A method and system for predicting multi-fluid performance of an ejector under all operating conditions

Abstract

This invention belongs to the field of ejector and fuel cell technology, and provides a multi-fluid performance prediction method and system for ejectors under all operating conditions. The method involves acquiring operating parameters and ejector geometric parameters; based on these parameters, and under preset conditions, modeling of critical points and recirculation points is performed to form a solution model for characteristic points of ejector performance, including the critical recirculation ratio. 、 Critical back pressure and recirculation back pressure; parameter identification of unknown parameters in the solution model; based on the identified unknown parameters, determining the values ​​of characteristic points under the target operating condition; and calculating the recirculation ratio, outlet temperature, and outlet fluid composition under the target operating condition based on the values ​​of the characteristic points, thus achieving prediction. This invention obtains the performance of the ejector under all operating conditions using a non-iterative solution method, which can meet the real-time control requirements of ejector-driven anode gas recirculation systems in fuel cells, which have characteristics such as wide operating range and fast response, under different operating conditions.

Description

Technical Field

[0001] This invention belongs to the field of ejector and fuel cell technology, specifically relating to a multi-fluid performance prediction method and system for ejectors under all operating conditions. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Proton exchange membrane fuel cells (PEMFCs) offer advantages such as high energy conversion efficiency, rapid start-up, and zero emissions, making them an important carrier for hydrogen energy applications. The anode gas recirculation system is a crucial component of the PEMFC system.

[0004] Typically, an excess of hydrogen needs to be supplied to the anode, and unreacted hydrogen needs to be recovered from the anode exhaust gas. This helps improve hydrogen utilization and removes product water to prevent flooding shutdowns. Ejectors, due to their simple structure, low noise, easy maintenance, and lack of parasitic power, have gradually become an effective method for hydrogen recovery. Anode gas recirculation systems are characterized by wide operating range, strong variable load, and fast response, requiring advanced control strategies to achieve the aforementioned goals.

[0005] Currently, some researchers have proposed models for predicting ejector performance, but none of the existing models are applicable to the real-time control of multi-fluid ejectors in fuel cell anode gas recirculation systems under all operating conditions, and they have the following drawbacks: Existing models are mostly used for ejector parameter design or performance analysis. The model structure is relatively complex, and the unknown parameters (component efficiency) in the model are mostly determined by empirical methods or identified by nonlinear methods, which inevitably increases the prediction error and the time required for parameter identification in the preliminary experiment.

[0006] The existing model contains coupled equations, which must be solved using iterative calculation methods with energy conservation constraints or defined convergence factors. This solution method is cumbersome and time-consuming, and therefore unsuitable for system modeling and real-time control.

[0007] Existing models are typically used for single-fluid gas ejectors, but in many scenarios, the working medium of the ejector is a typical multi-fluid, multi-component gas, that is, the primary flow is pure fuel (hydrogen / methane), and the secondary flow is a multi-component gas mixture from the anode outlet. Existing models are not applicable. Summary of the Invention

[0008] To address the aforementioned problems, this invention proposes a multi-fluid performance prediction method and system for ejectors under all operating conditions. This invention uses a non-iterative solution method to obtain the performance of the ejector under all operating conditions, which can meet the real-time control requirements of ejector-driven anode gas recirculation systems in fuel cells, which have characteristics such as wide operating range and fast response, under different operating conditions.

[0009] According to some embodiments, the present invention adopts the following technical solution: A multi-fluid performance prediction method for ejectors under all operating conditions includes the following steps: Obtain operating parameters and ejector geometric parameters; Based on the operating parameters and geometric parameters, and under preset conditions, the critical point and recirculation point are modeled separately to form a solution model for the characteristic points of the ejector performance. These characteristic points include the critical recirculation ratio. 、 Critical back pressure and reflux back pressure; Parameter identification is performed on the unknown parameters in the solution model; Based on the identified unknown parameters, the values ​​of characteristic points under the target operating conditions are determined. Based on the values ​​of the characteristic points, the recirculation ratio, outlet temperature, and outlet fluid composition under the target operating conditions are calculated to achieve prediction.

[0010] As an alternative implementation, the process of obtaining operating parameters and ejector geometric parameters includes: operating parameters including: primary flow pressure, secondary flow pressure, primary flow inlet temperature, secondary flow inlet temperature, and secondary flow fluid composition; The geometric parameters of the ejector include: nozzle throat area and mixing chamber area.

[0011] As an alternative implementation method, the preset conditions include: The flow inside the ejector is a one-dimensional adiabatic steady-state flow; The working medium is considered to be an ideal gas; Neglecting the kinetic energy of the fluid at the ejector inlet and outlet; The primary flow is blocked in front of the target section, and the secondary flow is blocked at the target section, that is, the Mach number of the secondary flow at this interface is 1; At the target cross-section, the two fluid streams begin to mix, and the pressure of the two streams at the target cross-section is equal to the pressure of the secondary stream.

[0012] As an alternative implementation, modeling the critical point includes: determining the primary flow control equation from the inlet to the target cross section, the secondary flow control equation from the inlet to the target cross section, and calculating the critical recirculation ratio.

[0013] As a further defined implementation, the primary flow control equation from the inlet to the target cross-section is: Pressure of the primary flow at the target cross section ppm 、 Ideal effective circulation area A pm ,temperature T pm and speed V pm They are respectively: ; ; ; ; ; in, p p For primary flow pressure, k p The adiabatic index of the primary flow is... A nt Let t be the area at the nozzle throat. M a pt Let t be the Mach number of the primary flow at the nozzle throat. M a pm and A' pm These are the Mach number and actual effective flow area of ​​the primary flow at the target interface. T p The primary inlet temperature, or pm It means A ' pm and A pm The component efficiency in relation to each other R g_p Let be the gas constant for the primary flow.

[0014] As a further defined implementation, the governing equation for the secondary flow from the inlet to the target cross-section is: the temperature of the secondary flow at the target cross-section... T sm ,speed V sm and effective circulation area A sm They are respectively: ; ; ; in, T s This refers to the secondary inlet temperature. M a sm It is the Mach number of the secondary flow at the target cross-section. ks The adiabatic index of the secondary flow. R g_s The gas constant for secondary flow. A' m It is the area of ​​the target cross-section, determined by a defined coefficient. f m , A' m Represented as: ; in, A 3 represents the cross-sectional area at the constant diameter of the mixing chamber.

[0015] coefficient f m The critical point and the reflux point are different, and are defined as follows: f m* and f mcb .

[0016] As a further defined implementation, the process of constructing a solution model for the characteristic points of ejector performance includes: ; ; ; in, oh * indicates the critical cycle ratio. p c* represents the critical back pressure. p cb is the backflow back pressure; x 1 -x 6. Related to inlet conditions and gas composition. k 1 -k 6 is only related to component efficiency and a defined coefficient, where: ; ; ; ; ; ; ; ; ; ; ; ; in, ps For secondary flow pressure, or s The component efficiency is used to determine the relationship between the theoretical and actual flow rates of the secondary flow. or p The component efficiency is the relationship between the theoretical flow rate and the actual flow rate of a single flow. oh The cycle ratio is... or d* The component efficiencies of the mixing chamber and diffusion chamber under critical conditions are given. or dcb For the component efficiency of the mixing chamber and diffusion chamber under reflux conditions, f d for A d and A nt The ratio, A d Let be the area at the outlet section (out).

[0017] As an alternative implementation, the solution model satisfies the following constraint: the subcritical recirculation ratio is approximated as the back pressure p. c The quadratic function, the axis of symmetry of the quadratic function is the critical back pressure. p c* Furthermore, the peak value of the quadratic function is the critical recurrence ratio. oh * .

[0018] As an alternative implementation, during the parameter identification process of the unknown parameters in the solution model, the least squares method is used to identify the unknown parameters in the solution model.

[0019] As an alternative implementation method, the recirculation ratio under the target operating condition is calculated. oh for: ; in, p c* For critical back pressure, p c For back pressure, the coordinates of the reflux point are ( p cb ,0); .

[0020] A multi-fluid performance prediction system for an ejector under all operating conditions includes: The parameter acquisition module is configured to acquire operating parameters and ejector geometric parameters. The model building module is configured to model the critical point and recirculation point under preset conditions based on operating parameters and geometric parameters, forming a solution model for the characteristic points of ejector performance, including the critical recirculation ratio. 、Critical back pressure and reflux back pressure; The parameter identification module is configured to identify unknown parameters in the solution model. The performance prediction module is configured to determine the value of the characteristic point under the target operating condition based on the identified unknown parameters, and calculate the recirculation ratio, outlet temperature and outlet fluid composition under the target operating condition based on the value of the characteristic point to achieve prediction.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention can predict the performance of ejectors under all operating conditions and has a simple and linear model structure. Compared with other models, the linear structure of the constructed solution model makes it easier to identify unknown parameters and has higher prediction accuracy. The solution process of the established model does not require a cyclic iteration process, so it is suitable for real-time system control and performance analysis.

[0022] This invention is applicable to multi-fluid and multi-component gas ejectors and conforms to the actual working conditions of various anode gas recirculation ejector working media.

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0025] Figure 1 A schematic diagram of an ejector-driven AGRS according to one embodiment; Figure 2 This is a schematic diagram of an ejector according to one embodiment; Figure 3 A schematic diagram of the ejector's operating mode and characteristic curves according to one embodiment; Figure 4 A flowchart illustrating ejector performance prediction in one embodiment; Figure 5 As one embodiment k 1- k 6 and D nt and Ar The relationship is given by a, b, c, d, e, and f, where a, b, c, d, e, and f are respectively... k 1. k2, k3, k4, k5 and k6 and D nt and Ar Relationship diagram. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0028] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0029] Where there is no conflict, the embodiments and features described in this application may be combined with each other.

[0030] Example 1 A multi-fluid performance prediction method for ejectors under all operating conditions includes the following steps: Obtain operating parameters and ejector geometric parameters; Based on the operating parameters and geometric parameters, and under preset conditions, the critical point and recirculation point are modeled separately to form a solution model for the characteristic points of the ejector performance. These characteristic points include the critical recirculation ratio. 、 Critical back pressure and reflux back pressure; Parameter identification is performed on the unknown parameters in the solution model; Based on the identified unknown parameters, the values ​​of characteristic points under the target operating conditions are determined. Based on the values ​​of the characteristic points, the recirculation ratio, outlet temperature, and outlet fluid composition under the target operating conditions are calculated to achieve prediction.

[0031] The following is a detailed introduction.

[0032] like Figure 1 and Figure 2 These diagrams illustrate the ejector-driven AGRS for PEMFCs and the ejector structure, respectively. High-pressure, dry hydrogen gas (the primary flow from the ejector) from the hydrogen storage tank is delivered to the ejector after pressure reduction. The high-pressure gas is accelerated in the nozzle, accompanied by a pressure decrease. This results in a low-pressure zone at the nozzle outlet, drawing the anode outlet gas (the secondary flow from the ejector) into the intake chamber. Subsequently, the two gas streams combine in the mixing chamber, achieving a pressure increase in the diffusion chamber. The combined fluid is then released at the anode inlet pressure (ejector outlet pressure, i.e., back pressure) required for fuel cell operation and fed into the fuel cell anode.

[0033] The efficiency of an ejector-driven AGRS in a fuel cell system depends on the performance of the ejector, which is a core component. Recycling ratio ( oh () is a commonly used parameter for evaluating ejector performance, defined as follows: (1) In the formula, m p and m s These are the mass flow rates of the primary flow and the secondary flow, respectively. Figure 3 The ejector's operating characteristic curve is shown under a fixed primary flow rate and pressure. p p ) and secondary flow pressure ( p s Under certain conditions, the ejector's operating mode can be determined based on the back pressure ( p c It is divided into critical mode, subcritical mode, and reflux mode. With... p c increase oh Initially remained unchanged ( oh * Then it gradually decreases to 0. This corresponds to the change in operating mode from critical to subcritical. The pressure at the critical operating point is defined as the critical back pressure ( p c* ).along with p c Continue to rise to the reflux back pressure ( p cb The operating mode changes to recirculation mode, and the ejector stops working.

[0034] To simplify the modeling process of the ejector, the following assumptions were used: 1. The flow inside the ejector is a one-dimensional adiabatic steady-state flow. 2. The working medium is considered to be an ideal gas.

[0035] 3. Neglect the kinetic energy of the fluid at the ejector inlet and outlet.

[0036] 4. The primary flow is blocked at section tt, and the secondary flow is blocked at section mm, meaning that the Mach number of the secondary flow at this interface is 1. 5. At section mm, the two fluids begin to mix, and the pressure of the two fluids at section mm is equal to the pressure of the secondary fluid.

[0037] Based on the above assumptions, the following relationship can be obtained: (2) (3) (4) in, M a sm It is the Mach number of the secondary flow at the target interface. M a pt Let t be the Mach number of the primary flow at the nozzle throat. p s For secondary flow pressure, p m The pressure at the cross-section mm is p sm The pressure of the secondary flow at the target cross-section. p sp The pressure of the primary flow at the target cross-section. k s The adiabatic index is the value of the secondary flow.

[0038] First, perform critical point modeling: (1) Primary flow control equation from inlet to cross-section mm Pressure of a single flow at a cross-section of mm ( p pm ) 、 Ideal effective circulation area ( A pm ),temperature( T pm ) and speed ( V pm It is obtained from the following formula: (5) (6) (7) (8) (9) in, p p For primary flow pressure, A nt Let t be the area at the nozzle throat. M a pm and A' pm These are the Mach number and actual effective flow area of ​​the primary flow at the target interface. T p The primary inlet temperature, or pm It means A ' pm and A pm The component efficiency in relation to each other R g_p Let be the gas constant for the primary flow.

[0039] (2) Secondary flow control equations from inlet to cross-section mm Temperature of the secondary flow at a cross-section of mm ( T sm ),speed( V sm ) and effective circulation area ( A sm It is obtained from the following formula: (10) (11) (12) in, T s This refers to the secondary inlet temperature. M a sm It is the Mach number of the secondary flow at the target cross-section. k s The adiabatic index of the secondary flow. R g_s The gas constant for secondary flow. A' m It is the area of ​​the target cross-section (mm). This is determined by defining a coefficient. f m , A' m It can be represented as: (13) in, A 3 represents the cross-sectional area of ​​the mixing chamber at the constant diameter section, i.e., section 3-3.

[0040] It is important to note that f m The critical point and the reflux point are different, and are defined as follows: f m* and f mcb .

[0041] (3) Calculation of critical recycle ratio The mass flow rate of the primary flow ( m p ) and the mass flow rate of the secondary flow ( m s It is obtained from the following formula: (14) (15) (16) A ntLet t be the area at the nozzle throat. D nt Let tt be the diameter at the nozzle throat. T p The primary inlet temperature, or p The component efficiency is the relationship between the theoretical flow rate and the actual flow rate of a single flow. or s The component efficiency is the relationship between the theoretical flow rate and the actual flow rate of the secondary flow.

[0042] When the secondary flow is a gas mixture, the gas constant of the secondary flow ( R g_s ) and specific heat ratio ( k s It can be obtained through the following formula: (17) (18) In the formula, Y s, i and X s, i Let i be the mass fraction and mole fraction of component i in the secondary flow, where i represents the component of the mixture.

[0043] Therefore, by setting the parameters, oh * It can be simplified to: (19) in, x 1. x 2. k 1 and k 2 is defined as: (20) (twenty one) (twenty two) (twenty three) in, oh This represents the cycle ratio.

[0044] Calculation of critical back pressure Considering that the primary purpose of this model is to predict ejector performance, the mixing and recompression processes of the two fluids are neglected for the sake of modeling simplicity. Using momentum, the following equation can be obtained from the cross-section mm to the outlet: (twenty four) in, or d* The component efficiencies of the mixing chamber and diffusion chamber under critical conditions are given.A d The area at the outlet section (out) Therefore, the critical back pressure ( p c* ) can be represented as: (25) Among them, coefficient f d express A d and A nt The ratio of .

[0045] Then, p c* It can be simplified to: (26) in, x 3. x 4. k 3 and k 4 is defined as: (27) (28) (29) (30) Next, we will model the reflow point: When the ejector is running in recirculation mode m s and V sm The value is zero. Based on the assumption, the value at the cross-section (mm) is zero. p sm equal p s Therefore, the following relationship can be obtained at the reflux point: (31) (32) (33) The momentum equation (24) can be modified as follows: (34) Therefore, the back pressure of the return flow ( p cb ) can be represented as: (35) in, or dcb For the component efficiency of the mixing chamber and diffusion chamber under reflux conditions, Then, by grouping the parameters together, p cb It can be simplified to: (36) in, x 5. x 6. k 5 and k 6 is defined as: (37) (38) (39) (40) Performance calculation under all operating conditions The above analysis shows that the critical recirculation ratio oh * Critical back pressure p c* and backflow back pressure p cb It can be represented as a linear expression, in the following form: (41) Where Γ is the objective function value, Ψ is the independent variable parameter, and X is the unknown parameter.

[0046] Specifically: (42) (43) (44) in, x 1 -x 6. Related to inlet conditions and gas composition. k 1 -k 6 Only related to component efficiency ( or p ,or pm , f ηs and ηd ) and the defined geometric coefficients ( f m and f d This relates to [the above]. In this embodiment, to simplify parameter identification, it is assumed that the above-mentioned efficiency and coefficients are constant for a given ejector, even though they may vary slightly due to operating conditions or structure. Thus, once identified... k 1 -k 6, can be obtained under any entry conditions. oh * , p c* and p cb .

[0047] For the linear expression (41), the parameters that need to be identified can be obtained using the least squares method: (45) By analyzing the ejector characteristic curves, such as Figure 3 As shown, the subcritical recycle ratio can be reasonably adjusted. oh sub It can be approximated as p c Quadratic function: (46) There are three unknown parameters A , B and C It requires three points to determine the parameters, making parameter identification difficult.

[0048] Considering oh For continuity, the critical point and reflux point must satisfy the above equation (46), therefore the following simplification is made: 1. The axis of symmetry of a quadratic function is the critical back pressure. p c* ; 2. The peak value of the quadratic function is the critical recurrence ratio. oh * . Then, the above expression (46) can be converted into the vertex expression of the quadratic function: (47) Introducing the coordinates of the return point ( p cb (0), we can get: (48) Therefore, for any working condition oh All can be calculated using the following formula: (49) Calculation of outlet flow rate, temperature, and composition According to the law of conservation of energy, we have: (50) in, Cp p The isobaric specific heat capacity of the primary flow. Cp s The isobaric specific heat capacity of the secondary flow. Cpc The isobaric specific heat capacity of the outlet fluid. T c The temperature of the outlet fluid.

[0049] m c It can be represented as: (51) Then, the above formula (50) can be converted to: (52) In the formula, the secondary flow is multi-component. C ps and C pc It can be calculated using the following formula: (53) (54) In the formula, Y c, i It is the mass fraction of component i in the mixed flow (outlet flow). For components that are the same as the mainstream, Y c, i It can be derived from the following formula: (55) For the other components, they Y c, j It can be derived in the following way: (56) The detailed calculation process of the ejector performance prediction model established in this invention is divided into two parts: model parameter identification and ejector performance prediction, such as... Figure 4 As shown. First, input the operating parameters, namely the inlet pressure and temperature ( p p , p s , T p and T s ), secondary flow composition ( Y s, i or X s, i ) and key geometry (nozzle throat area) A nt and mixing chamber area A 3). Then, the unknown parameters ( k 1- k6) The parameters can be determined based on experimental or simulation results. Due to the linear expression of the equation, parameter identification can be easily achieved using the least squares method. Secondly, based on the parameters determined in the first part, the recycle ratio under any operating conditions ( oh ), critical back pressure ( p c* ), backflow back pressure ( p cb ), outlet temperature ( T c ) and outlet fluid composition ( Y c, i or X c, i You can obtain it by doing so.

[0050] coefficient k 1- k 6. Relationship with geometric features From the above analysis, we can see that k 1- k Six are related to the structural parameters of the ejector (mainly including) D nt and D 3, and area ratio Ar = A 3 / A nt Therefore, in this embodiment, the ejector operating conditions vary within the range (430 ≤ p p ≤ 1700 kPa and 131≤ p s ≤ 215 kPa) and structural parameter variation range (0.80 ≤ D nt ≤ 1.40 mm and 2.56 ≤ D 3 ≤ 6.40mm, corresponding to 3.34 ≤ Ar Within ≤ 40.96), k 1- k 6 and nozzle diameter ( D nt ) and mixing chamber diameter ( D 3) Relationship, such as Figure 5 As shown.

[0051] Through data regression and parameter identification, we can obtain the following: k 1- k 6 and D nt and Ar The relational expression (57), where R 2 All are greater than 0.99.

[0052] (57) Example 2 A multi-fluid performance prediction system for an ejector under all operating conditions includes: The parameter acquisition module is configured to acquire operating parameters and ejector geometric parameters. The model building module is configured to model the critical point and recirculation point under preset conditions based on operating parameters and geometric parameters, forming a solution model for the characteristic points of ejector performance, including the critical recirculation ratio. 、 Critical back pressure and reflux back pressure; The parameter identification module is configured to identify unknown parameters in the solution model. The performance prediction module is configured to determine the value of the characteristic point under the target operating condition based on the identified unknown parameters, and calculate the recirculation ratio, outlet temperature and outlet fluid composition under the target operating condition based on the value of the characteristic point to achieve prediction.

[0053] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of one or more computer-usable storage media (including, but not limited to, disk storage, etc.) containing computer-usable program code. CD - ROM It takes the form of a computer program product implemented on (such as optical memory, etc.).

[0054] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure one One or more processes and / or boxes Figure one A device that provides the functions specified in one or more boxes.

[0055] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure one One or more processes and / or boxes Figure one The function specified in one or more boxes.

[0056] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure one One or more processes and / or boxes Figure one The steps of the function specified in one or more boxes.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art without creative effort within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for predicting the performance of a multi-fluid ejector over a full range of operating conditions, characterized by, Includes the following steps: Obtain operating parameters and ejector geometric parameters; According to the working condition parameters and the geometric parameters, under preset conditions, modeling of the critical point and the backflow point is respectively performed, forming a solving model of characteristic points of the ejector performance, the characteristic points including a critical recirculation ratio 、 Critical back pressure and backflow back pressure Modeling the critical point includes: determining the primary flow control equations from the inlet to the target cross section, the secondary flow control equations from the inlet to the target cross section, and calculating the critical recirculation ratio; The process of constructing a solution model for the characteristic points of ejector performance includes: ； ； ； in, ω * indicates the critical recycle ratio. p c* represents the critical back pressure. p cb is the backflow back pressure; x 1 -x 6. Related to inlet conditions and gas composition. k 1 -k 6 is only related to component efficiency and a defined coefficient, where: ； ； ； ； ； ； ； ； ； ； ； ； in, p s For secondary flow pressure, η s The component efficiency is used to determine the relationship between the theoretical and actual flow rates of the secondary flow. η p The component efficiency is the relationship between the theoretical flow rate and the actual flow rate of a single flow. ω The cycle ratio is... η d* The component efficiencies of the mixing chamber and diffusion chamber under critical conditions are given. η dcb For the component efficiency of the mixing chamber and diffusion chamber under reflux conditions, d for A d and A nt The ratio, A d The area at the outlet section. p p For primary flow pressure, k p The adiabatic index of the primary flow is... A nt Let t be the area at the nozzle throat. T p The primary inlet temperature, η pm It means A ' pm and A pm The component efficiency in relation to each other R g_p The gas constant for the primary flow is... T s This refers to the secondary inlet temperature. k s The adiabatic index of the secondary flow. R g_s The gas constant for secondary flow. A pm It is the ideal effective flow area at the target cross-section for a single flow. V pm It is the velocity of the flow at the target cross-section. V sm It is the velocity of the secondary flow at the target cross-section. p m The pressure at section mm is [value missing], and the secondary flow is blocked at section mm. A' pm It is the actual effective flow area of ​​the primary flow at the target cross-section; A 3 represents the cross-sectional area at the constant diameter section of the mixing chamber, and the coefficient is... m The critical point and the reflux point are different, and are defined as follows: m* and mcb ; Parameter identification is performed on the unknown parameters in the solution model; Based on the identified unknown parameters, the values ​​of characteristic points under the target operating conditions are determined. Based on the values ​​of the characteristic points, the recirculation ratio, outlet temperature, and outlet fluid composition under the target operating conditions are calculated to achieve prediction.

2. The multi-fluid performance prediction method for an ejector under all operating conditions as described in claim 1, characterized in that, The process of obtaining operating parameters and ejector geometric parameters includes: operating parameters include: primary flow pressure, secondary flow pressure, primary flow inlet temperature, secondary flow inlet temperature, and secondary flow fluid composition; The geometric parameters of the ejector include: nozzle throat area and mixing chamber area.

3. The multi-fluid performance prediction method for an ejector under all operating conditions as described in claim 1, characterized in that, The preset conditions include: The flow inside the ejector is a one-dimensional adiabatic steady-state flow; The working medium is considered to be an ideal gas; Neglecting the kinetic energy of the fluid at the ejector inlet and outlet; The primary flow is blocked in front of the target section, and the secondary flow is blocked at the target section, that is, the Mach number of the secondary flow at that section is 1; At the target cross-section, the two fluid streams begin to mix, and the pressure of the two streams at the target cross-section is equal to the pressure of the secondary stream.

4. The multi-fluid performance prediction method for an ejector under all operating conditions as described in claim 1, characterized in that, The primary flow control equations from the inlet to the target cross-section are: Pressure of the primary flow at the target cross section p pm 、 temperature T pm They are respectively: ； ； ； ； ； in, M a pt Let t be the Mach number of the primary flow at the nozzle throat. M a pm It is the Mach number of the primary flow at the target cross section.

5. The multi-fluid performance prediction method for an ejector under all operating conditions as described in claim 4, characterized in that, The governing equation for the secondary flow from the inlet to the target cross-section is: the temperature of the secondary flow at the target cross-section. T sm Effective circulation area A sm They are respectively: ； ； ； in, M a sm It is the Mach number of the secondary flow at the target cross-section. A' m It is the area of ​​the target cross-section, determined by a defined coefficient. m , A' m Represented as: 。 6. The multi-fluid performance prediction method for an ejector under all operating conditions as described in claim 1, characterized in that, The solution model satisfies the following constraint: the subcritical recirculation ratio is approximated as the back pressure p. c The quadratic function, the axis of symmetry of the quadratic function is the critical back pressure. p c* Furthermore, the peak value of the quadratic function is the critical recurrence ratio. ω * ; In the process of parameter identification of the unknown parameters in the solution model, the least squares method is used to identify the unknown parameters in the solution model.

7. The multi-fluid performance prediction method for an ejector under all operating conditions as described in claim 1, characterized in that, Calculate the recirculation ratio under the target operating condition ω for: ； in, p c* For critical back pressure, p c For back pressure, the coordinates of the reflux point are ( p cb ,0); 。 8. A multi-fluid performance prediction system for an ejector under all operating conditions, characterized in that, include: The parameter acquisition module is configured to acquire operating parameters and ejector geometric parameters. The model building module is configured to model the critical point and recirculation point under preset conditions based on operating parameters and geometric parameters, forming a solution model for the characteristic points of ejector performance, including the critical recirculation ratio. 、 Critical back pressure and reflux back pressure; Modeling the critical point includes: determining the primary flow control equations from the inlet to the target cross section, the secondary flow control equations from the inlet to the target cross section, and calculating the critical recirculation ratio; The process of constructing a solution model for the characteristic points of ejector performance includes: ； ； ； in, ω * indicates the critical recycle ratio. p c* represents the critical back pressure. p cb is the backflow back pressure; x 1 -x 6. Related to inlet conditions and gas composition. k 1 -k 6 is only related to component efficiency and a defined coefficient, where: ； ； ； ； ； ； ； ； ； ； ； ； in, p s For secondary flow pressure, η s The component efficiency is used to determine the relationship between the theoretical and actual flow rates of the secondary flow. η p The component efficiency is the relationship between the theoretical flow rate and the actual flow rate of a single flow. ω The cycle ratio is... η d* The component efficiencies of the mixing chamber and diffusion chamber under critical conditions are given. η dcb For the component efficiency of the mixing chamber and diffusion chamber under reflux conditions, d for A d and A nt The ratio, A d The area at the outlet section. p p For primary flow pressure, k p The adiabatic index of the primary flow is... A nt Let t be the area at the nozzle throat. T p The primary inlet temperature, η pm It means A ' pm and A pm The component efficiency in relation to each other R g_p The gas constant for the primary flow is... T s This refers to the secondary inlet temperature. k s The adiabatic index of the secondary flow. R g_s The gas constant for secondary flow. A pm It is the ideal effective flow area at the target cross-section for a single flow. V pm It is the velocity of the flow at the target cross-section. V sm It is the velocity of the secondary flow at the target cross-section. p m The pressure at section mm is [value missing], and the secondary flow is blocked at section mm. A' pm It is the actual effective flow area of ​​the primary flow at the target cross-section; A 3 represents the cross-sectional area at the constant diameter section of the mixing chamber, and the coefficient is... m The critical point and the reflux point are different, and are defined as follows: m* and mcb ; The parameter identification module is configured to identify unknown parameters in the solution model. The performance prediction module is configured to determine the value of the characteristic point under the target operating condition based on the identified unknown parameters, and calculate the recirculation ratio, outlet temperature and outlet fluid composition under the target operating condition based on the value of the characteristic point to achieve prediction.

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