inducer

Abstract

To provide an inducer.SOLUTION: An inducer of the present invention comprises: a shaft body disposed to be rotatably driven; and a plurality of blades disposed in a multi-row spiral shape on an outer peripheral surface of the shaft body, and whose leading edges in a circumferential direction, as viewed in an axial direction from an uppermost stream side, are displaced from each other in the circumferential direction. On each of the blades, a cut part that is opened to an outer edge other than the leading edge in a radial direction, and which is located on a downstream side in a counterclockwise direction from an outer peripheral end of the leading edge of each of the blades as viewed in the axial direction from the uppermost stream side, and extended shorter than an opening width to an inner side in the radial direction, is formed in a symmetrical position around a central axis of the shaft body as viewed in the axial direction from the uppermost stream side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an inducer. [Background technology]

[0002] In high-speed rotary pumps such as those used in rocket engine turbopumps, cavitation occurs at the pump inlet, causing poor suction and making it impossible to efficiently pressurize and transport the liquid. To address this issue, a spiral auxiliary impeller called an inducer, which has excellent suction performance, has traditionally been attached in front of the pump's main impeller to ensure stable pressurization and transport of the liquid. In this type of inducer, unstable phenomena associated with cavitation (such as rotating cavitation and cavitation surge) and asymmetric phenomena (asymmetric sticking cavitation) can occur, causing problems such as flow rate and pressure fluctuations. When flow rate and pressure fluctuations occur, they can, in some cases, increase instability in pump performance, leading to problems such as blade fatigue failure and shaft vibration.

[0003] For this reason, in the technical field of rocket engine turbopumps, various techniques have been proposed to suppress the unstable and asymmetric phenomena that accompany cavitation in the inducer. For example, Patent Document 1 below describes a configuration in which a notch or a through hole is provided in an inducer blade for the purpose of improving suction performance, Patent Document 2 describes a configuration in which a number of slits are provided, and Patent Document 3 describes a configuration in which a step is provided on the outer periphery of the blade. Patent Document 4 below describes a splitter vane in which the leading edges of three rotor blades are arranged at different positions in the meridian plane and the trailing edges of the three rotor blades are arranged so as to be aligned in the meridian plane. Patent Document 5 describes an inducer equipped with an asymmetric blade having a primary blade and a splitter vane. Patent Document 6 below describes an inducer in which a notch is provided on the tip side (outer periphery) of the rotor blade that is radially longer than the opening width and extends to one side in the radial direction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 54-057503 [Patent Document 2] Japanese Patent Application Publication No. 58-055003 [Patent Document 3] Patent No. 4556465 [Patent Document 4] Patent No. 4503264 [Patent Document 5] Special Publication No. 2007-514091 [Patent Document 6] Patent Publication No. 2021-011840 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned conventional techniques have the following problems. Inducers require a configuration that can be manufactured with simple processing, but the technology of Patent Document 2 requires the processing of many slits, and the technologies of Patent Documents 4 and 5 require the special production of splitter blades and asymmetric blades, and in either case, there is a problem that the processing is not easy.

[0006] Inducers must effectively suppress problems such as instability and shaft vibration, while also ensuring head performance (pressure-boosting capacity) and suction performance (ability to suck in low-pressure fluid). For this reason, the notches, introduction holes, and multiple slits described in Patent Documents 1 to 3 must be provided in appropriate positions and with appropriate sizes. However, Patent Documents 1 to 3 have a problem in that they do not disclose the desirable formation positions and sizes associated with the above-mentioned head performance and suction performance. If the above-mentioned notches, introduction holes, etc. are not provided in appropriate positions and with appropriate sizes, there is a concern that head performance and suction performance will decrease. The asymmetric blade described in Patent Document 5 has a problem in that the asymmetry of the blade itself causes the cavitation generation state to become asymmetric, which inevitably increases shaft vibration. Although there is a demand for lighter inducers, the technology of Patent Document 4 requires the addition of a separate splitter blade, which results in an increase in weight.

[0007] The present invention has been made in consideration of the problems of the above-mentioned conventional technology, and aims to provide an inducer with a simple configuration that can suppress the expansion and contraction of cavitation and suppress instability phenomena by providing cutouts of an appropriate shape at appropriate positions on the blades. [Means for solving the problem]

[0008] The inducer according to this embodiment includes a shaft that is rotatably driven, and a plurality of blades that are spirally arranged on the outer peripheral surface of the shaft, and whose leading edges in the circumferential direction are shifted from each other in the circumferential direction when viewed in the axial direction from the most upstream side. Each of the blades has an opening at its outer edge in the radial direction excluding the leading edge, and is positioned counterclockwise from the outer peripheral end of the leading edge of each of the blades when viewed in the axial direction from the most upstream side. do The notches are formed at symmetrical positions about the central axis of the shaft when viewed from the most upstream side in the axial direction. In a graph in which the notch has a width (b) and a depth (h), the horizontal axis shows the relative ratio (b / DM) of the width (b) to the diameter (DM) of the blade, and the vertical axis shows the relative ratio (h / DM) of the depth (h) to the diameter (DM), point A 1 (0.039,0.197), point A 2 (0.118,0.270), point A 3 (0.158,0.197), point A 4 (0.178,0.132), point A 5 (0.178,0.066), point A 6 (0.132, 0.039) in the relationship between the width and depth of the notch, the relative ratio of the width and depth to the diameter is point A on the graph. 1 , point A 2 , point A 3 , point A 4 , point A 5 , point A 6 The present invention is characterized in that the range is enclosed by the arrows. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an inducer with a simple configuration that can suppress unstable phenomena caused by cavitation while maintaining suction performance. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram illustrating a configuration example of a turbopump including an inducer according to an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic front view illustrating an example of an inducer according to an embodiment of the present invention. [Figure 3] FIG. 2 is a schematic side view illustrating an example of an inducer according to an embodiment of the present invention. [Figure 4] FIG. 3 is a schematic enlarged view showing an example of the configuration of a notch in the inducer according to the embodiment of the present invention. [Figure 5] 1A and 1B are schematic diagrams illustrating an example of a cavitation instability phenomenon. [Figure 6] FIG. 10 is a schematic enlarged view showing an example of the configuration of a slit in an inducer of a comparative example. [Figure 7] 10 is a graph showing the cavitation number obtained when the notch provided in the inducer blade is formed at the same position as in the comparative example, the depth is fixed, and the width is changed within a range of 0 to 60 mm. [Figure 8] 10 is a graph showing the cavitation number obtained when the formation position of the notch provided in the inducer blade is set to the example position, the depth is set to 5 mm, and the width is changed in the range of 0 to 35 mm. [Figure 9] 10 is a graph showing the cavitation number obtained when the notch provided in the inducer blade is formed at the example position, the depth is set to 10 mm, and the width is changed within the range of 0 to 35 mm. [Figure 10] 10 is a graph showing the cavitation number obtained when the notch provided in the inducer blade is formed at the example position, the depth is set to 20 mm, and the width is changed within the range of 0 to 35 mm. [Figure 11] 10 is a graph showing the cavitation number obtained when the formation position of the notch provided in the inducer blade is set to the example position, the depth is set to 22.5 mm, and the width is changed in the range of 0 to 35 mm. [Figure 12]10 is a graph showing the cavitation number obtained when the notch provided in the inducer blade is formed at the example position, the depth is set to 25 mm, and the width is changed within the range of 0 to 35 mm. [Figure 13] 10 is a graph showing the cavitation number obtained when the notch provided in the inducer blade is formed at the example position, the depth is set to 27.5 mm, and the width is changed within the range of 0 to 35 mm. [Figure 14] 10 is a graph showing the range in which asymmetric cavitation can be completely suppressed when the formation position of the notch provided in the inducer blade is set to the example position and the width and depth are changed within the range of 0 to 35 mm. [Figure 15] This shows some of the results of a demonstration experiment on an inducer, where (A) is a graph showing a first example of the frequency analysis results (Q / Qd=1.175) of pressure fluctuations at the slit formation position in the embodiment, and (B) is a graph showing a second example of the frequency analysis results (Q / Qd=1.175) of the same pressure fluctuations. [Figure 16] This shows some of the results of a demonstration experiment on an inducer, where (A) is a graph showing a first example of the frequency analysis results (Q / Qd=1.175) of pressure fluctuations at the slit formation position of the comparative example, and (B) is a graph showing a second example of the frequency analysis results (Q / Qd=1.175) of the same pressure fluctuations. [Figure 17] 10 is a graph showing the results of a comparison of pressure-boosting performance depending on the width and depth of the notch in the inducer. [Figure 18] 1A to 1C are schematic front views showing examples of inducers according to modified examples (first to third modified examples) of an embodiment of the present invention, where (a) is a front view of the first modified example, (b) is a front view of the second modified example, and (c) is a front view of the third modified example. [Figure 19] 10A and 10B are schematic circumferential cross-sectional views showing examples of inducers according to modified examples (fourth and fifth modified examples) of an embodiment of the present invention, where (a) is a front view of the fourth modified example, and (b) is a front view of the fifth modified example. DETAILED DESCRIPTION OF THE INVENTION

[0013] Inducers according to embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing an example of the configuration of a turbopump equipped with an inducer according to an embodiment of the present invention.

[0014] As shown in Fig. 1, the inducer 1 of this embodiment is used in a turbopump 100. In addition to the inducer 1, the turbopump 100 includes a casing 10, a rotor shaft 5, a first centrifugal impeller 2, a second centrifugal impeller 3, and a turbine 4. Note that the configuration of the turbopump 100 excluding the inducer 1 is an example, and is not limited to the configuration shown in Fig. 1. The turbopump 100 is not particularly limited in its application, but is particularly suitable as a pump for transporting liquid fuel in a rocket engine, for example.

[0015] The casing 10 is tubular, and has a pump inlet 10a and a drive gas outlet 10d at both longitudinal ends. A pump outlet 10b and a drive gas inlet 10c are opened at a side of the casing 10. The pump inlet 10a is an opening through which the fluid F transported by the turbopump 100 is supplied. When the turbopump 100 is a rocket turbopump, examples of the fluid F include a fuel such as liquid hydrogen, an oxidizer such as liquid oxygen, and the like. The pump outlet 10b is an outlet for the fluid F that has flowed into the interior, and is connected via an appropriate piping member to a device that uses the fluid F. For example, if the turbopump 100 is a turbopump for a rocket, the pump outlet 10b is connected to the combustion chamber of the rocket engine or the like. The drive gas inlet 10c is a supply port for drive gas G that rotates and drives the turbine 4, which will be described later. The drive gas outlet 10d is a discharge port for drive gas G.

[0016] The rotor shaft 5 is an axial member extending along a central axis O. The rotor shaft 5 is supported rotatably around the central axis O by a first bearing 6 and a second bearing 7 fixed to a support member (not shown) inside the casing 10. The rotor shaft 5 is disposed in the center of a pipe line within the casing 10 extending from the pump inlet 10a to the drive gas outlet 10d. The inducer 1, the first centrifugal impeller 2, the second centrifugal impeller 3, and the turbine 4 are fixed in this order along the axial direction of the rotor shaft 5.

[0017] Unless otherwise specified, in the following description, positions and regions closer to the pump inlet 10a than a specific position along the central axis O will be referred to as upstream positions and regions. Similarly, positions and regions closer to the drive gas outlet 10d than a specific position will be referred to as downstream positions and regions.

[0018] The inducer 1 is used for the purpose of suppressing cavitation at the inlet of a first centrifugal impeller 2, which will be described later, by pressurizing the fluid F. The inducer 1 is disposed inside the tubular portion 10e of the casing 10 in the vicinity of the pump inlet 10a. The inducer 1 is fixed to the rotor shaft 5 on the upstream side of the first bearing 6 and is rotatable together with the rotor shaft 5. The detailed configuration of the inducer 1 will be described later.

[0019] The first centrifugal impeller 2 and the second centrifugal impeller 3 are fixed to the rotor shaft 5 on the downstream side of the inducer 1. In the example shown in FIG. 1 , the first centrifugal impeller 2 and the second centrifugal impeller 3 are arranged between a first bearing 6 and a second bearing 7. The first centrifugal impeller 2 and the second centrifugal impeller 3, together with the inner wall portion of the casing 10 in their vicinity, constitute the main pump of the turbopump 100. However, the configuration in which the main pump has the first centrifugal impeller 2 and the second centrifugal impeller 3 is just one example. As long as the specifications required for the turbo pump 100 are satisfied, the centrifugal impeller that constitutes the main pump of the turbo pump 100 may be the first centrifugal impeller 2 only.

[0020] The fluid F pressurized by the inducer 1 is pressurized by the rotation of the first centrifugal impeller 2, and then further pressurized by the rotation of the second centrifugal impeller 3, and is discharged from the pump outlet 10b.

[0021] The turbine 4 is fixed to the rotor shaft 5 downstream of the second bearing 7. The turbine 4 is rotated about the central axis O by the drive gas G supplied from the drive gas inlet 10c. This causes the rotor shaft 5 to also rotate about the central axis O. The turbine 4 is an example of a rotational drive means for the inducer 1 and the main pump in the turbo pump 100. However, other rotational drive means may be used depending on the application of the turbo pump 100. For example, an electric motor or the like may be used as the rotational drive means for the inducer 1 and the main pump.

[0022] Next, the detailed configuration of the inducer 1 of this embodiment will be described. Fig. 2 is a schematic front view showing an example of an inducer according to an embodiment of the present invention, and Fig. 3 is a schematic side view showing an example of an inducer according to an embodiment of the present invention.

[0023] 2 shows the shape of inducer 1 as viewed from the most upstream side in the axial direction. In the following, when describing the configuration of each part of inducer 1, the X-axis, Y-axis, and Z-axis of an XYZ right-handed Cartesian coordinate system may be referenced. The Z axis is an axis coaxial with the central axis O (although in FIG. 2, for ease of viewing, it is drawn shifted from the central axis O). The direction along the Z axis is referred to as the Z direction. The positive direction in the Z direction is the direction from the downstream side to the upstream side (the direction from the back of the paper to the front of the paper). The negative direction in the Z direction is the opposite direction to the positive direction.

[0024] The Z direction is sometimes referred to as the axial direction. A direction that rotates around the Z axis is sometimes referred to as the circumferential direction, and a direction along an arbitrary axial direction perpendicular to the Z axis is sometimes referred to as the radial direction. The X-axis is an axis that is perpendicular to the Z-axis and overlaps with a line that passes through the central axis O and the inlet end terminal point pC, which will be described later, when viewed from the Z direction. The direction along the X-axis is called the X-direction. The positive direction in the X-direction is the direction from the inlet end terminal point pC toward the central axis O (the direction from the left to the right in the drawing). The negative direction in the X-direction is the opposite direction to the positive direction. The Y axis is an axis perpendicular to the Z axis and the X axis. The direction along the Y axis is called the Y direction. The positive Y direction is the direction determined by the convention of a right-handed Cartesian coordinate system (the direction from bottom to top in the illustration) when defining the positive directions of the Z axis and the X axis as described above. The negative Y direction is the opposite direction to the positive direction.

[0025] The inducer 1 comprises a hub 1D (shaft body) extending in the axial direction, and a first blade (first blade) 1A, a second blade (second blade) 1B, and a third blade (third blade) 1C (multiple blades) protruding radially outward from the outer surface 1e of the hub 1D.

[0026] The hub 1D is formed in a cylindrical shape having an inner peripheral surface 1d that fits onto the rotor shaft 5. The hub 1D is fixed to the rotor shaft 5 in a state where it is fitted onto the rotor shaft 5. As shown in FIG. 3, in this embodiment, the outer circumferential surface 1e of the hub 1D has a horn shape that gradually increases in diameter from an end face 1f in the positive Z direction toward the negative Z direction.

[0027] The first blade 1A, the second blade 1B, and the third blade 1C are arranged in a three-strand spiral on the outer peripheral surface 1e of the hub 1D. For simplicity, the first blade 1A, the second blade 1B, and the third blade 1C may hereinafter be collectively referred to as "each blade." The number of turns of each blade (number of rotations around the hub 1D) is not particularly limited as long as it satisfies the suction performance and pressurization performance required for the inducer 1. The number of turns in the configuration shown in Fig. 3 is approximately one. In this embodiment, each blade has a shape that is three-fold rotationally symmetrical with respect to the central axis O.

[0028] As shown in FIG. 2, when viewed from the most upstream side in the negative Z direction, the radially outer contour of each blade is along a circumference C with the central axis O as its center. Inlet ends 1Aa, 1Ba, 1Ca that protrude counterclockwise when viewed in the negative Z direction are formed at the circumferential tips of first blade 1A, second blade 1B, and third blade 1C, respectively. The blade starting points qA, qB, and qC on the outer peripheral surface 1e of the hub 1D are aligned in the same plane perpendicular to the central axis O, and are arranged at positions on this alignment plane that divide the outer peripheral surface 1e into three equal parts, as shown in Figure 2.

[0029] For example, the inlet end 1Aa protrudes in an arc shape in the counterclockwise direction as shown in Fig. 2 from a line segment LA connecting the blade starting point qA on the outer peripheral surface 1e and the inlet end terminal point pA on the circumference C. Similarly, the inlet end 1Ba protrudes in an arc shape in the counterclockwise direction as shown in Fig. 2 from a line segment LB connecting the blade starting point qB on the outer peripheral surface 1e and the inlet end terminal point pB on the circumference C. The inlet end 1Ca protrudes in an arc shape in the counterclockwise direction as shown in Fig. 2 from a line segment LC connecting the blade starting point qC on the outer peripheral surface 1e and the inlet end terminal point pC on the circumference C. The line segments LA, LB, and LC are inclined in the direction opposite to the rotation direction of the inducer 1 (clockwise direction in the drawing) with respect to a radial line passing through the blade starting points qA, qB, and qC, respectively. Hereinafter, the edges of the inlet ends 1Aa, 1Ba, 1Ca between the blade starting points qA, qB, qC and the inlet end terminal points pA, pB, pC will be referred to as leading edges eA, eB, eC, respectively.

[0030] Blade bodies 1Ab, 1Bb, and 1Cb are formed downstream of line segments LA, LB, and LC, respectively. The blade bodies 1Ab, 1Bb, 1Cb have a radial width extending from the outer peripheral surface 1e to blade tips oA, oB, oC aligned with the circumference C when viewed in the Z direction, and spiral downstream. As shown in Fig. 3, blade ends bA and bC, which are the end portions of blade bodies 1Ab and 1Cb, are formed in a linear shape extending in the radial direction. Although not shown in Fig. 3, a similar blade end is also formed at the end portion of blade body 1Bb.

[0031] As shown in Fig. 2, when each blade is viewed from the most upstream side in the axial direction (negative Z direction), the inlet end portions 1Aa, 1Ba, and 1Ca and parts of the blade bodies 1Ab, 1Bb, and 1Cb are exposed. Hereinafter, the position of each blade in the counterclockwise direction when viewed axially from the upstream side will be referred to as the circumferential front, and the opposite position will be referred to as the circumferential rear. As shown in Figure 2, the area of ​​the first blade 1A including its leading edge eA and one-third of the circumference of the blade tip oA following the leading edge eA is exposed circumferentially forward of the leading edge eB of the second blade 1B (the upstream blade). Circumferentially aft of the leading edge eB, the first blade 1A is submerged under the second blade 1B.

[0032] As shown in Figure 2, the area of ​​the second blade 1B including its leading edge eB and one-third of the circumference of the blade tip oB following the leading edge eB is exposed circumferentially forward of the leading edge eC of the third blade 1C (the upstream blade). Circumferentially aft of the leading edge eC, the second blade 1B is submerged under the third blade 1C. As shown in Figure 2, the third blade 1C has a region including its leading edge eC and one-third of the circumference of the blade tip oC that follows the leading edge eC, which is exposed circumferentially forward of the leading edge eA of the first blade 1A (the upstream blade). Circumferentially aft of the leading edge eA, the third blade 1C is submerged under the first blade 1A.

[0033] In the inducer 1, the flow passage where the inducer 1 can effectively work on the inflowing fluid F to increase the pressure of the fluid F is called a throat. Specifically, it is a flow passage sandwiched between adjacent blades in the axial direction. In this embodiment, the throat T is formed by a flow passage sandwiched between the area circumferentially aft of the leading edges eA, eB, and eC of each blade and the blades downstream of each of the leading edges, as shown in Figures 2 and 3. In each throat T, the area that axially overlaps with the leading edges eA, eB, and eC of each blade is the throat inlet Te (throat inlet).

[0034] In contrast, similar gaps E are formed, for example, between the inlet end 1Ca and the blade body 1Bb (see Figure 2), between the inlet end 1Ba and the blade body 1Ab, and between the inlet end 1Aa and the blade body 1Cb (see Figure 3).

[0035] As shown in FIG. 2, first blade 1A, second blade 1B, and third blade 1C are formed with notches 1a, 1b, and 1c. In this embodiment, the positions at which the notches 1a, 1b, and 1c are formed are rotationally symmetrical about the central axis O. The three notches 1a, 1b, and 1c are formed at equal intervals around the central axis O, and therefore the three notches 1a, 1b, and 1c are formed at intervals of 120° around the central axis. In the following explanation, cutout 1a will be used as an example, but the following explanation also applies to cutout 1b in second blade 1B and cutout 1c in third blade 1C.

[0036] FIG. 4 is a schematic enlarged view showing the configuration of the notch 1a in the inducer 1 according to the embodiment of the present invention. 4, the notch 1a opens at the blade tip oA of the first blade 1A, extends radially inward by a distance shorter than the opening width, and penetrates through the thickness of the first blade 1A. In this embodiment, the radially inner tip 1g of the notch 1a is a flat surface parallel to the extension direction of the notch 1a. The notch 1a is located at a position that does not overlap with the second blade 1B, which is located counterclockwise relative to the first blade 1A shown in FIG. 2, in the axial direction, and is formed outside the throat inlet Te. More specifically, in the example shown in FIGS. 2 and 4, the leading edge eB of the inlet end 1Ba reaches the blade tip oA (the inlet end end point pB), that is, at the blade tip oA outside the throat inlet Te, and in the vicinity of the leading edge eB.

[0037] As long as the notch 1a opens at the outer edge of the first blade 1A, extends radially inward by a distance shorter than the opening width, and opens at the blade tip oA (the radial outer edge excluding the circumferential leading edge eB), the circumferential position of the notch 1a is not limited to the position shown in Fig. 2. For example, the notch 1a may be formed at a position adjacent to the throat inlet Te shown in Fig. 2, further away along the blade tip oA in the counterclockwise direction. When notch 1a is formed at any position further counterclockwise along blade tip oA than the position shown in Figure 2, the limit position for formation is the position of inlet end terminal point pA of throat T formed by first blade 1A and third blade 1C. Therefore, notch 1a is formed at any blade tip position between inlet end terminal point pB and inlet end terminal point pA.

[0038] However, if the position of the cutout 1a is moved counterclockwise along the blade tip oA from the position shown in Figures 2 and 4, there is a concern that the head performance and suction performance will gradually decrease, so it is more desirable to position the cutout 1a closer to the position shown in Figures 2 and 4 than to a position closer to the inlet end terminal point pA. For this reason, it is more desirable to position the cutout 1a closer to the inlet end terminal point pB than to a position halfway between the inlet end terminal point pB and the inlet end terminal point pA. Also, the cutout 1a may be formed in a region overlapping with the throat inlet portion Te. The positions of the notches 1b and 1c are in the same relationship as the notch 1a. pB and the inlet end terminal point pC, and notch 1c is formed between the inlet end terminal point pC and the inlet end terminal point pA. Therefore, notches 1a, 1b, and 1c are all formed at the positions shown in Figure 2 when viewed from the most upstream side in the negative direction of the Z axis. In other words, with respect to the throat T formed from the upstream side to the downstream side in the inducer 1, the nozzle hole 11 is formed on the side closer to the inlet of each throat T (upstream side).

[0039] In this embodiment, as shown in FIG. 4, the radius of the blade tip oA is rt, the outer radius of the hub 1D is rh (where rh < rt), and the distance from the blade tip oA to the outer peripheral surface 1e of the hub 1D is rb (= rt - rh). However, the outer radius rh of the hub 1D increases as it goes in the negative Z direction as shown in FIG. 3. As shown in FIG. 2, the opening width of the notch 1a is b, and the depth (length) is h (where b > h). The notch 1a penetrates the first blade 1A straight in the Z direction.

[0040] The width b and depth h of the notch 1a preferably have the following relationship in relation to the diameter DM (blade diameter) of the circle drawn by the blade tips oA, oB, and oC of each blade shown in FIG. 2. 0.039DM ≤ b ≤ 0.178DM 0.039DM ≤ h ≤ 0.270DM Note that the width b and depth h of the notches 1b and 1c also have the same relationship as the width b and depth h of the notch 1a.

[0041] Furthermore, regarding the width b and depth h of the notch 1a, in relation to the diameter DM (blade diameter) of the circle drawn by the blade tips oA, oB, and oC of each blade shown in FIG. 2, it is more preferable that they are within the range surrounded by points A1, A2, A3, A4, A5, and A6 shown in FIG. 14 described later. However, the range surrounded by the points A1, A2, A3, A4, A5, and A6 is shown in detail in FIG. 14 where the horizontal axis represents the relative ratio (b / DM) of the width (b) of the notch to the blade diameter (DM), and the vertical axis represents the relative ratio (h / DM) of the depth (h) of the notch to the blade diameter (DM).

[0042] In the examples described later, the outer diameter of the blade is 152 mm, and the coordinate positions of each point are point A1(6, 30), point A2(18, 41), point A3(24, 30), point A4(27, 20), point A5(27, 10), and point A6(20, 6).

[0043] When the coordinates of these points are converted into relative ratios that fit the above formula, the following are obtained: point A1 where the relative ratio of the width is 0.039 and the relative ratio of the depth is 0.197; point A2 where the relative ratio of the width is 0.118 and the relative ratio of the depth is 0.270; point A3 where the relative ratio of the width is 0.158 and the relative ratio of the depth is 0.197; point A4 where the relative ratio of the width is 0.178 and the relative ratio of the depth is 0.132; point A5 where the relative ratio of the width is 0.178 and the relative ratio of the depth is 0.066; 0.039 The area enclosed by point A6 indicates the area.

[0044] Next, the cavitation instability phenomenon will be explained. For example, in the inducer for a rocket engine, cavitation is desirable to reduce because it leads to performance degradation. However, since it is difficult to completely suppress cavitation, it is considered important to suppress instability phenomena by suppressing the occurrence of asymmetric cavitation, for example. Examples of cavitation instability include rotating cavitation and cavitation surge. Below, we will briefly explain the rotating cavitation and cavitation surge that occur in a comparative inducer in which the notches 1a, 1b, and 1c are not provided in the inducer 1. FIG. 5 is a schematic diagram illustrating an example of the cavitation instability phenomenon.

[0045] Cavitation is a phenomenon in which a localized pressure drop in a fluid inside a fluid machinery causes the fluid to vaporize, forming bubbles or gas film-like gas regions (called cavities) within the fluid. The generation of cavities and their volume changes cause asymmetry in blade loading and fluctuations in the fluid flow rate and pressure, resulting in axial vibration of the turbomachinery impeller and fluid pulsation.

[0046] Rotating cavitation is a phenomenon in which the volume of the cavities generated on each blade fluctuates as the inducer rotates, making it appear as if the cavities are moving between the blades. In rotating cavitation, the cavities generated on each blade are asymmetrical about the axis. For this reason, rotating cavitation is the main cause of axial vibration in turbopumps. Hereinafter, the rotational frequency of the inducer is represented by ω, and the rotational frequency of the cavity is represented by ωc (stationary system) and Ωc (rotating system). Rotating cavitation is classified into supersynchronous rotating cavitation (ωc>ω), synchronous rotating cavitation (ωc=ω), and subsynchronous rotating cavitation (ωc<ω) depending on the relationship between ω and ωc.

[0047] In Figure 5, the "Super-S RC" column contains a schematic diagram of super synchronous rotating cavitation (hereafter abbreviated as SSRC). Each diagram is a schematic diagram of the inducer seen from the upstream side, with each blade displayed using dots of different densities. The white areas at the edge of each blade represent cavities (Ca). The numbers in the "Inducer Rotation Speed" column indicate the number of rotations from the reference static system state ("0", hereafter referred to as the reference state). The schematic diagrams corresponding to inducer rotation speeds 0 to 4 schematically show the static system state at each rotation.

[0048] In an SSRC, the size, shape, and other patterns of the cavity Ca on each blade change with each rotation and return to the reference pattern after a certain number of rotations. In the example shown in Figure 5, the cavity Ca repeats the same pattern every four rotations, so the cavity Ca rotates counterclockwise at Ωc = 0.25ω. In other words, when viewed from a stationary system, the cavity appears to be rotating at ωc = 1.25ω, which is faster than the inducer. Generally, ωc in an SSRC is about 1.1ω to 1.3ω. ωc is the excitation frequency of the shaft vibration. Unlike the natural vibration of the inducer, ωc changes depending on the operating state, which makes it difficult to predict in design.

[0049] In Figure 5, the "Sync RC" column shows a schematic diagram of synchronous rotating cavitation (hereinafter abbreviated as SRC). The meaning of each diagram is the same as that of SSRC. In the SRC, the size and shape of the cavity Ca on each blade are asymmetrical. SSRC Unlike the case of the rotor, it is attached to the blade in the reference state. Therefore, the cavity Ca rotates in synchronization with the inducer, and Ωc = 0ω, i.e., ωc = ω.

[0050] Although not specifically shown, subsynchronous rotating cavitation differs from SSRC in that ωc<ω, so the cavity pattern rotates in the opposite direction to the rotation direction of the inducer in the rotating system.

[0051] Cavitation surge (hereafter abbreviated as CS) is a phenomenon in which the cavity volume fluctuates in the same phase and frequency on all blades. CS causes pulsations in the fluid flow rate and pressure, which leads to a decrease in turbopump performance. In Figure 5, the "CS" column shows a schematic diagram of a cavitation surge (hereafter abbreviated as CS). The meaning of each diagram is the same as in the case of SSRC. In the example shown in Figure 5, the cavity size on each blade is maximum in the reference state, then minimum at 1.5 rotations (not shown), and returns to the reference state at 3 rotations. This change is repeated. Therefore, the pattern of each cavity does not rotate in either the fixed or rotating system.

[0052] "Inducer Action and Function" Next, the operation and function of the inducer 1 will be explained, focusing on the function of the notch 1a. The functions of the notches 1b and 1c are the same as those of the notch 1a. The inducer 1 is driven to rotate counterclockwise as viewed from the most upstream side in the negative Z direction by the rotation of the turbine 4, as shown in Fig. 2. As a result, as shown in Fig. 3, fluid F is sucked into the inducer 1 and is pumped through the flow passage between the blades like fluid F1, and moves overall in the negative Z direction (forward flow). The upstream side of the inducer 1 (the pump inlet 10a side) is at low pressure, while the downstream side of the inducer 1 (the first bearing 6 side) is pressurized to high pressure. A gap g exists between the blade tips oA, oB, and oC of each blade and the inner wall of the tubular portion 10e, as shown in Fig. 3. A leakage flow f (reverse flow) that flows in the positive Z direction (leftward in Fig. 3) is formed in this gap g. When this leakage flow f reaches the low-pressure area upstream, it forms a leakage vortex region V. This leakage vortex region V is formed near the blade tips oA, oB, and oC and near the leading edges eA, eB, and eC. The leakage vortex region V reduces the pressure at the vortex center, which is thought to contribute to the growth of the cavity.

[0053] In contrast, inducer 1 has notches 1a, 1b, and 1c (hereinafter sometimes referred to as each notch), which generates a leakage flow fS that flows through each notch in the positive Z direction. For this reason, it is thought that the leakage flow fS increases near each notch. If this causes the strength of the vortex to become non-uniform in the circumferential direction, it is thought that the vortex becomes unstable, suppressing the pressure drop at the vortex center and suppressing the growth of the cavity.

[0054] The effect of the notch 1a on the flow field was confirmed using numerical analysis. For the numerical analysis, we used ANSYS CFX19.0, a general-purpose thermal fluid analysis software. The governing equations were the three-dimensional incompressible gas-liquid two-phase Navier-Stokes equations, which took into account phase changes and assumed an isothermal process. Ta. The SST k-ω model was used as the turbulence model, and the isotropic two-phase flow model that takes into account the dynamics of cavitation bubbles using the simplified Rayleigh-Plesset equation implemented in CFX was used as the cavitation model.

[0055] Prior to conducting a numerical analysis of the effect of the notch 1a on the flow field, the present inventor previously conducted a numerical analysis based on the configuration of an inducer with a slit described in JP 2021-011840 A. The inducer 101 with a slit described in JP 2021-011840 A has the configuration shown in Fig. 6. The same components as those of the inducer 1 described above are denoted by the same reference numerals, and a description of the same components in the inducer 101 will be omitted. Inducer 101 has elongated slits 101a, 101b, and 101c formed at inlet end terminal points pA, pB, and pC, respectively. The slits extend radially inward from blade tips oA, oB, and oC toward central axis O, and are longer than the opening width. Slits 101a, 101b, and 101c are all formed inside throat T, and as shown in FIG. 6, slit 101a is formed at a position hidden by inlet end 1Ba, slit 101b is formed at a position hidden by inlet end 1Ca, and slit 101c is formed at a position hidden by inlet end 1Aa.

[0056] Figure 7 shows the asymmetric cavitation maps obtained through the above-mentioned numerical analysis when the outer diameter of the blade was set to 152 mm, the notch depth was set to 30 mm, and the width of each of the slits 101a, 101b, and 101c was set to 0 mm (no slit), 2.5 mm, 5 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, or 60 mm. In the analysis results shown in Figure 7, the open circles indicate that asymmetric cavitation did not occur (showing symmetry), and the filled circles indicate that asymmetric cavitation occurred (showing asymmetry).

[0057] From the analysis results shown in Fig. 7, it was found that in the inducer 101 having the structure shown in Fig. 6, the occurrence of asymmetric cavitation was observed regardless of the slit width being set to any value up to 60 mm. Furthermore, it was speculated that the occurrence of asymmetric cavitation may be more effectively suppressed by a slit with a wider slit width than by a slit with a narrower slit width.

[0058] Therefore, the inventors reconsidered the positions and shapes of the slits 101a, 101b, and 101c, provided notches 1a, 1b, and 1c at the positions shown in Figures 2 to 4, and performed a numerical analysis on the occurrence of asymmetric cavitation by adjusting the widths of the notches 1a, 1b, and 1c. However, the flow rate condition was set to Q / Qd = 1.1, where Q / Qd is the flow rate ratio when the design flow rate is Qd. Figure 8 shows the asymmetric map of cavitation when the width of the notch is set to 5 mm and the depth of the notch is set to 0 mm (no notch), 10 mm, 20 mm, 30 mm, and 35 mm. Figure 9 shows the asymmetric map of cavitation when the width of the notch is set to 10 mm and the depth of the notch is set to 0 mm (no notch), 10 mm, 20 mm, 30 mm, and 35 mm. Figure 10 shows the asymmetric map of cavitation when the width of the notch is set to 20 mm and the depth of the notch is set to 0 mm (no notch), 2.5 mm, 5 mm, 7.5 mm, 10 mm, 20 mm, 30 mm, and 35 mm.

[0059] Figure 11 shows the asymmetric map of cavitation when the width of the notch is set to 22.5 mm and the depth of the notch is set to 0 mm (no notch), 10 mm, 20 mm, 30 mm, and 35 mm. Figure 12 shows the asymmetric map of cavitation when the width of the notch is set to 25 mm and the depth of the notch is set to 0 mm (no notch), 10 mm, 20 mm, 30 mm, and 35 mm. Figure 13 shows the asymmetric map of cavitation when the width of the notch is set to 27.5 mm and the depth of the notch is set to 0 mm (no notch), 10 mm, 20 mm, 30 mm, and 35 mm.

[0060] Comparing the results shown in Figures 8 and 9, it can be seen that when the depth of the notch is changed from 5 mm to 10 mm, the region in which the occurrence of asymmetric cavitation can be suppressed expands at notch depths of 20 mm, 30 mm, and 40 mm. Referring to the results shown in FIG. 10, it was found that asymmetric cavitation could be completely suppressed over a wide range of notch depths from 7.5 mm to 35 mm. It can be seen from the analysis results shown in Figs. 11 and 12 that a region where asymmetric cavitation can be suppressed can be obtained. From the results shown in Figure 13, it was found that when the depth of the notch was set to 27.5 mm, the area where asymmetric cavitation occurs increased, and the suppression effect of asymmetric cavitation decreased.

[0061] Judging comprehensively from the analysis results shown in FIGS. 8 to 13, it is considered preferable to select the region shown in FIG. 14 as the size of the cutout (width b, depth h) that can completely suppress asymmetric cavitation.

[0062] FIG. 14 is a graph in which the horizontal axis represents the width of the notch in mm, and the vertical axis represents the depth of the notch in mm. In Figure 14, the size of the notch (width b, depth h) that completely suppresses the above-mentioned asymmetric cavitation is shown by a solid ● mark, and the size of the notch (width b, depth h) when the suppression effect of asymmetric cavitation is reduced is shown by a hollow ○ mark. In addition, in FIG. 14, the circles are present in the range of notch widths from 6 mm to 27 mm and notch depths from 6 mm to 41 mm.

[0063] If the outer diameter (DM) of the blade is 152 mm, the relative ratio b / DM of the width (b) to the outer diameter (DM) of the blade for a notch width of 6 mm is 0.039, and the relative ratio b / DM of the width (b) to the outer diameter (DM) of the blade for a notch width of 27 mm is 0.178. If the outer diameter (DM) of the blade is 152 mm, the relative ratio h / DM of the depth (h) to the outer diameter (DM) of the blade for a notch depth of 6 mm is 0.039, and the relative ratio h / DM of the depth (h) to the outer diameter (DM) of the blade for a notch depth of 41 mm is 0.270. Therefore, it can be interpreted that at the formation position of the notch shown in FIG. 2, there exists a region in which asymmetric cavitation can be suppressed in the ranges of 0.039DM≦b≦0.178DM and 0.039DM≦h≦0.270DM.

[0064] Furthermore, if we select only the area in the graph shown in Figure 14 that shows the size of the notch (width b, depth h) that can completely suppress the above-mentioned asymmetric cavitation, it is more preferable that it be within the range surrounded by points A1, A2, A3, A4, A5, and A6 shown in Figure 14. In the graph shown in Figure 14, the coordinates of point A1 can be written as (6,30), the coordinates of point A2 as (18,41), the coordinates of point A3 as (24,30), the coordinates of point A4 as (27,20), the coordinates of point A5 as (27,10), and the coordinates of point A6 as (20,6). Here, since the outer diameter of the blade used in the above-mentioned numerical analysis is 152 mm, the width (b) and depth (h) of the notch are converted into a relative ratio (b / DM) to the blade diameter (DM), and the vertical axis is converted into a relative ratio (h / DM) of the depth (h) of the notch to the blade diameter (DM), resulting in the following relationship:

[0065] Point A1 (6, 30) is a point where the relative ratio of the width b is 0.039 and the relative ratio of the depth h is 0.197. Point A2 (18, 41) is a point where the relative ratio of the width b is 0.118 and the relative ratio of the depth h is 0.270. Point A3 (24, 30) is a point where the relative ratio of the width b is 0.158 and the relative ratio of the depth h is 0.197. Point A4 (27, 20) is a point where the relative ratio of the width b is 0.178 and the relative ratio of the depth h is 0.132. Point A5 (27,10) is a point where the relative ratio of the width b is 0.178 and the relative ratio of the depth h is 0.066. At point A6 (20,6), the relative ratio of the width b is 0.132, and the relative ratio of the depth h is 0.039 This is the point that indicates The area surrounded by points A1 to A6 is an area where asymmetric cavitation was completely suppressed, but since there may be an area where only one point indicates the possibility of asymmetric cavitation occurring, as shown in Figures 9 and 11, the area where asymmetric cavitation can be sufficiently suppressed is thought to be slightly wider than the area surrounded by points A1 to A6. For this reason, as described above, it can be determined that at the formation position of the notch, an area where asymmetric cavitation can be suppressed exists in the ranges of 0.039DM≦b≦0.178DM and 0.039DM≦h≦0.270DM.

[0066] Next, experimental results showing that the cavitation instability phenomenon is suppressed by each notch will be described. In the experiment, the inducers used were a reference example inducer 333 (referred to as "Inducer 333" in Figures 15(A) and (B)) based on a liquid oxygen turbopump inducer, and a comparative example inducer 555 (referred to as "Inducer 555" in Figures 16(A) and (B)).

[0067] The inducer 333 is a reference example in which only the formation position of the notch is adopted in the inducer 1 described above, and the inducer 555 is an example of the inducer 101 described above. The inducers 333 and 555 have three blades, an inducer inlet tip diameter (outer diameter of blade tip oA, etc., 2 × rt) of 152 mm, an inducer inlet hub diameter (outer diameter of outer peripheral surface 1e on the most upstream side, 2 × rh) of 38 mm, and a tip clearance (size of gap g) of 0.5 mm. These shapes are common to inducers 333 and 555.

[0068] The inducer 333 has three notches, each with an opening width b of 5 mm and a depth h of 30 mm. As described above, each notch is located outside the throat inlet Te, at a position rotated 48° counterclockwise around the central axis O from the inlet end terminal points pA, pB, and pC along the blade tip. Therefore, each notch is formed axially symmetrically (three-fold rotational symmetry) with respect to the central axis O. The inducer 555 of the comparative example had three slits, with the slit opening width and length being d = 5 (mm) and L = 30 (mm), respectively. As described above, each slit was located on the throat inlet portion Te side, at the inlet end terminal points pA, pB, and pC. Therefore, each slit was formed axially symmetrically (three-fold rotational symmetry) with respect to the central axis O.

[0069] As an experimental device teeth, The water flow cavitation tunnel test facility at the Kakuda Space Center of the Japan Aerospace Exploration Agency was used. teeth, This is a circulating water tank that uses water as the working fluid. A pressure adjustment mechanism using a cylinder piston is installed upstream of the inducer under test, allowing the inducer under test to be reduced to any desired inlet pressure. teeth, Turbine flow meters and ultrasonic flow meters are installed. teeth, The temperature of the working fluid is adjusted by changing the opening of the flow control valve downstream of the flow meter. A heat exchanger is installed further downstream, and the temperature of the working fluid is kept almost constant during the test. The casing used in the test is made of transparent acrylic resin, in, The cavitation was visualized using high-speed video. Furthermore, pressure sensors installed on the casing measured pressure oscillations at the inlet, outlet, and intermediate points of the inducer. High-speed video recording teeth, The shooting speed was 10,000 fps and the shutter speed was 1 / 25,000 s. Pressure fluctuation data obtained by the pressure sensor teeth, The data was collected at a sampling frequency of 10 kHz. R, After the test, frequency analysis was performed using an FFT analyzer.

[0070] The working fluid (fluid F) was water at 298.5K. The design flow rate Qd was 192 L / s and the design rotation speed was 18,300 rpm, but the rotation speed of the test inducer in the experiment was set to 6,000 rpm (rotation frequency: 100 Hz). In the experiment teeth,By keeping the rotation speed and the opening of the flow control valve constant and gradually decreasing the inlet pressure, the cavitation number σ was decreased, and data such as pressure fluctuations and flow rate were obtained when cavitation grew. The cavitation number σ is expressed by the following formula (1): The cavitation number σ is a dimensionless number corresponding to the pressure of the fluid F.

[0071]

number

[0072] where p in is the main static pressure upstream of the inducer under test, p v is the saturated vapor pressure at the mainstream temperature, ρ∞ is the density of the working fluid, U t is the tip speed (the peripheral speed at the tip of the blade) of the inducer under test.

[0073] The experimental results will be explained below. Fig. 15 is a graph showing the results of a frequency analysis of pressure fluctuations (flow rate conditions: Q / Qd = 1.175: Qd is the design flow rate) in an inducer of a reference example in which a slit (width 5 mm, depth 30 mm) is provided at the position shown in Fig. 2. Here, Q / Qd is the flow rate ratio when Qd is the design flow rate. FIG. 16 is a graph showing the results of a frequency analysis of pressure fluctuations (flow rate condition: Q / Qd=1.175) in an inducer of a comparative example in which a slit (width 5 mm, depth 30 mm) is provided at the position shown in FIG. 15 and 16 show the power spectrum ΔP (kPa pp) of the pressure fluctuation in the inducers 333 and 555 when the flow rate condition is set to Q / Qd=1.175 and the cavitation number σ is changed from 0.01 to 0.08.

[0074] In the comparative inducer in which the slits are provided at the positions shown in FIG. 6, supersynchronous orbiting cavitation occurs as shown in FIG. In contrast, in the inducer of the reference example in which the slits were provided at the positions shown in Figure 2, supersynchronous orbital cavitation was almost completely suppressed as shown in Figure 15. This means that even if the slit is long and narrow, with a depth greater than its width, changing the position of the slit from the position shown in Figure 6 to the position shown in Figure 2 is effective in suppressing supersynchronous orbital cavitation.

[0075] In the inducer of the embodiment shown in Figure 2 of the present application, a notch is provided at the position shown in Figure 2, and the notch is placed at a position that is effective in suppressing supersynchronous orbiting cavitation.In addition, by providing a notch having the width and depth relationship described above, it is possible to obtain the effect of suppressing asymmetric cavitation.

[0076] Figure 17 shows the comparison of the head coefficient (≒pressure boosting capacity) of an inducer without a notch and the head coefficient of inducers with notches of various widths and depths at the positions shown in Figure 2. Figure 17 shows the head coefficient of inducers with a 10 mm wide, 30 mm deep notch, a 10 mm wide, 35 mm deep notch, a 20 mm wide, 10 mm deep notch, a 20 mm wide, 20 mm deep notch, a 20 mm wide, 30 mm deep notch, and a 20 mm wide, 35 mm deep notch, each located at the same position as in Figure 2.

[0077] As shown in the comparison results in Figure 17, the inducer without a notch has the highest head coefficient and is considered to have high pressure-boosting capacity. In contrast, providing a notch in the inducer means that the pressure-boosting capacity decreases slightly, but even if the pressure-boosting capacity decreases slightly, it is clear that providing a 20 mm wide and 10 mm deep notch, i.e., a notch whose width is greater than its depth, reduces the pressure-boosting capacity less than other notches whose depth is greater than their width.

[0078] The results shown in Figure 17 indicate that in order to suppress asymmetric cavitation while maintaining the pressure-boosting capacity of the inducer, it is advantageous to form the notch at the position shown in Figure 2 and to make the notch as described above wider than it is deep. It was also found that by selecting the above-described formation position in the inducer and ensuring that the relationship between the depth and width of the notch satisfies the above-described relationship, an inducer that can better suppress cavitation can be provided.

[0079] [First to third modified examples] Next, first to third modified examples of this embodiment will be described. 18(a), (b), and (c) are schematic front views showing examples of inducers according to modifications (first to third modifications) of the embodiment of the present invention. The following description will focus on the differences from the embodiment.

[0080] As shown in Figure 18(a), the main part of the inducer 11 of the first modified example has a tip 11g consisting of an arc-shaped curved surface convex in the extension direction of the cutout 1a, instead of the flat tip 1g of the cutouts 1a, 1b, and 1c of the inducer 1. As a result, the shape of each cutout portion when viewed from the Z direction is U-shaped. According to this modification, stress concentration at the tip 11g of each notch is alleviated, and therefore the durability of the inducer 11 is improved.

[0081] As shown in Fig. 18(b), the inducer 12 of the second modified example has isosceles trapezoidal cutouts 12a, 12b, and 12c as cutouts replacing the cutouts 1a, 1b, and 1c of the inducer 1. The tip 12g of each isosceles trapezoidal cutout may be a flat surface or a convex arc-shaped curved surface as shown in Fig. 18(a). The opening width d12 of each isosceles trapezoidal cutout may be wider or narrower than the opening width d of cutout 1a, etc. The radial depth (length) L12 of each isosceles trapezoidal cutout is shorter than the opening width d12.

[0082] According to this modification, the cross-sectional area through which the leakage flow fS passes changes in the radial direction, so that the radial distribution of the flow velocity and flow rate of the leakage flow fS can be changed to an appropriate distribution.

[0083] As shown in Fig. 18(c), the inducer 13 of the third modification includes oblique cutouts 13a, 13b, and 13c as cutouts replacing the cutouts 1a, 1b, and 1c of the inducer 1. Each oblique cutout is obtained by rotating the cutout 1a, etc. of the embodiment by an angle θ around the open end with respect to a straight line C0 extending in the radial direction of the blade. The inclination angle of each oblique cutout is not particularly limited.

[0084] This modified example shows that the extending direction of the cutout portion does not have to coincide with the radial direction. The inclination direction of each oblique cutout is not particularly limited. In the example shown in Figure 18(c), each oblique cutout is inclined in the opposite direction to the rotation direction of the inducer 13 as it moves radially inward. The inclination direction of each oblique cutout may be the opposite direction. In the case of an oblique cutout, the depth of the cutout can be defined as the depth of the center of the oblique cutout in the width direction. According to this modification, the outlet of the leakage flow fS toward the suction surface can be shifted in the circumferential direction as it advances in the radial direction.

[0085] [Fourth and fifth variants] Next, fourth and fifth modifications of this embodiment will be described. 19(a) and 19(b) are schematic circumferential cross-sectional views showing examples of inducers according to modifications (fourth and fifth modifications) of the embodiment of the present invention. The following description will focus on the differences from the embodiment.

[0086] 19(a), in the inducer 14 of the fourth modification, chamfered portions 14a are formed at the corners formed by the inner edges of the notches 1a, 1b, and 1c of the inducer 1 and the surface S1. Similarly, chamfered portions 14b are formed at the corners formed by the inner edges of the notches 1a, 1b, and 1c of the inducer 1 and the surface S2. The specific shape of the chamfered portions 14a, 14b is not particularly limited as long as the leakage flow fS passing through each notch flows smoothly. For example, Fig. 19(a) shows an example in which the chamfered portions 14a, 14b are C-chamfered portions that intersect with the inner surfaces of the notches at a 45° angle. However, the intersection angle of the chamfered portions 14a, 14b is not limited to 45°.

[0087] Alternatively, the chamfered portions 14a and 14b may be formed with a curved surface such as an arc. It is more preferable that the inner surface of each cutout portion where the chamfered portions 14a and 14b are formed is the inner surface on the opposite side to the rotation direction R of the inducer 14, as shown in FIG. 19(a). According to this modification, the chamfered portions 14a and 14b allow the leakage flow fS passing through each notch to flow more smoothly, thereby reducing the negative pressure region formed by the leakage flow fS, and as a result, reducing the cavities generated downstream of each notch.

[0088] As shown in Figure 19(b), the inducer 15 of the fifth modified example has diagonal cutouts 15a, 15b, and 15c (hereinafter sometimes referred to as the individual diagonal cutouts) as cutouts replacing the cutouts 1a, 1b, and 1c of the inducer 1. Each oblique cutout has inner surfaces 15d, 15e that are inclined in the opposite direction to the rotation direction R from surface S1 toward surface S2. The inner surfaces 15d, 15e may be parallel or non-parallel. In the example shown in Figure 19(b), they are parallel to each other. Each oblique cutout extends toward the central axis O, similarly to the embodiment. According to this modification, the leakage flow fS passes along the inner surfaces 15d and 15e of the cutouts, so that the leakage flow fS flows more smoothly. This reduces the negative pressure area formed by the leakage flow fS. As a result, it is possible to reduce cavities occurring downstream of each oblique cutout.

[0089] In the above embodiment and each modified example, an inducer used in a turbopump 100 that is particularly suitable for rocket engines has been described as an example, but the inducer described in the above embodiment and each modified example may also be used in turbopumps other than turbopumps for rocket engines. Even in general industrial pumps, deterioration of suction performance and damage due to cavitation can occur. The inducer of the present invention can suppress deterioration of suction performance and damage due to shaft vibration caused by cavitation instability, even when used in industrial pumps. Examples of industrial pumps that can use the inducer of the present invention include pumps for LNG (liquefied natural gas) and pumps for liquid hydrogen, which are essential in a hydrogen society.

[0090] In the above embodiment and each modified example, an example has been described in which the inducer has three blades. However, the inducer may have two or more blades, as long as the number of blades is multiple. For example, if the number of blades is n (where n is an integer of 2 or more), it is more preferable that each blade is provided with a notch at a position that is n-fold rotationally symmetric (axially symmetric) about the central axis of the inducer when viewed in the axial direction. However, if it is possible to suppress the cavitation instability phenomenon and improve the suction performance required for the inducer, the notches may be provided asymmetrically about the axis.

[0091] In the above embodiment and each modified example, the leading edge of each blade is described as having an arc-shaped protrusion when viewed in the axial direction. However, the shape of the leading edge of each blade is not limited to this. For example, the leading edge of each blade may have a convex shape other than an arc, or may have a linear or concave shape.

[0092] In the above embodiment and each modified example, the cutout portion of each blade is formed so as to open at the blade tip of the downstream blade that overlaps the position where the blade tip of the upstream blade begins as viewed from the axial direction. However, the cutout portion may be formed in the throat T region where the blade tips of the upstream and downstream blades overlap, or may be formed in the throat T further upstream. Furthermore, the cutout portion may be formed in a region that does not overlap with the upstream blade as viewed from the axial direction.

[0093] In the above embodiment and each modified example, an example in which one notch is formed in each blade has been described. However, the number of notches in each blade may be one or more. If the notches are arranged non-axially symmetrically, some blades may not have any notches.

[0094] In the fourth modified example, the chamfered portions 14a, 14b are formed on the inner surface of each cutout on the side opposite to the rotational direction R. However, the chamfered portions 14a, 14b may also be formed on the inner surface of the cutout in the rotational direction R, or may be formed only on the inner surface of the cutout in the rotational direction R. Furthermore, either one of the chamfered portions 14a and 14b may be omitted.

[0095] Although the preferred embodiment and modifications of the present invention have been described above, the present invention is not limited to these embodiments and modifications. Additions, omissions, substitutions, and other modifications of the configuration are possible within the scope of the present invention. Furthermore, the present invention is not limited by the foregoing description, but is limited only by the appended claims. [Explanation of symbols]

[0096] 1, 11, 12, 13, 14, 15... inducer, 1a, 1b, 1c...notch portion, 1A...first blade (wing), 1Aa, 1Ba, 1Ca... inlet end, 1Ab, 1Bb, 1Cb... blade body, 1B...2nd blade (vane), 1C...3rd blade (vane), 1D hub (shaft body), 1g, 11g, 12g...tip, 10...casing, 10e...tubular part, 100...Turbo pump, b...Width, Ca...Cavity, f, fS...Leakage flow, DM...blade diameter, eA, eB, eC...leading edge, F, F1...fluid, h...depth, g...gap, O...Central axis, oA, oB, oC...Blade tip, R...Rotation direction, S1, S2...Surface, T...throat, Te...throat entrance, V...leakage vortex region.

Claims

1. a shaft body that is rotatably driven; a plurality of blades provided in a spiral pattern on the outer peripheral surface of the shaft, the leading edges of which are offset from each other in the circumferential direction when viewed in the axial direction from the most upstream side; each blade has a notch that opens at a radially outer edge excluding the leading edge, and is located counterclockwise from the outer peripheral end of the leading edge of the blade as viewed in the axial direction from the most upstream side, and is formed at symmetrical positions about the central axis of the shaft as viewed in the axial direction from the most upstream side; The notch has a width (b) and a depth (h), In a graph showing the relative ratio (b / DM) of the width (b) to the diameter (DM) of the blade on the horizontal axis and the relative ratio (h / DM) of the depth (h) to the diameter (DM) on the vertical axis, points A1 (0.039, 0.197), A2 (0.118, 0.270), A3 (0.158, 0.197), A4 (0.178, 0.132), A5 (0.178, 0.066), and A6 (0.132, 0.039) are used, In the relationship between the width and depth of the notch, the relative ratio of the width and the depth to the diameter is within a range surrounded by points A1, A2, A3, A4, A5, and A6 on the graph. Inducer.

2. An inducer as described in claim 1, wherein, when the plurality of blades are viewed axially from the upstream side, the notch formed in a particular blade is located in a position that does not overlap with the blade one downstream.

3. When viewing the plurality of blades in the axial direction from the upstream side, the notch is located at a blade tip position between the inlet end end point, which is the position where the leading edge of the inlet end of a specific blade reaches the blade tip, and the inlet end end point, which is the position where the leading edge of the inlet end of the blade one blade downstream from the specific blade reaches the blade tip. The inducer of claim 1 .

Images