JPH0735090A - Thrust balance mechanism - Google Patents

Abstract

PURPOSE:To provide a thrust balance mechanism that can be applied even in a multistage pump of high head and large capacity without greatly varying standard products by enhancing balancing thrust. CONSTITUTION:In a thrust balance mechanism wherein a high-pressure fluid delivered from the impeller 10 of the final stage is allowed to pass through a high-pressure balance chamber 20 and a low-pressure balance chamber 22 divided from each other between fixed wall portions 12 by means of a diaphragm 18 (gap (g)) between a rotating balance disk 14 and a balance sheet 16 and is then bypassed to a suction-side low-pressure fluid, a restrainer 30 for restraining the rotation of fluids within space inside a balance-chamber gap S20 is provided on the fixed wall 12 of the high-pressure balance chamber 20. An accelerator 32 for accelerating the rotation of fluids within space inside a balance-chamber gap S22 is provided on the rotating balance disk 14 of the low-pressure balance chamber 22. The gaps S20, S22 are set to a relatively small dimension such that both are affected by the rotation of the balance disk 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thrust balance mechanism for a multi-stage pump, and more particularly to a thrust balance mechanism using a rotary balance disc.

[0002]

2. Description of the Related Art Generally, in a single-suction multi-stage pump (hereinafter simply referred to as a multi-stage pump), a pump thrust toward the suction side is generated. A balance mechanism) is provided.

That is, in FIG. 6, the thrust balance mechanism is arranged so that the discharge side high pressure liquid from the final stage impeller 10 is
The suction side low pressure liquid is passed through the high pressure side balance chamber 20 and the low pressure side balance chamber 22 which are defined between the fixed wall portion 12 via the rotary balance disc 14 and the throttle 18 (gap g) between the disc 14 and the balance sheet 16. Is configured to bypass. With this configuration, via the pressure drop across the throttle 18, the balance thrust force generated between the two balance chamber 20 and 22 (the pump thrust retaining force) T _B is, the pump thrust force T _P and balance Is configured to.

That is, when the pump thrust force T _P increases, the shaft 24 moves (forwards) in the pump thrust direction to reduce the gap g, thereby increasing the pressure drop by the throttle 18 and increasing the balance thrust force T _B. Increase. on the other hand,
When the pump thrust force T _P decreases, the shaft 24 moves (retracts) in the balance thrust direction to increase the gap g, so that the pressure drop due to the throttle 18 decreases and the balance thrust force T _B decreases. As a result, the position of the shaft 24 is automatically balanced at the point that the thrust forces T _P and T _B are the same.

As described above, according to this type of thrust balance mechanism, the pump thrust of the multistage pump can be automatically canceled with a relatively simple structure.

The thrust force T _P or T _{B at the} balance position is expressed by the following equation (1) and FIG.

[0007]

[Equation 1]

Here, P ₂₀ ′ (first term) and P ₂₂ ′
(Item 2) is the high-pressure side and low-pressure side balance chambers 20, 2
The pressure at 2 (integral value of pressure distribution) is shown. Further, r _B and r _S are the outer and inner diameters of the balance disk 14, and p ₁ ′, p ₂ ′ and p ₃ ′ are positions I (the inner diameter portion of the high pressure side balance chamber 20) and II (the diaphragm 18).
And (III) (the outer diameter portion of the low-pressure side balance chamber 22).

[0009]

However, the conventional thrust balance mechanism described above still has a problem to be improved as described below.

That is, in general, multistage pumps have recently been required to have a particularly high head and a large capacity. For this reason, the number of stages is increased and the pump thrust force is increased. Therefore, it is required to increase the balance thrust force. However, in the conventional thrust balance mechanism, a special design change is required to increase the balance thrust force, which increases cost and further increases friction loss (pump power). It had drawbacks.

That is, in the configuration shown in FIG. 6 described above, when the pump thrust force T _P increases, the gap g between the balance disc 14 and the balance sheet 16 is reduced in order to increase the balance thrust force T _B. It
In this case, in the conventional thrust balance mechanism, for example, in the above-described high-lift and large-capacity pump,
When operating in a relatively high flow rate and low head region, the gap g is reduced too much and the balance disk 14 and the balance sheet 16 try to come into contact with each other. Therefore, in order to prevent this, the outer diameter r _B of the balance disk 14 is increased.

However, since this preventive measure enlarges (design changes) the entire structure of both balance chambers 20 and 22 including the balance disk 14 and the balance sheet 16 and other components, as described above. However, it is obvious that there are drawbacks such as a significant increase in cost and a reduction in pump efficiency. In the above design change, there is a practical limit to the size increase of each component such as a balance disk, and these components should be formed as small as possible from the viewpoint of cost and manufacturing. Of course, it is a thing.

Therefore, to further conclude, the above-mentioned difficulties are caused by a basic defect (lack of balance thrust force) of the pressure generating mechanism of the conventional thrust balance mechanism. Then, the present invention aims to solve the above-mentioned problems by removing the defect of the pressure generating mechanism. Therefore, first, regarding the configuration and operation of the pressure generating mechanism itself,
The following is a general description.

Referring again to FIG. 6, the liquid swirl flow associated with the rotation of the balance disc 14 generally exists in the gap (space) S between the balance chambers 20 and 22, and this swirl flow is the balance disc. It can be regarded as a velocity-related forced vortex motion. Therefore, regarding the swirl flow, a relational expression of u = Krω (where u: peripheral velocity of fluid, r: radius, ω: angular velocity of balance disk 14, and K: peripheral velocity ratio) and Δp = ρ / 2 * K ² (r ₀ ² −r
_i ² ) ω ² (where Δp: differential pressure in the gap S, ρ: fluid density, r ₀ : outer radius, and r _i : inner radius).

However, the peripheral velocity ratio K is a function of the clearance S and the outer diameter r _B , and its value is determined by Kurokawa et al. (For example, the Japan Society of Mechanical Engineers Proceedings No. 346, centrifugal type turbomachinery). It is known from the study on axial thrust) and the like that the clearance S in the high pressure side balance chamber 20 shown in the figure is usually about 0.5 to 0.4.

Therefore, considering the above relational expressions and numerical values, when the above-mentioned FIG. 7 is examined again, in the figure, first, both components of the balance thrust force T _B generated in both balance chambers 20 and 22, that is, both pressures. P ₂₀ ′ (first term integral value) and P ₂₂ ′ (second term integral value) are both area P defined between both line segments L ₂₀ ′ and L ₂₂ ′ and the vertical axis r line, respectively. ₂₀ ', P _22' are displayed in. It is obvious that the balance thrust force T _B becomes larger as the high-pressure side balance chamber pressure P ₂₀ ′ and the low-pressure side balance chamber pressure P ₂₂ ′ become smaller. In addition, reference numeral l
Shows the opposing surface lengths of the balance disk 14 and the seat 16.

However, in the conventional thrust balance mechanism, the above-mentioned relationship, that is, the relationship of increasing the balance thrust force is not sufficiently achieved due to the defect of the pressure generating mechanism. That is,
In other words, the pressure P ₂₀ ′ in the high pressure side balance chamber becomes relatively small, while the pressure P ₂₂ ′ in the low pressure side balance chamber becomes relatively large. Note that, as is clear from FIG. 7, the line segment L ₂₀ ′ has a hydraulic pressure p
Has steep toward 'from the hydraulic p _{2' 1} to (value of the above-mentioned peripheral speed ratio K is meant that it is set to about 0.5 to 0.4), whereas the line segment L ₂₂ ' Relates to the fact that the hydraulic pressure p ₂ ′ is shifted to the hydraulic pressure p ₃ ′ in a substantially vertical direction (meaning that the value of the peripheral speed ratio K is set to approximately 0). And, this means that the high pressure side balance chamber 2
Within 0, the fluid pressure (static pressure) drops sharply due to the relatively high-speed swirling flow, while on the other hand, within the low-pressure side balance chamber 22, since the swirling flow is relatively low, the hydraulic pressure (static pressure) is It is easily understood that it relates to good preservation.

As described above, in the conventional thrust balance mechanism, the balance thrust force is insufficient particularly in a multistage pump having a high lift and a large capacity. Therefore, it is necessary to change the size and design of the standard product. For this reason, there are drawbacks such as an increase in cost and an increase in friction loss (pump power).

Therefore, the object of the present invention is to be applied to the multistage pump of high lift and large capacity as it is without changing the standard product as it is by improving the balance thrust force. It is to provide a thrust balance mechanism that can be performed.

[0020]

In order to achieve the above object, a thrust balance mechanism according to the present invention comprises a rotating balance disk and a disk sheet for discharging high pressure liquid on the discharge side from a final stage impeller between fixed wall portions. In the thrust balance mechanism that bypasses to the suction side low pressure liquid through the high pressure side and low pressure side balance chambers partitioned through the throttle gap,
It is characterized in that the fixed wall of the high-pressure side balance chamber is provided with a suppressing section for suppressing liquid swirl and / or the rotating balance disk of the low-pressure side balance chamber is provided with a promoting section for promoting liquid swirl.

In this case, the restraining portion and the accelerating portion can be constituted by radial convex lines and / or concave lines provided on the fixed wall and the rotary balance disk, respectively.

[0022]

In the present invention, in the high pressure side balance chamber,
Fluid pressure (static pressure) due to the swirling flow being suppressed by the suppression unit
Is well preserved. On the other hand, in the low pressure side balance room,
Fluid pressure (static pressure) due to the swirling flow being accelerated in the acceleration section
Drops sharply. Therefore, according to the present invention, it is clear that the balance thrust force increases because the high pressure side balance chamber pressure increases while the low pressure side balance chamber pressure decreases. Then, this makes it possible to apply it to a multistage pump having a particularly high head and a large capacity as it is, without significantly changing the standard product.

[0023]

Embodiments of the thrust balance mechanism according to the present invention will be described below in detail with reference to the accompanying drawings. For convenience of explanation, the same components as those of the conventional structure shown in FIGS. 6 and 7 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, the overall structure of the thrust balance mechanism according to the present invention is basically the same as the conventional structure (FIG. 6). Therefore, although overlapping, but briefly described again, the thrust balance mechanism causes the high pressure liquid on the discharge side from the final stage impeller 10 to rotate between the fixed wall portion 12 and the rotation balance disk 14 and between the disk 14 and the balance sheet 16. The high-pressure side balance chamber 20 and the low-pressure side balance chamber 2 which are partitioned via the throttle 18 (gap g)
The balance thrust force (pump thrust holding force) T _B generated between the balance chambers 20 and 22 via the pressure drop in the throttle 18 by bypassing the suction side low pressure liquid through the pump thrust force T It is configured to balance _P. The thrust forces T _P and T _B are expressed in the same manner as in the case of the prior art, that is, by the following formula (2) corresponding to the formula (1) and FIG. 7 and FIG.

[0025]

[Equation 2]

Here, each reference numeral is P ₂₀ (first
And P ₂₂ (second term) are the pressures in the high-pressure side and low-pressure side balance chambers 20 and 22 (pressure distribution integral value), r _B
And r _S are the outer diameter and inner diameter of the balance disk 14,
p ₁ , p ₂ and p ₃ are at position I (the high pressure side balance chamber 20).
It is obvious that the hydraulic pressures are shown in (inner diameter portion of), II (outlet portion of the throttle 18) and III (outer diameter portion of the low pressure side balance chamber 22), respectively.

In the present invention, however, in the above structure, the fixed wall 12 of the high-pressure side balance chamber 20 is provided with the suppressing portion 30 for suppressing the liquid swirling in the space inside the balance chamber gap S ₂₀ . On the other hand, the rotation balance disk 14 of the low-pressure side balance chamber 22 is provided with a promoting portion 32 that promotes liquid swirling in the space inside the balance chamber gap S ₂₂ . In this case, the gaps S ₂₀ and S ₂₂ are set to relatively small dimensions such that both gaps are affected by the rotation of the balance disc 14. The suppressing portion 30 may be, for example, the fixed wall 1.
2 are provided radially on the ridges 30a [(a) and (b) of FIG. 3].
Reference] or a recessed line 30b [see (a) and (b) of FIG. 4]. In addition, the promotion unit 32,
For example, the balance disk 14 can be formed by the ridges 32a also provided radially (see FIGS. 5A and 5B).

Therefore, according to the present invention, both balance chambers 2
Both components P of the balance thrust force T _B generated at 0 and 22
₂₀ and P ₂₂ are defined by both line segments L ₂₀ and L ₂₂ 22 as in the case of the conventional art. However, the two line segments L ₂₀ and L ₂₂ are set such that the value of the peripheral velocity ratio K of the swirling fluid in the gaps S ₂₀ and S ₂₂ is almost 0 in the high pressure side balance chamber 20, while the low pressure is low. Since the side balance chamber 22 is set to be approximately 1, the former line segment L
₂₀ shifts from the hydraulic pressure p ₁ ′ to the hydraulic pressure p ₂ ′ in a substantially vertical direction. On the other hand, the latter line segment L ₂₂ ′ is steeply inclined from the hydraulic pressure p ₂ ′ to the hydraulic pressure p ₃ ′. That is, in the high-pressure side balance chamber 20, the swirl flow is suppressed to a low speed and the hydraulic pressure (static pressure) is stored, while in the low-pressure side balance chamber 22, the swirl flow is accelerated at a high speed and the hydraulic pressure (static pressure) is increased. ) Has disappeared.

Therefore, according to the present invention, the high-pressure side balance chamber pressure P ₂₀ is increased and the low pressure is reduced as compared with the above-mentioned prior art (see the line segments L ₂₀ ′ and L ₂₂ ′ shown by the dotted lines). Since the side balance chamber pressure P ₂₂ decreases, it is clear that the balance thrust force T _B increases. It has been confirmed from experimental results that the increase reaches about 1.5 times in the balance disk 14 having the same diameter.

As described above, according to the present invention, since the balance thrust force can be greatly improved by using the balance discs having the same diameter, the standard standard can be applied especially to a multistage pump having a high lift and a large capacity. It is possible to apply the product as it is without changing the product significantly. Therefore, a high-efficiency thrust balance mechanism for a high-lift and large-capacity multi-stage pump can be provided at low cost.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and many design changes can be made without departing from the spirit thereof.

[0032]

As described above, in the thrust balance mechanism according to the present invention, the high pressure liquid on the discharge side from the final stage impeller is partitioned between the fixed wall portions via the rotary balance disc and the disc sheet throttle gap. In a thrust balance mechanism that bypasses the low-pressure liquid on the suction side through the high-pressure side and low-pressure side balance chambers, a swirling part that suppresses liquid swirling on the fixed wall of the high-pressure side balance chamber and / or liquid swirling on the rotating balance disc of the low-pressure side balance chamber Due to the provision of the promoting section that promotes, the swirl flow is suppressed to a low speed in the high pressure side balance chamber, and the hydraulic pressure (static pressure) is stored, while the swirl flow is accelerated to a high speed in the low pressure side balance chamber. The hydraulic pressure (static pressure) disappears. As a result, the high pressure side balance chamber pressure increases and the low pressure side balance chamber pressure decreases, so the balance thrust force is increased.

Therefore, according to the present invention, it is possible to apply it to a multistage pump having a particularly high head and a large capacity as it is without changing the standard product. That is, a high-efficiency thrust balance mechanism for a high-lift and large-capacity multi-stage pump can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an embodiment of a thrust balance mechanism according to the present invention.

FIG. 2 is a radius-hydraulic pressure diagram for explaining the balance thrust force achieved by the thrust balance mechanism shown in FIG.

3A and 3B show an embodiment of a suppressing portion (ridge) applied to the high pressure side balance chamber fixing wall of the thrust balance mechanism shown in FIG. 1, where (a) is a plan view and (b) is a side sectional view. It is a figure.

4A and 4B show an embodiment of a suppressing portion (recess) applied to the high pressure side balance chamber fixing wall of the thrust balance mechanism shown in FIG. 1, in which (a) is a plan view and (b) is a side sectional view. It is a figure.

5A and 5B show an embodiment of a promoting portion (protrusion) applied to the low pressure side balance chamber balance disc of the thrust balance mechanism shown in FIG. 1, (a) is a plan view, and (b) is a side sectional view. It is a figure.

FIG. 6 is a cross-sectional view of essential parts showing a conventional thrust balance mechanism.

7 is a radius-hydraulic pressure diagram for explaining the balance thrust force achieved by the thrust balance mechanism shown in FIG.

[Explanation of symbols]

 10 Final Stage Impeller 12 Fixed Wall 14 Balance Disc 16 Balance Sheet 18 Throttling 20 High Pressure Side Balance Chamber 22 Low Pressure Side Balance Chamber 24 Shaft 30, 30a, 30b Suppressing Section 32 Promoting Section

Claims (2)

[Claims] 1. A high-pressure liquid on the discharge side from the final stage impeller,
In the thrust balance mechanism that bypasses the low-pressure liquid on the suction side through the high-pressure side and low-pressure side balance chambers defined by the rotary balance disc and the disk sheet throttle gap between the fixed wall parts, the liquid swirls on the fixed wall of the high-pressure side balance chamber. A thrust balance mechanism characterized in that a suppressing portion for suppressing the above-mentioned phenomenon and / or a accelerating portion for accelerating the swirling of the liquid are provided on the rotation balance disc of the low-pressure side balance chamber. 2. The thrust balance mechanism according to claim 1, wherein the restraining portion and the accelerating portion are formed by radial convex lines and / or concave lines provided on the fixed wall and the rotary balance disc, respectively.