Initial guess value model calculation method for steady-state simulation calculation of overall performance of engine

Abstract

The invention provides an initial guess value model calculation method for steady-state simulation calculation of the overall performance of an engine, and the method comprises the steps: extracting a specific performance parameter conversion table and a thermodynamic calculation independent variable parameter table according to a simulation calculation result of a full-envelope working condition; initial guess value calculation is carried out, and a target variable value is given; assigning a low-pressure conversion rotation speed initial value and calculating a target variable to obtain a calculated target variable value; calculating the target variable deviation of the given target variable value and the calculated target variable value, judging whether the target variable deviation meets the error precision or not, and calculating an initial guess value parameter according to the low-pressure conversion rotating speed initial value if the precision requirement is met; and if the precision requirement is not met, correcting the low-pressure conversion rotating speed to obtain a corrected low-pressure conversion rotating speed value, and repeating the steps until the low-pressure conversion rotating speed value with the target variable deviation meeting the error precision is obtained. And according to the low-voltage conversion rotating speed value, interpolating to obtain a specific performance parameter conversion table, and calculating an initial guess value parameter.

Description

Technical Field

[0001] This invention relates to the field of aero-engines, and more specifically to the field of overall performance steady-state calculation modeling methods. Background Technology

[0002] The calculation of aero-engine performance simulation models is a common method in engine design. The overall performance steady-state simulation calculation model of aero-turbofan engines is mainly used for the steady-state performance calculation within the entire working envelope of aero-engines.

[0003] In the initial calculation, initial values ​​for the unknown independent variables need to be estimated. Based on the estimated initial values, a set of iterative error values ​​is obtained through iterative calculations. Based on the aforementioned error equations, the convergent solution is gradually approximated. Due to the limitations of numerical iterative methods, the accuracy of the estimated initial values ​​has a significant impact on the stability of the steady-state calculation: the smaller the difference between the estimated value and the actual value, the easier the calculation is to converge; conversely, a longer iteration time is required, and divergence may even occur, leading to model non-convergence. The iteration step size also affects the convergence of the iteration: the smaller the iteration step size, the better the convergence, but this comes at the cost of sacrificing convergence speed.

[0004] How to establish an initial guess model with high accuracy and high computational stability is an urgent problem to be solved. Summary of the Invention

[0005] One objective of this invention is to provide a method for calculating the initial guess value model for steady-state simulation of overall engine performance, which can calculate the initial guess value with high accuracy and high computational stability.

[0006] To achieve the above objectives, the initial guess value calculation method for the steady-state simulation calculation of the overall engine performance includes the following steps: S1. Based on the simulation calculation results under the full envelope condition, extract the conversion table of specific performance parameters and the table of independent variable parameters for thermodynamic calculation; S2. Perform the initial guess value calculation, including the following steps:

[0007] S21. Given the value of the target variable;

[0008] S22. Assign initial values ​​to the low-pressure conversion speed and calculate the target variable to obtain the calculated target variable value;

[0009] S23. Calculate the target variable deviation between the given target variable value and the calculated target variable value, and determine whether the target variable deviation meets the error accuracy. If it meets the accuracy requirements, calculate the initial guess parameter based on the initial value of the low-pressure converted speed.

[0010] S24. If the accuracy requirements are not met, correct the low-pressure converted speed to obtain the corrected low-pressure converted speed value, and repeat steps S22-S23 until the low-pressure converted speed value that meets the error accuracy of the target variable deviation is obtained.

[0011] S25. Based on the low-pressure converted speed value, interpolate the specific performance parameter conversion table to calculate the initial guess parameter.

[0012] In one or more embodiments, the method for correcting the low-pressure converted speed is as follows: S241. Add 1% to 3% to the existing low-pressure converted speed to obtain a first corrected low-pressure converted speed; S242. Repeat steps S22-S23 to determine whether the deviation of the target variable meets the error accuracy. If the accuracy requirement is met, calculate the initial guess parameter based on the initial value of the low-pressure converted speed; if the accuracy requirement is not met, continue to correct the low-pressure converted speed.

[0013] In one or more embodiments, in step S24, it is also necessary to determine whether the value of the low-pressure converted speed exceeds the limit. The determination method includes the following steps: calculating the adjustment amount of the low-pressure converted speed value; determining whether the absolute value of the adjustment amount is greater than the deviation threshold, wherein the deviation threshold is 5% to 10% of the low-pressure converted speed value; when the adjustment amount is greater than the deviation threshold, the low-pressure converted speed value is superimposed on the deviation threshold; when the adjustment amount is less than the deviation threshold, the low-pressure converted speed value is superimposed on the adjustment amount; determining whether the superimposed and updated low-pressure converted speed value exceeds the initial guess calculation limit; when it exceeds the initial guess calculation limit, the low-pressure converted speed value is corrected to the initial guess calculation limit, and the corrected value is used to perform the calculation in step S242; when it does not exceed the initial guess calculation limit, the updated low-pressure converted speed value is used to perform the calculation in step S242.

[0014] In one or more embodiments, in step S22, the step of determining the value of the target variable is as follows: given the inlet conditions, the incoming flow parameters are calculated; according to different solution objectives, different solution steps are used to obtain the calculated value of the target variable.

[0015] In one or more embodiments, the number table is a three-dimensional or four-dimensional number table.

[0016] In one or more embodiments, the interpolation step in the data table is as follows: the data table is a three-dimensional data table, which includes a first parameter, a second parameter, and a third parameter, arranged in ascending order; the position of a known first parameter in the three-dimensional data table is retrieved, and the two first parameter values ​​closest to the known first parameter are selected; based on the two first parameter values, the corresponding second parameter values ​​under the same first parameter value are retrieved respectively, and the positions of the two second parameter values ​​closest to the corresponding second parameter value in the three-dimensional data table are selected; based on the two second parameter values, the corresponding third parameter values ​​under the same second parameter value are retrieved respectively, and the positions of the two third parameter values ​​closest to the corresponding third parameter value in the three-dimensional data table are selected; according to the eight third parameter values, the corresponding target parameter at the corresponding position in the data table is found, and the target variable value is obtained by interpolation, wherein the interpolation steps are: based on the two third parameter values, the third parameter dimension is eliminated; based on the two second parameter values, the second parameter dimension is eliminated; based on the two first parameter values, the first parameter dimension is eliminated; and the target interpolation is obtained.

[0017] In one or more embodiments, using The elimination of the third parameter dimension is defined as follows: RN1R11 and LN1R11 are two adjacent third parameter values ​​obtained based on the same corresponding third parameter value, XX1 and XX2 are the corresponding target parameters of RN1R11 and LN1R11 at the corresponding positions in the table, and XY1 is the value of the corresponding position parameter after eliminating the third parameter dimension.

[0018] In one or more embodiments, using Eliminate the second parameter dimension, where RXM1 and LXM1 are two adjacent second parameter values ​​obtained based on the same corresponding second parameter value, XY2 and XY1 are the corresponding target parameters of RXM1 and LXM1 at the corresponding positions in the table, and XZ1 is the value of the corresponding position parameter after eliminating the second parameter dimension.

[0019] In one or more embodiments, using Elimination is performed using the first parameter dimension, where RALT and LALT are two adjacent first parameter values ​​obtained from the same corresponding first parameter value, XZ2 and XZ1 are the corresponding target parameters of RALT and LALT at their respective positions in the table, and β FAN That is the target value.

[0020] In one or more embodiments, the first parameter is flight altitude, the second parameter is Mach number, and the third parameter is low-pressure equivalent rotational speed.

[0021] The above method considers the requirement for robustness of calculations within the entire envelope. It selects the low-pressure shaft equivalent speed N1R, which has good convergence, as the target value for the solution, and uses a less accurate initial guess value for calculation, generating model input characteristics suitable for calculating the initial guess value within the entire envelope. Based on the aforementioned characteristic table, a calculation model for the initial guess value of the entire envelope is established. Within the entire envelope, different tables are selected for different solution targets, and the target deviation value is calculated in a specific form. An iterative process is used to establish the correspondence between the low-pressure equivalent speed N1R and the target value, thus providing the low-pressure equivalent speed N1R value under the corresponding characteristic target value. Referring to the aforementioned N1R value and combining it with the table of thermodynamic calculation independent variable parameters, a relatively accurate initial guess value for the engine steady-state performance model is given, facilitating model calculation convergence and demonstrating good steady-state model calculation stability. Attached Figure Description

[0022] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, wherein:

[0023] Figure 1 This is a flowchart of the calculation method for the initial guess model in the steady-state simulation calculation of the overall engine performance;

[0024] Figure 2 This is a flowchart for calculating the initial guess value;

[0025] Figure 3 This is a schematic diagram showing the locations of the three types of parameters used in the number table interpolation. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0027] It should be noted that these and other accompanying drawings are merely examples and are not drawn to scale, and should not be construed as limiting the scope of protection of the present invention.

[0028] Improving the modeling accuracy of aero-engine performance simulation models will directly drive the overall improvement of aero-engine design. Aero-engine performance simulation models are applied throughout the entire engine lifecycle, enabling steady-state, unsteady-state, and real-time performance calculations. They can rapidly provide aircraft customers, engine design and component design departments, and service departments with a large amount of reliable performance prediction data from engine design and testing to its operational use. Applying aero-engine performance simulation software can significantly reduce R&D costs, improve the overall system design, accelerate engineering progress, support product airworthiness, and facilitate fault diagnosis and health management.

[0029] After determining the engine dimensions and design point parameters, the engine has a fixed operating state under given flight conditions and control laws. For example, under standard ground conditions, given the engine thrust, a unique steady-state operating state can be determined. This process is an equilibrium state achieved by the engine through the constraint relationships between its various components, also known as the joint working process among the engine components. However, the parameters of each component at the engine's steady-state operating point need to be calculated using relevant constraint equations.

[0030] Under stable operating conditions, all components of an engine must meet the following constraints, i.e., common operating conditions: airflow balance; pressure balance; power balance between the turbine and compressor; and equal physical speeds of the turbine and compressor.

[0031] Under the above constraints and control laws, a system of nonlinear equations with unknown variables is formed. The number of unknown variables in the system of equations is equal to the number of equations in the system. When the engine is operating stably, this system of equations has a unique solution.

[0032] For engine thermodynamic calculation modeling, in addition to accurately calculating the thermodynamic processes of each component, it is also necessary to construct a system of equations based on the common working conditions of the engine. By giving specific values ​​to each unknown variable, the model ensures that all components of the engine meet the common working conditions. Specifically, this involves selecting reasonable parameters as independent variables, constructing error equations based on the flow rate and pressure balance, and then using a specific iterative method to gradually reduce the error until it converges to an acceptable range.

[0033] The independent variables generally include low-pressure shaft speed, high-pressure shaft speed, fan characteristic diagram auxiliary coordinate beta value, booster stage characteristic diagram auxiliary coordinate beta value, high-pressure compressor characteristic diagram auxiliary coordinate beta value, high-pressure turbine characteristic diagram auxiliary coordinate beta value, low-pressure turbine characteristic diagram auxiliary coordinate beta value, fuel consumption rate, etc.

[0034] In the initial calculation, it is necessary to estimate the initial values ​​of the unknown independent variables. Based on the estimated initial values, a set of iterative error values ​​are obtained through thermodynamic cycle calculations. Due to the use of inaccurate initial values ​​of the variables, the upstream and downstream parameters of the aero-thermodynamic cross section are inconsistent: for example, given the high-pressure compressor speed and the auxiliary coordinate beta value of the characteristic diagram, the compressor flow rate can be obtained. The compressor flow rate plus the fuel flow rate is transferred to the turbine flow rate. However, based on the turbine inlet conditions, turbine speed, and the beta value of the characteristic diagram, a turbine flow rate can be calculated. These two flow rates are not equal, and the deviation term constitutes an error equation.

[0035] Based on the above set of error equations, the convergent solution can be gradually approximated by using the Newton-Raphson iterative method and gradient algorithm.

[0036] Due to the limitations of numerical iterative methods, the accuracy of the initial guess has a significant impact on the stability of steady-state calculations: the smaller the difference between the initial guess and the actual value, the easier the calculation converges; conversely, a larger difference requires a longer iteration time and may even lead to divergence, causing the model to fail to converge. The iteration step size also affects the convergence of the iteration: a smaller iteration step size results in better convergence, but at the cost of sacrificing convergence speed.

[0037] Current methods for establishing initial guess values ​​consider the impact of flight altitude and Mach number on engine performance matching, providing several sets of initial guess parameters for different flight altitudes. This method can address some of the impact of performance matching differences among engine components at different flight altitudes / Mach numbers. However, it does not consider the influence of engine speed. That is, under the same altitude conditions, it can only refer to the characteristics at a specific speed to give specific initial guess values, failing to account for the impact of changes in initial guess values ​​at different speeds. To address these issues, manual intervention is often used, where initial guess values ​​are given based on experience outside the model to complete specific calculations. This approach relies on the experience of the program user, lacks universality, and leads to low model calculation stability, requiring further improvement.

[0038] The diversity of the objectives to be solved also places requirements on the accuracy of the initial guesses. Objectives to be solved can include thrust, relative equivalent speed of the low-pressure shaft, relative equivalent speed of the high-pressure shaft, relative physical speed of the low-pressure shaft, relative physical speed of the high-pressure shaft, physical speed of the low-pressure shaft, physical speed of the high-pressure shaft, equivalent speed of the low-pressure shaft, equivalent speed of the high-pressure shaft, combustion chamber air-fuel ratio, combustion chamber outlet total temperature, engine exhaust temperature, fuel flow rate, fan margin, booster stage margin, high-pressure compressor margin, and high-pressure compressor outlet bleed pressure, etc.

[0039] For different solution objectives, the deviation in the accuracy of the initial guess may be further amplified, leading to different results in iterative calculations. For example, when the solution objective is low-pressure speed based on a less accurate initial guess, convergence is easier; while when the solution objective is high-pressure speed, calculation divergence or non-true solutions are more likely to occur.

[0040] Therefore, for engine thermal calculation modeling, in addition to accurately calculating the thermal processes of each component, it is also necessary to construct a system of equations based on the engine's common operating conditions. By providing specific values ​​for each unknown variable, the entire engine model should satisfy the common operating conditions for all components. The accuracy of the initial guess has a significant impact on the stability of the steady-state calculation. The smaller the difference between the initial guess and the actual value, the easier it is for the calculation to converge. Conversely, a larger difference requires a longer iteration time and may even lead to divergence, causing the model to fail to converge.

[0041] Based on this, the purpose of this method is to establish a set of highly accurate initial guess models to ensure high computational stability under different solution objectives within the entire flight envelope.

[0042] The method includes the following steps: S1. Based on the simulation calculation results of the full-envelope operating condition, extract the specific performance parameter conversion table and the thermodynamic calculation independent variable parameter table; S2. Perform initial guess value calculation, including the following steps: S21. Give the target variable value; S22. Assign an initial value to the low-pressure converted speed and calculate the target variable to obtain the calculated target variable value; S23. Calculate the target variable deviation between the given target variable value and the calculated target variable value, and determine whether the target variable deviation meets the error accuracy. If it meets the accuracy requirement, calculate the initial guess value parameter based on the initial value of the low-pressure converted speed; S24. If it does not meet the accuracy requirement, correct the low-pressure converted speed to obtain the corrected low-pressure converted speed value, and repeat steps S22-S23 until a low-pressure converted speed value whose target variable deviation meets the error accuracy is obtained; S25. Based on the low-pressure converted speed value, interpolate the specific performance parameter conversion table to calculate the initial guess value parameter.

[0043] In S1, the core of the method for calculating the initial guess of the full envelope is to extract characteristics used for the initial guess model calculation based on the calculated convergent steady-state model results. These characteristics include tables of thermodynamic calculation independent variable parameters and tables of conversion relationships between specific performance parameters. The tables of thermodynamic calculation independent variable parameters are used to determine the initial guess; the tables of conversion relationships between specific performance parameters are used to establish the relationship between specific target values ​​and the converted speed of the low-pressure shaft. Specifically, step S1 includes the following specific steps.

[0044] S11. Given the flight envelope, determine the range of flight altitude ALT, flight Mach number XM, and standard ambient temperature difference TAMB, and perform reasonable discretization within the usable range;

[0045] S12. Based on the actual application scenarios of the engine, cover all thrust levels required for thrust management, determine the range of low-pressure shaft conversion speed N1R under various inlet conditions, and perform reasonable discretization within the operating range.

[0046] S13. Under various flight conditions, the low-pressure shaft equivalent speed N1R, which has good convergence, is used as the objective value for calculation to obtain the convergent steady-state model results. Since the calculation of the low-pressure shaft equivalent speed has good convergence, a relatively coarse initial guess value can be selected for calculation.

[0047] S14. Based on the calculation results of the full-envelope operating condition, extract the characteristic tables for each item. The tables can be in three-dimensional or four-dimensional form, with the independent variables being altitude, inlet Mach number, standard ambient temperature difference, and low-pressure shaft converted speed. For example, the table for the beta value of the auxiliary coordinate of the fan characteristic diagram can be represented as Table_betaFAN(ALT,XM,DTAMB,N1R) or Table_betaFAN(ALT,XM,N1R). The former represents a four-dimensional table, containing information such as flight altitude (ALT), flight Mach number (XM), standard ambient temperature difference (TAMB), and low-pressure shaft converted speed; the latter is a three-dimensional table, which can be omitted because the change in the standard ambient temperature difference has a relatively small impact on the independent variables.

[0048] Conventional data table interpolation typically requires the data table to be a square matrix for convenient data storage and management. For example, the number and value of flight Mach numbers XM corresponding to different values ​​of flight altitude (ALT) should be consistent. However, within the flight envelope, the range of usable inlet Mach numbers differs between low-altitude and high-altitude regions, making traditional data table formats unsuitable. This patent presents a novel storage method: using four one-dimensional data tables (TB_ALT, TB_XM, TB_N1R, TB_betaFAN) to represent the information of a three-dimensional data table. Elements with the same sequence number in the four data tables are grouped together to represent a parameter corresponding to a specific operating condition, such as (ALT...). i XM i N1R i ,β (FAN,i) This can be considered as being at flight altitude ALT. i and flight Mach number XM i Under the import conditions, the low-pressure equivalent speed N1R i At that time, the auxiliary coordinate beta value of the fan characteristic diagram is β. (FAN,i) The numbers are arranged in ascending order of ALT, XN, and N1R.

[0049] In some specific embodiments, the tables of independent variable parameters for thermodynamic calculation include, but are not limited to: low-pressure shaft speed, high-pressure shaft speed, fan characteristic diagram auxiliary coordinate beta value, booster stage characteristic diagram auxiliary coordinate beta value, high-pressure compressor characteristic diagram auxiliary coordinate beta value, high-pressure turbine characteristic diagram auxiliary coordinate beta value, low-pressure turbine characteristic diagram auxiliary coordinate beta value, fuel consumption rate, etc.

[0050] Tables showing the conversion relationships between specific performance parameters include, but are not limited to: a table showing the conversion of the high-pressure shaft speed N2R; a table showing the conversion between the total inlet temperature T25 of the high-pressure compressor and the total inlet temperature T1 of the engine; and a table showing the conversion between the static pressure PS3 of the high-pressure compressor outlet and the total inlet pressure P1 of the engine.

[0051] After obtaining the tables of independent variable parameters for thermodynamic calculations and the tables of mutual conversion relationships between specific performance parameters, the calculated value of the target variable V under the current low-pressure equivalent rotational speed N1R is calculated using interpolation and calculation methods based on these tables. cal And based on the given target variable value V Target Calculate the deviation value of the target variable.

[0052] In step S21, obtaining the value of the given target variable based on the numerical table includes the following steps:

[0053] S211. During the calculation, the incoming flow parameters need to be configured first. For the given inlet conditions, the incoming flow parameters are calculated, including but not limited to: altitude ALT, standard temperature difference DTAMB, flight Mach number XM, inlet total temperature P1, inlet total pressure T1, flight speed V1, etc.

[0054] S212. When solving, different calculation methods are given for different solution objectives to obtain the calculated value of the objective variable. For details, please refer to the calculation objectives and calculation methods in S2121-2129 below.

[0055] S2121. When solving for the target variable, which is the converted speed of the low-pressure shaft, the formula for calculating the target variable is V. cal =N1R.

[0056] S2122. When the objective is the physical speed of the low-pressure shaft, the formula for calculating the objective variable is: Where T std T1 is the temperature under standard ground conditions, i.e., 288.15K, and T2 is the total temperature at the engine inlet.

[0057] S2123. When solving for the target variable V, which is the converted speed of the high-pressure shaft, the target variable is calculated as follows: cal The calculation steps are as follows: Based on the table Table_N2R(ALT,XM,N1R) corresponding to the converted high-pressure shaft speed N2R, interpolate to obtain N2R; V cal =N2R.

[0058] The steps for interpolating based on the numerical table will be introduced later.

[0059] S2124. When solving for the target value V, which is the physical speed of the high-pressure shaft, the target variable is calculated. cal The calculation steps are as follows: Based on the table of correspondences between the high-pressure compressor inlet total temperature T25 and the engine inlet total temperature T1 (Table_T25qT1(ALT,XM,N1R), interpolate to obtain T25qT1; calculate the high-pressure compressor inlet total temperature T25 = T25qT1 × T1; based on the table of correspondences between the high-pressure shaft converted speed N2R (Table_N2R(ALT,XM,N1R), interpolate to obtain N2R; the formula for calculating the target variable is... T std The temperature is the ground standard temperature, which is 288.15K.

[0060] S2125. When solving for the objective variable V, where the objective is the static pressure PS3 at the outlet of the high-pressure compressor. cal The calculation steps are as follows: Based on the table Table_PS3qP1(ALT,XM,N1R) showing the correspondence between the high-pressure compressor outlet static pressure PS3 and the engine inlet total pressure P1, interpolate to obtain PS3qP1; calculate the high-pressure compressor outlet static pressure PS3 = PS3qP1 × P1; calculate the target variable V. cal It is PA3.

[0061] S2126. When the objective is the total outlet temperature T3 of the high-pressure compressor, calculate the target variable V. cal The calculation steps are as follows: Based on the table Table_T3qT1(ALT,XM,N1R) showing the correspondence between the high-pressure compressor outlet total temperature T3 and the engine inlet total temperature T1, interpolate to obtain T3qT1; calculate the high-pressure compressor outlet total temperature T3 = T3qT1 × T1; calculate the target variable V. cal It equals T3.

[0062] S2127. When the objective is the total inlet temperature T4 of the first-stage guide vane of the high-pressure turbine, calculate the target variable V. cal The calculation steps are as follows: Based on the correspondence table Table_T41qT1(ALT,XM,N1R) between the total outlet temperature T41 of the high-pressure turbine first-stage guide vane and the total inlet temperature T1 of the engine, interpolate to obtain T41qT1; calculate the total outlet temperature T4 of the high-pressure turbine first-stage guide vane = T4qT1 × T1; the correspondence between the total inlet temperature T4 of the high-pressure turbine first-stage guide vane and the total outlet temperature T41 of the high-pressure turbine first-stage guide vane can be approximately considered as a linear relationship, i.e., T4 = T41 × K3, where K3 is a constant coefficient with a value range of 1.05-1.08; calculate the target variable V. cal It equals T4.

[0063] S2128. When solving for the objective variable V, which is the engine exhaust temperature EGT, the calculated value of the objective variable is... cal The calculation steps are as follows: Based on the correspondence table Table_T49qT1(ALT,XM,N1R) between the low-pressure turbine first-stage guide vane outlet total temperature T49 and the engine inlet total temperature T1, interpolate to obtain T49qT1; calculate the low-pressure turbine first-stage guide vane outlet total temperature T49 = T49qT1 × T1; the correspondence between the engine exhaust temperature EGT and the low-pressure turbine first-stage guide vane outlet total temperature T49 can be approximately considered a linear relationship, i.e., EGT = T49 × K4, where K4 is a constant coefficient, generally taken as 1.01-1.03; calculate the target variable V. cal It equals EGT.

[0064] S2129. When solving for the objective variable V as fuel flow rate WFE. cal The calculation steps are as follows: Based on the table Table_W036R(ALT,XM,N1R) corresponding to the converted flow rate W036R at the combustion chamber flame tube inlet (corresponding to the converted flow rate at the engine inlet section), interpolate to obtain W036R; calculate the physical flow rate at the combustion chamber flame tube inlet. Where T std The temperature under standard ground conditions is 288.15 K, P std The pressure is 101.325 kPa under standard ground conditions; FAR36 is obtained by interpolation based on the corresponding table Table_FAR36(ALT,XM,N1R) for the air-fuel ratio at the combustion chamber inlet; the fuel flow rate WFE is calculated as W036 × FAR36; the target variable V is calculated. cal It equals WFE.

[0065] S2120. When solving for the target force FN, the calculated value of the target variable V is... cal The calculation steps are as follows: Based on the corresponding table Table_FGR(ALT,XM,N1R) for the converted total thrust of the engine, interpolate to obtain FGR; calculate the total thrust of the engine. P std The pressure is 101.325 kPa under standard ground conditions. Based on the table W1R(ALT,XM,N1R) corresponding to the converted flow rate W1R at the engine inlet, W1R is obtained by interpolation. The physical flow rate at the engine inlet is then calculated. Where T std The temperature under standard ground conditions is 288.15 K, P std The pressure under standard ground conditions is 101.325 kPa; calculate the net engine thrust FN = FG - W1 × V1; calculate the target variable V. cal It equals FN.

[0066] The above interpolation method will be introduced below.

[0067] Taking the three-dimensional interpolation table Table_betaFAN(ALT,XM,N1R) as an example, combined with Table 1 and... Figure 3 Understand the implementation principle of multidimensional interpolation calculation methods.

[0068] (1) First, retrieve the position of the target flight altitude ALT in TB_ALT, select the two closest altitude values ​​(such as the altitude value LALT on the left and the altitude value RALT on the right), that is, LALT≤ALT≤RALT, and there are no other altitude values ​​between LALT and RALT in the TB_ALT table; record the leftmost parameter positions N_(LALT,1) and N_(RALT,1) of the above two altitudes;

[0069] (2) Based on the position N_(LALT,1), retrieve the position of the target inlet Mach number XM under the same LALT in TB_XM, select the two closest inlet Mach values ​​(LXM1 and RXM1), that is, LXM1≤XM≤RXM1, and the TB_XM table is within the interval of the corresponding same LALT, and there are no other Mach values ​​between LXM1 and RXM2; record the leftmost parameter positions N_LXM1,1 and N_RXM1,1 of the above two Mach numbers;

[0070] (3) Based on the position N_LXM1,1, retrieve the position of the target low-pressure equivalent speed N1R under the same LALT & same LXM1 in the TB_N1R table, select the two closest low-pressure equivalent speed values ​​LN1R11 and RN1R11, that is, LN1R11≤XM≤RN1R11, and there are no other Mach values ​​between LN1R11 and RN1R11 in the TB_N1R table within the interval corresponding to the same LALT & same LXM1; record the positions N_LN1R11 and N_RN1R11 of the above two speeds;

[0071] (4) Similarly, the positions of the other 6 parameters can be given. The information of the 8 points after retrieval is shown in Table 1:

[0072] Under the same LALT & the same RXM1, select the two low-pressure converted speed values ​​that are closest to the target N1R and record the positions N_LN1R12 and N_RN1R12;

[0073] Under the same RALT & the same LXM2, select the two low-pressure converted speed values ​​that are closest to the target N1R and record the positions N_LN1R21 and N_RN1R21;

[0074] Under the same RALT & the same RXM2, select the two low-pressure converted speed values ​​that are closest to the target N1R and record the positions N_LN1R22 and N_RN1R22;

[0075] (5) Based on the eight positions obtained above, interpolate the target β_FAN:

[0076] a) Based on the position information of N_LN1R11 and N_RN1R11, find the corresponding position parameters XX1 and XX2 of the TB_betaFAN table, eliminate the N1R dimension, and calculate using the following formula:

[0077] Similarly, the values ​​of XY2, XY3, and XY4 can be calculated.

[0078] b) Eliminate the Mach number dimension at the input, and calculate the result after elimination based on the values ​​of XY1 and XY2. Similarly, the value of XZ2 can be calculated.

[0079] c) Eliminate the flight altitude dimension, calculate the target value, and refer to the calculation method described above.

[0080] Complete the interpolation calculation.

[0081] Table 1 shows the operating condition information of the eight points after the retrieval.

[0082]

[0083] It is understandable that the above formula applies not only to... Figure 3 The first pair of data in the table also applies to any pair of adjacent parameters.

[0084] After completing step S21 and providing the target variable value, calculate the initial guess value.

[0085] The core of this method for calculating the initial guess of the full envelope is based on the calculated convergent steady-state model results. It extracts characteristics used for the initial guess model calculation, including tables of thermodynamic calculation independent variable parameters and tables of conversion relationships between specific performance parameters. The corresponding N1R is calculated, and then, based on the thermodynamic calculation independent variable tables, the initial guess is calculated for subsequent iterative calculations.

[0086] The following is a specific embodiment and Figure 2 The following section provides a detailed introduction to S21-S25.

[0087] (1) The initial step of calculating the initial guess value is to give the initial value of the low-pressure converted speed N1R0 and assign it to the independent variable of the low-pressure converted speed N1R in the iteration process, N1R = N1R0.

[0088] (2) Perform calculations based on the given target variable and its value V. Target Calculate the target variable V under a specific low-pressure equivalent speed N1R. calCalculate the target variable deviation value delTarget=(V cal -V Target ) / V Target Assign the low-pressure converted speed value N1R to DUMX1, and assign the target variable value V... cal Assign the value to DUMY1 for subsequent calculations.

[0089] (3) Determine whether the target variable deviation value delTarget meets the error accuracy requirement k0. k0 can be given as needed, generally 0.1%-0.5%. If the absolute value of the deviation is less than the error accuracy requirement k0, skip to step (13). If the absolute value of the deviation is greater than or equal to the error accuracy requirement k0, skip to step (4).

[0090] (4) The low-pressure converted speed value N1R is superimposed with the deviation amount of k1%N1R0. That is, based on the N1R value, a smaller deviation amount is given to determine the direction of change of N1R. N1R = N1R + k1%N1R0. In one embodiment, k1% is in the range of 1% to 3%, preferably 1%, to find the direction of change of N1R.

[0091] (5) Perform calculations based on the given target variable and its value V. Target Calculate the target variable V under a specific low-pressure equivalent speed N1R. cal , calculate the target variable deviation value delTarget=(V cal -V Target ) / V Target Assign the low-pressure converted speed value N1R to DUMX2, and assign the target variable value V. cal Assign the value to DUMY2;

[0092] (6) Determine whether the target variable deviation value delTarget meets the error accuracy requirement k0; if the absolute value of the deviation is less than the error accuracy requirement k0, or N1R has exceeded the limit, jump to step (13); if the absolute value of the deviation is greater than or equal to the error accuracy requirement k0, jump to step (7).

[0093] (7) Based on the calculation results of step (6), and based on the gradient method principle, calculate the adjustment amount delN1R of the low-pressure converted speed value N1R, i.e.

[0094] And update DUMX1 = DUMX2 (do not update in the first iteration), and update DUMY1 = DUMY2 (do not update in the first iteration);

[0095] (8) Determine whether the absolute value of the adjustment amount delN1R of the low-pressure converted speed value N1R is greater than the deviation threshold k2%N1R0. In some embodiments, the deviation threshold is 5% to 10% of the low-pressure converted speed value. If it is greater than the threshold, skip to step (9). If it is less than or equal to the threshold, skip to step (10).

[0096] (9) Update the low-pressure converted speed value N1R according to k2%N1R0, with the same sign as delN1R, i.e. N1R=N1R+ABS(delN1R) / delN1R×k2%N1R0, and jump to step (11) to continue the iteration;

[0097] (10) Update the low-pressure converted speed value N1R by delN1R, i.e. N1R = N1R + delN1R, and jump to step (11) to continue the iteration;

[0098] (11) Determine whether the updated N1R exceeds the initial guess value to calculate the limit value, where the limit value can be determined according to the flight altitude and flight Mach number, N1RMAX is the upper limit value, and N1RMIN is the lower limit value; if it exceeds the limit, skip to step (12), if it does not exceed the limit, skip to step (5);

[0099] (12) After the updated N1R exceeds the limit, update N1R to the limit value and jump to step (5);

[0100] (13) Based on the low-pressure converted speed value N1R, interpolate the relevant data tables to calculate the initial guess parameters. Combined with the data tables of mutual conversion relationships of specific performance parameters, the necessary inputs can be provided for the component characteristics of the engine steady-state performance model, such as some parameters of the inlet and outlet sections of each component, such as total temperature, total pressure, and flow parameters.

[0101] The above method establishes a calculation method for generating the initial guess value characteristics of the full envelope, generating a model input suitable for calculating the initial guess value of the full envelope. The characteristics consist of a family of numerical tables, including numerical tables for independent variable parameters and numerical tables for the conversion relationships between specific performance parameters. The numerical tables for independent variable parameters are used to determine the initial guess value, and the numerical tables for the conversion relationships between specific performance parameters are used to establish the relationship between specific target values ​​and the low-pressure shaft equivalent speed. A full envelope initial guess value model is established, and for various calculation target values, the conversion relationship between the low-pressure equivalent speed N1R and the target variable is established, giving the low-pressure equivalent speed N1R value under the corresponding characteristic target value. Based on the N1R value and the corresponding incoming flow parameter interpolation, a relatively accurate initial guess value is generated, so that the steady-state model, within the full envelope range, reduces the iteration time and has good steady-state model calculation stability for various solution objectives.

[0102] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any variations and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for calculating the initial guess value model in steady-state simulation of overall engine performance, characterized in that, Includes the following steps: S1. Based on the simulation results of the full-envelope working condition, extract the conversion table of specific performance parameters and the table of independent variable parameters for thermodynamic calculation; S2. Perform the initial guess calculation, including the following steps: S21. Given the value of the target variable; S22. Assign initial values ​​to the low-pressure conversion speed and calculate the target variable to obtain the calculated target variable value; S23. Calculate the target variable deviation between the given target variable value and the calculated target variable value, and determine whether the target variable deviation meets the error accuracy. If it meets the accuracy requirements, calculate the initial guess parameter based on the initial value of the low-pressure converted speed. S24. If the accuracy requirements are not met, correct the low-pressure converted speed to obtain the corrected low-pressure converted speed value, and repeat steps S22-S23 until the low-pressure converted speed value that meets the error accuracy of the target variable deviation is obtained. S25. Based on the low-pressure converted speed value, interpolate the specific performance parameter conversion table to calculate the initial guess parameter.

2. The calculation method as described in claim 1, characterized in that, In step S24, the method for correcting the low-pressure converted speed is as follows: S241. Add 1% to 3% to the existing low-pressure converted speed to obtain the first corrected low-pressure converted speed; S242. Repeat steps S22-S23 to determine whether the target variable deviation meets the error accuracy. If the accuracy requirement is met, calculate the initial guess parameter based on the initial value of the low-pressure converted speed. If the accuracy requirement is not met, continue to correct the low-pressure converted speed.

3. The calculation method as described in claim 1, characterized in that, In step S24, it is also necessary to determine whether the value of the low-pressure converted speed exceeds the limit. The determination method includes the following steps: Calculate the adjustment amount for the low-pressure converted speed value; Determine whether the absolute value of the adjustment amount is greater than the deviation threshold, wherein the deviation threshold is 5% to 10% of the low-pressure converted speed value. When the adjustment amount is greater than the deviation threshold, the low-pressure converted speed value is superimposed on the deviation threshold. When the adjustment amount is less than the deviation threshold, the low-pressure converted speed value is superimposed on the adjustment amount. Determine whether the superimposed and updated low-pressure converted speed value exceeds the initial guess calculation limit. If it exceeds the initial guess calculation limit, correct the low-pressure converted speed value to the initial guess calculation limit and use the corrected value to perform the calculation in step S242. If it does not exceed the initial guess calculation limit, use the updated low-pressure converted speed value to perform the calculation in step S242.

4. The calculation method as described in claim 1, characterized in that, In step S22, the steps for determining the value of the target variable are as follows: Given the inlet conditions, the incoming flow parameters are calculated; depending on the different solution objectives, different solution steps are used to obtain the calculated values ​​of the target variables.

5. The calculation method as described in claim 1, characterized in that, The data table can be a three-dimensional or four-dimensional data table.

6. The calculation method as described in claim 5, characterized in that, The steps for interpolating values ​​in a table are as follows: The number table is a three-dimensional number table, which includes a first parameter, a second parameter, and a third parameter, arranged in ascending order; Retrieve the position of the known first parameter in the three-dimensional table, and select the two first parameter values ​​that are closest to the known first parameter; Based on the two first parameter values, the corresponding second parameter values ​​under the same first parameter value are retrieved respectively, and the positions of the two second parameter values ​​that are closest to the corresponding second parameter value are selected in the three-dimensional table. Based on the two second parameter values, the corresponding third parameter values ​​under the same second parameter value are retrieved respectively, and the positions of the two third parameter values ​​that are closest to the corresponding third parameter value are selected in the three-dimensional table. Based on the eight third parameter values, find the corresponding target parameter at the corresponding position in the table, and interpolate to obtain the target variable value. The interpolation steps are as follows: Eliminate the third parameter dimension based on the two third parameter values; Eliminate the second parameter dimension based on the two second parameter values; Eliminate the first parameter dimension based on the two first parameter values; Obtain the target interpolation.

7. The calculation method as described in claim 6, characterized in that, use The elimination of the third parameter dimension is defined as follows: RN1R11 and LN1R11 are two adjacent third parameter values ​​obtained based on the same corresponding third parameter value, XX1 and XX2 are the corresponding target parameters of RN1R11 and LN1R11 at the corresponding positions in the table, and XY1 is the value of the corresponding position parameter after eliminating the third parameter dimension.

8. The calculation method as described in claim 7, characterized in that, use Eliminate the second parameter dimension, where RXM1 and LXM1 are two adjacent second parameter values ​​obtained based on the same corresponding second parameter value, XY2 and XY1 are the corresponding target parameters of RXM1 and LXM1 at the corresponding positions in the table, and XZ1 is the value of the corresponding position parameter after eliminating the second parameter dimension.

9. The calculation method as described in claim 8, characterized in that, use Elimination is performed using the first parameter dimension, where RALT and LALT are two adjacent first parameter values ​​obtained from the same corresponding first parameter value, XZ2 and XZ1 are the corresponding target parameters of RALT and LALT at their respective positions in the table, and β FAN That is the target value.

10. The calculation method as described in claim 6, characterized in that, The first parameter is the flight altitude, the second parameter is the Mach number, and the third parameter is the low-pressure equivalent rotational speed.

Images