Design method of pressure control throttle valve with pressure drop linearly changing along with stroke

Abstract

The invention discloses a design method of a pressure control throttle valve with the pressure drop linearly changing along with the stroke, and belongs to the technical field of automation of oil and gas exploitation equipment.The design method comprises the following steps that the linear relation between the pressure drop and the stroke of the throttle valve serves as a target; a mathematical model of a valve element contour is established by establishing a minimum throttling area equation of a cylindrical valve and a wedge-shaped valve, correcting a flow pressure drop characteristic equation and deducing a differential pressure linear adjustment equation, a valve element contour curve meeting the linear requirement is deduced through variable-diameter contour optimization design, and therefore the valve element structure of the throttling valve is obtained. By means of the design method, the valve element contour curve with the wider linearity range of pressure control adjustment and the better precision can be obtained, and the design method is more efficient and universal.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil drilling, in particular to a design method of a pressure control throttle valve with linear pressure drop along stroke, which is especially used in pressure control drilling. BACKGROUND

[0002] Under the drive of digital transformation, the global oil and gas field is accelerating the upgrading process of pressure control drilling technology to intelligent closed-loop control system. As the key execution terminal for wellhead pressure balance regulation and control, the dynamic response characteristics of the throttle valve play a crucial role in the stability of the pressure control loop. However, oilfield test data shows that the traditional pressure control throttle valve generally has a nonlinear response characteristic between opening and pressure drop. This nonlinear characteristic not only restricts the data acquisition accuracy of the control system, but also seriously hinders the effective implementation of the automatic pressure regulation function in engineering practice. Therefore, achieving the linear response characteristic between the opening and pressure drop of the throttle valve has extremely important theoretical and engineering significance for building an intelligent closed-loop pressure control drilling system.

[0003] Currently, related researches mainly focus on the linearization design of cylindrical throttle valves, while the research on other types of throttle valves widely used in pressure control drilling engineering (such as wedge-shaped throttle valves) is still relatively lacking, and a universal design theory system has not yet been formed. The development of linear opening-pressure drop throttle valves faces many technical challenges, including the difficulty in establishing a minimum flow area calculation model, the difficulty in expressing the dynamic mapping relationship between the valve core stroke and the minimum flow area, and the unclear flow transition regulation mechanism of the valve core geometry, etc. In addition, the linear pressure control cylindrical throttle valve designed by the existing technology can only achieve linear pressure control within the opening range of 20% to 80%, which cannot meet the design requirements of high-precision execution terminals for intelligent closed-loop pressure control drilling systems.

[0004] Therefore, in order to solve the problem of narrow linear pressure control range and unable to meet the multi-phase flow drilling (MPD) technical requirements of the existing throttle valve pressure control, it is urgent to develop a design method of pressure control throttle valve with linear relationship between stroke and pressure drop, and design the valve core through this method to achieve linear pressure control of the throttle valve, so as to achieve precise throttling. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a design method of a pressure control throttle valve with linear pressure drop along stroke, which can obtain a valve core profile curve with wider linear pressure control regulation range and better accuracy, and the design method is more efficient and universal, and can be applied to cylindrical, needle-shaped and wedge-shaped valve core design.

[0006] The technical solution of the present application is to provide a design method of a pressure control throttle valve with linear pressure drop along stroke, which comprises the following steps:

[0007] The linear relationship between the pressure drop and the stroke of the throttle valve is taken as the target, the minimum throttling area equation of the cylindrical throttle valve and the wedge-shaped throttle valve (hereinafter referred to as "cylindrical valve" and "wedge-shaped valve") is established, the pressure difference linear regulation equation is derived, the mathematical model of the valve core profile is established, the valve core profile curve meeting the linear requirement is derived through the variable diameter profile optimization design, and thus the valve core structure of the throttle valve is obtained.

[0008] Compared with the prior art, the design method of the throttle valve with the linear change of the pressure drop with the stroke has the following advantages. The profile curve of the valve core can be obtained through the method, compared with the existing cylindrical valve and wedge-shaped valve core, the pressure control linearity range of the valve core adopting the curve profile meeting the linear relationship between the pressure drop and the stroke of the throttle valve is wider and the regulation accuracy is better. Moreover, the method can be universally used for the design of the needle-shaped, cylindrical and wedge-shaped valve cores, and then the corresponding valve core profile curve and valve core structure are obtained according to the target and design parameters of the specific valve core, and the method is more universal. Therefore, the design method can improve the design efficiency and is more efficient.

[0009] In one embodiment, the geometric expression of the minimum throttling area of the cylindrical valve is: Wherein, A rt is the minimum throttling area of the cylindrical valve core, R is the inner diameter of the valve seat, r is the equivalent diameter corresponding to the minimum throttling cross section of the valve core at the stroke y, and dL is the axial distance from the characteristic point to the valve seat.

[0010] In one embodiment, the geometric expression of the minimum throttling area of the wedge-shaped valve is: Wherein, A rx is the minimum throttling area of the wedge-shaped valve core; b(y) is an area characteristic function about the stroke y, which is obtained through nonlinear regression of test data; R is the throttling surface radius of the wedge-shaped valve core; u = x-(h-R); and θ is the included angle between the throttling area and the bottom projection.

[0011] In one embodiment, the relationship between the pressure drop △P and the stroke y of the valve core is: Wherein P m is the maximum pressure difference between the inlet and the outlet of the throttle valve; L m is the maximum stroke of the valve core of the throttle valve.

[0012] In one embodiment, the pressure drop flow characteristic of the throttle valve includes that the fluid passing through the throttle valve should satisfy the Bernoulli equation and the continuity equation of the fluid, and the influence of flow transition on the pressure control of the throttle valve is considered, and thus the modified flow pressure drop characteristic equation is obtained, Wherein Q is the fluid flow passing through the valve body, a is a kinetic energy correction coefficient, A r is the minimum throttling area of the fluid, A is the valve seat hole area, and ρ is the fluid density.

[0013] In one embodiment, the curve profile of the throttle valve is formed by using an outer envelope of a parameterized straight line cluster stroke, a mathematical model is established by a minimum throttle area equation, a modified flow pressure drop characteristic equation, and a parameterized straight line cluster, which is represented by a resulting pressure difference linear adjustment equation wherein Ft or Fx represents the equation of the cylindrical valve and the wedge valve respectively.

[0014] In one embodiment, if Ft = 0, Fx = 0, an equivalent area straight line cluster composed of equivalent area straight lines at each stroke of the cylindrical valve and the wedge valve is obtained, and a valve core profile curve trajectory equation satisfying the linear requirement is derived by satisfying the formula

[0015] In one embodiment, an initial assumption characteristic function b(y) as = 1 is made, a theoretical throttle area A th is calculated, an actual throttle area A act is obtained by three-dimensional modeling, an area deviation at different strokes y is extracted, and a six-order polynomial regression fitting is performed, i.e. b(y) = a1y + a2y 2 + … + a6y 6 , wherein the coefficients a1, a2, …, a6 represent the dynamic law of the nonlinear correction amount of the throttle area changing with the stroke.

[0016] In one embodiment, the design method of the cylindrical valve is applicable to the needle throttle valve.

[0017] In a preferred embodiment, under the conditions that the working condition is a drilling fluid pump displacement of 72 m 3 / h, the drilling fluid density is 1700 g / cm 3 , the maximum regulating pressure of the throttle valve is 100 kPa, and the maximum stroke of the valve core is 30 mm, the profile curve of the wedge valve and the cylindrical valve core is designed for a nominal diameter of 50.8 mm, and the wedge valve core is made to have a linear relationship between the pressure drop ΔP and the valve core stroke y within 16% to 93% of the effective stroke, and the cylindrical valve core is made to have a linear relationship between the pressure drop ΔP and the valve core stroke y within 20% to 93% of the effective stroke.

[0018] In a preferred embodiment, the valve core profile points of the throttle valve are obtained every 1 mm within the range of 16% to 93% for the wedge valve core and within the range of 20% to 93% for the cylindrical valve core, and the profile curve of the valve core and the trajectory equation of the profile curve are obtained by fitting the obtained valve core profile points:

[0019] y t = -3.38505x 5 - 391.92183x 4 - 18153.17224x 3 - 420464.27744x 2 ​-4869948.60749x -22564411.86913;

[0020] y x = 0.00019x 5 - 0.00879x 4 + 0.17112x 3 - 1.63450x 2 + 8.23645x - 13.34579.

[0021] In a preferred embodiment, the valve core profile curve equation of the cylindrical valve and the wedge valve is simulated, and the stroke-pressure drop curve is drawn to verify. After the profile structure of the valve core is fitted, it is verified whether the stroke-pressure drop cylindrical curve and the wedge curve are in a linear relationship within 20% to 93% and 16% to 93% effective stroke. If the condition is met, the designed valve core profile meets the design requirements, and the linearity range of pressure control adjustment is wider and the accuracy is better when the throttle valve is used for pressure control drilling. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Fig. 1 is a schematic diagram of a throttle area of a throttle valve designed according to the design method of the present application.

[0023] Figure 2 Fig. 2 is a three-dimensional schematic diagram of the minimum throttle area of a wedge-shaped throttle valve. Figure 1 Fig. 3 is a micro-section schematic diagram of the minimum throttle area of a wedge-shaped throttle valve.

[0024] Figure 3 Fig. 4 is a schematic diagram of a linear cluster envelope of a cylindrical valve core and a wedge valve core. Figure 2 Fig. 5 is a schematic diagram of a linear cluster envelope of a cylindrical valve core and a wedge valve core.

[0025] Figure 4 Fig. 6 is a wedge valve core profile curve fitted according to the valve core of Fig. 1.

[0026] Figure 5 Fig. 7 is a cylindrical valve core profile curve fitted according to the valve core of Fig. 1. Figure 4

[0027] Fig. 8 is a stroke-pressure drop relationship curve of the wedge valve core in Fig. 1. Figure 6 Figure 4 Fig. 9 is a stroke-pressure drop relationship curve of the cylindrical valve core in Fig. 1.

[0028] Figure 7 Figure 5 DETAILED DESCRIPTION

[0029] Figure 8 Figure 6 DETAILED DESCRIPTION ​​​​

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] In one embodiment of the design method according to the present invention, the operating condition is a drilling fluid pump displacement of 72m³ / h. 3 / h, drilling fluid density 1700g / cm³ 3 With a maximum regulating pressure of 100 kPa and a maximum valve core stroke of 30 mm, the valve core profile curves for cylindrical and wedge valves with a nominal diameter of 50.8 mm are designed. It is readily understood that the design of the 50.8 mm valve core and the design of the cylindrical and wedge valves in the specific embodiments of this invention are merely exemplary. The design method of this invention is applicable to valve cores of any size, such as cylindrical valve cores of 38.1 mm, needle valve cores of 25.4 mm, and wedge valve cores of 76.2 mm.

[0032] In one embodiment, when designing 50.8mm cylindrical valve and wedge valve spools, it is required that the stroke and pressure drop have a linear relationship within 20% to 93% of the effective stroke of the cylindrical valve spool and 16% to 93% of the effective stroke of the wedge valve spool.

[0033] 1) The objective of establishing a linear relationship between the valve core stroke and pressure drop can be expressed by the following formula:

[0034]

[0035] 2) According to Figure 1 , Figure 2 , Figure 3 Given a specific valve core position, and assuming the minimum distance between the valve core and valve seat is NB, then the flow area A of the cylindrical valve is... rt This refers to the lateral surface area of ​​the frustum NBCM and the flow area A of the wedge valve in the diagram. rx It's what's left after the cone ENH is truncated by EF. Figure 2 The formula for the minimum throttling area of ​​the black region is:

[0036]

[0037] Additionally, R is the valve seat inner diameter, r is the equivalent diameter corresponding to the minimum throttling section of the valve core at stroke y, dL is the axial distance from the feature point to the valve seat, and A... rx Let be the minimum throttling area of ​​the wedge valve core, b(y) be the area characteristic function with respect to stroke y, obtained by nonlinear regression of experimental data, R be the radius of the throttling surface of the wedge valve core, u = x - (hR) and θ be the angle between the throttling area and the bottom projection.

[0038] 3) The existing flow rate and pressure drop characteristic equation is modified as follows:

[0039]

[0040] a is the kinetic energy correction factor, A r is the minimum throttling area of the fluid.

[0041] 4) According to Figure 1 and Figure 4 the above formula, the linear cluster parameterization formula of the cylindrical valve core and the wedge-shaped valve core is established t and F x :

[0042]

[0043] 5) Let F t and F x (Hereinafter referred to as F) be 0, since the contour line of the signal is tangent to all straight lines, so the valve core contour curve satisfies:

[0044]

[0045] Solving this equation can obtain the contour equation of the valve core.

[0046] 6) The units of various parameters are as follows: the unit of the flow area A is cm2; the unit of the pressure drop ΔP is 100 KPa; the unit of the fluid density ρ is g / cm3; the unit of the flow rate Q is m3 / h.

[0047] 7) The throttling valve core contour points of the wedge-shaped valve core in the range of 16% to 93% and the cylindrical valve core in the range of 20% to 93% are obtained every 1 mm, as shown in the following Table 1-1 and Table 1-2:

[0048] Table 1-1 Contour data points of cylindrical throttling valve

[0049]

[0050] Table 1-2 Contour data points of wedge-shaped throttling valve

[0051]

[0052]

[0053] 8) The valve core contour line is obtained according to the obtained coordinate values, as shown in Figure 5 , 6 , and the contour curve equation obtained by fitting is:

[0054] y t = -3.38505x 5 -391.92183x 4 -18153.17224x 3 -420464.27744x2 -4869948.60749x-22564411.86913;

[0055] y x =0.00019x 5 -0.00879x 4 +0.17112x 3 -1.63450x 2 +8.23645x-13.34579.

[0056] 9) Based on the method of this invention, a contour curve is designed, and a program is written using Matlab software to simulate it, plotting the stroke-pressure drop curves of the cylindrical valve and the wedge valve as shown below. Figure 7 , 8 As shown.

[0057] Depend on Figure 6 , 7 It can be seen that the wedge valve core exhibits a good linear relationship between stroke and pressure drop within the opening range of 16% to 93% and the cylindrical valve core exhibits a good linear relationship within the opening range of 20% to 93%, which fully meets the design requirements.

[0058] Although the present invention has been described in conjunction with specific embodiments, it is understood that various modifications or substitutions can be made without departing from the scope of the invention. In particular, features in the various embodiments can be combined with each other as long as there is no structural conflict, and the resulting combined features still fall within the scope of the present invention. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A design method for a pressure-controlled throttle valve where the pressure drop varies linearly with the stroke, comprising the following steps: With the goal of establishing a linear relationship between the pressure drop and stroke of the throttle valve, a mathematical model of the valve core profile is established by creating the minimum throttling area equation for cylindrical throttle valves and wedge throttle valves (hereinafter referred to as "cylindrical valves" and "wedge valves"), modifying the flow rate and pressure drop characteristic equation, and deriving the differential pressure linear regulation equation. Through variable diameter profile optimization design, the valve core profile curve that meets the linear requirements is derived, thereby obtaining the valve core structure of the throttle valve.

2. The method according to claim 1, characterized in that, The geometric expression for the minimum throttling area of ​​a cylindrical valve is: Among them, A rt Let be the minimum throttling area of ​​the cylindrical valve core, R be the inner diameter of the valve seat, r be the equivalent diameter corresponding to the minimum throttling section of the valve core at stroke y, and dL be the axial distance from the feature point to the valve seat; the geometric expression for the minimum throttling area of ​​the wedge valve is: Among them, A rx y is the minimum throttling area of ​​the wedge valve core; b(y) is the area characteristic function with respect to stroke y, obtained by nonlinear regression of experimental data; R is the radius of the throttling surface of the wedge valve core; u = x - (hR); θ is the angle between the throttling area and the bottom projection.

3. The method according to claim 1, characterized in that, The relationship between pressure drop ΔP and valve core stroke y is as follows: Where P m L represents the maximum pressure difference between the inlet and outlet of the throttle valve. m This represents the maximum stroke of the throttle valve core.

4. The method according to claim 1, characterized in that, The pressure drop-flow characteristics of a throttle valve include the fluid passing through the valve satisfying Bernoulli's equation and the fluid continuity equation. Simultaneously, the influence of flow transition on the throttle valve's pressure control must be considered, resulting in a modified flow-pressure drop characteristic equation. Where Q is the fluid flow rate through the valve body, a is the kinetic energy correction coefficient, and A r Let A be the minimum throttling area of ​​the fluid, ρ be the valve seat orifice area, and ρ be the fluid density.

5. The method according to claim 1, characterized in that, The throttle valve's profile is formed using the circumferential envelope of a parameterized family of linear curves. A mathematical model is established using the minimum throttling area equation, the modified flow-pressure drop characteristic equation, and the parameterized family of linear curves. This mathematical model is derived from the obtained differential pressure linear regulation equation. Let Ft or Fx represent the equations for the cylindrical valve and the wedge valve, respectively.

6. The method according to claim 1, characterized in that, If we set Ft = 0 and Fx = 0, we obtain a set of straight lines representing the lower profile tangents of the cylindrical valve and the wedge valve at each stroke, and then satisfy the formula... The equation for the valve core profile curve trajectory that satisfies the linearity requirement is derived.

7. The method according to claim 3, characterized in that, Initial assumption: characteristic function b(y) as =1, calculate the theoretical throttling area A th The actual throttling area A is obtained through 3D modeling. act The area deviation under different travel distances y is extracted, and a sixth-order polynomial regression is performed to fit the equation, i.e., b(y) = a1y + a2y. 2 +…+a6y 6 In the formula, the coefficients a1, a2, ..., a6 characterize the dynamic law of the nonlinear correction amount of the throttling area changing with the stroke.

8. The method according to any one of claims 2, 4, 5, 6, 7, and 8, characterized in that, The design of cylindrical valves is suitable for needle valves.

9. The method according to any one of claims 1 to 7, characterized in that, Under operating conditions, the drilling fluid pump displacement is 72m³ / h. 3 / h, drilling fluid density 1700g / cm³ 3 With a maximum regulating pressure of 100 kPa and a maximum valve core stroke of 30 mm, design the valve core profile curves of a wedge valve and a cylindrical valve with a nominal diameter of 50.8 mm, and make the pressure drop ΔP of the wedge valve core and the valve core stroke y linearly related within the effective stroke range of 16% to 93% and 20% to 93% of the cylindrical valve core, respectively.

10. The method according to claim 9, characterized in that, For wedge valve cores (16%–93%) and cylindrical valve cores (20%–93%), valve core profile points were calculated at 1mm intervals. Based on these profile points, fitting was performed to obtain the profile curves and corresponding trajectory equations y for the cylindrical and wedge valve cores, respectively. t and y x : y t =-3.38505x 5 -391.92183x 4 -18153.17224x 3 -420464.27744x 2 -4869948.60749x-22564411.86913; y x =0.00019x 5 -0.00879x 4 +0.17112x 3 -1.63450x 2 +8.23645x-13.34579; Preferably, the contour curve equation of the valve core is simulated, and the curve of stroke versus pressure drop is plotted for verification.

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