Electric submersible pump

Abstract

Invention details;

Description

Submersible electric pump

[0001] The present invention relates to a submersible electric pump, and more particularly to a submersible electric pump with a closed impeller.

[0002] A submersible electric pump having a closed impeller, in which the blades are covered by a main plate and a side plate, as opposed to an open impeller, in which the blades are not covered, is known. Such a submersible electric pump is disclosed, for example, in Japanese Patent Application Laid-Open No. 2006-291937.

[0003] The aforementioned Japanese Patent Application Laid-Open Publication No. 2006-291937 discloses a pump including a motor, a drive shaft, a closed impeller, and a pump casing. In the patent document 1, the suction portion of the closed impeller is configured to communicate with the suction portion of the pump casing. The closed impeller is also attached to the drive shaft.

[0004] Japanese Patent Application Laid-Open No. 2006-291937

[0005] Although not disclosed in the above-mentioned JP 2006-291937 A, a seal is provided on the main shaft on the motor side of the casing to prevent the pumped liquid (e.g., pumped water) inside the casing from leaking toward the motor. Also, the lower end of the closed impeller is located near the suction port in order to minimize the amount of pumped liquid that flows sideways through the gap between the suction port and the closed impeller and prevent a decrease in the efficiency of the submersible electric pump.

[0006] Although not disclosed in the above-mentioned JP 2006-291937 A, studies have been conducted to improve the performance of submersible electric pumps by increasing the flow rate. When increasing the depth of the casing to increase the flow rate, increasing the distance between the closed impeller and the casing's suction port increases the amount of pumped liquid flowing sideways through the gap between the suction port and the closed impeller. Therefore, it is possible to also increase the blade width, which is the height of the closed impeller's main shaft. However, increasing the blade width lowers the center of gravity of the closed impeller, and the radial force acting on the center of gravity of the closed impeller due to the large amount of pumped liquid increases, which may cause the closed impeller to become eccentric. This results in deflection of the main shaft, which in turn creates a gap in the seal, allowing the pumped liquid to seep into the motor.

[0007] The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to provide an underwater electric pump that is capable of preventing the pumped liquid from entering the motor side and is capable of increasing the flow rate.

[0008] In order to achieve the above object, an underwater electric pump in one aspect of the present invention comprises a casing including a flow path having a spiral shape and an inlet port for sucking pumped liquid into the flow path, a closed impeller including a blade portion, a main plate that holds the blade portion, and a side plate that opens on the inlet side of the casing, and a motor including a main shaft connected to the closed impeller, wherein the casing faces the closed impeller, has a convexly protruding inlet port, and includes an inlet flow path portion formed integrally with the casing.

[0009] In one aspect of the submersible electric pump of the present invention, as described above, the casing faces the closed impeller, has a convexly protruding suction port, and includes a suction passage formed integrally with the casing. This allows the distance between the closed impeller and the suction port to be reduced by adjusting the protruding height of the suction passage, even when the casing depth is increased to increase the flow rate. This allows the flow rate to be increased by reducing the distance between the closed impeller and the suction port and minimizing the amount of pumped liquid flowing laterally through the gap between the suction port and the closed impeller. Furthermore, the width of the blades can be reduced because the distance between the closed impeller and the suction port can be adjusted by adjusting the protruding height of the suction passage. This allows the blade width to be reduced, thereby preventing pumped liquid from infiltrating into the motor due to shaft deflection. As a result, the flow rate can be increased while preventing pumped liquid from infiltrating into the motor.

[0010] In the submersible electric pump according to the above aspect, the blade width, which is the height of the closed impeller including the blade portion, main plate, and side plate in the direction of extension of the main shaft, is preferably smaller than the maximum depth of the flow passage of the casing in the direction of extension of the main shaft by the protruding height of the suction flow passage in the direction of extension of the main shaft. With this configuration, the blade width of the closed impeller can be reduced by the protruding height of the suction flow passage, making it easy to reduce the blade width. As a result, it is possible to prevent the main shaft from bending due to an increase in the blade width, and therefore it is easy to prevent the pumped liquid from entering the motor side.

[0011] In the submersible electric pump according to the above aspect, the suction passage portion preferably has a cylindrical shape extending from the suction port side toward the closed impeller side. With this configuration, the pumped liquid can be sucked through the cylindrical internal passage of the suction passage portion.

[0012] In this case, preferably, the side plate of the closed impeller has an opening that opens to the suction passage portion side, and the inner diameter of the opening is approximately the same as the inner diameter of the end of the suction passage portion on the closed impeller side when viewed from the direction in which the main shaft extends. With this configuration, the diameters of the passages connecting the suction passage portion to the closed impeller can be made approximately the same, so that the closed impeller can efficiently suck in the pumped liquid that has passed through the suction passage portion.

[0013] In the submersible electric pump according to the above aspect, the casing and the suction passage are preferably integrally formed from resin. With this configuration, the casing provided with the suction passage can be easily formed.

[0014] In this case, preferably, the side plate of the closed impeller has an opening that opens to the suction passage portion side, and the opening is disposed with a gap of 5 mm or less between the opening and the suction passage portion in the direction of extension of the main shaft. With this configuration, the amount of pumped liquid that flows sideways through the gap between the opening and the suction passage portion can be minimized, thereby preventing a decrease in the efficiency of the submersible electric pump.

[0015] In the submersible electric pump according to the above aspect, the protruding height of the suction passage in the direction of extension of the main shaft is preferably 20% or more of the maximum depth of the passage in the direction of extension of the main shaft. This configuration makes it possible to produce a submersible electric pump with a sufficiently large flow rate while preventing the blade width of the closed impeller from becoming too large. This effect has been proven by experiments (examples) described below.

[0016] In the submersible electric pump according to the above aspect, the casing preferably includes an outlet for discharging air from within the casing, a sealing member disposed below the outlet and pushed up by the pumped liquid when the pumped liquid is sucked in to seal the outlet, and a base portion on which the sealing member is placed and which forms a flow of the pumped liquid that pushes the sealing member up toward the outlet. With this configuration, by positioning the base portion below and near the center of gravity of the sealing member, the sealing member can be stably pushed up, thereby ensuring that the sealing member is reliably pushed up to the position of the outlet and that the outlet is reliably sealed.

[0017] In this case, the base preferably has a substantially V-shape. With this configuration, the pumped liquid can be collected by the sloped surface forming the V-shape, thereby increasing the force pushing up the sealing member.

[0018] According to the present invention, as described above, it is possible to provide a submersible electric pump that is capable of suppressing the intrusion of pumped liquid into the motor side and is capable of increasing the flow rate.

[0019] 1 is a schematic diagram showing the overall configuration of a submersible electric pump according to an embodiment; FIG. 2 is a perspective view showing a lower casing of a submersible electric pump according to an embodiment; FIG. 3 is a side view of a closed impeller of a submersible electric pump according to an embodiment; FIG. 4 is a view of a closed impeller according to an embodiment from the suction flow path side; FIG. 5 is a view of a casing according to an embodiment from the closed impeller side; FIG. 6 is a view showing the configuration of a discharge section; FIG. 7 is a view showing the position where the discharge section is provided; FIG. 8 is a graph showing the relationship between head and flow rate; FIG. 9 is a graph showing the relationship between shaft power and flow rate; and FIG. 10 is a graph showing the relationship between pump efficiency and flow rate.

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0021] [Embodiment] (Configuration of submersible electric pump) A submersible electric pump 100 of this embodiment will be described with reference to Figures 1 to 7. The submersible electric pump 100 is a vertical submersible electric pump in which the central axis of rotation α of the main shaft 33 extends in the up-down direction (Z direction). The submersible electric pump 100 is placed underwater for use.

[0022] 1, the submersible electric pump 100 includes a pump chamber 1, an oil chamber 2, and a motor 3. Here, the direction in which the rotational center axis α of the main shaft 33 extends is indicated as the Z direction, the direction within the Z direction facing from the closed impeller 4 side to the motor 3 side is indicated as the Z1 direction, and the direction opposite to the Z1 direction is indicated as the Z2 direction.

[0023] The pump chamber 1 is surrounded by a casing 11. The casing 11 includes a lower casing 11a located on the Z2 side and an upper casing 11b located on the Z1 side. The casing 11 is made of resin. The lower casing 11a and the upper casing 11b are formed separately, and the casing 11 is formed by joining the lower casing 11a and the upper casing 11b.

[0024] The casing 11 includes an intake port 12 , an exhaust port 13 , an intake flow passage portion 14 , and a flow passage 15 .

[0025] The suction port 12 is provided on the lower side (Z2 side) of the lower casing 11a. When the closed impeller 4 rotates, the pumped liquid (e.g., pumped water) flows from the suction port 12 in the Z1 direction and into the pump chamber 1.

[0026] The discharge port 13 is provided on the upper side (Z1 side) of the upper casing 11b. The pumped liquid in the pump chamber 1 is discharged from the discharge port 13 by centrifugal force generated by the rotation of the closed impeller 4.

[0027] The suction passage 14 is formed inside the lower casing 11a. The suction passage 14 protrudes in a convex shape in the Z1 direction from the periphery of the suction port 12 toward the closed impeller 4. The suction passage 14 faces the closed impeller 4 in the direction in which the main shaft 33 extends (the Z direction). The suction passage 14 is formed integrally with the lower casing 11a from resin.

[0028] 1 and 2 , the suction passage 14 has a cylindrical shape extending in the Z direction from the suction port 12 side toward the closed impeller 4 side. The protruding height H of the suction passage 14 in the direction in which the main shaft 33 extends (Z direction) is 15% or more, preferably 20% or more, and more preferably 25% or more of the maximum depth D of the passage 15 in the direction in which the main shaft 33 extends. The protruding height H is the height from the inner bottom surface of the casing 11.

[0029] As shown in Figures 1 and 2, the flow path 15 is formed inside the lower casing 11a. The flow path 15 has a spiral shape (volute shape) when viewed in the Z direction. The flow path 15 is formed so that its width increases from the suction port 12 toward the discharge port 13. The maximum depth D of the flow path 15 in the direction in which the main shaft 33 extends (Z direction) is greater than the blade width W, which is the size of the closed impeller 4 including the blade portion 41, main plate 42, and side plate 43 in the direction in which the main shaft 33 extends, by the protruding height H of the suction flow path portion 14 in the direction in which the main shaft 33 extends. The suction port 12 and the flow path 15 are in communication with each other via the suction flow path portion 14.

[0030] 1 and 3 , the closed impeller 4 includes a blade portion 41, a main plate 42, and a side plate 43. The closed impeller 4 is disposed within the flow passage 15. A blade width W, which is the height of the closed impeller 4 including the blade portion 41, the main plate 42, and the side plate 43 in the direction in which the main shaft 33 extends (Z direction), is smaller than the maximum depth D of the flow passage 15 of the casing 11 in the direction in which the main shaft 33 extends (Z direction) by the protruding height H of the suction flow passage portion 14 in the direction in which the main shaft extends (Z direction). The blade width W of the closed impeller 4 is 80% or less, preferably 75% or less, of the maximum depth D of the flow passage 15.

[0031] The blade portion 41 is attached to the Z2 side end of the main shaft 33. The blade portion 41 rotates to agitate the pumped liquid and generate centrifugal force.

[0032] The main plate 42 covers the motor 3 side of the blade portion 41. The main plate 42 holds the blade portion 41. The main plate 42 has a disk shape.

[0033] The side plate 43 is provided on the suction port 12 side of the casing 11. The main plate 42 and the side plate 43 are arranged side by side in the Z direction with the blade portion 41 sandwiched between them. The side plate 43 has an opening 43a that opens to the suction flow path portion 14 side. The side plate 43 has a circular plate shape.

[0034] As shown in Figures 4 and 5, the inner diameter r1 of the opening 43a as viewed from the suction passage 14 side and the inner diameter r2 of the end of the suction passage 14 on the closed impeller 4 side (Z1 side) are configured to be approximately the same size.

[0035] 1 , the opening 43a and the suction passage 14 are disposed at a distance G in the extension direction of the main shaft 33. The distance G is set depending on the location where the submersible electric pump 100 is used. The distance G may be 5 mm or less, preferably greater than 1 mm and equal to or less than 5 mm, and more preferably equal to or less than 3 mm.

[0036] 1 , the motor 3 includes a stator 31, a rotor 32, and a main shaft 33. The motor 3 is located on the Z1 side of the closed impeller 4. The main shaft 33 is connected to the closed impeller 4.

[0037] The oil chamber 2 is provided between the motor 3 and the pump chamber 1. A mechanical seal 21 is provided in the oil chamber 2 to prevent the pumped liquid in the pump chamber 1 from flowing into the oil chamber 2. The mechanical seal 21 is disposed so as to surround the main shaft 33.

[0038] The mechanical seal 21 includes sliding portions 21a and 21b that slide in accordance with the rotation of the main shaft 33. The sliding portion 21a is provided on the motor 3 side (Z1 side) of the oil chamber 2 and prevents oil from the oil chamber 2 from flowing into the motor 3 side. The sliding portion 21b is provided on the pump chamber 1 side (Z2 side) of the oil chamber 2 and prevents the pumped liquid from the pump chamber 1 from flowing into the oil chamber 2.

[0039] As shown in Figures 6 and 7, the casing 11 includes a discharge section 20 for discharging air from within the casing 11 to the outside. The discharge section 20 is composed of a discharge port 16, a sealing member 17, a base 18, and an exhaust pipe 19. During operation of the submersible electric pump 100, the discharge port 16 is sealed by the sealing member 17, which is pushed up by the pumped liquid, preventing air from being discharged through the discharge section 20. In the submersible electric pump 100 of the present invention, the impeller width W is narrowed, which reduces the force with which the pumped liquid pushes up the sealing member 17, potentially preventing the sealing function of the sealing member 17 from functioning properly during operation of the submersible electric pump 100. Therefore, the base 18 is provided to compensate for the force of the pumped liquid pushing up the sealing member 17. In Figure 6, arrows indicate the flow of pumped liquid when the sealing member 17 seals the discharge port 16. The discharge section 20 is in communication with the lower casing 11a.

[0040] The exhaust port 16 is provided to exhaust air to the outside from the casing 11. The exhaust port 16 is provided on the Z1 side.

[0041] The sealing member 17 is disposed below (on the Z2 side of) the discharge port 16. The sealing member 17 is pushed up by the pumped liquid when the pumped liquid is sucked in, thereby sealing the discharge port 16. The sealing member 17 is spherical.

[0042] The sealing member 17 is placed on the pedestal 18. The pedestal 18 is provided on the bottom surface of the exhaust pipe 19 that communicates with the pump chamber 1. When the pumped liquid flows into the pedestal 18, the pedestal 18 forms a flow of the pumped liquid that pushes up the sealing member 17 toward the discharge port 16. The pedestal 18 has a generally V-shape with intersecting sloped portions. The pumped liquid flows from the open portion of the pedestal 18 toward the intersecting portion, and forms a flow at the intersecting portion that pushes up the sealing member 17.

[0043] The exhaust pipe 19 has a cylindrical shape. A notch that communicates with the casing 11 is provided on the Z2 side of the exhaust pipe 19. Air inside the casing 11 is discharged through the exhaust pipe 19 and the outlet 16. When the pumped liquid flows in and fills the casing 11, the pumped liquid flows into the exhaust pipe 19, and a flow is formed that pushes up the sealing member 17 (moves it in the Z1 direction) by the base portion 18. The pushed-up sealing member 17 then seals the outlet 16.

[0044] (Effects of the embodiment) In the present embodiment, the following effects can be obtained.

[0045] In this embodiment, as described above, the casing 11 faces the closed impeller 4, has a suction port 12 that protrudes convexly, and includes an suction flow passage 14 that is integrally formed with the casing 11. This allows the protruding height H of the suction flow passage 14 to be adjusted to reduce the gap G between the closed impeller 4 and the suction port 12, even when the depth of the casing 11 is increased to increase the flow rate. This reduces the gap between the closed impeller 4 and the suction port 12, minimizing the amount of pumped liquid that flows sideways through the gap between the suction port 12 and the closed impeller 4, while increasing the depth of the casing 11 to increase the flow rate. Furthermore, because the size of the gap G between the closed impeller 4 and the suction port 12 can be adjusted by the protruding height H of the suction flow passage 14, the blade width W can be reduced. This allows the blade width W to be reduced, thereby preventing pumped liquid from infiltrating into the motor 3 due to shaft deflection. As a result, it is possible to prevent the pumped liquid from infiltrating into the motor 3 side and to increase the flow rate.

[0046] In the present embodiment, as described above, the blade width W, which is the height of the closed impeller 4 including the blade portion 41, the main plate 42, and the side plate 43 in the direction in which the main shaft 33 extends, is smaller than the maximum depth D of the flow path 15 of the casing 11 in the direction in which the main shaft 33 extends by the protruding height H of the suction flow path portion 14 in the direction in which the main shaft 33 extends. This allows the blade width W of the closed impeller 4 to be reduced by the protruding height H of the suction flow path portion 14, and therefore the blade width W can be easily reduced. As a result, it is possible to prevent the main shaft 33 from bending due to an increase in the blade width W, and therefore it is possible to easily prevent the pumped liquid from entering the motor 3 side.

[0047] In this embodiment, as described above, the suction passage 14 has a cylindrical shape extending from the suction port 12 side toward the closed impeller 4 side. This allows the pumped liquid to be sucked through the cylindrical internal passage of the suction passage 14.

[0048] In this embodiment, as described above, the side plate 43 of the closed impeller 4 has an opening 43a that opens to the suction passage 14 side, and the inner diameter r1 of the opening 43a and the inner diameter r2 of the end of the suction passage 14 on the closed impeller 4 side are approximately the same when viewed from the extending direction of the main shaft 33. This allows the diameters of the flow passages connected from the suction passage 14 to the closed impeller 4 to be approximately the same, so that the closed impeller 4 can efficiently suck in the pumped liquid that has passed through the suction passage 14.

[0049] In this embodiment, as described above, the casing 11 and the suction passage 14 are integrally formed from resin, which makes it possible to easily form the casing 11 provided with the suction passage 14.

[0050] In this embodiment, as described above, the side plate 43 of the closed impeller 4 has an opening 43a that opens to the suction passage 14 side, and the opening 43a and the suction passage 14 are disposed with a gap of 5 mm or less in the extension direction of the main shaft 33. This makes it possible to minimize the amount of pumped liquid that flows sideways through the gap between the opening 43a and the suction passage 14, thereby preventing a decrease in the efficiency of the submersible electric pump 100.

[0051] In this embodiment, as described above, the protruding height H of the suction passage portion 14 in the direction in which the main shaft 33 extends is 20% or more of the maximum depth D of the passage 15 in the direction in which the main shaft 33 extends. This makes it possible to manufacture a submersible electric pump 100 with a sufficiently large flow rate while preventing the blade width W of the closed impeller 4 from becoming too large. This effect has been proven by the inventors of the present application through experiments (examples) described below.

[0052] In this embodiment, as described above, the casing 11 includes the discharge port 16 for discharging air from within the casing 11, the sealing member 17 that is disposed below the discharge port 16 and is pushed up by the pumped liquid when the pumped liquid is sucked in, thereby sealing the discharge port 16, and the base 18 on which the sealing member 17 is placed and that forms a flow of the pumped liquid that pushes the sealing member 17 up toward the discharge port 16. As a result, by positioning the intersecting portion of the inclined surfaces of the base 18 below and near the center of gravity of the sealing member 17, the sealing member 17 can be stably pushed up, and therefore the sealing member 17 can be reliably pushed up to the position of the discharge port 16 and the discharge port 16 can be reliably sealed.

[0053] In this embodiment, as described above, the base portion 18 has a substantially V-shape, which allows the pumped liquid to be collected by the sloped surface forming the V-shape, thereby increasing the force pushing up the sealing member 17.

[0054] (Example) Flow rate (m ) of the submersible electric pump 100 with different ratios of the protrusion height H of the suction flow passage portion 14 to the maximum depth D of the flow passage 15 in the extension direction of the main shaft 33 3The relationship between the head (m / min) and the head was investigated. In addition, when a submersible electric pump 100 with a sufficiently large flow rate is sold as a product, a desirable relationship between the head and the flow rate was set as a target value, and each measurement result was compared with the target value. Specifically, the following examples were prepared: Example 1 in which the head was 18.3% (the ratio of the impeller width W to the maximum depth D of the flow passage 15 was 73.8%); Example 2 in which the head was 23.2% (the ratio of the impeller width W to the maximum depth D of the flow passage 15 was 69.0%); Example 3 in which the impeller width W was 27.2% (the ratio of the impeller width W to the maximum depth D of the flow passage 15 was 65.0%); and Example 4 in which the protruding height H of the suction flow passage portion 14 was 32.1% of the maximum depth D of the flow passage 15 (the ratio of the impeller width W to the maximum depth D of the flow passage 15 was 60.0%). 3 / min) and head (m). In Figure 8, the vertical axis plots head (m) and the horizontal axis plots flow rate (m 3 / min) were plotted. As a result of the experiment, it was found that in all cases the flow rate could be increased beyond the limit at which the target flow rate could be increased (the point where the graph is broken). It was also found that it was possible to manufacture a submersible electric pump 100 with a sufficiently large flow rate even when the protruding height H of the suction flow passage 14 was set to 18% or more of the maximum depth D.

[0055] The flow rate (m 3 The relationship between the flow rate (m / min) and the shaft power (kW) was investigated. 3 / min) and shaft power (kW). 3 In Fig. 9, the vertical axis plots the shaft power (kW) and the horizontal axis plots the flow rate (m 3 9, the inventors have found that the submersible electric pump 100 of the present invention, by providing the suction flow path portion 14, can sufficiently increase the flow rate to the same extent as a submersible electric pump with 95% rated power.

[0056] The flow rate (m 3 The relationship between the flow rate (m / min) and the pump efficiency (%) was investigated. 3 In FIG. 10, the vertical axis plots the pump efficiency (%) and the horizontal axis plots the flow rate (m 3 10, the inventors of the present invention have found that a constant pump efficiency can be maintained even when the flow rate is increased.

[0057] From the above results, the inventors have found that, under the constraint of a given shaft power, it is possible to sufficiently increase the flow rate and maintain a certain level of pump efficiency by adjusting the protruding height H of the suction passage 14 while maintaining a small impeller width W in order to suppress deflection. Furthermore, it is also possible to further optimize the submersible electric pump 100 by appropriately adjusting the outer diameter of the impeller width.

[0058] (Modifications) The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the description of the above-mentioned embodiments, and includes all modifications (modifications) within the meaning and scope of the claims.

[0059] For example, in the above embodiment, the suction passage portion is cylindrical, but the present invention is not limited to this. In the present invention, for example, the suction passage portion may be configured as a rectangular parallelepiped.

[0060] In the above embodiment, the inner diameter of the opening and the inner diameter of the end of the suction passage on the closed impeller side are substantially the same when viewed from the direction in which the main shaft extends, but the present invention is not limited to this. In the present invention, the inner diameter of the opening and the inner diameter of the end of the suction passage on the closed impeller side when viewed from the direction in which the main shaft extends may be different.

[0061] In the above embodiment, the casing and the suction passage are integrally formed from resin, but the present invention is not limited to this. In the present invention, the casing and the suction passage may be integrally formed from metal.

[0062] In the above embodiment, the base portion is formed in a substantially V-shape, but the present invention is not limited to this. In the present invention, the base portion may be formed in, for example, a substantially U-shape.

[0063] In the above embodiment, the upper casing and the lower casing are formed separately, but the present invention is not limited to this. In the present invention, the upper casing and the lower casing may be integrally formed.

Claims

DEPCT671. Electric submersible pumps assembled with a housing (11) incorporating a volute-shaped flow path (15) and a suction port (12) for drawing liquid into the flow path; a closed impeller assembly (4) incorporating the impeller fins (41), a main plate (42) holding the impeller fins, and side plates (43) that are open on the suction port side of the housing; and an electric motor (3) incorporating the main shaft connected to the closed impeller assembly in which the housing incorporates the suction path (14) facing the closed impeller assembly, with protruding, convex suction ports and a construction 1. The impeller is formed as a single unit with the housing.

2. Electric submersible pumps under claim 1 where the impeller blade width, which is the height of the enclosed impeller assembly including the impeller blades and the main and side plates in the main shaft overhang direction, is less than the maximum depth of the housing flow path in the main shaft overhang direction by an amount equal to the overhang height of the suction path in the main shaft overhang direction.

3. Electric submersible pumps under claim 1 or 2 where the suction path has a cylindrical shape extending from the suction port side to the enclosed impeller assembly side. 4.

5. Any submersible electric pump under Reputation 1 to 4 in which the side plate of the enclosed impeller has an opening on the suction path side and the inner diameter of the opening is substantially equal to the inner diameter of the suction path on the end of the enclosed impeller when viewed in the main shaft overhang direction.

6. Any submersible electric pump under Reputation 1 to 5 in which the side plate of the enclosed impeller has an opening on the suction path side and the opening and the suction path are spaced no more than 5 mm apart in the main shaft overhang direction.

7. Any submersible electric pump under Reputation 1 to 6 in which the overhang height of the suction path in the main shaft overhang direction is not less than 20% of the maximum depth of the flow path in the main shaft overhang direction. 8.

9. Electric submersible pumps under any of the claims 1 through 7 in which the housing includes a vent (16) for venting of the housing, a sealing assembly (17) provided beneath the vent and constructed to be pushed upward by the fluid to seal the vent when the fluid is drawn, and a base (18) constructed to receive the sealing assembly and to form an upward flow of fluid to push the sealing assembly into the vent.

10. Electric submersible pumps under claim 8 in which the base is generally V-shaped;

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