Patent Publication Number: US-2022228469-A1

Title: Low-pressure liquid inlet manifold and fracturing apparatus

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The present application claims the priority of the Chinese patent application No. 202110080048.8 filed on Jan. 21, 2021, the Chinese patent application No. 202110859620.0 filed on Jul. 28, 2021 and the Chinese patent application No. 202121733037.7 filed on Jul. 28, 2021, for all purposes, the disclosure of which is incorporated herein by reference in its entirety as part of the present application. 
     TECHNICAL FIELD 
     Embodiments of the present disclosure relate to a low-pressure liquid inlet manifold and a fracturing apparatus. 
     BACKGROUND 
     In the field of oil and natural gas exploitation, fracturing technology is a method of using high-pressure fracturing fluid to form cracks in oil and gas layers. The fracturing technology improves underground flow environment of oil and gas by making cracks in the oil and gas layers, so that the production of oil wells can be increased, thus the fracturing technology is widely used in exploitation of conventional and unconventional oil and gas, and development of offshore and onshore oil and gas resource. 
     A fracturing apparatus usually includes a plunger pump, a low-pressure liquid inlet manifold and a high-pressure discharge manifold; the low-pressure liquid inlet manifold provides low-pressure fluid to the plunger pump, the plunger pump uses the reciprocating movement of a plunger in a cylinder to pressurize the low-pressure fluid, and the pressurized high-pressure fluid is discharged through the high-pressure discharge manifold, so that the pressurized high-pressure fluid can be used for fracturing of oil and gas layers. 
     SUMMARY 
     Embodiments of the present disclosure provide a low-pressure liquid inlet manifold and a fracturing apparatus, by means of arranging at least one auxiliary accumulator corresponding to at least one of the N liquid feeding pipes on the main liquid inlet pipe, the low-pressure liquid inlet pipe can ensure stability of liquid supply pressure of the corresponding liquid feeding pipe in the case where pressure of the fluid in the main liquid inlet pipe is insufficient or fluctuates, so that the problem of fracturing air suction is avoided, and thus the service life and performance of the plunger pump can be improved. On the other hand, the auxiliary accumulator can play a role of preventing sand deposition to a certain extent. Therefore, the low-pressure liquid inlet manifold can further alleviate or even eliminate the problem of sand deposition. 
     At least one embodiment of the present disclosure provides a low-pressure liquid inlet manifold, which includes: a main liquid inlet pipe, including a first end and a second end that are arranged opposite to each other in an extension direction of the main liquid inlet pipe; N liquid feeding pipes, arranged in sequence along a direction from the first end to the second end; each of the liquid feeding pipes includes a third end and a fourth end that are arranged opposite to each other in an extension direction of the each of the liquid feeding pipes, the third end is communicated with the main liquid inlet pipe, and the fourth end is configured to provide low-pressure liquid to a plunger pump; and the low-pressure liquid inlet manifold further includes at least one auxiliary accumulator, the at least one auxiliary accumulator is connected with the main liquid inlet pipe and is arranged corresponding to at least one of the N liquid feeding pipes, an orthographic projection of the auxiliary accumulator on an axis of the main liquid inlet pipe overlaps with an orthographic projection of a corresponding liquid feeding pipe on the axis, and N is a positive integer greater than or equal to 2. 
     For example, in the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, the low-pressure liquid inlet manifold includes N−1 auxiliary accumulators, and the N−1 auxiliary accumulators are sequentially arranged along the direction from the first end to the second end; and, in the direction from the first end to the second end, a first one of the N liquid feeding pipes is arranged corresponding to a first one of the N−1 auxiliary accumulators, an i-th one of the N liquid feeding pipes is arranged corresponding to an i-th one of the N−1 auxiliary accumulators, an (N−1)-th one of the N liquid feeding pipes is arranged corresponding to an (N−1)-th one of the N−1 auxiliary accumulators, and i is a positive integer greater than 1 and less than N−1. 
     For example, the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure further includes: an end auxiliary accumulator, wherein the end auxiliary accumulator is connected with the main liquid inlet pipe and is arranged corresponding to the N-th one of the N liquid feeding pipes, and an orthographic projection of the end auxiliary accumulator on the axis of the main liquid inlet pipe overlaps with an orthographic projection of the N-th one of the N liquid feeding pipes on the axis. 
     For example, the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure further includes: a deflecting inclined plate, located at the second end and at least partly located in the main liquid inlet pipe, an orthographic projection of the deflecting inclined plate on the axis of the main liquid inlet pipe overlaps with an orthographic projection of the N-th one of the N liquid feeding pipes on the axis, an included angle between the deflecting inclined plate and the axis of the main liquid inlet pipe is less than 90 degrees, and a distance between a part of the deflecting inclined plate close to the first end and the N-th one of the N liquid feeding pipes is greater than a distance between a part of the deflecting inclined plate close to the second end and the N-th one of the N liquid feeding pipes. 
     For example, in the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, the included angle between the deflecting inclined plate and the axis of the main liquid inlet pipe ranges from 30 degrees to 60 degrees. 
     For example, the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure further includes: an inclined plug, located at the second end, the deflecting inclined plate is located on the inclined plug. 
     For example, in the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, energy storage pressures of the N−1 auxiliary accumulators are different from each other. 
     For example, in the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, in the direction from the first end to the second end, the energy storage pressures of the N−1 auxiliary accumulators gradually decrease. 
     For example, in the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, in the direction from the first end to the second end, the energy storage pressures of the N−1 auxiliary accumulators gradually decrease, and an energy storage pressure of the end auxiliary accumulator is less than an energy storage pressure of the (N−1)-th one of the N−1 auxiliary accumulator. 
     For example, in the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, each of the auxiliary accumulators includes: a top plate, wherein the top plate is in contact with fluid in the main liquid inlet pipe and is configured to move along a movement direction; and a pressure applying portion, wherein the pressure applying portion is located on a side of the top plate away from the main liquid inlet pipe, and is configured to apply energy storage pressure to the top plate. 
     For example, in the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, an angle between the movement direction of the top plate and a corresponding extension direction of the liquid feeding pipe is less than 180 degrees. 
     For example, in the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, an angle between the movement direction of the top plate and the corresponding extension direction of the liquid feeding pipe is less than 150 degrees. 
     For example, in the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, a minimum distance between a surface of the top plate of the auxiliary accumulator close to the main liquid inlet pipe and the axis of the main liquid inlet pipe is greater than a radius of the main liquid inlet pipe. 
     For example, in the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, a surface of the top plate of the auxiliary accumulator close to the main liquid inlet pipe is a circular arc surface, and a radius of curvature of the circular arc surface is approximately equal to a radius of curvature of an inner wall of the main liquid inlet pipe. 
     For example, in the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, a surface of the top plate of the auxiliary accumulator close to the main liquid inlet pipe is a flat surface. 
     For example, in the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, the low-pressure liquid inlet manifold includes one auxiliary accumulator, the auxiliary accumulator extends from the second end into the main liquid inlet pipe, and extends toward the first end. 
     For example, in the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, in the direction from the first end to the second end, an orthographic projection of the first one of the N liquid feeding pipes on an axis of the main liquid inlet pipe overlaps with an orthographic projection of the auxiliary accumulator on the axis. 
     For example, in the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, the auxiliary accumulator further includes: a fixed pipe, including a hollow cavity; a pipe plug; and a pipe joint, one end of the fixed pipe is fixedly connected with the main liquid inlet pipe, the pressure applying portion is located in the hollow cavity, and the pipe plug is located on a side of the pressure applying portion away from the top plate, and is connected with the fixed pipe through the pipe joint. 
     For example, in the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, the pressure applying portion is an airbag, the auxiliary accumulator further includes an air intake pipe, the pipe plug includes a through hole, and the air intake pipe is connected to the airbag through the through hole. 
     For example, the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure further includes a pressure gauge, configured to detect a gas pressure in the airbag. 
     For example, the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, further includes: a liquid supply pipe, wherein the liquid supply pipe is communicated with the first end of the main liquid inlet pipe, and is configured to provide low-pressure fluid to the main liquid inlet pipe; and a main accumulator, wherein the main accumulator is connected with the liquid supply pipe. 
     For example, the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure further includes a purging pipe, the purging pipe is located at the second end of the main liquid inlet pipe and is communicated with the main liquid inlet pipe. 
     For example, in the low-pressure liquid inlet manifold provided by an embodiment of the present disclosure, a diameter of the first end of the main liquid inlet pipe is larger than a diameter of the second end of the main liquid inlet pipe, and in the direction from the first end to the second end, lengths of the N liquid feeding pipes gradually decrease. 
     At least one embodiment of the present disclosure further discloses a fracturing apparatus, which includes: a plunger pump, including a power end and a hydraulic end; and the abovementioned low-pressure liquid inlet manifold, the low-pressure liquid inlet manifold is connected with the hydraulic end, and is configured to provide low-pressure fluid to the plunger pump. 
     For example, in the fracturing apparatus provided by an embodiment of the present disclosure, the liquid end includes N cylinders, the N liquid feeding pipes and the N cylinders are arranged in one-to-one correspondence, and each of the liquid feeding pipes is configured to provide low-pressure fluid to a corresponding cylinder. 
     For example, in the fracturing apparatus provided by an embodiment of the present disclosure, value of N is 5, 7, or 9. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to clearly illustrate the technical solution of the embodiments of the present disclosure, the drawings of the embodiments will be briefly described. It is apparent that the described drawings are only related to some embodiments of the present disclosure and thus are not limitative of the present disclosure. 
         FIG. 1  is a schematic structural diagram of a low-pressure liquid inlet manifold provided by an embodiment of the present disclosure; 
         FIG. 2  is a schematic structural diagram of another low-pressure liquid inlet manifold provided by an embodiment of the present disclosure; 
         FIG. 3  is a schematic structural diagram of an inclined plug provided by an embodiment of the present disclosure; 
         FIG. 4  is a schematic structural diagram of still another low-pressure liquid inlet manifold provided by an embodiment of the disclosure; 
         FIG. 5  is a schematic structural diagram of an auxiliary accumulator provided by an embodiment of the present disclosure; 
         FIG. 6  is a schematic structural diagram of still another low-pressure liquid inlet manifold provided by an embodiment of the present disclosure; 
         FIG. 7  is a schematic structural diagram of still another low-pressure liquid inlet manifold provided by an embodiment of the present disclosure; 
         FIG. 8  is a schematic structural diagram of still another low-pressure liquid inlet manifold provided by an embodiment of the present disclosure; and 
         FIG. 9  is a schematic diagram of a fracturing apparatus provided by an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In order to make objects, technical details and advantages of embodiments of the present disclosure clear, the technical solutions of the embodiments will be described in a clearly and fully understandable way in connection with the related drawings. It is apparent that the described embodiments are just a part but not all of the embodiments of the present disclosure. Based on the described embodiments herein, those skilled in the art can obtain, without any inventive work, other embodiment(s) which should be within the scope of the present disclosure. 
     Unless otherwise defined, all the technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. The terms “first,” “second,” etc., which are used in the description and claims of the present disclosure, are not intended to indicate any sequence, amount or importance, but distinguish various components. The terms “comprises,” “comprising,” “includes,” “including,” etc., are intended to specify that the elements or the objects stated before these terms encompass the elements or the objects listed after these terms as well as equivalents thereof, but do not exclude other elements or objects. The phrases “connect”, “connected”, etc., are not intended to define a physical connection or a mechanical connection, but may comprise an electrical connection which is direct or indirect. 
     With the continuous development of technology, fracturing operations have put forward higher requirements on the flow and pressure of fracturing; in order to reduce equipment investment costs, use costs and maintenance costs, the oil and gas service companies reduce the number of fracturing trucks in a fracturing truck group, and increase the displacement and discharge pressure of a single fracturing truck, the oil and gas service companies have put forward higher requirements on the performance, service life and performance of the single fracturing truck. 
     The inventor(s) of the present disclosure noted that, for a single fracturing truck, the plunger pump faces the problems of fracturing air suction and sand deposition of the low-pressure liquid inlet manifold under the high-pressure and large displacement working conditions; the problem of fracturing air suction will reduce the service life of a hydraulic end of the plunger pump, while the problem of sand deposition of the low-pressure liquid inlet manifold will reduce the maintenance efficiency and increase maintenance costs. It should be noted, in the case where pressure of low-pressure fluid provided by the low-pressure liquid inlet manifold for the plunger pump is insufficient or fluctuates, the plunger pump may suck air, which leads to the problem of fracturing air suction. 
     In this regard, embodiments of the present disclosure provide a low-pressure liquid inlet manifold and a fracturing apparatus, the low-pressure liquid inlet manifold includes a main liquid inlet pipe and N liquid feeding pipes; the main liquid inlet pipe includes a first end and a second end that are arranged opposite to each other in an extension direction of the main liquid inlet pipe; the N liquid feeding pipes are arranged in sequence along a direction from the first end to the second end; each of the liquid feeding pipes includes a third end and a fourth end that are arranged opposite to each other in an extension direction of the each of the liquid feeding pipes, the third end is communicated with the main liquid inlet pipe, the fourth end is configured to provide low-pressure liquid to a plunger pump; the low-pressure liquid inlet manifold further includes at least one auxiliary accumulator, the at least one auxiliary accumulator is connected with the main liquid inlet pipe, and is arranged corresponding to at least one of the N liquid feeding pipes, an orthographic projection of the auxiliary accumulator on an axis of the main liquid inlet pipe overlaps with an orthographic projection of a corresponding liquid feeding pipe on the axis, N is a positive integer greater than or equal to 2. In this way, the low-pressure liquid inlet pipe is provided with at least one auxiliary accumulator corresponding to at least one of the N liquid feeding pipes on the main liquid inlet pipe, which can ensure stability of liquid supply pressure of the corresponding liquid feeding pipe in the case where pressure of the fluid in the main liquid inlet pipe is insufficient or fluctuates, so that the problem of fracturing air suction is avoided, and thus the service life and performance of the plunger pump can be improved. On the other hand, the auxiliary accumulator can play a role of preventing sand deposition to a certain extent. Therefore, the low-pressure liquid inlet manifold can further alleviate or even eliminate the problem of sand deposition. 
     Hereinafter, the low-pressure liquid inlet manifold and the fracturing apparatus provided by the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. 
     An embodiment of the present disclosure provides a low-pressure liquid inlet manifold.  FIG. 1  is a schematic structural diagram of a low-pressure liquid inlet manifold provided by an embodiment of the present disclosure. As illustrated by  FIG. 1 , the low-pressure liquid inlet manifold  100  includes a main liquid inlet pipe  110  and N liquid feeding pipes  120 ; the main liquid inlet pipe  110  includes a first end  110 A and a second end  110 B that are arranged opposite to each other in an extension direction of the main liquid inlet pipe  110 ; the N liquid feeding pipes  120  are arranged in sequence along a direction from the first end  110 A to the second end  110 B; each of the liquid feeding pipes  120  includes a third end  120 A and a fourth end  120 B that are arranged opposite to each other in an extension direction of the each of the liquid feeding pipes  120 , the third end  120 A is communicated with the main liquid inlet pipe  110 , the fourth end  120 B is configured to provide low-pressure liquid to the plunger pump  200 ; the low-pressure liquid inlet manifold  100  further includes at least one auxiliary accumulator  130 , the at least one auxiliary accumulator  130  is connected with the main liquid inlet pipe  110 , and is arranged corresponding to at least one of the N liquid feeding pipes  120 , and an orthographic projection of the auxiliary accumulator  130  on the axis of the main liquid inlet pipe  110  overlaps with an orthographic projection of a corresponding liquid feeding pipe  120  on the axis, in which N is a positive integer greater than or equal to 2. That is, in the case where the main liquid inlet pipe  110  is divided into multiple sections in the axial direction of the main liquid inlet pipe  110 , and the auxiliary accumulator  130  and the corresponding liquid feeding pipe  120  are located in the same section or adjacent sections of the main liquid inlet pipe  110 , so that the auxiliary accumulator  130  can correspondingly supplement fluid to the corresponding liquid feeding pipe  120 . 
     In the low-pressure liquid inlet manifold provided by the embodiment of the present disclosure, the at least one auxiliary accumulator corresponding to at least one of the N liquid feeding pipes is arranged on the main liquid inlet pipe; in the case where the pressure of the fluid in the main liquid inlet pipe is insufficient or fluctuates, the auxiliary accumulator can ensure the stability of the liquid supply pressure of the corresponding liquid feeding pipe, so that the problem of fracturing air suction is avoided, and thus the service life and the performance of the plunger pump can be improved. On the other hand, in the case where the above mentioned auxiliary accumulator supplements the liquid supply pressure, compression and expansion actions of the auxiliary accumulator can play a role of preventing sand deposition; in addition, the auxiliary accumulator can ensure the stability of the pressure in the main liquid inlet pipe, so that the fluid in the main liquid inlet pipe can flow fully, and the auxiliary accumulator can also play a role of preventing sand deposition to a certain extent. Therefore, the low-pressure liquid inlet manifold can also alleviate or even eliminate the problem of sand deposition. 
     In some examples, as illustrated by  FIG. 1 , the low-pressure liquid inlet manifold  100  includes N−1 auxiliary accumulators  130 , which are sequentially arranged along the direction from the first end  110 A to the second end  110 B; and the N liquid feeding pipes  120  are also sequentially arranged along the direction from the first end  110 A to the second end  110 B. In this case, in the direction from the first end  110 A to the second end  110 B, the first one of the N liquid feeding pipes  120  is arranged corresponding to the first one of the N−1 auxiliary accumulators  130 , the i-th one of the N liquid feeding pipes  120  is arranged corresponding to the i-th one of the N−1 auxiliary accumulators  130 , the (N−1)-th one of the N liquid feeding pipes  120  is arranged corresponding to the (N−1)-th one of the N−1 auxiliary accumulator  130 , in which i is a positive integer greater than 1 and less than N−1. That is, the first one of the N liquid feeding pipes  120  to the (N−1)-th one of the N liquid feeding pipes  120  are arranged in one-to-one correspondence with the N−1 auxiliary accumulators  130 . In this way, in the case where pressure of fluid in the main liquid inlet pipe is insufficient or fluctuates, the N−1 auxiliary accumulators can respectively supplement the fluid for the first one of the N liquid feeding pipes to the (N−1)-th one of the N liquid feeding pipes, to ensure the stability of the liquid supply pressure of the liquid feeding pipes, so that the problem of fracturing air suction can be better avoided. On the other hand, since the N−1 auxiliary accumulators are arranged in sequence from the first end to the second end, and are arranged corresponding to the first one of the N liquid feeding pipes to the (N−1)-th one of the N liquid feeding pipes, so that the problem of sand deposition can be reduced to a great extent. 
     In some examples, as illustrated by  FIG. 1 , the low-pressure liquid inlet manifold  100  further includes: an end auxiliary accumulator  139 , which is connected with the main liquid inlet pipe  110 , and is arranged corresponding to the N-th one of the N liquid feeding pipes  120 , and an orthographic projection of the end auxiliary accumulator  139  on the axis of the main liquid inlet pipe  110  overlaps with an orthographic projection of the N-th one of the N liquid feeding pipes  120  on the axis. In this way, in the case where the pressure of the fluid in the main liquid inlet pipe is insufficient or fluctuates, the end auxiliary accumulator can correspondingly replenish fluid for the N-th one of the liquid feeding pipes. 
     In some examples, the above mentioned end auxiliary accumulator  139  and the auxiliary accumulator  130  may adopt the same structure; in this case, the end auxiliary accumulator  139  can be regarded as an auxiliary accumulator  130 . In this case, the low-pressure liquid inlet manifold  100  includes N auxiliary accumulators  130 , which are arranged in sequence from the first end  110 A to the second end  110 B; in the direction from the first end  110 A to the second end  110 B, the N auxiliary accumulators  130  and the N liquid feeding pipes  120  are arranged in one-to-one correspondence. Of course, the embodiments of the present disclosure include but are not limited thereto, and the end auxiliary accumulator  139  and the auxiliary accumulator  130  may also adopt different structures. 
     In some examples, as illustrated by  FIG. 1 , the storage pressures of the N−1 auxiliary accumulators  130  are different from each other. In the direction from the first end  110 A to the second end  110 B, as a distance between the liquid feeding pipe and the first end  110 A increases, the liquid supply pressure of the liquid feeding pipes will also change accordingly. Therefore, by arranging N−1 auxiliary accumulators  130  to have different storage pressures, the low-pressure liquid inlet manifold can better ensure the liquid supply pressure of the liquid feeding pipe. 
     It should be noted that, the energy storage pressure of the N−1 auxiliary accumulators can be adjusted and arranged by detecting the actual liquid supply pressure (the actual effect played by the auxiliary accumulators) of the N liquid feeding pipes in the case where the pressure of the fluid in the main liquid inlet pipe is insufficient or fluctuates. 
     In some examples, as illustrated by  FIG. 1 , in the direction from the first end  110 A to the second end  110 B, the energy storage pressures of the N−1 auxiliary accumulators  130  gradually decrease. In this way, by arranging the energy storage pressures of the N−1 auxiliary accumulators to gradually decrease, the low-pressure liquid inlet manifold can better ensure the liquid supply pressure of the liquid feeding pipes. 
     In some examples, as illustrated by  FIG. 1 , in the case where the low-pressure liquid inlet manifold  100  includes the end auxiliary accumulator  139 , in the direction from the first end  110 A to the second end  110 B, the energy storage pressures of the N−1 auxiliary accumulators  130  gradually decrease, the energy storage pressure of the end auxiliary accumulator  139  is less than the energy storage pressure of the (N−1)-th one of the N−1 auxiliary accumulators  130 . That is, in the direction from the first end  110 A to the second end  110 B, the energy storage pressures of the N−1 auxiliary accumulators  130  and the end auxiliary accumulator  139  gradually decrease. 
     For example, as illustrated by  FIG. 1 , the low-pressure liquid inlet manifold  100  includes the main liquid inlet pipe  110  and five liquid feeding pipes  120 ; the five liquid feeding pipes  120  are sequentially arranged along the direction from the first end  110 A to the second end  110 B; and the five liquid feeding pipes  120  can be respectively connected with five cylinders  2205  of a hydraulic end  220  of the plunger pump  200 . That is, in the direction from the first end  110 A to the second end  110 B, one end of the first liquid feeding pipe  120  is connected with the main liquid inlet pipe  110 , the other end of the first liquid feeding pipe  120  is connected with a first cylinder  2205  of the hydraulic end  220 , one end of the second liquid feeding pipe  120  is connected with the main liquid inlet pipe  110 , the other end of the second liquid feeding pipe  120  is connected with a second cylinder  2205  of the hydraulic end  220 , one end of the third liquid feeding pipe  120  is connected with the main liquid inlet pipe  110 , the other end the third liquid feeding pipe  120  is connected with a third cylinder  2205  of the hydraulic end  220 , one end of the fourth liquid feeding pipe  120  is connected with the main liquid inlet pipe  110 , the other end of the fourth liquid feeding pipe  120  is connected with a fourth cylinder  2205  of the hydraulic end  220 , one end of the fifth liquid feeding pipe  120  is connected with the main liquid inlet pipe  110 , the other end of the fifth liquid feeding pipe  120  is connected with a fifth cylinder  2205  of the hydraulic end  220 . Thus, the five liquid feeding pipes  120  can respectively provide low-pressure fluid to the five cylinders  2205  of the hydraulic end  220 . 
     As illustrated by  FIG. 1 , the low-pressure liquid inlet manifold  110  further includes five auxiliary accumulators  130  (the end auxiliary accumulator  139  is also regarded as an auxiliary accumulator  130 ), and the five auxiliary accumulators  130  are connected with the main liquid inlet pipe  110 , and are arranged in one-to-one correspondence with the five liquid feeding pipes  120  mentioned above, an orthographic projection of each of the auxiliary accumulators  130  on the axis of the main liquid inlet pipe  110  overlaps with an orthographic projection of the corresponding liquid feeding pipe  120  on the axis. In this way, the five auxiliary accumulators  130  can respectively replenish fluid or fluid pressure to the five liquid feeding pipes  120 , to ensure the stability of the liquid supply pressure of the liquid feeding pipes, so that the problem of fracturing air suction can be better avoided. 
     In some examples, as illustrated by  FIG. 1 , the above mentioned auxiliary accumulators  130  are detachably connected with the main liquid inlet pipe  110 . In addition, the above mentioned end auxiliary accumulator  139  is also detachably connected with the main liquid inlet pipe  110 . In this way, in the case where at least one of the auxiliary accumulators or the end auxiliary accumulator is damaged, the low-pressure liquid inlet manifold can be maintained immediately, to ensure a long-term stable operation of an apparatus including the low-pressure liquid inlet manifold. On the other hand, the auxiliary accumulators or the end auxiliary accumulator can also be removed in the case where the above auxiliary accumulators or the end auxiliary accumulator are not needed. Or, in the case where the above mentioned auxiliary accumulators have relatively large volumes, during the transportation of a fracturing apparatus using the above mentioned low-pressure liquid inlet manifold, the auxiliary accumulators can be removed, to facilitate transportation; after the fracturing apparatus using the above mentioned low-pressure liquid inlet manifold is transported to the designated position, the auxiliary accumulators can be installed. 
     In some examples, as illustrated by  FIG. 1 , the low-pressure liquid inlet manifold  100  further includes a liquid supply pipe  160  and a main accumulator  170 ; the liquid supply pipe  160  is communicated with a first end  110 A of the main liquid inlet pipe  110 , and is configured to provide low-pressure fluid to the main liquid inlet pipe  110 ; the main accumulator  170  is connected with the liquid supply pipe  160 . In this case, the first end  110  of the main liquid inlet pipe  110  is a liquid inlet end; the main accumulator  170  can ensure that the pressure of the main liquid inlet pipe  110  is stable in the case where the pressure of the main liquid inlet pipe  110  is insufficient or the pressure fluctuates. It should be noted that if only the above mentioned main accumulator  170  is provided without the auxiliary accumulator  130 , as a distance between the main accumulator  170  and the first end  110 A increases, the main accumulator  170  cannot effectively and adequately replenish fluid or supply pressure for the liquid feeding pipe  120  that is far away from the main accumulator  170 , thus problems such as insufficient liquid supply pressure may still exist. The low-pressure liquid inlet manifold provided in the present example stabilizes the pressure of the low-pressure fluid globally and locally by the combination and coordination of the main accumulator and the auxiliary accumulator, so that an excellent effect is provided. 
       FIG. 2  is a schematic structural diagram of another low-pressure liquid inlet manifold provided by an embodiment of the present disclosure. As illustrated by  FIG. 2 , the low-pressure liquid inlet manifold  100  is not arranged with the above mentioned end auxiliary accumulator  139 , that is, the N-th one of the N liquid feeding pipes  120  does not correspond to the auxiliary accumulator  130  or the end auxiliary accumulator  139 . As illustrated by  FIG. 1 , the low-pressure liquid inlet manifold  100  further includes a deflecting inclined plate  140 , the deflecting inclined plate  140  is located at the second end  110 B, and is at least partially located in the main liquid inlet pipe  110 . An orthographic projection of the deflecting inclined plate  140  on the axis of the main liquid inlet pipe  110  overlaps with an orthographic projection of the N-th one of the N liquid feeding pipes  120  on the axis, and an included angle between the deflecting inclined plate  140  and the axis of the main liquid inlet pipe  110  is less than 90 degrees. A distance between a part of the deflecting inclined plate  140  close to the first end  110 A and the N-th one of the N liquid feeding pipes  120  is greater than a distance between a part of the deflecting inclined plate  140  close to the second end  110 B and the N-th one of the N liquid feeding pipes  120 . In this way, the deflecting inclined plate  140  can guide fluid in the main liquid inlet pipe  110  to the N-th one of the N liquid feeding pipes  120 , so that an effect of ensuring the liquid supply pressure of the N-th one of the N liquid feeding pipes  120  can be achieved. In addition, compared with the case where the N-th one of the N liquid feeding pipes  120  is also arranged with the auxiliary accumulator  130  or the end auxiliary accumulator  139 , because the deflecting inclined plate  140  has the advantages of simple structure, simple maintenance, and low cost, the low-pressure liquid inlet manifold can improve the service life and performance of the plunger pump by the combination of the auxiliary accumulator  130  and the deflecting inclined plate  140 , and alleviate or even eliminate the problem of sand deposition, at the same time, the low-pressure liquid inlet manifold has lower maintenance difficulty and lower costs. 
     In some examples, as illustrated by  FIG. 2 , the included angle between the deflecting inclined plate  140  and the axis of the main liquid inlet pipe  110  is in the range of from 30 degrees to 60 degrees. In this way, the deflecting inclined plate  140  has a better guiding effect, and can better ensure the liquid supply pressure of the N-th one of the N liquid feeding pipes. Of course, the embodiments of the present disclosure include but are not limited thereto, the included angle between the deflecting inclined plate and the axis of the main liquid inlet pipe can be arranged according to actual conditions. 
     In some examples, as illustrated by  FIG. 2 , the N−1 auxiliary accumulators  130  have different storage pressures. In the direction from the first end  110 A to the second end  110 B, as the distance between the liquid feeding pipe and the first end  110 A increases, the liquid supply pressures of the liquid feeding pipes will also change accordingly. Therefore, by arranging N−1 auxiliary accumulators  130  to have different energy storage pressures, the low-pressure liquid inlet manifold can better ensure the liquid supply pressures of the liquid feeding pipes. 
     It should be noted that, the energy storage pressures of the N−1 auxiliary accumulators can be adjusted and arranged by detecting actual supply pressures (that is, actual effect of the auxiliary accumulators) of the N liquid feeding pipes in the case where the pressure of the fluid in the main liquid inlet pipe is insufficient or fluctuating. 
     In some examples, as illustrated by  FIG. 2 , in the direction from the first end  110 A to the second end  110 B, the energy storage pressures of the N−1 auxiliary accumulators  130  gradually decrease. In this way, by arranging the energy storage pressures of the N−1 auxiliary accumulators to gradually decrease, the low-pressure liquid inlet manifold can better ensure the liquid supply pressure of the liquid feeding pipes. 
     In some examples, as illustrated by  FIG. 2 , the low-pressure liquid inlet manifold  100  further includes an inclined plug  150 , and the inclined plug  150  is located at the second end  110 B and is used to block the second end  110 B. In this case, the deflecting inclined plate  140  is located on the inclined plug  150 . Therefore, the low-pressure liquid inlet manifold can reduce the difficulty of installation and maintenance of the deflecting inclined plate by arranging the deflecting inclined plate on the inclined plug. 
     For example, as illustrated by  FIG. 2 , the low-pressure liquid inlet manifold  100  includes the main liquid inlet pipe  110  and five liquid feeding pipes  120 ; the five liquid feeding pipes  120  are sequentially arranged along the direction from the first end  110 A to the second end  110 B; and the five liquid feeding pipes  120  can be respectively connected with five cylinders  2205  of the hydraulic end  220  of the plunger pump  200 . That is, in the direction from the first end  110 A to the second end  110 B, one end of the first liquid feeding pipe  120  is connected with the main liquid inlet pipe  110 , the other end of the first liquid feeding pipe  120  is connected with the first cylinder  2205  of the hydraulic end  220 , one end of the second liquid feeding pipe  120  is connected with the main liquid inlet pipe  110 , the other end of the second liquid feeding pipe  120  is connected with the second cylinder  2205  of the hydraulic end  220 , one end of the third liquid feeding pipe  120  is connected with the main liquid inlet pipe  110 , and the other end of the third liquid feeding pipe  120  is connected with the third cylinder  2205  of the hydraulic end  220 , one end of the fourth liquid feeding pipe  120  is connected with the main liquid inlet pipe  110 , and the other end of the fourth liquid feeding pipe  120  is connected with the fourth cylinder  2205  of the hydraulic end  220 , one end of the fifth liquid feeding pipe  120  is connected with the main liquid inlet pipe  110 , and the other end of the fifth liquid feeding pipe  120  is connected with the fifth cylinder  2205  of the hydraulic end  220 . In this way, the five liquid feeding pipes  120  can respectively provide low-pressure fluid to the five cylinders  2205  of the hydraulic end  220 . 
     As illustrated by  FIG. 2 , the low-pressure liquid inlet manifold  110  further includes four auxiliary accumulators  130 , and the four auxiliary accumulators  130  are respectively connected with the main liquid inlet pipe  110 ; in the direction from the first end  110 A to the second end  110 B, the four auxiliary accumulators  130  are arranged in one-to-one correspondence with the front four liquid feeding pipes  120 , an orthographic projection of each of the four auxiliary accumulators  130  on the axis of the main liquid inlet pipe  110  overlaps with an orthographic projection of the corresponding liquid feeding pipe  120  on the axis. In this way, the four auxiliary accumulators  130  can respectively supplement fluid or fluid pressure to the four liquid feeding pipes  120 , and the liquid supply pressure of the fifth liquid feeding pipe  120  can be ensured by the deflecting inclined plate  140 . In this way, the low-pressure liquid inlet manifold can improve the service life and performance of the plunger pump through the combination of the four auxiliary accumulators  130  and the deflecting inclined plate  140 , and alleviates or even eliminates the problem of sand deposition, and at the same time, the low-pressure liquid inlet manifold has lower maintenance difficulty and lower cost. 
     It should be noted that, although the low-pressure liquid inlet manifold shown in  FIGS. 1 and 2  both adopt a scheme of one auxiliary accumulator corresponding to one liquid feeding pipe, the embodiments of the present disclosure include but are not limited thereto. In the case where the performance of the auxiliary accumulator is good, one auxiliary accumulator can also correspond to multiple liquid feeding pipes, which is used to replenish fluid for multiple liquid feeding pipes or to ensure the stability of liquid supply pressure. In addition, although five liquid feeding pipes are provided shown in  FIG. 1  and  FIG. 2 , the embodiments of the present disclosure include but are not limited thereto. 
       FIG. 3  is a schematic structural diagram of an inclined plug provided by an embodiment of the present disclosure. As illustrated by  FIG. 3 , the inclined plug  150  includes a straight pipe  151  and an inclined pipe  152  located inside the straight pipe  151 , and the deflecting inclined plate  140  is arranged on the inclined pipe  152 , in this case, a plane shape of the deflecting inclined plate  140  may be an ellipse, that is, a shape of an inclined section of the inclined pipe  152 , so that better diversion can be performed. 
     In some examples, as illustrated by  FIG. 3 , the inclined plug  150  further includes a plug  153  at one end of the straight pipe  151 . A handle  1530  can be arranged on the plug  153  to facilitate disassembly and assembly. 
       FIG. 4  is a schematic structural diagram of an auxiliary accumulator provided by an embodiment of the present disclosure. As illustrated by  FIG. 4 , the auxiliary accumulator  130  includes a top plate  131  and a pressure applying portion  132 ; the top plate  131  is in contact with the fluid in the main liquid inlet pipe  110  and can move along a movement direction; the pressure applying portion  132  is located on a side of the top plate  131  away from the main liquid inlet pipe  110  and is configured to apply energy storage pressure to the top plate  131 . In this way, in the case where the fluid pressure in the main liquid inlet pipe  110  is high, the top plate  131  can be pushed to move away from the main liquid inlet pipe  110 , so that the fluid pressure in the main liquid inlet pipe  110  is reduced; in the case where the fluid pressure in the main liquid inlet pipe  110  is insufficient, the pressure applying portion  132  can push the top plate  131  to move to a center of the main liquid inlet pipe  110 , to replenish fluid to the corresponding liquid feeding pipe  120 , so that the supply pressure of the corresponding liquid feeding pipe  120  is ensured. 
     In some examples, as illustrated by  FIG. 4 , the auxiliary accumulator  130  further includes a fixed pipe  133 , a pipe plug  134  and a pipe joint  135 ; the fixed pipe  133  includes a hollow cavity  1330 ; one end of the fixed pipe  133  is fixedly connected with the main liquid inlet pipe  110 , the pressure applying portion  132  is located in the hollow cavity  1330 , the pipe plug  134  is located on a side of the pressure applying portion  132  away from the top plate  131 , and is connected with the fixed pipe  133  through the pipe joint  135 . 
     In some examples, as illustrated by  FIG. 4 , the pressure applying portion  132  is an airbag, gas in the airbag can be nitrogen; the auxiliary accumulator  130  further includes an air inlet pipe  136 , the pipe plug  134  includes a through hole  1340 , the air inlet pipe  136  is connected with the airbag  132  through the through hole  1340 , so that the airbag can be inflated or deflated through the air inlet pipe  136 , to adjust the pressure generated by the airbag  132 . 
     In some examples, as illustrated by  FIG. 4 , the auxiliary accumulator  130  further includes a buffer layer  137 , which is located between the pressure applying portion  132  and the pipe plug  134 , so as to protect the airbag. 
     In some examples, as illustrated by  FIG. 4 , the auxiliary accumulator  130  further includes a pressure gauge  138 , which is configured to detect the gas pressure in the airbag  132 . 
     In some examples, as illustrated by  FIG. 4 , a surface of the top plate  131  of the auxiliary accumulator  130  close to the main liquid inlet pipe  110  is a circular arc surface, and a radius of curvature of the circular arc surface is approximately equal to a radius of curvature of an inner wall of the main liquid inlet pipe, so that the influence of the arrangement of the auxiliary accumulator on the fluid in the main liquid inlet pipe can be reduced. 
     Of course, regarding the shape of the surface of the top plate of the auxiliary accumulator close to the main liquid inlet pipe, the embodiments of the present disclosure include, but are not limited to the circular arc surface.  FIG. 5  is a schematic structural diagram of another auxiliary accumulator provided by an embodiment of the present disclosure. As illustrated by  FIG. 5 , the surface of the top plate  131  of the auxiliary accumulator  130  close to the main liquid inlet pipe  110  further includes a flat surface. 
     It should be noted that, in the case where the above mentioned end accumulator and the auxiliary accumulators adopt a same structure, the structure of the end accumulator can also refer to the related descriptions of  FIG. 4 . 
     In some examples, as illustrated by  FIGS. 1 and 2 , a minimum distance between the surface of the top plate  131  of the auxiliary accumulator  130  close to the main liquid inlet pipe and the axis of the main liquid inlet pipe  110  is greater than the radius of the main liquid inlet pipe  110 . That is, a part of the auxiliary accumulator  130  located inside the main liquid inlet pipe  110  cannot exceed an inner surface of the main liquid inlet pipe  110 . In this way, the top plate  131  of the auxiliary accumulator  130  will not extend into the main liquid inlet pipe  110 , to avoid obstructions to the flow of fluid. 
     In some examples, as illustrated by  FIGS. 1 and 2 , in a direction of gravity, the liquid feeding pipe  120  is arranged at a top of the main liquid inlet pipe  110 , and the auxiliary accumulator  130  is arranged at a bottom of the main liquid inlet pipe  110 ; in this case, an included angle between the movement direction of the top plate  131  and the extension direction of the corresponding liquid feeding pipe  120  is approximately 180 degrees. 
       FIG. 6  is a schematic structural diagram of still another low-pressure liquid inlet manifold provided by an embodiment of the present disclosure. As illustrated by  FIG. 6 , an angle between the movement direction of the top plate  131  and the extension direction of the corresponding liquid feeding pipe  120  is less than 180 degrees. That is, the auxiliary accumulator  130  is not arranged at the bottom of the main liquid inlet pipe  110 , but on the side surface of the main liquid inlet pipe  110 , so that erosion and wear of the gravel to the auxiliary accumulator can be reduced. 
     In some examples, as illustrated by  FIG. 6 , the included angle between the movement direction of the top plate and the extension direction of the corresponding liquid feeding pipe is less than 150 degrees; for another example, the included angle between the movement direction of the top plate and the extension direction of the corresponding liquid feeding pipe is less than 90 degrees. 
       FIG. 7  is a schematic structural diagram of still another low-pressure liquid inlet manifold provided by an embodiment of the present disclosure. As illustrated by  FIG. 7 , the low-pressure liquid inlet manifold  100  further includes a liquid supply pipe  160  and a main accumulator  170 ; the liquid supply pipe  160  is communicated with the first end  110 A of the main liquid inlet pipe  110 , and is configured to provide low-pressure fluid to the main liquid inlet pipe  110 ; the main accumulator  170  is connected with the liquid supply pipe  160 . In this case, the first end  110  of the main liquid inlet pipe  110  is a liquid inlet end; the main accumulator  170  can ensure that the pressure of the main liquid inlet pipe  110  is stable in the case where the pressure of the main liquid inlet pipe  110  is insufficient or the pressure fluctuates. It should be noted that, although the low-pressure liquid inlet manifold shown in  FIG. 6  does not show the auxiliary accumulator, the low-pressure liquid inlet manifold can also be arranged with the above mentioned auxiliary accumulators and the end auxiliary accumulator. 
     In some examples, as illustrated by  FIG. 7 , the low-pressure liquid inlet manifold  100  further includes a purging pipe  180 , the purging pipe  180  is located at the second end  110 B of the main liquid inlet pipe  110  and is communicated with the main liquid inlet pipe  110 . In this way, in the case where the low-pressure liquid inlet manifold is out of service or there is gravel in the low-pressure liquid inlet manifold, purge gas can be introduced into the purging pipe  180 , to blow out the gravel or residual moisture in the low-pressure liquid inlet manifold. 
     In some examples, as illustrated by  FIG. 7 , a diameter of the first end  110 A of the main liquid inlet pipe  110  is larger than a diameter of the second end  110 B of the main liquid inlet pipe  110 , in the direction from the first end  110 A to the second end  110 B, lengths of the N liquid feeding pipes gradually decrease. As the fluid in the main liquid inlet pipe continuously enters the plunger pump from the liquid feeding pipes, a flow rate of the main liquid inlet pipe gradually decreases. The main liquid inlet pipe in the low-pressure liquid inlet manifold provided in the example is a reducing pipe, so that it can ensure that flow and pressure of a connection position of each of the liquid feeding pipes and the curved liquid feeding pipes and the main liquid inlet pipe are stable, to reduce a generation of cavitation, and thus it can avoid the problem of fracturing air suction and restrain the generation of vibration. On the other hand, as the lengths of the liquid feeding pipes gradually decrease from the first end of the main liquid inlet pipe to the second end of the main liquid inlet pipe, the main liquid inlet pipe has an upwardly inclined angle with respect to the horizontal direction, so that the settlement caused by horizontal transportation can be reduced. 
       FIG. 8  is a schematic structural diagram of still another low-pressure liquid inlet manifold provided by an embodiment of the present disclosure. As illustrated by  FIG. 8 , the low-pressure liquid inlet manifold  100  includes an auxiliary accumulator  130 , and the auxiliary accumulator  130  extends from the second end  110 B into the low-pressure liquid inlet manifold  110 , and extends to the first end  110 A. 
     In some examples, as illustrated by  FIG. 8 , in the direction from the first end  110 A to the second end  110 B, an orthographic projection of the first one of the N liquid feeding pipes  120  on the axis of the main liquid inlet pipe  110  overlaps with an orthographic projection of the auxiliary accumulator  130  on the axis. In this way, in the working process, after the fluid enters the main liquid inlet pipe, the fluid will contact the auxiliary accumulator, so that the auxiliary accumulator buffers the fluid in the entire liquid inlet main pipe. 
     In some examples, as illustrated by  FIG. 8 , an end of the auxiliary accumulator  130  away from the second end  110 B includes an inclined surface, so that the fluid can be better buffered, to avoid obstructions to the flow of fluid. 
     An embodiment of the present disclosure further provides a fracturing apparatus.  FIG. 9  is a schematic diagram of a fracturing apparatus provided by an embodiment of the present disclosure. As illustrated by  FIG. 9 , the fracturing apparatus  500  includes a plunger pump  200  and the above mentioned low-pressure liquid inlet manifold  100 ; the plunger pump  200  includes a power end  210  and a hydraulic end  220 ; and the low-pressure liquid inlet manifold  100  is connected with the hydraulic end  220  and is configured to provide low-pressure fluid to the plunger pump  200 . In this way, the at least one auxiliary accumulator corresponding to at least one of the N liquid feeding pipes is arranged on the main liquid inlet pipe; in the case where the pressure of the fluid in the main liquid inlet pipe is insufficient or fluctuates, the auxiliary accumulator can ensure the stability of the liquid supply pressure of the corresponding liquid feeding pipe, so that the problem of fracturing air suction can be avoided, and thus the service life and performance of the plunger pump can be improved. On the other hand, in the case where the above mentioned auxiliary accumulator supplements the liquid supply pressure, compression and expansion actions of the auxiliary accumulator can play a role of preventing sand deposition; in addition, the auxiliary accumulator can ensure that the pressure in the main liquid inlet pipe is stable, so that the fluid in the main liquid inlet pipe can flow fully, and the auxiliary accumulator can also play a role of preventing sand deposition to a certain extent. Therefore, the low-pressure liquid inlet manifold can also alleviate or even eliminate the problem of sand deposition. 
     For example, a shell of the power end and a shell of the hydraulic end can be fixedly connected by bolts, etc. Of course, the embodiments of the present disclosure include but are not limited thereto, and other connection methods may also be adopted to realize the fixed connection of the above mentioned components. 
     For example, the power end includes a crankshaft connecting rod mechanism and a plunger, the crankshaft connecting rod mechanism can convert a rotary motion into a reciprocating motion of the plunger, at least a part of the plunger can extend into the hydraulic end, to pressurize the low-pressure fluid in the hydraulic end. It should be noted that, the structure and working mode of the plunger pump are briefly described above, however, the plunger pump of the embodiment of the present disclosure includes but is not limited to the above mentioned structure and working mode. 
     In some examples, as illustrated by  FIG. 8 , the hydraulic end  220  includes N cylinders  2205 , N liquid feeding pipes  120  and N cylinders  2205  are arranged in one-to-one correspondence, and each of the liquid feeding pipes  120  is configured to provide low-pressure fluid to the corresponding cylinder  2205 . 
     For example, the value of N is 5, 7, or 9. That is, the plunger pump  200  may be a five-cylinder plunger pump, a seven-cylinder plunger pump, and a nine-cylinder plunger pump. Of course, the embodiments of the present disclosure include but are not limited thereto, and the plunger pump may also be a plunger pump with other cylinder numbers. 
     In some examples, as illustrated by  FIG. 9 , the fracturing apparatus  500  further includes a high-pressure discharge manifold  300 , a gear box  410 , a coupling  410 , and a prime mover  430 . The prime mover  430  is connected with the gear box  410  through the coupling  410 , and the gear box  410  is connected with the power end  210  of the plunger pump  200 , in this way, after power output by the prime mover  430  is decelerated by the gear box  410 , the power is transmitted to the power end  210  of the plunger pump  200 . The power end  210  of the plunger pump  200  converts the power provided by the prime mover  430  into the reciprocating motion of the plunger; the low-pressure liquid inlet manifold  100  is connected with the hydraulic end  220  of the plunger pump  200 , and provides low-pressure fluid, such as fracturing fluid, to the hydraulic end  220 ; the hydraulic end  220  can use the reciprocating movement of the plunger to pressurize the low-pressure fluid to form high-pressure fracturing fluid; the high-pressure discharge manifold  300  is connected with the hydraulic end  220  of the plunger pump  200  and is used to discharge the high-pressure fracturing fluid. In this way, the fracturing apparatus can provide high-pressure fracturing fluid, and then to be used in fracturing operations. 
     For example, the above mentioned prime mover may be an equipment that provides power such as a diesel engine, an electric motor, or a turbine engine. In addition, due to a high speed of the prime mover (especially the electric motor and the turbine engine), a reduction box is necessary to be installed between the plunger pump and the prime mover, so that the reduction box is used to decelerate the power output by the prime mover, to match the plunger pump. 
     In some examples, the fracturing apparatus may be a fracturing truck, a fracturing skid, or other equipment used to generate high-pressure fracturing fluid. 
     The following points required to be explained: 
     (1) the drawings of the embodiments of the present disclosure only relate to the structures related to the embodiments of the present disclosure, and other structures can refer to the general design. 
     (2) without conflict, the embodiments of the present disclosure and the features in the embodiments may be combined with each other. 
     The present application claims the priority of Chinese patent application No. 202110080048.8 filed on Jan. 21, 2021, and the disclosure of which is incorporated herein by reference in its entirety as part of the present application.