the parameters, establish the equilibrium equations under the same number of finite measured parameters.

[0115] To simplify calculations and improve operating speed, a simplified physical model based on a component-level model was established. Compared with the component-level model, this model eliminates the relatively time-consuming calculations of turbine components, thus eliminating the need to select a power balance equation in the selection of balance equations. Furthermore, considering the provided measurable parameters and the physical relationships between them, two flow balance equations and one static pressure balance equation are retained in form. Based on the characteristic parameters, a balance equation is designed between the calculated and measured static pressure values ​​of the model. The specific balance equation is shown below:

[0116] (1) Static pressure balance between the outlet of the outer bypass duct and the outlet of the inner bypass duct:

[0117] Ps 16 / Ps6-1.0=0

[0118] (2) Balance between the tail nozzle outlet flow rate and the afterburner outlet flow rate:

[0119] W9 / W7-1.0=0

[0120] (3) Flow balance between the first three stages and the last six stages of the compressor:

[0121] W 3X / W in -1.0 = 0

[0122] (4) Balance between compressor outlet static pressure and actual value:

[0123] PS3 / PS 3r -1.0 = 0

[0124] Among them, Ps 16 Ps6 is the static pressure at the outlet of the outer bypass duct, W9 is the static pressure at the outlet of the inner bypass duct, W7 is the flow rate at the outlet of the afterburner, and W... 3X W is the outlet flow rate of the first three stages of the compressor. in Ps is the inlet flow rate of the sixth stage after the compressor, Ps3 is the static pressure at the compressor outlet, and Ps is the static pressure at the outlet. 3r This is the measured value of the static pressure at the compressor outlet.

[0125] Furthermore, the solution for Ps6 can be directly obtained using thermodynamic calculations based on known and initial parameters, without needing to operate the turbine components according to the airflow conditions. This method effectively avoids complex aerodynamic and thermodynamic calculations inside the turbine. Theoretically, compared to component-level models, it significantly reduces computation time, providing model conditions for real-time airborne applications.

[0126] Based on the selected initial parameters and the established equilibrium equations, the Newton-Raphson method is used for iterative solution, thereby providing analytical redundancy.

[0127] Step B2) Design a solution for the analytical redundancy of the compressor guide vane angle afa in the servo control feedback signal.

[0128] Since the compressor guide vane angle afa has a significant impact on the flow rate and efficiency of compressor components, but a relatively small impact on other components, the design of the analytical redundancy scheme for the compressor guide vane angle afa is divided into two steps, with separate iterative calculations for each compressor component.

[0129] Step B2.1) focuses on the gas flow rate through the bypass to obtain two parameters: fan pressure ratio and compressor inlet flow rate.

[0130] First, select the fan pressure ratio π. fan and compressor inlet flow rate W comp With two initial parameters, focusing on the gas flow rate through the bypass duct, and considering only six components—the intake duct, fan, bypass duct, mixing chamber, afterburner, and exhaust nozzle—two remaining equilibrium equations are selected:

[0131] (1) Static pressure balance between the outlet of the outer bypass duct and the outlet of the inner bypass duct:

[0132] Ps 16 / Ps6-1.0=0

[0133] (2) Balance between the tail nozzle outlet flow rate and the afterburner outlet flow rate:

[0134] W9 / W7-1.0=0

[0135] The solution for Ps6 directly utilizes known sensor and initial parameters through thermodynamic calculations, eliminating the need to operate the turbine components according to the airflow conditions. This avoids the complex aero-thermodynamic calculations within the turbine. Using the two equations above, the Newton-Raphson method is employed for iterative solutions to obtain the fan pressure ratio π. fan and compressor inlet flow rate W comp Two parameters.

[0136] Step B2.2) focuses only on the gas flow inside the compressor components to obtain the analytical redundancy parameter of the compressor guide vane angle afa in the servo control feedback signal.

[0137] Obtain the fan pressure ratio π fan and compressor inlet flow rate W comp After that, the inlet flow rate, temperature, and pressure of the compressor components are known quantities. Considering only a single compressor component, we select the guide vane angle afa and the pressure ratio π of the first three stages of the compressor. compi The pressure ratio π of the last six stages of the compressor comp As initial parameters, two flow balance equations and one balance equation between the calculated and measured static pressure values ​​of the compressor are designed based on the characteristic parameters. The specific balance equations are shown in the following formula:

[0138] (1) Balance between compressor outlet static pressure and actual value:

[0139] PS3 / PS 3r -1.0 = 0

[0140] (2) Flow rate of the first three stages of the compressor and W comp Traffic balancing:

[0141] W comp / W 3X -1.0 = 0

[0142] (3) The flow rates of the last six stages of the compressor are balanced with those of the first three stages:

[0143] W 3X / W in -1.0 = 0

[0144] Using the above three equations, the Newton-Raphson method is employed for iterative solution to obtain the pressure ratio π of the first three stages of the compressor. compi The pressure ratio π of the last six stages of the compressor compTwo parameters and the analytical redundancy parameter, guide vane angle afa. At this point, the analytical redundancy scheme design for the compressor guide vane angle afa of the servo control feedback signal is complete.

[0145] Step B3), after establishing the analytical redundancy of the key output and servo control loop feedback signals of the turbofan engine, now the key output parameter low-pressure speed N is... L High pressure and high speed N H Low-pressure turbine outlet total temperature T5, low-pressure turbine outlet total pressure P5, and servo control feedback signal main fuel flow W fb The analytical redundancy parameters, such as throat area A8, compressor guide vane angle afa, and the tracking performance of component-level models and actual input parameters, were simulated and verified.

[0146] Step B3.1), for the key output parameter low-pressure speed N L High pressure and high speed N H The analytical redundancy parameters of the low-pressure turbine outlet total temperature T5 and the low-pressure turbine outlet total pressure P5 are used to simulate and verify the tracking performance of the component-level model.

[0147] Select the following operating points, denoted as test points 1, 2, and 3, and perform single-point steady-state accuracy verification on the three test points.

[0148] Test point 1: H = 0km, Ma = 0, W fb =0.2kg / s, A8=0.41m 2 afa = 7.79°;

[0149] Test point 2: H = 10km, Ma = 0.8, W fb =0.4kg / s, A8=0.218m 2 afa = 0°;

[0150] Test point 3: H = 11km, Ma = 1.5, W fb =0.5kg / s, A8=0.191m 2 ,afa=0.35°.

[0151] For the three selected test points, steady-state simulation tests were conducted in both the component-level model and the analytical redundancy model to check the analytical redundancy value of the engine's key outputs (low-pressure speed N). L High pressure and high speed N H The total temperature at the low-pressure turbine outlet (T5) and the total pressure at the low-pressure turbine outlet (P5) are calculated. An error comparison analysis is performed between the component-level model output and the analytical redundancy values ​​of the key output parameters, as shown in Table 2.

[0152] Table 2 Comparison of steady-state points of analytical redundancy values ​​of engine component-level model output and key output parameters (%)

[0153]

[0154] As can be seen from the table, the steady-state error of the engine component-level model and the analytical redundancy value of the key output parameters are both less than 1%, proving that the method can provide good analytical redundancy parameters at the steady-state point.

[0155] The dynamic simulation results at the working point H=0km, Ma=0 are as follows: Figure 3 , 4 As shown in the figure. It can be seen from the figure that under the conditions of rapid and slow throttle input, the low-pressure speed N... L High pressure and high speed N H The analytical margin parameters for the total temperature T5 at the low-pressure turbine outlet and the total pressure P5 at the low-pressure turbine outlet can track the trajectory of the throttle lever change in the component-level model very well. The steady-state error is within 1%, and the dynamic error is no more than 5%, indicating that the proposed method for providing analytical margin for key output parameters has high dynamic and steady-state accuracy at this operating point.

[0156] The dynamic simulation results under the operating condition H=10km and Ma=0.8 are as follows: Figure 5 , 6 As shown in the figure. It can be seen from the figure that under the conditions of rapid and slow throttle input, the low-pressure speed N... L High pressure and high speed N H The analytical margin parameters for the total temperature T5 at the low-pressure turbine outlet and the total pressure P5 at the low-pressure turbine outlet can track the trajectory of the throttle lever change in the component-level model very well. The steady-state error is within 1%, and the dynamic error is no more than 5%, indicating that the proposed method for providing analytical margin for key output parameters has high dynamic and steady-state accuracy at this operating point.

[0157] The dynamic simulation results under the operating condition H=11km and Ma=1.5 are as follows: Figure 7 , 8 As shown in the figure. It can be seen from the figure that under the conditions of rapid and slow throttle input, the low-pressure speed N... L High pressure and high speed N H The analytical margin parameters for the total temperature T5 at the low-pressure turbine outlet and the total pressure P5 at the low-pressure turbine outlet can track the trajectory of the throttle lever change in the component-level model very well. The steady-state error is within 1%, and the dynamic error is no more than 2%, indicating that the proposed method for providing analytical margin for key output parameters has high dynamic and steady-state accuracy at this operating point.

[0158] In summary, the key output parameter is the low-pressure speed N. L High pressure and high speed N HThe total temperature at the low-pressure turbine outlet (T5) and the total pressure at the low-pressure turbine outlet (P5) show good accuracy at all three flight state points within the envelope, and also exhibit high dynamic steady-state accuracy under large fuel step changes and linear changes, indicating that the proposed method for providing analytical redundancy for key output parameters has good usability within the envelope.

[0159] Step B3.2), the servo control feedback signal for the main fuel flow W fb The analytical redundancy parameters of throat area A8 and compressor guide vane angle afa are used to simulate and verify the tracking of real input parameters.

[0160] Three typical operating points were selected: operating point 1 (H=0km, Ma=0), operating point 2 (H=10km, Ma=0.8), and operating point 3 (H=11km, Ma=1.5). The simulation verification of the analytical redundancy parameter of the servo control feedback signal tracking the actual input parameter was carried out.

[0161] At the above three operating points, the main fuel flow rate W fb Under the conditions of step change and linear change, how does its analytical redundancy parameter track the changes of the actual input parameter? Figure 9 As shown in the figure. From the figure, we can see that the main fuel flow rate W... fb The analytical redundancy parameter values ​​can track the changes in the actual input parameters of the component-level model very well, and they also have a consistent trend with the input parameters when the range of input parameter changes is large. This shows that this method of providing analytical redundancy for servo control feedback signals can provide a reference for servo control systems.

[0162] Under the above three operating conditions, with the throat area A8 undergoing both step and linear changes, the analytical redundancy parameter tracks the changes in the actual input parameters as follows: Figure 10 As shown in the figure, the analytical margin parameter value of the throat area A8 can track the changes of the actual input parameters of the component-level model very well, and it also has a consistent trend with the input parameters when the range of input parameter changes is large. This indicates that this method of providing analytical margin for servo control feedback signals can provide a reference for servo control systems.

[0163] Under the above three operating conditions, with both step and linear changes in the compressor guide vane angle afa, the analytical redundancy parameter tracks the changes in the actual input parameter as follows: Figure 11 As shown in the figure, the analytical margin parameter value of the compressor guide vane angle afa can track the changes of the actual input parameters of the component-level model very well, and it also has a consistent trend with the input parameters when the range of input parameter changes is large. This indicates that this method of providing analytical margin for servo control feedback signals can provide a reference for servo control systems.

[0164] In summary, the servo control feedback signal is the main fuel flow rate W. fb The throat area A8 and the compressor guide vane angle afa all have good accuracy at the three operating points, and they also have a consistent trend of change when the input parameters vary over a large range, indicating that the analytical margin provided by this method can provide a reference for the servo control system.

[0165] In summary, the analytical redundancy of the feedback signal in the key output and servo control loop of the turbofan engine proposed in this paper is crucial for the low-pressure speed N of the key output parameter. L High pressure and high speed N H Low-pressure turbine outlet total temperature T5, low-pressure turbine outlet total pressure P5, and servo control feedback signal main fuel flow W fb The throat area A8 and compressor guide vane angle afa have strong applicability and play a positive role in promoting the study of analytical margin.

[0166] It should be noted that the above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations and substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for analyzing the margins of a feedback signal of a critical output and servo control loop of a turbofan engine, characterized in that, The method comprises the following steps: Step A), simplifying the component-level model through the measurable state parameters and the physical relationship between the parameters, thereby obtaining a key output parameter analytical margin model based on a physical model and a servo control feedback signal analytical margin model; Step B), selecting the initial guess value for the established key output analytical margin model and the servo control feedback signal analytical margin model, respectively, and establishing the balance equation by using the measurable state parameters, iteratively solving the balance equation, and further obtaining the analytical margin of the key output parameter and the servo control feedback signal; The key output parameters include low-pressure rotating speed N L , high-pressure rotating speed N H , low-pressure turbine outlet total temperature T5, low-pressure turbine outlet total pressure P5, and servo control feedback signal main fuel flow W fb , throat area A8; low-pressure rotating speed N L , high-pressure rotating speed N H , low-pressure turbine outlet total temperature T5, low-pressure turbine outlet total pressure P5, and initial parameter initial guess value of servo control feedback signal throat area A8 are selected according to input condition main fuel flow W fb , and interpolation calculation is performed according to current main fuel flow W fb and similar conversion criteria to obtain initial guess value under current state. Servo control feedback signal main fuel flow W fb The initial parameter of the initial guess value is based on the input high-pressure rotor speed measurement N Hr Select, according to the current high-pressure rotor speed measurement N Hr And similar conversion criteria for interpolation calculation to obtain the initial guess value under the current state; According to the initial guess value of the key output parameter, the balance equation under the same number of finite measurement parameters is established in combination with the measured parameters and the physical relationship between the parameters, and the specific balance equation is shown in the following formula: The bypass outlet and the inner bypass outlet static pressure balance: Ps 16 / Ps6-1.0=0 The nozzle outlet flow and the afterburner outlet flow balance: W9 / W7-1.0=0 The flow balance of the first three stages and the last six stages of the compressor: W 3X / W in -1.0 = 0 The balance of the compressor outlet static pressure and the true value: Ps3 / Ps 3r -1.0 = 0 where Ps is the outer bypass exit static pressure, Ps6 is the inner bypass exit static pressure, W9 is the nozzle exit flow, W7 is the afterburner exit flow, W 16 is the compressor first three stage exit flow, W 3X is the compressor first three stage exit flow, W in is the compressor first three stage exit flow, W 3r is the compressor first three stage exit flow, W The servo control feedback signal is the compressor guide vane angle afa, and the initial parameter guess value of the compressor guide vane angle afa is selected as the fan pressure ratio π fan , the compressor inlet flow rate W comp , the guide vane angle afa, the compressor front three-stage pressure ratio π compi , the compressor rear six-stage pressure ratio π comp , and the specific balance equation is as shown in the following formula: The bypass outlet and the inner bypass outlet static pressure balance: Ps 16 / Ps6-1.0=0 The nozzle outlet flow and the afterburner outlet flow balance: W9 / W7-1.0=0 The balance of the compressor outlet static pressure and the true value: Ps3 / Ps 3r -1.0 = 0 Compressor front three stage flow vs. W comp Flow balance: W comp / W 3X -1.0 = 0 The balance of the flow of the last six stages and the flow of the first three stages of the compressor: W 3X / W in -1.0 = 0.

2. The method of claim 1, wherein: The analytical margin model in the step A) comprises a rotating component simplified mathematical model, and the value calculated by the rotating component simplified mathematical model is the flow and the total temperature and total pressure of the outlet.

3. The method of claim 1, wherein: The analytical margin model in the step A) comprises an inner and outer bypass simplified mathematical model; the value calculated by the outer bypass simplified mathematical model is the outer bypass outlet static pressure, and the aerodynamic thermodynamic formula of the outer bypass adopts the following formula: Ps 16 = f3(0, T 16 , P 16 , W 16 , A 16 ) where f3 is a calculated function of static pressure, W 16 , P 16 , T 16 , Ps 16 are the mass flow rate, pressure, temperature and static pressure at the exit of the outer duct respectively, A 16 is the exit area of the outer duct. The value calculated by the inner bypass simplified mathematical model is the inner bypass outlet static pressure, and the formula for calculating the inner bypass outlet static pressure is shown in the following formula: where W fb is the main fuel flow, W 22 is the fan exit flow, W6 is the core exit flow, f6 is the core exit fuel-air ratio, T6 and P6 are the low pressure turbine exit temperature and pressure, respectively, and A6 is the core exit geometric area. where W fb is the main fuel flow, W 22 is the fan exit flow, W6 is the core exit flow, f6 is the core exit fuel-air ratio, T6 and P6 are the low pressure turbine exit temperature and pressure, respectively, and A6 is the core exit geometric area.

4. The method of claim 1, wherein: The analytical margin model in the step A) comprises a nozzle simplified mathematical model, and the value calculated by the nozzle simplified mathematical model is the outlet flow.

5. The method of claim 1, wherein: The Newton-Lapson method is used to iteratively solve the balance equation.

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