JP6392643B2 - rectifier - Google Patents

Description

  The present invention relates to a rectifier that is connected in the middle of a pipe in which a fluid flows in one direction and rectifies a turbulent flow of the fluid.

  Conventionally, as this kind of rectifier, one in which three or more ring plates and discs are arranged alternately on the same axis and rectified by bending an ultrasonic propagation path a plurality of times is known. (For example, refer to Patent Document 1).

Japanese Unexamined Patent Publication No. 2004-19844 (FIGS. 1, 2, and 6)

  However, the conventional rectifier described above cannot provide a sufficient rectifying effect.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a rectifier having a higher rectification effect than before.

  In order to achieve the above object, the invention of claim 1 is characterized in that a pipe-type case connected in the middle of a pipe through which a fluid flows in one direction and an inner diameter of an axially intermediate portion of the pipe-type case are expanded. An intermediate enlarged portion and an upstream small diameter portion on the upstream side thereof, and a rectifying filter accommodated in the intermediate enlarged portion, wherein the rectifying filter has a plurality of annular shapes surrounding a central axis of the pipe-shaped case. A ring structure having a ring portion and a center member that covers one end opening of the cylindrical portion from the opposite side to the upstream small diameter portion, and the upstream small diameter portion An opening side end of the cylindrical portion is connected to a downstream opening edge, and is a rectifier provided with a terminal taper guide that protrudes from the center member opposite to the upstream small diameter portion and gradually decreases in diameter toward the front. .

  The invention according to claim 2 is the rectifier according to claim 1, wherein the distal taper guide has a taper gradient on the distal end side that is smaller than that on the proximal end side from an intermediate position in the axial direction.

  According to a third aspect of the present invention, the pipe-shaped case is provided with a downstream small-diameter portion that is reduced in a stepped shape from a downstream end portion of the intermediate enlarged-diameter portion, and a distal end portion of the end tapered guide is the It is a rectifier of Claim 1 or 2 in which the downstream small diameter part has plunged.

  The invention according to claim 4 is the rectifier according to any one of claims 1 to 3, wherein each of the ring guides has a tapered shape whose diameter is increased in a direction away from the upstream small diameter portion. is there.

  According to a fifth aspect of the present invention, the center member and the plurality of ring guides are formed with bolt insertion holes through which a common bolt passes, and adjacent to the surface of the plurality of ring guides on the center member side. The rectifier according to any one of claims 1 to 4, further comprising a spacer protrusion for forming the annular gap between the ring guide and the center member to be fitted.

  A sixth aspect of the present invention is the rectifier according to any one of the first to fifth aspects, wherein a mesh that covers the cylindrical portion from the outside or the inside is provided.

  According to a seventh aspect of the present invention, the pipe-shaped case is provided with a downstream small-diameter portion that is reduced in a stepped shape from a downstream end portion of the intermediate enlarged portion, and the intermediate enlarged portion and the downstream side are provided. 5. The corner arc surface between the step surface with the small-diameter portion and the inner peripheral surface of the downstream-side small-diameter portion includes a corner arc surface that is continuous with the step surface and the inner peripheral surface. A rectifier according to claim.

  In the rectifier according to claim 1, the rectifying filter provided in the intermediate enlarged portion of the pipe-shaped case has a cup structure in which one end opening of a cylindrical portion formed by laminating a plurality of ring guides with an annular gap is covered with a center member. Since the opening end of the cylinder part is connected to the downstream opening edge of the upstream small diameter part, all fluid flows into the cylindrical part from the upstream small diameter part and is divided into a plurality of annular gaps. The turbulent flow is rectified. In addition, the terminal taper guide that protrudes from the center member to the opposite side of the small diameter part on the upstream side and gradually reduces the diameter toward the front is provided, so that the occurrence of a turbulent flow of fluid after passing through the rectifying filter is suppressed. Can do. Thus, according to the present invention, it is possible to provide a rectifier having a higher rectification effect than before. If acoustic noise propagates through the fluid from the upstream side, the acoustic noise is restricted from going straight by the rectifying filter, and is greatly attenuated by repeated reflection between the opposing surfaces on both sides of the annular gap. . That is, the rectifier of the present invention can also provide a silencing effect.

  If the taper gradient on the distal end side of the distal tapered guide is made smaller than the proximal end side from the axial intermediate position, the fluid flows more smoothly and passes through the rectifying filter. Generation | occurrence | production of the turbulent flow of the following fluid can be suppressed.

  In the rectifier according to claim 3, the downstream small-diameter portion protrudes from the distal end portion of the end taper guide, so that the fluid smoothly flows into the downstream small-diameter portion, and turbulence occurs in the portion where the fluid flows from the intermediate enlarged portion into the downstream small-diameter portion. The generation of excessive flow can be suppressed.

  In the rectifier according to claim 4, each ring guide has a tapered shape whose diameter is increased in a direction away from the upstream small diameter portion, so that the fluid flows obliquely forward from the annular gap, Pressure loss is reduced and the rectifying effect is improved compared to the one that flows to the side.

  In the rectifier according to the fifth aspect of the present invention, it is possible to form an annular gap between adjacent ring guides or center members simply by putting the plurality of bolts through the bolt insertion holes of the center member and the plurality of ring guides.

  In the rectifier according to the sixth aspect, the rectifying effect is improved by providing the mesh covering the outside of the cylindrical portion.

  The rectifier according to claim 7 includes a corner arc surface that is continuous with the inner circumferential surface of the downstream small-diameter portion and the stepped surface of the intermediate large-diameter portion and the downstream small-diameter portion of the pipe-shaped case, so that the fluid flows downstream. It is possible to smoothly flow into the small-diameter portion and suppress the occurrence of a turbulent flow in the portion flowing from the intermediate enlarged portion into the upstream small-diameter portion.

1 is a side sectional view of an ultrasonic flowmeter having a rectifier according to a first embodiment of the present invention. Partially enlarged side sectional view of ultrasonic flowmeter Disassembled perspective view of rectifying filter Disassembled side view of rectifying filter Sound absorption sleeve perspective view Disassembled perspective view of sound absorbing sleeve Side sectional view of an ultrasonic flowmeter having a rectifier of the second embodiment Conceptual diagram for explaining the experimental method of the first embodiment The graph which shows the experimental result of Example 1 of 1st Example The graph which shows the experimental result of the implementation product 2 of 1st Example The graph which shows the experimental result of the comparative product 1 of 1st Example Monitor display of experimental results of the second embodiment First graph showing experimental results of the third embodiment 2nd graph which shows the experimental result of 3rd Example

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. As shown in FIG. 1, the rectifier 30 of this embodiment is provided as a part of the ultrasonic flowmeter 10. In FIG. 1, reference numeral 11 denotes a pipe-shaped case according to the present invention, which extends in a straight line and has tapered screws 12 and 12 inside both ends. Then, for example, gas pipes 90 and 90 are connected to the taper screws 12 and 12, and a commercial gas (for example, argon gas, nitrogen gas, propane gas) is formed in one direction (the direction from the left to the right in FIG. 1) on the inner side. ) Flows as “fluid” according to the present invention.

  The inside of the pipe-shaped case 11 has an upstream side small diameter portion 13 according to the present invention where the upstream side taper screw 12 is formed, and in order from the upstream side small diameter portion 13 toward the downstream side, the intermediate expansion is performed. A diameter portion 14 and a downstream small diameter portion 15 are formed, and the other taper screw 12 is formed on the downstream side of the downstream small diameter portion 15. Further, the downstream side small diameter portion 15 has a slightly smaller inner diameter than the upstream side small diameter portion 13, and the intermediate diameter expanded portion 14 expands stepwise with respect to the upstream side small diameter portion 13 and the downstream side small diameter portion 15. It is a diameter. Further, a corner arc surface 15 </ b> A is formed at the opening edge of the downstream small-diameter portion 15 so as to be continuous with the step surface with the intermediate enlarged-diameter portion 14 and the inner peripheral surface of the downstream small-diameter portion 15.

  The pipe-shaped case 11 is divided into first to third case components 11A, 11B, and 11C in the axial direction. The first case component 11A and the second case component 11B are fitted and coupled at an intermediate position of the intermediate enlarged portion 14, and the second case component 11B and the third case component 11C are the downstream small-diameter portion. 15 are fitted and connected at the downstream end.

  At two locations on the inner surface of the downstream small-diameter portion 15, a pair of element receiving recesses 16, 16 are formed in a recess on a straight line that obliquely intersects the axial direction. The sound wave elements 17, 17 are received and face each other. Then, similarly to a known ultrasonic flow meter, the propagation time of the ultrasonic wave from one ultrasonic element 17 to the other ultrasonic element 17 and the ultrasonic wave from the other ultrasonic element 17 to one ultrasonic element 17 are as follows. The flow rate of the fluid passing through the downstream small diameter portion 15 is measured based on the difference from the propagation time of the sound wave, and the flow rate of the fluid is detected by multiplying the flow velocity by the fluid passage area of the downstream small diameter portion 15. Yes.

  An upstream side of the ultrasonic element 17 upstream of the ultrasonic flow meter 10 is a rectifier 30 according to the present invention, and a rectifying filter 20 according to the present invention is provided in the intermediate diameter enlarged portion 14. ing. The rectifying filter 20 has a cup structure in which one end of a cylindrical portion 23 formed by laminating a plurality of ring guides 21 is covered with a center member 24. Then, the opening side end of the cylindrical portion 23 is connected to the downstream opening edge of the upstream small diameter portion 13 so that the entire rectifying filter 20 is intermediately expanded from the step surface between the upstream small diameter portion 13 and the intermediate large diameter portion 14. It protrudes to the diameter portion 14 side.

  Specifically, each ring guide 21 is, for example, a resin molded product, and has a tapered shape that is gently inclined toward the side away from the upstream small-diameter portion 13 toward the outside in the radial direction, as shown in FIG. ing. In addition, the plurality of ring guides 21 other than the ring guide 21 at the end on the upstream side small diameter portion 13 side have the same slope of the tapered surfaces 21S and 21T on both the front and back sides. The ring guide 21 at the end on the upstream small diameter portion 13 side has a tapered surface 21S on the upstream small diameter portion 13 side that is steeper than the tapered surface 21S of the other ring guide 21, and the upstream small diameter portion 21S. It is adapted to be fitted into a recess 13 </ b> D formed at the opening edge of the portion 13.

  As shown in FIG. 3, bolt insertion holes 21 </ b> A are formed through a plurality of locations in the circumferential direction of each ring guide 21 in parallel to the center axis of the ring guide 21, and the center member 24 extends from the opening edge of each bolt insertion hole 21 </ b> A. A spacer protrusion 21B protrudes on the side (opposite the upstream small diameter part 13). Further, the tip surface of each ring guide 21 is inclined so as to be able to come into surface contact with the tapered surface 21S on the upstream small-diameter portion 13 side in another ring guide 21 arranged on the downstream side of the ring guide 21. Yes.

  As shown in FIG. 4, the surface of the center member 24 on the ring guide 21 side (upstream small diameter portion 13 side) is a tapered surface 24S having the same gradient as the tapered surface 21S of the ring guide 21, and an inner opening of the tapered surface 24S. And a circular flat surface 24F that closes the surface. In addition, an annular flat surface 24B orthogonal to the axial direction of the pipe-shaped case 11 is provided on the back side of the tapered surface 24S of the center member 24, and penetrates between the annular flat surface 24B and the tapered surface 24S. A plurality of bolt insertion holes 24A corresponding to the bolt insertion holes 21A of the ring guide 21 are formed. A plurality of common bolts B are inserted from the annular flat surface 24B side into the center member 24 and bolt insertion holes 24A, 21A of the plurality of ring guides 21 and formed at the opening edge of the upstream small diameter portion 13 (not shown). It is fastened to the female screw hole. As a result, as shown in FIG. 2, the plurality of ring guides 21 and the center member 24 are held in a state of being stacked in the axial direction of the pipe-shaped case 11 with the annular gap 22 therebetween, and the center member 24 group described above. The cylindrical portion 23 is configured, and one end opening of the cylindrical portion 23 is closed by the center member 24 from the opposite side to the upstream small diameter portion 13. Further, in this state, the downstream end surface (that is, the annular flat surface 24B) of the center member 24 is located closer to the downstream small diameter portion 15 than the center in the axial direction of the intermediate expanded diameter portion 14.

  As shown in FIG. 1, an end taper guide 25 according to the present invention is provided on the back side of the circular flat surface 24F of the center member 24. The terminal taper guide 25 has a tapered shape with a diameter gradually reduced toward the downstream side. Further, the distal taper guide 25 forms a proximal taper portion 25A from the proximal end portion to an intermediate position that is approximately 1/3 in the axial direction, and a distal taper portion 25B extends from the intermediate position to the distal end. In addition, the gradient of the distal end taper portion 25B is gentler than the proximal end taper portion 25A. In other words, the distal tapered guide 25 has a shape in which the distal tapered portion 25B is sharper and narrower than the proximal tapered portion 25A. Then, the distal end side projects into the downstream small diameter portion 15 from the axial intermediate position of the distal tapered portion 25B.

  The cylindrical portion 23 of the rectifying filter 20 is covered with a mesh 26 on the outside. Further, as shown in FIG. 2, the center member 24 and the ring guide 21 at the end on the upstream side small diameter portion 13 side have a slightly larger outer diameter than the other ring guide 21 groups, and the mesh 26 has a shaft. It moves in the direction so as not to leave the cylinder part 23.

  A sound absorbing sleeve 29 is fitted to the inner peripheral surface of the intermediate enlarged diameter portion 14. As shown in FIG. 5, the sound absorbing sleeve 29 is formed by winding a sheet-like sound absorbing member 27 (for example, sponge) around the outer side of the skeleton sleeve 28. Further, as shown in FIG. 6, the skeleton sleeve 28 has a plurality of axially extending portions of the intermediate enlarged portion 14 extending between a pair of support rings 28 </ b> A and 28 </ b> A fitted inside the intermediate enlarged portion 14. Contact is made at the contact bar 28B. Furthermore, a plurality of locking projections 28C that protrude straight outward from the connecting bar 28B are provided at a plurality of locations in the circumferential direction of the skeleton sleeve 28, and a plurality of locking hooks are provided at one location in the circumferential direction of the skeleton sleeve 28. 28F is formed on the outer surface of one connection bar 28B. Among the skeleton sleeves 28 group, a part of the locking hooks 28F constitutes a first locking hook 28G whose tip is bent to one side around the outer periphery of the skeleton sleeve 28, and the other part of the locking hooks 28F includes The distal end portion is a second locking hook 28 </ b> H bent to the other side around the outer periphery of the skeleton sleeve 28. Then, as shown in FIG. 5, the sound absorbing member 27 is wound around the skeleton sleeve 28 with one end hooked on the first locking hook 28G, and the other end hooked on the second locking hook 28H. ing. Further, the locking projections 28C group penetrate the sound absorbing member 27 on the front and back sides. As a result, the sound absorbing member 27 is fixed to the skeleton sleeve 28 to form a sound absorbing sleeve 29.

  This completes the description of the configuration of the rectifier 30 of the present embodiment. Next, the function and effect of the rectifier 30 will be described. In the rectifier 30 of this embodiment, the rectifying filter 20 provided in the intermediate diameter enlarged portion 14 of the pipe-shaped case 11 has an opening at one end of the cylindrical portion 23 formed by laminating a plurality of ring guides 21 with an annular gap 22 therebetween. Since the cup structure covered with the center member 24 is formed and the opening side end portion of the cylindrical portion 23 is connected to the downstream opening edge of the upstream small diameter portion 13, all the fluid flows from the upstream small diameter portion 13 to the cylindrical portion 23. After flowing into the interior, the air flow is divided into a plurality of annular gaps 22 and the turbulent flow is rectified. In addition, each ring guide 21 has a tapered shape whose diameter is increased in a direction away from the upstream small diameter portion 13, so that the fluid flows obliquely forward from the annular gap 22, and the fluid moves to the side. The pressure loss is reduced and the rectifying effect is improved as compared with the flow. Furthermore, the rectification effect is improved by covering the cylindrical portion 23 of the rectification filter 20 with the mesh 26 from the outside.

  Furthermore, since the end taper guide 25 that protrudes from the center member 24 opposite to the upstream small diameter portion 13 and gradually decreases in diameter toward the front is provided, the turbulent flow of fluid after passing through the rectifying filter 20 Can be suppressed. Further, the distal taper guide 25 has a smaller taper gradient on the distal end side than the proximal end side from the intermediate position in the axial direction, and the downstream small diameter portion 15 enters the distal end portion of the distal taper guide 25. As a result, the fluid smoothly flows into the downstream small-diameter portion 15, and the occurrence of a turbulent flow at the portion where the fluid flows from the intermediate enlarged portion 14 into the downstream small-diameter portion 15 can be sufficiently suppressed. In addition, the occurrence of a turbulent flow can be suppressed by providing the corner circular arc surface 15A at the opening edge of the downstream side small diameter portion 15. Thereby, according to the rectifier 30 of this embodiment, a higher rectification effect can be obtained than before.

  Further, when acoustic noise propagates through the fluid from the upstream side, the acoustic noise is restricted from going straight by the rectifying filter 20, and is greatly reflected by repeating reflection between the opposing surfaces on both sides of the annular gap 22. Attenuates. Further, the acoustic noise that could not be silenced by the annular gap 22 is absorbed by the sound absorbing member 27 that covers the inner peripheral surface of the intermediate enlarged diameter portion 14 after passing through the annular gap 22. As a result, the rectifier 30 of the present embodiment can also provide a silencing effect. The acoustic noise is, for example, in the vicinity of the frequency component of the ultrasonic wave used for measurement by the ultrasonic flow meter 10 among noises generated by a noise source such as a governor or a valve disposed in the vicinity of the ultrasonic flow meter 10. The noise of the frequency.

[Second Embodiment]
The ultrasonic flowmeter 10V of the above embodiment is different from the first embodiment only in the structure of the end taper guide 25C in the rectifying filter 20. The end taper guide 25C has a uniform gradient as shown in FIG. 7 so that the tip does not enter the downstream small diameter portion 15.

[Example 1]
The product 1 of the present invention having the same structure as the ultrasonic flow meter 10 of the first embodiment, the product 2 of the present invention having the same structure as the ultrasonic flow meter 10V of the second embodiment, and the ultrasonic flow meter The following experiment was performed using the comparative product 1 as an ultrasonic flowmeter that does not have the rectifier 30 in which the rectifying filter 20 and the intermediate diameter enlarged portion 14 are excluded from the tenth.

1. Experimental Method As shown in FIG. 8 (A), the detection results when the flow rate is gradually increased by connecting straight pipes to both ends of the ultrasonic flowmeters of Examples 1 and 2 and Comparative Example 1 are used as reference measurement data. Asked. Next, as shown in FIG. 8B, elbow pipes are connected to both sides of the implementation products 1 and 2 and the comparative product 1, and the elbow pipes are bent 90 degrees at a time so that the elbow pipes are rotated to the right (in FIG. 1). It was changed to “downward”, “upward”, “leftward” (upward in FIG. 1), and “downward”, and an error (that is, instrumental difference) between each measurement result and the above-described reference measurement data was obtained and graphed.

2. Experimental Result The experimental result of the implementation product 1 is shown in FIG. 9, the experiment result of the implementation product 2 is shown in FIG. 10, and the experiment result of the comparison product 1 is shown in FIG. As shown in FIG. 11, in the comparative product 1, simply changing from the straight pipe to the elbow pipe deviated from the allowable instrumental error range (see “instrument error frame” in the graph). On the other hand, as shown in FIG. 10, the product 2 may fall within the allowable instrumental error range depending on the bending direction of the elbow pipe, and the product 1 as shown in FIG. 9. The result was within the allowable instrumental range regardless of the bending direction of the elbow. As described above, the products 1 and 2 of the present invention were able to confirm a certain rectifying effect, and in particular, the product 1 was able to confirm a high rectifying effect. Further, when a rectifier is provided as in the case of the working products 1 and 2, a constant pressure loss occurs, but the pressure loss is substantially the same (for example, in the working product 1, 519.5 [Pa] at 150 [m3 / h], In the product 2, it was 520.1 [Pa] at 150 [m3 / h], and it was confirmed that the pressure loss was not substantially changed by the difference in the size of the end taper guides 25 and 25C.

[Example 2]
1. Experimental Method Using a fluid analysis simulator, the following first to third fluids are set so that the Reynolds numbers are the same, and these fluids are separated from the ultrasonic flowmeter 10 of the first embodiment. The distribution of the flow velocity when flowing through the product 3 having a structure excluding the receiving concave portion 16 and the ultrasonic element 17 is unified and displayed by color so that 1.5 times the set flow velocity becomes the maximum value.

First fluid: Air flowing at a flow rate of 10.5 [m / s] at atmospheric pressure Second fluid: Air flowing at a flow rate of 1.74 [m / s] at 500 [kPa] Third fluid: Flow rate at 500 [kPa] Propane gas flowing at 0.49 [m / s] The set flow rate is the average flow rate at the left inlet of FIG.

2. Experimental Result The simulation result of the first fluid is shown in FIG. 12A, the simulation result of the second fluid is shown in FIG. 12B, and the simulation result of the third fluid is shown in FIG. 12C. Actual simulation results are displayed in color.

  From these simulation results, it was found that when the Reynolds number is the same, the flow velocity distribution level (that is, the degree of flow development) is almost the same even if the flow velocity is different up to about 20 times. From this, it is considered that the same correction value can be applied to the flowmeter according to the Reynolds number even if the gas type or pressure changes by passing the rectifier which is the product 3 of the present invention.

[Example 3]
1. Experimental Method (1) First ultrasonic flowmeter 10 of the first embodiment is used to flow the following first to third fluids and compare changes in instrumental difference due to differences in Reynolds numbers Create a graph.
(2) A second graph in which the ultrasonic flowmeter 10 of the first embodiment is used to flow the first fluid and the following fourth fluid, and the change in instrumental difference due to the difference in Reynolds number is compared. Create
First fluid: Air at atmospheric pressure Second fluid: Air at 200 [kPa] Third fluid: Air at 500 [kPa] Fourth fluid: City gas at atmospheric pressure (so-called 13A gas)

2. Experimental Results The first graph is shown in FIG. 13, and the second graph is shown in FIG. From these graphs, it was confirmed that the instrumental performance was almost the same under the same Reynolds number even when the gas type and pressure were different.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.

(1) Although the rectifying filter 20 of the above embodiment is covered with the mesh 26 on the outer peripheral surface, it may not be covered with the mesh 26.

(2) In the rectifying filter 20 of the above-described embodiment, the portion of the center member 24 facing the upstream small diameter portion 13 through the cylindrical portion 23 is the circular flat surface 24F. The shape may be a shape that protrudes in a tapered shape or a shape that bulges into a dome shape, and the recessed surface on the back side of the terminal tapered guide 25 is directed to the upstream small diameter portion 13 side instead of the circular flat surface 24F. Also good.

(3) The rectifier 30 of the above embodiment is provided as a part of the ultrasonic flow meter 10, but may be separate from the ultrasonic flow meter 10.

DESCRIPTION OF SYMBOLS 11 Pipe-shaped case 13 Upstream side small diameter part 14 Intermediate | middle enlarged diameter part 15 Downstream side small diameter part 15A Corner circular arc surface 20 Rectification filter 21 Ring guide 21A, 24A Bolt insertion hole 21B Spacer protrusion 22 Annular gap 23 Cylindrical part 24 Center member 25 End taper guide 26 Mesh 30 Rectifier

Claims (7)

A pipe-type case connected in the middle of a pipe that allows fluid to flow in one direction;
An intermediate enlarged portion formed by expanding the inner diameter of the intermediate portion in the axial direction of the pipe-shaped case and an upstream small diameter portion on the upstream side thereof;
A rectifying filter housed in the intermediate enlarged portion,
The rectifying filter includes a cylindrical portion formed by laminating a plurality of annular ring guides surrounding the central axis of the pipe-shaped case with an annular gap, and one end opening of the cylindrical portion is opposite to the upstream small-diameter portion. A cup structure having a center member that covers from the downstream end of the upstream small-diameter portion, the opening end of the cylindrical portion is connected to the downstream end of the upstream small-diameter portion, and projects from the center member to the opposite side of the upstream small-diameter portion. A rectifier equipped with a tapered end guide that gradually decreases in diameter.   The rectifier according to claim 1, wherein the distal taper guide has a taper gradient on a distal end side that is smaller than a proximal end side from an intermediate position in an axial direction thereof.   The pipe-shaped case is provided with a downstream small diameter portion having a stepped diameter reduced from the downstream end portion of the intermediate enlarged diameter portion, and the downstream small diameter portion projects into the distal end portion of the end tapered guide. The rectifier according to claim 1 or 2.   The rectifier according to any one of claims 1 to 3, wherein each of the ring guides has a tapered shape whose diameter is increased in a direction away from the upstream small diameter portion.   The center member and the plurality of ring guides are formed with bolt insertion holes through which a common bolt penetrates, and the ring guide or the center adjacent to the surface of the plurality of ring guides on the center member side is formed. The rectifier according to any one of claims 1 to 4, further comprising a spacer protrusion for forming the annular gap with a member.   The rectifier according to any one of claims 1 to 5, wherein a mesh that covers the cylindrical portion from the outside or the inside is provided.   The pipe-shaped case is provided with a downstream small-diameter portion having a stepped diameter reduced from a downstream end of the intermediate large-diameter portion, and a step surface between the intermediate large-diameter portion and the downstream small-diameter portion. The rectifier according to any one of claims 1 to 4, wherein a corner arc surface that is continuous with the step surface and the inner peripheral surface is provided at a corner of the downstream small-diameter portion with the inner peripheral surface.