A Visual Experimental Apparatus and Method for Gap Leakage in a Carbon Dioxide Scroll Compressor

Abstract

This application discloses a visualization experimental device and method for gap leakage in a carbon dioxide scroll compressor, relating to the field of positive displacement compressor leakage characteristic testing technology. The device includes: a working fluid supply module, a working condition adjustment module, a visualization experimental module, a flow rate testing module, and a data acquisition and processing module. The visualization experimental module includes a visualization experimental chamber and a Z-shaped transmission schlieren visualization module. The schlieren visualization module is coaxially adapted with the visualization experimental chamber and is used to acquire transient schlieren images of CO2 leakage flow inside the equivalent gap and in the downstream region of the gap. The working condition adjustment module is used to stabilize the inlet and outlet pressures, working fluid temperature, and working fluid flow rate of the visualization experimental chamber. The flow rate testing module is used to acquire gap leakage flow data. Through the visualization experimental method for gap leakage in a carbon dioxide scroll compressor, this application achieves simultaneous accurate measurement of leakage flow and visualization of the entire flow field.

Description

Technical Field

[0001] This application relates to the field of leakage characteristic testing technology for positive displacement compressors, and in particular to a visual experimental device and method for gap leakage in a carbon dioxide scroll compressor. Background Technology

[0002] With the rapid development of heat pump systems in new energy vehicles, CO2, as a natural and environmentally friendly refrigerant, has become the core working fluid in low-temperature heat pump systems for new energy vehicles due to its GWP=1, non-flammability, and excellent low-temperature heating performance. The scroll compressor is the core power component of the CO2 heat pump system, and its volumetric efficiency and operating energy efficiency directly determine the overall performance of the heat pump system. The working pressure difference of the CO2 working cycle is as high as 4MPa or more. Combined with the low viscosity of CO2 and the short scroll tooth structure of the scroll compressor, the leakage loss between the scroll plates accounts for more than 60% of the total compressor loss, which is the core bottleneck restricting the improvement of CO2 scroll compressor energy efficiency. For the gap leakage characteristics of CO2 scroll compressors, experimental testing is the core means to verify the performance of the turbulence suppression structure and analyze the leakage flow mechanism. However, the following core defects exist in related technologies that cannot be solved: 1. Most existing studies only conduct leakage flow tests, lacking visual experimental support. The gap leakage of CO2 scroll compressors is characterized by small scale and large pressure difference. The actual gap is only 10~50μm, making the leakage flow field difficult to observe directly. Existing experiments can only obtain macroscopic performance results of "the amount of leakage," but cannot analyze the microscopic mechanism of leakage flow or clarify the leakage suppression principle of the disturbance structure. 2. Existing visualization experiments have gaps in the observation range and cannot achieve full flow field analysis. Existing schemes can only observe the local flow field of the gap, lacking full-range synchronous observation of the flow field inside the gap and the development process of the flow field downstream of the gap. They cannot fully restore the core characteristics of the leakage jet, such as shear layer evolution, vortex structure generation and shedding, and shock wave distribution, and cannot provide support for the precise optimization of the disturbance structure. Summary of the Invention

[0003] The purpose of this application is to provide a visualization experimental device and method for gap leakage in a carbon dioxide scroll compressor, which can simultaneously carry out accurate measurement of leakage flow and visualization of the entire flow field, providing reliable experimental support for the optimization of the gap leakage suppression structure of a CO2 scroll compressor.

[0004] To achieve the above objectives, this application provides the following solution: In a first aspect, this application provides a visualization experimental device for gap leakage in a carbon dioxide scroll compressor, comprising: a working fluid supply module, a working condition adjustment module, a visualization experimental module, a flow rate testing module, and a data acquisition and processing module; the working fluid supply module, the working condition adjustment module, the visualization experimental module, and the flow rate testing module are connected sequentially along the working fluid flow direction; the visualization experimental module includes a high-pressure resistant and sealed visualization experimental chamber and a Z-type transmission schlieren visualization module, the schlieren visualization module being coaxially adapted with the visualization experimental chamber and used to acquire transient schlieren images of CO2 leakage flow inside the equivalent gap and in the downstream region of the gap; the working condition adjustment module is used to stabilize the inlet and outlet pressures, working fluid temperature, and working fluid flow rate of the visualization experimental chamber, and the flow rate testing module is used to acquire gap leakage flow data.

[0005] Optionally, the working fluid supply module includes a CO2 cylinder, a pressure reducing valve, and a check valve; the operating condition adjustment module includes a high-pressure stabilizing chamber, a low-pressure stabilizing chamber, a back pressure valve, an outlet control valve, and a constant temperature control module; the flow test module is a flow meter; and the data acquisition and processing module is used to simultaneously process gap leakage flow data and CO2 leakage flow transient schlieren images to complete flow field feature analysis and experimental result reconstruction.

[0006] Optionally, optical windows are coaxially formed on opposite side walls of the visualization experimental cavity, and quartz windows are sealed and fixed inside the optical windows; the nominal height of the equivalent gap of the visualization experimental cavity is controlled by polyethylene gaskets of different thicknesses.

[0007] Optionally, the schlieren visualization module has a double concave mirror structure, and its optical path is completely coaxial with the two quartz glass windows of the visualization experimental chamber. The optical path passes perpendicularly through the equivalent gap flow channel, covering the entire flow field region inside the gap and downstream of the gap. The schlieren visualization module includes a light source, a high-speed camera, two concave mirrors, and a knife-edge assembly.

[0008] Secondly, this application provides a method for visualizing gap leakage in a carbon dioxide scroll compressor based on the carbon dioxide scroll compressor gap leakage visualization experimental device described in the first aspect, comprising: S1: For the target CO2 scroll compressor's leakage gap, the three-dimensional leakage channel is expanded into a two-dimensional parallel plate gap model along the main leakage direction. The two-dimensional parallel plate gap model is scaled up proportionally by a set factor to determine the geometric parameters of the equivalent experiment. Based on the basic control equations of fluid mechanics, the flow characteristic parameters of the prototype under real operating conditions are calculated. The geometric amplification ratio and operating temperature are fixed on the two-dimensional parallel plate gap model side. The optimal operating parameters of the two-dimensional parallel plate gap model are determined based on minimizing the deviation of the flow similarity criterion parameters between the two-dimensional parallel plate gap model and the prototype. The actual operating conditions of the target compressor are matched to determine the inlet and outlet pressures and working fluid temperature parameters of the experiment, so that the deviations of the Reynolds number and Mach number of the CO2 leakage flow in the equivalent gap from the flow characteristic parameters in the actual compressor gap are within the set range. S2: Construct a visualization experimental device for gap leakage in a carbon dioxide scroll compressor; S3: Calibrate the gap dimensions and flow measurement module of the visualization experimental chamber; perform high-pressure holding test on the experimental system; S4: Adjust the inlet and outlet pressures of the visualization experimental chamber to the target value, stabilize the working fluid temperature through the constant temperature control module, and determine that the steady-state experimental condition has been reached after the system operating conditions have reached the set time period and the peak-to-peak pressure fluctuation, peak-to-peak temperature fluctuation, and peak-to-peak flow fluctuation meet the set steady-state operating conditions. S5: Install the control group sample into the fixed plate mounting position of the visualization experimental chamber. Within the set time, collect the gap leakage flow data and simultaneously collect the transient schlieren images of CO2 leakage flow inside the equivalent gap and downstream region through the schlieren visualization module. Complete no less than the set number of repeated experiments. Replace the experimental group sample and repeat the above acquisition operation under the same working conditions to complete the test of all samples. The control group sample is a smooth plate sample, and the experimental group sample is a sample with a 20x magnified turbulence suppression structure to be tested. S6: By adjusting the inlet and outlet pressures, working fluid temperature, and nominal clearance height of the visualization experimental chamber, the full operating conditions and common clearance size range of the CO2 scroll compressor are covered. Repeat steps S4-S5 to complete the extended experiment with multiple operating conditions and multiple clearance sizes. S7: Perform statistical analysis on the gap leakage flow data, calculate the leakage suppression efficiency of the test turbulence suppression structure in the experimental group samples; process the transient schlieren image of CO2 leakage flow to obtain the density field distribution of the leakage flow, analyze the flow field characteristic parameters, and clarify the leakage suppression mechanism of the test turbulence suppression structure; restore the experimental results to the real compressor operating conditions through equivalent mapping relationship to complete the verification of experimental results.

[0009] Optionally, the equivalent clearance nominal height, flow channel length, and flow channel width after proportional scaling are all the same multiple of the corresponding dimensions of the actual compressor clearance; the relative dimensions of the turbulence suppression structure to be tested are completely consistent with the relative dimensions of the structure inside the actual compressor, and the relative dimensions are the ratio of the structure depth to the clearance nominal height, the ratio of the structure width to the clearance nominal height, and the ratio of the structure spacing to the clearance nominal height.

[0010] Optionally, the material of the control sample and the experimental sample is the same as that of the target compressor scroll disk; the turbulence structure of the experimental sample is processed by micron-level laser etching or precision milling, with a processing size error of ≤±1mm.

[0011] Optionally, the transient schlieren image of the CO2 leakage flow is processed, specifically including: processing the transient schlieren image of the CO2 leakage flow using the background schlieren method; The flow field characteristic parameters include the shear layer thickness of the leaking jet, the vortex core size, the vortex shedding frequency, and the shock wave spacing.

[0012] Optionally, the experimental results are verified by comparing them with the three-dimensional CFD simulation results based on the GERG-2008 real gas equation of state, ensuring that the deviation between the experimental results and the simulation results does not exceed 8%. The equivalent mapping relationship is based on the dual equivalence principle of geometric similarity + flow similarity, including a one-to-one correspondence of geometric parameters, flow similarity criterion parameters, physical property parameters, and operating condition parameters, and introduces a wall roughness correction coefficient. and end effect correction coefficient Perform accuracy compensation.

[0013] Optionally, the physical properties are calculated based on the GERG-2008 real gas equation of state, including compressibility factor, density, dynamic viscosity, thermal conductivity, specific heat at isobaric pressure, and adiabatic index. According to the specific embodiments provided in this application, this application has the following technical effects: This application provides a visualization experimental device and method for gap leakage in a carbon dioxide scroll compressor. Through a working fluid supply module, a working condition adjustment module, a visualization experimental module (including a visualization experimental chamber and a Z-type transmission schlieren visualization module), and a flow rate testing module, it achieves precise measurement of leakage flow and simultaneous acquisition of schlieren visualization for gap leakage in a CO2 scroll compressor. This overcomes the limitation of existing technologies that can only conduct single flow rate experiments. This application can simultaneously acquire macroscopic leakage suppression performance data and microscopic flow mechanism data of the structure under test, solving both the performance verification problem of "how much leakage is reduced" and the problem of "why leakage can be suppressed." The mechanism analysis of this problem provides dual support for the optimization of the turbulence structure. By designing an equivalent model with proportional similarity and scale, and with a complete equivalent mapping relationship and compensation for real gas effects, the industry problem of the inability to directly visualize and observe the leakage flow in the micron-level gap of CO2 compressor and the inability to restore the experimental results to the real working conditions is solved. By proportionally scaling up, the problems of the inability of the optical path to penetrate the real gap and the inability to observe the flow field are solved. Furthermore, by using equivalent control based on multiple flow criteria, the deviation between the flow field in the equivalent gap and the leakage flow field in the gap of the real compressor is ensured to be within the set value range (≤5%). The experimental results can be accurately mapped to the real working conditions and have direct engineering guidance value, providing reliable experimental support for the optimization of the gap leakage suppression structure of CO2 scroll compressor. Attached Figure Description

[0014] 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 described 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: Figure 1 A schematic diagram of a visualization experimental device for gap leakage of a carbon dioxide scroll compressor provided in an embodiment of this application; Figure 2 A three-dimensional structural diagram of a visual experimental chamber provided in one embodiment of this application; Figure 3 A cross-sectional view of a visual experimental chamber provided in an embodiment of this application; Figure 4 A front view of a visualization experimental chamber provided in one embodiment of this application; Figure 5 A top view of a visualization experimental chamber provided in one embodiment of this application; Figure 6 A schematic diagram of the optical path layout of a schlieren visualization module provided in an embodiment of this application; Figure 7This is a flowchart illustrating a method for visualizing gap leakage in a carbon dioxide scroll compressor, as provided in one embodiment of this application.

[0015] Reference numerals: Top viewing window glass—1; Top viewing window flange—2; Top cover plate—3; First gasket—4; Bottom viewing window flange—5; Cavity body—6; Front viewing window glass—7; Front viewing window flange—8; Screw—9; Second gasket—10; Bottom viewing window glass—11; Rear viewing window glass—12; Rear viewing window flange—13. Detailed Implementation

[0016] 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.

[0017] 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.

[0018] In an exemplary embodiment, a visualization experimental device for gap leakage in a carbon dioxide scroll compressor is provided, comprising a working fluid supply module, a condition adjustment module, a visualization experimental module, a flow test module, and a data acquisition and processing module; the working fluid supply module, the condition adjustment module, the visualization experimental module, and the flow test module are connected sequentially along the working fluid flow direction; the visualization experimental module includes a visualization experimental chamber and a Z-shaped transmission schlieren visualization module, the schlieren visualization module being coaxially adapted with the visualization experimental chamber and used to acquire transient schlieren images of CO2 leakage flow inside the equivalent gap and in the downstream region of the gap; the condition adjustment module is used to stabilize the inlet and outlet pressures, working fluid temperature, and working fluid flow rate of the visualization experimental chamber, and the flow test module is used to acquire gap leakage flow data.

[0019] like Figure 1 As shown, the working fluid supply module includes a CO2 cylinder, a pressure reducing valve, and a check valve; the operating condition adjustment module includes a high-pressure stabilizing chamber, a low-pressure stabilizing chamber, a back pressure valve, an outlet control valve, and a constant temperature control module; the flow test module is a flow meter; the data acquisition and processing module is used to simultaneously process gap leakage flow data and CO2 leakage flow transient schlieren images to complete flow field feature analysis and experimental result restoration.

[0020] The visualization experimental chamber is a high-pressure resistant, sealed hollow cavity suitable for high pressure applications. Optical windows are coaxially positioned on opposite side walls of the main body 6 of the chamber, each containing a sealed quartz window. The quartz window is made of optical-grade quartz glass, such as… Figure 2-5 As shown, the visualization experimental chamber includes a main body 6. Optical windows are provided on both the front and rear sides of the main body 6. A front viewing window 7 and a rear viewing window 12 are sealed and fixed inside the front and rear optical windows. The front viewing window 7 is fixed inside the optical window by a front viewing window flange 8 and screws 9. The rear viewing window 12 is fixed inside the optical window by a rear viewing window flange 13 and screws 9. Second gaskets 10 are provided on both the front and rear sides of the front and rear viewing windows 7 and 12. The main body 6 also has a top viewing window 1 and a bottom viewing window 11. The top viewing window 1 is embedded in the upper cover plate 3 of the visualization experimental chamber by a top viewing window flange 2 and screws 9. The bottom viewing window 11 is embedded in the lower cover plate of the visualization experimental chamber by a bottom viewing window flange 5 and screws 9. The main body 6 also has a gas inlet on each of its left and right sides. A first gasket 4 is provided between the upper cover plate 3 and the cavity body 6, and between the lower cover plate and the cavity body 6. The first gasket 4 and the second gasket 10 are polyethylene sealing gaskets. The nominal height of the equivalent gap of the visualization experimental cavity is controlled by polyethylene gaskets (polyethylene sealing gaskets) of different thicknesses. Different gap sizes can be adjusted by replacing gaskets of different nominal thicknesses.

[0021] The schlieren visualization module has a double-concave mirror structure, including a first concave mirror and a second concave mirror. The optical paths of the first and second concave mirrors are completely coaxial with the two quartz glass windows (front window 7 and rear window 12) of the visualization experimental chamber. The optical path perpendicularly passes through the equivalent gap flow channel, covering the entire flow field region inside and downstream of the gap. The schlieren visualization module includes a light source, a light source slit (the light source slit makes the light source incident on the first concave mirror a point light source), a high-speed camera, two concave mirrors, and a knife-edge assembly (the knife-edge assembly is used to block half of the light source to provide schlieren contrast). The high-speed camera is used to acquire transient schlieren images of CO2 leakage flow inside and downstream of the equivalent gap. The optical path layout of the schlieren visualization module is as follows: Figure 6 As shown.

[0022] Based on the same inventive concept, this application also provides a method for visualizing gap leakage in a carbon dioxide scroll compressor using the aforementioned visualization experimental apparatus for carbon dioxide scroll compressor gap leakage. Specific limitations in one or more embodiments of the visualization experimental apparatus for carbon dioxide scroll compressor gap leakage provided below can be found in the above-described limitations of the visualization experimental apparatus for carbon dioxide scroll compressor gap leakage, and will not be repeated here.

[0023] In an exemplary embodiment, a method for visualizing gap leakage in a carbon dioxide scroll compressor is provided, comprising the following steps S1 to S7. The flow of the method for visualizing gap leakage in a carbon dioxide scroll compressor is as follows: Figure 7 As shown.

[0024] The basic experimental procedures for testing the leakage gap of a CO2 scroll compressor include working fluid supply, operating condition adjustment, and leakage flow rate testing.

[0025] S1: For the target CO2 scroll compressor's leakage gap, the three-dimensional leakage channel is expanded into a two-dimensional parallel plate gap model along the main leakage direction. The two-dimensional parallel plate gap model is then scaled up proportionally by a set factor to determine the geometric parameters of the equivalent experiment. Based on the fundamental fluid dynamics control equations, the flow characteristic parameters of the prototype under real operating conditions are calculated. With the geometric scaling ratio and operating temperature fixed on the two-dimensional parallel plate gap model side, the optimal operating parameters of the two-dimensional parallel plate gap model are determined based on minimizing the deviation of the flow similarity criterion parameters between the two-dimensional parallel plate gap model and the prototype. Matching the actual operating conditions of the target compressor, the inlet and outlet pressures and working fluid temperature parameters of the experiment are determined so that the Reynolds number and Mach number of the CO2 leakage flow in the equivalent gap deviate from the flow characteristic parameters in the actual compressor gap within a set range. Step S1 above is used for equivalent model construction and experimental parameter determination. In a specific example, the set factor can be 5 to 20 times, and the deviation should be within the set range, i.e., the deviation should not exceed 5%.

[0026] S2: Construct a visualization experimental device for gap leakage in a carbon dioxide scroll compressor. Step S2 is used for experimental system construction and sample preparation: Construct an experimental device along the working fluid flow direction, including a CO2 cylinder, pressure reducing valve and check valve, high-pressure stabilizing chamber, flow meter, outlet control valve, visualization experimental chamber, low-pressure stabilizing chamber, and back pressure valve; construct a Z-type transmission schlieren visualization module coaxially adapted to the visualization experimental chamber; and prepare a control sample without turbulence structure and an experimental group sample with the turbulence suppression structure to be tested.

[0027] S3: Calibrate the gap dimensions and flow measurement modules of the visualization experimental chamber; perform a high-pressure holding test on the experimental system. The visualization experimental chamber is also equipped with a pressure measurement module, which is a pressure gauge with a range of 1 MPa and an accuracy of 1%. This step S3 is used for system calibration and airtightness verification: calibrating the gap dimensions, pressure measurement modules, and flow measurement modules of the visualization experimental chamber to ensure that the gap dimensions are within acceptable limits. 0.05mm, overall system measurement error 2%; A high-pressure holding test was conducted on the experimental system. Under a holding pressure reference of 6 MPa for 2 hours, the pressure drop was [not specified]. 0.05 MPa indicates that the airtightness is acceptable.

[0028] S4: Adjust the inlet and outlet pressures of the visualization experimental chamber to the target values, stabilize the working fluid temperature through the constant temperature control module, and determine that the steady-state experimental condition has been reached after the system has been operating for a set period of time, and the peak-to-peak values ​​of pressure fluctuation, temperature fluctuation, and flow rate fluctuation meet the set steady-state operating conditions. Step S4 is used for experimental condition adjustment: the inlet and outlet pressures of the visualization experimental chamber are adjusted to the target values ​​through the pressure reducing valve and back pressure valve, the working fluid temperature is stabilized through the constant temperature control module, and the flow field is opened and closed through the outlet control valve.

[0029] S5: Install the control group sample into the fixed plate mounting position in the visualization experimental chamber. Within the set time, collect the gap leakage flow rate data. Simultaneously, acquire transient schlieren images of CO2 leakage flow inside the equivalent gap and in the downstream region of the gap through the schlieren visualization module. Complete at least a set number of repeated experiments. Replace the experimental group sample and repeat the above acquisition operation under the same operating conditions to complete the testing of all samples. The control group sample is a smooth plate sample, and the experimental group sample is a sample with a 20x magnified flow suppression structure to be tested. Step S5 is the leakage flow rate and flow field visualization acquisition step.

[0030] S6: By adjusting the inlet and outlet pressures, working fluid temperature, and nominal clearance height of the visualization experimental chamber, covering all operating conditions and common clearance size ranges of the CO2 scroll compressor, repeat steps S4-S5 to complete the extended experiment with multiple operating conditions and multiple clearance sizes. This step S6 is the extended experiment step for multiple operating conditions / multiple clearances.

[0031] S7: Perform statistical analysis on the gap leakage flow data to calculate the leakage suppression efficiency of the tested turbulence suppression structure in the experimental group samples; process the transient schlieren image of the CO2 leakage flow to obtain the density field distribution of the leakage flow, analyze the flow field characteristic parameters, and clarify the leakage suppression mechanism of the tested turbulence suppression structure; restore the experimental results to the actual compressor operating conditions through equivalent mapping relationships to complete the verification of the experimental results. Step S7 is the data post-processing and result analysis step.

[0032] As an optional implementation, in step S1 above, the equivalent nominal height of the clearance, the flow channel length, and the flow channel widening after proportional scaling are all multiples of the corresponding dimensions of the clearance in the actual compressor. The relative dimensions of the turbulence suppression structure under test are completely consistent with the relative dimensions of the structure inside the actual compressor, which are the ratios of structure depth to nominal clearance height, structure width to nominal clearance height, and structure spacing to nominal clearance height. The experimental operating parameters are completely consistent with the actual operating conditions of the target compressor. Based on geometric scaling, the flow similarity between the two-dimensional parallel plate clearance model and the prototype is ensured through multi-similarity criterion matching. The multi-similarity criteria include at least the Mach number criterion characterizing compressibility and the Euler number criterion characterizing pressure driving force characteristics.

[0033] In step S2 above, the material of the control sample and the experimental sample is the same as that of the target compressor scroll disk; the test turbulence suppression structure of the experimental sample is processed by micron-level laser etching or precision milling, with a processing size error ≤ ±1mm.

[0034] In step S7 above, the transient schlieren image of the CO2 leakage flow is processed, specifically including: processing the transient schlieren image of the CO2 leakage flow using the Background-Oriented Schlieren (BOS) method. The extracted flow field characteristic parameters include the shear layer thickness of the leakage jet, the vortex core size, the vortex shedding frequency, and the shock wave spacing.

[0035] The experimental results were verified by comparing the results with those of a three-dimensional CFD simulation based on the GERG-2008 real gas equation of state, ensuring that the deviation between the experimental and simulation results did not exceed 8%. The equivalent mapping relationship was based on the dual equivalence principle of geometric similarity and flow similarity, including a one-to-one correspondence of geometric parameters, flow similarity criterion parameters, physical property parameters, and operating condition parameters, and introduced wall roughness correction coefficients and end effect correction coefficients for accuracy compensation. The matching of flow similarity criterion parameters was based on the principle of multi-similarity criterion collaborative matching, which minimized the comprehensive deviation of multiple flow similarity criterion parameters between the model and the prototype, ensuring that the deviation of the flow characteristic parameters between the model and the prototype was within the set range.

[0036] The equivalent mapping relationship in this application is based on the dual equivalence principle of geometric similarity and flow similarity, ensuring that the scaled-up model experimental results can be accurately reproduced to the actual compressor prototype operating conditions. The core parameters to be considered in the equivalent mapping include four categories: geometric parameters, flow similarity criterion parameters, physical property parameters, and operating condition parameters. All parameters correspond one-to-one to ensure the accuracy of the mapping.

[0037] 1. Geometric parameters: nominal height of the gap, flow channel length, flow channel width, depth, width, and spacing of the turbulence structure of the prototype (real compressor gap); corresponding geometric parameters of the model (experimental equivalent gap) (nominal height of the gap, flow channel length, flow channel width, depth, width, and spacing of the turbulence structure); proportional magnification factor.

[0038] 2. The parameters of the flow similarity criterion include: Reynolds number Re, Mach number Ma, Euler number Eu, Prandtl number Pr, and Strauhall number Sr.

[0039] 3. Physical properties include: the compressibility factor Z of the CO2 working fluid, and density. Dynamic viscosity thermal conductivity The adiabatic index k was calculated based on the GERG-2008 real gas equation of state.

[0040] 4. Operating parameters: Inlet and outlet pressures of the prototype and model (inlet pressure p) in Export pressure p out ), working fluid temperature T, and gap outlet characteristic velocity u.

[0041] For compressible viscous steady laminar flow with CO2 gap leakage, starting from the three-dimensional Navier-Stokes governing equations, dimensionless processing is performed to derive the core criteria for flow similarity.

[0042] 1. Dimensionless processing: Define dimensionless coordinates Dimensionless velocity Dimensionless pressure ,in The coordinates are before dimensionless processing, and L is the characteristic length (nominal height of the gap). The characteristic velocity (average velocity at the gap inlet). The pressure before dimensionless processing.

[0043] 2. Substituting the dimensionless parameters into the continuity equation, momentum equation, and energy equation, and simplifying, we obtain four dimensionless similarity criterion numbers that must be matched (the first dimensionless similarity criterion number - the fourth dimensionless similarity criterion number).

[0044] First dimensionless similarity criterion: Reynolds number : The ratio of inertial force to viscous force, expressed by the formula: (1); Ensure that the Reynolds number deviation between the model and the prototype is ≤5% to ensure consistent flow viscosity characteristics.

[0045] Second dimensionless similarity criterion number: Mach number Characterizing flow velocity The ratio to the local speed of sound is given by the formula: (2); in, For the local speed of sound, For specific heat ratio, The compression factor, This is the universal gas constant. The molar mass of CO2. Ensure the Mach number deviation between the model and the prototype is ≤5%, guaranteeing consistent compressibility of the flow.

[0046] The third dimensionless similarity criterion number: Euler number Eu: characterizing the ratio of pressure driving force to inertial force, the formula is: (3); in, The pressure difference between the inlet and outlet (total pressure p0 and outlet back pressure p)out Difference), For the inlet density, The average flow velocity at the gap inlet is denoted as .

[0047] The fourth dimensionless similarity criterion number: the Strauhal number Sr: characterizes the ratio of vortex convection time to available development time, i.e., the dimensionless formation time ratio, and is formulated as follows: (4); in, The characteristic length of the downstream development zone, For the characteristic flow velocity at the gap outlet, t ref For reference time, an effective leakage time window t is taken in the prototype. window,p The effective leakage time window is determined by the scroll compressor speed and the effective leakage phase angle. This ensures that the vortex's truncation development state is consistent downstream, corresponding to similar unsteady flow development characteristics. In the experiment, the mapping relationship t... window,m =n 2 ·t window,p The observation time window of the control model is used to extract only the transient schlieren images within the corresponding window for analysis.

[0048] The specific formulas for equivalent mapping relationships include formulas for calculating the proportional magnification factor, flow parameter mapping formulas, leakage flow mapping formulas, and flow field parameter mapping formulas.

[0049] 1) The formula for calculating the magnification factor is as follows: (5); in, , , These represent the nominal height of the gap, the flow channel length, and the flow channel width in a two-dimensional parallel plate gap model. , , These represent the nominal height of the clearance (prototype), the flow channel length, and the flow channel width, respectively. In other words, all geometric dimensions of the model are the corresponding dimensions of the prototype. The relative dimensions (d / h, w / h, s / h) of the turbulence suppression structure under test are completely consistent with the prototype, ensuring geometric similarity.

[0050] 2) Flow Parameter Mapping Formula: To ensure flow similarity between the model and the prototype, the flow characteristic parameters of the prototype are determined as similarity targets based on the fundamental governing equations of fluid mechanics. With the geometric scaling ratio and operating temperature fixed on the model side, the model's operating parameters are determined based on minimizing the combined deviations of multiple flow similarity criteria parameters between the model and the prototype. From this, the mapping relationship between the model's operating parameters and the prototype's operating parameters is derived: Inlet pressure p of the two-dimensional parallel plate gap model. in,m =Prototype inlet pressure pin,p ; Two-dimensional parallel plate gap model, outlet pressure p out,m =Prototype outlet pressure p out,p Model characteristic flow velocity =Prototype Feature Flow Rate This formula ensures that the Reynolds number, Mach number, and other flow similarity criterion parameters of the model and the prototype are consistent, and the deviations of each criterion parameter are within the set range. (6); in, and These are the nominal heights of the gap between the two-dimensional parallel plate gap model and the prototype, respectively; Re m and Re p , respectively, are the Reynolds numbers of the two-dimensional parallel plate gap model and the prototype; n is the proportional magnification factor.

[0051] 3) Leakage flow mapping formula, prototype actual leakage flow Flow rate measured by model experiment Mapping relationship: (7); in: The model mass leakage flow rate (in kg / h) was measured experimentally. This is the wall roughness correction factor; This is the end effect correction factor.

[0052] 4) Flow field parameter mapping formula, i.e., the mapping relationship between the flow field parameters measured in the model experiment and the prototype: Velocity field: Length scale: (e.g., vortex core size, shear layer thickness, shock wave spacing); Time scale: (e.g., vortex shedding frequency:) ); and The time scales are respectively for the prototype and the two-dimensional parallel plate gap model; and These are the vortex shedding frequencies of the prototype and the two-dimensional parallel plate gap model, respectively.

[0053] This application introduces two similarity criterion correction coefficients (wall roughness correction coefficient and end effect correction coefficient) to address the structural differences between the scaled-up model and the real prototype, ensuring mapping accuracy.

[0054] 1) Wall roughness correction factor The surface roughness of the actual compressor scroll plate differs from that of the experimental sample. The correction factor formula is as follows: ;in The friction coefficient is calculated using the Poiseuille friction formula, which is applicable to laminar flow: , The absolute roughness of the wall surface. This is the nominal height of the gap. When the surface roughness of the experimental specimen is the same as that of the prototype, =1.

[0055] 2) End effect correction coefficient The actual compressor's clearance leakage channel is a closed volute end, exhibiting an end secondary flow effect. However, the experimental model (two-dimensional parallel plate clearance model) uses an infinitely wide plate clearance, requiring the introduction of end effect correction. The correction coefficient formula is as follows: ;in, To widen the flow channel, The formula is for the nominal height of the gap, and applies to the ratio of the width to the gap. Under the working conditions, when hour, The end effect is negligible.

[0056] Real gas effect compensation method: CO2 deviates from the ideal gas state under high pressure conditions, and property compensation must be performed using the GERG-2008 real gas equation of state. The specific steps are as follows: 1. Calculation of physical property parameters: For the operating conditions (p, T) of the prototype and model, the compressibility factor, density, dynamic viscosity, thermal conductivity, specific heat at constant pressure, and adiabatic index of CO2 under the corresponding operating conditions are calculated using the GERG-2008 equation to replace the physical property parameters of the ideal gas assumption.

[0057] 2. Similarity criterion compensation: Substitute the calculated real gas physical property parameters into the calculation formulas for Reynolds number, Mach number, and Prandtl number to ensure that the similarity criterion numbers of the model and the prototype match, and avoid the deviation of physical properties caused by the ideal gas assumption.

[0058] 3. Flow Result Compensation: In the leakage flow mapping calculation, the ratio of the actual gas density under the prototype and model operating conditions is used to perform secondary compensation on the flow results. The compensation formula is as follows: in The actual CO2 density under prototype inlet conditions. The actual CO2 density under the model's inlet conditions; This represents the actual leaked traffic volume.

[0059] 4. Sound velocity compensation: The local sound velocity is calculated using the real gas equation of state to correct the calculated Mach number, ensuring that the compressible flow characteristics of the model are consistent with those of the prototype, and avoiding Mach number deviation caused by the calculation of the sound velocity of ideal gas.

[0060] The test object in this embodiment is the axial clearance of a CO2 scroll compressor used in heat pumps for new energy vehicles. A specific operating condition of the target compressor is: high-pressure side pressure 5.6 MPa, low-pressure side pressure 2.8 MPa, working fluid temperature 35℃, nominal axial clearance size 15 μm, and the tested turbulence suppression structure is a multi-stage arc-shaped groove turbulence suppression structure. The experimental method includes the following steps 1 to 7.

[0061] Step 1: Constructing the equivalent model and determining experimental parameters, including the following steps 1.1 to 1.2.

[0062] Step 1.1, Geometric equivalent model construction: The three-dimensional wedge-shaped leakage channel of the axial clearance of the target compressor is unfolded into a two-dimensional parallel plate clearance model along the main leakage direction. Then, the equivalent experimental geometric parameters are determined by using a 20x similarity magnification: the nominal height of the equivalent clearance is 300μm, the channel length is 56mm, and the channel width is 50mm. The turbulence structure to be tested is simultaneously magnified 20 times, and the relative dimensions of the structure are completely consistent with the actual design.

[0063] Step 1.2, Determination of experimental operating parameters: Matching the actual operating conditions of the target compressor, the experimental parameters are determined as follows: high pressure side pressure 5.6MPa, low pressure side pressure 2.8MPa, working fluid temperature 35℃; calculated by the GERG-2008 real gas state equation, the Reynolds number and Mach number of the leakage flow in the equivalent gap deviate from the parameters in the actual compressor gap by ≤3%, which meets the equivalence requirements.

[0064] Step 2: Experimental system setup and sample preparation, including the following steps 2.1 to 2.2.

[0065] Step 2.1, Experimental System Setup: The experimental system is constructed sequentially along the flow direction of the working fluid, specifically: CO2 cylinder → pressure reducing valve and check valve → high-pressure stabilizing chamber → flow meter → outlet control valve → visualization experimental chamber → low-pressure stabilizing chamber → back pressure valve; the high-pressure and low-pressure stabilizing chambers are both integrally formed from 316 stainless steel, with a design pressure of 10MPa; the visualization experimental chamber is a 316 stainless steel high-pressure resistant chamber, with coaxial optical windows on the front and rear side walls, each sealed with a 30mm thick optical-grade quartz glass window with 93% light transmittance and surface accuracy. The equivalent clearance nominal height passes 300. Thick, high-precision polyethylene gasket control, gasket thickness accuracy A Z-shaped double-concave mirror transmissive schlieren visualization module is constructed to support the system. The optical path is completely coaxial with the quartz glass window and passes perpendicularly through the equivalent gap flow channel. The core parameters of the system are as follows: The light source can be a halogen tungsten lamp. The parameter settings for each component in the schlieren visualization module are as follows: Halogen tungsten lamp: rated power 300W, rated voltage 24V DC / AC, luminous flux 10450lm, color temperature 3500K, spectral range 300~2500nm; High-speed camera: shooting resolution 1920×1080, shooting frame rate 2200fps, shutter speed 128µs, color ISO 8000, monochrome ISO 32000; Concave mirror: effective diameter 254mm, focal length 1500mm, reflectivity ≥95%; Knife edge assembly: knife edge width 0.1~5mm, adjustment accuracy ±0.01mm.

[0066] Step 2.2, Sample preparation: Two groups of flat plate samples were prepared, with the control group being a smooth flat plate sample and the experimental group being a sample with a multi-level arc-shaped groove turbulence structure magnified 20 times; the turbulence structure was machined by micron-level precision milling with a machining dimensional error ≤ ±1mm.

[0067] Step 3: System calibration and airtightness verification, which consists of the following two steps.

[0068] Step 3.1, System Calibration: Install the smooth flat plate sample into the cavity fixed plate mounting position, and calibrate it through 300... The polyethylene gasket controls the gap height, and a laser displacement sensor is used for multi-point calibration at 6 points to measure the gap size deviation. The pressure gauges on the high and low pressure sides are calibrated using a 0.1-grade standard pressure sensor; the Coriolis flow meter is calibrated using a standard flow meter, with a flow measurement error ≤0.15%FS; the schlieren optical path is coaxially calibrated to ensure that the optical path is free from offset and obstruction, and fully covers the gap and downstream flow field region.

[0069] Step 3.2 Air tightness verification: Close all valves, fill the experimental system with 6MPa high-purity carbon dioxide, maintain the pressure for 2 hours, and if the pressure drop is ≤0.03MPa, the air tightness is deemed qualified.

[0070] Step 4, Experimental Condition Adjustment: Slowly open the CO2 cylinder, stabilize the pressure in the low-pressure stabilizing chamber to 2.8MPa through the back pressure valve, stabilize the pressure in the high-pressure stabilizing chamber to 5.6MPa through the pressure reducing valve, and stabilize the working fluid temperature to 35℃ through the constant temperature control module.

[0071] Step 5: Simultaneous acquisition experiment of leakage flow rate and flow field visualization.

[0072] Control group experiment: Using a smooth flat plate sample as the test object, under steady-state conditions, leakage flow data were collected by a flow meter for 60 seconds at a sampling frequency of 10 Hz. Five sets of repeated experiments were completed. After removing abnormal data, the average value was taken to obtain the reference leakage of the smooth gap. Simultaneously, the schlieren visualization module was turned on to collect transient schlieren images of the flow field in the gap and downstream for 5 seconds to obtain valid images.

[0073] Experimental group experiment: Replace the experimental group sample with the test turbulence suppression structure, repeat the above operating condition adjustment and acquisition operation to ensure that the experimental conditions are completely consistent with the control group, and synchronously acquire the transient schlieren image of CO2 leakage flow under the corresponding operating conditions.

[0074] Step 6, Extended working condition experiment: Maintain gap size of 300 Keeping the inlet and outlet pressures and working fluid temperature unchanged, conduct extended experiments under different operating conditions; keeping the operating parameters unchanged, replace 100 ~1000 Thick polyethylene gasket, adjustable gap height is 100. ~1000 (Corresponding to actual gap 5) ~50 We completed extended experiments under different gap sizes to obtain an experimental database covering all working conditions and the entire gap range.

[0075] Step 7, data post-processing and result analysis, includes the following steps 7.1 to 7.3.

[0076] Step 7.1, Flow data analysis: The leakage suppression efficiency of the multi-stage arc-shaped groove turbulence suppression structure in this embodiment is calculated, verifying the excellent leakage suppression performance of the turbulence suppression structure under test; through the equivalent mapping relationship, the experimental flow results are restored to the real compressor operating conditions to obtain the benchmark leakage amount of the turbulence suppression structure under test under real operating conditions.

[0077] Step 7.2, Schreiber image analysis: The transient schreiber image of the CO2 leakage flow is post-processed using the BOS method to obtain the density field distribution of the leakage flow, and parameters such as shear layer thickness, vortex core size, and vortex shedding frequency are extracted to clarify the leakage suppression mechanism of the disturbance suppression structure under test.

[0078] Step 7.3, Experimental Result Verification: The experimental results were compared with the three-dimensional CFD simulation results based on the GERG-2008 real gas equation of state to verify the accuracy and reliability of the experimental results.

[0079] The existing experimental setups suffer from significant challenges in gap adjustment, making them unsuitable for batch optimization testing of turbulent structures. They also fail to rapidly complete multiple sets of experiments with different gap sizes and structural parameters, resulting in long optimization cycles and low efficiency. Furthermore, the equivalent mapping methods used in scaled-up experiments are incomplete, matching only a single flow criterion and failing to consider the actual CO2 gas effect. Consequently, the experimental results cannot accurately reflect real compressor operating conditions and lack engineering guidance value. To address these issues, this application provides a visual experimental setup and method for carbon dioxide scroll compressor gap leakage, solving the technical problems of existing technologies that only allow for single-flow experiments, lack full-field visualization, face significant gap adjustment challenges, large deviations between experimental results and real operating conditions, and inability to support turbulent structure optimization.

[0080] This application has the following significant beneficial effects: 1. This application is the first to achieve precise measurement and simultaneous acquisition of schlieren visualization of leakage flow in CO2 scroll compressors, breaking the limitation of existing technologies that can only conduct single-flow experiments. This application can simultaneously acquire macroscopic leakage suppression performance data and microscopic flow mechanism data of the structure under test, solving both the performance verification problem of "how much leakage is reduced" and the mechanistic analysis problem of "why leakage can be suppressed", providing dual support for the optimization of turbulent structures.

[0081] 2. This application solves the industry problem of the inability to directly visualize and observe leakage flow in micron-level gaps of CO2 compressors and the inability to reproduce experimental results to real operating conditions by designing an equivalent model with proportional scaling and a complete equivalent mapping relationship and compensation for real gas effects. By scaling up proportionally, it not only solves the problems of light paths not being able to penetrate the real gap and the flow field not being able to be observed, but also ensures that the flow field in the equivalent gap deviates from the leakage flow field in the real compressor gap by ≤5% through equivalent control of multiple flow criteria. The experimental results can be accurately mapped to real operating conditions and have direct engineering guidance value.

[0082] 3. This application achieves simultaneous observation of the flow field within the gap and downstream of the gap across the entire range, filling a gap in existing technologies. Through a schlieren optical path design adapted to the cavity coaxially, it can fully cover the entire process of the leakage jet from its generation within the gap to its downstream development, clearly capturing core flow field characteristics such as shear layer evolution, vortex structure shedding, and shock wave distribution. It can completely analyze the entire process law of leakage flow, providing a new experimental basis for the precise design of leakage suppression structures.

[0083] 4. This application uses high-precision polyethylene gaskets to control the gap size, eliminating the need for complex high-precision adjustment mechanisms. The structure is simple and easy to install, enabling rapid batch testing of different gap sizes and different turbulence structures, significantly improving experimental efficiency and shortening the R&D optimization cycle of turbulence suppression structures.

[0084] 5. This application, through its high- and low-pressure dual-stabilizing chamber design, can control pressure fluctuations under experimental conditions within ±0.05MPa, ensuring high stability of the experimental conditions. The flow measurement error is ≤0.2%FS, accurately distinguishing minute performance differences in different structural parameters, resulting in good experimental repeatability and high data reliability. 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 related data must comply with relevant regulations and be authorized by the owner of the corresponding device.

[0085] 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.

[0086] 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 visualization experimental apparatus for gap leakage in a carbon dioxide scroll compressor, characterized in that, The CO2 scroll compressor gap leakage visualization experimental device includes a working fluid supply module, a working condition adjustment module, a visualization experimental module, a flow test module, and a data acquisition and processing module. The working fluid supply module, the working condition adjustment module, the visualization experimental module, and the flow test module are connected sequentially along the working fluid flow direction. The visualization experimental module includes a visualization experimental chamber and a Z-shaped transmission schlieren visualization module. The schlieren visualization module is coaxially adapted to the visualization experimental chamber and is used to acquire transient schlieren images of CO2 leakage flow inside the equivalent gap and in the downstream region of the gap. The working condition adjustment module is used to stabilize the inlet and outlet pressures, working fluid temperature, and working fluid flow rate of the visualization experimental chamber. The flow test module is used to acquire gap leakage flow data.

2. The experimental apparatus for visualizing gap leakage in a carbon dioxide scroll compressor according to claim 1, characterized in that, The working fluid supply module includes a CO2 cylinder, a pressure reducing valve, and a check valve; the operating condition adjustment module includes a high-pressure stabilizing chamber, a low-pressure stabilizing chamber, a back pressure valve, an outlet control valve, and a constant temperature control module; the flow test module is a flow meter; the data acquisition and processing module is used to simultaneously process gap leakage flow data and CO2 leakage flow transient schlieren images to complete flow field feature analysis and experimental result reconstruction.

3. The experimental apparatus for visualizing gap leakage in a carbon dioxide scroll compressor according to claim 1, characterized in that, Optical windows are coaxially opened on opposite side walls of the visualization experimental cavity, and quartz windows are sealed and fixed inside the optical windows; the nominal height of the equivalent gap of the visualization experimental cavity is controlled by polyethylene gaskets of different thicknesses.

4. The experimental apparatus for visualizing gap leakage in a carbon dioxide scroll compressor according to claim 1, characterized in that, The schlieren visualization module has a double concave mirror structure. Its optical path is completely coaxial with the two quartz glass windows of the visualization experimental chamber. The optical path passes perpendicularly through the equivalent gap flow channel, covering the entire flow field region inside the gap and downstream of the gap. The schlieren visualization module includes a light source, a high-speed camera, two concave mirrors, and a knife-edge assembly.

5. A method for visualizing gap leakage in a carbon dioxide scroll compressor based on the visual experimental apparatus for gap leakage in a carbon dioxide scroll compressor according to any one of claims 1-4, characterized in that, The experimental method for visualizing gap leakage in a carbon dioxide scroll compressor includes: S1: For the target CO2 scroll compressor's leakage gap, the three-dimensional leakage channel is expanded into a two-dimensional parallel plate gap model along the main leakage direction. The two-dimensional parallel plate gap model is scaled up proportionally by a set factor to determine the geometric parameters of the equivalent experiment. Based on the basic control equations of fluid mechanics, the flow characteristic parameters of the prototype under real operating conditions are calculated. The geometric amplification ratio and operating temperature are fixed on the two-dimensional parallel plate gap model side. The optimal operating parameters of the two-dimensional parallel plate gap model are determined based on minimizing the deviation of the flow similarity criterion parameters between the two-dimensional parallel plate gap model and the prototype. The actual operating conditions of the target compressor are matched to determine the inlet and outlet pressures and working fluid temperature parameters of the experiment, so that the deviations of the Reynolds number and Mach number of the CO2 leakage flow in the equivalent gap from the flow characteristic parameters in the actual compressor gap are within the set range. S2: Construct a visualization experimental device for gap leakage in a carbon dioxide scroll compressor; S3: Calibrate the gap dimensions and flow measurement module of the visualization experimental chamber; perform high-pressure holding test on the experimental system; S4: Adjust the inlet and outlet pressures of the visualization experimental chamber to the target value, stabilize the working fluid temperature through the constant temperature control module, and determine that the steady-state experimental condition has been reached after the system operating conditions have reached the set time period and the peak-to-peak pressure fluctuation, peak-to-peak temperature fluctuation, and peak-to-peak flow fluctuation meet the set steady-state operating conditions. S5: Install the control group sample into the fixed plate mounting position of the visualization experimental chamber. Within the set time, collect the gap leakage flow data and simultaneously collect the transient schlieren images of CO2 leakage flow inside the equivalent gap and downstream region through the schlieren visualization module. Complete no less than the set number of repeated experiments. Replace the experimental group sample and repeat the above acquisition operation under the same working conditions to complete the test of all samples. The control group sample is a smooth plate sample, and the experimental group sample is a sample with a 20x magnified turbulence suppression structure to be tested. S6: By adjusting the inlet and outlet pressures, working fluid temperature, and nominal clearance height of the visualization experimental chamber, the full operating conditions and common clearance size range of the CO2 scroll compressor are covered. Repeat steps S4-S5 to complete the extended experiment with multiple operating conditions and multiple clearance sizes. S7: Perform statistical analysis on the gap leakage flow data, calculate the leakage suppression efficiency of the test turbulence suppression structure in the experimental group samples; process the transient schlieren image of CO2 leakage flow to obtain the density field distribution of the leakage flow, analyze the flow field characteristic parameters, and clarify the leakage suppression mechanism of the test turbulence suppression structure; restore the experimental results to the real compressor operating conditions through equivalent mapping relationship to complete the verification of experimental results.

6. The experimental method for visualizing clearance leakage in a carbon dioxide scroll compressor according to claim 5, characterized in that, The equivalent clearance nominal height, flow channel length, and flow channel width after proportional scaling are all multiples of the corresponding dimensions of the actual compressor clearance. The relative dimensions of the turbulence suppression structure under test are completely consistent with the relative dimensions of the structure inside the actual compressor. The relative dimensions are the ratio of the structure depth to the clearance nominal height, the ratio of the structure width to the clearance nominal height, and the ratio of the structure spacing to the clearance nominal height.

7. The experimental method for visualizing clearance leakage in a carbon dioxide scroll compressor according to claim 5, characterized in that, The materials of the control sample and the experimental sample are the same as those of the target compressor scroll disk; the turbulence structure of the experimental sample is processed by micron-level laser etching or precision milling, with a processing size error of ≤±1mm.

8. The experimental method for visualizing clearance leakage in a carbon dioxide scroll compressor according to claim 5, characterized in that, Processing the transient schlieren image of the CO2 leakage flow specifically includes: processing the transient schlieren image of the CO2 leakage flow using the background schlieren method; The flow field characteristic parameters include the shear layer thickness of the leaking jet, the vortex core size, the vortex shedding frequency, and the shock wave spacing.

9. The experimental method for visualizing clearance leakage in a carbon dioxide scroll compressor according to claim 5, characterized in that, The experimental results were verified by comparing them with the three-dimensional CFD simulation results based on the GERG-2008 real gas equation of state, ensuring that the deviation between the experimental results and the simulation results did not exceed 8%. The equivalent mapping relationship is based on the dual equivalence principle of geometric similarity + flow similarity, including a one-to-one correspondence of geometric parameters, flow similarity criterion parameters, physical property parameters, and operating condition parameters, and a wall roughness correction coefficient is introduced. and end effect correction coefficient Perform accuracy compensation.

10. The experimental method for visualizing clearance leakage in a carbon dioxide scroll compressor according to claim 9, characterized in that, The physical properties were calculated based on the GERG-2008 real gas equation of state, including compressibility factor, density, dynamic viscosity, thermal conductivity, specific heat at constant pressure, and adiabatic index.

Images