JPS6088896A - Impeller for centrifugal pump - Google Patents

Abstract

PURPOSE:To improve suction performance by communicating a balance chamber with the suction side of an impeller via a communication hole and an introduction hole in a shaft to keep pressure balance, reduce axial thrust, and preventing a turbulent flow from being produced and pressure on the suction side from being reduced. CONSTITUTION:A fluid leaking into a balance chamber 18 reaches an opening 23 in an impeller nut 17 through a hole 22, a communication hole 21, and an introduction hole 20 in a shaft 12, reversed on a concave surface 24a of a conical body 24, and injected from an annular flow passage 25 along a suction flow passage conical surface in front of a back shroud 2. Accordingly, the balance chamber 18 is kept and axial thrust of the impeller 1 is reduced, while a circulating flow flows out in the same directiin as a fluid flowing into the impeller 1. Thus, a turbulent flow can be prevented from being produced, while suction performance to be raised without sacrificing the pump performance, enabling noise and vibration to be prevented from being produced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Prior Art) The present invention relates to improvements in impellers for centrifugal pumps.

The first problem that arises when increasing the speed of pump operation is that pump performance is inhibited by cavitation. Therefore, it is necessary to improve cavitation performance without reducing pump performance.

Conventional countermeasures for centrifugal pumps include: widening the flow path width at the impeller blade inlet;

@Reduce the number of blades. Increase the O-blade inlet angle. Such methods were used. However, these methods
Even if it is effective in improving cavitation performance, it is often accompanied by the negative effect of sacrificing pump performance, so it is not a measure that can be taken recklessly. In addition to the above-mentioned means, as a means for improving the suction performance of the pump, as shown in FIG. Methods have also been adopted to improve cavitation performance by increasing the temperature. However, this method also causes backflow A when placed at a low flow rate, which causes pressure pulsations and causes noise and imaging.

On the other hand, in a centrifugal pump, in order to reduce the axial thrust generated in the suction direction, as shown in FIG. 5 is provided, and several balance holes 6 are provided in the back shroud 2 inside this annular projection 5 to balance the pressure on the back side of the back shroud 2 with the pressure on the suction side and eliminate axial thrust.

In the figure, 7 is a casing, 8 is an impeller wear ring provided on the annular protrusion 5, and 9 is a case wear ring provided on the casing 7, which is opposite to the impeller wear ring. Further, 10 is an impeller wear ring fitted to the outer periphery of the suction port 4;
is a case wear ring provided on the casing 7 so as to face it.

12 is a shaft supported by a bearing (not shown), and 12a is a shaft portion with a smaller diameter, to which the boss portion 18 of the impeller I is fixed via a key 14.

Reference numeral 12b denotes the most advanced shaft portion of the shaft 12, into which the boss portion 15 of the inducer 1a is fitted via a key 16, and is fixed with an invera nut 17. Note 1
8 is a balance chamber, and 9 is a sleeve that covers the shaft 12.

This axial thrust reduction structure functions by the fluid leaking between the annular protrusion 5 and the gauging 7 circulating from the balance hole 6, but this circulating flow is caused by the fluid flowing into the impeller l from the suction port 4. Because it collides with the flow and generates a backflow B, which obstructs smooth inflow into the impeller,
This disturbed the flow of fluid and caused deterioration of suction performance. Especially in low flow areas, the lift height is high, so
Since the reflux and backflow also increased, the suction performance deteriorated significantly.

In addition, impurities in the fluid easily enter the balance hole 6 when the pump is at rest, which eventually causes galling of the shaft and heat generation.

(Objective of the present invention) The present invention has been made to solve the problems inherent in the prior art, and it improves suction performance without sacrificing pump performance, and also eliminates the risk of noise and vibration. It is an object of the present invention to provide an advantageous impeller for a centrifugal pump that is not easily affected by impurities in the fluid.

(Structure of the present invention) In order to achieve the above-mentioned object, the present invention provides an annular protrusion with approximately the same diameter as the suction port of the front shroud on the back side of the back shroud of the centrifugal impeller to prevent contact with the casing. A balance chamber is formed inside the annular protrusion between the seal and the casing, and a conduction hole extending from the balance chamber to the tip of the impeller boss is provided in the shaft of the impeller. By turning the opening along the conical surface of the suction flow path on the front surface of the pack shroud, the fluid leaking into the balance chamber is configured to flow out in the same direction as the suction fluid of the impeller at the center of the impeller suction side. .

(Example) Hereinafter, examples of the present invention will be described in detail with reference to figures.
FIG. 2 is a sectional view of the centrifugal pump according to the present invention, and the first
The same reference numerals as those in the figures indicate the same constituent members.

That is, a front shroud 3 is attached to the back side (gauging side) of the back shroud 2 of the impeller 1 fitted to the stepped shaft portion 12a of the shaft 12 supported by a bearing (not shown).
An annular projection 5 having approximately the same diameter as the suction port 4 is provided, an impeller wear ring 8 is fitted onto the annular projection 5, and a non-contact seal is formed by a case wear ring 9 provided on the casing 7. A balance chamber 18 is formed inside the annular projection 5 and is sandwiched between the back shroud 2 and the teething hole.

In this embodiment, the boss portion 18 of the back shroud 2
A through hole 20 is formed in the shaft portion 12a of the shirt (to which the shirt is fitted) along the longitudinal direction of the shaft, and a diametrical communication hole 21 is provided in the shaft 12 that communicates with the end of the through hole 20.
In order to communicate this communication hole 21 with the lance chamber 18,
A hole 22 is bored in the impeller boss portion 13.

On the other hand, the other side of the conduction hole 20 is opened at the tip of the shaft 12 and further has an opening 28 provided at the center of the impeller nut 17.
and the suction side of the impeller 1.

A conical body 24 having four sides 24a covering the opening 23 is provided on the front surface of the opening 28 of the impeller nut 17, and an annular flow path 25 is formed between the concave fi 24a and the outer peripheral surface 17a of the impeller nut 17.

The conical body 24 is connected to the casing 7 by a plurality of suction ribs 26.
is supported by

In the embodiment shown in FIG. 2, the support plate of the cone 24 is also used as the suction rib 26 of the pump, but the cone 24 may also be supported from the impeller nut 17 side.
The impeller nut 17 may be formed integrally with the impeller 1.

Further, in the embodiment shown in FIG. 2, the hole 22 is provided in the impeller boss portion 18, but it may be provided in the sleeve 19 that covers the shaft 12, or the hole 22 may be provided in the sleeve 19 that covers the shaft 12, or the hole 22 may be provided in the sleeve 19 that covers the shaft 12. If the communication hole 21 directly communicates with the balance chamber 18, the hole 22 is unstable.

Furthermore, as shown in FIG.
It can also be formed as a plurality of radial flow paths following the flow path.

Note that 26 in the figure is a set screw that fixes the boss portion 13 of the impeller to the shaft 12.

(Action of the present invention) Since the present invention is configured as described above, the fluid leaked into the balance chamber 18 is transferred to the hole 22, the communication hole 21 and the shaft 12.
The opening 28 of the impeller nut 17 passes through the through hole 20 in the
Then, it is turned away from the axis by the concave surface 24a of the circular αE body 24, and is ejected from the annular flow path 25 along the conical surface of the suction flow path on the front surface of the pack shroud 2.

Therefore, since the balance chamber 18 communicates with the suction side of the impeller 1, the pressure balance is maintained, the axial thrust of the impeller is reduced, and the reflux flow flows out in the same direction as the inflow body of the impeller, so that the conventional Not only does it not cause turbulent flow like a balance hole, it also promotes the reduction and effective use of fluid energy leaking to the back side of the back shroud 2, and improves the pump's suction performance by preventing pressure drop on the impeller suction side. can.

(Effects of the present invention) Figure 4 shows a pump with a diameter of 50 mm, a pump with a conventional balance hole 6, and a pump with a maximum efficiency of 0.7''' 4 turns, a lift of 180 m%, and a rotation speed of 2988 rpm. This shows the results of a comparative experiment with the one according to the present invention, where the horizontal axis shows the flow Q'''/min', and the vertical axis shows the lift H (ml
, efficiency η (%), shaft power L (kW), suction specific speed S
18 (rpl■, /., m) is a characteristic curve diagram. In the figure, the characteristics when the present invention is implemented are shown by solid lines,
The characteristics of the conventional example are shown by broken lines.

Note that the suction specific speed S is 31+ nQh /H, as is well known as an index representing cavitation performance.
8vV4 (H: pump rotation speed rpm, Q: flow rate m
8/, H8v: Effective suction head m) is determined by 1n.

As can be seen from this figure, the value of S decreases with the conventional model as the flow rate decreases, indicating a decline in suction performance, but the model of the present invention has a suction specific speed of approximately 20% at the maximum efficiency point. The suction performance was improved by increasing S, and the suction performance maintained high performance even when the flow was narrowed down.

Moreover, the H-Q curve and efficiency are improved, and the performance of the entire pump can be improved.

As described above, the present invention does not require an inducer.
In addition to being as effective as an inducer while improving pump performance, the communication hole and conduction hole according to the present invention are open to the outlet of the fluid in the balance chamber.
As a result of sufficient discharge of impurities in the fluid, it has the excellent effect of preventing shaft galling and heat generation.

[Brief explanation of drawings]

Figure 1 is a sectional view showing a conventional centrifugal pump, Figure 2 is a sectional view showing an embodiment of the present invention, Figure 8 is a partial sectional view showing an embodiment of a pond, and Figure 4 shows the characteristics of a centrifugal pump. It is a line diagram.・l...Blade i 2...Back shroud 8...Front shroud structure...Suction port 5...Annular projection 6...Balance hole 7...Casing 8110
... Impeller mounting ring 9, 11 ... Case wear ring 12 ... Shaft 13 ... Boss part 17 ... Impeller nut 18 ... Balance chamber 19 ... Sleeve 2
0... Conduction hole 21... Communication hole 22... Hole 23... Opening 24... Cone 24a... Concave surface 25... Annular flow path. Patent applicant: Dengyosha Machinery Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4 (2 (VwIT)

Claims (1)

[Claims] An annular projection having approximately the same diameter as the intake port of the front shroud is provided on the back side of the back shroud of the L impeller to form a non-contact seal with the casing. In a centrifugal pump in which a balance chamber is provided in a gap inside the annular projection, the balance chamber and the suction side of the impeller boss are communicated through a communication hole provided in the center of the impeller, and the communication portion with the suction side of the impeller boss is connected. An impeller for a centrifugal pump characterized by an opening along the fluid inflow direction of the conical suction mud passage of the impeller. 2. An impeller for a centrifugal pump according to claim 1, wherein a through hole is provided at the center of the shaft and an impeller locking nut, and a concave surface of a conical body is arranged with a gap on the front surface of the impeller nut.