Design and calculation method of mechanical seal end face specific pressure

Abstract

The application discloses a design calculation method of mechanical seal end face specific pressure, and steps are as follows: obtaining material parameters, end face topography parameters, structure parameters and working condition parameters of dynamic and static rings of the mechanical seal; determining the maximum height of the contact interface gap and the initial porosity of the dynamic and static rings; determining the compression amount of the sealing interface; determining the deformation state of the sealing interface; determining the first end face specific pressure under the non-percolation critical contact condition of the sealing interface; determining the second end face specific pressure of the sealing interface; and determining the design range of the mechanical seal end face specific pressure according to the size of the first end face specific pressure and the second end face specific pressure. The application can change the disadvantage that the existing design mechanical seal end face specific pressure parameter is simply relied on the experience value, can ensure that the selected end face contact pressure is more scientific and reasonable, can guarantee that the mechanical seal end face does not leak, can realize that the wear rate of the mechanical seal end face does not exceed the standard, and provides important guarantee for realizing zero-leakage long-life operation of the mechanical seal device.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of mechanical seal, and particularly relates to a design calculation method of mechanical seal end face specific pressure. BACKGROUND

[0002] Mechanical seal is the main shaft sealing form of rotating equipment such as centrifugal compressor, centrifugal pump and steam turbine, and its main performance parameters include leakage rate and wear life. In addition to working condition parameters, the most critical factor affecting the performance of mechanical seal is the mechanical parameter of end face specific pressure. Increasing the end face specific pressure is beneficial to reducing the porosity between the sealing surfaces and achieving zero leakage, but excessive contact specific pressure of the sealing surface will increase the wear of the end face of the dynamic and static ring, and shorten the service life of the mechanical seal.

[0003] In the book of Chemical Seal Technology, it is pointed out that in pump mechanical seal, for the built-in mechanical seal, the end face specific pressure is generally selected as 0.3-0.5 MPa; the end face specific pressure of the external mechanical seal is generally selected as 0.15-0.4 MPa; for the medium with large material viscosity, the end face specific pressure is generally selected as 0.5-0.7 MPa, and the smaller end face specific pressure value is selected for the material with poor lubricity and easy evaporation, generally 0.25-0.45 MPa. In the "10th part of lubrication and sealing" of Mechanical Design Manual, the end face specific pressure range of mechanical seal under different media and installation modes is given. For a long time, the end face specific pressure parameter design of mechanical seal has always relied on the experience value in the above literature, and lacks theoretical basis, which seriously limits the better performance of mechanical seal. SUMMARY

[0004] In view of the above shortcomings, the present application aims to provide a design calculation method of mechanical seal end face specific pressure, so as to solve the problem of the lack of existing mechanical seal end face specific pressure design method, ensure that the mechanical seal realizes zero leakage at the same time, make the end face wear rate meet the requirements, and improve the service life and sealing performance of the mechanical seal. The specific scheme is as follows:

[0005] A design calculation method of mechanical seal end face specific pressure, comprising the following steps:

[0006] S1, obtaining the material parameters, end face topography parameters, structure parameters and working condition parameters of the dynamic and static rings of the mechanical seal;

[0007] S2, determining the maximum height of the contact interface gap and the initial porosity of the dynamic and static rings according to the end face topography parameters of the dynamic and static rings;

[0008] S3, determining the compression amount of the sealing interface from the non-percolation critical contact condition of the contact interface and the maximum height of the contact interface gap and the initial porosity in step S2;

[0009] S4, determining the deformation state of the sealing interface according to the compression amount of the sealing interface;

[0010] S5, determining the first end face specific pressure of the sealing interface under the non-percolation critical contact condition according to the deformation state of the sealing interface;

[0011] S6, determining the second end face specific pressure of the sealing interface according to the material parameters of the dynamic and static rings and the critical wear rate of the mechanical seal;

[0012] S7, determining the design range of the end face specific pressure of the mechanical seal according to the size of the first end face specific pressure and the second end face specific pressure.

[0013] In this application, the dynamic and static ring is the general term of the dynamic ring and the static ring.

[0014] Specifically, the material parameters of the dynamic and static ring include the dynamic ring elastic modulus E1, the static ring elastic modulus E2, the dynamic ring material Poisson's ratio υ1, the static ring material Poisson's ratio υ2, the static ring wear coefficient k, the static ring hardness H, the dynamic ring yield limit σ1 and the static ring yield limit σ2.

[0015] The end face topography parameters of the dynamic and static ring include the dynamic ring fractal dimension D1, the static ring fractal dimension D2, the dynamic ring scale coefficient G1, the static ring scale coefficient G2, the maximum height R y1 of the dynamic ring surface profile and the maximum height R y2 of the static ring surface profile.

[0016] The structure parameters of the dynamic and static ring include the outer radius R o of the sealing surface and the inner radius R i .

[0017] The working condition parameters of the dynamic and static ring include the main shaft speed n.

[0018] Specifically, in step S2, the maximum height of the contact interface gap is represented by h, and h is calculated by formula (1):

[0019] h = 0.746 × (R y1 + R y2 ) (1)

[0020] The initial porosity is represented by φ0, and φ0 is calculated by formula (2):

[0021]

[0022] Where D is the equivalent fractal dimension of the dynamic and static ring, a Lm is the base area of the maximum microconvex body of the contact interface, l is the profile base diameter of the maximum microconvex body of the contact interface, and a is the microconvex body contact area.

[0023] D, a Lm and l are calculated by formula (21):

[0024]

[0025] wherein G is an equivalent dimension coefficient of the dynamic and static ring, G is calculated by formula (22) :

[0026]

[0027] Specifically, in step S3, the non-percolation critical contact condition of the contact interface refers to that the porosity of the contact interface of the dynamic and static ring reaches a critical porosity after pressure loading, the critical porosity is denoted by φ, and φ = 0.312; the porosity after pressure loading is denoted by φ, the compression amount of the sealing interface is denoted by δ, and δ is calculated by formula (3) :

[0028]

[0029] wherein φ0 is the initial porosity of the contact interface.

[0030] The above pressure loading refers to the state when the dynamic and static ring is loaded by the pressure generated by the sealing medium during the operation of the mechanical seal.

[0031] Specifically, in step S4, the deformation state of the sealing interface is divided into elastic deformation, elastic-plastic deformation and plastic deformation, and the specific steps of determining the deformation state of the sealing interface according to the compression amount of the sealing interface are as follows:

[0032] S401, calculate the elastic deformation critical compression amount and the plastic deformation critical compression amount of the sealing interface, the elastic deformation critical compression amount is denoted by δ ec , and δ ec is calculated by formula (4) :

[0033]

[0034] wherein E is the equivalent elastic modulus of the dynamic and static ring, σ y is the equivalent yield limit of the dynamic and static ring, and G is the equivalent dimension coefficient of the dynamic and static ring; E, σ y are specifically calculated by formula (41) :

[0035]

[0036] The plastic deformation critical compression amount is denoted by δ pc , and δ pc is calculated by formula (5) :

[0037]

[0038] wherein e is a natural constant;

[0039] S402, compare δ with δ ec and δ pcComparison is made, when delta is less than or equal to delta ec , then the sealing interface is elastically deformed, when delta ec is greater than delta pc , then the sealing interface is elastically and plastically deformed, when delta pc is greater than delta cmin , then the sealing interface is plastically deformed.

[0040] Specifically, in step S5, the first end face specific pressure is calculated by using formula (5) as shown in the following formula (6) : cmin

[0041]

[0042] Wherein a is the micro asperity contact area, a ec is the micro asperity elastic deformation critical contact area, a pc is the micro asperity plastic deformation critical contact area, E is the equivalent elastic modulus of the dynamic and static ring, G is the equivalent scale coefficient of the dynamic and static ring, and a, a ec and a pc are specifically calculated by using formula (61) as shown in the following formula (62) :

[0043]

[0044] Specifically, in step S6, the critical wear rate of the mechanical seal is represented by gamma, gamma = 0.02 mm / 100h, the second end face specific pressure is represented by p cmax , and p cmax is calculated by using formula (7) as shown in the following formula (8) :

[0045]

[0046] Wherein v is the sliding speed of the sealing surface, and v is calculated by using formula (71) as shown in the following formula (72) :

[0047]

[0048] When the design calculation method in the present application is used to design and calculate the mechanical seal end face contact pressure, first, the first end face specific pressure of the mechanical seal is determined according to the non-percolation critical contact condition of the contact interface, then the second end face specific pressure of the mechanical seal is determined according to the wear rate requirement of the mechanical seal, and finally the design range of the mechanical seal end face specific pressure is determined according to the size of the two. The present application can change the disadvantage of simply relying on the experience value when the existing mechanical seal end face specific pressure parameter is designed, can ensure that the selected end face contact pressure is more scientific and reasonable, can ensure that the mechanical seal end face does not leak, and can also realize that the wear rate of the mechanical seal end face does not exceed the standard, thereby providing an important guarantee for realizing zero leakage and long service life operation of the mechanical seal device. BRIEF DESCRIPTION OF DRAWINGS

[0049] ​Figure 1 Flow chart of the design and calculation method of the mechanical seal end face specific pressure in the present application. DETAILED DESCRIPTION

[0050] The design and calculation method of the mechanical seal end face specific pressure in the present application is described in detail below, please refer to Figure 1 , which comprises the following steps:

[0051] S1, obtaining the material parameters, end face topography parameters, structure parameters and working condition parameters of the mechanical seal dynamic and static rings.

[0052] In this embodiment, the dynamic and static rings are the general term of the dynamic ring and the static ring.

[0053] Among them, the material parameters of the dynamic and static rings include the dynamic ring elastic modulus E1, the static ring elastic modulus E2, the dynamic ring material Poisson's ratio υ1, the static ring material Poisson's ratio υ2, the static ring wear coefficient k, the static ring hardness H, the dynamic ring yield limit σ1 and the static ring yield limit σ2.

[0054] The end face topography parameters of the dynamic and static rings include the dynamic ring fractal dimension D1, the static ring fractal dimension D2, the dynamic ring scale coefficient G1, the static ring scale coefficient G2, the maximum height R y1 of the dynamic ring surface profile and the maximum height R y2 of the static ring surface profile.

[0055] The structure parameters of the dynamic and static rings include the outer radius R o and the inner radius R i of the sealing surface.

[0056] The working condition parameters of the dynamic and static rings include the main shaft speed n.

[0057] S2, determining the maximum height of the contact interface gap and the initial porosity of the dynamic and static rings according to the end face topography parameters of the dynamic and static rings.

[0058] Among them, the maximum height of the contact interface gap is represented by h, and h is calculated by formula (1):

[0059] h = 0.746 × (R y1 + R y2 ) (1)

[0060] The initial porosity is represented by φ0, and φ0 is calculated by formula (2):

[0061]

[0062] Among them, D is the equivalent fractal dimension of the dynamic and static rings, a Lm is the base area of the maximum microconvex body of the contact interface, l is the profile base diameter of the maximum microconvex body of the contact interface, and a is the microconvex body contact area.

[0063] D, a Lm and l are calculated according to formula (21) :

[0064]

[0065] wherein G is the equivalent dimension coefficient of the dynamic and static ring, and is calculated according to formula (22) :

[0066]

[0067] S3, determining the compression amount of the sealing interface according to the non-percolation critical contact condition of the contact interface and the maximum height of the contact interface gap and the initial porosity in step S2.

[0068] The non-percolation critical contact condition of the contact interface refers to that the porosity of the contact interface of the dynamic and static ring reaches a critical porosity after pressure loading, the critical porosity is denoted as φ, and φ = 0.312; the porosity after pressure loading is denoted as φ, the compression amount of the sealing interface is denoted as δ, and δ is calculated according to formula (3) :

[0069]

[0070] wherein φ0 is the initial porosity of the contact interface.

[0071] The above pressure loading refers to the state when the pressure generated by the sealing medium is loaded on the dynamic and static ring during the operation of the mechanical seal.

[0072] S4, determining the deformation state of the sealing interface according to the compression amount of the sealing interface.

[0073] The deformation state of the sealing interface includes elastic deformation, elastic-plastic deformation and plastic deformation, and the specific steps of determining the deformation state of the sealing interface according to the compression amount of the sealing interface are as follows:

[0074] S401, calculating the elastic deformation critical compression amount and the plastic deformation critical compression amount of the sealing interface, the elastic deformation critical compression amount is denoted as δ ec , and the plastic deformation critical compression amount is denoted as δ ec , which are calculated according to formula (4) :

[0075]

[0076] wherein E is the equivalent elastic modulus of the dynamic and static ring, σ y is the equivalent yield limit of the dynamic and static ring, E and σ y are calculated according to formula (41) :

[0077]

[0078] the plastic deformation critical compression amount is denoted as δpc It means that δ pc The calculation is performed using equation (5):

[0079]

[0080] Where e is the natural constant.

[0081] S402, δ and δ ec and δ pc When comparing, when δ≤δ ec Then, elastic deformation occurs at the sealing interface, when δ ec ≤δ≤δ pc Then, the sealing interface undergoes elastoplastic deformation, when δ pc If the value is less than or equal to δ, then plastic deformation occurs at the sealing interface.

[0082] S5. Based on the deformation state of the sealing interface, determine the first end face specific pressure under the non-permeability critical contact condition of the sealing interface.

[0083] The first end face specific pressure is p. cmin It means that p cmin The calculation is performed using equation (6):

[0084]

[0085] Where a is the contact area of ​​the micro-convexity, a ec a is the critical contact area for elastic deformation of the micro-convex body. pc Let a and a' be the critical contact areas for plastic deformation of the micro-convex body. ec With a pc Specifically, the calculation is performed using formula (61):

[0086]

[0087] S6. Determine the specific pressure of the second end face of the sealing interface based on the material parameters of the dynamic and static rings and the critical wear rate of the mechanical seal.

[0088] In this application, the sealing surfaces of both the rotating ring and the stationary ring are smooth. Because the hardness of the rotating ring is higher than that of the stationary ring, when the rotating ring and the stationary ring rotate relative to each other, the sealing surface of the stationary ring will wear first, resulting in wear. The ratio of this wear to time is the wear rate. The wear rate standard specified in the "Technical Conditions for Mechanical Seals" is 0.02mm / 100h. When the wear rate is less than 0.02mm / 100h, it indicates that the mechanical seal meets the wear standard. When the wear rate is greater than 0.02mm / 100h, it indicates that the mechanical seal does not meet the wear standard.

[0089] The critical wear rate of the mechanical seal is represented by γ, where γ = 0.02 mm / 100 h. The specific pressure of the second end face in step S6 is represented by p.cmax is calculated using equation (7):

[0090]

[0091] where v is the sliding velocity of the sealing surface, v is calculated using equation (71):

[0092]

[0093] S7, determining the design range of the mechanical seal surface pressure according to the size of the first end surface pressure and the second end surface pressure.

[0094] The following is a specific calculation of the mechanical seal surface pressure:

[0095] S1, obtaining the material parameters, surface topography parameters, structure parameters and working condition parameters of the mechanical seal moving and static rings, wherein the material parameters and surface topography parameters of the mechanical seal moving and static rings are shown in Table 1, and the structure parameters and working condition parameters of the mechanical seal moving and static rings are shown in Table 2.

[0096] Table 1 Material parameters and surface topography parameters of mechanical seal moving and static rings

[0097]

[0098]

[0099] Table 2 Structure parameters and working condition parameters of mechanical seal moving and static rings

[0100]

[0101] S2, determining the maximum height of the equivalent contact interface gap and the initial porosity of the moving and static rings according to the surface topography parameters of the moving and static rings.

[0102] The maximum height R y1 of the dynamic ring surface profile in Table 1 is 0.28, and the maximum height R y2 of the static ring surface profile is 2.13, which is substituted into equation (1)

[0103] h = 0.746 (R y1 + R y2 )(1)

[0104] The maximum height h of the fixed dynamic and static ring contact interface gap is 1.79786 μm;

[0105] The initial porosity φ0 is calculated using equation (2):

[0106]

[0107] where D is the equivalent fractal dimension of the moving and static rings, and aLm Let D be the base area of ​​the largest micro-protrusion at the contact interface, and l be the diameter of the contour base of the largest micro-protrusion at the contact interface. Lm And l can be calculated using equation (21):

[0108]

[0109] Where G is the equivalent scale coefficient of the dynamic and static rings, and G is calculated using equation (22):

[0110]

[0111] Substituting the dimensional coefficients G1 and G2 of the moving ring end face from Table 1 into Equation (22), we obtain the equivalent dimensional coefficients G of the moving and stationary rings; substituting the fractal dimensions D1 and D2 of the moving ring end face from Table 1 into Equation (21), we obtain the equivalent fractal dimensions D of the moving and stationary rings; substituting the equivalent fractal dimensions D of the moving and stationary rings, the equivalent dimensional coefficients G of the moving and stationary rings, and the maximum height h of the gap between the moving and stationary ring contact interfaces into Equation (21), we obtain the contour base diameter l of the largest micro-protrusion at the contact interface; substituting the contour base diameter l of the largest micro-protrusion at the contact interface into Equation (21), we obtain the base area a of the largest micro-protrusion at the contact interface. Lm .

[0112] Finally, the equivalent fractal dimension D of the moving and stationary rings and the base area a of the largest micro-protrusion at the contact interface are calculated. Lm Substituting the diameter l of the substrate of the largest micro-protrusion at the contact interface into equation (2), we obtain the initial porosity φ0 = 0.83.

[0113] S3. Determine the sealing interface compression amount based on the non-permeability critical contact conditions of the contact interface, the maximum height of the contact interface gap in step S2, and the initial porosity.

[0114] δ is calculated using equation (3):

[0115]

[0116] Substituting φ = 0.312, initial porosity φ0 = 0.83, and maximum height h = 1.798 μm of the gap between the moving and stationary rings into equation (3), we obtain the sealing interface compression δ = 1.354 × 10⁻⁶. -6 m.

[0117] S4. Determine the deformation state of the sealing interface based on the compression amount of the sealing interface, which includes the following steps:

[0118] S401. Calculate the critical compression amount for elastic deformation and the critical compression amount for plastic deformation at the sealing interface. The critical compression amount for elastic deformation is expressed as δ. ec It means that δ ecThe formula (4) is used for calculation:

[0119]

[0120] Wherein, E is the equivalent elastic modulus of the dynamic and static rings, σ y is the equivalent yield limit of the dynamic and static rings, E, σ y The formula (41) is used for calculation:

[0121]

[0122] The dynamic ring elastic modulus E1, the static ring elastic modulus E2, the dynamic ring Poisson's ratio υ1, the static ring Poisson's ratio υ2, the dynamic ring yield limit σ1, and the static ring yield limit σ2 in Table 1 are substituted into the formula (41) to obtain the equivalent elastic modulus E of the dynamic and static rings and the equivalent yield limit σ y of the dynamic and static rings. The equivalent fractal dimension D of the dynamic and static rings, the equivalent scale coefficient G of the dynamic and static rings, the profile base diameter l of the maximum microconvex body of the contact interface, the equivalent elastic modulus E of the dynamic and static rings, and the equivalent yield limit σ y of the dynamic and static rings are substituted into the formula (4) to obtain the elastic deformation critical compression amount δ ec = 7.243 × 10 -12 m.

[0123] The plastic deformation critical compression amount is represented by δ pc , and δ pc The formula (5) is used for calculation:

[0124]

[0125] The equivalent fractal dimension D of the dynamic and static rings, the equivalent scale coefficient G of the dynamic and static rings, the profile base diameter l of the maximum microconvex body of the contact interface, the equivalent elastic modulus E of the dynamic and static rings, and the equivalent yield limit σ y of the dynamic and static rings are substituted into the formula (4) to obtain the plastic deformation critical compression amount δ pc = 1.425 × 10 -6 m.

[0126] S402, δ is compared with δ ec and δ pc When δ≤δ ec , the sealing interface occurs elastic deformation, when δ ec ≤δ≤δ pc , the sealing interface occurs elastic-plastic deformation, and when δ pc ≤δ, the sealing interface occurs plastic deformation.

[0127] When δ = 1.354 × 10 -6 m, δ ec = 7.243 × 10 -12 m, δpc = 1.425 x 10 -6 m are compared, it is found that δ ec ≤ δ ≤ δ pc , which indicates that the sealing interface has undergone elastic-plastic deformation.

[0128] S5, according to the deformation state of the sealing interface, the first end face specific pressure p cmin of the sealing interface under the non-percolation critical contact condition is determined. cmin The formula (6) is used for calculation:

[0129]

[0130] Wherein a is the micro asperity contact area, a ec is the micro asperity elastic deformation critical contact area, a pc is the micro asperity plastic deformation critical contact area, a, a ec and a pc The formula (61) is used for calculation:

[0131]

[0132] The sealing interface compression δ, the equivalent size coefficient G of the dynamic and static ring, and the profile base diameter l of the maximum micro asperity of the contact interface are substituted into the formula (61) to obtain the micro asperity contact area a; the equivalent yield limit σ y of the dynamic and static ring, the equivalent elastic modulus E of the dynamic and static ring, the equivalent size coefficient G of the dynamic and static ring, the equivalent fractal dimension D of the dynamic and static ring, and the profile base diameter l of the maximum micro asperity of the contact interface are substituted into the formula (61) to obtain the micro asperity elastic deformation critical contact area a ec and the micro asperity plastic deformation critical contact area a pc .

[0133] The equivalent yield limit σ y of the dynamic and static ring, the equivalent elastic modulus E of the dynamic and static ring, the equivalent size coefficient G of the dynamic and static ring, the equivalent fractal dimension D of the dynamic and static ring, the profile base diameter l of the maximum micro asperity of the contact interface, the micro asperity contact area a, the micro asperity elastic deformation critical contact area a ec and the micro asperity plastic deformation critical contact area a pc are substituted into the formula (6) to obtain the first end face specific pressure p cmin = 1.771 MPa.

[0134] S6, according to the material parameters of the dynamic and static ring and the critical wear rate of the mechanical seal, the second end face specific pressure p cmax of the sealing interface is determined.

[0135] When the moving ring and the stationary ring rotate relatively, the sealing surface of the stationary ring is first abraded, and an abrasion amount is generated. The abrasion rate is the ratio of the abrasion amount to time. The abrasion rate of 0.02 mm / 100 h is a standard abrasion rate specified in the Technical Conditions for Mechanical Seals. When the abrasion rate is less than 0.02 mm / 100 h, the mechanical seal meets the abrasion standard. When the abrasion rate is greater than 0.02 mm / 100 h, the mechanical seal does not meet the abrasion standard. The critical abrasion rate is denoted by γ, and γ = 0.02 mm / 100 h. The second end face specific pressure p cmax The formula (7) is used for calculation.

[0136]

[0137] wherein v is the sliding speed of the sealing surface, and v is calculated by the formula (71):

[0138]

[0139] The inner diameter R i of the sealing surface, the outer diameter R o of the sealing surface, and the main shaft rotating speed n in Table 2 are substituted into the formula (71) to obtain the sliding speed v of the sealing surface. The sliding speed v of the sealing surface, the critical abrasion rate γ, the stationary ring abrasion coefficient k in Table 1, and the hardness H of the stationary ring are substituted into the formula (7) to obtain the second end face specific pressure p cmax = 5.682 MPa.

[0140] S7. According to the sizes of the first end face specific pressure and the second end face specific pressure, the design range of the mechanical seal end face specific pressure is determined.

[0141] In the embodiment, the first end face specific pressure p cmin = 1.771 MPa, the second end face specific pressure p cmax = 5.682 MPa, and the control range of the end face specific pressure is 1.771-5.682 MPa. The mechanical seal can realize zero leakage, and the abrasion rate of the sealing surface can meet the requirements.

Claims

1. A method of designing a mechanical seal face pressure ratio, characterized by, The method comprises the following steps: S1, obtaining material parameters, end face topography parameters, structure parameters and working condition parameters of the dynamic and static rings of the mechanical seal; S2, determining the maximum height of the contact interface gap and the initial porosity of the dynamic and static rings according to the end face topography parameters of the dynamic and static rings; S3, determining the compression amount of the sealing interface according to the non-percolation critical contact condition of the contact interface and the maximum height of the contact interface gap and the initial porosity in step S2; S4, determining the deformation state of the sealing interface according to the compression amount of the sealing interface; S5, determining the first end face specific pressure under the non-percolation critical contact condition of the sealing interface according to the deformation state of the sealing interface; The first end face specific pressure is p cmin It means that p cmin The calculation is performed using equation (6): （6） where a is the micro asperity contact area, a ec is the micro asperity elastic deformation critical contact area, a pc is the micro asperity plastic deformation critical contact area, E is the equivalent elastic modulus of the dynamic and static rings, G is the equivalent scale coefficient of the dynamic and static rings, D is the equivalent fractal dimension of the dynamic and static rings, l is the profile base diameter of the largest micro asperity of the contact interface, δ is the compression of the sealing interface, δ ec is the elastic deformation critical compression, δ pc is the plastic deformation critical compression, σ2 is the yield limit of the static ring, σ y is the equivalent yield limit of the dynamic and static rings; S6, determining the second end face specific pressure of the sealing interface according to the material parameters of the dynamic and static rings and the critical wear rate of the mechanical seal; The critical wear rate of the mechanical seal is represented by γ, γ = 0.02 mm / 100 h, and the second end face specific pressure is represented by p cmax , p cmax is calculated by formula (7): (7) Wherein, H is the hardness of the static ring, k is the wear coefficient of the static ring, and v is the sliding speed of the sealing surface; S7, determining the design range of the end face specific pressure of the mechanical seal according to the size of the first end face specific pressure and the second end face specific pressure.

2. The design calculation method of claim 1, wherein, The material parameters of the dynamic and static rings include the dynamic ring elastic modulus E1, the static ring elastic modulus E2, the dynamic ring material Poisson's ratio υ1, the static ring material Poisson's ratio υ2, the static ring wear coefficient k, the static ring hardness H, the dynamic ring yield limit σ1 and the static ring yield limit σ2; The end surface topography parameters of the dynamic and static rings include dynamic ring fractal dimension D1, static ring fractal dimension D2, dynamic ring scale coefficient G1, static ring scale coefficient G2, and maximum height R of the dynamic ring surface profile y1 The maximum height R of the static ring surface profile y2 ; The structural parameters of the dynamic and static rings include the outer radius R of the sealing surface o and the inner radius R i ; The working condition parameters of the dynamic and static rings include the main shaft rotating speed n.

3. The method of design calculation according to claim 1, characterized in that, In step S2, the maximum height of the contact interface gap is represented by h, and h is calculated by formula (1): (1) The initial porosity of the contact interface is represented by Φ0, and Φ0 is calculated by formula (2): (2) where a Lm is the base area of the largest asperity of the contact interface, a is the asperity contact area, R y1 is the maximum height of the surface profile of the moving ring, R y2 is the maximum height of the surface profile of the stationary ring.

4. The method of design calculation according to claim 1, characterized in that, In step S3, the non-percolation critical contact condition of the contact interface refers to that after pressure loading, the porosity of the contact interface of the dynamic and static rings reaches the critical porosity, the critical porosity is represented by Φ, and Φ=0.312; the compression amount of the sealing interface is represented by δ, and δ is calculated by formula (3): (3) Wherein, Φ0 is the initial porosity of the contact interface, and h is the maximum height of the contact interface gap.

5. The method of design calculation according to claim 1, characterized in that, In step S4, the deformation state of the sealing interface is divided into elastic deformation, elastic-plastic deformation and plastic deformation, and the specific steps of determining the deformation state of the sealing interface according to the compression amount of the sealing interface are as follows: S401、Calculate the elastic deformation critical compression amount and the plastic deformation critical compression amount of the sealing interface, the elastic deformation critical compression amount adopts δ ec , and the plastic deformation critical compression amount adopts δ ec The calculation is performed by using formula (4): (4) The plastic deformation critical compression amount is expressed by δ pc The plastic deformation critical compression amount is expressed by δ pc The plastic deformation critical compression amount is calculated by the following equation (5). (5) Wherein, e is a natural constant; S402, compare δ with δ ec and δ pc When δ≤δ ec , the sealing interface is elastically deformed, when δ ec ≤δ≤δ pc , the sealing interface is elastically-plastically deformed, and when δ pc ≤δ, the sealing interface is plastically deformed.

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