JPH11308800A - Conned motor pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a canned motor pump which balances a shaft thrust force with a simple constitution, without boring a balance hole in a first step, when the head of the first step is high. SOLUTION: In a pressurized circulation type canned motor pump, impellers 11, 12 are arranged in the mutually opposite directions on both ends of a rotating shaft 1, a main flow channel is installed from the low pressure side end to a high pressure side end, an internal circulation flow channel 2 is installed from the impeller 12 on the high pressure side end toward the impeller 11 on the low pressure side end, and a rotor is arranged in the internal circulation flow channel 2. The external diameter of the impeller 12 on the high pressure side end is made greater than that of the impeller 11 on the low pressure side end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a canned motor pump which can be operated without boiling in a canned motor chamber even with a liquid having a high vapor pressure, and in particular, can realize a high head with a small flow rate and a simple structure. Related to a highly reliable canned motor pump.

[0002]

2. Description of the Related Art Conventional canned motor pumps include:
For example, there is one as shown in FIG. In this conventional canned motor pump, impellers 51 and 52 of the same design are arranged in the first and second stages, and have the same impeller outer diameter and the same impeller suction diameter. Thus, the canned motor pump shown in FIG. 5 has a configuration in which the axial thrust force generated in the impellers 51 and 52 is offset, and the residual axial thrust force generated in other portions is held by the thrust bearing.

In this conventional canned motor pump, if the lift per stage is not so high, for example, if it is several tens of meters, it can be held by the thrust bearing without any problem. In recent years, there has been a demand for downsizing of a device relating to a canned motor pump, and there is a case where another process liquid is used due to environmental problems. In such a field, a pump having a smaller flow rate and a higher head is desired. It has become.

[0004]

However, in the conventional canned motor pump, when the head exceeds several hundred meters per stage, the impellers of the same design are arranged in the first and second stages, and However, there is a problem that even if the axial thrust force generated in the above is canceled out, the residual axial thrust force generated in other parts, for example, the one generated on the shaft end face, becomes insignificant.

[0005] The residual shaft thrust force generated on the shaft end surface acts as a force having a magnitude obtained by multiplying the area of the shaft penetrating portion by the first stage lift, and acts in the direction of the first stage to increase the lift per stage. Increases in proportion to. FIG. 6 shows the residual axial thrust force T1 acting on the first-stage impeller 51.
FIG. 3 is an explanatory diagram for explaining the method. Here, each part
Pressures P1 to P6 and pressures P2 'and P6' are acting. The pressure acting on the impeller section is offset, and (P2 ′
−P2) = (P6′−P6). On the shaft end face, P5> P1. On the rotor end face, P4> P3. As a result, the following residual shaft thrust force T1 acts toward the first-stage impeller 51.

T1 = (P5-P1) × A1 + (P4-P3) × A2 Here, A1 is a shaft cross-sectional area, and A2 is a rotor cross-sectional area.

[0007] This residual axial thrust force is held by a thrust bearing. However, when the load increases, the reliability is inevitably degraded, and a large thrust bearing for handling the load is required. A large thrust bearing increases costs and is not preferable.

Another example of a small-flow, high-lift canned motor pump is that a balance hole is drilled in the first-stage impeller 51 to reduce the pressure on the back surface of the first-stage impeller 51 and balance the total axial thrust force. Some take. However, in this canned motor pump, the pressure in the motor chamber is inevitably reduced due to the perforation of the balance hole, and the liquid tends to boil in the motor chamber with a liquid having a high vapor pressure, thereby reducing the reliability of this type of pump. Had created a factor.

Therefore, in the canned motor pump having the opposed multistage impeller as described above, even if the lift per stage is high, the shaft thrust force is structurally balanced and the pressure in the motor chamber is not reduced. And highly reliable ones were desired.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. An object of the present invention is to make a balance hole perforated at the first stage with a simple structure even if the lift per stage is high. An object of the present invention is to provide a canned motor pump that balances the axial thrust force without using the same.

[0011]

According to the present invention, one or more impellers are disposed at opposite ends of a rotating shaft, and a main flow path is provided from a low pressure side end to a high pressure side end. The present invention relates to a pressurized circulation type canned motor pump in which an internal circulation passage is provided toward an impeller at a low pressure side end, and a rotor is disposed in the internal circulation passage. This is achieved by making the outer diameter of the impeller at the side end larger than the outer diameter of the impeller at the lower pressure side end.

Further, the present invention is attained by setting the suction opening of the impeller at the high pressure side end to be larger than the suction opening of the impeller at the low pressure side end.

Further, the present invention is achieved by making the penetrating portion (impeller boss) of the impeller at the high pressure side end smaller than the penetrating portion (impeller boss) of the impeller at the low pressure side end.

Further, the present invention is achieved by setting the number of stages of the impeller at the high pressure side end to be greater than the number of stages of the impeller at the low pressure side end.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a main part showing a structure of a canned motor pump according to an embodiment of the present invention. This canned motor pump has impellers 11 at both ends of the rotating shaft 1.
And an impeller 12 are provided, and a main flow path is provided from the end on the low pressure side to the end on the high pressure side. Further, the internal circulation passage 2 is provided from the high pressure side end impeller 12 to the low pressure side end impeller 11. And, it is a pressurized circulation type canned motor pump in which a rotor is arranged in the internal circulation channel 2.

Further, in this canned motor pump, the outer diameter D22 of the impeller 12 at the high pressure side is larger than the outer diameter D21 of the impeller 11 at the low pressure side.

A residual axial thrust force T determined by the following equation 1 acts on the first-stage impeller 11.

[0019]

(Equation 1) Here, Dr is the inner diameter (cm) of the base and is a dimension based on the inlet diameter. Db is the thickness (cm) of the boss. HL is the head (m) within the Dr diameter behind the impeller. The head HL is obtained by the following equation (2).

[0020]

(Equation 2) Here, u2 is the outer peripheral speed (m / s) of the impeller.
ur is the peripheral speed (m / s) of the base. K3 is a predetermined coefficient. The theoretical explanations of the above equations 1 and 2 are described in Susumu Terada, “Design and drafting of a centrifugal pump”.

As is clear from the above equations (1) and (2),
In a plurality of impellers that rotate on the same axis, if the shapes are the same, the generated axial thrust force is the same. Therefore, when the impellers of the same design are arranged facing each other, the axial thrust force at each impeller can be canceled.

From equation (1), as the head HL increases, the axial thrust force T increases. Also, as the inner diameter Dr of the base increases, the axial thrust force T increases. Furthermore, the axial thrust force T increases as the thickness Db of the boss increases.

When the second-stage impeller (high-pressure side end impeller) 12 is made larger than the first-stage impeller (low-pressure side end impeller) 11 as shown in FIG. 1, the following two effects will be obtained. is there. First, since the first stage head HL is reduced, the residual axial thrust force generated at the shaft end is reduced. Second, since the first stage head HL decreases and the second stage head HL rises, the residual axial thrust force at the impeller acts in the direction of the second stage.

Next, the following case will be examined as one embodiment. First, as a specification, the flow rate is 6
(M3 / h), the head is 200 (m), the number of stages of the impeller is two, the rotation speed is 10,000 (rpm), and the thickness of the boss is 2.5 (cm) (in this case, the first stage). The impeller and the second-stage impeller are the same). In this case, the pressure difference at the rotor section is negligible due to the small output.

<When the same impeller is used> This is shown in FIG.
The first stage lift: 100 m The outer diameter D2 of the impeller 51 = 8.7 cm The inner diameter Dr of the base = 5 cm, the thickness of the boss Db = 2.5 cm The second stage lift: 100 m The outer diameter D2 of the impeller 52 is 8.7 cm. The inner diameter Dr of the base is 5 cm, and the thickness Db of the boss is 2.5 cm.

The residual shaft thrust force at the shaft end is 49.1.
kgf (481 N). In a conventional canned motor pump, this is held by a shaft thrust bearing. However, since the rotation speed is 10,000 rpm and a PV value (design constant multiplied by pressure and speed) increases in a carbon bearing normally used in a canned motor pump, it is used. It was not possible and required expensive ceramic bearings. In addition, even with ceramic bearings, there is a problem in reliability because the PV value is large.

<Case where the first-stage impeller is smaller than the second-stage impeller> This is the case of the canned motor pump according to the embodiment of the present invention shown in FIG. 1, and the first-stage head: 75 m The outer diameter D21 of the impeller 11 = 7.5cm Inner diameter Dr of cap = 5cm, Boss thickness Db = 2.5cm Second stage head: 125m Outer diameter D22 of impeller 12 = 9.7cm Inner diameter Dr of cap = 5cm, Boss thickness Db = 2 0.5 cm 2.

As for the overall performance, the total head is 200 m,
This is the same as when the same impeller is used (in the case of FIG. 5). The residual shaft thrust force at the shaft end is 36.8 kgf
(361 N), which is a decrease of 12.3 kgf (121 N) as compared with the case where the same impeller is used. Also,
The axial thrust force at the impeller section is 66.6 kg at the first stage.
f (653N) and the second stage is 102.5 kgf (10
05N), which is 35.9 kgf in the second stage direction (the direction opposite to the residual axial thrust force at the shaft end) by deduction.

Therefore, in this canned motor pump,
36.8-35.9 = 0.9kgf (8.8N) in total
And a very small residual axial thrust force.

<Case where Second Stage Inlet Diameter is Greater Than First Stage Impeller> This is the case of the canned motor pump according to the embodiment of the present invention shown in FIG. Is the same, the first stage head: 100 m Outer diameter D2 of the impeller 21 = 8.7 cm Inner diameter Dr1 = 5 cm, boss thickness Db = 2.5c
m First stage suction diameter = 5 cm Second stage lift: 100 m Outer diameter D2 of impeller 22 = 8.7 cm Inner diameter Dr2 = 5.9 cm, boss thickness Db = 2.
5 cm The second stage suction port diameter is 5.9 cm.

The residual shaft thrust force at the shaft end is 49.1k
gf (481 N), and the axial thrust force at the impeller portion is 84.6 kgf (830 N) in the first stage and 136.5 kgf (1339 N) in the second stage. 51.9 kgf (509 N) in the direction opposite to the axial thrust force).

Therefore, in this canned motor pump,
49.1-51.9 = 2.8 kgf (27.5 in total)
N) and a very small residual axial thrust force.

<Case where penetration of second-stage impeller is smaller than first-stage impeller> This is the case of the canned motor pump according to the embodiment of the present invention shown in FIG. 3, and the first-stage and second-stage impellers The outer diameter is the same, the first stage lift: 100 m The outer diameter D2 of the impeller 31 = 8.7 cm, the inner diameter Dr of the mouthpiece is 5 cm, the thickness of the boss Db = 3.3 cm, the penetration part Db1 of the first stage is 3.3 cm, the second stage Lifting height: 100 m Outer diameter D2 of the impeller 32 = 8.7 cm Inner diameter Dr of the mouthpiece = 5 cm, thickness of the boss Db = 2 cm 2nd penetration part Db2 = 2 cm

The residual axial thrust force at the shaft end is 31.4 kgf (308 N) due to the change in the area, which is 17.7 kgf (174 N) compared to the case where the same impeller is used.
N). The axial thrust force at the impeller was 63.6 kgf (624 N) in the first stage and 9 in the second stage.
4.7 kgf (929 N), and in the second stage direction (the direction opposite to the residual axial thrust force at the shaft end) by deduction.
A force of 1 kgf (305 N) acts.

Therefore, in this canned motor pump,
Overall, 31.4-31.1 = 0.3 kgf (2.9
N) and a very small residual axial thrust force.

<In the case where the number of stages on the high pressure side is increased> This is the case of the canned motor pump according to the embodiment of the present invention shown in FIG. 4, in which the low pressure side is one stage of the impeller 41 and the high pressure side is the impeller 42. , 43, so that a total of three stages are provided, and the head of each stage is 66.7 m.

First stage head of the low pressure part: 66.7 m Outer diameter D2 of impeller 41 = 7.1 cm Inner diameter Dr of cap = 4.5 cm, thickness of boss Db = 2.7
cm Second stage head of high-pressure part: 66.7 m Outer diameter D2 of impeller 42 = 7.1 cm Inner diameter Dr of cap = 4.5 cm, thickness of boss Db = 2.7
cm Third stage head of high pressure part: 66.7 m Outer diameter D2 of impeller 43 = 7.1 cm Inner diameter Dr of cap = 4.5 cm, thickness of boss Db = 2.7
cm 2.

The residual axial thrust force at the shaft end is 38.2.
kgf (375 N). The axial thrust force generated at each stage of the impeller is 40.2 kgf (394 N).
The first stage of the low-pressure section and the second stage of the high-pressure section are canceled, and the residual shaft thrust force generated in the impeller section is generated in the third stage, and 40.2 kgf (394 N) is applied in the direction of the high pressure section (the residual shaft at the shaft end). Acting in the direction opposite to the thrust force).

Therefore, in this canned motor pump,
38.2-40.2 = 2kgf (19.6N) in total
And a very small residual axial thrust force.

[0040]

As described above, according to the present invention, the outer diameter of the impeller at the high pressure side end is made larger than the outer diameter of the impeller at the low pressure side end, or the suction port diameter of the impeller at the high pressure side end is reduced to the low pressure side. That it is larger than the suction diameter of the impeller at the end,
Alternatively, the penetrating portion of the impeller at the high pressure side end is made smaller than the penetrating portion of the impeller at the low pressure side end, or the number of steps of the impeller at the high pressure side end is made larger than the number of steps of the impeller at the low pressure side end. Since the thrust force can be made extremely small, the pressurized circulation type canned motor pump should be small, high-yield, inexpensive and reliable without making a balance hole in the first stage. Can be.

According to the present invention, any residual shaft thrust can be held in any direction. For example, when an inducer needs to be mounted, the shaft thrust force generated by the inducer can be maintained. Can also be canceled.

Further, in the above-described embodiment, a horizontal canned motor pump has been described. However, when a vertical canned motor pump is required for installation space, the own weight of the rotating body acts as a residual axial thrust force. According to this, the residual axial thrust force due to this own weight can also be canceled.

Further, when it is desired to increase the amount of internal circulation to suppress a rise in temperature, the residual axial thrust force due to the internal circulation becomes a problem. According to the present invention, however, the internal circulation can be increased without any problem. You can design.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a structure of a canned motor pump according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a structure of a canned motor pump according to another embodiment of the present invention.

FIG. 3 is an explanatory view showing a structure of a canned motor pump according to another embodiment of the present invention.

FIG. 4 is an explanatory view showing a structure of a canned motor pump according to another embodiment of the present invention.

FIG. 5 is an explanatory view showing an example of the structure of a conventional canned motor pump.

6 is an explanatory diagram for explaining a residual shaft thrust force in the canned motor pump shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Rotation shaft 2 Internal circulation channel 11, 12, 21, 22, 31, 32, 41, 42, 4
3, 51, 52 Impeller T1 Residual axial thrust force

Claims (4)

[Claims] At least one impeller is disposed at each end of a rotating shaft in opposite directions, a main flow path is provided from a low pressure side end to a high pressure side end, and from a high pressure side end impeller to a low pressure side end impeller. In a pressurized circulation type canned motor pump having an internal circulation flow path and a rotor disposed in the internal circulation flow path, the outer diameter of the impeller at the high pressure side end is larger than the outer diameter of the impeller at the low pressure side end. A canned motor pump characterized by a larger size. 2. The canned motor pump according to claim 1, wherein a suction opening of the impeller at the high pressure side end is larger than a suction opening of the impeller at the low pressure side end. 3. The canned motor pump according to claim 1, wherein a penetrating portion (impeller boss) of the impeller at the high pressure side end is smaller than a penetrating portion (impeller boss) of the impeller at the low pressure side end. . 4. The canned motor pump according to claim 1, wherein the number of stages of the impeller at the high pressure side end is larger than the number of stages of the impeller at the low pressure side end.