Design method and system for a variable-section ultra-high-pressure plunger structure

Abstract

The present invention discloses a design method and system for a variable-section ultra-high-pressure plunger structure. First, the load and boundary conditions on the plunger are set. Then, by constructing the shape function of the variable-section plunger, the inner cavity structure of the variable-section plunger is determined. Secondly, based on finite element simulation calculations, the deformation distribution of the current plunger surface is obtained. Finally, the gradient descent method is used to iteratively optimize the parameters of the plunger inner cavity shape function until the termination condition is met, thereby obtaining the optimal variable-section ultra-high-pressure plunger structure. The variable-section ultra-high-pressure plunger structure and its design method proposed by the present invention, by changing the plunger inner cavity cross-sectional structure, match the plunger internal and external pressure difference with the cross-sectional stiffness, thereby significantly reducing the plunger surface deformation, taking into account both anti-deformation performance and lightweight requirements, and are easy to process, with prospects for large-scale engineering applications.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydraulic pumps, and in particular relates to a design method and system for a variable-cross-section ultra-high-pressure plunger structure. Background Art

[0002] Axial piston pumps are widely used in aerospace, engineering machinery, and other fields due to their high operating pressure, high power density, and compact structure. As hydraulic systems continue to increase their power density requirements, piston pumps are increasingly moving towards higher pressure and lighter weight. Increasing pressure levels helps reduce the size and weight of equipment. Studies have shown that increasing the pressure level from 21MPa to 56MPa can reduce the weight of the hydraulic system by 30% and the volume by 40%. However, existing commercial piston pumps generally have pressure levels of 21MPa to 35MPa, making it difficult to meet the application requirements of ultra-high pressure conditions of 56MPa and higher.

[0003] Excessive component deformation is a key technical bottleneck restricting the application of plunger pumps under ultra-high-pressure conditions. During operation, a micron-level lubrication clearance must be maintained between the plunger and the cylinder bore to ensure both sealing and load-bearing performance under high-pressure conditions. However, the uneven pressure differential generated by ultra-high-pressure oil on the inner and outer surfaces of the plunger can lead to significant irregular deformation. This not only easily results in poor sealing of the mating surfaces and exacerbated leakage, but also leads to excessive localized contact pressure, causing the plunger assembly to become stuck and wear, directly impacting performance and service life.

[0004] Traditional plungers generally utilize a cylindrical inner cavity with a uniform cross-section. While simply increasing the wall thickness can reduce local deformation, it inevitably leads to increased weight. This not only directly affects the power density of the plunger pump, but also, when the plunger rotates at high speeds, the inertial force exacerbates the overturning moment, further deteriorating the load-bearing and lubrication conditions of other friction pairs. Therefore, a plunger structural design method that can balance the requirements of high pressure and lightweight is urgently needed. Summary of the Invention

[0005] The purpose of the present invention is to address the deficiencies of the existing technology and provide a design method and system for an ultra-high-pressure plunger structure with a variable cross-section, which significantly reduces the deformation of the plunger surface while ensuring the lightweight requirements of the plunger, thereby promoting the high-pressure development of the plunger pump.

[0006] The present invention aims to provide a design method for an ultra-high pressure plunger structure with a variable cross-section, which matches the pressure difference between the inside and outside of the plunger with the cross-section stiffness by changing the cross-section design of the plunger cavity, thereby reducing the deformation of the plunger surface under ultra-high pressure conditions. The method comprises the following steps: (1) setting the load and boundary conditions on the plunger;

[0007] (2) Construct a plunger with a variable inner cavity cross-section and design a variable inner cavity cross-section shape of the plunger so that the pressure difference between the inside and outside of the plunger matches the cross-section stiffness; define the change of the plunger inner wall radius along the axial direction as the shape function S(a1, a2, ... a i ), determine the inner cavity structure of the variable cross-section plunger;

[0008] (3) Based on the boundary conditions and the plunger geometry, the deformation distribution D (a1, a2, ... a i );

[0009] (4) Based on the gradient descent method, iteratively optimize the parameter a of the plunger cavity shape function i ;

[0010] (5) Determine whether the termination condition is met. If not, repeat steps (2) to (4) until the termination condition is met, that is, the optimal variable-section ultra-high-pressure plunger structure is obtained.

[0011] Furthermore, in step (1), the loads on the inner and outer walls of the plunger are determined based on the axial displacement of the plunger surface, the axial length of the plunger, the high pressure load of the plunger pump, and the low pressure of the housing of the plunger pump.

[0012] Furthermore, in step (2), the variable cross-section inner cavity structure includes a conical inner cavity, an arc-shaped inner cavity and a stepped inner cavity, and their corresponding shape functions are:

[0013]

[0014]

[0015]

[0016] Where a i is the control parameter of the shape function; specifically, a t1 , a t2 is the control parameter of the cone inner cavity shape function, a c1 , a c2 is the control parameter of the arc-shaped inner cavity shape function, a s1 , a s2 … a sk is the control parameter of the step cavity shape function, k is the number of steps set, and the geometric structure of the plunger cavity can be flexibly changed by adjusting the parameters.

[0017] Furthermore, in step (4), the gradient descent optimization algorithm first calculates the partial derivative of the objective function with respect to each parameter to obtain the gradient vector, and then updates the shape parameters along the gradient descent direction;

[0018] Furthermore, the shape parameter ai The search domain is constrained by the lightweight requirement of the plunger, and the search range of the parameter space should satisfy:

[0019]

[0020] Where ρ is the material density and m is the plunger design mass. N (a i ) is the upper boundary of the shape function, i.e. the outer cylindrical surface of the plunger; S S (a i ) is the lower boundary of the shape function, i.e., the variable cross-section profile; S E (a i ) is the left boundary of the shape function, i.e. the plunger end face; S W (a i ) is the right boundary of the shape function, that is, the end face of the plunger close to the ball head.

[0021] Furthermore, in step (5), the termination condition is whether the degree of change of the surface deformation range of the current step relative to the surface deformation range of the previous step meets the requirements.

[0022] On the other hand, the present invention provides a design system for implementing a design method for an ultra-high pressure plunger structure with a variable cross-section, the system comprising:

[0023] The plunger cross-section design module is used to construct a variable inner cavity cross-section plunger and design a variable inner cavity cross-section shape of the plunger to match the pressure difference between the inside and outside of the plunger with the cross-section stiffness; the change in the radius of the plunger inner wall along the axial direction is defined as the shape function S(a1, a2, ... a i ), determine the inner cavity structure of the variable cross-section plunger;

[0024] The simulation calculation module is used to obtain the deformation distribution D (a1, a2, ... a) of the current plunger surface through finite element simulation calculation based on the boundary conditions and the plunger geometry. i );

[0025] Iterative optimization module, used to iteratively optimize the parameter a of the plunger inner cavity shape function based on the gradient descent method i ; until the termination condition is met, the optimal variable-section ultra-high-pressure plunger structure is obtained.

[0026] The beneficial effects of the design method of the variable cross-section ultra-high pressure plunger structure proposed in the present invention are:

[0027] 1. It breaks through the design paradigm of traditional homogeneous plunger structure. Under the premise of ensuring the lightweight requirement of plunger, the variable cross-section design matches the internal and external pressure difference of plunger with the cross-section stiffness, which can significantly reduce the deformation of plunger surface and is suitable for ultra-high pressure conditions.

[0028] 2. Users can flexibly choose a variety of variable cross-section structures such as conical, arc-shaped, and stepped shapes according to the actual working conditions of the plunger pump to balance the anti-deformation performance and lightweight requirements.

[0029] 3. The variable cross-section structural design does not require improvement of material or surface quality, does not increase additional costs, and is easy to process, with prospects for large-scale engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flow chart of a method for designing an ultra-high pressure plunger structure according to the present invention.

[0031] Figure 2 The load distribution on the plunger.

[0032] Figure 3 To optimize the plunger structure before and after.

[0033] Figure 4 Comparison of deformation of different plunger structures. DETAILED DESCRIPTION

[0034] In order to more clearly illustrate the embodiments of the present invention, the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] like Figure 1 As shown, the present invention provides a design method for an ultra-high pressure plunger structure with a variable cross-section, comprising the following steps:

[0036] Step 1: Set the load and boundary conditions on the plunger. The plunger ball head is a fixed constraint, and the oil load p on the inner wall of the plunger is inner That is the load pressure of the plunger pump, and the plunger outer wall load p outter It is determined by the oil film pressure formed by it and the cylinder hole. The pressure distribution is obtained by solving the pressure control equation of the annular gap flow:

[0037] (1)

[0038] (2)

[0039] Where x is the axial displacement of the plunger surface, L p is the axial length of the plunger, p H is the load high pressure of the plunger pump, p c The low pressure of the plunger pump housing. The load distribution is as follows Figure 2 shown.

[0040] Step 2: Construct a shape function to determine the inner cavity structure of the variable-section plunger. The change in the radius of the plunger's inner wall along the axial direction is defined as the shape function S. For a traditional cylindrical plunger with a constant inner cavity radius along the axial direction, it can be expressed as the following shape function:

[0041] (3)

[0042] Where r p is a constant inner cavity radius.

[0043] From the above analysis, it can be seen that the pressure difference between the inside and outside of the plunger wall is not uniform in the axial direction, but gradually increases from the bottom of the plunger to the ball head. However, the wall thickness of the traditional plunger is evenly distributed in the axial direction. Therefore, the stiffness of the plunger wall does not match the pressure difference distribution, resulting in significant surface deformation. Inspired by this, the present invention proposes a variable-section ultra-high-pressure plunger structure. In the area near the ball head where the pressure difference is large, the inner cavity cross-section is reduced to improve the interface stiffness and suppress deformation; in the area near the bottom of the plunger where the pressure difference is small, the inner cavity cross-section is appropriately increased to ensure the lightweight requirements of the plunger; in the middle area, a gradual cross-section is used as much as possible to concentrate the wall stress. The variable-section inner cavity can have various forms, including a conical inner cavity, an arc-shaped inner cavity, a stepped inner cavity, etc.

[0044] The inner radius of the cone decreases linearly along the axial direction, and its shape function is:

[0045] (4)

[0046] Where a t1 , a t2 is the control parameter of the cone-shaped inner cavity shape function.

[0047] The curved inner cavity structure optimizes stress distribution through continuous changes in curvature:

[0048] (5)

[0049] Where a c1 , a c2 is the control parameter of the arc-shaped inner cavity shape function.

[0050] The stepped inner cavity structure is the easiest to process, and segmented stiffness enhancement is achieved through discrete wall thickness jumps:

[0051] (6)

[0052] Where a s1 , a s2 … a skis the control parameter of the step inner cavity shape function, and k is the number of steps set.

[0053] By adjusting the parameter a of the shape function i The geometry of the plunger cavity can be flexibly adjusted to balance deformation resistance and lightweight requirements.

[0054] Step 3: Based on the aforementioned plunger structure and boundary condition settings, the deformation distribution D of the current plunger surface is obtained through finite element simulation calculation.

[0055] (7)

[0056] Step 4: Based on the gradient descent method, iteratively optimize the parameter a of the plunger inner cavity shape function i , so that the deformation of the plunger surface is minimized, that is:

[0057] (8)

[0058] Calculate the partial derivative of the objective function with respect to each parameter and obtain the gradient vector:

[0059] (9)

[0060] Update the shape parameters along the gradient descent direction:

[0061] (10)

[0062] At the same time, in order to ensure the lightweight requirements of the plunger, the mass of the ultra-high pressure plunger should not exceed the design value, so the parameter a i The search domain should satisfy the following constraints:

[0063] (11)

[0064] Where ρ is the material density and m is the plunger design mass. N (a i ) is the upper boundary of the shape function, i.e. the outer cylindrical surface of the plunger; S S (a i ) is the lower boundary of the shape function, i.e., the variable cross-section profile; S E (a i ) is the left boundary of the shape function, i.e. the plunger end face; S W (a i ) is the right boundary of the shape function, that is, the end face of the plunger close to the ball head.

[0065] Step 5: Repeat steps 2 to 4 until the termination condition is reached, that is, the optimal ultra-high pressure plunger structure is obtained. The termination condition is:

[0066] (12)

[0067] Where ∆D j is the extreme surface deformation of the current step, and ε is the convergence residual.

[0068] The present invention takes the plunger structure of a 7mL / r plunger pump product as an example, and optimizes the design in the form of a conical inner cavity, an arc inner cavity, and a stepped inner cavity respectively. The plunger quality before and after the optimization design remains unchanged. The corresponding optimized ultra-high pressure plunger structure is as follows Figure 3 shown.

[0069] Based on the finite element model, the surface deformation of different plunger structures under 42MPa high pressure working conditions was simulated, and the deformation of each plunger along the axial direction was extracted. The results are as follows: Figure 4 As shown in the figure, the conventional plunger exhibits significant uneven deformation distribution under the action of high-pressure oil. At the plunger base, the radial dimension shrinks by 2.34μm, while near the ball head, the plunger expands radially by 2.51μm, resulting in a surface deformation range of 4.85μm. Considering that the design tolerance of the typical plunger clearance is approximately 8-12μm to ensure lubrication, this deformation range significantly increases the risk of plunger seizure and wear during operation.

[0070] The ultra-high-pressure plunger design with a variable inner cross-section provided by the present invention can significantly reduce the deformation of the plunger surface, and the conical inner cavity, arc-shaped inner cavity, and stepped inner cavity all have good deformation suppression effects. The stepped inner cross-section plunger is the most convenient to process, with a surface deformation range of 2.4μm, which is 50.51% lower than the deformation of traditional plungers, but the stepped structure may bring about certain stress concentration. The arc-shaped inner cross-section has the best deformation suppression effect, with a maximum deformation of 1.89μm, which is 61% lower than the traditional plunger, but the processing requirements will be higher. The performance of the conical inner cross-section plunger is more comprehensive, with a maximum deformation of 1.94μm, which is 60% lower than the traditional plunger. It not only has a good deformation suppression effect, but also has a relatively low processing cost. In actual engineering applications, users can freely choose a variable-cross-section ultra-high-pressure plunger structure based on their own needs, weighing the anti-deformation ability and processing cost.

[0071] On the other hand, the present invention also provides a design system for implementing a design method for an ultra-high pressure plunger structure with a variable cross-section, the system comprising:

[0072] The plunger cross-section design module is used to construct a variable inner cavity cross-section plunger and design a variable inner cavity cross-section shape of the plunger to match the pressure difference between the inside and outside of the plunger with the cross-section stiffness; the change in the radius of the plunger inner wall along the axial direction is defined as the shape function S(a1, a2, ... a i ), determine the inner cavity structure of the variable cross-section plunger;

[0073] The simulation calculation module is used to obtain the deformation distribution D (a1, a2, ... a) of the current plunger surface through finite element simulation calculation based on the boundary conditions and the plunger geometry. i );

[0074] Iterative optimization module, used to iteratively optimize the parameter a of the plunger inner cavity shape function based on the gradient descent method i ; until the termination condition is met, the optimal variable-section ultra-high-pressure plunger structure is obtained.

[0075] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A design method for a variable cross-section ultra-high pressure plunger structure, characterized in that: The following steps are involved: (1) Set the load and boundary conditions on the plunger; (2) Construct a plunger with a variable inner cavity cross-section and design a variable inner cavity cross-section shape of the plunger so that the pressure difference between the inside and outside of the plunger matches the cross-section stiffness; define the change of the plunger inner wall radius along the axial direction as the shape function S(a1, a2, ... a i ), determine the inner cavity structure of the variable cross-section plunger; (3) Based on the boundary conditions and the plunger geometry, the deformation distribution D (a1, a2, ... a i ); (4) Based on the gradient descent method, iteratively optimize the parameter a of the plunger cavity shape function i ; (5) Determine whether the termination condition is met. If not, repeat steps (2) to (4) until the termination condition is met, that is, the optimal variable-section ultra-high-pressure plunger structure is obtained.

2. The design method of a variable-cross-section ultra-high-pressure plunger structure according to claim 1, characterized in that: In step (1), the loads on the inner and outer walls of the plunger are determined based on the axial displacement of the plunger surface, the axial length of the plunger, the high pressure load of the plunger pump, and the low pressure of the housing of the plunger pump.

3. The design method of a variable cross-section ultra-high pressure plunger structure according to claim 1, characterized in that: In step (2), the variable cross-section inner cavity structure includes a conical inner cavity, an arc-shaped inner cavity and a stepped inner cavity, and their corresponding shape functions are: Where a i is the control parameter of the shape function; specifically, a t1 , a t2 is the control parameter of the cone inner cavity shape function, a c1 , a c2 is the control parameter of the arc-shaped inner cavity shape function, a s1 , a s2 … a sk is the control parameter of the step cavity shape function, k is the number of steps set, and the geometric structure of the plunger cavity can be flexibly changed by adjusting the parameters.

4. The design method of a variable cross-section ultra-high pressure plunger structure according to claim 1, characterized in that: In step (4), the gradient descent optimization algorithm first calculates the partial derivative of the deformation distribution with respect to each parameter to obtain the gradient vector, and then updates the shape parameters along the gradient descent direction.

5. The method for designing a variable-cross-section ultra-high-pressure plunger structure according to claim 4, characterized in that: Shape parameter a i The search domain is constrained by the lightweight requirement of the plunger, and the search range of the parameter space should satisfy: Where ρ is the material density, m is the plunger design mass; S N (a i ) is the upper boundary of the shape function, i.e. the outer cylindrical surface of the plunger; S S (a i ) is the lower boundary of the shape function, i.e., the variable cross-section profile; S E (a i ) is the left boundary of the shape function, i.e. the plunger end face; S W (a i ) is the right boundary of the shape function, that is, the end face of the plunger close to the ball head.

6. The method for designing a variable-cross-section ultra-high-pressure plunger structure according to claim 1, characterized in that: In step (5), the termination condition is whether the degree of change of the surface deformation range of the current step relative to the surface deformation range of the previous step meets the requirements.

7. A design system for implementing the design method of the variable cross-section ultra-high pressure plunger structure according to any one of claims 1 to 6, characterized in that: The system includes: The plunger cross-section design module is used to construct a variable inner cavity cross-section plunger and design a variable inner cavity cross-section shape of the plunger to match the pressure difference between the inside and outside of the plunger with the cross-section stiffness; the change in the radius of the plunger inner wall along the axial direction is defined as the shape function S(a1, a2, ... a i ), determine the inner cavity structure of the variable cross-section plunger; The simulation calculation module is used to obtain the deformation distribution D (a1, a2, ... a) of the current plunger surface through finite element simulation calculation based on the boundary conditions and the plunger geometry. i ); Iterative optimization module, used to iteratively optimize the parameter a of the plunger inner cavity shape function based on the gradient descent method i ; until the termination condition is met, the optimal variable-section ultra-high-pressure plunger structure is obtained.

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