JP2009156097A - Multi-stage diffuser pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce vibration noises of an entire pump by reducing vibrations noises to a discharging nozzle in a multi-stage diffuser pump. <P>SOLUTION: This multi-stage diffuser pump comprises a multi-stage impeller 5 mounted to a rotary shaft 6, a guide vane 4, a return vane 2, an inner casing 3 covering them, and an outer casing 1 mounted on an outer circumferential side of the inner casing 3 and having an intake nozzle 8 and a discharging nozzle 7. The discharging nozzle 7 is mounted to the outer casing 1 in its axial direction on an upstream of an impeller 5a, a guide vane 4a, and a return vane 2a at the final stage, and mounted in a direction lateral to a circumferential direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for reducing noise in a multistage diffuser pump.

  FIG. 1 shows a cross-sectional view of a multi-stage diffuser pump used in a conventional boiler feed pump. In FIG. 1, five stages including an impeller 5, a guide vane 4, and a return vane 2 attached to the rotating shaft 6 are arranged in the rotating shaft direction, and an inner casing 3 covers the plurality of stages and follows. A structure is shown in which an outer casing 1 including a discharge nozzle 7 and a suction nozzle 8 guides the flow to the stage impeller and covers the inner casing 3.

  In the multistage diffuser pump shown in FIG. 1, a fluid excitation force that is an integral multiple of the product of the number of blades Z of the impeller 5 and the rotational speed N of the impeller 5 vibrates the inner casing 3 and the outer casing 1. However, the outer casing 1 vibrates by the excitation force, and noise is generated by acoustic radiation from the surface. That is, the flow discharged in the centrifugal direction from the edge of the impeller 5 becomes a non-uniform pulsating flow in the circumferential direction due to the influence of the blade thickness, the secondary flow between the blades, etc., but this flow is the guide blade 4 To generate periodic pressure pulsation. This becomes a fluid excitation force, which is transmitted to the inner casing 3 to generate vibration, and this vibration is solid-propagated to the outer casing 1 and emitted from the surface of the outer casing 1 as radiated sound. is there.

  Further, the outer casing 1 is provided with a discharge nozzle 7 and a suction nozzle 8. In these nozzles, both vibration caused by fluid inside the nozzle and vibration due to solid propagation from the outer casing 1 propagate, Due to this vibration, noise is also generated from the nozzle. In general, since the discharge pipe is connected to the discharge nozzle and the suction pipe is connected to the suction nozzle 8 by flange connection, welding or the like, noise is similarly generated from these pipes.

  For example, in the case of a boiler feed pump that is a barrel casing type multistage turbine pump delivered to a thermal power plant, many pipes such as a discharge pipe and a suction pipe are connected to the outer casing 1. Also, auxiliary equipment such as a drive and a transmission is connected to the pump. For this reason, the sound field around the pump is synthesized with noise generated from these pipes and accessories including the pump body. Of these, plant piping such as suction piping, discharge piping, and minimum flow piping, among others, has a large surface area and is stretched in the air, so the sound radiation efficiency is also high, and noise generated from these plant piping. Is considered to have a greater impact on the sound field than the pump body. Therefore, in order to reduce the noise around the pump, it is necessary to reduce the noise from the piping in addition to the pump body.

  In recent years, the above-described multistage diffuser pump is required to reduce noise from the viewpoint of environmental regulations and the pursuit of a comfortable environment, and an invention in that direction has also been made.

  For example, Patent Document 1 discloses a vibration damping device having a hollow portion in which a ring-shaped damping material is sealed in the vicinity of a connection portion between a discharge pipe and a discharge nozzle in a turbo fluid machine, and a cylindrical pipe in which a granular damping material is sealed. A technique for attenuating the propagation of the excitation force from the outer casing to the discharge pipe and the pressure pulsation of the fluid inside the pipe by providing such a propagation attenuating means is disclosed.

  In addition, a method of reducing the noise by increasing the gap between the inlet of the guide vane 4 and the outlet of the impeller 5, and twisting the outlet of the impeller 5 in a three-dimensional skew to alleviate the interference between the two to reduce vibration noise A method for reducing this is also known.

  However, with these methods, a satisfactory effect cannot be obtained in order to reduce the noise around the pump.

Japanese Patent No. 3299638

  In the above prior art, there is a problem that the mass damper damping mechanism such as a ring-shaped damping material is installed, so that the number of parts is increased and the shape of the discharge pipe itself is increased.

  In view of the above problems, the present invention provides a multi-stage diffuser pump that reduces vibration propagation from the casing of the multi-stage diffuser pump to the discharge nozzle, and reduces noise from the surface and piping of the multi-stage diffuser pump. Is the main purpose.

  In order to solve the above problems, a multi-stage diffuser pump according to the present invention includes a multi-stage impeller attached to a rotary shaft, an inner casing that forms a return flow path that guides the flow to the next-stage impeller, and the inner casing A multi-stage diffuser pump that covers the outer peripheral side of the casing and includes an outer casing having a suction nozzle and a discharge nozzle. The discharge nozzle is positioned upstream of the final stage of the multi-stage impeller in the axial direction. It is characterized by having been installed in.

  Moreover, the multistage diffuser pump according to the present invention is characterized in that the discharge nozzle is installed at the same angular position as the base for fixing the outer casing or in the vicinity thereof with respect to the circumferential direction of the outer casing. .

  In the multistage diffuser pump according to the present invention, the discharge nozzle and the base are integrated.

  According to the present invention, by setting the axial position of the discharge nozzle attached to the outer casing to the upstream side of the final stage of the multistage diffuser, fluid excitation force due to separation at the corner of the discharge nozzle, erosion due to cavitation, etc. are caused. Reduce the risk and improve the fluid performance of the pump.

  Furthermore, since the circumferential position of the discharge nozzle can be set in the same direction as the base for fixing the casing, vibration propagation to the discharge nozzle can be reduced, and vibration noise from the multistage diffuser pump and piping can be reduced. .

  The inventor of the present invention has studied the mechanism of vibration noise generation from the excitation force to the vibration / noise propagation path and the noise radiation, and has obtained the best mode for carrying out the present invention. Examples thereof will be described below.

  FIG. 2 is a sectional view of the multistage diffuser pump according to the first embodiment of the present invention. In the first embodiment, as shown in FIG. 2, five stages including an impeller 5, a guide vane 4 and a return vane 2 attached to the rotary shaft 6 are arranged in the axial direction. Further, in the multistage diffuser pump having a structure in which the inner casing 3 is covered with the outer casing 1 having the discharge nozzle 7 and the suction nozzle 8, the discharge nozzle 7 is the last stage blade with respect to the rotation axis direction. The vehicle 5a, the guide vane 4a, and the return vane 2a are attached upstream. Thereby, the swirling secondary flow generated in the inner casing 3 is bent so that the fluid flows to the discharge nozzle 7.

  3 is an enlarged view of the vicinity of the final stage of the conventional multistage diffuser pump shown in FIG. 1, and FIG. 4 is an enlarged view of the vicinity of the final stage of the multistage diffuser pump according to the present invention. Black arrows indicate fluid flow. In the conventional structure shown in FIG. 3, the flow that flows out from the guide blade 4a at the final stage is very high speed, and as shown by the black arrow, a high-speed flow in only one direction is generated as compared with the surrounding flow. In such a case, the high-speed flow may cause separation near the corner of the discharge nozzle 7, which may increase unsteady fluid excitation force that causes noise or cause cavitation. . In addition, this can cause erosion or damage to the material.

  On the other hand, in the multi-stage diffuser pump according to the present invention shown in FIG. 4, the flow from the guide blade 5a at the final stage is bent as indicated by the black arrow and is rectified to some extent to the discharge nozzle 7. Flowing. That is, by decelerating the high-speed flow from the final stage by bending the flow path and reducing the non-uniformity of the flow velocity distribution, the fluid excitation force accompanying separation in the conventional example that flows directly to the discharge nozzle 7 is reduced. Since the risk of occurrence and cavitation can be reduced, the fluid performance of the pump can be improved.

  Also, as shown in FIGS. 2 and 4, by bringing the discharge nozzle 7 upstream from the final stage, the degree of freedom of the mounting angle position of the discharge nozzle 7 in the circumferential direction of the outer casing 1 is improved. . FIG. 5 shows a schematic side view of a conventional multi-stage diffuser pump. As shown in FIG. 5, since there is a fixing base 9 at the position of the conventional discharge nozzle, the discharge nozzle 7 is at least fixed. There was a restriction that it must be installed avoiding the base 9 position.

  In contrast, as shown in the schematic side view of the multi-stage diffuser pump according to the first embodiment of the present invention in FIG. 6, in the pump of the present invention, the discharge nozzle position is located upstream of the final stage. Without interfering with the two bases 9, it can be attached at any position in the circumferential direction between them. Therefore, the mounting angle of the discharge nozzle 7 can be optimally changed according to the situation around the pump.

  FIG. 7: shows the schematic side view of the multistage diffuser pump of Example 2 of this invention. In the second embodiment, the position of the discharge nozzle is attached to the side, that is, the angular position of the base in the first embodiment. FIG. 8 is a schematic front view of the multistage diffuser pump according to the second embodiment, and is a view seen in the axial direction from the discharge nozzle side in FIG. 7.

  FIG. 9 exaggerates the vibration mode when the outer casing 1 of the multistage diffuser pump is fixed at the position of the base 9. In the multistage diffuser pump fixed at the position of the base 9 shown in FIG. 9, the inventor of the present invention has a mode in which the position of the base 9 of the outer casing 1 is a node and the top and bottom are antinodes, that is, the position of the base 9 It has been found that it vibrates in a mode that expands and contracts in the vertical direction with as a node.

  In the present invention, by disposing the discharge nozzle 7 from the upward direction to the lateral direction, the discharge nozzle 7 can be attached at the site where vibration is smallest, so that vibration propagation to the discharge nozzle 7 can be reduced. . Further, by integrating the discharge nozzle 7 and the base 9, the rigidity of the entire pump can be improved, and vibration of the entire pump can be reduced. Therefore, the vibration noise of the pump body can be reduced, and the vibration noise from the discharge nozzle 7 to the pipe attached first can be reduced.

  FIG. 10 shows an analysis model of a conventional multistage diffuser pump, and FIG. 11 shows an analysis model using the second embodiment of the present invention. In the model of the conventional structure, the discharge nozzle 7 is at the top, the discharge pipe 10 is connected to the tip, and the bend is used once in the middle. On the other hand, in the model of the second embodiment, the discharge nozzle 7 is horizontally horizontal, the discharge pipe 10 is connected to the tip, and the discharge pipe 10 is horizontally bent so that it is bent twice. .

  Vibration analysis was performed on the models shown in FIGS. As a constraint condition, the position of the base 9 and the end of the discharge pipe are fixed. In the analysis model of the conventional pump and the analysis model of the pump of the present invention, the same amplitude was given to the discharge pipe 10 as the input excitation force, and the amplitude corresponding to the input was output. Based on the result, if the amplitude AO of the discharge pipe with respect to the amplitude AI of the excitation force, that is, AO / AI is compared, the effect of reducing the pipe vibration can be calculated.

  FIG. 12 is a logarithmic display of the above-mentioned AO / AI converted into sound pressure, and shows the noise level difference between the model of the conventional example and the model of the present invention, that is, the noise reduction effect. FIG. 12 shows that the noise from the pipe is reduced by about 7 dB by using the model of the present invention.

  In the conventional example, the horizontal portion of the discharge pipe 10 is vibrated in the same vertical direction, that is, in the radial direction due to the vertical vibration shown in FIG. It is thought that it was. On the other hand, in the present invention, since the discharge nozzle 7 is attached to the node portion of the mode of FIG. 9, the vibration direction to the discharge nozzle 7 is horizontal, and the horizontal portion of the discharge pipe 10 is horizontal. Since the sound is oscillated, the sound emission direction and the vibration direction are shifted by 90 degrees, so that it is difficult to produce sound, and as a result, the noise generated from the pipe can be reduced.

  In the second embodiment, the discharge nozzle 7 and the base 9 have the same direction. However, the discharge nozzle 7 and the base 9 may be installed in the vicinity of the discharge nozzle 7 and have the same direction.

  In the second embodiment, only the discharge nozzle 7 has the same direction as the base 9, but the suction nozzle 8 may also be attached in the same direction as the base 9 or in the vicinity thereof so as not to interfere with the base. Further, the direction of the discharge nozzle 7 and the suction nozzle 8 may be the same direction or an angular position in the opposite direction of 180 degrees, or may be a position near the position.

  Furthermore, it is desirable that the discharge nozzle 7 is in the same direction as the base 9 with respect to the circumferential direction of the outer casing 1, that is, the center of the discharge nozzle 7 is preferably flush with the base 9. If it is difficult to do so due to restrictions, a certain angle, for example, 15 degrees, 30 degrees, etc. may be provided between the mounting angle position of the discharge nozzle 7 and the mounting angle position of the base 9. Good.

  As described above, according to the present invention, in the multi-stage diffuser pump, the installation position of the discharge nozzle 7 is installed on the upstream side of the final stage, so that fluid excitation force due to separation at the corner portion of the discharge nozzle, erosion due to cavitation, etc. It is possible to improve the fluid performance of the pump to reduce the risk of causing it.

  Furthermore, since the interference with the base 9 can be avoided with respect to the mounting angle position of the discharge nozzle 7, the degree of freedom of the mounting position is increased, and it can be mounted not only in the upward direction but also in any position such as the lateral direction and the downward direction. It becomes.

  Furthermore, by setting the circumferential position of the mounting position of the discharge nozzle 7 in the same direction as the base 9 for fixing the casing, that is, laterally, the vibration propagation to the discharge nozzle 7 is further reduced, and the multistage diffuser Vibration noise from the pump and the discharge pipe 10 can be further reduced.

Sectional drawing of the conventional multistage diffuser pump. Sectional drawing of the multistage diffuser pump of Example 1 of this invention. The enlarged view of the last stage vicinity of the conventional multistage diffuser pump. The enlarged view of the last stage vicinity of the multistage diffuser pump of Example 1 of this invention. The schematic side view of the conventional multistage diffuser pump. 1 is a schematic side view of a multistage diffuser pump according to a first embodiment of the present invention. The schematic side view of the multistage diffuser pump of Example 2 of this invention. The schematic front view of the multistage diffuser pump of Example 2 of this invention. The vibration mode figure of a multistage diffuser pump. The analysis model figure of the conventional multistage diffuser pump. The analysis model figure of Example 2 of this invention. The figure which shows the noise reduction effect in the multistage diffuser pump analysis model by Example 2 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Outer casing, 2 ... Return vane, 3 ... Inner casing, 4 ... Guide vane, 5 ... Impeller, 6 ... Rotating shaft, 7 ... Discharge nozzle, 8 ... Suction nozzle, 9 ... Base, 10 ... Discharge piping

Claims (3)

A multi-stage impeller attached to the rotary shaft; an inner casing that forms a return flow path that guides the flow to the next-stage impeller; and an outer peripheral side of the inner casing that covers the suction nozzle and the discharge nozzle. In a multistage diffuser pump with an outer casing having
The multistage diffuser pump, wherein the discharge nozzle is installed at a position upstream in the axial direction from the final stage of the multistage impeller. The multistage diffuser pump according to claim 1,
The multi-stage diffuser pump, wherein the discharge nozzle is installed at the same angular position as the base for fixing the outer casing or in the vicinity thereof with respect to the circumferential direction of the outer casing. The multi-stage diffuser pump according to claim 2,
A multi-stage diffuser pump, wherein the discharge nozzle and the base are integrated.

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