JP2010031738A - Pump with impeller made from sheet metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an impeller made from a sheet metal capable of improving a blade molding property of the impeller achieving high performance and balancing strength reliability and welding property of the impeller at the same time. <P>SOLUTION: In the pump provided with a rotation shaft, the impeller made from the sheet metal consisting of hub mounted to the rotation shaft and blades arranged for an outer circumference of this hub, a suction casing for introducing fluid to the impeller and a discharge casing consisting of an outer circumferential discharge casing and an inner circumferential discharge for introducing the fluid discharged from the impeller, the impeller is structured as follows; the blades of the impeller are separated in a direction from an impeller inlet to an outlet and suction side blades of the separated blades are molded by mold-bending and discharge side blades of the separated blades are defined in a perfect two-dimensional form and molded by linear bending with a roll and the blades are respectively arranged to a hub at its sucking side and discharge side in tandem and welded. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pump that is one of fluid machines, and more particularly to a pump having a sheet metal impeller such as a sheet metal that achieves high performance while maintaining strength reliability and manufacturability.

  Pumps, which are examples of fluid machinery, are used for large-capacity cooling water circulation pumps, desalination pumps, feed and drainage pumps for power plants and plants.

  Regarding the conventional pump, a mixed flow pump is taken up, and the structure thereof will be described below with reference to FIGS. FIG. 8 is a cross-sectional view of a peripheral portion of a closed type impeller having a shroud 13 on the impeller 1 in a conventional mixed flow pump. FIG. 9 is a cross-sectional view of a peripheral portion of an open type impeller having no shroud in the impeller of a conventional mixed flow pump.

  The conventional mixed flow pump includes an impeller 1 including a rotating shaft 10, a hub 12 attached to the rotating shaft 10, and blades 11 provided on the outer periphery of the hub 12, and suction for guiding fluid to the impeller 1. The casing 2 includes a discharge casing 3 including an outer peripheral discharge casing 31 and an inner peripheral discharge casing 32 that guide the fluid discharged from the impeller 1.

  Among these, the structure of the blade 11 will be described. FIG. 10 is a view of the blade shape of a conventional mixed flow pump as viewed from the suction side in the direction of the impeller rotation axis, and shows two adjacent blades. In the blade shown in FIG. 10, when viewed from the impeller rotation axis direction, the blade 101 that precedes the blade rotation direction and the blade 102 that follows are partially overlapped to form an inter-blade channel 103. Yes. Among these, the boundary line 104 on the blade leading edge side is defined in the inter-blade channel portion of the preceding blade 101. Further, a boundary line 105 on the trailing edge side of the blade is defined in the inter-blade channel portion of the trailing blade 102. With these two boundary lines 104 and 105, the blade is divided into three regions. This is classified into a suction side blade 106, a discharge side blade 108, and 107, which is an intermediate region between them, and is shown in FIG.

  FIG. 12 is a perspective view of the blade of FIG. 11 viewed from one direction on the blade tip side. As shown in FIG. 11, the discharge-side blades 108 appear to overlap substantially in the span direction from the hub 12 to the outermost peripheral surface (blade tip) 109 of the blades, and have a two-dimensional shape. On the other hand, the suction side blade 106 has a warped shape to improve the efficiency of the flowing water portion of the blade and the cavitation performance, and has a three-dimensional free-form surface shape.

  Since the suction-side blade 106 has a three-dimensional free-form surface shape, conventionally, the entire blade is formed by casting, or the blade is made of sheet metal and formed by pressing with a three-dimensional total mold (canned structure impeller). It was.

  However, in the manufacture of the impeller blades by the conventional casting described above, there are problems that the manufacturing cost for making the wooden mold is high and the manufacturing period of the wooden mold is long. On the other hand, in the conventional impeller blade made of sheet metal by press working, there is a problem that the fluid machine cannot be manufactured at low cost because the production cost of the three-dimensional total mold is high. In addition, a large press machine was required to form large blades of stainless steel with high hardness.

  In order to overcome this problem, as disclosed in Patent Document 1, the blade surface is approximated as a part of a cylinder or a cone, and an impeller made of sheet metal is formed relatively easily, thereby reducing costs. is there.

  Further, when the impeller is made of sheet metal and the blade and the hub are welded, the strength of the root portion of the blade cannot be ensured as compared to the case where the blade and the hub are manufactured integrally as in the case of a cast impeller. Therefore, in the case of an open type impeller without the shroud 13 in the blade tip 109, the strength against the bending stress of the blade caused by changing the fluid flow direction in the vicinity of the blade leading edge becomes a problem. On the other hand, in the case of a closed type impeller in which the blade tip 109 has the shroud 13, the shroud 131 near the blade outlet side receives a force due to the moving and stationary blade interference between the guide blade 5 and the blade 11 in FIG. Therefore, the strength against the interference fluctuation stress becomes a problem. In order to maintain the blade strength, it is necessary to use a plate material with a large blade thickness, so that it is necessary to increase the blade weight, deteriorate the blade moldability, increase the welding amount, etc., resulting in an increase in manufacturing cost. There was a problem.

  Among these problems, in order to overcome the problem concerning the bending stress of the blade leading edge in particular, as described in Patent Document 2, the shroud of the impeller for the compressor is moved from the blade leading edge on each blade tip side to the trailing edge. There is an example in which the impeller is reinforced by attaching to the middle part.

JP 2002-147390 A JP 2004-353607 A

  However, in the blade manufacturing method described in Patent Document 1, when the three-dimensionality of the free curved surface shape of the suction side blade 3 becomes strong, the blade shape approximated as a part of a cylinder or a cone deviates from the desired blade shape. There was a problem.

  In addition, as described in the embodiment of Patent Document 2, there is an example in which a shroud is partially attached to an impeller of a compressor, but cavitation that occurs near the leading edge of the blade, which is a problem peculiar to the pump. There was a problem that the shroud mounting method considering the above was not mentioned.

  An object of the present invention is to provide a pump capable of improving the blade formability for achieving high performance in a sheet metal impeller and at the same time satisfying the strength reliability of the impeller, weldability, and cavitation performance. There is.

  In order to achieve the above-mentioned object, a pump according to the present invention includes a rotating shaft, a hub mounted on the rotating shaft, and a sheet metal impeller comprising blades provided on the outer periphery of the hub, and a fluid in the impeller. In a pump comprising a suction casing for guiding the fluid discharged from the impeller, and a discharge casing composed of an outer peripheral discharge casing and an inner peripheral discharge casing for guiding the fluid discharged from the impeller, the impeller blade is moved in a direction from the impeller inlet to the outlet. The suction side blade which is divided into two and has a three-dimensional free-form surface in order to improve the flowing water efficiency and cavitation performance of the two divided blades is press-molded by a die (hereinafter referred to as mold bending). Of the two divided blades, the discharge-side blade having a relatively two-dimensional shape is defined as a complete two-dimensional shape, and the hub and shuffle are defined at each position in the flow direction of the blade. Define a straight bend line connecting the Udo and form it by wire bending (hereinafter referred to as wire bending) in which a sheet metal is sequentially bent by a roll to form a curved surface. Installed in tandem and welded.

  Further, a portion of the tip side of the suction side blade of the two divided blades and the tip side of the discharge side blade of the two divided blades are substantially conical on the upstream side in the direction from the impeller inlet to the outlet. It is characterized in that it is constructed by covering and welding with a sheet metal shroud expanded in a shape, and arranging a liner in a portion without the shroud to form a narrow gap between the blade blade tips. The shroud is a cylindrical member, and an impeller ring portion that slides the casing is formed on an outer peripheral portion of the cylindrical portion.

  According to the pump of the present invention, it is possible to improve the blade formability of an impeller that achieves high performance in a sheet metal impeller, and at the same time, it is possible to achieve both strength reliability, weldability, and cavitation performance of the impeller.

  Hereinafter, a first embodiment of a pump to which the present invention is applied will be described with reference to FIGS.

  FIG. 1 is a cross-sectional view showing a schematic configuration of an example of a pump to which the present invention is applied. FIG. 2 is a view of the impeller blade 11 in the present embodiment as viewed from the rotation axis direction suction side. The pump of the present embodiment includes a rotating shaft 10, an impeller 1, a suction casing 2, and a discharge casing 3 including an outer peripheral discharge casing 31 and an inner peripheral discharge casing 32. The impeller 1 is formed of sheet metal. Moreover, the suction casing 2 and the discharge casing 3 may be formed of a casting or may be formed of a sheet metal.

  The rotary shaft 10 extends from the suction casing 2 side to the discharge casing 3 side, and is rotatably supported by a thrust bearing and a radial bearing (not shown). The impeller 1 is attached to the rotating shaft 10 and rotated together with the rotating shaft 10 to give energy to the working fluid (in this embodiment, water). The impeller 1 includes a hub 12 that is expanded in a substantially conical shape, and a plurality of blades 2 that are provided obliquely on the outer peripheral surface of the cone of the hub 12.

  In this embodiment, the blade shape is configured to reproduce the same performance as the cast product. Here, the conventional example of FIGS. 10 and 11 is used as the shape of the cast impeller, and the features of the blades of the example will be described based on FIG. 2 in comparison with this.

  In this embodiment, the blades are formed of sheet metal, only the suction side blade portion 106 having a three-dimensional free-form surface shape having a large influence on performance is formed by mold bending, and the discharge side blade 108 having a two-dimensional shape is formed by a roll. It is defined as a complete two-dimensional shape by bending, a straight bending line 110 connecting the hub and the shroud is defined at each position in the flow direction of the blade, and the sheet metal is sequentially bent by a roll to form a curved surface. . As a result, a performance equivalent to that of a cast impeller can be obtained without pressing with a three-dimensional total mold. Further, the wire bending by the roll does not require a large press, which leads to cost reduction.

  In order to further reduce the cost, it is necessary to extend the region of the wire bending blade 108 defined by the complete two-dimensional shape as much as possible to the suction side. However, as the region of the wire bending blade 108 is extended to the suction side, the shape of the wire bending forming blade and the shape of the die bending forming blade are formed in the vicinity of the intermediate region 107 shown in FIG. The discontinuity becomes stronger, and the distribution of the blade angle β of the blade 11 shown in FIG. 3 with respect to the winding angle θ becomes discontinuous as shown in FIG. In the shape discontinuous region, molding by wire bending becomes difficult, and it must be mold bending. As a result, the cost increases. FIG. 4 shows the blade angle β due to the discontinuity of the shape of the blade for wire bending and the blade for mold bending when the region of the blade for wire bending is extended to the impeller suction side. It is a figure explaining the discontinuity of distribution with respect to the winding angle θ.

  Therefore, as shown in FIG. 2, in this embodiment, the blade is divided into two in the direction from the impeller inlet to the outlet. Of the two divided blades, the suction side blade 106 is formed by mold bending, and the discharge side blade 108 is formed by linear bending. Then, the two divided blades 106 and 108 are arranged in tandem (vertically arranged) on the suction side and the discharge side of the hub 12 with the intermediate region 107 removed (space region) and welded.

  When the blades are formed of sheet metal, the following effects are produced by making the blades into a divided structure. That is, the suction-side blade 106 that serves as a mold bend and the discharge-side blade 107 that serves as a wire bend can be formed independently, so that the process can be shortened by parallel forming. Further, only the suction side blade 106 whose size is reduced by the division requires a press working die, so that the capacity of the press machine can be reduced. In addition, it is possible to remove the shape discontinuity of the intermediate region 107, which is inevitable when the blade is formed from a single sheet metal. Accordingly, the line bending region of the discharge side blade 108 can be extended to the suction side, and the die for press working can be made the minimum size.

  Furthermore, when both mold bending and line bending are performed on a blade having an undivided structure, bending is performed in order. However, when bending is performed later, deformation occurs in an already bent region. However, if the blade is divided, the problem of this deformation is eliminated. In addition, the discontinuity of the shape in the intermediate region 107 is removed, and the fluid flows between the suction side blade 106 and the discharge side blade 108 without being restricted by the blade. In such a flow field, the fluid tends to flow more smoothly between the outlet of the suction-side blade 106 and the inlet of the discharge-side blade 108 than when the blade is constrained, which adversely affects the fluid performance. You can also prevent.

  Cavitation performance equivalent to that of a cast impeller can be realized by dividing the blades and welding each to the hub, but the blade number ratio between the suction side blades 106 and the discharge side blades 108 can be freely set. This makes it possible to improve pump cavitation performance. In this embodiment, in order to increase the flow passage area on the impeller suction side with the aim of improving cavitation performance, if the number of blades of the suction side blades 106 is set smaller than the number of blades of the discharge side blades 108 as shown in FIG. The flow path area on the impeller suction side can be widened. Here, if the number of the suction side blades 106 is half the number of the discharge side blades 108, the relative positional relationship between the two in the circumferential direction is the same for all the blades. This is desirable because it minimizes the property.

  In addition, since the blades are divided and each is welded to the hub 12, it is possible to freely set the circumferential relative positional relationship between them. In FIG. 5, the circumferential relative position between the suction-side blade 106 and the discharge-side blade 108 is not changed, but the circumferential relative position is set as necessary in consideration of the efficiency and cavitation performance of the impeller. good.

  Although the mixed flow pump has been described as an example in the drawings described in the present embodiment, the form of the pump is not limited to the mixed flow pump and can be used for other forms of pumps.

  A second embodiment of the present invention will be described below with reference to FIGS. FIG. 6 is a sectional view showing a schematic configuration of a pump to which the present invention is applied. FIG. 7 is a diagram illustrating a configuration example of the blade tip side shroud of FIG. 6.

  The difference between the present embodiment and the first embodiment is that the entire tip 109 of the suction side blade 106 and the tip 109 of the discharge side blade 108 are directed from the inlet to the outlet of the impeller 1 as shown in FIG. A part of the upstream side in the direction is covered with a shroud 13 expanded in a conical shape and welded. A portion 14 having no shroud in the tip of the discharge-side blade is configured by disposing the liner 4 and forming a narrow gap with the blade blade tip. As shown in FIG. 6, the suction side portion of the sheet metal shroud 13 has a shape parallel to the impeller rotating shaft 10. Further, in order to smoothly turn the fluid flowing from the suction port along the impeller rotating shaft 10 in the oblique radial direction, the portion having the same inclination as the blade tip portion of the shroud 13 is connected to the suction side portion. The middle part of the shroud 13 has a curved surface shape. A seal portion 6 for suppressing leakage from the back surface of the shroud 13 is provided at the tip.

  Here, when the plate thickness of the shroud 13 is relatively thick, as shown in FIG. 6, the end shape in the flow direction of the shroud 13 is cut in advance so as to be parallel to the impeller rotating shaft 10. It is good to give. Then, by shaping the shape of the liner 4 in accordance with the shape of the end portion of the shroud 13 in the flow direction, leakage toward the back surface of the shroud 13 can be reduced, and at the same time, when the pump is assembled, the liner 4 is halved. Even if it is not structured, it can be assembled from the impeller shaft direction.

  The shroud 13 may be configured as shown in FIG. 7 because the intermediate portion has a curved surface shape and poor moldability. That is, the shroud 13 is a cylindrical member, an impeller ring portion 132 that slides with the casing is formed on the outer peripheral portion of the cylinder, and a lathe intermediate portion in FIG. Form the curvature. This cylindrical member may be an integral sheet metal, or cylindrical members made of different materials may be laminated and welded. Then, the blade tip and the cylindrical shroud are welded so that the outlet end of the inner peripheral portion of the cylindrical shroud matches the end position in the flow direction of the closed impeller portion shown in FIG.

  As described above, the following effects can be obtained by attaching the shroud 13.

  First, since the entire tip 109 of the suction side blade 106 of the impeller 1 is covered with the shroud 13 and welded, the space between the tips of the suction side blades 106 is reinforced by the shroud 13, so there is a problem with the open type impeller. The strength against the bending stress of the blade generated by changing the fluid flow direction in the vicinity of the blade leading edge increases.

  Next, the arrangement location of the shroud 13 on the discharge side blade 108 is not limited to the entire region on the tip 109 side of the discharge side blade 108, but is limited to a part on the upstream side in the direction from the inlet to the outlet of the impeller 1. You can get the following effects.

  In the open type impeller, the flow is disturbed by the leakage flow flowing through the gap between the front edge side of the blade tip 109 and the liner 4, and the velocity shear layer of the leakage flow is generated to generate a vortex near the tip. Cavitation is likely to occur because pressure loss occurs in the region where the flow is disturbed, and static pressure decreases at the center of the vortex. Here, the vicinity of the leading edge of the blade, where the pressure increasing action by the blade is not sufficient, is the portion where the cavitation is most likely to occur in the impeller 1.

  In the present embodiment, since the suction side blade 106 is a closed type, cavitation is most likely to occur in an open type impeller, and the occurrence of cavitation due to leakage flow between the suction tip blade tip 109 and the liner 4 is prevented. It becomes possible to suppress. Further, in this embodiment, in addition to the entire tip of the suction side blade 106, the shroud 13 is extended to a part of the tip 109 of the discharge side blade 108 on the upstream side in the direction from the inlet to the outlet of the impeller 1. By covering, the wall surface of the discharge-side blade 108 facing the tip 109 changes from a stationary wall surface to a rotating wall that rotates together with the impeller. When the wall surface facing the blade tip 109 is a stationary wall, the flow velocity on the stationary wall surface is zero. On the other hand, the fluid on the blade tip 109 has a speed equal to the impeller rotational speed due to the influence of viscosity. Furthermore, the fluid between the two wall surfaces is subjected to a force in the direction opposite to the impeller rotation direction due to the pressure gradient between the pressure surface and the suction surface of the blade.

  Accordingly, when viewed from the stationary coordinate system, the flow velocity distribution of the flow in the gap is zero on the stationary wall surface, and is convex between the stationary wall and the blade tip 109 wall surface in the direction opposite to the rotation direction of the impeller, and the blade tip 109 Above, it becomes equal to the impeller rotational speed. In this case, since the velocity gradient in the gap height direction becomes large, the vortex strength generated by the velocity shear layer of the leakage flow is strong and cavitation is likely to occur. On the other hand, when the shroud 13 is extended to the upstream side of the discharge-side blade 108 and the wall surface facing the blade tip 109 is a rotating wall, the flow in the gap between the blade tip 10 on the leading edge side of the discharge-side blade 108 and the liner 4. The field also becomes a flow field of a rotating coordinate system that rotates with the impeller.

  At this time, the driving force of the leakage flow is only the pressure gradient between the blade pressure surface and the suction surface, so the flow velocity distribution of the flow in the gap is the blade tip when viewed from the rotating coordinate system that rotates with the impeller. 109 is 0 on the wall surface and the opposite wall surface, and in the meantime, it is convex in the direction opposite to the impeller rotation direction. Since the magnitude of the velocity shear of the leakage flow is smaller than the case where the wall surface facing the blade tip 109 is a stationary wall, the leakage vortex is weakened. Therefore, it is also possible to suppress the occurrence of cavitation due to the leakage flow in the gap between the blade tip 109 and the liner 4 on the leading edge side of the discharge blade 108 that has not yet been sufficiently pressurized.

  In addition, in this embodiment, the cavitation performance is improved, and at the same time, the blade is caused by the moving and stationary blade interference between the guide blade 5 and the discharge-side blade 108, which is a problem in a completely closed type impeller in which the entire tip of the blade is covered with a shroud. Interference fluctuation stress caused by repeated deformation of the shroud near the exit side in the blade height direction can be reduced. Further, compared with a completely closed type impeller, the disc frictional power acting on the shroud can be reduced, so that the efficiency is improved. Furthermore, since the space where the welding machine enters can be secured by providing the portion without the shroud 13, the welding workability between the blades 106 and 108 and the hub 12 can be improved. Thereby, complete penetration welding is possible in the entire region between the blade and the hub, and the strength of the blade is increased.

  Further, the shroud 13 is a cylindrical member, and an impeller ring portion 132 that slides with the casing is formed on the outer peripheral portion of the cylinder, and an intermediate portion of the shroud in FIG. The following effects are born by forming the curvature of. First, the formability of the curved shape of the intermediate portion of the shroud 13 is improved as compared with the case of forming by press working. The curvature of the middle part of the shroud has a large effect on the performance of centrifugal and mixed flow impellers with large turning in the oblique radial direction from the impeller inlet to the discharge side. Required. Since the curved surface shape of the shroud intermediate portion is uniform in the circumferential direction, lathe machining is easy, and the lathe machining makes it easy to obtain the accuracy of the curved surface shape. Further, since the curvature is created by lathe processing on the simple inner peripheral surface of the cylindrical member, the processing becomes simple. Furthermore, if this cylindrical member is made by laminating and welding cylindrical members made of different materials and using a soft member suitable for sliding only on the impeller ring portion 132 on the outer peripheral side, the hardness difference between the shroud 13 and the impeller ring portion 132 is reduced. It can be secured. By carrying out like this, the lifetime and maintainability of the seal part 6 can be improved.

Sectional drawing which shows schematic structure of the pump in Example 1 of this invention. Explanatory drawing which looked at the impeller blade from the rotation-axis direction suction side similarly. Similarly explanatory drawing of blade angle (beta) and winding angle (theta). Similarly, the figure explaining the discontinuity of distribution with respect to the winding angle θ of the blade angle β. Explanatory drawing when the number of suction side blades is similarly configured to be smaller than the number of discharge side blades. Sectional drawing which shows schematic structure of the pump in Example 2 of this invention. Explanatory drawing of the structural example of the shroud of FIG. 6 similarly. Sectional drawing of the pump which has the conventional closed type impeller. Sectional drawing of the pump which has the conventional open type impeller. The figure which looked at the blade | wing shape of the conventional impeller from the impeller rotation-axis direction suction side. Explanatory drawing which classified the blade | wing of FIG. 10 into three area | regions. The perspective view which looked at the blade | wing of FIG. 11 from one direction with a blade | tip chip | tip side.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Impeller, 10 ... Rotating shaft, 11 ... Blade, 101 ... Leading blade, 102 ... Trailing blade, 103 ... Flow path between blades, 104 ... Blade leading edge side boundary line, 105 ... Blade trailing edge side boundary line, 106 ... Suction side blade, 107 ... middle region, 108 ... discharge side blade, 109 ... tip, 110 ... bending line, 12 ... hub, 13 ... shroud, 131 ... shroud near blade outlet of closed impeller, 132 ... impeller ring part, 2 DESCRIPTION OF SYMBOLS ... Suction casing, 3 ... Discharge casing, 31 ... Outer periphery discharge casing, 32 ... Inner periphery discharge casing, 4 ... Liner, 5 ... Guide blade, 6 ... Seal part.

Claims (3)

A rotating shaft, a hub mounted on the rotating shaft, and a sheet metal impeller comprising blades provided on the outer periphery of the hub, a suction casing for guiding fluid to the impeller, and fluid discharged from the impeller In a pump provided with a discharge casing composed of a leading outer discharge casing and an inner discharge casing,
The blade provided in the impeller is divided into a suction side blade and a discharge side blade, the suction side blade is formed by mold bending, and the discharge side blade is defined by a two-dimensional shape and formed by wire bending by a roll. The suction blade and the discharge blade are arranged in tandem and fixed on the suction and discharge sides of the hub, respectively.   2. The pump according to claim 1, an upstream side in a direction from an impeller inlet to an outlet, out of an entire tip side of a suction side blade of the two divided blades and a tip side of a discharge side blade of the two divided blades. A part of this was covered with a sheet metal shroud expanded in a substantially conical shape and welded, and a liner was placed on the part without the shroud to form a narrow gap with the blade blade tip. A pump having an impeller made of sheet metal.   The pump according to claim 2, wherein the shroud is a cylindrical member, and an impeller ring portion that slides the casing is formed on an outer peripheral portion of the cylindrical portion.

Images