Plug preventing throttling valve spool entity structure based on lens-shaped section and forward design method thereof

Abstract

The application discloses a kind of anti-blocking throttling valve spool solid structure based on lenticular section and its forward design method, belong to oil and gas drilling technical field.The solid structure includes valve seat and axially movable valve core, three-dimensional cutting surface of valve core and valve seat inner wall are jointly enveloped to form throttling flow passage;In effective pressure control stroke section, the flow passage arbitrary cross section is lenticular area, the lenticular area is enclosed by two symmetrical circular arcs with equal radius equal to the reference radius R of valve seat inner hole, and the horizontal distance 2d of two circular arc centers gradually changes with the stroke of valve core.The application also provides a kind of forward design method, obtains theoretical flow area by fluid mechanics model, generates valve core curved surface by combining the numerical inverse solution characteristic parameters of the geometric mapping equation of the above lenticular section.The application reconstructs dispersion flow passage into large hydraulic diameter connected domain, reduces the probability of solid particle bridging and blocking, and realizes high-precision linear pressure control in full stroke.

Description

Technical Field

[0001] This invention relates to the field of oil and gas drilling technology, specifically to a pressure control throttle valve core structure with high hydraulic diameter and anti-clogging features, and its forward design method. Background Technology

[0002] In managed pressure drilling (MPD) systems in the oil and gas engineering field, the throttle valve, as the core actuator for precise wellbore pressure control, directly determines the stability and control accuracy of the fully automatic closed-loop pressure control system through its dynamic response characteristics and adjustment linearity. Currently, the throttle valve cores commonly used in the industry are mostly needle-shaped, conical, or conventional cylindrical structures. These traditional linear profile or conventional rotary valve cores have certain structural limitations in practical engineering applications. Specifically, when the traditional valve core cooperates with the valve seat for pressure regulation, its throttling channel essentially manifests as an annular gap. Under high pressure differential conditions and when maintaining a small opening to achieve a minimal flow area, the radial gap of this annular channel is compressed. From a hydrodynamic cross-sectional property perspective, the throttling area is distributed within a thin-walled annular space with a long wetted perimeter, resulting in a reduction in the system's effective hydraulic diameter and a tendency to generate geometric constraint effects.

[0003] Furthermore, the medium under actual pressure control conditions is typically a multiphase drilling fluid carrying heterogeneous solid particles (such as barite weighting agents, formation cuttings, etc.). When such high-pressure solid-containing fluids are displaced through the aforementioned tiny annular gaps, solid particle groups with diameters close to or larger than the radial gap threshold are prone to mechanical collisions, mutual compression, and embedding at the inlet of the flow channel or the narrow throat. The accumulation of a large number of particle groups can easily form a stable macroscopic arched stress structure, thereby triggering a "bridging effect" and causing local or overall flow channel blockage. Once the blockage condition is triggered, it will lead to the deterioration of the local flow field: the sudden reduction of the effective flow area forces a surge in local flow velocity in the unblocked area, thereby exacerbating the high-speed jet erosion and wear on the surface of the throttling element. At the same time, the obstruction of multiphase flow discharge will cause pressure buildup at the front end of the throttling port, causing the valve core and valve seat to mechanically jam under unbalanced hydraulic loads, affecting the normal operation of the automated pressure closed-loop control link of the MPD system.

[0004] At the level of existing design methodologies, the throttle valve core profile largely relies on engineering experience for shaping and subsequent inversion trial and error, lacking the support of forward design theory based on fluid dynamics constitutive equations and spatial mapping, making it difficult to meet the design requirements of the system for a smooth and predictable linear pressure drop response over a wide stroke range. Summary of the Invention

[0005] The technical problem this invention aims to solve is the structural limitation of traditional throttle valve cores, which easily form narrow, thin-walled annular flow channels at small openings, leading to a reduction in the effective hydraulic diameter. In multiphase fluid conditions (such as drilling fluids containing solids), this flow channel morphology increases the probability of triggering a "bridging effect" of solid particles, resulting in flow channel blockage, exacerbated local jet erosion, and mechanical jamming of the valve body. Furthermore, existing design methods relying on engineering experience for modification have limitations in achieving precise linear pressure drop response across the entire stroke range of the actuator. The purpose of this invention is to overcome the shortcomings of the prior art and provide a solid structure for an anti-clogging throttle valve core and its forward design method.

[0006] The technical solution of the present invention is as follows: On one hand, the present invention provides a solid structure of an anti-clogging throttle valve core based on a lens-shaped cross-section, characterized in that it includes a valve seat with a cylindrical hole inside and a valve core disposed within the cylindrical hole and capable of axial movement relative to the valve seat; the outer wall of the valve core is machined with a three-dimensional cutting surface, and the three-dimensional cutting surface and the inner wall surface of the valve seat together envelop and form a throttling flow channel; on any cross-section within the effective pressure control stroke of the valve core, the cross-sectional shape of the throttling flow channel is a lens-shaped region; the lens-shaped region is surrounded by two intersecting symmetrical arcs, one arc being the inner wall profile of the valve seat, and the other arc being the cross-sectional profile of the three-dimensional cutting surface; the radii of the two arcs are both equal to the reference radius R of the cylindrical hole of the valve seat, and the horizontal distance between the centers of the two arcs is 2d, where the horizontal distance 2d is a solid geometric feature variable that continuously changes with the axial stroke of the valve core.

[0007] On the other hand, the present invention provides a forward design method for manufacturing the solid structure of the anti-clogging throttle valve core as described in claim 1 or 2, characterized by comprising the following steps: obtaining the target operating parameters of the throttle valve core and the target control equation for the pressure drop changing with the stroke; constructing a numerical calculation model based on fluid mechanics principles, and calculating the theoretical pressure-controlled flow area required to achieve the target control equation at each stroke node of the valve core in combination with the operating parameters; establishing a nonlinear geometric mapping equation between the cross-sectional area of ​​the lens-shaped region and the horizontal distance 2d between the centers; substituting the theoretical pressure-controlled flow area at each stroke node into the nonlinear geometric mapping equation, and numerically inversely solving to obtain the horizontal distance 2d between the centers corresponding to each stroke node; and generating the three-dimensional cutting surface of the valve core based on the axial gradient law of the horizontal distance 2d between the centers corresponding to each stroke node.

[0008] Furthermore, the pressure drop at the inlet and outlet of the throttle valve The linear relationship with the valve core stroke Z is as follows:

[0009] in, This is the maximum design differential pressure of the throttle valve. To achieve the minimum design differential pressure for the throttle valve, This represents the maximum effective stroke of the valve core.

[0010] Furthermore, the fluid dynamics calculation model established based on the fluid continuity equation and the ideal Bernoulli equation is as follows:

[0011] in, For theoretical pressure control flow area, This refers to the drilling fluid discharge rate. Where is the area of ​​the valve seat inlet orifice, is the fluid density, C is the physical conversion constant related to the engineering unit system, and K is the dimensionless correction coefficient for the actual flow field.

[0012] Furthermore, assuming the radius of the valve seat reference circle is R, the lens-shaped region is formed by the intersection of two circular arcs with the same radius R and a center-to-center distance of 2d. The area of ​​this region is related to the distance from the axis of symmetry. The nonlinear transcendental equation between them is:

[0013] Where d is the cutting characteristic parameter (i.e., the distance of the axis of symmetry). By numerically solving this transcendental equation, the value of d corresponding to each stroke node can be obtained.

[0014] Furthermore, in step four, the coordinate generation method for the three-dimensional cutting surface of the valve core is as follows: With the valve core stroke defined as the Z-axis in the axial direction, the range of values ​​for the Y-coordinate of the cross-section width at any given stroke cross-section is as follows:

[0015] The X-coordinate equation of the three-dimensional cut surface of the valve core at the corresponding height is:

[0016] The continuous function is obtained by performing cubic spline interpolation along the Z-axis on the d-values ​​obtained at each node. Substituting these values ​​into the coordinate system above generates a spatial point cloud mesh, which in turn constructs a continuous and smooth three-dimensional cutting surface solid model.

[0017] Beneficial effects of the present invention Compared with the prior art, the present invention has the following beneficial effects: 1. The strong coupling relationship between the small flow area and the small radial clearance has been altered: This invention overcomes the structural limitations of traditional linear profile valve cores in forming extremely thin annular flow channels under small opening conditions. By using a lens-shaped cross-section formed by the intersection and envelope of the three-dimensional cut curved surface of the valve core and the inner wall of the valve seat as the main flow channel, the strong correlation and coupling state between the small flow area and the small radial clearance in the throttling design is changed in terms of physical structure.

[0018] 2. Increasing Hydraulic Diameter and Suppressing Bridging Blockage: While meeting the equivalent flow area required for the preset pressure control target, this invention utilizes a spatial surface mapping mechanism to reconstruct the traditionally dispersed annular flow region into a locally concentrated connected domain. This reconstruction design reduces the wetted perimeter of the flow channel cross-section, thereby increasing the hydraulic diameter at the throttling orifice and the effective unidirectional flow width. The macroscopic flow channel convergence characteristics alter the mechanical boundary conditions for mutual compression, embedding, and arching of solid particles in multiphase fluids containing solid phases (such as heterogeneous drilling fluids), thus reducing the probability of triggering the "bridging effect" at the underlying fluid dynamics level.

[0019] 3. Extended Equipment Service Life: Thanks to this structural characteristic, even under high pressure differential and small opening throttling conditions, the throttling mechanism can still ensure the discharge of larger diameter rock cuttings and weighting materials, reducing the probability of mechanical blockage caused by localized particle accumulation. Simultaneously, it mitigates localized erosion problems associated with blockage, extends the service life of the pressure control actuator under solid-liquid two-phase flow conditions, and improves the reliability of the control system.

[0020] 4. Achieved linear pressure control response across the entire stroke range: Through forward hydrodynamic derivation and inversion of nonlinear geometric transcendental equations, the final generated cutting surface follows the hydrodynamic setting rules. Compared with traditional empirical shaping, this design method can output a more stable linear pressure control response across the entire stroke range.

[0021] 5. Improved processing efficiency of forward design: This design method transforms fluid dynamics control objectives into numerical calculation models that can directly output three-dimensional coordinate matrices. The generated design point cloud data can be directly imported into 3D modeling software or CNC machining centers, shortening the R&D cycle and possessing good engineering versatility. Attached Figure Description

[0022] Figure 1 This is a function fitting curve of the distance between the axis of symmetry and the valve core stroke in an embodiment of the present invention; Figure 2 This is a schematic diagram showing the evolution of the flow channel as projected from the valve core cross-section onto the valve seat end face in an embodiment of the present invention; Figure 3 This is a schematic diagram of the three-dimensional cutting surface model of the valve core in an embodiment of the present invention; Figure 4 This is a three-dimensional schematic diagram of the structure of the valve core and valve seat mating inside the throttle valve in an embodiment of the present invention; Figure 5 This is a schematic diagram of the horizontal cross-sectional structure of the valve core and valve seat inside the throttle valve in an embodiment of the present invention; Figure 6This is a linear fitting curve of the relationship between valve core stroke and pressure drop in an embodiment of the present invention.

[0023] Explanation of reference numerals in the attached diagram: 1-valve seat; 2-valve core. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0025] Combination Figure 4 3D assembly drawings and Figure 5 As shown in the horizontal cross-sectional view, the throttle valve core structure designed in this embodiment of the invention mainly includes a cylindrical valve seat 1 and a throttle valve core 2 capable of axial linear motion.

[0026] Basic fit between valve seat and valve core: The valve seat 1 has a cylindrical reference inner hole with a constant inner diameter and a radius of [missing information]. The base of the throttle valve core 2 is an outer cylinder, and its outer cylindrical surface forms a dynamic sealing fit with the inner hole of the valve seat 1.

[0027] Spatial morphology of the three-dimensional cutting surface of the valve core: On the outer circumferential surface of the end of the valve core 2, a continuously gradually changing three-dimensional cutting surface is machined along its axial direction (Z-axis). From a macroscopic three-dimensional spatial perspective, this three-dimensional cutting surface appears as a smooth groove extending from the bottom to the top of the valve core 2. As the axial height changes, the cutting depth and cutting width of this groove exhibit a preset nonlinear gradual change law.

[0028] Cross-sectional characteristics of the lens-shaped flow channel: When the valve core 2 is assembled inside the valve seat 1, the three-dimensional cutting surface and the inner wall of the valve seat 1 together envelop each other, forming a throttling flow channel that allows fluid to pass through. At any height cross-section within the effective pressure control stroke of the valve core 2, the shape of this flow channel presents as a "lens-shaped region". Specifically, this lens-shaped region is surrounded by two intersecting symmetrical arcs: one arc comes from the fixed inner wall profile of the valve seat (1), and the other arc comes from the three-dimensional cutting surface cross-sectional profile of the valve core 2.

[0029] Dynamic adjustment and anti-clogging mechanism: The radii of the two arc segments constituting the lens-shaped region are both strictly equal to the reference radius of the inner hole of valve seat 1. Furthermore, the virtual centers of the two arcs are offset by a distance in the horizontal direction. When valve core 2 moves along the Z-axis under the drive of the actuator, the aforementioned horizontal distance between the centers... As a geometric characteristic variable of a solid, it undergoes continuous nonlinear changes with the valve core stroke, thereby precisely altering the size of the flow area of ​​the lens-shaped cross-section. During this dynamic adjustment process, because the flow channel always maintains a central convergence shape at the intersection of two circular arcs, it effectively overcomes the thin-walled annular gap that is easily generated by traditional linear valve cores at small openings, thus maintaining a large local hydraulic diameter at normal operating openings.

[0030] Valve Core Curved Surface Forward Design and Engineering Implementation Steps Step 1: Define the target equation for linear pressure control Based on the requirements of controlled pressure drilling, establish the pressure drop at the inlet and outlet of the throttle valve. With valve core (2) stroke Z The linear functional relationship between them:

[0031] in, This is the maximum design differential pressure of the throttle valve. To achieve the minimum design differential pressure for the throttle valve, This represents the maximum effective stroke of the valve core.

[0032] Step 2: Solve for the theoretical pressure-controlled flow area Based on the fluid continuity equation and Bernoulli's law of conservation of energy, a basic flow calculation equation for throttle valves is introduced, taking into account local energy losses and conversions to practical engineering units:

[0033] In the formula, Drilling fluid displacement, unit: m³ 3 / h; This represents the maximum cross-sectional area of ​​the valve seat inlet, in units of... ; Fluid density, in g / cm³ 3 ; The target pressure drop, determined in step one, varies linearly with the valve core stroke Z, and its unit is... K is the dimensionless correction coefficient for the actual flow field (set to 1.0 in the initial iteration, and subsequently adjusted by...). (Closed-loop simulation iterative correction); 5.09 is the conversion constant for practical engineering units.

[0034] By combining the above basic flow equations, the flow area under a given displacement and target pressure drop can be calculated, thus deriving the arbitrary valve core stroke. Theoretical controlled current area required for the next system The analytical solution model is as follows:

[0035] Step 3: Discretize and solve the transcendental equations of the lens-shaped cross-section geometry In this embodiment, the pressure control flow area at each valve core stroke node is achieved by the lens-shaped cross-section formed by the valve core (2) and the valve seat (1). The radius of the reference circle on the inner wall of the valve seat is set to R, and the lens-shaped region is essentially enclosed by two intersecting circular arcs with the same radius R. The area of ​​this lens-shaped cross-section is established. With respect to valve core cutting characteristic parameters (i.e., the distance between the two circular arc symmetry axes) (Nonlinear geometric transcendental equations between)

[0036] Step 4: 3D cutting surface smoothing and point cloud data export To prevent step vibration marks from appearing during CNC machining of the valve core (2), cubic spline interpolation is performed along the Z-axis on the obtained discrete distance d to obtain a smooth and continuous function. Its fitted curve is as follows Figure 1 As shown. Then, a three-dimensional spatial mesh matrix is ​​constructed. After setting the Y-coordinate of the cross-sectional width, the corresponding X-coordinate is calculated using the equation of a symmetrical circular arc:

[0037] Step 5: CFD flow field closed-loop simulation and correction coefficient acquisition Extract the generated valve core entity for flow field numerical simulation to obtain the actual simulated pressure drop. The theoretical design pressure drop and the simulated pressure drop were compared (comparison data are shown in Table 2), and the dimensionless correction coefficient for the actual flow field was extracted. Then, substitute back into step two to perform closed-loop iteration until the accuracy requirements are met.

[0038] To further verify the effectiveness and engineering feasibility of the above design method, this section provides a specific example of a drilling site pressure control condition.

[0039] 1. Initial parameter settings for the example In this embodiment, the drilling site operating parameters are set as follows: nominal diameter is 50.0 mm (i.e., valve seat reference circle radius R = 25 mm, rated displacement...). The drilling fluid density is 180 m³ / h. The maximum effective stroke of the valve core is 1.7 g / cm³. The pressure drop is 30mm. It is required that the pressure drop remains constant throughout the entire stroke, starting from the initial minimum differential pressure. Linearly reduce to the maximum design pressure difference at the end .

[0040] 2. Solving for theoretical characteristic parameters: Without adding the flow field correction coefficient initially (i.e., taking K=1), substitute the above operating parameters into the general control equations of steps one to three above, and numerically solve for the theoretical pressure-controlled flow area corresponding to each discrete stroke node. Distance from the axis of symmetry As shown in Table 1.

[0041] Table 1. Theoretical data for each travel node in the initial state (K=1) 3. Three-dimensional surface generation and correction iteration: Based on the data in Table 1, spline interpolation is performed along the Z-axis (e.g., Figure 1 As shown), and uses spatial coordinate equations to generate a three-dimensional cutting surface model of the valve core (such as...). Figure 3 (As shown in Table 3). Subsequently, CFD flow field simulation was performed on the solid model, and the actual pressure drop was extracted and compared with the theoretical pressure drop (as shown in Table 3). Table 2 shows the point cloud data (X,Y,Z) obtained by substituting Z=15 and K=1.0, with units of mm. Table 3 shows the data for (theoretical design pressure drop and simulated pressure drop - stroke). By comparing the theoretically designed pressure drop with the simulated pressure drop, a correction function for the actual flow field is obtained. :

[0042] Will Substitute back into the fluid dynamics model for the second round of iteration, and finally output the corrected three-dimensional coordinate final characteristic parameters (as shown in Table 3) and matrix (as shown in excerpt from Table 5).

[0043] Table 4. Flow coefficients of valve core at different strokes through the actual flow field. The corrected theoretical flow area and distance from the axis of symmetry to the valve seat center are... Table 5 uses Z=15 and substitutes the dimensionless correction coefficients for the flow field. The three-dimensional coordinate matrix (X,Y,Z) and point cloud data (txt) are obtained, with units of mm. 4. Implementation effect verification: After the valve core (2) entity generated by the final closed-loop iteration of the method in this embodiment is matched with the valve seat (1) (as shown in the figure) Figure 4 , Figure 5 As shown in the figure, this effectively reduces the calculation deviation caused by three-dimensional eddies. Simulation tests show that, as Figure 6 As shown, its stroke and pressure drop exhibit a good linear relationship, verifying the pressure control capability of the design method of this invention under high-pressure multiphase flow conditions.

[0044] Although this embodiment uses two circular arcs of equal radius to construct a lens-shaped cross section, those skilled in the art will understand that non-uniform diameter lens-shaped cross sections constructed using similar elliptical arcs, parabolas, or other smooth transition surfaces, as long as they can achieve the concentration of hydraulic diameter, fall within the protection scope of this invention.

Claims

1. A physical structure for an anti-clogging valve core throttle valve based on a lens-shaped cross-section, characterized in that, The valve includes a valve seat (1) with a cylindrical hole inside and a valve core (2) disposed in the cylindrical hole and capable of axial movement relative to the valve seat; the outer wall of the valve core (2) is machined with a three-dimensional cutting surface, which together with the inner wall of the valve seat (1) forms a throttling flow channel; at any cross-section within the effective pressure control stroke of the valve core (2), the cross-sectional shape of the throttling flow channel is a lens-shaped region; the lens-shaped region is enclosed by two intersecting symmetrical arcs, one arc being the inner wall profile of the valve seat (1) and the other arc being the cross-sectional profile of the three-dimensional cutting surface; the radii of both arcs are equal to the reference radius of the cylindrical hole of the valve seat (1). Furthermore, the horizontal distance between the centers of the two arc segments is 2d, and the horizontal distance between the centers 2d is a solid geometric feature variable that changes continuously with the axial stroke of the valve core (2).

2. The physical structure according to claim 1, characterized in that, The gradient rate of the horizontal spacing 2d between the centers along the axial travel of the valve core is configured such that, under fluid conditions, the pressure drop at the inlet and outlet of the throttling flow channel exhibits a linear functional relationship with the axial travel of the valve core.

3. A forward design method for manufacturing the solid structure of the anti-clogging throttle valve core as described in claim 1 or 2, characterized in that, Includes the following steps: Obtain the target operating parameters of the throttle valve and the target control equation for pressure drop as a function of stroke; A numerical calculation model is constructed based on fluid mechanics principles. Combined with the operating parameters, the theoretical pressure-controlled flow area required to achieve the target control equation at each valve core stroke node is calculated. The cross-sectional area of ​​the lens-shaped region and the horizontal distance from its center are established. The nonlinear geometric mapping equation between them; Substituting the theoretical pressure-controlled flow area at each stroke node into the nonlinear geometric mapping equation, the inverse numerical solution is used to obtain the horizontal center-to-center spacing 2d corresponding to each stroke node; based on the horizontal center-to-center spacing corresponding to each stroke node... The gradual change along the axial direction generates the three-dimensional cutting surface of the valve core.

4. The design method according to claim 3, characterized in that, Pressure drop at the inlet and outlet of the throttle valve The linear functional relationship between the valve core stroke Z and the valve core stroke Z is as follows: ,in, This is the maximum design differential pressure of the throttle valve. This is the minimum design differential pressure for the throttle valve. This represents the maximum effective stroke of the valve core.

5. The forward design method according to claim 3, characterized in that... In calculating the theoretical pressure-controlled flow area The numerical calculation model is based on the fluid continuity equation and the ideal Bernoulli equation, and the derived analytical solution model is as follows: in, For theoretical pressure control flow area, For drilling fluid discharge, The area of ​​the valve seat inlet channel. Where C is the fluid density, C is the physical conversion constant related to the engineering unit system, and K is the dimensionless correction factor for the actual flow field.

6. The forward design method according to claim 3, characterized in that... The cross-sectional area of ​​the lens-shaped region With cutting characteristic parameters The nonlinear geometric mapping equation between them is: .

7. The forward design method according to claim 3, characterized in that, The steps for generating the three-dimensional cutting surface include: performing continuous spline interpolation fitting on the discrete horizontal spacing d between the center points along the valve core axis; setting the cross-sectional cutting width variable, and combining the geometric symmetry constraint of the double circular arc to establish a spatial mapping coordinate relationship between the cross-sectional width and the cutting depth, so as to generate a three-dimensional point cloud mesh.

8. The forward design method according to claim 3, characterized in that, After generating the three-dimensional cutting surface, the process further includes a flow field closed-loop iterative correction step: extracting the generated solid surface model for CFD flow field numerical simulation to obtain the actual simulated pressure drop; comparing the actual simulated pressure drop with the theoretical target pressure drop to extract the actual flow field correction function that varies with the stroke. The correction function Substitute the solutions back into the numerical calculation model and iterate again until the simulated voltage drop meets the linearity accuracy requirement.

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