Method, device and medium for calculating operating back pressure range of ejector

Abstract

This application discloses a method, device, and medium for calculating the back pressure range of an ejector operation, relating to the field of ejector operation optimization technology. The method includes: under actual operating conditions, analyzing the ejector coefficient variation curve with different outlet back pressures, and determining the outlet back pressure corresponding to the inflection point where the curve transitions from a plateau segment to a descending segment as the upper critical back pressure; inputting the ratio of working steam pressure to ejector steam pressure, the ratio of nozzle throat area to mixing chamber cross-sectional area, and the stable ejector coefficient into a pre-constructed operating back pressure range coefficient calculation model, and outputting the operating back pressure range coefficient; calculating the lower critical back pressure based on the operating back pressure range coefficient, ejector steam pressure, and upper critical back pressure; and determining the ejector's operating back pressure range based on the upper and lower critical back pressures; thereby defining the back pressure range for stable and efficient ejector operation and achieving rapid determination and prediction of the operating back pressure range under different operating conditions.

Description

Technical Field

[0001] This application relates to the field of ejector operation optimization technology, and in particular to a method, device and medium for calculating the back pressure range of ejector operation. Background Technology

[0002] An ejector is a fluid device that uses a high-energy working fluid to eject a low-energy entrained fluid, achieving mixing and pressurization. It is widely used in systems such as combined heat and power (CHP), waste heat recovery, and refrigeration. In engineering applications, ejector performance is highly sensitive to outlet back pressure. Current technology typically uses the critical back pressure as the operating criterion, assuming that the ejector maintains good performance when the outlet back pressure is below the critical back pressure. However, the critical operating range is usually quite wide. Even when the ejector operates below the critical back pressure, under varying operating conditions, issues such as decreased pressurization performance or deteriorated operating efficiency may still occur. This is because the critical back pressure mainly reflects the boundary between critical and subcritical operating conditions, and it is difficult to further characterize the changes in flow structure and differences in pressurization capacity within the critical operating range. In fact, the internal pressurization process of the ejector is usually completed by the combined action of shock wave compression and diffuser diffusion. Specifically, the fluid first achieves pressure increase through the shock wave structure, and then further converts kinetic energy into pressure energy in the diffuser. When the shock wave enters the diffuser, it can easily disrupt the internal flow state of the diffuser, resulting in a decrease in diffusion capacity, which in turn affects the pressurization performance and operational stability of the ejector.

[0003] Therefore, existing technologies only use the critical back pressure as the performance boundary and do not consider the relative relationship between the shock train position and the boundaries of the mixing and diffuser chambers as operational criteria. Consequently, it is difficult to further determine the target back pressure range that is more conducive to the stable and efficient operation of the ejector within a wider critical operating range. In addition, existing technologies rely heavily on condition-by-condition testing or numerical simulation analysis to determine the operating range, which suffers from problems such as large computational load, high calibration costs, and low efficiency in engineering applications. Therefore, it is difficult to achieve rapid calculation and prediction of the operating back pressure range under different operating conditions. Summary of the Invention

[0004] The purpose of this application is to provide a method, device, and medium for calculating the back pressure range of an ejector, so as to solve the problem in the prior art that it is difficult to quickly predict the back pressure range under different operating conditions.

[0005] To achieve the above objectives, this application provides the following solution: Firstly, this application provides a method for calculating the back pressure range of an ejector operation, including: Obtain the actual operating condition parameters and structural parameters of the ejector, wherein the actual operating condition parameters include the working steam pressure and the ejector steam pressure, and the structural parameters include the nozzle throat area and the mixing chamber cross-sectional area; Under the actual operating conditions, by analyzing the ejector coefficient variation curve of the ejector with different outlet back pressures, the outlet back pressure corresponding to the turning point of the variation curve from the plateau segment to the descending segment is determined as the upper critical back pressure, and the stable ejector coefficient corresponding to the actual operating conditions is determined. The ratio of the working steam pressure to the ejector steam pressure, the ratio of the nozzle throat area to the mixing chamber cross-sectional area, and the stable ejector coefficient are input into a pre-constructed operating back pressure range coefficient calculation model, and the operating back pressure range coefficient is output. The lower critical back pressure is calculated based on the operating back pressure range coefficient, the upper critical back pressure, and the ejector steam pressure, and the operating back pressure range of the ejector is determined based on the upper critical back pressure and the lower critical back pressure.

[0006] In one embodiment, the expression for the calculation model of the operating back pressure range coefficient is: ; in, The working steam pressure is... The ejector steam pressure is... The area of ​​the nozzle throat is [area]. The cross-sectional area of ​​the mixing chamber is... The stable entrainment coefficient is... This is the range coefficient for the operating back pressure interval.

[0007] In one embodiment, the step of calculating the lower critical back pressure based on the operating back pressure range coefficient, the upper critical back pressure, and the ejector steam pressure, and determining the operating back pressure range of the ejector based on the upper critical back pressure and the lower critical back pressure, is expressed as follows: ; ; in, This refers to the upper critical back pressure. For the operating back pressure range, For the operating back pressure range, The ejector steam pressure is... This is the range coefficient for the operating back pressure interval.

[0008] In one embodiment, in the calculation model for the operating back pressure range coefficient, the applicable range of the working steam pressure satisfies: 7 MPa < <20 MPa; In the calculation model for the operating back pressure range coefficient, the applicable range of the ejector steam pressure satisfies: 1.5MPa < <5 MPa; In the calculation model for the operating back pressure range coefficient, the applicable range of the stable ejection coefficient satisfies: 0.52 < <2.16.

[0009] In one embodiment, the step of constructing and running a back pressure range coefficient calculation model specifically includes: Under different sample operating conditions, the upper critical back pressure and lower critical back pressure of the sample corresponding to each sample operating condition parameter are obtained to determine the sample operating back pressure range, and the sample operating back pressure range range coefficient is determined based on the sample operating back pressure range; wherein, the sample operating conditions parameters include the sample working steam pressure and the sample ejector steam pressure; Using the ratio of the sample working steam pressure to the sample ejector steam pressure, the ratio of the nozzle throat area to the mixing chamber cross-sectional area, and the sample stable ejection coefficient as independent variables, and the sample operating back pressure range coefficient as the dependent variable, a multiple linear regression fitting using the least squares method is performed to obtain the calculation model for the operating back pressure range coefficient.

[0010] In one embodiment, the step of obtaining the critical back pressure corresponding to each sample's operating condition parameter specifically includes: Under each of the sample operating condition parameters: Acquire flow field data of the ejector under multiple different outlet back pressure conditions; Pressure distribution data along the ejector axis is extracted from each flow field data, and shock trains inside the ejector are identified based on the pressure distribution data to determine the end position of the shock trains. The relative positions of the end positions of each shock train and the outlet cross-section of the ejector mixing chamber are compared to determine whether the end position of the shock train is located upstream of the outlet cross-section of the mixing chamber. From the multiple outlet back pressures that satisfy the condition that the end position of the shock train is located upstream of the outlet cross-section of the mixing chamber, the outlet back pressure with the smallest value is selected as the sample lower critical back pressure.

[0011] In one embodiment, the step of acquiring flow field data of the ejector under multiple different outlet back pressure conditions specifically includes: A numerical calculation model of the ejector is constructed, which includes a two-dimensional axisymmetric geometric model based on the structural parameters of the ejector, and a set of basic governing equations based on the internal flow of the ejector. Based on the established numerical calculation model, keeping the sample operating parameters unchanged, the internal flow of the ejector under multiple different outlet back pressure conditions is calculated sequentially using numerical simulation methods to obtain flow field data corresponding to each outlet back pressure.

[0012] In one embodiment, the step of identifying the shock train inside the ejector based on the pressure distribution data to determine the end position of the shock train specifically includes: Identify pressure jump zones from the pressure distribution data; A first pressure value and a second pressure value are selected in the pressure stabilization regions on both sides of the pressure jump section, respectively. Calculate the pressure jump intensity based on the first pressure value and the second pressure value; When the pressure jump intensity is greater than a preset intensity threshold, the pressure jump segment is determined to be the segment corresponding to the shock train, and the end position of the shock train is determined.

[0013] Secondly, this application also provides a computer device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the above-described method.

[0014] Thirdly, this application also provides a computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the above-described method.

[0015] According to the specific embodiments provided in this application, the following technical effects are disclosed: This application inputs the ratio of working steam pressure to ejector steam pressure, the ratio of nozzle throat area to mixing chamber cross-sectional area, and stable ejector coefficient into a pre-constructed operating back pressure range coefficient calculation model, outputting the operating back pressure range coefficient. Based on the operating back pressure range coefficient, the upper critical back pressure, and the ejector steam pressure, the lower critical back pressure is calculated, and the operating back pressure range of the ejector is determined based on the upper and lower critical back pressures. The upper critical back pressure and stable ejector coefficient are determined by analyzing the ejector coefficient variation curve with different outlet back pressures under actual operating conditions. Thus, this application further defines a back pressure range more conducive to efficient ejector operation on the basis of a relatively wide critical operating range, realizing rapid calculation and prediction of the operating back pressure range under different operating conditions. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1A flowchart illustrating a method for calculating the back pressure range of an ejector operation according to an embodiment of this application; Figure 2 A schematic diagram of the ejector structure for calculating the back pressure range of the ejector operation according to an embodiment of this application; Figure 3 This is a schematic diagram showing the relationship between the ejector coefficient and the outlet back pressure in a method for calculating the back pressure range of the ejector operation according to an embodiment of this application. Figure 4 A schematic diagram of the computational domain for numerical simulation of an ejector, illustrating a method for calculating the back pressure range of an ejector in accordance with an embodiment of this application. Figure 5 The diagram shows the axial pressure distribution under different outlet back pressure conditions, which is a calculation method for the ejector operating back pressure range according to an embodiment of this application. Figure 6 This is a schematic diagram showing the relative relationship between the shock train position and the mixing chamber and diffuser chamber in the calculation method of the ejector operating back pressure range according to an embodiment of this application. Figure 7 This is a schematic diagram of the structure of a computer device provided in an embodiment of this application.

[0018] Figure label: 1-Adjusting cone, 2-Nozzle, 3-Nozzle throat, S-Shock train, a-Absorption chamber, b-Mixing chamber, c-Diffuser chamber. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] See Figure 1 This application provides a method for calculating the back pressure range of an ejector operation, comprising the following steps: S100: Obtain the actual operating condition parameters and structural parameters of the ejector. The actual operating condition parameters include the working steam pressure and the ejector steam pressure, and the structural parameters include the nozzle throat area and the mixing chamber cross-sectional area. S200: Under actual operating conditions, by analyzing the change curve of the ejector coefficient with different outlet back pressures, the outlet back pressure corresponding to the turning point of the change curve from the plateau section to the descending section is determined as the upper critical back pressure, and the stable ejector coefficient corresponding to the actual operating conditions is determined. S300: Input the ratio of working steam pressure to ejector steam pressure, the ratio of nozzle throat area to mixing chamber cross-sectional area, and stable ejector coefficient into the pre-built operating back pressure range coefficient calculation model, and output the operating back pressure range coefficient. S400: Calculate the lower critical back pressure based on the operating back pressure range coefficient, the upper critical back pressure, and the ejector steam pressure, and determine the operating back pressure range of the ejector based on the upper critical back pressure and the lower critical back pressure.

[0022] In S100, see Figure 2 Actual operating condition parameters refer to the working conditions of the ejector during operation, including the working steam pressure and the ejector steam pressure, used to describe the inlet state of the fluid. The working steam pressure is the high-energy fluid pressure at the ejector's working fluid inlet, and the ejector steam pressure is the low-energy fluid pressure at the ejector's ejector fluid inlet. Structural parameters refer to the ejector's own geometric dimensions, including the nozzle throat area and the mixing chamber cross-sectional area, used to describe the structural characteristics of the internal flow channels.

[0023] See S200. Figure 3 By continuously increasing the outlet back pressure while keeping the actual operating parameters constant, the relationship between the ejector coefficient and the outlet back pressure is obtained. When the outlet back pressure increases to the point where the ejector coefficient changes from essentially not changing with the outlet back pressure to decreasing with increasing outlet back pressure, i.e., when the ejector changes from a critical operating state to a subcritical operating state, the corresponding outlet back pressure is determined as the upper critical back pressure. p CBP This is the outlet back pressure value when the ejector transitions from a critical operating state to a subcritical operating state.

[0024] For example, the ejector coefficient can be calculated as follows: Under actual operating conditions, obtain the mass flow rate of the ejected fluid and the mass flow rate of the working fluid corresponding to any outlet back pressure; calculate the ratio of the mass flow rate of the ejected fluid to the mass flow rate of the working fluid to obtain the ejector coefficient.

[0025] In one embodiment, to improve the stability and repeatability of the upper critical back pressure determination, the turning point where the ejector coefficient curve changes from basically constant to starting to decline can be determined by a piecewise fitting method. Specifically, this includes: sorting each outlet back pressure in ascending order to obtain a back pressure sequence and a corresponding ejector coefficient sequence; based on the back pressure sequence and the ejector coefficient sequence, performing two-segment piecewise fitting on the ejector coefficient curve, where the first segment represents the plateau segment of the critical working region, and the second segment represents the declining segment of the subcritical working region; the outlet back pressure value corresponding to the intersection of the first and second fitted lines is used as a candidate turning point; and the outlet back pressure value corresponding to the candidate turning point is determined as the upper critical back pressure. .

[0026] In the above implementation, the absolute value of the slope of the first fitted line is less than the preset plateau slope threshold, and the slope of the second fitted line is less than the preset descent slope threshold, so as to distinguish between the plateau segment and the descent segment.

[0027] In one exemplary implementation, the least squares method can be used to perform linear fitting on the two data segments respectively, and the minimum sum of the fitting residuals of the two segments can be used as the criterion for selecting the segment position.

[0028] In another embodiment, the upper critical back pressure It can be determined using the differential slope threshold method, specifically by sorting the back pressures at each outlet in ascending order of value to obtain the back pressure sequence. } and the corresponding entrainment coefficient sequence { }; Calculate the difference slope between adjacent sampling points ,in: ; Determine if the differential slope meets the preset descent condition: When the differential slope is less than the preset slope threshold for multiple consecutive sampling intervals, determine if the curve of the ejector coefficient changing with the outlet back pressure enters the descent segment from the plateau segment; the outlet back pressure value corresponding to the first time the continuous descent condition is met is determined as the upper critical back pressure. .

[0029] In the above implementation, the number of consecutive sampling intervals can be set according to the number of sampling points and the data noise level to reduce the impact of local fluctuations on the inflection point identification results.

[0030] In summary, this application improves the stability, repeatability, and programmable implementation capability of the upper critical back pressure identification results by quantifying the inflection point of the curve of the ejection coefficient changing with the outlet back pressure (e.g., using a piecewise fitting method or a differential slope threshold method).

[0031] It should be noted that the stable entrainment coefficient is the average of the entrainment coefficients at multiple sampling points in the plateau segment of the entrainment coefficient-exit backpressure curve. See [link to relevant documentation]. Figure 3 The average value of the ejector coefficient corresponding to the platform segment in the figure reflects the maximum ejection capability that the ejector can achieve under the current operating conditions.

[0032] In S300, the ratio of working steam pressure to ejector steam pressure, the ratio of nozzle throat area to mixing chamber cross-sectional area, and the stable ejector coefficient are obtained, and the operating back pressure range coefficient is calculated based on the above parameters. Specifically, in this embodiment, The back pressure range coefficient can be calculated using a pre-established fitting model, namely, the back pressure range calculation model. The fitting model is constructed based on sample back pressure range data determined under multiple sample operating conditions. The sample lower critical back pressure in the sample back pressure range data is determined according to the position criterion that the shock train is completely located in the mixing chamber, and is used to realize the rapid calculation of the operating back pressure range under different operating conditions.

[0033] In one exemplary embodiment, the back pressure range coefficient is operated. The calculation formula is: ; in, For working steam pressure, For the ejector steam pressure, This represents the area of ​​the nozzle throat. The cross-sectional area of ​​the mixing chamber is... To stabilize the entrainment coefficient, This is the back pressure range coefficient for operation. Wherein, and The unit is pressure. and The unit is area.

[0034] In S400, based on the operating back pressure range coefficient With ejector steam pressure p s Calculate the operating back pressure range Based on the operating back pressure range and upper critical back pressure Calculate the lower critical back pressure, and determine the operating back pressure range of the ejector based on the lower and upper critical back pressures. Specifically, in one exemplary embodiment, based on the operating back pressure range coefficient... With ejector steam pressure p s Calculate the operating back pressure range The steps and calculation formula are as follows: ; Based on the operating back pressure range and upper critical back pressure Calculate the lower critical back pressure, and determine the operating back pressure range of the ejector based on the lower and upper critical back pressures. Therefore, the operating back pressure range is defined as: ; in, This is the upper critical back pressure. To operate within the back pressure range, For the operating back pressure range, The calculation result is the lower critical back pressure. Through the above calculation, the back pressure range for stable and efficient operation of the ejector can be quickly obtained under given operating and structural parameters.

[0035] In some implementations, the applicable range of the operating steam pressure in the back pressure range coefficient calculation model satisfies: 7 MPa < <20 MPa; In the calculation model for the operating back pressure range coefficient, the applicable range of the ejector steam pressure satisfies: 1.5 MPa < <5 MPa; In the calculation model of the back pressure range coefficient, the applicable range of the stable ejection coefficient satisfies: 0.52 < <2.16. Within the above applicable scope, this fitting model can be used for rapid estimation of back pressure ranges and preset of operating parameters. In practical engineering applications, the calculation results can also be corrected by combining real-time measurement data or calibration data.

[0036] Ultimately, the closed interval defined by the lower critical back pressure as the lower limit and the upper critical back pressure as the upper limit is determined as the operating back pressure range of the ejector. Within this range, the shock train is entirely located within the mixing chamber and does not enter the diffuser chamber, resulting in good ejector stability and suitability for operation and control. See also Figure 3 As the outlet back pressure continues to increase, the ejector coefficient decreases further and approaches zero. Numerical simulation results show that the ejector fluid exhibits a backflow trend, and the ejector enters a reflux working state. This state is used to describe the upper limit of the ejector's operating range, but it is not used as a criterion for the upper critical back pressure in this embodiment.

[0037] In this embodiment of the application, the step of constructing the calculation model for the operating back pressure range coefficient specifically includes: obtaining the upper critical back pressure and lower critical back pressure of the sample corresponding to each sample operating condition parameter under different sample operating condition parameters, so as to determine the sample operating back pressure range, and determining the sample operating back pressure range coefficient based on the sample operating back pressure range; wherein, the sample operating condition parameters include the sample working steam pressure and the sample ejector steam pressure; using the ratio of the sample working steam pressure to the sample ejector steam pressure, the ratio of the nozzle throat area to the mixing chamber cross-sectional area, and the sample stable ejector coefficient as independent variables, and the sample operating back pressure range coefficient as the dependent variable, a multiple linear regression fitting is performed using the least squares method to obtain the calculation model for the operating back pressure range coefficient.

[0038] The determination coefficient of the back pressure range coefficient calculation model in this application reaches 0.9946, the correlation coefficient is 0.9918, the root mean square error is 0.00793, and the mean absolute percentage error is 1.34%, indicating that the model has high fitting accuracy to the sample data and can meet the needs of rapid calculation of the back pressure range in engineering applications.

[0039] The method for obtaining the upper critical back pressure of any sample operating condition parameter is the same as the method for determining the upper critical back pressure of the actual operating condition parameter, so it will not be repeated here.

[0040] Specifically, the steps for obtaining the sample-level critical back pressure under each sample's operating conditions include: under each sample's operating conditions: acquiring flow field data of the ejector under multiple different outlet back pressure conditions; extracting pressure distribution data along the ejector axis from each flow field data, and identifying shock trains inside the ejector based on the pressure distribution data to determine the end position of the shock trains; comparing the relative position of the end position of each shock train with the outlet cross-section of the ejector mixing chamber to determine whether the end position of the shock train is located upstream of the outlet cross-section of the mixing chamber, and selecting the outlet back pressure with the smallest value from among multiple outlet back pressures that satisfy the condition that the end position of the shock train is located upstream of the outlet cross-section of the mixing chamber as the sample-level critical back pressure. The sample-level critical back pressure is defined as: under given sample operating conditions, the outlet back pressure with the smallest value among all outlet back pressures that can keep the end position of the shock train upstream of the outlet cross-section of the mixing chamber.

[0041] Under specific sample operating parameters, the shock train termination positions corresponding to multiple different outlet backpressure conditions were obtained, and the relative positions of each shock train termination position and the mixing chamber outlet section were compared. When the axial coordinate of the shock train termination position is less than the axial coordinate of the mixing chamber outlet section, the outlet backpressure is determined to satisfy the condition that the shock train termination position is upstream of the mixing chamber outlet section; when the axial coordinate of the shock train termination position is greater than or equal to the axial coordinate of the mixing chamber outlet section, the outlet backpressure is determined not to satisfy the condition. Among all outlet backpressures that satisfy the condition, the outlet backpressure with the smallest value is selected as the sample lower critical backpressure. Thus, the sample lower critical backpressure characterizes the lower backpressure boundary when the shock train termination position just does not enter the diffuser. When the actual operating outlet backpressure is greater than or equal to the sample lower critical backpressure, the shock train termination position remains upstream of the mixing chamber outlet section; when the actual operating outlet backpressure is lower than the sample lower critical backpressure, the shock train termination position will cross the mixing chamber outlet section and enter the diffuser, thereby weakening the pressure boosting effect of the diffuser and affecting the ejector's operational stability.

[0042] Under a specific numerical simulation condition corresponding to the lower critical back pressure, the shock train structure inside the ejector remains stable, and its starting and ending positions do not shift significantly with changes in the outlet back pressure, indicating good anti-disturbance capability. This internal flow characteristic can serve as an auxiliary basis for determining the lower critical back pressure.

[0043] The steps for obtaining flow field data of the ejector under multiple different outlet back pressure conditions specifically include: constructing a numerical calculation model of the ejector, which includes a two-dimensional axisymmetric geometric model constructed based on the structural parameters of the ejector, and a set of basic governing equations constructed based on the internal flow of the ejector; based on the constructed numerical calculation model, keeping the sample operating condition parameters unchanged, using numerical simulation methods to calculate the internal flow of the ejector under multiple different outlet back pressure conditions in sequence, and obtaining flow field data corresponding to each outlet back pressure.

[0044] See Figure 2 Taking a steam ejector as the research object, the ejector includes structures such as an adjusting cone 1, a working nozzle 2, a nozzle throat 3, an absorption chamber a, a mixing chamber b, and a diffuser c. In this application, a two-dimensional axisymmetric geometric model is established based on the structural parameters of the ejector. That is, based on the rotational symmetry characteristics of the ejector, its three-dimensional solid structure is simplified into a two-dimensional cross-section through the central axis.

[0045] In this embodiment, the flow inside the ejector is assumed to be steady-state, compressible turbulent flow, neglecting the effects of gravity and phase transition. Mass conservation, momentum conservation, and energy conservation equations are established as the basic governing equations, and a shear stress transfer (SST k-ω) turbulence model is used to enclose the turbulence effects. Thus, based on the fundamental physical laws of fluid mechanics, a set of governing equations describing the flow is established, and the shear stress transfer turbulence model is selected to characterize the turbulence, completing the numerical modeling and solution of the compressible turbulent flow inside the ejector.

[0046] This step also includes mesh generation and solution setup: a structured mesh is generated for the two-dimensional axisymmetric geometric model, with local refinement in areas such as the nozzle exit, mixing chamber, and diffuser inlet. The final computational mesh is determined through mesh independence verification; for example, the mesh density is gradually increased for multiple trial calculations until key results no longer change significantly with further mesh refinement. The mesh selected at this point is the final computational mesh. During the numerical simulation, both the working fluid inlet and the ejected fluid inlet are set as pressure inlet boundary conditions, the ejector outlet is set as a pressure outlet boundary condition, and the ejector wall is set as a no-slip adiabatic boundary condition. Specifically, the numerical solution uses the finite volume method, the convection term uses a second-order upwind scheme, and the calculation is considered convergent when the residuals of each governing equation are less than a preset threshold.

[0047] While keeping the sample's operating parameters constant, the ejector outlet back pressure is gradually changed, and numerical simulations are performed for different outlet back pressure conditions to obtain the flow field data under the corresponding conditions. The sample's operating parameters may include the working steam pressure and ejector steam pressure, and may also include, depending on the actual situation, the working fluid inlet temperature, ejector fluid inlet temperature, and working fluid mass flow rate.

[0048] The step of identifying the shock train S inside the ejector based on pressure distribution data to determine the end position of the shock train specifically includes: identifying a pressure jump segment from the pressure distribution data; selecting a first pressure value and a second pressure value in the pressure stable regions on both sides of the pressure jump segment; calculating the pressure jump intensity based on the first pressure value and the second pressure value; and determining the pressure jump segment as the corresponding segment of the shock train and determining the end position of the shock train when the pressure jump intensity is greater than a preset intensity threshold.

[0049] See Figure 4 and Figure 5Pressure distribution data along the ejector axis is extracted from the flow field data. A one-dimensional sampling line is set along the central symmetry axis (i.e., the geometric center line from the inlet to the outlet) within the computational domain. Then, the static pressure value corresponding to each coordinate point on this sampling line is directly read from the flow field data. Thus, the pressure values ​​arranged along the axial direction constitute an axial pressure distribution curve that can intuitively reflect the internal flow characteristics. Furthermore, by analyzing the pressure jump regions on this axial pressure distribution curve, key components such as shock waves can be located.

[0050] See Figure 6 Locate the section on the axial pressure distribution curve where the pressure suddenly and significantly increases; this is likely the region where the shock wave train is located. In the stable pressure region upstream of this pressure jump area, select a stable pressure value, denoted as [value missing]. In the stable pressure region downstream of the pressure jump region, a stable pressure value is selected and denoted as . The pressure jump intensity is calculated based on the first and second pressure values, using the following formula: ; In the formula, For the intensity of the pressure jump, The first pressure value, This is the second pressure value. The pressure jump intensity is used to distinguish between a real shock train and ordinary flow fluctuations. Only when the calculated pressure jump intensity is greater than a preset intensity threshold can a valid shock train be determined to exist, ensuring that the observed pressure jump is not an ordinary flow fluctuation or noise interference.

[0051] Furthermore, the starting and ending positions of the shock wave train can be determined based on the axial pressure distribution curve. The coordinates of the point where the pressure first begins to rise sharply can be defined as the starting position, and the coordinates of the point where the pressure returns to a stable change can be defined as the ending position.

[0052] It should be noted that when multiple pressure jump segments that meet the intensity threshold are identified, the shock train corresponding to the pressure jump segment whose end position is closest to the ejector outlet is selected as the judgment criterion.

[0053] In summary, based on the collected sample dataset, a multivariate linear regression fitting using the least squares method was employed to obtain a calculation model for the operating backpressure range coefficient. This model takes the actual operating conditions, structural parameters, and stable ejection coefficients as inputs to directly calculate the corresponding operating backpressure range coefficient. This simplifies the complex physical process of determining the critical backpressure based on the shock train position criterion, avoiding condition-by-condition testing or numerical simulation analysis, and enabling rapid and accurate prediction of the operating backpressure range under different operating conditions.

[0054] Compared with existing technologies, this application not only uses the characteristics of ejector coefficient variation to determine the upper boundary of operation, but also uses the shock train position criterion to determine the lower boundary of operation, thereby more accurately defining the back pressure range for stable and efficient operation of the ejector, and realizing rapid calculation and prediction of the back pressure range under different operating conditions.

[0055] In one exemplary embodiment, a computer device is provided, which may be a server or a terminal, and its internal structure diagram may be as follows. Figure 7 As shown, this computer device includes a processor, memory, input / output (I / O) interfaces, and a communication interface. The processor, memory, and I / O interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the I / O interfaces. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and databases. The internal memory provides the environment for the operating system and computer programs stored in the non-volatile storage media to run. The I / O interfaces are used for exchanging information between the processor and external devices. The communication interface is used for communicating with external terminals via a network connection.

[0056] Those skilled in the art will understand that Figure 7 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0057] In one exemplary embodiment, a computer device is also provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above-described method embodiments.

[0058] In one exemplary embodiment, a computer-readable storage medium is provided storing a computer program that, when executed by a processor, implements the steps in the above-described method embodiments.

[0059] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0060] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM).

[0061] The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0062] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0063] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for calculating the back pressure range of an ejector operation, characterized in that, include: Obtain the actual operating condition parameters and structural parameters of the ejector, wherein the actual operating condition parameters include the working steam pressure and the ejector steam pressure, and the structural parameters include the nozzle throat area and the mixing chamber cross-sectional area; Under the actual operating conditions, by analyzing the ejector coefficient variation curve of the ejector with different outlet back pressures, the outlet back pressure corresponding to the turning point of the variation curve from the plateau segment to the descending segment is determined as the upper critical back pressure, and the stable ejector coefficient corresponding to the actual operating conditions is determined. The ratio of the working steam pressure to the ejector steam pressure, the ratio of the nozzle throat area to the mixing chamber cross-sectional area, and the stable ejector coefficient are input into a pre-constructed operating back pressure range coefficient calculation model, and the operating back pressure range coefficient is output. The lower critical back pressure is calculated based on the operating back pressure range coefficient, the upper critical back pressure, and the ejector steam pressure, and the operating back pressure range of the ejector is determined based on the upper critical back pressure and the lower critical back pressure.

2. The method for calculating the back pressure range of the ejector operation according to claim 1, characterized in that, The expression for the calculation model of the operating back pressure range coefficient is as follows: ； in, The working steam pressure is... The ejector steam pressure is... The area of ​​the nozzle throat is [area]. The cross-sectional area of ​​the mixing chamber is... The stable entrainment coefficient is... This is the range coefficient for the operating back pressure interval.

3. The method for calculating the back pressure range of the ejector operation according to claim 2, characterized in that, The step of calculating the lower critical back pressure based on the operating back pressure range coefficient, the upper critical back pressure, and the ejector steam pressure, and determining the operating back pressure range of the ejector based on the upper critical back pressure and the lower critical back pressure, is expressed as follows: ； ； in, This refers to the upper critical back pressure. For the operating back pressure range, For the operating back pressure range, The ejector steam pressure is... This is the range coefficient for the operating back pressure interval.

4. The method for calculating the back pressure range of the ejector operation according to claim 2, characterized in that, In the calculation model for the operating back pressure range coefficient, the applicable range of the working steam pressure satisfies: 7 MPa < <20 MPa; In the calculation model for the operating back pressure range coefficient, the applicable range of the ejector steam pressure satisfies: 1.5 MPa < <5 MPa; In the calculation model for the operating back pressure range coefficient, the applicable range of the stable ejection coefficient satisfies: 0.52 < <2.

16.

5. The method for calculating the back pressure range of the ejector operation according to claim 1, characterized in that, The steps for constructing and running the back pressure range coefficient calculation model specifically include: Under different sample operating conditions, the upper critical back pressure and lower critical back pressure of the sample corresponding to each sample operating condition parameter are obtained to determine the sample operating back pressure range, and the sample operating back pressure range range coefficient is determined based on the sample operating back pressure range; wherein, the sample operating conditions parameters include the sample working steam pressure and the sample ejector steam pressure; Using the ratio of the sample working steam pressure to the sample ejector steam pressure, the ratio of the nozzle throat area to the mixing chamber cross-sectional area, and the sample stable ejection coefficient as independent variables, and the sample operating back pressure range coefficient as the dependent variable, a multiple linear regression fitting using the least squares method is performed to obtain the calculation model for the operating back pressure range coefficient.

6. The method for calculating the back pressure range of the ejector operation according to claim 5, characterized in that, The steps for obtaining the critical back pressure corresponding to the operating condition parameters of each sample specifically include: Under each of the sample operating condition parameters: Acquire flow field data of the ejector under multiple different outlet back pressure conditions; Pressure distribution data along the ejector axis is extracted from each flow field data, and shock trains inside the ejector are identified based on the pressure distribution data to determine the end position of the shock trains. The relative positions of the end positions of each shock train and the outlet cross-section of the ejector mixing chamber are compared to determine whether the end position of the shock train is located upstream of the outlet cross-section of the mixing chamber. From the multiple outlet back pressures that satisfy the condition that the end position of the shock train is located upstream of the outlet cross-section of the mixing chamber, the outlet back pressure with the smallest value is selected as the sample lower critical back pressure.

7. The method for calculating the back pressure range of the ejector operation according to claim 6, characterized in that, The step of acquiring flow field data of the ejector under multiple different outlet back pressure conditions specifically includes: A numerical calculation model of the ejector is constructed, which includes a two-dimensional axisymmetric geometric model based on the structural parameters of the ejector, and a set of basic governing equations based on the internal flow of the ejector. Based on the established numerical calculation model, keeping the sample operating parameters unchanged, the internal flow of the ejector under multiple different outlet back pressure conditions is calculated sequentially using numerical simulation methods to obtain flow field data corresponding to each outlet back pressure.

8. The method for calculating the back pressure range of the ejector operation according to claim 6, characterized in that, The step of identifying the shock train inside the ejector based on the pressure distribution data to determine the end position of the shock train specifically includes: Identify pressure jump zones from the pressure distribution data; A first pressure value and a second pressure value are selected in the pressure stabilization regions on both sides of the pressure jump section, respectively. Calculate the pressure jump intensity based on the first pressure value and the second pressure value; When the pressure jump intensity is greater than a preset intensity threshold, the pressure jump segment is determined to be the segment corresponding to the shock train, and the end position of the shock train is determined.

9. A computer device, comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor executes the computer program to implement the method for calculating the ejector operating back pressure range according to any one of claims 1-8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the method for calculating the ejector operating back pressure range as described in any one of claims 1-8.

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