JP2016507698A - Pump with a shield to protect the pump wheel against coolant leakage along the hub of the pump wheel - Google Patents

Abstract

The pump according to the present invention comprises a flow chamber (4) for heat transport fluid, a pump wheel (10) generally disposed in the flow chamber (4) and provided with a hub (40), and a pump wheel (10). A shaft (14) for rotating the pump wheel (10) having an axial end portion (12) that is firmly connected and fitted into a hub (40) of the pump wheel (10), and a shaft (14) A motor for rotating about the axis and means for flowing a coolant for cooling the drive shaft (14) along the drive shaft (14) at a temperature lower than the temperature of the heat transport fluid. The pump further comprises a shield (120) for protecting the pump wheel (10) against coolant leakage along the outer peripheral surface (48) of the hub (40) of the pump wheel (10), and the protection The shield (120) is attached to the pump wheel (10).

Description

The present invention provides a heat transport fluid for flowing in a fluid circuit,
-A flow chamber for heat transport fluid,
-A pump wheel arranged entirely in the flow chamber and equipped with a hub;
-A shaft for rotating the pump wheel, having an axial end portion firmly connected to the pump wheel and fitted into the hub of the pump wheel;
-A motor for rotating the shaft around its axis;
-A pump of the kind comprising a coolant for cooling the drive shaft at a temperature below the temperature of the heat transport fluid and means for flowing along the drive shaft.

  In a reactor cooled by pressurized water, the pressurized coolant water of the reactor is a primary pump with a single pump wheel submerged in the pressurized water that fills the primary circuit in the reactor core cooling circuit or in the primary circuit Flowed by a pump called

  The pump wheel is driven by an electric motor positioned externally at a specific distance from the primary circuit via a drive shaft that is coupled at one end to the pump wheel. The drive shaft traverses between a first end section fixed to the pump wheel and a second end section fixed to the rotor of the electric motor through a set of cooling and sealing means. Yes.

  Inside the pump body connected to the primary circuit piping, the pump wheel and the first end section of the drive shaft are submerged in pressurized water at a temperature of approximately 300 ° C. The shaft, between its first and second sections, contains an enclosure containing a thermal barrier made from a network of tubes that are internally cooled by the flow of exchange fluid, and the rotation of the shaft And a means which makes it possible to ensure a tight passage of the shaft between the body of the pump receiving pressurized water and the outer part of the pump including the drive motor.

The role of the thermal barrier is to prevent heat from the primary water from rising towards the upper part of the pump. Further, during normal operation, cooling water at a temperature below 60 ° C. is injected at the thermal barrier to form a dam between the primary circuit and the shaft sealing device. Therefore, the pressure of this injection circuit is slightly higher than the pressure of the primary circuit. The injection flow rate is divided into the following two.
-A part of the flow flows downwards, ie through play between the shaft and the thermal barrier.
-Another part of the flow flows upward, i.e. through the pump bearing and the sealing device.

  Therefore, there is no possibility that water from the primary circuit contaminated by radioactive elements taken from the reactor core leaks through the sealing device.

  Under these conditions, when the pump is operating, the pump wheel is at a temperature close to the temperature of the primary circuit water, while the shaft is cooled by its thermal barrier and injection water at its upper part, The temperature is less than This results in loss of coupling between the shaft and the pump wheel, which further causes contact wear at the connection between the shaft and the pump wheel, followed by degradation at the shaft and pump wheel contact surfaces. cause. Therefore, regular maintenance of the primary pump is necessary to ensure optimal retention of the pump wheel on the shaft.

  In order to solve this problem, a system has been proposed for flowing water from the primary circuit in the first end section of the shaft. Such a system in fact allows the first end section to be kept at a temperature close to that of the pump wheel and prevents loss of coupling due to the presence of a temperature gradient between the shaft and the pump wheel. To do. Such a system is disclosed in Patent Document 1.

  However, such a system is not completely satisfactory. Indeed, despite the presence of this system for flowing primary circuit water in the first end section of the shaft, evidence of shaft and pump wheel degradation due to contact wear is still observed.

European Patent Application No. 0,257,140

  Therefore, one object of the present invention is to reduce the maintenance cost of the primary pump, specifically by reducing the contact wear between the pump wheel and the drive shaft.

  To that end, the present invention relates to a pump of the aforementioned type and further comprises a shield for protecting the pump wheel against coolant leakage along the outer peripheral surface of the hub of the pump wheel. The protective shield is attached to the pump wheel.

According to a preferred embodiment of the invention, the pump also has one or more of the following characteristics, either alone or according to any technically possible combination.
The protective shield is formed by an annular crown with a substantially cylindrical peripheral wall that is coaxial with and surrounds the hub.
The peripheral wall has an inner diameter with a difference in diameter relative to the outer diameter of the hub, said difference in diameter being less than 1.5 mm;
-The difference in diameter is greater than 0.1mm.
The annular crown comprises an inner peripheral edge extending substantially radially from the peripheral wall towards the axis of the peripheral wall;
-The inner periphery is flush with the shaft.
The annular crown further comprises an outer peripheral edge protruding from the peripheral wall opposite to the axis of the peripheral wall, said outer peripheral edge extending along the surface of the pump wheel;
-The protective shield is fastened to the pump wheel by the outer periphery.
-A sealing body is inserted between the outer periphery and the pump wheel.
The inner peripheral edge protrudes from the first axial end of the peripheral wall and the outer peripheral edge protrudes from the second axial end of the peripheral wall opposite the first axial end;
The pump comprises means for flowing the heat transport fluid in the axial end section of the shaft fitted in the hub;
-The pump comprises a key that connects the pump wheel to the shaft, the pump wheel has a first axial slot for receiving the key, and the shaft has a second axial slot for receiving the key. The key and the pump wheel are provided with complementary members for blocking the axial direction of the key with respect to the pump wheel.
-The first axial slot is exposed at the axial end of the pump wheel through the window, and a protective shield obstructs the window.
-Pump wheel is connected to the shaft.
-A protective shield is attached to the pump wheel.
The axial end section in which the drive shaft is oriented substantially vertically and fits into the hub is the lower end section of the shaft.
-The primary circuit of the reactor, where the pump is the primary pump and the fluid circuit is specifically a pressurized water reactor.

  Other features and advantages of the present invention will become apparent upon reading the following description provided, by way of example only, with reference to the accompanying drawings.

FIG. 3 is a partial cross-sectional view of an elevation surface of a pump according to the present invention. FIG. 2 is a diagram of a detailed portion denoted by reference numeral II in FIG. FIG. 3 is a diagram of a detailed portion denoted by reference numeral III in FIG.

  A pump 1 shown in FIG. 1 is a primary pump of a pressurized water reactor. This pump 1 is suitable for flowing heat transport fluid, in this case pressurized water at a temperature close to 300 ° C., in the fluid circuit, in this case in the primary circuit of the reactor.

  For that purpose, the primary pump 1 comprises a chamber 4 or a swirl defining a swirl for flowing a heat transport fluid, the pump body 2 using a first pipe part 6 It is fluidly connected to the first pipe of the heat transport fluid, and is fluidly connected to the second pipe of the primary circuit using the second pipe portion 8, and the first pipe portion 6 and the second pipe The pump 1 creates a specific pump pressure in order to flow the heat transport fluid.

  The pump 1 further includes a pump wheel 10 for creating a pump pressure between the first pipe portion 6 and the second pipe portion 8. The pump wheel 10 is coupled to a lower axial end section 12 of the drive shaft 14 that is substantially vertically oriented, and the upper axial end section 16 of the drive shaft 14 is coupled to the pump wheel using a coupler 18. It is connected to a rotor of an electric motor 20 for driving 10 rotations.

  A bearing 22 provides a connection of the shaft 14 to the pump body 2 and guides the shaft 14 in rotation about its axis.

  With reference to FIG. 2, around the drive shaft 14, means 32 for cooling the shaft 14 are located in an enclosure 30 surrounding the shaft 14.

  The pump body 2 separates the flow chamber 4 from the enclosure 30. In other words, the wall 34 of the pump body 2 extends between the flow chamber 4 and the enclosure 30. The wall 34 has a through-orifice 36 that is exposed in the flow chamber 4 and the enclosure 30 for penetration of the drive shaft 14.

  Specifically, the cooling means 32 is formed by a circuit network of pipes through which the exchange fluid circulates, and includes a thermal barrier 38 accommodated in the enclosure 30. The thermal barrier 38 functions to prevent heat from the heat transport fluid from rising toward the upper part of the pump 1.

  The cooling means 32 is means for injecting pressurized coolant into the enclosure 30 at a temperature below 60 ° C. and for flowing the coolant along the drive shaft 14 in the enclosure 30 ( (Not shown) is also provided in a known manner. The coolant partially flows downward through the orifice 36 and partially flows upward through the bearing 22.

  The pump wheel 10 is completely arranged in the flow chamber 4. In other words, the pump wheel 10 does not extend into the enclosure 30. Thus, the pump wheel 10 is completely submerged in the heat transport fluid flowing inside the flow chamber 4, as is the end section 12.

  Still referring to FIG. 2, the pump wheel 10 includes a hub 40, an annular ring 42 extending around the hub 40, and a plurality of blades 44 supported by the ring 42.

  The hub 40 is tubular. The hub 40 is coaxial with the shaft 14 and is fitted in the lower axial end section 12. The hub 40 has an inner peripheral surface 46 that is in contact with the shaft 14 and an outer peripheral surface 48 opposite to the inner peripheral surface 46.

  The inner peripheral surface 46 has a substantially frustoconical shape that narrows toward the bottom to facilitate mounting of the wheel 10 to the shaft 14.

  An annular ring 42 surrounds the hub 40. The annular ring 42 protrudes outward and upward from the lower end of the hub 40. Accordingly, the annular ring 42 is substantially in the form of a hollow cone that narrows downward and extends upward.

  The annular ring 42 has an upper surface 50 that forms an annular plate 52 that defines a substantially radial plane at the point of contact with the outer peripheral surface 48 of the hub 40. The plate 52 is drawn downward with respect to the upper ends 54 and 56 of the hub 40 and the ring 42.

  The annular ring 42 further has a lower surface 58 opposite the upper surface 50.

  Each blade 44 protrudes downward from the lower surface 58 of the ring 42.

  The pump wheel 10 is a single item.

  The drive shaft 14 includes, in addition to the lower axial end area 12, a central area 60 surrounded by the enclosure 30, an intermediate area 62 inserted between the central area 60 and the lower axial end area 12, It has.

  The central area 60 is substantially rotating cylindrical and has a first diameter. The central area 60 defines a downwardly oriented radial shoulder 64 at the junction with the intermediate area 62.

  The intermediate section 62 is substantially rotating cylindrical and has a second diameter that is smaller than the first diameter. The intermediate section 62 extends through the through orifice 36.

  A heat protection ring 66 is fitted in the intermediate section 62 and rests against the shoulder 64. The ring 66 is specifically joined at the area 62. The ring 66 is designed to protect the shaft 14 against temperature gradients that exist inside the enclosure 30 and inside the flow chamber 4.

  The lower axial end region 12 is fully fitted into the hub 40. The lower axial end region 12 has a slightly frustoconical shape that narrows downward. Specifically, this shape is complementary to the shape of the inner peripheral surface 46 of the hub 40.

  The maximum diameter of the lower axial end section 12 is preferably substantially equal to the second diameter, as shown.

  Pump 1 also includes a nut 70 for axially securing pump wheel 10 to shaft 14 and a key 72 for rotatably securing pump wheel 10 to shaft 14 with reference to FIG. I have.

  The lower axial end region 12 defines a recess 74 for receiving a nut 70 that is exposed at the lower axial end 76 of the shaft 14. The recess 74 has a substantially rotating cylindrical shape, is coaxial with the shaft 14, and is threaded on the inside.

  The nut 70 is screwed into the shaft 14. The nut 70 includes a nut main body 80 and a nut head 82.

  The nut body 80 is substantially a rotating cylindrical shape. The nut body 80 has a diameter that is substantially equal to the diameter of the recess 74 and has an outer thread that cooperates with the tapping of the recess 74.

  The nut head 82 has a diameter that is larger than the diameter of the lower end 76 of the shaft 14. The nut head 82 defines an upwardly oriented radial shoulder 84 and rests against the pump wheel 10. Therefore, the pump wheel 10 cannot move downward with respect to the shaft 14.

  The nut 70 advantageously has an axial passage 86 for the check screw 88. The check screw 88 is screwed into the lower axial end section 12 having a pitch opposite to the screw pitch of the nut 70 in the lower axial end section 12 and the head 90 of the check screw 88 leans against the head 82 of the nut 70. It is hanging. Specifically, the head 90 of the check screw 88 is welded to the wheel nut 70 in order to prevent the wheel nut 70 from loosening.

  The hub 40 of the pump wheel 10 has a first axial slot 92 for receiving the key 72 and the lower axial end section 12 has a second axial slot 94 for receiving the key 72. doing. The slots 92, 94 are positioned directly opposite each other, and a key 72 is engaged in each of the two slots 92, 94. Thus, when coupling is lost, the key 72 can transmit rotational torque from the shaft 14 to the pump wheel 10.

  The first slot 92 is exposed through the window 96 at the upper end 54 of the hub 40.

  Pump wheel 10 and key 72 include complementary means for axially securing key 72 to wheel 10. Thus, the pump wheel 10 can be mounted on the drive shaft 14 by a key 72 that is already engaged in the first slot 92. In the illustrated example, these complementary means are made from a protrusion 100 secured to the key 72 and an orifice 102 disposed in the hub 40 for receiving the protrusion 100. Specifically, the protrusion 100 protrudes radially outward from the key 72.

  Still referring to FIG. 2, the pump 1 also includes means for flowing the heat transport fluid within the lower axial end section 12. In the example shown here, these flow means are formed by a centrifugal auxiliary wheel integrated with the wheel nut 70.

  For that purpose, the wheel nut 70 is arranged in the nut head 82 and has a plurality of inclined channels 104 fluidly connecting the passage 86 to the flow chamber 4 and the nut body 80 around the passage 86. A plurality of axial flow paths 106 disposed and a plurality of radial flow paths 108 disposed in the nut head 82 and each fluidly connecting the axial flow paths 106 to the flow chamber 4. doing. In addition, the nut body 80 has a smaller diameter upper axial end section to place the ring 110 welded to the nut 70 in the extension of the radial flow path 106 and the gap 112 is axial It remains free between the channel 106 and the ring 110. Finally, an axial space 114 is disposed between the bottom of the recess 74 and the wheel nut 70 in order to place the passage 86 in fluid communication with each axial flow path 106 by bypassing the ring 110. The peripheral space 116 is disposed between the peripheral wall of the recess 74 and the ring 110.

  According to the present invention, referring to FIG. 3, the pump 1 further includes a shield 120 for protecting the pump wheel 10 from coolant flow along the outer peripheral surface 48 of the hub 40 of the wheel 10.

  This protective shield 120 is attached to the pump wheel 10. The protective shield 120 is formed from an annular metal crown, typically made of stainless steel or nickel alloy (INCONEL), with a substantially cylindrical peripheral wall and from the peripheral wall toward the axis of the peripheral wall 122. An inner peripheral edge 124 extending substantially in the radial direction, and an outer peripheral edge 126 protruding from the peripheral wall 122 opposite to the axis of the peripheral wall 122.

  The peripheral wall 122 is coaxial with the hub 40 and surrounds the hub 40. The peripheral wall 122 has a difference in diameter with respect to the outer diameter of the hub 40, and the difference in diameter is to form a narrow fluid cavity commonly referred to as a “water space” between the protective shield 120 and the hub 40. Larger than 0.1 mm, preferably smaller than 1.5 mm.

  The inner peripheral edge 124 protrudes from the upper end 130 of the peripheral wall 122 toward the inside of the peripheral wall 122. The inner peripheral edge 124 extends substantially along the upper end 54 of the hub 40, and a height gap (not shown) comprised between 0.1 mm and 1.5 mm is provided between the inner peripheral edge 124 and the upper end 54. Is left free between.

  The inner peripheral edge 124 blocks a window 96 through which the first slot 92 is exposed at the upper end 54 of the hub 40. Therefore, the inner peripheral edge 124 extends from the peripheral wall 122 until it is flush with the shaft 14. Specifically, the inner peripheral edge 124 is flush with the shaft 14 over its entire contour.

  The inner peripheral edge 124 is inserted axially between the upper end 54 of the hub 40 and the heat protection ring 66. Preferably, the inner peripheral edge 124 is axially spaced from the heat protection ring 66 by a few millimeters.

  The outer peripheral edge 126 protrudes from the lower end 132 of the peripheral wall 122 toward the outside of the peripheral wall 122. The outer peripheral edge 126 extends along the plate 52.

  A plurality of screws 134 extend through the outer periphery 126 and are screwed into the pump wheel 10 to secure the outer periphery 126 to the pump wheel 10. Alternatively, the outer periphery 126 is welded to the pump wheel 10. Accordingly, the protective shield 120 is fastened to the pump wheel 10 by the outer periphery 126 and is not fastened to the pump wheel at any other location, but is exclusively fastened to the pump wheel 10.

  As shown in FIG. 3, an annular sealing body 136 is inserted between the outer peripheral edge 126 and the plate 52. The sealing body 136 is typically a C-ring type metal seal.

  Thanks to the present invention described above, loss of coupling between the pump wheel 10 and the drive shaft 14 is avoided.

  In fact, due to the presence of the protective shield 120, some of the downward flowing coolant flow cannot flow directly to the hub 40 of the wheel 10. This results in slow cooling of the hub 40 under the effect of the coolant when the pump 1 is stopped when the furnace is stopped at a high temperature. This makes it possible to prevent the hub 40 from cooling more quickly than the shaft 14, and in doing so the grip around the shaft 14 which remains inflated, causing the coupling to be lost. 40 prevents deformation. This delay in the cooling of the hub 40 is due to the difference in diameter between the peripheral wall 122 and the hub 40, and water is trapped between the shield 120 and the hub 40, and the water is present in the presence of the seal 136. Therefore, it cannot flow downward, so that the water is even more important considering that it forms a stagnant water space that reinforces the thermal insulation provided by the shield 120.

  Further, since the shield 120 blocks the window 96, the coolant cannot flow through the first slot 92. This avoids more significant local cooling of the hub 40 and shaft 15 that can cause cracks in the pump wheel 10 and shaft 15.

A thermomechanical simulation is performed in order to compare the residual bonding force between the present invention described above and the pump described in Patent Document 1. To that end, each of the two pumps was exposed to a series of 10 cycles each including the following series of steps.
-Heat the heat transport fluid from 20 ° C to 300 ° C at a rate of 40 ° C per hour.
-Stop pump heating, heat transport fluid is 300 ° C, coolant injection is maintained, fluid temperature in the flow chamber is very stable at 150 ° C after 120 seconds on the back side of the pump wheel It drops quickly.
-Begin pump heating again and the wheel is quickly heated to a temperature of 300 ° C by the heat transport fluid.
-Cooling the furnace, the temperature of the heat transport fluid proceeds from 300 ° C to 20 ° C at a rate of 55 ° C per hour.

  After these 10 cycles, stabilization of the deformation is observed. The pump 1 has a residual bond pressure gain of 360% for the heating rotation and 180% for the cooling rotation as compared with the pump described in Patent Document 1.

  Thus, these results clearly show the benefits of the present invention over the state of the art.

  It should be noted that although the pump described is a primary pump for a pressurized water reactor, the invention is not limited to this type of pump. The present invention relates generally to any type of pump for flowing heat transport fluid into a fluid circuit, and is particularly applicable to the primary pumps of other nuclear reactors, such as boiling water reactors. .

1 Primary pump
2 Pump body
4 Flow chamber
6 First pipe
8 Second pipe
10 Pump wheel
12 Lower axial end area
14 Drive shaft
16 Upper axial end area
20 Electric motor
22 Bearing
30 enclosure
32 Cooling means
34 walls
36 Through orifice
38 Thermal barrier
40 hub
42 rings
44 feathers
46 Inner surface
48 Outer surface
50 Upper side
52 Annular plate
54 Upper edge
56 Upper edge
60 central area
62 Middle area
64 radial shoulder
66 Thermal protection ring
70 nuts
72 keys
74 recess
76 Lower axial end
80 Nut body
82 Nut head
84 Radial shoulder
86 Axial passage
88 Check screw
90 head
92 First axial slot
94 Second axial slot
96 windows
100 protrusions
102 Orifice
104 inclined channel
106 Axial flow path
108 radial flow path
110 rings
112 Clearance
114 Axial space
116 Surrounding space
120 Protective shield
122 wall
124 Inner rim
126 Outer periphery
130 Upper edge
132 Lower edge
134 screws
136 Annular seal

Claims (15)

A pump (1) for flowing heat transport fluid into the fluid circuit,
A flow chamber (4) for heat transport fluid;
A pump wheel (10) generally disposed in the flow chamber (4) and provided with a hub (40);
For rotating the pump wheel (10) having an axial end portion (12) securely connected to the pump wheel (10) and fitted into the hub (40) of the pump wheel (10). The shaft (14),
A motor (20) for rotating the shaft (14) about its axis;
Means for flowing a coolant for cooling the drive shaft (14) along the drive shaft (14) at a temperature lower than the temperature of the heat transport fluid;
In the pump (1) with
The pump further includes a shield (120) for protecting the pump wheel (10) against coolant leakage along the outer peripheral surface (48) of the hub (40) of the pump wheel (10). A pump (1), characterized in that the protective shield (120) is attached to the pump wheel (10).   The protective shield (120) is formed by an annular crown (122) having a substantially cylindrical peripheral wall that is coaxial with and surrounds the hub (40). The pump according to (1).   The pump (1) according to claim 2, wherein the peripheral wall (122) has an inner diameter with a difference in diameter with respect to an outer diameter of the hub (40), wherein the difference in diameter is less than 1.5 mm.   The pump (1) according to claim 3, wherein the difference in diameter is greater than 0.1 mm.   5. The annular crown according to any one of claims 2 to 4, comprising an inner peripheral edge (124) extending substantially radially from the peripheral wall (122) toward the axis of the peripheral wall (122). Pump (1) according to paragraph.   The pump (1) according to claim 5, wherein the inner peripheral edge (124) is flush with the shaft (14).   The annular crown further includes an outer peripheral edge (126) protruding from the peripheral wall (122) opposite to the axis of the peripheral wall (122), and the outer peripheral edge (126) is a surface of the pump wheel (10). The pump (1) according to any one of claims 2 to 6, which extends along (52).   The pump (1) according to claim 7, wherein the protective shield (120) is fastened to the pump wheel (10) by the outer periphery (126).   The pump (1) according to claim 7 or 8, wherein a sealing body (136) is inserted between the outer peripheral edge (126) and the pump wheel (10).   The inner peripheral edge (124) protrudes from the first axial end (130) of the peripheral wall (122), and the outer peripheral edge (126) extends from the second axial end (132) of the peripheral wall (122). 10. The pump (1) according to any one of claims 7 to 9, in combination with claim 5 or 6, projecting opposite the first axial end (130).   A means for flowing the heat transport fluid into the axial end section (12) of the shaft (14) fitted in the hub (40). The pump according to (1).   A key (70) connecting the pump wheel (10) to the shaft (14), the pump wheel (10) having a first axial slot (92) for receiving the key (70); And the shaft has a second axial slot (94) for receiving the key (70), the key (70) and the pump wheel (10) being located relative to the pump wheel (10). 12. A pump (1) according to any one of the preceding claims, comprising a complementary member (100, 102) for axial blocking of the key (70).   The first axial slot (92) is exposed at the axial end (54) of the pump wheel (10) through the window (96), and the protective shield (120) passes through the window (96). 13. The pump (1) according to claim 12, which is interrupted.   The pump (1) according to any one of the preceding claims, wherein the pump wheel (10) is coupled to the shaft (14).   The drive shaft (14) is oriented substantially vertically and the axial end section (12) fitted in the hub (40) is a lower end section of the shaft (14). The pump (1) according to any one of 14 above.

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