A reciprocating pump with a simple harmonic motion of a linear motor mover and its current control method

Abstract

The present invention discloses a reciprocating pump with a simple harmonic motion of a linear motor mover and its current control method, which relates to the technical field of linear motor reciprocating pumps, and includes a stator winding, a mover assembly, a pump barrel and a plunger. The stator winding is sleeved outside the mover push rod. The top end of the mover assembly is fixedly connected to the plunger, and a compression spring is also connected between the two. The plungers are all located in the pump barrel. By controlling the current to change along a sine curve, the present invention can avoid the sudden increase in the force of the mover push rod during the upward movement, causing the problem of excessive extrusion between the mover push rod and the plunger. At the same time, during the downward movement, it can also prevent the problem that the plunger and the liquid column generate a large impact on the mover push rod under the action of inertia, thereby reducing the loss of the mover push rod during the reciprocating process and prolonging the service life of the linear motor.

Description

Technical Field

[0001] The present invention relates to the technical field of linear motor reciprocating pumps, and particularly to a reciprocating pump with a simple harmonic motion of a linear motor mover and a current control method therefor. Background Art

[0002] Currently, in oilfield production, reciprocating pumps generally use crank-link mechanisms, cam mechanisms, etc. as the power end. However, the crank-link reciprocating pump has a large flow rate and large pressure pulsation; the cam mechanism of the reciprocating pump at the power end is prone to wear, has low reliability, and still has flow pulsation. The linear motor reciprocating pump can well optimize the above disadvantages.

[0003] A linear motor is a device that directly converts electrical energy into linear motion mechanical energy without any conversion device, simplifies the device, and effectively improves the reliability and transmission efficiency of the reciprocating pump. Since the linear motor moves smoothly and at a constant speed, theoretically, the pulsation of the output flow rate and pressure of the reciprocating pump is basically eliminated.

[0004] For a linear motor reciprocating pump, after alternating current is applied, a thrust is generated on the mover push rod through the mover and the stator winding, and is applied to the plunger, thereby realizing the up and down movement of the reciprocating pump. During the upward movement, the fixed valve is opened due to the pressure difference, and the liquid enters the tubing. During the downward movement, the traveling valve is opened due to the pressure difference, and the liquid enters the pump barrel. For example, the invention patent with the application number "200510085297.7" and the name "Linear motor lifting device for double-acting reciprocating pump" and the invention patent with the application number "202110079065.X" and the name "A linear motor reciprocating pump suitable for high gas-liquid ratio".

[0005] However, in the actual operation of a linear motor reciprocating pump, when the plunger moves upward, the current suddenly increases, and the generated thrust will immediately increase accordingly, which will cause certain damage to both the mover push rod and the plunger. At the same time, when the plunger moves downward, it only moves downward by the gravity of the plunger, and the plunger suddenly stops. The liquid column existing in the tubing and the pump barrel will indirectly cause great damage to the mover push rod due to inertia. The greater the output, the greater the damage caused. The relationship between current and time is as Figure 6 , and the relationship between plunger speed and time is as Figure 7 .

[0006] Therefore, if the magnitude of the current is controlled to generate different induced voltages in the stator winding, the force of the mover push rod will also change accordingly. Finally, under the condition of ensuring the normal operation of the linear motor reciprocating pump, the speeds of the upward and downward movements of the plunger are changed, and the impact force on the mover push rod generated by the inertia of the liquid column and the plunger is reduced, which is of great significance for protecting the mover push rod and extending its service life. Summary of the Invention

[0007] The object of the present invention is to provide a reciprocating pump with a simple harmonic motion of a linear motor mover and its current control method, so as to solve the problems existing in the prior art, reduce the loss of the mover push rod during reciprocation, and extend the service life of the linear motor.

[0008] To achieve the above object, the present invention provides the following solution: The present invention provides a reciprocating pump with a simple harmonic motion of a linear motor mover, including a stator winding, a mover assembly, a pump barrel and a plunger. The stator winding is sleeved outside the mover push rod. The top end of the mover assembly is fixedly connected to the plunger, and a compression spring is also connected between the two. The plunger is located in the pump barrel.

[0009] Preferably, the mover assembly includes a mover body and a mover push rod fixed on the mover body. The mover push rod is fixedly connected to the plunger, and a compression spring is connected between the mover push rod and the plunger.

[0010] Preferably, an oil pipe is connected to the top of the pump barrel.

[0011] Preferably, a traveling valve is arranged in the plunger, and a fixed valve is arranged in the upper part of the pump barrel.

[0012] Preferably, it further includes a casing, and the pump barrel and the oil pipe are both arranged inside the casing.

[0013] Preferably, the stator winding is fixed inside the casing through a fixing member.

[0014] The present invention also provides a current control method for the reciprocating pump with a simple harmonic motion of the linear motor mover. When the mover push rod drives the plunger to move upward, the magnitude of the current passed into the linear motor increases from 0 to the peak value i max1 , and then decreases to 0. When the plunger moves to the top of the stroke, the change of the current magnitude with time conforms to the sine curve change law, and when i = a < i max1 , the magnitude of the thrust of the mover push rod is equal to the gravity of the plunger; when the mover push rod moves downward, the magnitude of the current passed into the linear motor increases from 0 to the peak value i max2 , and then decreases to a. When the plunger moves to the bottom of the stroke, the change of the current magnitude with time conforms to the sine curve change law, and a < i max2 < i max1 .

[0015] The present invention has obtained the following technical effects compared with the prior art:

[0016] 1. By controlling the current to vary along a sine curve, the present invention can avoid the sudden increase in the force of the moving plunger rod during upward movement, thus preventing the problem of excessive extrusion between the moving plunger rod and the plunger. At the same time, during downward movement, it can also prevent the problem of a large impact on the moving plunger rod caused by the plunger and the liquid column under the action of inertia, thereby reducing the loss of the moving plunger rod during reciprocation and extending the service life of the linear motor.

[0017] 2. In the present invention, a compression spring is also provided between the moving plunger rod and the plunger. When the linear motor fails, the spring can buffer the plunger and prevent it from hitting the moving plunger rod under the action of inertia. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0019] Figure 1 It is a schematic structural diagram of the upper part of the linear motor reciprocating pump in the present invention;

[0020] Figure 2 It is a schematic structural diagram of the lower part of the linear motor reciprocating pump in the present invention

[0021] Figure 3 It is a basic working principle diagram of the mover and stator winding in the linear motor;

[0022] Figure 4 It is a relationship curve diagram of current and time in the present invention;

[0023] Figure 5 It is a relationship curve diagram of plunger speed and time in the present invention;

[0024] Figure 6 It is a relationship curve diagram of current and time in the prior art;

[0025] Figure 7 It is a relationship curve diagram of plunger speed and time in the prior art;

[0026] Among them, 1. Oil pipe; 2. Fixed valve; 3. Traveling valve; 4. Plunger; 5. Pump barrel; 6. Spring; 7. Moving plunger rod; 8. Casing; 9. Mover body; 10. Fixed part; 11. Stator winding. DETAILED DESCRIPTION OF THE INVENTION

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] The object of the present invention is to provide a reciprocating pump with a linear motor mover performing simple harmonic motion and its current control method to solve the problems existing in the prior art, which can reduce the loss of the mover push rod during the reciprocating process and extend the service life of the linear motor.

[0029] To make the above objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0030] Embodiment 1:

[0031] As Figures 1 to 2 shown, this embodiment provides a reciprocating pump with a linear motor mover performing simple harmonic motion, including a stator winding 11, a mover assembly, a pump barrel 5, and a plunger 4. The stator winding 11 is sleeved outside the mover assembly. The top end of the mover assembly is fixedly connected to the plunger 4, and a compression spring 6 is also connected between them. The plunger 4 is located in the pump barrel 5.

[0032] Further, the mover assembly includes a mover body 9 and a mover push rod 7 fixed on the mover body 9. The mover push rod 7 is fixedly connected to the plunger 4, and a compression spring 6 is connected between the mover push rod 7 and the plunger 4.

[0033] Further, in this embodiment, the top of the pump barrel 5 is connected to an oil pipe 1.

[0034] Further, in this embodiment, a traveling check valve 3 is provided in the plunger 4, and a fixed check valve 2 is provided in the upper part of the pump barrel 5.

[0035] Further, this embodiment further includes a casing 8, and the pump barrel 5 and the oil pipe 1 are both arranged inside the casing 8.

[0036] Further, in this embodiment, the stator winding 11 is fixed inside the casing 8 through a fixing member 10.

[0037] During operation, when the mover push rod 7 drives the plunger 4 to move upward, the traveling valve 3 closes, and the liquid pressure at the top of the plunger 4 in the pump barrel 5 increases. Under the action of high pressure, the liquid pushes open the fixed valve 2 and enters the tubing 1 from the pump barrel 5. When the plunger 4 moves downward under the action of the mover push rod 7 of the linear motor, the fixed valve 2 closes, and the liquid pressure at the top of the plunger 4 in the pump barrel 5 decreases. Under the action of the pressure difference, the liquid pushes open the traveling valve 3 and enters the pump barrel 5 from outside the tubing 1. In this way, the reciprocating motion is repeated to complete the extraction of the liquid. At the same time, when moving upward, the magnitude of the current passed through the linear motor increases from 0 to the peak value i max1 , and then decreases to 0. The plunger 4 moves to the top of the stroke. The variation of the current magnitude with time conforms to the sine curve variation law. And when i = a < i max1 , the thrust of the mover push rod 7 is equal to the gravity of the plunger 4. Thus, when i < a, the plunger 4 does not move. When i > a, the plunger 4 starts to move upward with an increasing acceleration, and reaches the peak value i max1 . At this time, the acceleration is the largest. Subsequently, the plunger 4 starts to move upward with a decreasing acceleration. When i < a, the plunger 4 starts to decelerate. When i decreases to 0, the speed of the plunger 4 just reduces to 0, and it moves to the top of the stroke. When the mover push rod 7 moves downward, the magnitude of the current passed through the linear motor increases from 0 to the peak value i max2 , and then decreases to a. The plunger 4 moves to the bottom of the stroke. The variation of the current magnitude with time conforms to the sine curve variation law, and a < i max2 < i max1 . When it just starts to move downward and i < a, the plunger 4 moves downward with a decreasing acceleration. When i > a, the plunger 4 moves with an increasing deceleration, and at i = i max2 , the acceleration is the largest. When i decreases to a, the speed of the plunger 4 reduces to 0, and it just moves to the bottom of the stroke. The variation curve of the current passing time of the linear motor is as shown in Figure 3 , and the variation curve of the plunger 4 speed with time is as shown in Figure 4 . Then i starts the next upward process from 0.

[0038] In this embodiment, by controlling the current to vary along a sine curve, it is possible to avoid the sudden increase in the force of the mover push rod 7 during upward movement, which may cause excessive extrusion between the mover push rod 7 and the plunger 4. At the same time, during downward movement, it can also prevent the problem that the plunger 4 and the liquid column generate a large impact on the mover push rod 7 due to inertia. Thus, it is possible to reduce the loss of the mover push rod 7 during the reciprocating process and extend the service life of the linear motor.

[0039] Those skilled in the art should understand that when the mass of the plunger 4 and its stroke height change, the current should change accordingly. For example, if the stroke height of the plunger 4 increases, the required acceleration will increase, and the current needs to increase. The specific current calculation process is well-known to those skilled in the art and will not be elaborated in this embodiment.

[0040] In addition, a compression spring 6 is provided between the mover push rod 7 and the plunger 4 in this embodiment. During normal operation, the effect of the spring 6 is small. When the linear motor fails, the spring 6 can buffer the plunger 4 to prevent it from hitting the mover push rod 7 under the action of inertia.

[0041] Embodiment 2: This embodiment provides a current control method for a reciprocating pump with a simple harmonic motion of the linear motor mover. When the mover push rod 7 drives the plunger 4 to move upward, the magnitude of the current input to the linear motor increases from 0 to the peak value i max1 , and then decreases to 0. When the plunger 4 moves to the top of the stroke, the change of the current magnitude with time conforms to the sine curve change rule, and when i = a < i max1 , the thrust magnitude of the mover push rod 7 is equal to the gravity of the plunger 4; when the mover push rod 7 moves downward, the magnitude of the current input to the linear motor increases from 0 to the peak value i max2 , and then decreases to a. When the plunger 4 moves to the bottom of the stroke, the change of the current magnitude with time conforms to the sine curve change rule, and a < i max2 < i max1 .

[0042] Adaptability changes made according to actual needs are all within the protection scope of the present invention.

[0043] It should be noted that for those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

Claims

1. A current control method for a reciprocating pump with a simple harmonic motion of a linear motor mover, characterized in that, It includes a stator winding, a rotor assembly, a pump barrel and a plunger. The top end of the rotor assembly is fixedly connected to the plunger, and a compression spring is also connected between the two. The plunger is located in the pump barrel. The rotor assembly includes a rotor body and a rotor push rod fixed on the rotor body. The stator winding is sleeved outside the rotor push rod. The rotor push rod is fixedly connected to the plunger, and a compression spring is connected between the rotor push rod and the plunger. The current control method in the reciprocating pump with the linear motor mover performing simple harmonic motion includes that when the mover push rod drives the plunger to move upward, the magnitude of the current applied to the linear motor increases from 0 to the peak value i max1 , and then decreases to 0. When the plunger moves to the top of the stroke, the variation of the current magnitude with time conforms to the sine curve variation law, and when i = a < i max1 , the magnitude of the thrust of the mover push rod is equal to the gravity of the plunger; thus, when i < a, the plunger does not move, and when i > a, the plunger starts to move upward with an increasing acceleration, and when it reaches the peak value i max1 , the acceleration is the largest. Subsequently, the plunger starts to move with a decreasing acceleration. When i < a, the plunger starts to decelerate. When i decreases to 0, the speed of the plunger just reduces to 0 and it moves to the top of the stroke; when the mover push rod moves downward, the magnitude of the current applied to the linear motor increases from 0 to the peak value i max2 , and then decreases to a. When the plunger moves to the bottom of the stroke, the variation of the current magnitude with time conforms to the sine curve variation law, a < i max2 < i max1 ; when it just starts to move downward and i < a, the plunger moves downward with a decreasing acceleration, and when i > a, the plunger moves with an increasing deceleration, and when i = i max2 , the acceleration is the largest. When i decreases to a, the speed of the plunger reduces to 0, and it just moves to the bottom of the stroke.

2. The current control method in the reciprocating pump with the simple harmonic motion of the linear motor mover according to claim 1, characterized in that, The top of the pump barrel is communicated with an oil pipe.

3. The current control method in the reciprocating pump with the simple harmonic motion of the linear motor mover according to claim 2, characterized in that, A traveling valve is arranged in the plunger, and a fixed valve is arranged at the upper part of the pump barrel.

4. The current control method in the reciprocating pump with a linear motor mover performing simple harmonic motion according to claim 3, characterized in that, It also includes a casing, and the pump barrel and the oil pipe are both arranged inside the casing.

5. The method for controlling current in a reciprocating pump with a linear motor mover performing simple harmonic motion according to claim 4, characterized in that, The stator winding is fixed inside the casing through a fixing member.

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