Axial flow compressor performance prediction method adopting back pressure boundary condition

Abstract

The invention relates to a method for predicting the performance of an axial flow compressor by adopting a backpressure boundary condition, which comprises the following steps of: replacing flow with static pressure at an outlet of the axial flow compressor to serve as an input parameter of a low-dimensional analysis program, further analyzing the performance level of the axial flow compressor, and optimizing the performance of the axial flow compressor by utilizing a means of combining a least square method and a variable optimization formula. A calculation mode of the back pressure boundary condition of the low-dimensional analysis program of the axial flow compressor is applied, and meanwhile, the calculation content and process of the low-dimensional analysis program of the axial flow compressor in the calculation mode of the back pressure boundary condition are planned; therefore, the low-dimensional analysis program of the axial flow compressor has the capability of predicting the blocking state performance of the axial flow compressor, and the performance prediction integrity and reliability of the axial flow compressor in a one-dimensional design stage and a two-dimensional design stage in an axial flow compressor design system are also enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of fluid machinery design, and particularly to a method for predicting the performance of an axial compressor. Background Art

[0002] With the development of the times, the progress of technology, and the continuous improvement of the industrial level. At the same time, the technical level and design indicators of aeroengines and gas turbines are also getting higher and higher. As a core component among them, the design ability and related level of the axial compressor are directly related to the performance levels of the "two engines", namely aeroengines and gas turbines. There are two operating conditions during the operation of the axial compressor, namely the design condition and the off-design condition. And in the actual working state of the axial compressor, most of the conditions are off-design conditions. There are two relatively "dangerous states" in the off-design conditions, namely the stall state and the choke state. The present invention mainly discusses the choke state under off-design conditions in the axial compressor.

[0003] Earlier axial compressor designers believed that the axial compressor being in the choke state is extremely unfavorable to the performance of the axial compressor, and its relatively high Mach number and the losses brought by shock waves are relatively severe. Generally, design means are used to avoid the axial compressor operating in the choke state. With continuous in-depth research, researchers have found that not all choke states are unacceptable.

[0004] Taking the flow angle-loss characteristic curve of a certain supersonic inlet cascade as an example, at a certain inlet Mach number (greater than 1), as the angle of attack continuously decreases, its total pressure loss coefficient continuously decreases; until the angle of attack decreases to a certain angle, the angle of attack no longer decreases, and there is a normal shock wave in the axial compressor cascade passage. At this time, the cascade passage is in the choke state of supersonic inlet flow, also known as the starting state. In this state, the angle of attack of the inlet flow no longer changes, which means that the flow angle and flow rate of the inlet flow in the axial compressor cascade will be fixed. At this time, the loss coefficient of the cascade is related to the static pressure at the outlet of the cascade (the static pressure at the outlet is the back pressure). The smaller the static pressure at the outlet, the larger the loss coefficient, and the lower the compressor pressure ratio. It corresponds to the "vertical section" in the flow rate-pressure ratio characteristic diagram of the axial compressor. However, in the choke state of the supersonic cascade, within a certain range of outlet static pressure, the loss coefficient of the cascade can be controlled within an acceptable range for design and application. In addition, there is also an engineering need for the axial compressor in a gas turbine to operate in the choke condition.

[0005] Meanwhile, at present, the performance prediction and analysis of axial flow compressors under the blocked state mainly rely on full three-dimensional numerical simulation calculations, which are extremely time-consuming and costly prediction methods. Since the design of axial flow compressors requires continuous iteration of design schemes during the design process, it is impossible to rely on full three-dimensional numerical simulation methods for the design and analysis of axial flow compressors. In the existing axial flow compressor aerodynamic design system, the main tools used are one-dimensional design and analysis programs and two-dimensional design and analysis programs. Among them, the design programs are used for scheme design and geometry generation, and the analysis programs are used for the rapid inspection of the performance indicators of the design scheme.

[0006] However, at present, a low-dimensional (one-dimensional or two-dimensional) analysis program that can predict the performance of compressors under the blocked state has not been published. The main reasons are as follows: First, since the flow rate does not change under the blocked state of the compressor, there are multiple performance points corresponding to the blocked state of the compressor at this flow rate. Therefore, a single flow rate input cannot accurately predict the performance of the axial flow compressor at this flow rate. Second, under the blocked state of the axial flow compressor, its performance is jointly determined by the flow rate and the outlet static pressure at this operating point. Moreover, the calculation of the key parameters "loss coefficient" and "lag angle" in the performance calculation requires a semi-empirical model with the flow rate and the outlet static pressure as inputs, and this model has not been published yet due to the lack of a supporting one-dimensional or two-dimensional analysis program for axial flow compressors.

[0007] In summary, during the design process of axial flow compressors, the prediction and analysis of their performance under the blocked state are crucial. Therefore, there is an urgent need to provide a method that can predict the performance of axial flow compressors. Summary of the Invention

[0008] The purpose of the present invention is to avoid the deficiencies of the prior art and provide a calculation mode that applies the backpressure boundary conditions of the low-dimensional analysis program of the axial flow compressor through optimization means, enabling it to have the basic conditions for predicting the performance of the axial flow compressor under the blocked state. At the same time, the calculation content and process of the low-dimensional analysis program of the axial flow compressor under the backpressure boundary condition calculation mode are planned to solve the problem that in the existing axial flow compressor design system, the low-dimensional analysis program uses the flow rate as the boundary condition and cannot predict the performance under the blocked state of the axial flow compressor. A method for predicting the performance of an axial flow compressor using backpressure boundary conditions.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for predicting the performance of an axial flow compressor using backpressure boundary conditions, comprising the following steps: Step 1: Given the boundary conditions of an axial flow compressor elementary stage during the performance analysis of the axial flow compressor, the boundary conditions include: the absolute airflow angle at the inlet calculation station of the rotor blade , the total temperature , the total pressure , the pressure ratio ; the static pressure at the outlet calculation station of the stator blade , the rotational speed of the axial flow compressor and the geometric parameters of the elementary stage of the axial flow compressor; Step 2: Based on the pressure ratio at the calculation station at the inlet of the rotor blade Determine the static pressure at the calculation station at the inlet of the rotor blade , combined with the static pressure at the calculation station at the outlet of the stator blade , thereby initializing and allocating the static pressure at the calculation station at the outlet of the rotor blade as: , Step 3: Based on the performance analysis and calculation model of the axial flow compressor and the number of elementary stages of the axial flow compressor, in the gas flow direction of the axial flow compressor, calculate the performance parameters of the calculation stations at the inlet of the rotor blade, at the outlet of the rotor blade, at the inlet of the stator blade, and at the outlet of the stator blade of the axial flow compressor for each elementary stage. The calculation process for each elementary stage of the axial flow compressor is as follows: First, according to the boundary conditions, solve for the flow rate at the calculation station at the inlet of the rotor blade of the elementary stage of the axial flow compressor ; according to the static pressure at the calculation station at the outlet of the rotor blade , solve for the flow rate at the calculation station at the outlet of the rotor blade ; Next, according to the flow rate at the calculation station at the outlet of the rotor blade , solve for the performance parameters of the calculation station at the inlet of the stator blade Among them, the performance parameters include the total temperature , total pressure , absolute circumferential velocity , axial velocity , absolute velocity , static temperature , static pressure ; Finally, according to the performance parameters of the calculation station at the inlet of the stator blade and the static pressure at the calculation station at the outlet of the stator blade , calculate the flow rate at the calculation station at the outlet of the stator blade , that is, complete the calculation of the performance parameters of the elementary stage of the axial flow compressor; After the performance parameters of each elementary stage are calculated, determine whether the current elementary stage is the last elementary stage of the axial flow compressor, that is, obtain the flow rate at the calculation station at the outlet of the rotor blade and the flow rate at the calculation station at the outlet of the stator blade in each elementary stage of the axial flow compressor; Step 4: Based on the least squares method, through the flow rate at the calculation station at the inlet of the rotor blade , the flow rate at the calculation station at the outlet of the rotor blade , and the flow rate at the calculation station at the outlet of the stator blade , establish an objective function for measuring the flow rate difference of the elementary stage of the axial flow compressor; Step 5: Based on the objective function, with the static pressure at the calculation station at the inlet of the rotor blade , the static pressure at the calculation station at the outlet of the rotor blade To optimize the variables, according to the law of conservation of flow, the variable optimization formula is used to continuously update the optimized variables until the value of the objective function is less than 10 -8 , that is, the updated performance parameters of the axial flow compressor are obtained.

[0010] Furthermore, in step three, the flow rate at the inlet calculation station of the rotor blade is equal to the flow rate at the outlet calculation station of the inlet guide vane of the axial flow compressor.

[0011] Furthermore, in step three, in the calculation of each elementary stage, the absolute flow angle, total temperature, and total pressure at the inlet calculation station of the rotor blade of the next elementary stage of the axial flow compressor are the same as those at the outlet calculation station of the stator blade of the previous elementary stage of the axial flow compressor.

[0012] Furthermore, the flow rate at the inlet calculation station of the rotor blade described in step three The solution process is as follows: First, according to the total temperature , total pressure , and static pressure at the inlet calculation station of the rotor blade, the static temperature at the inlet calculation station of the rotor blade is determined to be: , wherein, is equal to 1.4, which is the specific heat ratio constant; Next, according to the isentropic relationship, the absolute velocity at the inlet calculation station of the rotor blade is determined to be: , wherein, is equal to 1004.0, which is the specific heat at constant pressure; Furthermore, in sequence, according to the absolute flow angle at the inlet calculation station of the rotor blade, and the axial velocity at the inlet calculation station of the rotor blade determined according to the velocity triangle relationship; according to the rotational speed of the axial flow compressor and the median radius at the inlet calculation station of the rotor blade, the circumferential velocity , absolute circumferential velocity , relative circumferential velocity and relative velocity at the inlet calculation station of the rotor blade are determined. The specific formulas include: , , , , , Continuously, according to the thermodynamic relationship, determine the relative total temperature at the inlet calculation station of the moving blade and the relative total pressure . The specific formula is: , , Then, based on the geometric parameters of the known elementary stage of the axial compressor and the static pressure and static temperature at the inlet calculation station of the moving blade, determine the gas density and the flow rate at the inlet calculation station of the moving blade. The specific formula is: , , In the formula, is equal to 287.03, which is the gas state constant. At this time, the flow rate at the inlet calculation station of the moving blade is output.

[0013] Furthermore, the calculation process of the flow rate at the outlet calculation station of the moving blade in step three is as follows: According to the conservation relationship of enthalpy transfer, based on the static pressure , circumferential velocity at the outlet calculation station of the moving blade and the relative total temperature , circumferential velocity at the inlet calculation station of the moving blade, then the relative total temperature at the outlet calculation station of the moving blade is determined as: , In the formula, is equal to 1004.0, which is the specific heat capacity at constant pressure; Based on the moving blade loss coefficient : , Thus, according to the isentropic relationship, determine the ideal relative total pressure at the outlet calculation station of the moving blade as: , In the formula, is equal to 1.4, which is the specific heat ratio constant; Since the moving blade loss coefficient is calculated by the loss model in the axial compressor performance analysis and calculation model, then determine the relative total pressure at the outlet calculation station of the moving blade as: , Furthermore, based on the static pressure of the calculated station at the outlet of the moving blade that has been allocated , and the relative total temperature and relative total pressure of the calculated station at the outlet of the moving blade, according to the isentropic relationship, determine the static temperature of the calculated station at the outlet of the moving blade as: , Then, based on the relationship between the relative total temperature and the static temperature of the calculated station at the outlet of the moving blade, determine the relative velocity of the calculated station at the outlet of the moving blade as: , Continuing, according to the velocity triangle relationship, determine the circumferential velocity , relative circumferential velocity , absolute circumferential velocity and absolute velocity of the calculated station at the outlet of the moving blade. The specific formulas are: , , , , In the formula, is the relative flow angle of the calculated station at the outlet of the moving blade, which is calculated by the trailing angle model in the axial compressor performance analysis and calculation model; Furthermore, based on the concept of stagnation state, given the absolute velocity and static temperature of the calculated station at the outlet of the moving blade, determine the total temperature of the calculated station at the outlet of the moving blade as: , According to the isentropic relationship, and the static temperature , total temperature , static pressure of the calculated station at the outlet of the moving blade, determine the total pressure of the calculated station at the outlet of the moving blade as: , The gas flow density and flow rate of the calculated station at the outlet of the moving blade are: , , At this time, the flow rate of the calculated station at the outlet of the moving blade is obtained.

[0014] Furthermore, the flow rate of the stationary blade outlet calculation station in step 3 is The specific calculation process is: Calculate the static pressure of the station according to the stator outlet , total pressure of the stationary blade inlet calculation station The operating characteristics of the static stator blades in the elementary stage of the axial compressor are that the airflow in the stator blades belongs to absolute energy non-isentropic flow, so the total temperature of the stator blade outlet calculation station is determined. Equal to the total temperature of the stationary blade inlet calculation station ; Next, determine the total pressure at the stationary blade outlet calculation station. for: , Where, is the stator blade loss coefficient, which is calculated by the loss model in the axial compressor performance analysis and calculation model; Then, the static pressure at the station is calculated based on the stator outlet , total temperature , total pressure , determine the static temperature of the stationary blade outlet calculation station for: , Next, continue to calculate the total temperature of the station at the known stator outlet based on the isentropic relationship. and Jingwen , and the absolute airflow angle at the stator blade outlet calculation station determined by the lagging angle model in the axial flow compressor performance analysis calculation model , determine the absolute speed of the stationary blade exit calculation station , axial speed The size is: , , Where, is equal to 1004.0, which is the specific heat capacity at constant pressure; At the same time, determine the airflow density at the stationary blade outlet calculation station and traffic , specifically: , , Where, Equal to 287.03, which is the gas state constant; At this time, the flow rate of the stationary blade outlet calculation station is obtained .

[0015] Furthermore, the objective function established in step 4 is for: , wherein, , , are the flow rates at the inlet calculation station of the moving blade, the flow rate at the outlet calculation station of the moving blade, and the flow rate at the outlet calculation station of the stationary blade, .

[0016] Furthermore, the variable optimization formula in step five is: , wherein, is the updated input variable, is the input variable before update, is the learning rate, representing the magnitude of parameter adjustment in the optimization process, is the output variable corresponding to when is the input variable; includes , , , and , , are the flow rates at the inlet calculation station of the moving blade, the flow rate at the outlet calculation station of the moving blade, and the flow rate at the outlet calculation station of the stationary blade, .

[0017] The beneficial effects of the present invention are as follows: The present invention provides an axial flow compressor performance prediction method using backpressure boundary conditions, which proposes a method and calculation process for applying backpressure boundary conditions by means of optimization. By using the optimization means to apply the calculation mode of the backpressure boundary conditions to the low-dimensional analysis program of the axial flow compressor, and at the same time planning the calculation content and process of the low-dimensional analysis program of the axial flow compressor under the backpressure boundary condition calculation mode; enabling the low-dimensional analysis program of the axial flow compressor to have the ability to predict the performance of the axial flow compressor in the blocked state; also enhancing the integrity and reliability of the performance prediction of the axial flow compressor in the one-dimensional design stage and the two-dimensional design stage in the axial flow compressor design system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the flow chart of the present invention; Figure 2 is the schematic diagram of the elementary stage structure of the axial flow compressor described in the present invention; Figure 3 is the schematic diagram of the three-stage axial flow compressor PW3S1 in the specific example 1 of the present invention; Figure 4It is a schematic diagram of the velocity triangle principle in Specific Example 1 of the present invention; Figure 5 It is the total pressure and static pressure distribution diagrams of each calculation station obtained by using the flow boundary condition in Specific Example 1 of the present invention; Figure 6 It is the axial velocity distribution diagram of each calculation station obtained by using the flow boundary condition in Specific Example 1 of the present invention; Figure 7 It is a comparison diagram of the total pressure and static pressure distributions of each calculation station calculated by using the flow boundary condition and the back pressure boundary condition respectively for the three-stage axial flow compressor PW3S1 in Specific Example 1 of the present invention; Figure 8 It is a comparison diagram of the axial velocity distributions of each calculation station calculated by using the flow boundary condition and the back pressure boundary condition respectively for the three-stage axial flow compressor PW3S1 in Specific Example 1 of the present invention; Figure 9 It is the convergence history diagram of the calculation process in Specific Example 1 of the present invention; Figure 10 It is a schematic diagram of the Laval nozzle structure principle in Specific Example 2 of the present invention; Figure 11 It is the outlet static pressure - flow rate characteristic diagram obtained in Specific Example 2 of the present invention; Figure 12 It is a comparison diagram of the calculation result and the analytical solution by using the back pressure boundary condition under the blocked state of the Laval nozzle in Specific Example 2 of the present invention; Figure 13 It is the convergence history diagram of the calculation process in Specific Example 2 of the present invention. Specific Embodiment

[0019] The principles and features of the present invention will be described below in conjunction with the figures. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0020] Example 1: As Figure 1 shown, a method for predicting the performance of an axial flow compressor using a back pressure boundary condition according to the present invention includes the following steps: S01. Given a boundary condition for an axial flow compressor elementary stage in the performance analysis of an axial flow compressor, the boundary condition includes: the absolute flow angle [[ID=4i]]、total temperature 、total pressure 、pressure ratio at the inlet calculation station of the rotor blade; the static pressure at the outlet calculation station of the stator blade, the rotational speed of the axial flow compressor, and the geometric parameters of the axial flow compressor elementary stage; S02. Determine the static pressure at the inlet calculation station of the rotor blade according to the pressure ratio , combined with the static pressure of the stationary blade outlet calculation station , thereby initializing the static pressure distribution of the blade outlet calculation station for: ; S03. Calculate the performance parameters of the first axial flow compressor elementary stage rotor blade inlet, rotor blade outlet calculation station, stator blade inlet, and stator blade outlet calculation station: Calculate the total temperature of the station based on the blade inlet , total pressure , static pressure , determine the static temperature of the blade inlet calculation station for: , Where, is equal to 1.4, which is the specific heat constant; Then, according to the isentropic relationship, the absolute speed of the rotor blade inlet calculation station is determined for: , Where, is equal to 1004.0, which is the specific heat capacity at constant pressure; Then, according to the absolute airflow angle of the rotor blade inlet, , and the axial velocity of the rotor blade inlet calculation station determined according to the velocity triangle relationship ; According to the speed of the axial compressor and the centerline radius of the rotor blade inlet calculation station , determine the circumferential velocity of the rotor blade inlet calculation station , absolute circumferential speed , relative circumferential speed and relative speed , the specific formulas include: , , , , , S04. According to the thermodynamic relationship, determine the relative total temperature of the blade inlet calculation station. , relative total pressure , the specific formula is: , , S05. Based on the known geometric parameters of the axial flow compressor elementary stage and the static pressure of the rotor blade inlet calculation station , static temperature , determine the airflow density at the rotor blade inlet calculation station and traffic , the specific formula is: , , Where, Equal to 287.03, which is the gas state constant. At this time, the flow rate of the first axial flow compressor elementary stage moving blade inlet calculation station is output. At this time, the flow rate of the rotor blade inlet calculation station is Equal to the calculated station flow rate at the outlet of the inlet guide vane of the axial compressor; S06. According to the conservation relationship of conversion enthalpy, the static pressure of the station is calculated based on the moving blade outlet. , circumferential speed and the relative total temperature of the blade inlet calculation station , circumferential speed , then, the relative total temperature of the blade outlet calculation station is Determined as: , Where, is equal to 1004.0, which is the specific heat capacity at constant pressure; Based on the rotor blade loss coefficient : , Thus, according to the isentropic relationship, the ideal relative total pressure at the blade outlet calculation station is determined for: , Where, is equal to 1.4, which is the specific heat constant; Because the moving blade loss coefficient It is calculated by the loss model in the axial flow compressor performance analysis calculation model, and then the relative total pressure at the moving blade outlet calculation station is determined. for: , Then, the static pressure of the station is calculated based on the assigned moving blade outlet. , and the relative total temperature of the blade outlet calculation station and relative total pressure According to the isentropic relationship, the static temperature of the blade outlet calculation station is determined for: , S07, calculate the relative total temperature of the station based on the blade outlet and Jingwen The relationship between the blade outlet and the calculation station is used to determine the relative speed of the blade outlet. is: , Continuing, according to the velocity triangle relationship, determine the circumferential velocity at the outlet of the moving blade outlet calculation station , relative circumferential velocity , absolute circumferential velocity and absolute velocity , and the specific formula is: , , , , In the formula, is the relative flow angle at the outlet of the moving blade outlet calculation station, which is calculated by the trailing angle model in the axial compressor performance analysis and calculation model; S08. According to the concept of stagnation state, given the absolute velocity and static temperature at the outlet of the moving blade outlet calculation station, determine the total temperature at the outlet of the moving blade outlet calculation station as: , S09. According to the isentropic relationship, as well as the static temperature , total temperature , static pressure at the outlet of the moving blade outlet calculation station, determine the total pressure at the outlet of the moving blade outlet calculation station as: , The gas flow density and flow rate at the outlet of the moving blade outlet calculation station are: , , At this time, the flow rate of the first-stage axial compressor elementary stage moving blade outlet calculation station is obtained.

[0021] S10. According to the static pressure at the outlet of the stator blade outlet calculation station, the total pressure at the inlet of the stator blade calculation station and the operating characteristics of the stator blade being stationary in the axial compressor elementary stage, the gas flow in the stator blade belongs to an adiabatic non-isentropic flow, thus determining that the total temperature at the outlet of the stator blade outlet calculation station is equal to the total temperature at the inlet of the stator blade calculation station; S11. Determine the total pressure at the outlet of the stator blade outlet calculation station as: , wherein, is the static blade loss coefficient, which is calculated by the loss model in the axial flow compressor performance analysis and calculation model; Then, according to the static pressure , total temperature , and total pressure at the static blade outlet calculation station, determine the static temperature at the static blade outlet calculation station as: , S12. Continuing according to the isentropic relationship, combining the known total temperature and static temperature at the static blade outlet calculation station, and the absolute flow angle at the static blade outlet calculation station determined by the stagger angle model in the axial flow compressor performance analysis and calculation model, determine the absolute velocity , axial velocity at the static blade outlet calculation station, specifically: , , wherein, is equal to 1004.0, which is the specific heat capacity at constant pressure; At the same time, determine the gas density and flow rate at the static blade outlet calculation station, specifically: , , wherein, is equal to 287.03, which is the gas state constant; At this time, the flow rate at the static blade outlet calculation station is obtained, and in this embodiment, the calculation of the performance parameters of the first axial flow compressor elementary stage is completed; S13. According to the principle that the absolute flow angle, total temperature, and total pressure at the moving blade inlet calculation station of the next axial flow compressor elementary stage are the same as those at the static blade outlet calculation station of the previous axial flow compressor elementary stage, and in accordance with the calculation methods in steps S03 to S12, after the performance parameters of each elementary stage are calculated, and it is determined that the current elementary stage is the last axial flow compressor elementary stage in the axial flow compressor, the flow rate at the moving blade outlet calculation station and the flow rate at the static blade outlet calculation station in all the elementary stages included in the axial flow compressor are obtained; S14. Based on the least squares method, through the flow rate at the moving blade inlet calculation station, the flow rate at the moving blade outlet calculation station, and the flow rate , the objective function for measuring the flow difference of the elementary stage of the axial compressor is established as follows: , In the formula, , , are the flow rates at the calculation stations at the inlet of the rotor blade , the flow rates at the calculation stations at the outlet of the rotor blade , and the flow rates at the calculation stations at the outlet of the stator blade .

[0022] Step 5: Based on the objective function, using the static pressure at the calculation station at the inlet of the rotor blade and the static pressure at the calculation station at the outlet of the rotor blade as the optimization variables, according to the law of conservation of flow rate, use the variable optimization formula to continuously update the optimization variables until the value of the objective function is less than 10 -8 , and the variable optimization formula is: , In the formula, is the updated input variable, is the input variable before update, is the learning rate, representing the magnitude of the parameter adjustment in the optimization process, is the output variable corresponding to when is the input variable; includes , , , and , , [[ID=5m6]] are the flow rates at the calculation stations at the inlet of the rotor blade , the flow rates at the calculation stations at the outlet of the rotor blade , and the flow rates at the calculation stations at the outlet of the stator blade ; At this time, the updated performance parameters of the axial compressor are obtained.

[0023] As Figures 2 - 13 shown, in order to further illustrate the technical solution and technical effect of the present invention, the following specific calculation examples are provided: Specific calculation example 1: As Figures 2 - 9 shown, taking the three-stage axial compressor PW3S1 as an example, as Figure 2 shown, the schematic diagram of the elementary stage structure of the axial compressor, where R represents the rotor blade and S represents the stator blade; the elementary stage of the axial compressor consists of a row of rotor blades and a row of stator blades, and the number of stages of the axial compressor is determined by the number of elementary stages contained in the axial compressor; Define the calculation stations in the elementary stage of an axial flow compressor, including the calculation station at the inlet of the rotor blade, the calculation station at the outlet of the rotor blade, the calculation station at the inlet of the stator blade, and the calculation station at the outlet of the stator blade; the air flow in the elementary stage of the axial flow compressor flows axially into from the calculation station at the inlet of the rotor blade, successively passes through the calculation station at the outlet of the rotor blade, the calculation station at the inlet of the stator blade, and flows out from the calculation station at the outlet of the stator blade; Among them, it mainly includes the annulus area of the axial flow compressor calculation station , the median line radius of the axial flow compressor calculation station , the rotational speed of the axial flow compressor , the absolute air flow angle , where is the number of the calculation station in the elementary stage of the axial flow compressor. Among them, the calculation station at the inlet of the guide vane , the calculation station at the outlet of the guide vane , the calculation station at the outlet of the first-stage rotor blade , the calculation station at the outlet of the first-stage rotor blade , the calculation station at the inlet of the first-stage stator blade , the calculation station at the outlet of the first-stage stator blade , the calculation station at the inlet of the second-stage rotor blade , the calculation station at the outlet of the second-stage rotor blade , the calculation station at the inlet of the second-stage stator blade , the calculation station at the outlet of the second-stage stator blade , the calculation station at the inlet of the third-stage rotor blade , the calculation station at the outlet of the third-stage rotor blade , the calculation station at the inlet of the third-stage stator blade , the calculation station at the outlet of the third-stage stator blade ; among them, the median line position is also shown in Figure 2 ; Such as Figure 3 shown in the three-stage axial flow compressor PW3S1, which consists of the first row of inlet guide vanes and three successively arranged elementary stages. The air flow in the three-stage axial flow compressor PW3S1 flows axially into from the calculation station at the inlet of the guide vane, successively passes through the calculation station at the outlet of the guide vane, the calculation station at the outlet of the first-stage rotor blade, the calculation station at the outlet of the first-stage rotor blade, the calculation station at the inlet of the first-stage stator blade, the calculation station at the outlet of the first-stage stator blade, the calculation station at the inlet of the second-stage rotor blade, the calculation station at the outlet of the second-stage rotor blade, the calculation station at the inlet of the second-stage stator blade, the calculation station at the outlet of the second-stage stator blade, the calculation station at the inlet of the third-stage rotor blade, the calculation station at the outlet of the third-stage rotor blade, the calculation station at the inlet of the third-stage stator blade, and flows out from the calculation station at the outlet of the third-stage stator blade; the specific calculation example 1 of the present invention is Figure 3 [[ID=, the three-stage axial flow compressor PW3S1 shown in ; The specific method steps of the present invention are as follows: Step 1: Given the boundary conditions of the three-stage axial flow compressor PW3S1 in the calculation model for the performance analysis of the axial flow compressor; The boundary conditions for the performance analysis of the elemental stage of an axial compressor include: the absolute flow angle of the incoming air at the inlet of the rotor blade , the total temperature at the inlet of the rotor blade , the total pressure at the inlet of the rotor blade , the geometric parameters of each calculation station in the elemental stage of the axial compressor, the static pressure at the outlet of the stator blade and the static pressure at the inlet of the rotor blade and the ratio of the total pressure at the inlet of the rotor blade ; Among them, in the boundary conditions, the absolute flow angle, total temperature, and total pressure given in the example at the inlet of the inlet guide vane , total temperature , total pressure , the static pressure at the outlet of the stator blade in the last elemental stage , the rotational speed of the axial compressor and the geometric parameters of each calculation station in the elemental stage of the axial compressor; In addition, it should be noted that if the axial compressor includes an inlet guide vane, the absolute flow angle, total temperature, and total pressure described in the boundary conditions are the parameters at the inlet of the inlet guide vane; the parameters at the inlet and outlet in the boundary conditions refer to the parameters at the inlet of the first blade row in the axial compressor; Step 2: Determine the static pressure at the inlet of the inlet guide vane of the first elemental stage according to the pressure ratio at the inlet of the first row of inlet guide vanes, and combine it with the static pressure at the outlet of the stator blade of the last elemental stage, so as to initialize and allocate the static pressures at the outlets of the rotor and stator blades of other elemental stages as: , , , , , ; In addition, the three-stage axial compressor PW3S1 includes an inlet guide vane. The parameter calculations at the inlet and outlet of the inlet guide vane are the same as those at the inlet and outlet of the stator blade. The following steps are carried out in the order of the elemental stage, starting from the inlet of the first-stage rotor blade; Step 3: Solve the parameters at the inlet of the rotor blade: According to the boundary conditions given in Step 3 and the static pressures , , , allocated at the outlets of the rotor and stator blades in Step 4 , , , calculate the solution for the three-stage axial compressor PW3S1 for each calculation station in the order of the stator blade inlet calculation station, stator blade outlet calculation station, rotor blade inlet calculation station, and rotor blade outlet calculation station according to the order of the elementary level: First, perform parameter calculations for the rotor blade inlet calculation station of the first stage. Based on the total temperature of the rotor blade inlet calculation station of the first stage, the total pressure of the rotor blade inlet calculation station of the first stage, and the static pressure of the rotor blade inlet calculation station of the first stage, determine the static temperature of the rotor blade inlet calculation station of the first stage: , where is the specific heat ratio, a constant, approximately 1.4; Furthermore, determine the absolute velocity of the rotor blade inlet calculation station of the first stage according to the concept of the stagnation state: , where is the specific heat at constant pressure, a constant, approximately 1004.0; Furthermore, based on the absolute flow angle of the rotor blade inlet calculation station of the first stage and the velocity triangle relationship in Figure 4 , determine the axial velocity of the rotor blade inlet calculation station of the first stage. According to the rotational speed of the axial compressor and the median radius of the rotor blade inlet calculation station of the first stage, determine the circumferential velocity of the rotor blade inlet calculation station of the first stage, the absolute circumferential velocity of the rotor blade inlet calculation station of the first stage, the relative circumferential velocity of the rotor blade inlet calculation station of the first stage, and the relative velocity of the rotor blade inlet calculation station of the first stage: , , , , , Determine the relative total temperature and relative total pressure of the rotor blade inlet calculation station of the first stage according to the thermodynamic relationship: , , Furthermore, the static pressure of the station is calculated based on the known geometric parameters and the first stage rotor blade inlet. 、Static temperature of the first stage rotor blade inlet calculation station , determine the airflow density at the first stage rotor blade inlet calculation station and the flow rate of the first stage rotor blade inlet calculation station : , , Furthermore, according to the law of flow conservation, the flow rate of the first stage rotor blade inlet calculation station is determined Is it equal to the flow rate of the inlet guide vane outlet calculation station? , iteratively adjust the axial speed of the first stage rotor blade inlet calculation station according to the difference between the two Flow rate to the first stage rotor blade inlet calculation station Calculate the flow rate of the outlet of the inlet guide vane Keep consistent; at the same time, the thermal parameters of the first-stage rotor blade inlet calculation station are kept updated during the iteration process; Step 6: Solve the parameters of the rotor blade outlet calculation station: The static pressure of the first stage moving blade outlet is calculated based on the static pressure of the first stage moving blade outlet determined in step 4. , and the conservation relationship of transfer enthalpy, the relative total temperature of the blade outlet calculation station Calculate the relative total temperature of the station through the blade inlet And the circumferential speed of the blade outlet calculation station Sure: , Furthermore, the blade loss coefficient Calculated by the following formula: , Determine the ideal relative total pressure at the first stage moving blade outlet calculation station based on the isentropic relationship : , Due to the blade loss coefficient The relative total pressure at the first stage moving blade outlet calculation station can be determined by calculating the loss model in the performance prediction program. : , Furthermore, the station static pressure is calculated based on the allocated first stage moving blade outlet , and the relative total temperature of the first stage moving blade outlet calculation station and the relative total pressure at the first stage rotor blade outlet calculation station , according to the isentropic relationship, the static temperature of the first stage moving blade outlet calculation station is determined : , Furthermore, the relative flow angle at the outlet calculation station of the first-stage moving blade is calculated by the stagger angle model in the performance prediction program; Furthermore, according to the relationship between the relative total temperature at the outlet calculation station of the first-stage moving blade and the static temperature at the outlet calculation station of the first-stage moving blade the relative velocity at the outlet calculation station of the first-stage moving blade is determined : , Furthermore, according to the velocity triangle relationship, the circumferential velocity at the outlet of the outlet calculation station of the first-stage moving blade , the relative circumferential velocity at the outlet calculation station of the first-stage moving blade , the absolute circumferential velocity at the outlet calculation station of the first-stage moving blade and the absolute velocity at the outlet calculation station of the first-stage moving blade are determined: , , , [[ID=XX]] , Furthermore, according to the concept of stagnation state, given the absolute velocity at the outlet calculation station of the first-stage moving blade and the static temperature at the outlet calculation station of the first-stage moving blade the total temperature at the outlet calculation station of the first-stage moving blade is determined as: , Furthermore, according to the isentropic relationship, and the static temperature at the outlet calculation station of the first-stage moving blade , the total temperature at the outlet calculation station of the first-stage moving blade , the static pressure at the outlet calculation station of the first-stage moving blade the total pressure at the outlet calculation station of the first-stage moving blade is determined as: , Furthermore, a method similar to that in step five is used to determine the gas density at the outlet calculation station of the first-stage moving blade and the flow rate at the outlet calculation station of the first-stage moving blade: , , The parameter calculation of the outlet calculation station of the first-stage moving blade is completed, and the flow rate at the outlet calculation station of the first-stage moving blade is output; Step 7: Solve the parameters of the inlet calculation station of the stationary blade: The air flow exits from the calculation station at the outlet of the first-stage moving blades and directly enters the calculation station at the inlet of the first-stage stationary blades. According to the conservation of flow rate, the flow rate at the calculation station at the inlet of the first-stage stationary blades is determined. which is the flow rate at the calculation station at the outlet of the first-stage moving blades ; Furthermore, according to the characteristics of isentropic flow with no energy addition, the total temperature at the calculation station at the inlet of the first-stage stationary blades is determined to be equal to the total temperature at the calculation station at the outlet of the first-stage moving blades , and the total pressure at the calculation station at the inlet of the first-stage stationary blades is equal to the total pressure at the calculation station at the outlet of the first-stage moving blades ; Furthermore, the absolute circumferential velocity at the calculation station at the inlet of the first-stage stationary blades is determined through constant-circulation calculation :

[0024] Furthermore, assuming the axial velocity at the calculation station at the inlet of the first-stage stationary blades , based on the absolute circumferential velocity at the calculation station at the inlet of the first-stage stationary blades , the total temperature at the calculation station at the inlet of the first-stage stationary blades , the absolute velocity at the calculation station at the inlet of the first-stage stationary blades and the static temperature at the calculation station at the inlet of the first-stage stationary blades are determined: , , Furthermore, according to the isentropic relationship, as well as the total temperature at the calculation station at the inlet of the first-stage stationary blades , the static temperature at the calculation station at the inlet of the first-stage stationary blades , the total pressure at the calculation station at the inlet of the first-stage stationary blades , the static pressure at the calculation station at the inlet of the first-stage stationary blades is determined: , Furthermore, based on the static pressure at the calculation station at the inlet of the first-stage stationary blades , the static temperature at the calculation station at the inlet of the first-stage stationary blades , the air flow density at the calculation station at the inlet of the first-stage stationary blades and the flow rate at the calculation station at the inlet of the first-stage stationary blades are determined: , , Furthermore, according to the conservation of flow rate, it is judged whether the flow rate at the calculation station at the inlet of the first-stage stationary blades is equal to the flow rate at the calculation station at the outlet of the first-stage moving blades , and the axial velocity at the calculation station at the inlet of the first-stage stationary blades Flow rate to the first stage stator inlet calculation station Calculate the flow rate at the outlet of the first stage rotor blade Keep consistent; at the same time, the thermal parameters of the calculation station of the first-stage stator inlet are kept updated during the iteration process; Step 8. Solve the parameters of the stationary blade outlet calculation station: Static pressure of the first stage stator outlet calculation station In step 3, it has been determined that according to the operating characteristics of the static stator blades in the elementary stage of the axial flow compressor, the air flow in the stator blades belongs to absolute energy non-isentropic flow, and the total temperature of the calculation station at the outlet of the first stage stator blade is determined. Equal to the total temperature of the first stage stator inlet calculation station ; Furthermore, the stator loss coefficient Calculated by the following formula: , Furthermore, the stator loss coefficient The total pressure at the first stage station blade outlet is determined by the loss model in the performance prediction program. : , Furthermore, the static pressure at the first stage stator outlet is calculated , total pressure at the first stage station blade inlet calculation station 、Total temperature of the first stage stator blade inlet calculation station , determine the static temperature of the first stage stator blade outlet calculation station : , Furthermore, based on the concept of stagnation state, the total temperature of the station is calculated by combining the known first-stage stator outlet. and the static temperature of the first stage stator blade outlet calculation station , and the absolute airflow angle at the first-stage stator outlet calculation station determined by the lagging angle model in the performance prediction program , determine the absolute speed of the first stage stator blade outlet calculation station And the axial velocity of the first stage stator blade outlet calculation station Size: , , Further, the airflow density at the first stage stator outlet calculation station is determined according to a method similar to step 5. and the flow rate of the first stage stator outlet calculation station : , , Complete the solution of the parameters at the outlet calculation station of the first-stage stator blades and output the flow rate at the outlet calculation station of the first-stage stator blades ; Step Nine: Judgment of the Axial Compressor Outlet: The outlet of the axial compressor is the outlet calculation station of the stator blades of the last elementary stage of the axial compressor; determine whether the outlet calculation station of the stator blades in Step Eight is the outlet of the axial compressor. For the three-stage axial compressor PW3S1, the outlet calculation station of the stator blades in Step Eight is the outlet of the first stage of the axial compressor. Since the three-stage axial compressor PW3S1 contains three elementary stages, continue with the parameter calculation of the next elementary stage and repeat Steps Four to Eight; Step Ten: For the three-stage axial compressor PW3S1, according to the static pressure at the calculation station assigned during initialization , , , , , , , , after the calculations in Steps Five to Nine, output the flow rates corresponding to the inlet calculation station of the inlet guide vane, the outlet calculation station of the inlet guide vane, the outlet calculation station of the first-stage rotor blades, the outlet calculation station of the first-stage stator blades, the outlet calculation station of the second-stage rotor blades, the outlet calculation station of the second-stage stator blades, the outlet calculation station of the third-stage rotor blades, and the outlet calculation station of the third-stage stator blades 、 、 、 、 、 、 、 ; In this step, for the sake of convenience of expression , , , , , , , are respectively denoted as , , , , , , , as the input variables for Steps Five to Eight, and 、 、 、 、 、 、 、 are respectively denoted as , , , , , , , as the output of the aforesaid Steps Five to Eight. According to the law of conservation of flow rate, that is ; Thus, by using the least squares method, the output variables are constructed as the objective function of the optimization problem : , Step Five: Based on the objective function, with the static pressure at the inlet calculation station of the inlet guide vane , the static pressure at the inlet calculation station of the inlet guide vane , the static pressure at the outlet calculation station of the first-stage rotor blade , the static pressure at the outlet calculation station of the first-stage stator blade , the static pressure at the outlet calculation station of the second-stage rotor blade , the static pressure at the outlet calculation station of the second-stage stator blade , the static pressure at the outlet calculation station of the third-stage rotor blade being the optimization variables, according to the law of conservation of flow rate, the variable optimization formula is used to continuously update the optimization variables until the value of the objective function is less than 10 -8 , that is, the updated axial compressor performance parameters are obtained; The variable optimization formula is: , wherein, is the updated input variable, is the input variable before update, is the learning rate, representing the magnitude of the parameter adjustment in the optimization process, is the output variable corresponding to when it is the input variable, the output variable corresponding to the axial compressor outlet; the subscript represents the th input, ; After determining the direction of updating the input static pressure, determine the magnitude of the update step; according to the situation that the input static pressures at each calculation station in the axial compressor are inconsistent, in combination with the learning rate and to determine that the update step of the input static pressure at each calculation station is matched with it; Meanwhile, during the optimization process, continuously adjust the input variables , , , , , , The value ensures that the output flow of each computing station continuously tends to be conserved, and the objective function value continuously approaches 0. After reaching the convergence criterion, the calculation ends and the performance parameters of the axial flow compressor are obtained.

[0025] Finally, the simulation parameters of the three-stage axial flow compressor PW3S1 optimized are as follows: The total inlet pressure is 101325 pa, the total inlet temperature is 288.15 K, the rotational speed is 5455 RPM, the flow rate is 4.29 kg / s, and there are 14 computing stations in seven rows of blades. Verification of the simulation results of the three-stage axial flow compressor PW3S1: First step, the one-dimensional analysis program of the axial flow compressor with the flow rate as the boundary condition is used to calculate the above working conditions. The total pressure and static pressure distributions of each computing station are as Figure 5 shown, where the abscissa is the label of each computing station and the ordinate is the pressure; The axial velocity distributions of each computing station obtained are as Figure 6 shown, where the abscissa is the label of each computing station and the ordinate is the velocity. Under the design point working condition, the static pressure at the outlet computing station of the third-stage stator blades of the three-stage axial flow compressor PW3S1 is 14430.5 pa; Second step, the static pressure at the outlet computing station of the third-stage stator blades of the three-stage axial flow compressor PW3S1 obtained in the first step and the boundary condition parameters are used as inputs, and the calculation is carried out according to the steps described in the present invention.

[0026] The calculation results are compared with the results obtained in the first step. The comparisons of the total pressure and static pressure distributions of each computing station are as Figure 7 shown, where the abscissa is the label of each computing station and the ordinate is the pressure; the circle line is the calculation result of the one-dimensional analysis program of the axial flow compressor with the flow rate as the boundary condition, and the cross line is the calculation result of the one-dimensional analysis program of the axial flow compressor with the pressure as the boundary condition.

[0027] The comparison results of the axial velocities of each computing station are as Figure 8 shown, where the abscissa is the label of each computing station and the ordinate is the velocity; the circle line is the calculation result of the one-dimensional analysis program of the axial flow compressor with the flow rate as the boundary condition, and the cross line is the calculation result of the one-dimensional analysis program of the axial flow compressor with the pressure as the boundary condition.

[0028] The flow convergence history in the final optimization process described in the present invention is as Figure 9 shown; Analysis of the simulation results of the three-stage axial flow compressor PW3S1: Conclusion 1: Figure 7 In the comparison results of the total pressure and static pressure and Figure 8The comparison results of the axial velocity show that the calculation results obtained by using the method described in the present invention are in complete agreement with the calculation results of the one-dimensional analysis program using the flow boundary condition, which proves that the method described in the present invention has the ability to predict the performance parameters of each calculation station of the compressor; Conclusion 2: From Figure 9 the convergence history of the medium flow rate, it can be seen that the inlet and outlet flows gradually tend to be consistent during the program calculation process, and converge to the flow rate corresponding to this working condition; Conclusion 3: The simulation data shows that the method described in this patent can replace the traditional one-dimensional analysis program of the axial compressor with the flow as the boundary condition for performance prediction of the compressor. The feasibility and effectiveness of the theory and method proposed in this patent have been verified.

[0029] Specific example 2: As Figures 10 - 13 shown, this specific example is mainly to analyze and calculate the performance parameters of the axial compressor in the choked state. Since the flow rate remains unchanged in the choked state of the axial compressor, its performance is related to the losses and stagger angles of the blade rows where choking occurs. At this time, the magnitudes of the losses or stagger angles are related to the static pressure at the outlet of the blade row and the choked flow rate.

[0030] The method provided in this application also provides a basic condition for the axial compressor performance analysis and calculation model to predict the performance of the axial compressor in the choked state. Due to the lack of a supporting model for predicting the magnitudes of losses and stagger angles, the verification of the present invention regarding the choked state of the axial compressor is relatively difficult.

[0031] However, the exhaust flow passage of the axial compressor in the choked state is similar to a Laval nozzle, and the gas flow state is similar to the supercritical state with a subsonic outlet in the Laval nozzle. Therefore, the second example of the present invention is the calculation of a symmetric Laval nozzle from the inlet through the throat to the outlet, as Figure 10 shown, where there are a total of 3 calculation stations, namely the inlet calculation station 1, the throat calculation station 2, and the outlet calculation station 3; when initializing, the static pressures of the 3 calculation stations are given, and the following steps are used for calculation: Step 1: Given the boundary conditions for calculating the Laval nozzle using the back pressure boundary condition: Among them, the boundary conditions include: the absolute gas flow angle at the inlet calculation station, the total temperature , the total pressure , the static pressure at the outlet calculation station. Here, the static pressure at the outlet calculation station is not limited to a single value, and multiple static pressures at the outlet calculation station will be given for calculation; Step 2: Determine the static pressure at the inlet calculation station according to the pressure ratio at the inlet calculation station, and combine it with the static pressure at the outlet calculation station, so as to initialize and allocate the static pressure at the throat calculation station : , Step 3: Calculate the import calculation station, the throat calculation station, and the outlet calculation station in sequence. According to the boundary conditions, solve for the flow rate of the import calculation station , the flow rate of the throat calculation station , and the flow rate of the outlet calculation station : Step 4: Based on the least squares method, through the flow rate of the import calculation station , the flow rate of the throat calculation station , and the flow rate of the outlet calculation station , establish an objective function for measuring the differences in the flow rates of the import calculation station, the throat calculation station, and the outlet calculation station of the Laval nozzle; Step 5: Based on the objective function, with the static pressure of the import calculation station , and the static pressure of the throat calculation station as the optimization variables, according to the law of conservation of flow rate, use the variable optimization formula to continuously update the optimization variables until the value of the objective function is less than 10 -8 , that is, obtain the updated performance parameters of the Laval nozzle.

[0032] Laval nozzle simulation results: As the static pressure of the outlet calculation station of the Laval nozzle continuously decreases, the Laval nozzle enters the supercritical state, and this state corresponds to the blockage state in the axial flow compressor. At this time, the throat of the Laval nozzle becomes blocked, and the flow rate of the entire nozzle no longer changes, as Figure 11 shown, where the abscissa is the flow rate and the ordinate is the static pressure at the outlet of the Laval nozzle; After the nozzle is in the supercritical state, the outlet Mach number calculated by the method described in the present invention is compared with the analytical solution obtained by theoretical calculation, and the comparison results are as Figure 12 shown, where the abscissa is the outlet Mach number and the ordinate is the ratio of the static pressure at the outlet calculation station of the Laval nozzle to the total pressure at the import calculation station of the Laval nozzle; the circled points are the theoretical calculation results, and the solid line is the calculation result of the method described in the present invention; Under a certain supercritical condition of the Laval nozzle, the convergence history of the flow rate of the import calculation station of the Laval nozzle, the flow rate of the throat calculation station of the Laval nozzle, and the flow rate of the outlet calculation station of the Laval nozzle is as Figure 13 shown, where the abscissa is the number of iteration steps and the ordinate is the flow rate; the solid line, the dashed line, and the dotted line are the flow rate changes of the import calculation station, the outlet calculation station, and the throat calculation station of the Laval nozzle respectively; Analysis of Laval nozzle simulation results: Conclusion 1: From Figure 11It can be seen that as the static pressure at the calculation station at the outlet of the Laval nozzle continuously decreases, the Laval nozzle gradually enters the supercritical state. At this time, the flow rate in the nozzle continuously changes, and the trend of the flow rate change in the Laval nozzle is successfully predicted; Conclusion 2: From Figure 12 the comparison between the calculation results of the method described in the present invention and the theoretical calculation, it can be seen that the method described in the present invention can accurately predict the change of the outlet Mach number after the Laval nozzle is blocked. Since there are shock waves and losses in the expansion section of the nozzle after it enters the supercritical state, and the magnitude of the losses directly affects the magnitude of the outlet Mach number, the successful prediction of the outlet Mach number can represent the effectiveness of the method described in the present invention; Conclusion 3: From Figure 13 It can be seen that the flow rates at the three calculation stations in the Laval nozzle all converge stably to the expected flow rate as the number of iterations increases; Conclusion 4: The simulation data shows that the method described in this patent has the ability to capture the flow rate and performance of the Laval nozzle in the blocked state, and at the same time proves that the method described in this patent provides the basic conditions for the one-dimensional and two-dimensional analysis programs of axial compressors to predict the performance of axial compressors in the blocked state.

[0033] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An axial compressor performance prediction method using backpressure boundary conditions, characterized in that Including the following steps: Step 1. Given the boundary conditions for a blade row of an axial compressor in the performance analysis of an axial compressor. The boundary conditions include: the absolute flow angle at the inlet calculation station of the rotor blade , the total temperature , the total pressure , the pressure ratio ; the static pressure at the outlet calculation station of the stator blade , the rotational speed of the axial compressor and the geometric parameters of the blade row of the axial compressor. Step 2: According to the pressure ratio at the moving blade inlet calculation station The static pressure at the moving blade inlet calculation station determined , combined with the static pressure at the stator blade outlet calculation station , thereby initializing and distributing the static pressure at the moving blade outlet calculation station as follows: ， Step 3: Based on the axial flow compressor performance analysis and calculation model and the number of elementary stages of the axial flow compressor, calculate the performance parameters of the moving blade inlet, moving blade outlet calculation station, stator blade inlet, and stator blade outlet calculation station of the axial flow compressor in the air flow direction of the axial flow compressor one by one for each elementary stage. The calculation process for each elementary stage of the axial flow compressor is as follows: First, according to the boundary conditions, solve for the flow rate at the inlet computational station of the rotor blade of the elemental stage of the axial-flow compressor. ; According to the static pressure at the outlet computational station of the rotor blade , solve for the flow rate at the outlet computational station of the rotor blade ; Next, based on the flow rate at the moving blade outlet calculation station , the performance parameters at the stator blade inlet calculation station are solved; Among them, the performance parameters include the total temperature at the inlet calculation station of the stator blades , the total pressure , the absolute circumferential velocity , the axial velocity , the absolute velocity , the static temperature , the static pressure ; Finally, according to the performance parameters of the stator inlet calculation station and the static pressure of the stator outlet calculation station , calculate the flow rate of the stator outlet calculation station , that is, complete the calculation of the performance parameters of the elementary stage of the axial flow compressor; After the performance parameters of each elementary stage are calculated, determine whether the current elementary stage is the last elementary stage of the axial flow compressor, that is, obtain the flow rate at the moving blade outlet calculation station and the flow rate at the stator blade outlet calculation station in each elementary stage of the axial flow compressor; Step 4: Based on the least squares method, calculate the flow rate at the moving blade inlet calculation station , the flow rate at the moving blade outlet calculation station , and the flow rate at the stator blade outlet calculation station , and establish an objective function for measuring the flow rate difference of the elementary stage of the axial flow compressor; Step 5: Based on the objective function, with the static pressure at the inlet calculation station of the moving blade and the static pressure at the outlet calculation station of the moving blade as the optimization variables, according to the law of conservation of flow rate, continuously update the optimization variables using the variable optimization formula until the value of the objective function is less than 10 -8 , thus obtaining the updated performance parameters of the axial flow compressor.

2. The axial flow compressor performance prediction method using backpressure boundary conditions as described in claim 1, characterized in that, In Step 3, the flow rate at the moving blade inlet calculation station is equal to the flow rate at the outlet calculation station of the inlet guide vane of the axial flow compressor.

3. The axial compressor performance prediction method using backpressure boundary conditions according to claim 1, characterized in that, In Step 3, in the calculation of each elementary stage, the absolute air flow angle, total temperature, and total pressure at the moving blade inlet calculation station of the next elementary stage of the axial flow compressor are the same as the absolute air flow angle, total temperature, and total pressure at the stator blade outlet calculation station of the previous elementary stage of the axial flow compressor.

4. The axial compressor performance prediction method using backpressure boundary conditions as described in claim 1, wherein The flow rate of the moving blade inlet calculation station described in Step 3 The solution process is as follows: First, according to the total temperature , total pressure , and static pressure at the moving blade inlet calculation station, determine that the static temperature at the moving blade inlet calculation station is: ， In the formula, is equal to 1.4, which is the specific heat ratio constant; Next, according to the isentropic relationship, the absolute velocity at the inlet calculation station of the moving blade is determined as follows: ， wherein, equals 1004.0, which is the specific heat capacity at constant pressure; Furthermore, successively, according to the absolute flow angle at the inlet calculation station of the moving blade , and according to the axial velocity at the inlet calculation station of the moving blade determined by the velocity triangle relationship ; according to the rotational speed of the axial flow compressor and the median radius at the inlet calculation station of the moving blade , determine the circumferential velocity , absolute circumferential velocity , relative circumferential velocity and relative velocity at the inlet calculation station of the moving blade. The specific formulas are as follows: ， ， ， ， ， Continuing, based on the thermodynamic relationships, determine the relative total temperature and the relative total pressure at the inlet calculation station of the moving blade. The specific formulas are as follows: ， ， Next, based on the geometric parameters of the known elementary stage of the axial flow compressor and the static pressure at the calculation station at the inlet of the rotor blade , static temperature , the gas density and flow rate at the calculation station at the inlet of the rotor blade are determined. The specific formula is as follows: ， ， In the formula, is equal to 287.03, which is the gas state constant. At this time, the flow rate of the inlet calculation station of the moving blade is output .

5. The axial compressor performance prediction method using backpressure boundary conditions according to claim 1, characterized in that, The flow rate of the moving blade outlet calculation station described in Step 3 The calculation process is as follows: Based on the conservation relation of enthalpy transfer, the static pressure at the outlet calculation station of the moving blade , the circumferential velocity and the relative total temperature at the inlet calculation station of the moving blade , the circumferential velocity , then, the relative total temperature at the outlet calculation station of the moving blade is determined as: ， wherein, is equal to 1004.0, which is the specific heat capacity at constant pressure; Based on the moving blade loss coefficient : ， Thus, according to the isentropic relationship, the ideal relative total pressure at the calculation station at the outlet of the moving blade is determined as follows: ， Wherein, is equal to 1.4, which is the specific heat ratio constant; Since the rotor blade loss coefficient is calculated by the loss model in the axial compressor performance analysis and calculation model, and then the relative total pressure at the rotor blade outlet calculation station is: ， Furthermore, based on the static pressure at the calculated outlet station of the moving blade that has been allocated , as well as the relative total temperature and the relative total pressure at the calculated outlet station of the moving blade, according to the isentropic relationship, the static temperature at the calculated outlet station of the moving blade is determined as follows: ， Based on the relationship between the relative total temperature and the static temperature at the moving blade outlet calculation station, determine the relative velocity at the moving blade outlet calculation station and the static temperature The relative velocity at the moving blade outlet calculation station is determined as follows as follows: ， Continuing, based on the velocity triangle relationship, determine the circumferential velocity at the outlet of the moving blade outlet calculation station , relative circumferential velocity , absolute circumferential velocity and absolute velocity . The specific formula is as follows: ， ， ， ， In the formula, is the relative airflow angle at the outlet calculation station of the moving blade, which is calculated by the trailing angle model in the axial flow compressor performance analysis and calculation model; Furthermore, according to the stagnation state concept, the absolute velocity at the calculated station at the outlet of the moving blade and the static temperature are used to determine the total temperature at the calculated station at the outlet of the moving blade as follows: ， According to the isentropic relationship and the static temperature at the calculation station at the outlet of the moving blade , total temperature , static pressure , determine the total pressure at the calculation station at the outlet of the moving blade as: ， Airflow density at the moving blade outlet calculation station and the flow rate are as follows: ， ， At this time, the flow rate of the moving blade outlet calculation station is obtained. .

6. The axial compressor performance prediction method using backpressure boundary conditions according to claim 1, characterized in that The flow rate of the static blade outlet calculation station described in step three The specific calculation process is as follows: According to the static pressure at the calculation station at the outlet of the stator blade , the total pressure at the calculation station at the inlet of the stator blade and the operating characteristics of the stator blade being stationary in the elementary stage of the axial flow compressor, the gas flow in the stator blade belongs to adiabatic non-isentropic flow, thereby determining the total temperature at the calculation station at the outlet of the stator blade is equal to the total temperature at the calculation station at the inlet of the stator blade ; Next, determine the total pressure at the computational station at the outlet of the stator blades which is ， In the formula, is the static blade loss coefficient, which is calculated by the loss model in the axial flow compressor performance analysis and calculation model; Then, based on the static pressure at the calculated station of the stator vane outlet , total temperature , total pressure , determine the static temperature at the calculated station of the stator vane outlet as follows: ， Next, continue to determine the total temperature at the calculation station at the outlet of the stator vane according to the isentropic relationship, combined with the known total temperature at the outlet of the stator vane and the static temperature , as well as the absolute flow angle at the calculation station at the outlet of the stator vane determined by the trailing angle model in the axial compressor performance analysis and calculation model , to determine the absolute velocity and the axial velocity at the calculation station at the outlet of the stator vane. Specifically, it is as follows: ， ， In the formula, is equal to 1004.0, which is the specific heat capacity at constant pressure; Simultaneously determine the gas flow density at the calculation station at the outlet of the stationary blades and the flow rate , specifically as follows: ， ， In the formula, is equal to 287.03, which is the gas state constant; At this time, the flow rate of the stator vane outlet calculation station is obtained .

7. The axial compressor performance prediction method using backpressure boundary conditions according to claim 1, characterized in that The objective function established in Step 4 is as follows: ， In the formula, , , are the flow rates at the calculation stations at the inlet of the moving blades , the flow rates at the calculation stations at the outlet of the moving blades , and the flow rates at the calculation stations at the outlet of the stationary blades .

8. The axial compressor performance prediction method using backpressure boundary conditions according to any one of claims 1-7, characterized in that, The variable optimization formula in Step 5 is: ， In the formula, is the updated input variable, is the input variable before update, is the learning rate, representing the magnitude of parameter adjustment in the optimization process, is the output variable corresponding to when is the output variable corresponding to the axial compressor outlet; includes , , , and , , is the flow rate at the moving blade inlet calculation station , the flow rate at the moving blade outlet calculation station , and the flow rate at the stator blade outlet calculation station .

Images