Calculation method of water film pressure distribution in bearings considering journal inertia force under dynamic load

Abstract

The invention belongs to the field of water-lubricated bearing pressure calculation, and in particular relates to a method for calculating water film pressure distribution of a water-lubricated bearing under the condition of a journal inertia force under a dynamic load. The method comprises the following steps: on the basis of a two-dimensional Reynolds equation, a water film thickness equation is substituted into the equation for derivation and dimensionless transformation; a water film is divided into a plurality of grids by using a finite element method; pressure values ​​at each node on the grid are used to form each order difference quotient to approximately replace the derivative in the Reynolds equation; the Reynolds equation is solved by an iterative method; and the pressure value of each internal node is obtained after a convergence condition is met; the method can analyze the load and pressure distribution of a water-lubricated bearing considering the journal inertia force; the water film pressure distribution at different time steps can be obtained and the pressure extreme values ​​at different time steps can be diagnosed; only the bearing parameters, the number of axial and circumferential divisions of the water film and the rotation speed need to be input; the calculation time is short and the calculation accuracy is high.

Description

Technical Field

[0001] The invention belongs to the field of water-lubricated bearing pressure calculation, and in particular relates to a method for calculating water film pressure distribution of a water-lubricated bearing under dynamic load and considering the inertial force of a journal. Background Art

[0002] Radial sliding bearings are widely used in industry. They have the advantages of strong load-bearing capacity, stable operation, good vibration resistance and long life, and are widely used in various fields. Traditional sliding bearings are often made of materials such as babbitt alloys and copper-aluminum alloy metal anti-friction, and most of them use oil as a lubricant. When ships lubricated with oil are used in rivers and lakes, their lubricating oil is easy to leak and pollute water resources. Because water-lubricated bearings have the characteristics of resource conservation and environmental friendliness, they can be used in many important equipment, such as ship propulsion systems, turbines, etc.

[0003] When the bearing is working, a water film with a dynamic pressure effect is formed in the bearing gap, which in turn generates water film pressure to support the shaft, avoiding direct contact between the inner surface of the bearing and the journal, reducing bearing wear, and extending the service life of the bearing. However, when water is used as a lubricating medium, the viscosity is much lower than that of lubricating oil, resulting in a weaker bearing capacity. The water film pressure distribution determines the bearing's load capacity, service life, and lubrication performance. Therefore, calculating the water film pressure distribution and pressure extremes of water-lubricated bearings is of great significance for analyzing the water-lubricated bearing's load capacity.

[0004] In previous studies, the influence of external forces on the water film pressure distribution was rarely considered. In fact, under the action of external forces, the journal itself also has a certain acceleration. When the external force changes with time, the direction and magnitude of the journal velocity change. In this case, the influence of the journal inertia force must be considered. Compared with oil-lubricated bearings, water-lubricated bearings are more difficult to converge in time domain simulation, especially when considering inertia forces. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a method for calculating the water film pressure distribution of a water-lubricated bearing under dynamic load considering the journal inertia force, so as to obtain the pressure distribution and pressure extremes of the bearing water film.

[0006] The present invention provides a method for calculating the water film pressure distribution of a water-lubricated bearing under dynamic load considering the inertial force of the journal, and the pressure distribution at each point of the bearing is obtained by solving the Reynolds equation by using a numerical method to discretize the water film using a finite difference method, including the following steps:

[0007] Step 1: Based on the fluid lubrication theory, the two-dimensional Reynolds equation for incompressible water lubrication motion in the bearing under dynamic load is established as follows:

[0008]

[0009] Among them, s is the circumferential displacement of the bearing, and z is the axial displacement of the bearing;

[0010] p is the water film pressure, h is the water film thickness;

[0011] η0 is the dynamic viscosity.

[0012] Step 2: Substitute the water film thickness equation into the two-dimensional Reynolds equation for derivation and dimensionlessness to establish the water film bearing capacity W in the horizontal direction. x and the vertical water film bearing capacity W y Systems of equations;

[0013] Step 3: Use the finite difference method to discretize the water film, establish the difference format of the Reynolds equation, obtain the pressure of each node, and iteratively correct the pressure of each node to obtain a pressure value that satisfies the iteration error;

[0014] Step 4: Based on the force balance equation considering the journal inertia force and the water film bearing capacity formula described in step 2, a force balance equation is established, and the eccentricity ε and the offset angle φ are derived with respect to time and brought into the force balance equation to obtain a differential format of the force balance equation;

[0015] Step 5: Change the eccentricity change rate of the current time step Deflection angle change rate Substitute the difference format of the force balance equation obtained in step 4 to obtain the eccentricity change rate and the angular change rate of the next time step, as well as W of the current time step. x and W y ;

[0016] Step 6: W x and W y Perform force synthesis to obtain the distribution of water film pressure p at the current time step.

[0017] This technical solution uses the finite difference method to discretize the water film to solve the Reynolds equation, and analyzes the load and pressure distribution of the water-lubricated bearing taking into account the journal inertia force; it can obtain the water film pressure distribution at different time steps and diagnose the pressure extremes at different time steps. This method is easy to implement, has high calculation accuracy, high efficiency and high operability.

[0018] In some of the embodiments, the two-dimensional Reynolds equation described in step S1 ignores the effect of body force, assumes that the fluid has no sliding on the interface, ignores the change of pressure along the thickness direction of the water film, and ignores the influence of the curvature of the water film.

[0019] In some embodiments, the water film thickness equation is h=c+ecosθ, where c is the absolute clearance, c=Rr, R is the bearing radius, r is the shaft neck radius, e is the eccentricity, which is the distance between the bearing center and the shaft neck center; θ is the circumferential angular displacement starting from the direction of maximum water film thickness.

[0020] In some embodiments, in step 2, the water film thickness equation h=c+ecosθ is substituted into the two-dimensional Reynolds equation to obtain

[0021]

[0022] Taking partial derivatives of both ends of the water film thickness equation h=c+ecosθ with respect to θ, we get

[0023]

[0024] Substituting it into formula (2) we get:

[0025]

[0026] Where ω is the angular velocity of the bearing, is the rate of change of the deflection angle, is the rate of change of eccentricity, η0 is the dynamic viscosity;

[0027] Formula 3 is non-dimensionalized, and the dimensionless factor is:

[0028]

[0029] In some embodiments, the water film pressure p is formed by the superposition of the water film pressure p1 of the dynamic pressure effect generated by the rotation angular velocity and the water film pressure p2 of the squeezing effect generated by the squeezing velocity, that is:

[0030] p=p1+q·p2(5)

[0031] Substituting p1 and p2 into formula (3), we get:

[0032]

[0033] Substituting the dimensionless factor (4) into formula (6), we obtain:

[0034]

[0035] make but:

[0036] but:

[0037]

[0038] Thus, the horizontal water film bearing capacity W is obtained x The vertical water film bearing capacity W y System of equations:

[0039]

[0040] In some of the embodiments, in step 3, the finite difference method is to divide the water film of the bearing into a grid; use the pressure value at each node to form each order difference quotient to approximately replace the derivative in the Reynolds equation, number the grid nodes according to the number of columns and rows, axially with i, circumferentially with j, and the first-order derivative at the node (i, j) can be approximately expressed by the difference quotient of its adjacent nodes:

[0041]

[0042] The difference form of the Reynolds equation is

[0043]

[0044]

[0045] make:

[0046]

[0047]

[0048]

[0049]

[0050] E i,j =A i,j +B i,j +C i,j +D i,j ;

[0051]

[0052] F 2,i,j =Δφ 2 *cosφ;

[0053] In some embodiments, in step 3, it is determined whether the result of each iteration has reached sufficient accuracy to determine whether the iteration process can be terminated, usually based on the following relative convergence criteria:

[0054]

[0055] The allowable relative error value δ is taken as 10 -3 .

[0056] In some embodiments, when the journal inertia force is not considered, the force balance equations in the horizontal direction x and the vertical direction y are as follows:

[0057]

[0058] Among them, G x is the external load in the x direction, G y is the external load in the y direction;

[0059] make Substituting into formula (9),

[0060]

[0061] Substituting formula (11) into formula (10), the force balance equation is simplified to:

[0062]

[0063] In step (4), when the journal inertia force is considered, ζ is the direction of the line connecting the maximum thickness of the water film and the axis, and η is the tangential direction of the maximum thickness of the water film. The force balance equation is:

[0064]

[0065] Where M is the bearing mass, W is the water film bearing capacity, is the centripetal force caused by the journal inertia force;

[0066] According to the force conversion relationship, the forces in the ζ and η directions are converted to the x and y directions, and the force balance equation considering the journal inertia force is:

[0067]

[0068] The relationship between eccentricity ε, deviation angle φ and acceleration is:

[0069]

[0070] Substituting the relationship (15) between the eccentricity ε, the offset angle φ and the acceleration into the formula (14) for simplification, the simplified force balance equation considering the journal inertia force is obtained:

[0071]

[0072] Backward difference is used to solve and The difference format is as follows:

[0073]

[0074] Substituting the difference format of the above formula into the formula (16) and simplifying it, the final difference form of the force balance equation considering the journal inertia force is obtained:

[0075]

[0076] Based on the above technical scheme, the present invention uses the finite difference method to discretize the water film to solve the Reynolds equation, and analyzes the load and pressure distribution of the water-lubricated bearing taking into account the journal inertia force; the water film pressure distribution at different time steps can be obtained and the pressure extremes at different time steps can be diagnosed. This method is easy to implement, has high calculation accuracy, high efficiency and high operability, and is of great significance for analyzing the load-bearing capacity of water-lubricated bearings. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0078] Figure 1 A schematic diagram of the structure of a bearing and a coordinate system in an embodiment of the present invention;

[0079] Figure 2 This is a diagram showing the development of a water film in an embodiment of the present invention;

[0080] Figure 3 Schematic diagram of water film pressure distribution at time step t=0.00625s in an embodiment of the present invention;

[0081] Figure 4 Schematic diagram of water film thickness distribution at time step t=0.00625s in an embodiment of the present invention;

[0082] Figure 5 Schematic diagram of water film pressure distribution at time step t=0.00688s in an embodiment of the present invention;

[0083] Figure 6 Schematic diagram of water film thickness distribution at time step t = 0.00688s in an embodiment of the present invention

[0084] Figure 7 Schematic diagram of water film pressure distribution at time step t=0.00750s in an embodiment of the present invention;

[0085] Figure 8 Schematic diagram of water film thickness distribution at time step t=0.00750s in an embodiment of the present invention;

[0086] Fig. 9 Schematic diagram of water film pressure distribution at time step t=0.0812s in an embodiment of the present invention;

[0087] Fig.10 Schematic diagram of water film thickness distribution at time step t=0.0812s in an embodiment of the present invention. DETAILED DESCRIPTION

[0088] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0089] Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. In addition, it can also be understood that although the efforts made in this development process may be complicated and lengthy, for ordinary technicians in this field related to the content disclosed in this application, some changes in design, manufacturing or production based on the technical content disclosed in this application are just conventional technical means, and should not be understood as insufficient content disclosed in this application.

[0090] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those of ordinary skill in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0091] According to the theory of fluid dynamic lubrication, the parameters that affect the water film pressure distribution of the sliding bearing mainly include the bearing width-to-diameter ratio, relative clearance, radial load, viscosity of the lubricating oil, and spindle speed. The calculation of the performance of the hydrodynamic sliding bearing and the water film pressure distribution requires solving the two-dimensional Reynolds equation. The Reynolds equation is actually a second-order elliptic partial differential equation obtained by simplifying the NS equation based on certain assumptions.

[0092] Figure 1 The figure shows the bearing diagram and the coordinate system used, where ξo'η is the rotating coordinate system, O' is the center of the journal, ξ is the direction of the line connecting the water film at the maximum thickness and the axis, and η is the tangential direction between the water film at the maximum thickness and the axis; xOy is the fixed coordinate system, O is the bearing center, x is the horizontal direction, and y is the vertical direction.

[0093] The method for calculating the water film pressure distribution of a water-lubricated bearing under dynamic load considering the inertial force of the journal is a method for obtaining the pressure distribution at each point of the bearing by solving the Reynolds equation by using a numerical method and a finite difference method to discretize the water film, and includes the following steps:

[0094] Step 1: Based on the fluid lubrication theory, the two-dimensional Reynolds equation for incompressible water lubrication motion in the bearing under dynamic load is established as follows:

[0095]

[0096] Among them, s is the circumferential displacement of the bearing, and z is the axial displacement of the bearing;

[0097] p is the water film pressure, h is the water film thickness;

[0098] η0 is the dynamic viscosity;

[0099] U is the bearing speed, and U=ωR.

[0100] Step 2: Substitute the water film thickness equation into the two-dimensional Reynolds equation for derivation and dimensionlessness to establish the water film bearing capacity W in the horizontal direction. x and the vertical water film bearing capacity W y Systems of equations;

[0101] Step 3: Use the finite difference method to discretize the water film, establish the difference format of the Reynolds equation, obtain the pressure of each node, and iteratively correct the pressure of each node to obtain a pressure value that satisfies the iteration error;

[0102] Step 4: Based on the force balance equation considering the journal inertia force and the water film bearing capacity formula described in step 2, a force balance equation is established, and the eccentricity ε and the offset angle φ are derived with respect to time and brought into the force balance equation to obtain a differential format of the force balance equation;

[0103] Step 5: Change the eccentricity change rate of the current time step Deflection angle change rate Substitute the difference format of the force balance equation obtained in step 4 to obtain the eccentricity change rate and the angular change rate of the next time step, as well as W of the current time step. x and W y ;

[0104] Step 6: W x and W y Perform force synthesis to obtain the distribution of water film pressure p at the current time step.

[0105] The finite difference method is used to discretize the water film to solve the Reynolds equation, and the load and pressure distribution of the water-lubricated bearing taking into account the journal inertia force is analyzed; the water film pressure distribution at different time steps can be obtained and the pressure extremes at different time steps can be diagnosed. This method is easy to implement, has high calculation accuracy, high efficiency and high operability.

[0106] The two-dimensional Reynolds equation described in step S1 ignores volume forces, such as gravity, magnetism, etc.; assumes that the fluid does not slide on the interface, that is, the velocity of the fluid attached to the surface is the same as the surface velocity; does not consider the change in pressure along the thickness of the water film; and the radius of curvature of the bearing surface is large compared to the film thickness, so the influence of the curvature of the water film is ignored.

[0107] The water film thickness equation is h=c+ecosθ, where c is the absolute clearance, c=Rr, R is the bearing radius, r is the journal radius, e is the eccentricity, which is the distance between the bearing center and the journal center; θ is the circumferential angular displacement starting from the direction of maximum water film thickness.

[0108] Substituting the water film thickness equation h=c+ecosθ into the two-dimensional Reynolds equation, we can obtain

[0109]

[0110] Taking partial derivatives of both ends of the water film thickness equation h=c+ecosθ with respect to θ, we get

[0111]

[0112] Substituting it into formula (2) we get:

[0113]

[0114] Where ω is the angular velocity of the bearing, is the rate of change of the deflection angle, is the rate of change of eccentricity, η0 is the dynamic viscosity;

[0115] Formula 3 is non-dimensionalized, and the dimensionless factor is:

[0116]

[0117] The water film pressure p1 and the squeezing effect water film pressure p2 generated by the squeezing speed are superimposed, that is:

[0118] p=p1+q·p2 (5)

[0119] Substituting p1 and p2 into formula (3), we get:

[0120]

[0121] Substituting the dimensionless factor (4) into formula (6), we obtain:

[0122]

[0123] make but:

[0124] but:

[0125]

[0126] Thus, the horizontal water film bearing capacity W is obtained x The vertical water film bearing capacity W y System of equations:

[0127]

[0128] In step 3, the finite difference method is to divide the water film of the bearing into grids; Figure 2 As shown in the figure, the pressure values ​​at each node are used to form the difference quotients of each order to approximately replace the derivatives in the Reynolds equation. The grid nodes are numbered according to the number of columns and rows, with i in the axial direction and j in the circumferential direction. The first-order derivative at the node (i, j) can be approximately expressed by the difference quotient of its adjacent nodes:

[0129]

[0130] The difference form of the Reynolds equation is

[0131]

[0132]

[0133] make:

[0134]

[0135]

[0136]

[0137]

[0138] E i,j =A i,j +B i,j +C i,j +D i,j ;

[0139]

[0140] F 2,i,j=Δφ 2 *cosφ;

[0141] In step 3, the super-relaxation iteration method is used to calculate the pressure value of the middle node using the pressure values ​​of the four nodes around the node, and the node pressure is corrected to determine whether the result of each iteration has reached sufficient accuracy to decide whether the iteration process can be terminated, usually based on the following relative convergence criteria:

[0142]

[0143] The allowable relative error value δ is taken as 10 -3 .

[0144] When the journal inertia force is not considered, the force balance equations in the horizontal direction x and the vertical direction y are as follows:

[0145]

[0146] Among them, G x is the external load in the x direction, G y is the external load in the y direction;

[0147] make Substituting into formula (9),

[0148]

[0149] Substituting formula (11) into formula (10), the force balance equation is simplified to:

[0150]

[0151] In step (4), when the journal inertia force is considered, the force balance equation is:

[0152]

[0153] Among them, ζ is the direction of the line connecting the maximum thickness of the water film and the axis, η is the tangential direction of the maximum thickness of the water film, M is the bearing mass, W is the water film bearing capacity, is the centripetal force caused by the journal inertia force;

[0154] According to the force conversion relationship, the forces in the ζ and η directions are converted to the x and y directions, and the force balance equation considering the journal inertia force is:

[0155]

[0156] The relationship between eccentricity ε, deviation angle φ and acceleration is:

[0157]

[0158] Substituting the relationship (15) between the eccentricity ε, the offset angle φ and the acceleration into the formula (14) for simplification, the simplified force balance equation considering the journal inertia force is obtained:

[0159]

[0160] Backward difference is used to solve and The difference format is as follows:

[0161]

[0162] Substituting the difference format of the above formula into the formula (16) and simplifying it, the final difference form of the force balance equation considering the journal inertia force is obtained:

[0163]

[0164] like Figure 2 As shown, the water film is spread out along the axial direction, and 41 nodes are divided along the axial direction, that is, n = 40, and 61 nodes are divided circumferentially, that is, m = 60. The water film thickness h at each node is obtained i,j , substitute A i,j , B i,j , C i,j , D i,j , E i,j 、F 1i,j 、F 2i,j In the difference format, we get and When calculating the water film pressure, iterate from the starting point to the end point. Assuming that the initial pressure of each point is zero, in the process of calculating the pressure of each point, if the pressure calculation value of a point is negative, it is determined that the water film at this point is broken, the pressure value is zero, and the pressure value of the next point is calculated. The boundary condition adopts the Reynolds boundary condition, that is, This boundary condition is close to the actual situation. In the iterative process, the super-relaxation iteration method is used to calculate the pressure value of the middle node using the pressure values ​​of the four nodes around the node, and the node pressure is corrected until it reaches the iterative error range to obtain the water film pressure distribution of each node.

[0165] In this embodiment, the bearing diameter D is set to 70.0895 mm, the journal diameter d is set to 70.005 mm, the rotation speed is 2 m / s, the initial eccentricity ε is set to 0.1, and the water density ρ is set to 1000 kg / m 3 , viscosity η=1.103*10 -3 Pa·s, external load in x direction G x =1.0E4cos(800πt), external load in y direction G y =1.0E4sin(800πt), obtained through the above calculation Figure 3-Figure 5 result.

[0166] Based on the above technical solution, the present invention uses the finite difference method to discretize the water film to solve the Reynolds equation, analyzes and considers the inertial force of the journal, including the centripetal acceleration and the translational acceleration, derives the motion equation of the journal, solves the water film under the action of the accelerated journal by the finite difference method, and obtains the load and pressure distribution of the water-lubricated bearing of the water film pressure distribution; it can obtain the water film pressure distribution at different time steps and diagnose the pressure extremes at different time steps. This method is easy to implement, has high calculation accuracy, high efficiency and high operability, and is of great significance for analyzing the load capacity of water-lubricated bearings. .

[0167] Finally, it should be noted that: the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0168] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, a person skilled in the art should understand that the specific implementation mode of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A method for calculating the water film pressure distribution of a bearing considering the journal inertia force under dynamic load, characterized in that: The steps include: Step 1: Based on the fluid lubrication theory, the two-dimensional Reynolds equation for incompressible water lubrication motion in the bearing under dynamic load is established as follows: Among them, s is the circumferential displacement of the bearing, and z is the axial displacement of the bearing; p is the water film pressure, h is the water film thickness; η0 is the dynamic viscosity; U is the bearing speed, and U = ωR; Step 2: Substitute the water film thickness equation into the two-dimensional Reynolds equation for derivation and dimensionlessness to establish the water film bearing capacity W in the horizontal direction. x and the vertical water film bearing capacity W y Systems of equations; Step 3: Use the finite difference method to discretize the water film, establish the difference format of the Reynolds equation, obtain the pressure of each node, and iteratively correct the pressure of each node to obtain a pressure value that satisfies the iteration error; Step 4: Based on the force balance equation considering the journal inertia force and the water film bearing capacity formula described in step 2, a force balance equation is established, and the eccentricity ε and the offset angle φ are derived with respect to time and brought into the force balance equation to obtain a differential format of the force balance equation; Step 5: Change the eccentricity change rate of the current time step Deflection angle change rate Substitute the difference format of the force balance equation obtained in step 4 to obtain the eccentricity change rate and the angular change rate of the next time step, as well as W of the current time step. x and W y ; Step 6: W x and W y Perform force synthesis to obtain the distribution of water film pressure p at the current time step.

2. The method for calculating the water film pressure distribution of a bearing considering the journal inertia force under dynamic load according to claim 1 is characterized in that: The two-dimensional Reynolds equation described in step S1 ignores the effect of body force, assumes that the fluid has no sliding on the interface, ignores the change of pressure along the thickness direction of the water film, and ignores the influence of the curvature of the water film.

3. The method for calculating the water film pressure distribution of a bearing considering the journal inertia force under dynamic load according to claim 2 is characterized in that: The water film thickness equation is h=c+ecosθ, Among them, c is the absolute clearance, c=Rr, R is the bearing radius, r is the journal radius, e is the eccentricity, which is the distance between the bearing center and the journal center; θ is the circumferential angular displacement starting from the direction of maximum water film thickness.

4. The method for calculating the water film pressure distribution of a bearing considering the journal inertia force under dynamic load according to claim 3 is characterized in that: In step 2, the water film thickness equation h=c+ecosθ is substituted into the two-dimensional Reynolds equation to obtain Taking partial derivatives of both ends of the water film thickness equation h=c+ecosθ with respect to θ, we get Substituting it into formula (2) we get: Where ω is the angular velocity of the bearing, is the rate of change of the deflection angle, is the rate of change of eccentricity, η0 is the dynamic viscosity; Formula 3 is non-dimensionalized, and the dimensionless factor is: 。 5. The method for calculating the water film pressure distribution of a bearing considering the journal inertia force under dynamic load according to claim 4 is characterized in that: The water film pressure p is formed by the superposition of the water film pressure p1 of the dynamic pressure effect generated by the rotation angular velocity and the water film pressure p2 of the squeezing effect generated by the squeezing velocity, that is: p=p1+q·p2(5) Substituting p1 and p2 into formula (3), we get: Substituting the dimensionless factor (4) into formula (6), we obtain: make but: but: Thus, the horizontal water film bearing capacity W is obtained x The vertical water film bearing capacity W y System of equations: 。 6. The method for calculating the water film pressure distribution of a bearing considering the journal inertia force under dynamic load according to claim 1 is characterized in that: In step 3, the finite difference method is to divide the water film of the bearing into grids; use the pressure value at each node to form each order difference quotient to approximately replace the derivative in the Reynolds equation, and number the grid nodes according to the number of columns and rows, with i in the axial direction and j in the circumferential direction. The sum of the first-order derivatives at the node (i, j) can be approximately expressed by the difference quotient of its adjacent nodes: The difference form of the Reynolds equation is make:

7. The method for calculating the water film pressure distribution of a bearing considering the journal inertia force under dynamic load according to claim 6 is characterized in that: In step 3, it is determined whether the result of each iteration has reached sufficient accuracy to decide whether the iteration process can be terminated, usually based on the following relative convergence criteria: The allowable relative error value δ is taken as 10 -3 .

8. The method for calculating the water film pressure distribution of a bearing considering the journal inertia force under dynamic load according to claim 1 is characterized in that: When the journal inertia force is not considered, the force balance equations in the horizontal direction x and the vertical direction y are as follows: Among them, G x is the external load in the x direction, G y is the external load in the y direction; make Substituting into formula (9), Substituting formula (11) into formula (10), the force balance equation is simplified to: In step (4), when the journal inertia force is considered, ζ is the direction of the line connecting the maximum thickness of the water film and the axis, and η is the tangential direction of the maximum thickness of the water film. The force balance equation is: Where M is the bearing mass, W is the water film bearing capacity, is the centripetal force caused by the journal inertia force; According to the force conversion relationship, the forces in the ζ and η directions are converted to the x and y directions, and the force balance equation considering the journal inertia force is: The relationship between eccentricity ε, deviation angle φ and acceleration is: Substituting the relationship (15) between the eccentricity ε, the offset angle φ and the acceleration into the formula (14) for simplification, the simplified force balance equation considering the journal inertia force is obtained: Backward difference is used to solve The difference format is as follows: Substituting the difference format of the above formula into the formula (16) and simplifying it, the final difference form of the force balance equation considering the journal inertia force is obtained: 。

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