JP6032976B2 - Steam injector - Google Patents

Description

  The present invention relates to a steam injector in which a liquid nozzle is disposed in a gas nozzle.

Conventionally, a steam injector has been used for supplying water to a steam locomotive or a boiler. For example, a steam injector having a configuration as shown in FIG. 8 is known.
This steam injector 1 is provided with a steam inlet 11, a water suction port 12 and an overflow drain pipe 13 on the side surface of a casing 2, a gas nozzle 3 in the casing 2, and a liquid nozzle 4 in the gas nozzle 3. Is provided. A mixing space 6 is provided on the discharge side of the liquid nozzle 4 in the gas nozzle 3. It is connected to the diffuser 8 having the throat portion 34 on the discharge side of the mixing space 6. An overflow drain port 9 is provided on the downstream side of the diffuser 8. The overflow drain port 9 and the overflow drain pipe 13 are in communication with each other (see, for example, Patent Document 1).

  In such a steam injector 1, when a liquid jet is discharged from the liquid nozzle 4, the liquid jet flows into the gas jet in the gas nozzle 3, so that the steam flows into the mixing space 6 while being condensed by water. . At this time, the pressure in the mixing space 6 mixes the steam and water and becomes negative pressure due to the condensation of the steam to be equal to or lower than the atmospheric pressure, and flows into the mixing space 6 that has become negative pressure so that water is drawn. As a result, a high-speed water flow is generated at the throat portion 34 and water is supplied to the diffuser 8.

Further, when the high-speed water stream flows through the diffuser 8, the pressure is ideally increased by the pressure Δp expressed by the following equation according to Bernoulli's theorem.
Δp = 1/2 · ρ · U ²
(Ρ = density of liquid, U = flow velocity of water flow passing through throat part 34)
Thereby, the steam injector 1 can obtain a discharge pressure higher than the supply pressure of the steam. When the pressure becomes sufficiently high at the outlet side of the diffuser 8, the check valve is automatically opened to eject pressurized water. By repeating these steps, a large amount of water continues to be supplied to the steam injector 1.

When such a steam injector 1 is used in a large facility such as a nuclear power plant using a pressurized water reactor (PWR), a steam injector 1 having a large capacity and a high head capable of supplying a very large amount of water. It becomes necessary (see, for example, Patent Document 2).
However, in the large-capacity steam injector 1, in order to obtain a high discharge pressure, the thickness and length of the liquid jet are increased in order to sufficiently condense the steam by increasing the surface area of contact between the steam and water. There is a need.

JP-A-5-79499 Japanese Patent Publication No. 3327934

However, even if the shape of the vapor injector is made similar to increase the surface area of the liquid jet, the larger the size, the more difficult it is to transfer heat from the surface of the liquid jet to the center. For this reason, the efficiency of gas condensation decreases and the discharge pressure tends to decrease.
In this way, the operation of the steam injector itself is governed by the heat transfer phenomenon from the surface to the center of the liquid jet where the gas jet collides and condenses, so the larger the steam injector, the more efficiently the water can be condensed. There is a problem that becomes difficult.

  The present invention has been made to solve the above-described problems, and provides a steam injector capable of improving the gas condensing efficiency and increasing the discharge pressure.

In order to solve the above problems, the present invention proposes the following means.
The steam injector according to the present invention is a gas nozzle that extends in the axial direction, has a reduced diameter portion that decreases in diameter toward the leading end side that opens, and gas flows through the inside toward the leading end side And a liquid nozzle that is disposed at a distance from an inner wall surface of the reduced diameter portion with a distal end portion inside the reduced diameter portion facing the opening, and from which the liquid is ejected from the distal end portion, The tip includes a jet having a hole for jetting the liquid so as to go radially inward toward the opening, and the jet is disposed in contact with the inner wall surface of the tip, A curved outlet formed in a curved shape that protrudes in a protruding shape upstream from a convergence point on the axis with respect to the opening, and the hole has a curved shape of the curved outlet and characterized in that it is formed at an vertical That.

  According to such a configuration, the flow of liquid ejected from the hole (hereinafter referred to as “liquid jet”) is ejected so as to be directed radially inward, so that the liquid jet is ejected in the ejection direction (direction along the axis). In addition to the component to the flow, the component also flows in the direction toward the center of the liquid jet (direction toward the axial direction). Thereby, turbulence occurs in the liquid jet, and the area of the liquid in contact with the gas increases. As a result, the amount of heat exchanged between the gas and the liquid increases and the heat transfer efficiency increases, so that the condensation efficiency can be improved.

  Further, the steam injector of the present invention has a plurality of the hole portions, and each of the plurality of hole portions is inclined and extends so as to go radially inward toward the opening. It is characterized by that.

  According to such a configuration, by using a plurality of holes instead of one hole, a fine liquid jet can be ejected, the surface area of the liquid jet is increased, and the area of the liquid in contact with the gas is further increased. As a result, the amount of heat exchanged between the gas and the liquid is further increased and the heat transfer efficiency is increased, so that the condensation efficiency can be further improved.

  Further, the hole is formed so as to be recessed from the inner peripheral surface, and extends across both ends of the hole, and has a plurality of grooves adjacent to each other in the circumferential direction of the hole. Is inclined so as to be directed radially inward toward the opening.

  According to such a configuration, the surface area of the liquid jet is further increased, and the area of the liquid in contact with the gas is increased. As a result, the amount of heat exchanged between the gas and the liquid is further increased and the heat transfer efficiency is increased, so that the condensation efficiency can be further improved.

  In the vapor injector of the present invention, the hole ejects the liquid toward a convergence point on the axis between the tip and the opening.

  According to such a configuration, since the liquid jets converge toward one point and eject the liquid, the liquid jet can increase the flow velocity toward the convergence point, and the discharge pressure can be increased with an easy structure. .

  Furthermore, the steam injector of the present invention is characterized in that an uneven shape is formed on the inner wall surface of the reduced diameter portion.

  According to such a configuration, a gas flow (hereinafter referred to as a gas jet) that circulates on the outer peripheral side of the liquid jet is disturbed by the irregular shape, and is disturbed not only in the flow direction but also in the axial direction. As the gas jet agitates the surface of the jet, the area of the liquid in contact with the gas increases. As a result, the amount of heat exchanged between the gas and the liquid is further increased and the heat transfer efficiency is increased, so that the condensation efficiency can be further improved.

  According to the vapor injector of the present invention, since the liquid jet ejected from the hole flows together with the component in the center direction of the liquid jet as well as the component in the ejection direction, turbulence occurs in the liquid jet. The area of the liquid that comes into contact with the gas increases. Thereby, the amount of heat exchanged between the gas and the liquid is increased and the heat transfer efficiency is increased, so that the gas condensation efficiency can be improved and the discharge pressure can be increased.

1 is an overall view of a steam injector according to a first embodiment of the present invention. It is an enlarged view near the jet nozzle of the steam injector which concerns on 1st embodiment of this invention. It is an enlarged view near the jet nozzle of the steam injector which concerns on 2nd embodiment of this invention. It is an enlarged view near the jet nozzle of the steam injector which concerns on 3rd embodiment of this invention. It is an enlarged view near the jet nozzle of the steam injector which concerns on 4th embodiment of this invention. It is an enlarged view near the jet nozzle of the steam injector which concerns on 5th embodiment of this invention. It is an enlarged view near the jet nozzle of the steam injector which concerns on 6th embodiment of this invention. It is a general view of the steam injector using a prior art.

Hereinafter, a first embodiment according to the present invention will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1, the steam injector 1 of the first embodiment is covered with a bottomed cylindrical casing 2 centering on an axis O (left and right direction on the paper surface). The casing 2 is disposed with the bottomed side facing the upstream side (the left side of the paper). Inside the casing 2, a gas nozzle 3 that extends along the direction of the axis O and opens toward the downstream side (the right side in the drawing), and a cylindrical liquid nozzle that is coaxially arranged inside the gas nozzle 3. 4, an ejection port 5 disposed at an opening on the downstream side of the liquid nozzle 4, a mixing space 6 that is a space in the gas nozzle 3 from the ejection port 5 to the opening of the gas nozzle 3, and an upstream side of the liquid nozzle 4 A water storage tank 7 disposed in communication with the opening is provided.

Further, the casing 2 is arranged coaxially with the gas nozzle 3 and penetrates the diffuser 8 connected to the opening of the gas nozzle 3 and the middle of the side wall of the gas nozzle 3 in the vertical direction (vertical direction in the drawing). An overflow drain port 9 is provided, and a drain tank 10 communicating with the overflow drain port 9 is provided.
A cylindrical side surface of the casing 2 is disposed upstream and is disposed in the vicinity of the center with a water inlet 12 communicating with the water storage tank 7 and having a cylindrical shape protruding vertically upward and having a bottom opening. A steam intake 11 that protrudes vertically downward in a cylindrical shape and communicates with the gas nozzle 3, and an overflow drain that is also disposed near the center and protrudes vertically upward in a cylindrical shape and communicates with the drain tank 10. A tube 13 is provided.

The gas nozzle 3 extends along the direction of the axis O in the vicinity of the center in the casing 2, and has a reduced diameter portion 31 formed with the axis O as a center toward the downstream opening, and a reduced diameter portion 31. A throat portion 34 that is the distal end side of the first and second ends, and a disc portion 33 that is arranged with the end face on the upstream side of the reduced diameter portion 31 closed and formed around the axis O.
The reduced diameter portion 31 has a cross-sectional ring shape centered on the axis O, and is formed so that the inner diameter decreases toward the downstream opening. The throat portion 34 is connected to the diffuser 8 and the gas nozzle 3, and is formed at the most reduced diameter position on the distal end side of the reduced diameter portion 31. The disk portion 33 is disposed so as to close the opening on the upstream side of the reduced diameter portion 31, has a disk shape centered on the axis O, and has a circular liquid nozzle insertion hole centered on the axis O at the center portion. 33a.

The liquid nozzle 4 has a cylindrical shape, is coaxially disposed inside the gas nozzle 3, is spaced from the outer wall surface 41 from the reduced diameter portion inner wall 32, and is spaced apart from the throat portion 34 at the downstream side opening. Arranged. The liquid nozzle 4 is inserted through the liquid nozzle insertion hole 33a and communicated with the water storage tank 7 through an opening on the upstream side.
The spout 5 has a disk shape centered on the axis O, and is disposed in contact with the inner wall surface 42 of the opening on the downstream end of the liquid nozzle 4, and has a circular hole centered on the axis O 51 is the center. The hole 51 is formed by an inclined surface 51a that is inclined so as to be directed radially inward toward the downstream side. The inclined surface 51a is inclined so that the extended line converges toward one point (convergence point) on the axis O in the vicinity of the throat portion 34.
The mixing space 6 is formed by a space in the gas nozzle 3 between the throat portion 34 and the jet outlet 5.

The water storage tank 7 has a cylindrical space along the vertical direction, and the side surface thereof is arranged to communicate with the opening on the upstream side of the liquid nozzle 4.
The diffuser 8 has a ring shape in section with the axis O as the center, and is formed while gradually increasing the inner wall surface from the throat portion 34. And one opening is connected with the gas nozzle 3 by the throat part 34, and the opposite opening is connected to the supply destination.
The overflow drain port 9 is disposed in the vicinity of the middle of the gas nozzle 3 so as to penetrate the side wall of the gas nozzle 3 in a circular shape in the vertical direction.
The drainage tank 10 has a cylindrical space along the vertical direction, and is disposed so as to cover the overflow drainage port 9 from the radially outer side. The drain tank 10 communicates with the gas nozzle 3 through the overflow drain port 9.

The water suction port 12 is disposed on the upstream side in the casing 2, has a cylindrical shape along the vertical direction, and penetrates the side surface of the casing 2 so as to protrude vertically upward. The bottom surface communicates with the upper surface side of the water storage tank 7.
The steam inlet 11 is disposed near the center in the casing 2, has a cylindrical shape along the vertical direction, and is formed to penetrate the side surface of the casing 2 and protrude downward in the vertical direction. The upper surface communicates with the side surface of the reduced diameter portion 31 of the gas nozzle 3.
The overflow drain pipe 13 is disposed in the vicinity of the center in the casing 2, has a cylindrical shape along the vertical direction, and penetrates the side surface of the casing 2 so as to protrude vertically upward. The bottom surface communicates with the upper surface side of the drainage tank 10.

Next, the operation of the steam injector 1 according to the first embodiment having the above configuration will be described.
When water is supplied using the steam injector 1 having such a configuration, low-temperature water is introduced from the water suction port 12 and fed into the water storage tank 7. At the same time, high-temperature steam flows from the steam inlet 11 and is sent into the mixing space 6 as a gas jet (hereinafter referred to as a steam jet S) along the inner wall surface 42 of the gas nozzle 3. The water sent to the water storage tank 7 flows through the liquid nozzle 4 and is ejected as a liquid jet (hereinafter referred to as a water jet W) from the jet outlet 5. The ejected water jet W comes into contact with the steam jet S at the same time as it is ejected, flows into the mixing space 6 while condensing the steam, and becomes a high-speed water stream when reaching the throat portion 34. The water that has become a high-speed water stream is pressurized and flows through the diffuser 8 and discharged to the supply destination.
Further, when the discharge amount to the supply destination is reduced, the water in the gas nozzle 3 flows into the drainage tank 10 through the overflow drainage port 9 and excess water is discharged from the overflow drainage pipe 13 to the outside. The

According to the steam injector 1 of the first embodiment as described above, the water jet W ejected from the hole portion 51 of the ejection port 5 is ejected along the inclined surface 51 a and is near the throat portion 34 of the mixing space 6. It is ejected so as to converge at a convergence point which is one point on the axis O.
Thereby, since the water jet W ejected from the hole 51 is ejected so as to be directed radially inward, the water jet W has not only a component in the ejection direction but also a component in the center direction of the water jet W. It will flow together. By the component in the central direction of the water jet W, the water flowing on the surface of the water jet W is disturbed, and the water in contact with the steam jet S on the surface is replaced, thereby increasing the amount of water in contact with the steam, Increases contact area with water. This increases the amount of heat exchanged between the steam and water and increases the heat transfer efficiency, so that the steam condensation efficiency can be improved.
Further, since the water jet W is converged and ejected toward one point, the cross-sectional area of the water jet W is smaller at the time of convergence than at the time of ejection, so that the flow velocity is increased. As a result, a high-speed water flow can be easily obtained at the throat portion 34, and the discharge pressure can be increased with an easy structure in which the inclined surface 51a is simply provided in the hole 51.

Next, the steam injector 1 of the second embodiment will be described with reference to FIG.
In the second embodiment, the same components as those in the first embodiment are given the same reference numerals, and detailed description thereof is omitted. The steam injector 1 of the second embodiment is different from the first embodiment with respect to the hole 51.

  That is, in the second embodiment, a plurality of small hole portions (hole portions) 52 are formed in the jet nozzle 5 instead of the hole portions 51. The small hole portions (hole portions) 52 have a circular shape and are radially spaced apart from each other about the axis O at a plurality of locations of the ejection port 5, and each small hole has an inclined surface 51 a. doing.

  According to the steam injector 1 of the second embodiment as described above, a plurality of small holes (holes) 52 are formed instead of a single hole 51 so that a plurality of holes 51 are formed from a single jet port 5. The fine water jet W can be ejected, the surface area of the water jet W is increased, and the contact area between the steam and water is further increased. As a result, the amount of heat exchanged between the steam and water is increased and the heat transfer efficiency is increased, so that the steam condensation efficiency can be further improved.

  In addition, there is no restriction | limiting in the magnitude | size, the number, and arrangement | positioning of the small hole part (hole part) 52, many small holes may be arrange | positioned with respect to the jet nozzle 5, and conversely, a large number of small holes may be arranged. Further, the arrangement may be uneven.

Next, the steam injector 1 of 3rd embodiment is demonstrated with reference to FIG.
In the third embodiment, the same components as those in the first embodiment are given the same reference numerals, and detailed description thereof is omitted. The steam injector 1 of the third embodiment is different from the first embodiment with respect to the jet port 5.

  That is, in the third embodiment, instead of the jet nozzle 5, a curved jet nozzle (saddle outlet) 50 is provided. The curved surface outlet 50 is disposed in contact with the inner wall 42 of the opening at the downstream end of the liquid nozzle 4 and protrudes upstream from a point on the axis O in the vicinity of the throat portion 34. It is formed to have a curved shape that bends in a straight line. Further, the hole 51 of the curved surface outlet (slag outlet) 50 includes a plurality of vertical small holes (holes) 501. The vertical small hole portion (hole portion) 501 is formed by forming a circular hole perpendicular to the curved surface shape of the curved surface ejection port (spout port) 50, and is radially spaced from the axis O at a plurality of locations. Be placed.

According to the steam injector 1 of the third embodiment as described above, the hole 51 is formed not by one hole 51 but by a plurality of vertical small holes (holes) 501, so that one curved jet port ( A plurality of fine water jets W can be ejected from the eaves outlet 50, the surface area of the water jet W is further increased, and the contact area between the steam and water is increased. As a result, the amount of heat exchanged between the steam and water is further increased and the heat transfer efficiency is increased, so that the steam condensation efficiency can be further improved.
Furthermore, by making the jet nozzle 5 itself into a curved surface shape, it becomes possible to adjust the convergence point of the water jet W with the curvature of the curved jet nozzle (slag outlet) 50 instead of the hole 51. Thereby, it becomes possible to form the jet outlet 5 such that the water jet W is more easily directed toward the convergence point.

Next, the steam injector 1 of the fourth embodiment will be described with reference to FIG.
In the fourth embodiment, the same components as those in the first embodiment are given the same reference numerals, and detailed description thereof is omitted. The steam injector 1 according to the fourth embodiment is different from the first embodiment with respect to the ejection port 5.

  That is, in the fourth embodiment, a star-shaped hole (hole) 53 is formed instead of the hole 51 of the jet nozzle 5. The star-shaped hole portion (hole portion) 53 is formed in a star shape by arranging a plurality of V-shaped grooves so as to be adjacent to each other along the inner peripheral surface, and the groove is an extension of the bottom 51b. The lines are inclined and arranged so as to converge toward one point (convergence point) on the axis O in the vicinity of the throat portion 34.

  According to the steam injector 1 of the fourth embodiment as described above, the surface area of the water jet W is further increased and the contact area between the steam and water is increased by forming the star shape rather than the circular shape. As a result, the amount of heat exchanged between the steam and water is further increased and the heat transfer efficiency is increased, so that the steam condensation efficiency can be further improved.

  Note that the star-shaped hole (hole) 53 is not limited to a star shape, and it is only necessary to have a plurality of grooves adjacent to each other in the circumferential direction of the hole 51 on the inner peripheral surface. For example, a cross shape can be mentioned. Moreover, the groove | channel formed so that it may dent from an internal peripheral surface is not limited to arrange | positioning equally.

Next, the steam injector 1 of the fifth embodiment will be described with reference to FIG.
In the fifth embodiment, the same components as those in the first embodiment are given the same reference numerals, and detailed description thereof is omitted. The steam injector 1 of the fifth embodiment is different from the first embodiment with respect to the inner diameter wall 32 of the gas nozzle 3.

  That is, in the fifth embodiment, the inner diameter wall 32 of the reduced diameter portion is disposed over the circumferential direction centering on the axis O and spaced apart from the convex portion 32a, with the convex portion 32a disposed about the axis O and the center. And a recess 32b. The convex portion 32 a is formed to project from the surface of the reduced diameter portion inner wall 32 with a triangular cross section, and is disposed in the mixing space 6 along the circumferential direction with the axis O as the center. The concave portion 32b is formed to be recessed in a triangular shape from the inner surface 32 of the reduced diameter portion. The concave portion 32b is separated from the convex portion 32a in the mixing space 6 upstream of the convex portion 32a and is circumferentially centered about the axis O. It is arranged over.

According to the steam injector 1 of the fifth embodiment as described above, when the steam jet S flows along the inner wall 32 of the reduced diameter portion, the flow is disturbed by the convex portion 32a and the concave portion 32b, and the direction is in the direction of the axis O. Flow occurs. Therefore, the steam jet S flows so as to hit the water jet W, and by stirring the surface of the water jet W, the amount of water in contact with the steam increases, and the contact area between the steam and water further increases. This further increases the amount of heat exchanged between the steam and water, increases the heat transfer efficiency, and further improves the steam condensation efficiency.
In addition, the convex part 32a and the recessed part 32b should just be able to stir the steam jet S, and are not limited to the shape and number of this embodiment. For example, a ring-shaped concavo-convex shape having a rectangular cross-section or a spiral concavo-convex shape proceeding in the direction of the axis O along the reduced diameter inner wall 32 may be used.

Next, the steam injector 1 of 6th embodiment is demonstrated with reference to FIG.
In the sixth embodiment, the same components as those in the first embodiment are given the same reference numerals, and detailed description thereof is omitted. The steam injector 1 of the sixth embodiment is different from the first embodiment with respect to the inner diameter wall 32 of the reduced diameter portion of the gas nozzle 3.

  In other words, in the sixth embodiment, the fan 32 c is arranged on the reduced diameter inner wall 32 near the ejection port 5 between the reduced diameter inner wall 32 and the outer wall surface 41 of the liquid nozzle 4. The fan 32c has a structure that rotates when gas flows in the direction of the axis O.

According to the steam injector 1 of the sixth embodiment as described above, the steam jet S passes through the fan 32 c when it flows along the inner wall 32 of the reduced diameter portion. At that time, the fan 32c rotates and the steam jet S circulates while being stirred. Therefore, the steam jet S flows so as to hit the surface of the water jet W, and by stirring the surface of the water jet W, the amount of water in contact with the steam is increased, and the contact area between the steam and water is further increased. To increase. As a result, the amount of heat exchanged between the steam and water can be further increased, the heat transfer efficiency can be increased, and the steam condensation efficiency can be further improved.
In addition, it is not limited to the structure of this embodiment of the fan 32c, You may be set as the structure which has a drive system and rotates independently.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the configurations and combinations of the embodiments in the embodiments are examples, and the addition and omission of configurations are within the scope not departing from the gist of the present invention. , Substitutions, and other changes are possible. Further, the present invention is not limited by the embodiments, and is limited only by the scope of the claims.
That is, in each embodiment, although the thing of the various aspect was demonstrated about the structure of the hole 51 of the jet nozzle 5, and the structure of the reduced diameter part inner wall 32 of the gas nozzle 3, the steam injector 1 which combined these two or more It may be. For example, the steam injector 1 can be formed by forming the small hole portion (hole portion) 52 and then providing the convex portion 32a and the concave portion 32b on the inner wall 32 of the reduced diameter portion.

In the present embodiment, the combination of gas and liquid to be used is a combination of steam and water. However, the present invention is not limited to this, and may be appropriately selected according to the required environment. For example, a combination of organic vapor and ethylene glycol may be used.
Furthermore, although the hole 51 and the small hole (hole) 52 are inclined so as to converge toward one point (convergence point), the present invention is not limited to this. For example, it may be merely inclined so as to go radially inward without converging.

O ... axis 1 ... steam injector 2 ... casing 3 ... gas nozzle 4 ... liquid nozzle 5 ... spout 6 ... mixing space 7 ... water storage tank 8 ... diffuser 9 ... overflow drain port 10 ... drain tank 11 ... steam inlet 12 ... water Suction port 13 ... Overflow drain pipe W ... Water jet S ... Steam jet 31 ... Reduced diameter portion 32 ... Reduced diameter portion inner wall 33 ... Disc portion 34 ... Throat portion 33a ... Liquid nozzle insertion hole 41 ... Outer wall surface 42 ... Inner wall surface 51 ... Hole 51a ... Inclined surface 51b ... Bottom 52 ... Small hole part (hole part) 50 ... Curved surface outlet (saddle outlet) 501 ... Vertical small hole part (hole part) 53 ... Star-shaped hole part (hole part) 32a ... Convex Part 32b ... Recess 32c ... Fan

Claims (5)

A gas nozzle that extends in the axial direction, has a reduced diameter portion that decreases in diameter toward the leading end side that opens, and a gas nozzle through which gas flows toward the leading end side;
A liquid nozzle that is disposed with a space from the inner wall surface of the reduced diameter portion with the distal end portion inside the reduced diameter portion facing the opening, and that ejects liquid from the distal end portion,
The tip includes a jet nozzle having a hole for jetting the liquid so as to go radially inward toward the opening,
The jet outlet is disposed in contact with the inner wall surface of the tip, and is formed in a curved shape that protrudes in a protruding manner upstream with a convergence point on the axis between the opening and the opening. Curved spout,
The steam injector is characterized in that the hole portion is formed perpendicular to a curved surface shape of the curved surface ejection port . A plurality of the holes are formed,
2. The steam injector according to claim 1, wherein each of the plurality of hole portions is inclined and extended so as to be directed radially inward toward the opening. The hole is formed so as to be recessed from the inner peripheral surface, extends across both ends of the hole, and has a plurality of grooves adjacent to each other in the circumferential direction of the hole;
2. The steam injector according to claim 1, wherein each of the grooves is inclined so that a bottom portion is directed radially inward as the opening is directed to the opening.   4. The steam injector according to claim 1, wherein the hole ejects the liquid toward a convergence point on the axis between the tip and the opening. 5.   The steam injector according to any one of claims 1 to 4, wherein an uneven shape is formed on an inner wall surface of the reduced diameter portion.

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