A method for calculating the peak pressure of supercritical CO2 phase transition

Abstract

The invention discloses a method for calculating supercritical CO2 phase change peak pressure, which belongs to the technical field of supercritical CO2 phase change calculation, and comprises the following steps: based on the thin-walled cylinder theory, constructing a supercritical CO2 phase change peak pressure calculation formula according to the parameters of the fracturing tube; performing a supercritical CO2 phase change pressure test experiment to obtain peak pressure data, and verifying the supercritical CO2 phase change peak pressure calculation formula through the peak pressure data; and calculating the supercritical CO2 phase change peak pressure through the verified supercritical CO2 phase change peak pressure calculation formula. The invention solves the problem that the one-time supercritical CO2 phase change peak pressure calculation currently used for engineering blasting is not accurate enough.

Description

Technical Field

[0001] The invention belongs to the technical field of supercritical CO2 phase change calculation, and in particular relates to a method for calculating supercritical CO2 phase change peak pressure. Background Art

[0002] Supercritical CO2 phase change is a new type of blasting technology. This technology uses a heating tube to quickly change the liquid CO2 at a certain pressure and temperature into a liquid-gas phase, and the volume expands 600 times instantly, thereby generating a strong physical pressure (above 200MPa). It is a green and ecological blasting technology. In practical applications, this technology lacks monitoring of the blasting pressure, and the calculation of the phase change peak pressure is not accurate enough, so further theoretical analysis and verification are needed.

[0003] The main problem with existing technologies in blasting applications is that the progress of engineering applications is faster than theoretical research, resulting in the calculation of construction parameters, especially the peak pressure of supercritical CO2 phase change, which is not accurate enough, and most key influencing parameters cannot be reflected in the calculation method. Summary of the invention

[0004] The invention provides a method for calculating supercritical CO2 phase change peak pressure, which solves the problem that the one-time supercritical CO2 phase change peak pressure calculation currently used for engineering blasting is not accurate enough.

[0005] In order to solve the above technical problems, the technical solution of the present invention is: a method for calculating the supercritical CO2 phase change peak pressure, comprising the following steps:

[0006] S1. Based on the thin-walled cylinder theory and the fracture tube parameters, the calculation formula for the supercritical CO2 phase change peak pressure is constructed;

[0007] S2. Conduct a supercritical CO2 phase change pressure test to obtain peak pressure data, and verify the supercritical CO2 phase change peak pressure calculation formula through the peak pressure data;

[0008] S3. Calculate the supercritical CO2 phase change peak pressure using the verified supercritical CO2 phase change peak pressure calculation formula.

[0009] Furthermore, the specific steps of step S1 are:

[0010] S11. Based on the thin-walled cylinder theory, the fracturing tube is regarded as a thin-walled cylinder, and a fracturing tube mechanical model is constructed according to the uniformly distributed supercritical CO2 phase transition peak pressure p, the instantaneous radius r of the fracturing tube, and the instantaneous wall thickness d of the fracturing tube;

[0011] S12. Based on the mechanical model of cracked tube, determine the principal stress-strain state of the thin-walled cylinder when it is in the plastic limit state;

[0012] S13. Describe the stress-strain relationship of cracked pipe steel when subjected to blasting pressure by pure power rate curve;

[0013] S14, Substitute the principal stress-strain state into the three-shear unified strength criterion to obtain the equivalent stress;

[0014] S15. According to the stress-strain relationship and the equivalent stress, the explosion internal pressure of the thin-walled cylinder is obtained, wherein the calculation formula of the explosion internal pressure of the thin-walled cylinder is the calculation formula of the supercritical CO2 phase change peak pressure.

[0015] Furthermore, the expression of the principal stress-strain state in step S12 is:

[0016]

[0017] Among them, σ1, σ2 and σ3 represent the first principal stress, the second principal stress and the third principal stress respectively, σ θ , σ z and σ r They represent the hoop stress, axial stress and radial stress of the thin-walled cylinder, ε1, ε2 and ε3 represent the first principal strain, the second principal strain and the third principal strain, respectively. θ , ε z and ε r They represent the hoop strain, axial strain and radial strain of the thin-walled cylinder respectively, r0 represents the initial average radius of the thin-walled cylinder, and d0 represents the initial wall thickness of the thin-walled cylinder.

[0018] Furthermore, the expression of the stress-strain relationship in step S13 is:

[0019] σ=Kε n

[0020]

[0021] σ s =e n σ t

[0022]

[0023] Where σ and ε represent the uniaxial true stress and uniaxial true strain under simple tension, K represents the strength parameter, n represents the strain hardening exponent, and σ s Indicates the tensile yield limit of the pipe, σ t Indicates the engineering ultimate tensile strength of the pipe.

[0024] Furthermore, the expression of the three-shear unified strength criterion in step S14 is:

[0025] (1+b)(σ1-σ3)σ t =(ασ1-σ3)(σ1-σ3)+b(ασ1-σ2)(σ1-σ2)+b(ασ2-σ3)(σ2-σ3)

[0026] α=σ t / σ c

[0027] 0≤b≤α / (2+α)

[0028] Among them, α represents the tensile and compressive strength ratio of the material, b represents the influence of the principal stress on the material failure, and σ c Indicates the compressive strength of steel.

[0029] Furthermore, the expression of the effective stress in step S14 is:

[0030]

[0031] Among them, σ eq represents equivalent stress;

[0032] The calculation formula of the explosion internal pressure of the thin-walled cylinder in step S15 is:

[0033]

[0034] Among them, P b Indicates the bursting internal pressure of a thin-walled cylinder.

[0035] Furthermore, the specific steps of conducting the supercritical CO2 phase change pressure test experiment include:

[0036] A1. Use a drill to drill a hole on the fracture pipe, and install the pressure sensor in a threaded form based on the drilling position;

[0037] A2. Use a steel bracket to fix the liquid storage tube, assemble the energy release plate, sealing gasket, release head, heating tube and filling head in sequence, and perform an airtightness check;

[0038] A3. Use an ohmmeter to test the circuit connectivity between the heating tube and the filling head;

[0039] A4. Connect the CO2 filling system and the filling head through the filling hose, and set the booster pump and chiller parameters through the display screen;

[0040] A5. Connect the detonating wire, start the data acquisition system, and complete the detonation through the detonator;

[0041] A6. Obtain peak pressure data through the data acquisition system and complete the supercritical CO2 phase change pressure test.

[0042] Furthermore, the specific steps of verifying the calculation formula for supercritical CO2 phase change peak pressure include:

[0043] B1. Input the test parameters of the supercritical CO2 phase change pressure test into the supercritical CO2 phase change peak pressure calculation formula to calculate and obtain the supercritical CO2 phase change peak pressure;

[0044] B2. Verify the calculation formula of supercritical CO2 phase change peak pressure through peak pressure data and supercritical CO2 phase change peak pressure.

[0045] The beneficial effects of the present invention are: (1) according to the actual failure mode of the one-time fracturing pipe commonly used in actual engineering, the calculation formula of the supercritical CO2 phase change peak pressure is derived based on the thin-walled cylinder theory, which can accurately calculate the pressure change and enhance the understanding of the behavior of the engineering system;

[0046] (2) The supercritical CO2 phase change pressure test experiment was carried out to obtain the phase change pressure time curve and verify the pressure calculation model to ensure that the model can truly reflect the actual situation of the supercritical CO2 phase change. The actual test data provides a reliable basis for further research and application, which helps to improve the practical application value of the model. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The figure is a flow chart of the method for calculating the supercritical CO2 phase change peak pressure of the present invention.

[0048] Figure 2 Schematic diagram of the mechanical model of the fracturing tube of the present invention, (a) is a schematic diagram of the fracturing tube failure obtained according to the geometric conditions and failure mode of the fracturing tube, (b) is the overall stress mode of the fracturing tube, and (c) is the thin-wall stress mode of the fracturing tube.

[0049] Figure 3 This is a system structure diagram of the supercritical CO2 phase change pressure test experiment of the present invention.

[0050] Figure 4 It is a structural diagram of the fracturing tube of the present invention.

[0051] Figure 5 This is a supercritical CO2 phase change peak pressure-time curve diagram of the present invention.

[0052] Among them, 1-computer, 2-shock wave tester, 3-initiator, 4-connecting pipelines and valves, 5-boosting pump, 6-chiller, 7-display, 8-temperature and pressure control center, 9-workbench, 10-CO2 gas cylinder, 11-pressure sensor, 12-fracture tube, 13-fixed bracket, 12-1-inflating head, 12-2-heating tube, 12-3-liquid storage tube, 12-4-sealing gasket, 12-5-energy release plate and 12-6-release head. DETAILED DESCRIPTION

[0053] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

[0054] Example

[0055] like Figure 1 As shown, the present invention provides a method for calculating the supercritical CO2 phase change peak pressure, comprising the following steps:

[0056] S1. Based on the thin-walled cylinder theory and the fracture tube parameters, the calculation formula for the supercritical CO2 phase change peak pressure is constructed;

[0057] S2. Conduct a supercritical CO2 phase change pressure test to obtain peak pressure data, and verify the supercritical CO2 phase change peak pressure calculation formula through the peak pressure data;

[0058] S3. Calculate the supercritical CO2 phase change peak pressure using the verified supercritical CO2 phase change peak pressure calculation formula.

[0059] In this embodiment, the supercritical CO2 shock pressure, as the driving force of the surface vibration, has a direct impact on the vibration velocity, so an accurate description of the pressure is crucial for the derivation of the vibration velocity. Previous studies have mostly used the shear failure formula to calculate the peak pressure of the fracture pipe blasting, which is not suitable for on-site blasting pressure calculation.

[0060] Therefore, according to the geometric conditions of the fractured pipe (r / d ≥ 20) and the failure mode, such as Figure 2 As shown in (a), it is regarded as a closed large-diameter thin-walled cylinder, and the pressure formula applicable to on-site supercritical CO2 phase change explosion is derived based on it. The mechanical model of the fracture tube is as follows: Figure 2 (b) and (c), where P is the uniformly distributed supercritical CO2 phase change peak pressure, in MPa, and the instantaneous radius r of the fracturing tube and the instantaneous wall thickness d of the fracturing tube are both in mm.

[0061] The specific steps of step S1 are:

[0062] S11. Based on the thin-walled cylinder theory, the fracturing tube is regarded as a thin-walled cylinder, and a fracturing tube mechanical model is constructed according to the uniformly distributed supercritical CO2 phase transition peak pressure p, the instantaneous radius r of the fracturing tube, and the instantaneous wall thickness d of the fracturing tube;

[0063] S12. Based on the mechanical model of cracked tube, determine the principal stress-strain state of the thin-walled cylinder when it is in the plastic limit state;

[0064] S13. Describe the stress-strain relationship of cracked pipe steel when subjected to blasting pressure by pure power rate curve;

[0065] S14, Substitute the principal stress-strain state into the three-shear unified strength criterion to obtain the equivalent stress;

[0066] S15. According to the stress-strain relationship and the equivalent stress, the explosion internal pressure of the thin-walled cylinder is obtained, wherein the calculation formula of the explosion internal pressure of the thin-walled cylinder is the calculation formula of the supercritical CO2 phase change peak pressure.

[0067] In this embodiment, under the action of the explosion internal pressure, an infinitesimal differential unit of the outer wall of a thin-walled cylinder is considered, and its stress-strain state is expressed in a cylindrical coordinate system (r, θ, z). When the thin-walled cylinder is in the plastic limit state, the Barlow formula and finite strain theory are used to determine its principal stress-strain state.

[0068] The expression of the principal stress-strain state in step S12 is:

[0069]

[0070] Among them, σ1, σ2 and σ3 represent the first principal stress, the second principal stress and the third principal stress respectively, σ θ , σ z and σ r They represent the hoop stress, axial stress and radial stress of the thin-walled cylinder, ε1, ε2 and ε3 represent the first principal strain, the second principal strain and the third principal strain, respectively. θ , ε z and ε r They represent the hoop strain, axial strain and radial strain of the thin-walled cylinder respectively, r0 represents the initial average radius of the thin-walled cylinder, and d0 represents the initial wall thickness of the thin-walled cylinder.

[0071] In this embodiment, considering the influence of the strain hardening phenomenon of the material when the material reaches the limit state under the action of internal pressure, a pure power law curve is selected to describe the stress-strain relationship of the fracture pipe steel when it is subjected to the blasting pressure as follows.

[0072] The expression of the stress-strain relationship in step S13 is:

[0073] σ=Kε n

[0074]

[0075] σ s =e n σ t

[0076]

[0077] Where σ and ε represent the uniaxial true stress and uniaxial true strain under simple tension, K represents the strength parameter, n represents the strain hardening exponent, and σ s Indicates the tensile yield limit of the pipe, σ t Indicates the engineering ultimate tensile strength of the pipe.

[0078] In this embodiment, the three-shear unified strength criterion is introduced by considering the unequal tensile and compressive strength characteristics of steel (SD effect) and the influence of intermediate principal stress.

[0079] The expression of the three-shear unified strength criterion in step S14 is:

[0080] (1+b)(σ1-σ3)σ t =(ασ1-σ3)(σ1-σ3)+b(ασ1-σ2)(σ1-σ2)+b(ασ2-σ3)(σ2-σ3)

[0081] α=σ t / σ c

[0082] 0≤b≤α / (2+α)

[0083] Among them, α represents the tensile and compressive strength ratio of the material, b represents the influence of the principal stress on the material failure, and σ c Indicates the compressive strength of steel.

[0084] In this embodiment, the stress state of the thin-walled cylinder is substituted into the three-shear unified strength criterion to obtain the equivalent stress as follows.

[0085] The expression of the effective stress in step S14 is:

[0086]

[0087] Among them, σ eq represents equivalent stress;

[0088] In this embodiment, in the plastic deformation stage, the material volume is incompressible, so ε1+ε2+ε3=0. Substituting this formula into the principal stress-strain state, we get

[0089] Based on the assumption of plastic work, we can get: eq ε eq =σε=σ1ε1.

[0090] The formula σ eq ε eq =σε=σ1ε1 and equivalent stress σ eq Combined, the expression of the first principal strain ε1 is obtained as

[0091] Substituting the expression of the first principal strain ε1 into In the equation, the geometric relationship of the thin-walled cylinder is obtained as follows:

[0092] Simultaneous stress-strain relationship, equivalent stress σ eq And the geometric relationship of the thin-walled cylinder, the bursting internal pressure of the thin-walled cylinder is obtained as:

[0093] Derivation of the explosion internal pressure of a thin-walled cylinder according to the plastic instability condition: The equivalent effect can be obtained as:

[0094] Will Substituting it into the explosion internal pressure of the thin-walled cylinder, the final explosion internal pressure of the thin-walled cylinder is obtained, which is the calculation formula for the supercritical CO2 phase change peak pressure.

[0095] The calculation formula of the explosion internal pressure of the thin-walled cylinder in step S15 is:

[0096]

[0097] Among them, P b Indicates the bursting internal pressure of a thin-walled cylinder.

[0098] The specific steps of the supercritical CO2 phase change pressure test experiment include:

[0099] A1. Use a drill to drill a hole on the fracture pipe, and install the pressure sensor in a threaded form based on the drilling position;

[0100] A2. Use a steel bracket to fix the liquid storage tube, assemble the energy release plate, sealing gasket, release head, heating tube and filling head in sequence, and perform an airtightness check;

[0101] A3. Use an ohmmeter to test the circuit connectivity between the heating tube and the filling head;

[0102] A4. Connect the CO2 filling system and the filling head through the filling hose, and set the booster pump and chiller parameters through the display screen;

[0103] A5. Connect the detonating wire, start the data acquisition system, and complete the detonation through the detonator;

[0104] A6. Obtain peak pressure data through the data acquisition system and complete the supercritical CO2 phase change pressure test.

[0105] The specific steps of verifying the supercritical CO2 phase change peak pressure calculation formula include:

[0106] B1. Input the test parameters of the supercritical CO2 phase change pressure test into the supercritical CO2 phase change peak pressure calculation formula to calculate and obtain the supercritical CO2 phase change peak pressure;

[0107] B2. Verify the calculation formula of supercritical CO2 phase change peak pressure through peak pressure data and supercritical CO2 phase change peak pressure.

[0108] In this embodiment, the system structure of the supercritical CO2 phase change pressure test experiment is as follows: Figure 3-4 As shown, the fracturing tube 12 is fixed by a fixing bracket 13, the pressure sensor 11 is installed on the liquid storage tube 12-3 of the fracturing tube 12, the shock wave tester 2 is connected to the pressure sensor 11 and the computer 1 respectively, the detonator 3 is connected to one end of the fracturing tube 12, and the temperature and pressure control center 8, the display 7, the chiller 6, the booster pump 5 and the connecting pipeline and valve 4 are placed on the workbench 9, and the connecting pipeline and valve 4 are also connected to one end of the fracturing tube 12, and the CO2 gas cylinder 10 is connected to the booster pump 5. The fracturing tube 12 is assembled in sequence by 12-1-inflating head, 12-2-heating tube, 12-3-liquid storage tube, 12-4-sealing gasket, 12-5-energy release plate and 12-6-release head.

[0109] First, use a drill to drill a hole in the fracturing tube 12, then install the pressure sensor 11 in the form of a thread, and then weld around the pressure sensor 11 for further fixation. Use a steel bracket to fix the liquid storage tube 12-3, and then use tools such as a wrench to assemble the energy release plate 12-5, the sealing gasket 12-4, the release head 12-6, the heating tube 12-2 and the filling head 12-1 in sequence. After assembly, perform a pre-inflation test. After the air tightness inspection of the fracturing tube is completed, use an ohmmeter to test the circuit connectivity between the heating tube 12-2 and the filling head 12-1 to ensure that the strong current of the detonator 3 can smoothly pass through the filling head 12-1 and excite the heating tube 12-2. Use an inflatable hose to connect the CO2 filling system and the filling head, and set the parameters of the booster pump 5 and the chiller 6 through the display screen 7 to control the filling pressure and temperature of CO2. Connect the detonation wire and start the data acquisition system at the same time, complete the detonation through the detonator 3, and obtain the supercritical CO2 phase change peak pressure-time curve, that is, the peak pressure data.

[0110] In this embodiment, the steel type of the fracturing pipe used in the test is Q235 steel, whose elastic modulus E=207Gpa, yield strength is 235MPa, tensile strength is 370MPa, engineering ultimate tensile strength is 500MPa, the initial radius r0 of the fracturing pipe is 11mm, and the initial thickness d0 of the fracturing pipe under each working condition is 1.9mm, 1.9mm, 2.6mm, 2.6mm, 2.6mm, 3.4mm, 3.4mm and 3.4mm respectively. The supercritical CO2 phase change peak pressure-time curve is obtained as shown in Figure 5 shown.

[0111] Considering that the three-shear unified strength criterion can be degenerated into or approximate multiple existing yield criteria, for example, when α = 1, b = 0, it can be degenerated into the Tresca yield criterion; when α = 1, b = 1 / 3, it can be approximated into the Von-Mises yield criterion.

[0112] Therefore, when the radius of the fracturing tube is 11 mm and the material used is Q235 steel, the peak pressure value of the supercritical CO2 phase change obtained in the experiment is used as a reference, and the theoretical pressure calculation value degenerated into Tresca and the theoretical pressure calculation value approximating Von-Mises are used for comparison. The comparison is shown in Table 1. Table 1 is a statistical table of the comparison results between the test value and the theoretical value of the bursting pressure of the fracturing tube.

[0113] Table 1

[0114]

[0115]

[0116] Among them, P s , P b1 and P b2They represent the experimental value of the bursting pressure of a thin-walled cylinder, the calculated value of the theoretical pressure degenerated into Tresca, and the calculated value of the theoretical pressure approximating Von-Mises.

[0117] It can be seen from Table 1 that the average ratios of the burst pressure calculated by the Tresca yield criterion and the Von-Mises yield criterion to the experimental value are 0.828 and 1.049, respectively. The latter obviously has higher calculation accuracy and is more suitable for the calculation of the peak pressure of supercritical CO2 phase change.

[0118] In summary, the present invention derives a calculation formula for the supercritical CO2 phase change peak pressure based on the thin-walled cylinder theory according to the actual failure mode of the disposable fracturing tube commonly used in actual engineering, which can accurately calculate the pressure change. At the same time, the pressure calculation model is verified to ensure that the model can truly reflect the actual situation of the supercritical CO2 phase change. The actual test data provides a reliable basis for further research and application, which helps to improve the practical application value of the model.

Claims

1. A method for calculating supercritical CO2 phase change peak pressure, characterized in that: The following steps are involved: S1. Based on the thin-walled cylinder theory and the fracture tube parameters, the calculation formula for the supercritical CO2 phase change peak pressure is constructed; S2. Conduct a supercritical CO2 phase change pressure test to obtain peak pressure data, and verify the supercritical CO2 phase change peak pressure calculation formula through the peak pressure data; S3. Calculate the supercritical CO2 phase change peak pressure using the verified supercritical CO2 phase change peak pressure calculation formula; The specific steps of step S1 are: S11. Based on the thin-walled cylinder theory, the fracturing tube is regarded as a thin-walled cylinder, and a fracturing tube mechanical model is constructed according to the uniformly distributed supercritical CO2 phase transition peak pressure p, the instantaneous radius r of the fracturing tube, and the instantaneous wall thickness d of the fracturing tube; S12. Based on the mechanical model of cracked tube, determine the principal stress-strain state of the thin-walled cylinder when it is in the plastic limit state; S13. Describe the stress-strain relationship of cracked pipe steel when subjected to blasting pressure by pure power rate curve; S14, Substitute the principal stress-strain state into the three-shear unified strength criterion to obtain the equivalent stress; S15. According to the stress-strain relationship and the equivalent stress, the bursting internal pressure of the thin-walled cylinder is obtained, wherein the calculation formula of the bursting internal pressure of the thin-walled cylinder is the calculation formula of the supercritical CO2 phase change peak pressure; The expression of the principal stress-strain state in step S12 is: Among them, σ1, σ2 and σ3 represent the first principal stress, the second principal stress and the third principal stress respectively, σ θ , σ z and σ r They represent the hoop stress, axial stress and radial stress of the thin-walled cylinder, ε1, ε2 and ε3 represent the first principal strain, the second principal strain and the third principal strain, respectively. θ , ε z and ε r They represent the hoop strain, axial strain and radial strain of the thin-walled cylinder respectively, r0 represents the initial average radius of the thin-walled cylinder, and d0 represents the initial wall thickness of the thin-walled cylinder; The expression of the stress-strain relationship in step S13 is: σ=Kε n s s =e n s t Where σ and ε represent the uniaxial true stress and uniaxial true strain under simple tension, K represents the strength parameter, n represents the strain hardening exponent, and σ s Indicates the tensile yield limit of the pipe, σ t Indicates the engineering ultimate tensile strength of the pipe; The expression of the three-shear unified strength criterion in step S14 is: (1+b)(σ1-σ3)σ t =(ασ1-σ3)(σ1-σ3)+b(ασ1-σ2)(σ1-σ2)+b(ασ2-σ3)(σ2-σ3) a = s t / s c 0≤b≤α / (2+α) Among them, α represents the tensile and compressive strength ratio of the material, b represents the influence of the principal stress on the material failure, and σ c Indicates the compressive strength of steel; The expression of the effective stress in step S14 is: Among them, σ eq represents equivalent stress; The calculation formula of the explosion internal pressure of the thin-walled cylinder in step S15 is: Among them, P b Indicates the bursting internal pressure of a thin-walled cylinder.

2. The method for calculating supercritical CO2 phase change peak pressure according to claim 1, characterized in that: The specific steps of the supercritical CO2 phase change pressure test experiment include: A1. Use a drill to drill a hole on the fracture pipe, and install the pressure sensor in a threaded form based on the drilling position; A2. Use a steel bracket to fix the liquid storage tube, assemble the energy release plate, sealing gasket, release head, heating tube and filling head in sequence, and perform an airtightness check; A3. Use an ohmmeter to test the circuit connectivity between the heating tube and the filling head; A4. Connect the CO2 filling system and the filling head through the filling hose, and set the booster pump and chiller parameters through the display screen; A5. Connect the detonating wire, start the data acquisition system, and complete the detonation through the detonator; A6. Obtain peak pressure data through the data acquisition system and complete the supercritical CO2 phase change pressure test.

3. The method for calculating the supercritical CO2 phase change peak pressure according to claim 2, characterized in that: The specific steps of verifying the supercritical CO2 phase change peak pressure calculation formula include: B1. Input the test parameters of the supercritical CO2 phase change pressure test into the supercritical CO2 phase change peak pressure calculation formula to calculate and obtain the supercritical CO2 phase change peak pressure; B2. Verify the calculation formula of supercritical CO2 phase change peak pressure through peak pressure data and supercritical CO2 phase change peak pressure.

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