WO2006061914A1

WO2006061914A1 - Inducer and pump

Info

Publication number: WO2006061914A1
Application number: PCT/JP2004/018676
Authority: WO
Inventors: Kosuke Ashihara
Original assignee: Ebara Corporation
Priority date: 2004-12-08
Filing date: 2004-12-08
Publication date: 2006-06-15

Abstract

An inducer in which the number of vanes at an inlet is one and the number of vanes at an outlet is three, the gravity center of an entire blade is positioned on the rotating axis thereof to prevent a rotational unbalance from occurring, and both suction performance and boosting performance are excellent and a pump having the inducer. The inducer (8) comprises three vanes (1-1), (1-2), and (1-3) disposed on the upstream side of a main impeller (7) and having lengths along the vanes different from each other. The three vanes (1-1), (1-2), and (1-3) are disposed so that the positions of the leading edges (1-1a), (1-2a), and (1-3a) of the three vanes (1-1), (1-2), and (1-3) in meridian planes are different from each other.

Description

Description Inducer and Pump Technical Field

The present invention relates to an inducer and a pump. In particular, in order to improve the suction performance of the pump, the inductor disposed on the upstream side of the main impeller so that the rotation axis coincides with the rotation axis of the main impeller. The present invention relates to a reducer and a pump equipped with the inducer. Background art

When the pump is operated at a low suction pressure or at a flow rate greater than the rated pressure, the liquid pressure locally falls below the saturated vapor pressure in the pump flow path, and the pump impeller (hereinafter referred to as the main impeller) Cavitation may occur in the flow path. If cavity is generated in the main impeller flow path, the flow path may be blocked by the cavity bubbles and the pump may not be able to pressurize.

The difference between the total pressure at the inlet of the pump and the saturated vapor pressure represents a margin for pump cavity generation, and this pressure difference is called NPSH (Net Positive Suction Head). The pump suction performance is evaluated by this N P S H, and a pump that has a boosting performance even with a low N P S H is said to have high suction performance. If the pump suction performance is high, the pump can be operated at high speed and the pump can be downsized.

Conventionally, an inducer has been attached to the tip of the main shaft to improve pump suction performance. This inducer is arranged on the upstream side of the main impeller such that the main impeller and the rotation axis are the same, and is rotated at the same rotational speed as the main impeller via the main shaft. The inducer is a mixed flow type or axial flow type impeller having a plurality of blades, and has a shape characteristic that the number of blades is smaller and the blade length is longer than the main impeller.

Because of these geometric features, liquid pressure drops upstream of the blade inlet and Even in the case of occurrence of a phenomenon, the flow path of the inducer is not easily blocked, and the pressure of the liquid can be increased. For this reason, by arranging the inducer upstream of the main impeller, the pump suction performance can be improved compared to the case of the main impeller alone, and the pump can be increased in speed and size. Become. The suction performance of a pump with an inducer increases as the suction performance and pressure increase performance of the inducer increase. Figures 1A and 1B show a conventional inducer with three blades. As shown in Fig. 1A and Fig. 1B, three wings of helical shape (spiral shape) 1 1-1, 1 1-2, 1 1-3 (hereinafter collectively referred to as wing 1 1) Is fixed to the outer peripheral surface of the cylindrical or columnar shaft portion 5. The lengths of these wings 11 along the wings are all equally configured. In general, inducers are designed to achieve high suction performance, so it is preferable to reduce the number of inducer blades as much as possible. Since an inducer with only one blade has a problem of rotational balance, the number of blades of a normal inducer is 2 to 5 blades. Also, inductors with an even number of blades may cause alternate blade cavityation, so a three-blade inducer is generally preferred. A general design guideline regarding the number of blades of such a conventional inducer is described in the following document 1. Document 1:. NASA SP- 8052, Liquid Rocket Engine Turbopump Inducers, NASA SPACE VEHICLE DESIGN CRITERIA N the United States, NASA (National Aeronautics and Space Administration ) x -1 9 9 7 March 2009 ...

Generally, the boosting performance of an inducer increases as the number of blades of the inducer increases. On the other hand, since the suction performance of the inducer increases as the number of blades decreases, the boosting performance and suction performance of the inducer are in a trade-off relationship. If the inducer requires high suction performance and high boosting performance at the same time due to the pump specifications, an inducer with an intermediate blade may be used.

An inducer with an intermediate wing has an intermediate wing that is shorter than the entire wing in a flow path formed between the wings of the normal length (full wing). The rear wing of the intermediate wing is in the same position as all wings on the meridian plane, but the leading edge of the intermediate wing is located downstream of the leading edge of all wings. Therefore, an inducer with an intermediate blade has a feature that the number of blades is small at the inlet and the number of blades is large at the outlet. With this, with the middle wing The inducer has a high suction performance because it has a wider inlet channel and is less likely to be blocked by cavity bubbles, compared to an inducer with all blades. In addition, the inducer with intermediate blades has high boosting performance due to the large number of blades at the outlet. Document 2 shows that pump impellers with intermediate blades have higher suction performance than pump impellers without intermediate blades.

Reference 2: Kosuke ASHIHARA and Akira GOTO, STUDY ON PUMP IMPELLER WITH SPLITTER BLADES DESIGNED BY 3-D INVERSE DESIGN METHOD, FEDSM2000-11073. USA, ASME, June 2000

As another example of a pump impeller with an intermediate blade, Document 3 discloses an impeller for a sewage pump with one full blade and one intermediate blade. When the impeller is projected onto a plane perpendicular to the rotation axis, the trailing edge of the intermediate blade (sub blade) is more rotational than the symmetrical position around the rotation axis of the trailing edge of all blades (main blade). It is in the position shifted. This impeller for sewage pumps has one inlet blade to prevent clogging of the inlet due to dirt, and two outlet blades to make the pump efficiency practically sufficient. is there. Since the center of gravity of these intermediate wings and all wings are all separated from the rotation axis, the rotation balance cannot be obtained with only the middle wing and all wings.

Reference 3: Japanese Patent Laid-Open No. 2 0 0 1-2 8 9 1 9 3 Disclosure of Invention

A two-blade type inducer can be considered as an inducer that can achieve high suction performance. However, this type of inducer can be expected to have a high suction performance due to the small number of blades at the inlet, but the boosting performance is low due to the small number of blades at the outlet. On the other hand, an inducer with an intermediate blade that can be expected to have a high suction performance and a high pressure boosting performance always has an even number of blades due to its shape characteristics, and the minimum number of blades in an inducer used in an actual pump. A total of 4 blades, 2 for each wing and 2 for the middle wing.

Fig. 2A and Fig. 2B show an inducer with a conventional intermediate wing that has two full wings and two intermediate wings. As shown in Fig. 2A and Fig. 2B, the intermediate blades 1 2-1, 1 2-2 (hereinafter collectively referred to as the intermediate blade 1 2) are all blades 1 1-1, 1 1-2 (Hereinafter collectively referred to as all blades 1 1) are located at the center in the circumferential direction of the rotation axis, and the length of the intermediate blade 1 2 is the length of all blades 1 1 Half a minute. The trailing edge 1 2— 1 a, 1 2— lb on the meridian plane 1 2 is the same as the trailing edge 1 1 1 lb, 1 1— 2 b of the entire wing 1 1, but the intermediate wing 1 2 The leading edge 1 2-1 a, 1 2— 2 a is located downstream of the leading edge 1 1— la, ll _ 2 a of the entire wing 1 1. This inducer with intermediate blades has two inlet blades and four outlet blades, so the inlet is wide, so high suction performance can be achieved, and high boosting performance can be achieved.

In order to further improve the suction performance of these two blades + two intermediate blades, it is necessary to reduce the number of blades at the inlet and expand the inlet of the flow path. As an inducer with such a wide channel inlet, one type of inducer with one full blade and one intermediate blade can be considered. However, in the case of this type of inducer, the center of gravity of the entire blade is not on the axis of rotation, causing rotation imbalance and making the pump difficult to operate.

From these viewpoints, in order to achieve high suction performance and high boosting performance,

(1) The number of blades at the entrance is as small as possible,

(2) The number of exit wings is as large as possible,

(3) The center of gravity of the wing is on the axis of rotation and no rotation fan balance occurs.

An inducer with such a new structure is desired ^

The present invention has been made in view of such problems of the prior art. The number of blades at the inlet is one, the number of blades at the outlet is three, and the center of gravity of the entire blade is on the rotating shaft. It is an object of the present invention to provide an inducer excellent in both suction performance and boosting performance that does not cause a balance, and a pump equipped with such an inducer.

In order to solve the above problems in the prior art, the present invention is an inducer disposed on the upstream side of a main impeller, and includes three blades having different lengths along the blades. The positions of the leading edges of the wings on the meridian plane are different from each other.

In a preferred aspect of the present invention, the trailing edge positions of the three blades are aligned with each other on the meridian plane. In a preferred aspect of the present invention, the trailing edges of the three blades are uniformly arranged around the rotation axis in a plane perpendicular to the rotation axis.

In a preferred aspect of the present invention, the three wings are composed of a first wing, a second wing, and a third wing, and a winding angle from a trailing edge of the first wing is 2 3 0 + A to 2 5 0 + A. The winding angle from the trailing edge of the second wing is 1 1 0 + A to 1 3 0 + A °, and the winding angle from the trailing edge of the third wing is A ° (However, A represents a constant satisfying the condition 0 <A).

When the wing angle at the same meridional position of the three wings and the distribution of the wing angle with respect to the meridional position are different from each other, by adjusting the winding angle of the three wings within the above range, The center of gravity can be made to coincide with the rotation axis, and the rotation balance can be achieved. The winding angle is the center angle of the wing centered on the rotation axis from the trailing edge to the leading edge.

One example included in the present invention described above is shown below. For three wings, if the wing angle is constant regardless of meridional position and all wing angles are the same,

The firing angle from the trailing edge of the first wing is 2 4 0 + A °,

The firing angle from the trailing edge of the second wing is 1 2 0 + A °,

The winding angle from the trailing edge of the third wing can be A °.

In this relationship, the center of gravity of all three blades coincides with the rotational axis, and the rotational balance can be achieved. Here, A is a constant common to the three blades, and any value can be selected within the range of 0 <A.

In the inducer of the present invention, the lengths of the three wings along the wings are different, so there are one wing at the entrance, two wings at the center, and three wings at the exit. . Furthermore, when the wing angle of each blade relative to the position of the trailing edge satisfies the above relationship, the center of gravity of the three blades is positioned on the rotation axis.

According to the inducer of the present invention, since the number of blades at the inlet is one, even if a cavity bubble is generated on the suction surface near the inlet of the first blade, the flow path on the suction surface side at the inlet of the inducer Has a wide opening angle of 3600 °, and the inlet of the inducer is not easily blocked. Here, the opening angle is the channel breakage around the rotation axis. The center angle of a surface, which represents the size of the space between adjacent wings. Due to the pressure increase of the first blade, the cavitation bubbles generated on the suction surface of the second blade are smaller than those of the first blade, and the flow angle on the suction surface side also has an opening angle of 2400 °. And because it is wide, it is difficult to be blocked by bubbles. In the third wing, the opening angle of the flow path on the suction side is 120 °, but the cavity bubbles generated in the third wing by the pressurizing action of the first wing and the second wing are even smaller. Therefore, the possibility of blockage is low.

Thus, the inducer of the present invention having the above-described configuration has a high suction performance, and the number of blades at the inducer outlet is three, so that it has a sufficiently high boosting performance in practice. In addition, since the center of gravity of all three blades is on the rotation axis, there is no problem of rotational unbalance. Therefore, the inducer having the above configuration has the characteristics of high suction performance, high boosting performance, and no rotation imbalance.

Another aspect of the present invention is a pump comprising a main impeller housed in a casing, a main shaft to which the main impeller is fixed, and the inducer.

Since the inducer described above has a high suction performance and a high pressure increase performance, the suction performance of a pump including this inducer can be improved. Therefore, it is possible to increase the speed and size of the pump.

From another point of view, the present invention can be said to have solved the contradictory proposition regarding the number of blades of the inducer. In other words, the number of inducer blades should be reduced from the viewpoint of achieving high suction performance by avoiding blockage of the flow path due to cavity bubbles, but the number of blades will be increased from the point of achieving high boosting performance. Should. In the present invention, such a contradictory proposition can be satisfactorily solved with extremely high effects by using three wings having different lengths from each other rather than simply compromising both performances.

In the present invention, it is preferable that the positions of the trailing edges of the blades on the meridional surface are aligned with each other. However, the displacement of the positions of the trailing edges of the blades is an excellent object of the present invention. It does not immediately affect the suction performance and boost performance. As described above, the inducer of the present invention has high suction performance and high boosting performance, and does not cause rotation imbalance. Therefore, the inducer of the present invention The pump arranged on the upstream side of the main impeller can exhibit higher suction performance than conventional pumps, and can contribute to speeding up and downsizing of the pump. Brief Description of Drawings

FIG. 1A is a perspective view showing a conventional inducer having three blades, and FIG. 1B is a side view of the inducer shown in FIG. 1A.

FIG. 2A is a perspective view showing a conventional inducer with intermediate blades having two full blades and two intermediate blades, and FIG. 2B is a side view of the inducer shown in FIG. 2A.

FIG. 3 is a cross-sectional view schematically showing a pump provided with an inducer according to an embodiment of the present invention.

4A is a side view showing an inducer according to an embodiment of the present invention, FIG. 4B is a perspective view of the inducer according to an embodiment of the present invention, and FIG. 4C is an embodiment of the present invention. It is another perspective view of the inducer which concerns on a form.

FIG. 5 is a schematic diagram showing the first wing, the second wing, and the third wing on the meridian plane of the inducer according to the embodiment of the present invention.

FIG. 6A is a perspective view showing a first wing according to an embodiment of the present invention, and FIG. 6B is a plan view showing the first wing.

FIG. 7A is a perspective view showing a second wing according to an embodiment of the present invention, and FIG. 7Bj is a plan view showing the second wing.

FIG. 8A is a perspective view showing a third wing according to an embodiment of the present invention, and FIG. 8B is a plan view showing the third wing.

Fig. 9 is a schematic diagram showing the occurrence of cavitation in a conventional inducer with three blades.

FIG. 10 is a schematic diagram showing a state of occurrence of cavitation in a conventional inducer having two full blades and two intermediate blades.

FIG. 11 is a schematic diagram showing a cavitation occurrence state of an inducer according to an embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an inducer according to the present invention and a pump including the inducer will be described with reference to the drawings.

FIG. 3 is a cross-sectional view schematically showing a pump provided with the inducer of the present invention. As shown in FIG. 3, the pump has a main impeller (pump impeller) 7 accommodated in a casing 6, an inducer 8 according to the present invention, a main impeller 7 and an inducer 8 fixed thereto. Main shaft 9 is provided. Seal members 10 A and 10 B for preventing the pressurized fluid from leaking from the high pressure side to the low pressure side are respectively provided on the upstream side and the downstream side of the main impeller 7.

The inducer 8 is arranged upstream of the main impeller 7 so that the rotation axis (the central axis of the main shaft 9) is the same as that of the main impeller 7, and the main impeller is driven via the main shaft 9 by a drive source (not shown). It rotates at the same rotational speed as car 7. The fluid (liquid) flows in from the suction port 6a, is pressurized by the inducer 8 while generating a cavity, and further boosted by the main impeller 7 to the extent that the required pump head is obtained. At this time, because the inducer 8 is boosting the fluid up to a pressure at which no cavity is generated in the main impeller 7, the suction performance of the pump is improved as compared with the case of the main impeller 7 alone.

4A to 4C show in detail an inducer according to an embodiment of the present invention. 4A is a side view of an inducer according to an embodiment of the present invention, FIG. 4B is a perspective view of an inducer according to an embodiment of the present invention, and FIG. 4C is an embodiment of the present invention. It is another perspective view of the inducer which concerns on. FIG. 5 is a schematic diagram showing the first wing, the second wing, and the third wing on the meridian plane of the inducer according to the embodiment of the present invention.

As shown in FIGS. 4A to 4C, the inducer in this embodiment includes a cylindrical or cylindrical shaft portion 5 and three blades 1 fixed to the outer peripheral surface of the shaft portion 5. I have. The first wing 1 is composed of the first wing 1-1, the second wing 1 1-2, and the third wing 1-3 (hereinafter collectively referred to as wing 1). . As shown in Fig. 5, the lengths of the first wing 1 1, the second wing 1-2, and the third wing 1 1 3 are different from each other. 1 a, 1—2 a, 1— 3 a child The positions on the meridian plane are different from each other. Also, the trailing edge of wing 1 on the meridian plane 1 — lb, 1-2 b, 1-3 b is in the same position.

As shown in Fig. 4C, in the plane perpendicular to the rotation axis (the central axis of the shaft part 5), the trailing edges of the three blades 1 at the inducer exit 1 1 1 b to l— 3 b They are evenly spaced at 120 ° intervals around the center. In addition, the rolling angles from the trailing edges of the three wings 1 are set as follows.

First wing 1-1: 240 + A °

2nd wing 1 1 2: 120 + A °

Third wing 1 1 3: A °

However, A is a constant common to the three blades 1 and represents a value larger than 0. Here, the roll angle is the center angle of the wing centered on the axis of rotation from the trailing edge to the leading edge. The winding angle of the first blade 1-1 may be 230 + A to 250 + A °, and the winding angle of the second blade 1-2 is 1 10 + Α to 130 + A °. If there is.

FIG. 6A is a perspective view showing a first wing according to an embodiment of the present invention, and FIG. 6B is a plan view showing the first wing. FIG. 7A is a perspective view showing a second wing according to an embodiment of the present invention, and FIG. 7B is a plan view showing the second wing. FIG. 8A is a perspective view showing a third wing according to an embodiment of the present invention, and FIG. 8B is a plan view showing the third wing.

As shown in FIG. 6B, FIG. 7B, and FIG. 8B, in this embodiment, the constant A is set to 120, and the blades from the trailing edges 1—1 b to l_3 b of the three blades 1 are scattered. The angles are set as follows.

1st wing 1 1 1: 360 °

Second wing 1—2: 240 °

Third wing 1-3: 120 °

With such an arrangement, the inducer of the present embodiment is configured with one wing at the inlet, two wings at the center, and three wings at the outlet.

The constant A mentioned above is preferably 60≤A≤180. If A is 60, the length of the third wing 1-3 is too short to expect pressure boosting performance. Meanwhile, 180 <A If this is the case, the flow paths formed between the three blades 1 will be too long, and the resistance of the fluid will increase and the pressurizing performance will decrease.

As shown in FIG. 7B and FIG. 8B, the winding angle of the second blade 1 1 2 is 2400 °, the winding angle of the third blade 1 1 3 is 1 20 °, and the second blade The positions of the trailing edges 1 1 2 b and 1 _ 3 b of 1 1 2 and the third wing 1 1 3 are shifted from each other by 120 °. From this, the total winding angle of the second wing 1 _ 2 and the third wing 1-3 is the same as the winding angle of the first wing 1 1 1 3 60 °, and the second The center of gravity when the wings 1 and 2 and the third wings 1 and 3 are combined is located on the axis of rotation. 1st wing 1 1 1 The winding angle is 3 6 0. Therefore, since the center of gravity of the first wing 1-1 1 is on the axis of rotation, the overall center of gravity of the first wing 1-11, the second wing 1-2, and the third wing 1-3 also rotates. Will be on the axis. Accordingly, the rotation balance of the inducer according to the present embodiment is balanced. In this way, the leading edges of each blade 1 — 1 a to 1 1 3 a are shifted from each other by 120 °, so that the entire blade 1 can be increased or decreased by the same firing angle in each blade 1. The center of gravity is on the axis of rotation. Therefore, even if the above-described constant A is an arbitrary value, the center of gravity of the entire blade 1 is located on the rotation axis, and a rotation balance can be obtained.

Hereinafter, FIG. 9 to FIG. 11 show the state of occurrence of the oscillation of the inducer according to one embodiment of the present invention and the conventional inducer. Figures 9 to 11 show the wings of the inducer. In Fig. 9 to Fig. 11, the first wing is shown overlapping on both the left and right sides to make the flow path easy to understand, but in reality there is only one first wing.

Fig. 9 is a schematic diagram showing the state of occurrence of cavitation in the conventional inducer shown in Fig. 1 having three all blades. In this type of inducer, an interval of a size corresponding to an opening angle of 120 ° is formed between the blade 1 1−2 and the adjacent blade 1 1−3. Here, the opening angle refers to the central angle of the cross section of the flow channel centered on the rotation axis, and represents the size of the interval between adjacent blades. When the pressure upstream of the inlet decreases, cavitation bubbles 20 are generated on the suction surface of the blades 1 1 1 1 to 1 1 1 3 near the inlet. When a cavity bubble 20 having a certain size is generated, the flow path is closed. In terms of boosting performance, the number of blades at the exit is three, so this type of index Yousa has higher boosting performance than the two-blade type inducer.

FIG. 10 is a schematic view showing the state of occurrence of cavitation in the conventional inducer shown in FIG. 2 having two full blades and two intermediate blades. Since the number of blades at the inlet of this type of inducer is two, there is a gap between each blade 1 1 1 1 and the next blade 1 1—2 that corresponds to an opening angle of 1800 °. Is formed. Therefore, even if cavitation bubbles 20 are generated on the suction surface of all blades 11 near the inlet, the flow path is wider than that of the inducer (three blades type) shown in FIG. Cavitation bubbles generated on the suction surface of the intermediate blade 1 2 near the inlet

The size of 30 is smaller than the size of the cavity bubble 20 generated on the suction surface of all blades 11 because of the pressure increasing action by all blades 11. However, the opening angle between the adjacent intermediate blades 12 and all blades 11 is 90 °, and the flow path on the suction surface side of the intermediate blades 12 is relatively narrow. For this reason, if the cavity bubble 30 generated on the suction surface of the intermediate blade 12 is large to some extent, the flow path on the suction surface side of the intermediate blade 12 is likely to be blocked. Regarding the boosting performance, the number of blades at the outlet is four, so the inducer shown in Fig. 10 has higher boosting performance than the inducer shown in Fig. 9 (all third blade type).

FIG. 11 is a schematic diagram showing a cavitation occurrence state of an inducer according to an embodiment of the present invention. As shown in FIG. 11, since the number of blades at the inlet of the inducer according to the present embodiment is one, the opening angle at the inlet is 3.60 °. Therefore, even if a cavity bubble 20 occurs on the negative BE surface of the first wing (all wings) 11 near the entrance, it is difficult to block because the flow path is very wide. The size of the cavity bubble 30 generated on the suction surface near the inlet of the second blade 1-2 is generated on the suction surface of the first blade 1-1 due to the pressurizing action of the first blade 1-1. Cavitation bubbles to be smaller. In addition, the flow path on the suction surface side of the second blades 1 and 2 has a relatively large opening angle of 2400 degrees with the adjacent first blade 1 and 1, so this flow path is also very blocked. Hateful.

Cavitation bubbles generated on the suction surface near the inlet of the third wing 1-3

The size of 40 is smaller than the cavitation bubble 30 generated on the suction surface of the second blade 1-2 because of the pressurizing action of the first blade 1-11 and the second blade 1-2. In addition, the flow path on the suction surface side of the third blades 1 to 3 has a large opening angle with the adjacent first blade 11 to 1120 °, so this flow path is also difficult to block. Regarding the boosting performance, since the number of blades at the outlet is three, the inducer according to the present embodiment has a high boosting performance equivalent to the inducer (all blades three-blade type) shown in FIG. According to the above configuration, the inducer of the present invention has a high suction performance and a high boosting performance, and does not cause rotation imbalance.

In the above embodiment, the attachment positions of the three blades 1 with respect to the rotation shaft (shaft portion 5) are uniform in the circumferential direction of the rotation shaft. That is, the trailing edges 1 lb to 1 3 b of the three blades 1 are separated from each other by 120 ° as center angles around the rotation axis in a plane perpendicular to the rotation axis. They are arranged at equal intervals and are mounted so that the positions of the trailing edges 1 1 1 b to 1 3 b of the three blades 1 are the same on the meridian plane. However, as described above, the present invention includes three wings 1 having different lengths, and the leading edges of these wings 1 are different from each other on the meridian plane of 1a-1_3_a. Therefore, the trailing edges 1— lb to 1-3 b of each blade 1 do not necessarily have to be evenly installed around the axis of rotation at intervals of 120 °, The positions of the trailing edges 1 1 1 b to 1 3 b on the meridian do not have to be aligned. However, it is the indexer shown in the above-described embodiment that can reliably rotate the three blades of different lengths and can best exhibit the effects of the present invention. -. Possibility of industrial use

In order to improve the suction performance of the pump, the present invention includes an inducer disposed on the upstream side of the main impeller so that the rotation axis coincides with the rotation axis of the main impeller, and the inducer. Available for pumps.

Claims

The scope of the claims

1. In the inducer located upstream of the main impeller,

An inducer comprising three wings having different lengths along the wing, wherein the positions of the leading edges of the three wings are different from each other.

2. The inducer according to claim 1, wherein the trailing edge positions of the three blades are aligned with each other on the meridian plane.

3. The integrator according to claim 1 or 2, wherein the trailing edges of the three blades are evenly arranged with the rotation axis as a center in a plane perpendicular to the rotation axis. . ,

4. The three wings are composed of a first wing, a second wing, and a third wing, and a winding angle from a trailing edge of the first wing is 230 + A to 250 + A. The winding angle from the trailing edge of the second wing is 1 10 + A to 130 + A °, and the winding angle from the trailing edge of the third wing is A °

(However, A represents a constant that satisfies 0 and A)

The inducer according to any one of claims 1 to 3.

5. a main impeller housed in a casing;

A main shaft to which the main impeller is fixed;

A pump comprising the inducer according to any one of claims 1 to 4.