Multistage vertical molten salt pump axial force balancing device and multistage vertical molten salt pump

Abstract

The application provides a multi-stage vertical molten salt pump axial force balancing device and a multi-stage vertical molten salt pump. An axial force balancing device is arranged between a space guide vane and an impeller. The axial force balancing device has a third balancing cavity and a first balancing cavity. A labyrinth gap is arranged between the first balancing cavity and a pressure cavity of the impeller. The third balancing cavity is arranged in the space guide vane. An elastic damping is arranged between the first balancing cavity and the third balancing cavity, and is used for balancing the axial force received by the impeller. The application can realize instant response to the axial force received by the pump rotor, and can divide the main axial force received by the impeller into two parts. The axial force received by the multi-stage vertical molten salt pump is balanced by the two gaps before the first balancing cavity, the spring bidirectional action and the low-pressure state of the third balancing cavity, so that the stable operation of the vertical multi-stage molten salt pump is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of molten salt pump, in particular to a kind of multistage vertical molten salt pump axial force balancing device and multistage vertical molten salt pump. BACKGROUND

[0002] Vertical multistage molten salt pump is the core power device of photo-thermal power station, in actual work, due to the asymmetry of impeller front and rear cover plate, the different of impeller front and rear cavity flow passage and the influence of rotor self weight, axial force along axial direction will be generated during operation. The molten salt pump of photo-thermal system adopts the structure form that multistage impeller is arranged in the same direction, and the installation mode of vertical arrangement, so that the axial force received by the rotor structure gradually increases from top to bottom along the pump shaft, and the accumulation is realized at the first stage impeller on the lower section shaft.

[0003] Axial force will cause the rotor to move along the axial direction, cause the contact between rotor assembly and stationary part, produce abrasion, increase the vibration and noise of device, reduce the operation efficiency of pump. Excessive axial force will make the impeller move to the inlet direction, increase the friction of impeller and pump shell, increase the load of motor, and then damage the sealing structure, cause the increase of device leakage, increase the power consumption of pump. For multistage pump, the influence of axial force is more prominent, excessive axial force will cause the overheating damage of supporting bearing, and even may cause the shaft fracture and other serious problems, which threatens the safe and stable operation of pump. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application provides a kind of multistage vertical molten salt pump axial force balancing device and multistage vertical molten salt pump, novel structure, can balance the axial force received by pump rotor, effectively improve the safety and reliability of multistage molten salt pump operation.

[0005] The present application achieves the above technical purpose by the following technical means.

[0006] A kind of multistage vertical molten salt pump axial force balancing device, axial force balancing device is arranged between space guide vane and impeller, the axial force balancing device has third balancing cavity and first balancing cavity, labyrinth gap is arranged between the first balancing cavity and the pressure cavity of impeller;The third balancing cavity is located in the interior of space guide vane, elastic damping is arranged between the first balancing cavity and the third balancing cavity, for balancing the axial force received by impeller.

[0007] Further, the axial force balancing device comprises a cylinder, an elastic damping and an adjusting slide plate; the cylinder comprises an end cover and an outer cylinder wall, the outer cylinder wall is provided with the end cover at one end, the end cover is located inside the space guide vane and connected with the space guide vane; the other end of the outer cylinder wall is matched with the impeller gap; the adjusting slide plate is located inside the cylinder and connected with the back cover plate of the impeller, the adjusting slide plate divides the cylinder into a first balancing cavity and a third balancing cavity, and the elastic damping is arranged between the adjusting slide plate and the cylinder; the adjusting slide plate, the outer cylinder wall and the back cover plate form the first balancing cavity; and the area between the other side of the adjusting slide plate and the end cover forms the third balancing cavity.

[0008] Further, a sealing structure is arranged between the adjusting slide plate and the inner wall of the outer cylinder wall.

[0009] Further, the sealing structure is a ring-shaped metal brush wire, and the adjusting slide plate is provided with a plurality of spaced grooves at one end, and the ring-shaped metal brush wire is located in the grooves.

[0010] Further, a first gap is arranged between the back cover plate and the space guide vane, and a second gap is arranged between the back cover plate and the outer cylinder wall, and the first gap and the second gap form a labyrinth gap between the first balancing cavity and the pressure cavity.

[0011] Further, the inner wall of the outer cylinder wall is provided with a protrusion, and a spring is arranged between the protrusion and the adjusting slide plate.

[0012] Further, a second balancing cavity is arranged between the first balancing cavity and the pressure cavity, and the second balancing cavity is a region surrounded by the space guide vane, the cylinder and the back cover plate.

[0013] A multi-stage vertical molten salt pump comprises a plurality of impellers, and the axial force balancing device is arranged between at least one impeller and the corresponding space guide vane.

[0014] The beneficial effects of the present application are as follows:

[0015] The multi-stage vertical molten salt pump axial force balancing device has the axial force balancing device arranged between the space guide vane and the impeller, the elastic damping arranged between the first balancing cavity and the third balancing cavity, the automatic balancing of the axial force on the pump rotor realized by the pressure cavity, the labyrinth gap, the third balancing cavity and the elastic damping, the real-time monitoring of the axial force on the pump body realized by the infrared distance measuring device in the balancing device during operation, and the safety of the multi-stage vertical molten salt pump improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the description of the embodiments or the prior art. The drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0017] Figure 1 The schematic diagram of the multi-stage vertical molten salt pump described in the present application.

[0018] Figure 2 The schematic diagram of the installation of the axial force balancing device described in the present application.

[0019] Figure 3 The schematic diagram of the installation of the axial force balancing device described in the present application. Figure 2 The partial enlarged view.

[0020] Figure 4 The schematic diagram of the installation of the sealing structure described in the present application.

[0021] Figure 5 The three-dimensional view of the axial force balancing device described in the present application.

[0022] Figure 6 The force comparison diagram between the installation of the axial force balancing device and the prior art.

[0023] Figure 7 The flow comparison diagram under different flow conditions of the installation of the balancing device.

[0024] Figure 8 The comparison diagram of the external characteristic parameters of the single-stage pump with the installation of the balancing device, without the installation of the balancing device and the prior art.

[0025] In the diagram:

[0026] 1-inlet section; 2-primary impeller; 3-secondary impeller; 4-space guide vane; 5-pump shaft; 6-intermediate section; 7-outlet section; 8-balancing device; 9-back cover plate; 10-fixed module; 11-adjusting slide plate; 12-spring; 13-end cover; 14-outer side cylinder wall; 15-infrared distance measuring device; 16-sealing structure; 17-balancing hole; 18-sliding bearing; a-first gap; b-second gap; 101-pressure cavity; 102-second balancing cavity; 104-first balancing cavity; 103-third balancing cavity. DETAILED DESCRIPTION

[0027] The embodiments of the present application will be described in detail below, and examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0028] In the description of the present application, it is to be understood by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second" can be explicitly or implicitly included one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0029] In the present application, unless otherwise specifically defined and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0030] As Figure 1 shown, the multi-stage vertical molten salt pump of the present application is composed of five stages of impellers, each stage of impeller is installed in series on the pump shaft 5 in the same direction, the axial force balancing device of the multi-stage vertical molten salt pump of the present application can be arranged on one side of a certain stage of impeller or several stages of impeller according to the actual model of the multi-stage pump, generally, an axial force balancing device 8 is arranged between the space guide vane 4 of a certain stage and the corresponding impeller, the axial force balancing device has a third balancing cavity 103 and a first balancing cavity 104, the first balancing cavity 104 is provided with a labyrinth gap between the pressure cavity 101 of the impeller; the third balancing cavity 103 is located inside the space guide vane 4, and the first balancing cavity 104 and the third balancing cavity 103 are provided with elastic damping for balancing the axial force received by the impeller.

[0031] As Figure 2 , Figure 3 and Figure 5As shown, a sliding bearing 20 is provided between the spatial guide vane 4 and the pump shaft 5. The axial force balancing device 8 includes a cylinder, elastic damping, and an adjusting slide plate 11. The cylinder includes an end cap 13 and an outer cylinder wall 14. The end cap 13 is installed at one end of the outer cylinder wall 14. The end cap 13 is located inside the spatial guide vane 4 and is connected to the spatial guide vane 4. A mechanical seal is provided between the sliding bearing 20 and the end cap 13. The other end of the outer cylinder wall 14 is clearance-fitted with the impeller. The adjusting slide plate 11 is located inside the cylinder and is connected to the rear cover plate 9 of the impeller through a fixing module 10. The adjusting slide plate 11 divides the cylinder into a first balancing chamber 104 and a third balancing chamber 103. Elastic damping is provided between the adjusting slide plate 11 and the cylinder. One side of the adjusting slide plate 11, the outer cylinder wall 14, and the rear cover plate 9 constitute the first balancing chamber 104. The area between the other side of the adjusting slide plate 11 and the end cap 13 constitutes the third balancing chamber 103. The end cap 13 is fixedly mounted on the first-stage space guide vane 4 by bolts. The end cap 13 is also fixedly connected to the outer cylinder wall 14 by bolts. A first gap a is provided between the rear cover plate 9 and the space guide vane 4, and a second gap b is provided between the rear cover plate 9 and the outer cylinder wall 14. The first gap a and the second gap b constitute a labyrinth gap between the first balance chamber 104 and the pressure chamber 101 of the impeller. The second gap b is between 0.5 mm and 0.6 mm, and its axial length can change with the axial force. A second balance chamber 102 is provided between the first balance chamber 104 and the pressure chamber 101. The second balance chamber 102 is the area partially enclosed by the space guide vane 4, the cylinder body, and the rear cover plate 9.

[0032] The rear cover plate 9 and the fixing module 10 are connected by a key to synchronize the position changes during the operation of the molten salt pump. The fixing module 10 and the adjusting slide plate 11 are locked in the axial direction but move freely in the radial direction through corresponding concave-convex structures. That is, rotation of the fixing module 10 will not cause rotation of the adjusting slide plate 11, but axial movement of the fixing module 10 will cause axial movement of the adjusting slide plate 11. A spring 12 is installed between the adjusting slide plate 11 and the outer cylinder wall 14. An infrared ranging device 15 is installed on the corresponding surface of the adjusting slide plate 11 and the end cover 13 to monitor the axial force during rotor operation, thereby monitoring the actual operating status of the entire molten salt pump.

[0033] like Figure 4 As shown, a sealing structure 16 is provided between the adjusting slide plate 11 and the inner wall surface of the outer cylinder wall 14. The sealing structure 16 is an annular metal brush. One end of the adjusting slide plate 11 is provided with several spaced grooves, and the annular metal brush is located in the grooves to minimize the leakage of liquid in the first balance chamber 104 to the third balance chamber 103 through the gap.

[0034] The axial force balance principle of the application is to balance the axial force by using the relative low pressure of the pressure cavity 101, the labyrinth gap, the third balance cavity 103 and the bidirectional action of the spring 12 when the pump rotor is subjected to different axial forces, and the specific is:

[0035] The axial force received by the impeller can be mainly divided into two parts, one part is the axial force of the pressure cavity 101 on the upper part of the impeller back cover plate 9, and the other part is the axial force of the first balance cavity 104 on the lower part of the impeller back cover plate, and the former part of the axial force can be balanced with the axial force received by the front cover plate of the impeller, so the stress condition of the lower part of the impeller back cover plate needs to be focused on.

[0036] When the pump rotor is subjected to the right axial force, the fixed module 10 moves to the right synchronously with the impeller, drives the adjusting slide plate 11 to move to the right, and the spring 12 is compressed to generate the left action force. In addition, due to the existence of the first gap a and the second gap b, the high-pressure fluid in the pressure cavity 101 will partially leak into the second balance cavity 102, and the fluid in the second balance cavity 102 will partially leak into the first balance cavity 104. The flow process of the fluid conforms to the law of conservation of mass, when the flow area decreases, the flow rate of the fluid increases, and at the same time, according to Bernoulli equation, the incompressible fluid in the stable flow state will reduce the pressure with the increase of the flow rate to maintain the energy conservation in the flow process. Therefore, under the above action, the pressure of the first balance cavity 104 will always be lower than that of the second balance cavity 102, and the pressure of the second balance cavity 102 will always be lower than that of the pressure cavity 101. Under the action of the two radial gaps, the pressure in the first balance cavity 104 is always at a lower level compared with the pressure cavity 101. For the first balance cavity 104, the axial force received by the lower left side of the impeller back cover plate 9 and the force received by the right side of the adjusting slide plate 11 are offset, and the main source of the axial force in the impeller is converted into the force received by the left side of the adjusting slide plate 11 and the force received by the lower part of the front side of the impeller back cover plate. Since the lower part of the front side of the impeller back cover plate is close to the suction area of the impeller, the suction inlet of the impeller inlet is a low-pressure area, and the axial force of this part of fluid on the structure is small. The left side of the adjusting slide plate 11 is located in the third balance cavity 103, and the fluid in the cavity is partially leaked from the sealing structure 16 and partially seeped from the gap between the lower end of the fixed module 10 and the adjusting slide plate 11. The cavity is basically a static cavity, and due to the mass and energy conservation of the fluid flowing through the sealing and gap, the pressure is always lower than that in the first balance cavity 104. At this time, through the action of the two gaps and the sealing structure, the third balance cavity 103 will maintain a low pressure state, and the axial force received by the lower part of the impeller back cover plate in the right direction will be greatly reduced.

[0037] When the pump rotor is subjected to an axial force to the left, the fixed module 10 and the impeller move to the left, driving the adjusting slide 11 to the left, at which time the spring 12 is stretched, generating a rightward force. The pressure state of the three balance cavities is similar to that when the rotor is subjected to a rightward axial force, but due to the leftward movement of the impeller, the space guide vane 4 and the outer side cylinder wall 14 of the balance device are fixed structures, at this time the axial length of the first gap a and the second gap b is increased respectively, resulting in an increase in the flow resistance when the fluid passes through the gap, thereby causing the pressure difference between the second balance cavity 102 and the pressure cavity 101, and the first balance cavity 104 and the second balance cavity 102 to increase, so that the pressure of the first balance cavity 104 and the second balance cavity 102 is smaller than the pressure of the cavity when the impeller is not subjected to a leftward force, and the force of the liquid on the impeller back cover plate is reduced. At the same time, the existence of the third balance cavity 103 also plays a certain inhibitory role on the leftward movement of the adjusting slide 11 (i.e. the impeller).

[0038] The multi-stage vertical molten salt pump described in the application comprises a plurality of stages of impellers, and the axial force balance device is arranged between at least one impeller and the corresponding space guide vane 4.

[0039] Embodiment

[0040] The designed flow rate of the multi-stage vertical molten salt pump is 950m 3 / h, and the rated rotating speed is 1450r / min. One stage is selected for comparison between the axial force balance device 8 of the application and the model without using the balance means. The operating conditions of 25℃ clear water as the conveying medium under three working conditions of a small flow rate (759m 3 / h), a designed flow rate (950m 3 / h) and a large flow rate (1141m 3 / h) are calculated. The standard k-ε model is used for the turbulent flow model, the total pressure inlet is used for the boundary condition, and the mass flow outlet is used for the boundary condition. The impeller calculation area is a rotating area, the guide vane, the inlet pipe and the outlet pipe are stationary areas, the interface between the moving and stationary calculation areas uses the frozen rotor model, and the wall surface is a smooth wall condition.

[0041] The axial forces of the two under different working conditions are calculated by numerical simulation, and the results are as follows:

[0042] As Figure 6As shown, after installing the axial force balancing device 8, the axial force on the front and rear cover plates of the impeller is significantly reduced, and the amplitude of the axial force on the blade is small. An important source of the axial force of the pump is the asymmetry of the front and rear cover plates of the impeller, that is, the force difference between the two cover plates is the main part of the axial force of the pump. During the process of gradually increasing the flow, the force difference between the cover plates of the impeller with the balancing device is 11503N, 1157.7N, and 1914.5N, respectively, and the force difference between the two cover plates without the balancing measure is 25447N, 15216N, and 10729N, respectively. The force difference between the two cover plates after installing the balancing device is reduced by 54.8%, 92.3%, and 82.2% compared with that without the balancing measure. At the same time, the total axial force is reduced by 40.7%, 56.9%, and 61.5% compared with that without the balancing device. It is shown that the balancing device provided by the present application can effectively reduce the axial force under different working conditions.

[0043] Currently, there are mainly two ways to balance the axial force of a multi-stage pump in engineering, one is a balancing disc, and the other is to combine a sealing ring and a balancing hole. The former can only be installed after the last stage impeller, the position cannot be changed, and a pipeline needs to be connected to the pump inlet. Therefore, the axial force balancing device 8 of the present application is compared with the second one, and the calculation model still uses the single-stage pump model described above. The calculation results are shown in Figure 7 As can be seen, the ability of the axial force balancing device 8 provided by the present application to balance the axial force under different flow conditions is significantly better than that of the traditional balancing measure. Under the conditions of a flow rate of 759m 3 / h, 950m 3 / h, and 1141m 3 / h, the axial force on the device after using the axial force balancing device of the present application is reduced by 24.47%, 44.60%, and 49.42%, respectively, compared with that of the traditional sealing ring and balancing hole structure, and the balancing ability increases with the increase of the flow rate.

[0044] Considering that the axial force balancing device 8 should not have a great impact on the hydraulic performance of the pump, the efficiency, head, and shaft power are the main characteristic parameters for evaluating the performance of the pump. As shown in Figure 8 , the external characteristic parameters of the single-stage pump with the balancing device, without the balancing measure, and with the traditional balancing measure are compared. The influence on the hydraulic performance of the pump under different flow conditions, the head and efficiency of the pump using the balancing device of the present application are similar to those using the traditional balancing measure, and the shaft power is smaller. The greater the head and efficiency, the smaller the shaft power, and the better the performance of the pump. By comprehensively comparing the axial force and hydraulic performance parameters of the pump, the balancing device of the present application provides better balancing of the axial force while having less impact on the performance of the pump. It can be seen that the balancing device has little effect on the hydraulic performance of the pump and can be directly installed on the existing pump without adjusting the hydraulic design, thereby reducing the design cost.

[0045] It should be understood that although the present specification is described in terms of various embodiments, each of which describes only one implementation, the specification is intended to cover all possible combinations for each independent hardware or software characteristic and / or aspect described (or included) therein.

[0046] The foregoing detailed description of various embodiments has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teachings. The described embodiments were chosen in order to best explain the principles of the application and its practical application to thereby enable others skilled in the art to best utilize the application.

Claims

1. A multi-stage vertical molten salt pump axial force balancing device, characterized by, An axial force balancing device is arranged between the space guide vane (4) and the impeller, the axial force balancing device has a third balancing cavity (103) and a first balancing cavity (104), a labyrinth gap is arranged between the first balancing cavity (104) and the pressure cavity (101) of the impeller; the third balancing cavity (103) is located inside the space guide vane (4), and an elastic damping is arranged between the first balancing cavity (104) and the third balancing cavity (103) for balancing the axial force received by the impeller. The axial force balancing device comprises a cylinder, an elastic damping and an adjusting sliding plate (11); the cylinder comprises an end cover (13) and an outer cylinder wall (14), one end of the outer cylinder wall (14) is provided with the end cover (13), the end cover (13) is located inside the space guide vane (4) and connected with the space guide vane (4); the other end of the outer cylinder wall (14) is matched with the impeller gap; the adjusting sliding plate (11) is located inside the cylinder and connected with the back cover plate (9) of the impeller, the adjusting sliding plate (11) divides the cylinder into the first balancing cavity (104) and the third balancing cavity (103), and an elastic damping is arranged between the adjusting sliding plate (11) and the cylinder; one side of the adjusting sliding plate (11), the outer cylinder wall (14) and the back cover plate (9) form the first balancing cavity (104); the region between the other side of the adjusting sliding plate (11) and the end cover (13) forms the third balancing cavity (103).

2. The multi-stage vertical fused salt pump axial force balancing apparatus of claim 1, wherein, A sealing structure (16) is arranged between the adjusting sliding plate (11) and the inner wall of the outer cylinder wall (14).

3. The multi-stage vertical fused salt pump axial force balancing apparatus of claim 2, wherein, The sealing structure (16) is an annular metal brush wire, and the adjusting sliding plate (11) is provided with a plurality of spaced grooves, and the annular metal brush wire is located in the grooves.

4. The multi-stage vertical fused salt pump axial force balancing apparatus of claim 1, wherein, A first gap (a) is arranged between the back cover plate (9) and the space guide vane (4), and a second gap (b) is arranged between the back cover plate (9) and the outer cylinder wall (14), and the first gap (a) and the second gap (b) form the labyrinth gap between the first balancing cavity (104) and the pressure cavity (101).

5. The multi-stage vertical fused salt pump axial force balancing apparatus of claim 1, wherein, The inner wall of the outer cylinder wall (14) is provided with a protrusion, and a spring (12) is arranged between the protrusion and the adjusting sliding plate (11).

6. The multi-stage vertical fused salt pump axial force balancing apparatus of claim 1, wherein, A second balancing cavity (102) is arranged between the first balancing cavity (104) and the pressure cavity (101), and the second balancing cavity (102) is a region partially surrounded by the space guide vane (4), the cylinder and the back cover plate (9).

7. A multi-stage vertical molten salt pump comprising a multi-stage impeller, characterized in that, The axial force balancing device according to any one of claims 1-6 is arranged between at least one impeller and the corresponding space guide vane (4).

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