One-dimensional modeling method of transcritical CO2 ejector and related device

Abstract

The invention belongs to the technical field of engineering thermophysics, and discloses a one-dimensional modeling method for a transcritical CO2 injector and a related device, and the method comprises the steps: obtaining a performance matrix of the transcritical CO2 injector; the performance matrix is used for calculating the mass flow of the mainstream fluid of the ejector and the ejection ratio of the ejector; and building a transcritical CO2 ejector one-dimensional model by using the ejector mainstream fluid mass flow and the ejector injection ratio. According to the method, high-precision dynamic characteristic calculation of the ejector system is realized, and the method has important significance on design, test and test of the transcritical CO2 ejector system.

Description

Technical Field

[0001] The present invention belongs to the technical field of engineering thermophysics, and in particular relates to a one-dimensional modeling method of a transcritical CO2 injector and a related device. Background Art

[0002] As a natural refrigerant, CO2 has excellent environmental performance and is a very potential alternative refrigerant. The transcritical CO2 cycle has therefore become a research focus and hotspot. However, due to the high operating pressure of the transcritical cycle, there is a huge throttling loss in the system, resulting in low overall efficiency of the transcritical cycle. Using an ejector instead of a throttle valve in the system can recover expansion work and increase the suction pressure of the compressor, reduce the power consumption of the compressor, and improve system performance. As a core component of the system, the working performance of the ejector plays a vital role in the system performance. However, the current one-dimensional simulation of the ejector system only stays on simple cycle calculations, and it is difficult to simulate the dynamic operating characteristics of the system. Kornhauser proposed a one-dimensional steady-state mathematical calculation model for the ejector. The model assumes multiple efficiencies of the ejector to calculate the ejector. However, the calculation accuracy of the model is low and cannot meet the high-precision calculation of the dynamic characteristics of the ejector system. The existing public literature mainly studies the fluid dynamics calculation of the three-dimensional model of the ejector, and there is little research on the high-precision one-dimensional model of the ejector. In summary, establishing a high-precision one-dimensional modeling method for transcritical CO2 injectors is of great significance to the design, experiment, test and simulation of transcritical CO2 injector systems. Summary of the invention

[0003] The purpose of the present invention is to propose a one-dimensional modeling method and related devices for a transcritical CO2 injector, so as to solve the problem that the current one-dimensional simulation of the injector system only stays at a simple cycle calculation, it is difficult to simulate the dynamic operating characteristics of the system and there is little related research on the high-precision one-dimensional model of the injector.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: A one-dimensional modeling method for a transcritical CO2 ejector, comprising: Obtain the performance matrix of transcritical CO2 injectors; The performance matrix is ​​used to calculate the ejector mainstream fluid mass flow rate and the ejector injection ratio; A one-dimensional model of the transcritical CO2 ejector is constructed using the ejector mainstream fluid mass flow rate and the ejector injection ratio.

[0005] Preferably, the performance matrix of the transcritical CO2 ejector includes: The density, pressure, enthalpy and mass flow rate at the main inlet of the ejector, the density, pressure, enthalpy and mass flow rate at the ejector inlet, the pressure and mass flow rate at the ejector outlet, and the throat diameter in the geometric structure of the ejector.

[0006] Preferably, the mass flow rate of the mainstream fluid of the injector is calculated based on the performance matrix and the physical mechanism of the transcritical CO2 injector as follows:

[0007] in, represents the density of the mainstream entrance, Represents the pressure at the main entrance, represents the throat diameter of the ejector, is the critical pressure of CO2, and A, B, C, D, and E are coefficients; wherein, the coefficients A, B, C, D, and E are calculated by fitting using the least squares method.

[0008] Preferably, the ejector injection ratio is calculated based on the performance matrix and the physical mechanism of the transcritical CO2 ejector. as follows:

[0009] in, is the mass flow rate at the jet inlet, is the mass flow rate at the main inlet of the ejector, is the density at the main inlet of the ejector, is the pressure at the main inlet of the ejector, is the pressure at the jet inlet, is the pressure at the ejector outlet, is the diffusion chamber angle, , is the coefficient, , and are functions of the flow fluid state and the ejection fluid pressure, expressed as:

[0010]

[0011] in, i Take 1, 2, 3, , , , , , is the coefficient, is the critical pressure of CO2; Ejector injection ratio The coefficients in are calculated by the least squares method.

[0012] Preferably, a one-dimensional model of a transcritical CO2 ejector is constructed using the mass flow rate of the mainstream fluid of the ejector and the ejector injection ratio, comprising the following steps: S1. Calculate the mass flow rate of the main flow fluid of the ejector according to the density at the main flow inlet of the ejector, the pressure at the main flow inlet of the ejector and the throat diameter of the ejector: S2. After obtaining the mass flow rate of the mainstream fluid of the ejector, the ejection ratio is calculated based on the pressure of the ejection flow inlet, the ejector pressure and the ejector diffusion chamber opening angle: S3. Calculate the mass flow rate of the ejection fluid and the mass flow rate of the ejector outlet according to the mass flow rate of the mainstream fluid obtained in step S1 and the ejection ratio obtained in step S2: S4. Calculate the ejector outlet enthalpy value based on the mass flow rate of the mainstream fluid obtained in step S1, the mass flow rate of the ejector fluid obtained in step S3, the mass flow rate of the ejector outlet, the mainstream inlet enthalpy value, and the ejector inlet enthalpy value: S5. Determine the ejector outlet dryness according to the ejector outlet pressure and the ejector outlet enthalpy value obtained in step S4; S6. Determine whether the ejector outlet dryness and ejection ratio meet the ejector system stability conditions: S7. When the dryness and ejection ratio at the ejector outlet do not meet the ejector system stability conditions, change the ejector outlet pressure, and then repeat S1-S6 until the dryness and ejection ratio at the ejector outlet meet the ejector system stability conditions, and obtain the mass flow rate of the ejector mainstream fluid, the mass flow rate of the ejection fluid, the ejection ratio, the ejector outlet back pressure, the outlet enthalpy value and the outlet mass flow rate.

[0013] Preferred: In step S3, the mass flow rate of the jet fluid is and the mass flow rate at the ejector outlet They are as follows:

[0014]

[0015] In step S4, the ejector outlet enthalpy as follows:

[0016] In step S5, the ejector outlet dryness as follows:

[0017] In step S6, the injector system stability condition is as follows:

[0018] in, is the mass flow rate of the mainstream fluid in the ejector, is the ejection ratio, is the ejector mainstream inlet enthalpy, is the enthalpy of the jet inlet, is the ejector outlet back pressure.

[0019] The present invention also provides a one-dimensional modeling system for a transcritical CO2 injector, which is used to implement the one-dimensional modeling method for the transcritical CO2 injector, comprising: Data acquisition unit: used to obtain the performance matrix of the transcritical CO2 injector; Calculation unit: used for calculating the mass flow rate of the mainstream fluid of the ejector and the ejector injection ratio by using the performance matrix; Modeling unit: used to build a one-dimensional model of a transcritical CO2 ejector using the ejector mainstream fluid mass flow rate and the ejector injection ratio.

[0020] The present invention also provides an electronic device, comprising: one or more processors; a storage device having one or more programs stored thereon; When the one or more programs are executed by the one or more processors, the one or more processors are enabled to implement the one-dimensional modeling method of the transcritical CO 2 injector of the present invention as described above.

[0021] The present invention further provides a storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the one-dimensional modeling method of the transcritical CO2 injector of the present invention as described above is implemented.

[0022] The present invention further provides a computer program product, which includes computer instructions, and the computer instructions instruct a computer to execute the one-dimensional modeling method of the transcritical CO2 injector of the present invention as described above.

[0023] Compared with the prior art, the present invention has the following beneficial effects: The present invention is based on the performance matrix of the injector, simplifies and fits the data according to the physical mechanism of the injector, obtains the calculation correlation, and performs one-dimensional modeling of the injector according to the correlation. At the same time, the calculation process of the one-dimensional model of the injector is proposed to achieve accurate simulation of the actual flow, inlet and outlet states, and flow rate of the injector, which is of great significance to the design, experiment and test of the transcritical CO2 injector system. It can be seen that the present invention can effectively overcome the problem that the current one-dimensional simulation of the injector system only stays at simple cycle calculations and it is difficult to simulate the dynamic operating characteristics of the system; at the same time, it solves the problem that the existing model assumes multiple efficiencies of the injector to calculate the injector, and the calculation accuracy is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of the structure of an ejector in an embodiment of the present invention; Figure 2 is a flow chart of a one-dimensional modeling method of an ejector in an embodiment of the present invention; Figure 3 It is a calculation flow chart of the one-dimensional model of the ejector in the embodiment of the present invention.

[0025] Figure 1 In the figure, 1. the mainstream working nozzle of the ejector; 2. the mainstream inlet of the ejector; 3. the guide flow inlet of the ejector; 4. the mixed fluid outlet of the ejector. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] See also Figure 1 The transcritical CO2 ejector of the embodiment of the present invention comprises: an intake section, a mixing section and a diffusion section; specifically comprises an ejector mainstream working nozzle 1, an ejector mainstream inlet 2, an ejector guide flow inlet 3, and an ejector mixed fluid outlet 4; See also Figure 2 The one-dimensional modeling method of the transcritical CO2 injector of the present invention comprises the following steps: Step 1: Obtain the performance matrix of the ejector based on the computational fluid dynamics results; Step 2: Simplify and fit the data based on the principles of fluid mechanics and the flow mechanism inside the ejector to obtain the mainstream fluid and the ejection ratio Calculation correlation formula of ; Step 3: Build a one-dimensional model of the ejector based on the thermodynamic principles, the transcritical CO2 ejector system principles and the obtained correlation formula; In order to facilitate public understanding, the technical solution of the present invention is described in detail below with reference to the accompanying drawings: The specific steps of the one-dimensional modeling method of the transcritical CO2 injector of the present invention are as follows: Step 1: According to the computational fluid dynamics results, the performance matrix of the ejector is obtained. The performance matrix is ​​shown in Table 1: Table 1

[0028] It can be seen that the performance matrix includes the density of the main inlet of the injector ,pressure , enthalpy and mass flow , the density at the jet inlet ,pressure , enthalpy and mass flow , the pressure at the ejector outlet and mass flow , the throat diameter in the ejector geometry constituted by; Furthermore, the performance and state of the ejector mainly depend on the geometric structure, the state of the mainstream inlet fluid, the state of the ejector inlet fluid and the back pressure of the outlet, that is, the working state and performance of the ejector can be determined according to the density of the mainstream inlet. ,pressure , the density of the jet inlet ,pressure and outlet back pressure The pressure at the ejector outlet The most important performance index of the ejector is the ejection ratio. , the ejection ratio It is expressed as:

[0029] In the formula, and are the mass flow rates of the ejector flow and the mainstream flow respectively; therefore, the key to establishing the one-dimensional model of the ejector lies in the ejection ratio and flow rate determination at the main inlet, the pilot flow inlet and the outlet of the ejector; Step 2: Simplify and fit the data according to the obtained performance matrix and the physical mechanism of the ejector to obtain the correlation equation. The specific process is as follows: In the second step, the data is simplified and fitted according to the obtained performance matrix and the physical mechanism of the ejector to obtain a correlation process; mainly including the mass flow rate of the mainstream fluid of the ejector Calculation of ejector ratio Calculation of The mainstream fluid mass flow rate in the ejector In the simplification and fitting of the ejector, the main flow fluid of the ejector expands, increases in speed, and reduces in pressure, which is related to the fluid state of the ejector's injection flow inlet and the outlet back pressure (i.e., the pressure at the ejector outlet). ) has little to do with the mass flow rate of the mainstream fluid. Simplified as a function of the mainstream inlet fluid state and the ejector throat size, the mass flow rate of the mainstream fluid is It is expressed as:

[0030] In the formula, and represent the density and pressure at the mainstream inlet, respectively. Indicates the throat diameter of the injector; Furthermore, the mainstream mass flow It can be expressed as:

[0031] In the formula, and represent the density and pressure at the mainstream inlet, respectively. represents the throat diameter of the ejector, is the critical pressure of CO2, A, B, C, D, E are coefficients; Furthermore, the fitting method uses the least squares method to calculate the correlation coefficient, and the principle is as follows:

[0032]

[0033] To make Minimum, then the deviation The partial differential of each unknown coefficient is equal to 0, that is:

[0034] Get a linear equation system, and solve it to get the unknown coefficients; Furthermore, in the ejector injection ratio In the modeling calculation, the mainstream fluid of the ejector is expanded and depressurized to eject the ejection fluid with higher pressure. The actual ejection process is related to the state of the mainstream fluid, the state of the ejection fluid inlet and the back pressure of the ejector outlet. Therefore, the ejection ratio is simplified and modeled as a function of the mainstream fluid state, the ejection fluid pressure and the outlet back pressure, which is expressed as:

[0035]

[0036] In the formula, is the diffusion chamber angle, , is the coefficient, , and are functions of the flow fluid state and the ejection fluid pressure, expressed as:

[0037]

[0038] Where i=1, 2, 3; , , , , , is the coefficient; Furthermore, the correlation coefficient was calculated according to the least square method; Furthermore, the mixed mainstream fluid and the ejection fluid increase in pressure and decrease in speed in the diffuser outflow section, and finally become the fluid at the ejector outlet; through the conservation of mass and energy, the outlet state and mass flow rate can be expressed as:

[0039]

[0040] Therefore, the ejector outlet enthalpy It can be calculated by energy conservation:

[0041] Step 3: Build a one-dimensional model of the ejector according to the obtained correlation formula; See also Figure 3 , a further improvement of the present invention is that the calculation process of the one-dimensional model of the ejector in step three is as follows, S1. According to the density of the main inlet ,pressure and the injector throat diameter Calculate the mass flow rate of the mainstream fluid :

[0042] S2. After obtaining the mainstream mass flow rate of the ejector, according to the injection flow inlet pressure , outlet back pressure and the ejector diffusion chamber angle Calculate the ejection ratio :

[0043] S3. Based on the mass flow rate of the mainstream fluid obtained in step S1 and the ejection ratio obtained in step S2 , calculate the mass flow rate of the ejection fluid and the mass flow rate at the ejector outlet :

[0044]

[0045] S4. Based on the mass flow rate of the mainstream fluid obtained in step S1 , the mass flow rate of the ejection fluid obtained in step S3 and the mass flow rate at the ejector outlet , mainstream inlet enthalpy and the ejector inlet enthalpy Calculate the ejector outlet enthalpy :

[0046] S5. According to the ejector outlet back pressure and the ejector outlet enthalpy obtained in step S4 Determine the ejector outlet dryness :

[0047] S6. Determine the dryness of the ejector outlet and the ejection ratio Whether it meets:

[0048] If satisfied, the iteration ends, otherwise the ejector outlet back pressure is changed , then return to step S1, and finally iterate until the ejector system stability condition is met; S7. Mass flow rate of the main fluid of the output ejector , mass flow rate of the jet fluid , Ejection ratio , ejector outlet back pressure , outlet enthalpy And outlet mass flow , that is, the mass flow rate and fluid state at the two inlets and one outlet of the ejector are fully determined.

[0049] Compared with the existing one-dimensional ejector model, the above one-dimensional ejector model realizes high-precision calculation of the dynamic characteristics of the ejector system, which is of great significance to the design, experiment and test of the transcritical CO2 ejector system.

[0050] The present invention also provides a one-dimensional modeling system for a transcritical CO2 injector, which is used to implement the one-dimensional modeling method for the transcritical CO2 injector. The system comprises: Data acquisition unit: used to obtain the performance matrix of the transcritical CO2 injector; Calculation unit: used for calculating the mass flow rate of the mainstream fluid of the ejector and the ejector injection ratio by using the performance matrix; Modeling unit: used to build a one-dimensional model of a transcritical CO2 ejector using the ejector mainstream fluid mass flow rate and the ejector injection ratio.

[0051] The embodiments of the present invention also provide corresponding electronic devices and computer-readable storage media for implementing the solutions provided by the embodiments of the present invention.

[0052] The device includes a memory and a processor, the memory is used to store instructions or codes, and the processor is used to execute the instructions or codes so that the device executes the one-dimensional modeling method of the transcritical CO2 injector described in any embodiment of the present application.

[0053] The storage medium stores a computer program, wherein the computer program, when executed by the processor, implements the one-dimensional modeling method of the transcritical CO2 injector described in any embodiment of the present application.

[0054] An embodiment of the present invention further provides a computer program product, the computer program product comprising computer instructions, the computer instructions instructing a computer to execute the one-dimensional modeling method of the transcritical CO2 injector.

[0055] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0056] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0057] The present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, readable storage media, optical storage, etc.) containing computer-usable program codes.

[0058] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0059] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A one-dimensional modeling method for a transcritical CO2 ejector, characterized in that: include: Obtain the performance matrix of transcritical CO2 injectors; The performance matrix is ​​used to calculate the ejector mainstream fluid mass flow rate and the ejector injection ratio; A one-dimensional model of the transcritical CO2 ejector is constructed using the ejector mainstream fluid mass flow rate and the ejector injection ratio.

2. A one-dimensional modeling method for a transcritical CO2 injector according to claim 1, characterized in that: The performance matrix of the transcritical CO2 ejector includes: The density, pressure, enthalpy and mass flow rate at the main inlet of the ejector, the density, pressure, enthalpy and mass flow rate at the ejector inlet, the pressure and mass flow rate at the ejector outlet, and the throat diameter in the geometric structure of the ejector.

3. A one-dimensional modeling method for a transcritical CO2 injector according to claim 2, characterized in that: Calculate the mass flow rate of the mainstream fluid in the injector based on the performance matrix and the physical mechanism of the transcritical CO2 injector as follows: in, represents the density of the mainstream entrance, Represents the pressure at the main entrance, represents the throat diameter of the ejector, is the critical pressure of CO2, and A, B, C, D, and E are coefficients; wherein, the coefficients A, B, C, D, and E are calculated by fitting using the least squares method.

4. A one-dimensional modeling method for a transcritical CO2 injector according to claim 2, characterized in that: Calculation of ejector ratio based on performance matrix and transcritical CO2 ejector physics as follows: in, is the mass flow rate at the jet inlet, is the mass flow rate at the main inlet of the ejector, is the density at the main inlet of the ejector, is the pressure at the main inlet of the ejector, is the pressure at the jet inlet, is the pressure at the ejector outlet, is the diffusion chamber angle, , is the coefficient, , and are functions of the flow fluid state and the ejection fluid pressure, expressed as: in, i Take 1, 2, 3, , , , , , is the coefficient, is the critical pressure of CO2; Ejector injection ratio The coefficients in are calculated by the least squares method.

5. The one-dimensional modeling method of a transcritical CO2 injector according to claim 2, characterized in that: The one-dimensional model of the transcritical CO2 ejector is constructed using the ejector mainstream fluid mass flow rate and the ejector injection ratio, including the following steps: S1. Calculate the mass flow rate of the main flow fluid of the ejector according to the density at the main flow inlet of the ejector, the pressure at the main flow inlet of the ejector and the throat diameter of the ejector: S2. After obtaining the mass flow rate of the mainstream fluid of the ejector, the ejection ratio is calculated based on the pressure of the ejection flow inlet, the ejector pressure and the ejector diffusion chamber opening angle: S3. Calculate the mass flow rate of the ejection fluid and the mass flow rate of the ejector outlet according to the mass flow rate of the mainstream fluid obtained in step S1 and the ejection ratio obtained in step S2: S4. Calculate the ejector outlet enthalpy value based on the mass flow rate of the mainstream fluid obtained in step S1, the mass flow rate of the ejector fluid obtained in step S3, the mass flow rate of the ejector outlet, the mainstream inlet enthalpy value, and the ejector inlet enthalpy value: S5. Determine the ejector outlet dryness according to the ejector outlet pressure and the ejector outlet enthalpy value obtained in step S4; S6. Determine whether the ejector outlet dryness and ejection ratio meet the ejector system stability conditions: S7. When the dryness and ejection ratio at the ejector outlet do not meet the ejector system stability conditions, change the ejector outlet pressure, and then repeat S1-S6 until the dryness and ejection ratio at the ejector outlet meet the ejector system stability conditions, and obtain the mass flow rate of the ejector mainstream fluid, the mass flow rate of the ejection fluid, the ejection ratio, the ejector outlet back pressure, the outlet enthalpy value and the outlet mass flow rate.

6. A one-dimensional modeling method for a transcritical CO2 injector according to claim 5, characterized in that: In step S3, the mass flow rate of the jet fluid is and the mass flow rate at the ejector outlet They are as follows: In step S4, the ejector outlet enthalpy as follows: In step S5, the ejector outlet dryness as follows: In step S6, the injector system stability condition is as follows: in, is the mass flow rate of the mainstream fluid in the ejector, is the ejection ratio, is the ejector mainstream inlet enthalpy, is the enthalpy of the jet inlet, is the ejector outlet back pressure.

7. A one-dimensional modeling system for a transcritical CO2 ejector, characterized in that: include: Data acquisition unit: used to obtain the performance matrix of the transcritical CO2 injector; Calculation unit: used for calculating the mass flow rate of the mainstream fluid of the ejector and the ejector injection ratio by using the performance matrix; Modeling unit: used to build a one-dimensional model of a transcritical CO2 ejector using the ejector mainstream fluid mass flow rate and the ejector injection ratio.

8. An electronic device, characterized in that: include: one or more processors; a storage device having one or more programs stored thereon; When the one or more programs are executed by the one or more processors, the one or more processors implement the one-dimensional modeling method for a transcritical CO 2 injector according to any one of claims 1 to 6.

9. A storage medium, characterized in that: A computer program is stored thereon, wherein when the computer program is executed by a processor, the one-dimensional modeling method of the transcritical CO2 injector according to any one of claims 1 to 6 is implemented.

10. A computer program product, comprising computer instructions, characterized in that: The computer instructions instruct the computer to execute the one-dimensional modeling method of the transcritical CO2 injector according to any one of claims 1-6.

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