JPH01178800A - Flat-plate type straight inducer for pump - Google Patents

Abstract

PURPOSE:To simplify the manufacturing process of and improve the erosion resistance of the inducer in the caption by using an approximate fan-shaped flat plate to form an inducer vane whose surface is flat, and setting a patch made of a erosion-resistant material in an important position on the vane surface of the inducer. CONSTITUTION:An inducer vane 3 is made of a flat plate which is blanked out in an approximate fan shape, and connected to an inducer shaft 4 by welding without any three dimensional machining. That is, the inducer vane is fixed to the inducer shaft in such a condition that a predetermined datum line 5 which passes through the pivot 0 for the fan is kept at right angles to the center of the inducer shaft 4, and the vane surface is inclined at a predetermined angle alpha in relation to the center of the inducer shaft 4. And also, a patch 5 made of a erosion-resistant material is set in an important position on the surface of each inducer vane 6.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a flat linear inducer for a pump that requires high suction performance.

(Prior Art) Conventionally, in pumps that require high suction performance, an inducer is placed in front of the main impeller. This inducer increases the pressure of the fluid before it is sucked into the main impeller, suppresses the occurrence of gear pitage, and improves suction performance. This inducer is of the axial flow type, and helical inducer blades are often used, and its shape is determined by numerous design factors such as the number of blades, outer diameter, solidity, hub ratio 1 blade population angle, blade exit angle, etc. Determined by.

Here, the blade inlet angle and the blade exit angle of the inducer blade are determined by a geometric method using a velocity triangle assuming collision-free inflow.

For example, the blade inlet angle β1 with an arbitrary radius of 2 at the blade inlet
is determined from the following equation.

rltanβ, = r+ttanβ1t, where r
, Arbitrary radius rat: Inducer tip diameter β1t, inducer dip angle, and blade angle constant from inlet to outlet, such as a flat plate helical inducer, or one with camber, etc. is used. There is.

On the other hand, in order to improve the cavitation erosion resistance and sand erosion resistance of this inducer itself, conventionally, erosion resistant materials such as stainless steel were used for the inducer blades, and stellite was used on the surface of the inducer blades. It is also practiced to fill the feed with a plate made of corrosion-resistant feed.

(Problem to be solved by the invention) However, since conventional inducer blades have a three-dimensional blade shape, when manufacturing them, cast ones have a complicated blade shape, whereas welded ones have a complicated blade shape. The use of press molds, etc. was unavoidable, and the manufacturing process was complicated and required a large number of man-hours. In addition, welded products have large manufacturing errors during press forming and welding, and it is difficult to control the design angle distribution, so the reproducibility of hydraulic performance cannot be said to be good.

Furthermore, when applying erosion-resistant build-up to the three-dimensionally curved inducer blade, in order to obtain good hydraulic performance, the surface must be machined to follow the blade surface after the build-up.

Furthermore, in the case where a caul plate made of an erosion-resistant material is used as a lining instead of the build-up, the caul plate must be molded in advance to fit along the blade surface for the same reason. As described above, since the blade surface of the inducer blade is a three-dimensional curved surface, applying erosion-resistant build-up or erosion-resistant lining to the surface has been an extremely difficult and complicated process.

The present invention has been made in view of such problems, and by simplifying the shape of the inducer blade, the manufacturing process can be simplified and the number of man-hours can be reduced. It can ensure pumping performance and suction performance comparable to inducers, and has cavitation erosion resistance.

The purpose of the present invention is to provide a flat plate linear inducer for pumps with high sand erosion resistance.

(Means for Solving the Problems) In order to solve the above problems, the present invention focuses on the fact that the flow within the inducer does not necessarily follow the blade surface in its operating flow area, A sector-shaped flat plate with no curvature is used as the inducer blade.

That is, in an inducer placed in front of the main impeller of the pump, a plurality of inducer blades each having a fan-shaped flat plate with a predetermined reference line passing through the key point of the fan-shaped plate extend from the hub shaft of the main impeller. The reference line is held perpendicular to the axis of the inducer shaft, and the blade surface is inclined at a predetermined angle with respect to the axis of the inducer shaft. It is now one digit in size, with a patch plate made of erosion-resistant material placed at key points on the wing surface of the ducer blade.

(Example) Next, one embodiment of the present invention will be described with reference to the accompanying drawings.

1 and 2 show a centrifugal pump equipped with an inducer according to the present invention, in which an inducer shaft 4 having three inducer blades 3 is screwed onto a hub shaft 2 of a main impeller 1. be.

As shown in FIG. 3, the inducer blade 3 is a flat plate cut out into a substantially fan shape, and is welded to the inducer shaft 4 without any three-dimensional processing. That is, as shown in FIGS. 4 and 5, a predetermined reference line S passing through the point O of the sector is held perpendicular to the axis of the inducer shaft 4, and the blade surface is aligned with the axis of the inducer shaft 4. It should be tilted at a predetermined angle α with respect to the axis.

Further, a patch plate 5 made of an erosion-resistant material is attached to a key point on the surface of each inducer blade 3. In addition to conventional erosion-resistant materials, the material for the backing plate 5 includes partially stabilized zirconia (PSZ) and ZrO2.
Ceramics such as Co-Mo-0r ternary alloy, cemented carbide such as Hastelloy, and engineering plastics such as tetrafluoroethylene fluororesin (ETFE) can be used without any special processing. can.

In general, it is almost possible to predict deviations in the operating range of the pump at the location where cavitation erosion or the like occurs in the inducer, so it is sufficient to attach the abutment plate 5 only to that location.

Further, the attaching plate 5 can be attached by simply placing it on the surface of the inducer blade 3 and joining it, and the joining method thereof is bolt joining or welding joining.

or (:I bonding with adhesive, or (j) any of these combinations may be used.

In this way, since the erosion-resistant patch plate 5 is provided on each inducer blade 3, the occurrence of cavitary erosion, sand erosion, etc. of the inducer blade 3 itself is prevented.

Incidentally, the blade outer diameter, hub diameter, axial length, solid blade number, etc. of the flat plate linear inducer are determined by the same design method as that of a conventional helical type inducer. Also, the setting angle α is between the helical inducer and [J
Be determined so that the solidity matches.

As shown in Fig. 12, the reference line S of the inducer blade 3 is taken on the center line of the fan shape (indicated by S in the figure), and when it is taken upstream or downstream from the center line (respectively S
, , S2), the blade inlet and outlet angles are different.

In other words, in the case of the reference line S taken at the center line of the sector, as shown in FIGS. 4 and 5, the angle of the conventional flat helical inducer is A similar value can be obtained, and a smaller angle can be obtained on the hub side (inner peripheral edge of the inducer blade 3) compared to a flat plate helical inducer. Further, in the case of the reference line S1 taken on the first flow side, as shown in FIGS. 6 to 8, the blade angle is large on the blade inlet side and small on the blade outlet side. In contrast,
In the case of the reference line S2 taken on the downstream side, Figs. 9 to 11
As shown in the figure, the blade angle is small on the blade inlet side and large on the blade exit side.

In this way, by shifting the position of the reference line S from the center position to the 1st stream side or downstream side, the blade inlet or outlet angle can be finely adjusted.

FIG. 13 shows a flat plate linear inducer according to the present invention,
The performance of a centrifugal pump equipped with a conventional flat plate helical inducer was compared.

In the figure, the dotted line is a volute pump without an inducer, the solid line is a volute pump with a conventional flat helical inducer,
- the dash-dotted lines show the respective performance curves of a volute pump with a flat plate linear inducer according to the invention; From the figure, the NPSHreq in the normal operation range of the centrifugal pump is reduced by replacing the conventional flat plate helical type inducer, and the pump suction performance is greatly improved, but the flat plate linear type inducer according to the present invention It can be seen that even with the inducer attached, the pump suction performance comparable to the performance of the conventional flat plate helical type inducer was achieved, and the occurrence of bomb capitate noon was suppressed.

Furthermore, it has been confirmed that in the inducer according to the present invention, by appropriately selecting the blade angle of the inducer blades 3, the occurrence of cavitation in the inducer can be suppressed more than in the conventional flat plate helical type inducer. Therefore, due to the effect of suppressing cavitation that the inducer itself has and the erosion-resistant patch plate 5, the inducer according to the present invention has extremely little cavitation and erosion.

(Effects of the Invention) As is clear from the following explanation, according to the present invention, the inducer blade is formed into a substantially fan-shaped flat plate with a flat blade surface, eliminating the need for three-dimensional machining, and eliminating the need for conventional molding. Processes such as manufacturing and press working are omitted, the inducer manufacturing process is simplified, and the number of man-hours can be reduced. Also,
The caul plate made of erosion-resistant material is simply installed at key points of the flat inducer blade and joined as appropriate, and there is no need to perform the same processing, making the installation process extremely simple. . Therefore, even if the caul plate made of an erosion-resistant material is expensive, it is possible to manufacture an inducer that is inexpensive overall and has good gear erosion resistance by reducing the number of production steps.

Furthermore, by appropriately changing the reference line of the inducer blade, it is possible to adjust the blade inlet or exit angle, which minimizes the performance deterioration caused by the use of a flat plate linear inducer, compared to the conventional flat plate It has the advantage of being able to maintain shear performance comparable to that of a pump equipped with a helical inducer.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a centrifugal pump equipped with an inducer according to the present invention, Fig. 2 is a side view of Fig. 1, Fig. 3 is a plan view showing an inducer blade cut out from a flat plate, and Fig. 4. , FIG. 6, and FIG. 9 are diagrams showing the states in which inducer blades having different reference lines are attached to the inducer shaft (t II), FIG. 5, and FIG. 7. FIG. Side views of Figures 6 and 9;
FIGS. 8 and 11 are views seen from the six directions of FIGS. 7 and 10, respectively, and FIG. 12 shows three types of inducer blades according to the present invention and conventional inducer blades with different reference lines. Figure 13 shows the performance curves of a volute pump without an inducer, a conventional volute pump with a flat plate helical inducer, and a volute pump with a flat plate linear inducer according to the present invention. It is a diagram. 1 ・Main impeller, 2 Hub shaft, 3 Inducer blade, 4... Inducer shaft, 5-
Backing plate, S, S,, S2/Reference line, 0 required. Patent applicant: Nishijima Seisakusho Co., Ltd. Agent: Patent attorney: Aoyama Aoba Two idiots Figure 4
Figure 6 Figure 9 Figure 10

Claims (1)

[Claims] (1) In an inducer placed in front of the pump main impeller, a plurality of inducer blades each having a fan-shaped flat plate with a predetermined reference line passing through the key point of the fan-shaped plate are installed in an inducer blade extending from the hub shaft of the main impeller. Attach the reference line to the inducer shaft at right angles to the axis of the inducer shaft, and tilt the blade surface at a predetermined angle with respect to the axis of the inducer shaft. A flat plate linear inducer for pumps, characterized by having a caul plate made of an erosion-resistant material attached to important points on the blade surface.