JPH0893694A - Diffuser for centrifugal compressor and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Object] To provide a diffuser capable of forming a flow path or passage into a desired shape without being restricted by a processing technique. A diffuser D provided around an impeller I of a centrifugal compressor, wherein a flow passage or passage 3 of the diffuser D has a large number of first groove portions 12 communicating from an inner circumference 1a to an outer circumference 1b. By joining the formed first wall surface member 1 and the second wall surface member 2 in which a large number of second groove portions 22 corresponding to the groove portions 12 are formed so that the groove portions 12 and 22 face each other. It is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffuser for a centrifugal compressor and a manufacturing method thereof. More specifically, the present invention relates to improvements in the structure of a passage diffuser and its manufacturing method.

[0002]

2. Description of the Related Art Conventionally, in a centrifugal compressor, in order to convert the dynamic pressure obtained by an impeller (impeller) into static pressure, a diffuser is provided surrounding the impeller (impeller). As a kind of this diffuser, a so-called passage diffuser in which a flow passage or passage is formed by a vane is used. However, in this passage diffuser, since the conversion rate from the dynamic pressure to the static pressure depends on the shape of the flow passage or the passage, flow passages having various shapes have been conventionally proposed. For example, U.S. Pat. No. 2,967,013 discloses vane tips (leading edges).
Is close to the impeller on the wall surface side, and is formed by retreating at the central portion between the wall surfaces, that is, the angle of the tip of the vane is made to recede in the circumferential direction on the wall surface side, and vertical at the central portion between the wall surfaces. ,
It is proposed to match the angular distribution of the flow ejected from the impeller.

Further, Japanese Patent Laid-Open No. 60-145499 discloses a diffuser of a centrifugal compressor having an impeller,
An annular housing and a plurality of passages spaced along the circumference of the housing and extending through the housing, adjacent passages intersecting each other at their radially inner inlet portions of the vane. A diffuser annular inlet in conformity with the absence of a diffuser, each passage further having a throat integral with said inlet portion, said throat having two substantially parallel opposing linear side walls and two opposing generally arcuate sides. A diffuser having a first quadrilateral cross section including sidewalls is disclosed. Then, in the same publication, an electric discharge machining method is proposed as a method of forming a passage having such a shape, and
An electric discharge machining electrode suitable for the machining is disclosed (see the publication, FIG. 7).

Alternatively, Japanese Patent Publication No. 59-12880 discloses an outlet diffuser for a centrifugal compressor in which a large number of segments are provided between two parallel plane disks and a flow path is formed between these adjacent segments. And forming both ends of each segment between the flat discs with a groove having an arc-shaped cross section to form a substantially cylindrical flow path between two adjacent segments, and dividing both end faces of each segment into segments. At the inner longitudinal ends of the arcuate ends to merge to form an arcuate end, the central main portion of the arcuate end being pointed, and the planar disc of each segment at a location corresponding to the central main portion. The two parallel flat sides contacting with each other are formed wider than the thickness of the central main part, and are formed so as to be smoothly continuous with the surface of the protrusion corresponding to the leg of the arched end. The outlet diffuser for a centrifugal compressor, wherein a projecting portion of the planar side in contact with the planar disk segment longitudinal tip were each rounded has been proposed.

Here, it is conceivable to make use of the advantages of the diffuser related to the conventional proposals and further improve the performance of the diffuser.

[0006] For example, from the diffuser inlet to the throat, as in the above-mentioned US Pat. No. 2967013,
By moving the vane tip (front edge) close to the impeller on the wall side and retracting it from the center of the wall and the wall, the angle of the vane tip can be made to circulate in the circumferential direction on the wall side, and at the center of the wall and the wall. At the diffuser inlet by matching the angular distribution of the flow ejected from the impeller, that is, by matching the angular distribution of the vane tip (leading edge) with the flow ejected from the impeller. By improving the flow, and in addition, by making the corner (corner) of the transverse section of the passage to the throat a radius R of a predetermined radius, it is difficult to flow in the corner and eliminate the part where a boundary layer is easily formed, Then, after the throat portion, the side surface side and the wall surface side are widened toward the end, that is, a three-dimensionally enlarged rectangular cross section is provided to obtain an optimal area change along the passage. Again, the corners of the rectangular cross section are rounded with a predetermined radius to eliminate the difficult-to-flow corners, and the static pressure recovery force has been significantly improved by efficiently decelerating along the passage to obtain static pressure recovery. The diffuser can be designed.

However, when a passage or a flow path having such a complicated shape is formed by using, for example, electric discharge machining which has been conventionally used for machining this diffuser,
As shown in FIG. 7 of JP-A-60-145499, there is a problem that the shape of the electric discharge machining electrode becomes complicated and the manufacturing time becomes long. Along with that, there is a problem that the manufacturing cost also increases. further,
Depending on the shape of the flow path or the passage, there is also a problem that machining cannot be performed because existing machining techniques such as electric discharge machining cannot be applied. Therefore, there is also a problem in that the flow path shape cannot be optimized when designing the diffuser, that is, the design of the diffuser is restricted by the processing technology.

The diffuser according to the proposal of Japanese Patent Publication No. 59-12880 is a centrifugal compressor in which a large number of segments are provided between two parallel plane disks and a flow path is formed between these adjacent segments. An outlet diffuser for use in a segment, in which both ends between flat discs of each segment are formed in a groove shape having an arcuate cross section, and a substantially cylindrical flow path is formed between two adjacent segments. There is no problem in processing, but there is a problem that it is difficult to make the optimum cross-sectional shape.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and is a diffuser capable of forming a flow path or passage into a desired shape without being restricted by a processing technique. It is also an object to provide a structure, and also to provide a manufacturing method suitable for the structure.

[0010]

A diffuser according to the present invention is a diffuser provided around an impeller of a centrifugal compressor, wherein a plurality of passages or passages of the diffuser extend from the inner circumference to the outer circumference. First groove formed
It is characterized in that it is formed by joining a wall surface member and a second wall surface member having a large number of groove portions corresponding to the groove portions so that the groove portions are opposed to each other.

In the diffuser of the present invention, the cross section in the transverse direction of the flow passage or passage is formed with a radius of a predetermined radius at the corner up to the throat portion, and between two adjacent flow passages or passages. It is preferable that the tip of the vane left uncut is close to the impeller on the wall surface side and recedes from this at the central portion of the wall surface and the side surface of the flow passage or passage. It is also preferable that the directional cross section is a rectangle in which the throat portion and the subsequent portions are three-dimensionally enlarged, and the corners thereof are formed with a radius having a predetermined radius.

On the other hand, the method for manufacturing a diffuser of the present invention is a method for manufacturing a diffuser which is provided so as to surround an impeller of a centrifugal compressor, in which a large number of grooves extending from the inner circumference to the outer circumference of the first wall member. And a step of forming a large number of groove portions corresponding to the groove portions on the second wall member, and a step of joining the first wall member and the second wall member with the groove portions facing each other. It is characterized by including.

In the method for manufacturing a diffuser according to the present invention, the groove is formed with a radius of a predetermined radius in a corner portion of the groove portion up to a position corresponding to the throat portion, and the adjacent two are formed.
It is preferable that the tip of the vane left uncut between the two groove portions is close to the impeller near the wall surface, and that a step of forming at the joining surface is set back from this is formed.
With respect to the groove portion, a procedure is added in which a lateral cross section of the flow path or the passage is a three-dimensionally enlarged rectangle after the position corresponding to the throat portion, and a corner having a predetermined radius is formed at the corner portion. It is preferable that

[0014]

A large number of grooves having a desired shape are formed on the first wall member disposed on the outer periphery of the shroud, and then the second wall member is formed on the first wall member so as to be opposed to and joined to the first wall member. A large number of groove portions corresponding to the groove portions are formed, and then the first wall surface member and the second wall surface member are joined together with the surfaces on which the groove portions are formed facing each other to form a diffuser. As described above, according to the present invention, the groove member having a large number of desired shapes is formed in the wall surface member, and thereafter, the wall member is joined to form the diffuser having the flow path or the passage. And can be formed into a flow path or passage having a desired shape. Therefore, the dynamic pressure in the diffuser is converted to static pressure with high efficiency. In addition, since the diffuser flow passages or passages are formed by joining the flat plates with grooves formed on each other, the flow passages or passages can be designed without any restrictions in processing. Or the degree of freedom in the passage design is increased.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the accompanying drawings, but the present invention is not limited to such embodiments.

Embodiment 1 An axial sectional view of a diffuser according to Embodiment 1 of the present invention is shown in FIG. 1 and FIG. 2, in which the diffuser D of the present invention is provided on the rear side of a two-stage centrifugal compressor. It is applied and accelerated by an impeller on the front stage side (not shown) to increase velocity energy, is decelerated by a diffuser on the front stage side (not shown), then passes through a return channel C (partially shown), and again on the rear stage blade. The air that is sucked into the vehicle I and accelerated is converted into static pressure. The diffuser D includes a ring-shaped first wall member 1 arranged on the outer periphery of the shroud S and a joint surface 2 between the first wall member 1 and the ring-shaped first wall member 1.
And the second wall surface member 2 having No. 1 as a main part. In addition, in the first embodiment, the joint surface 11 and the joint surface 21 are located at left-right symmetrical positions (central portions).

As shown in FIG. 3, a large number of inner peripheries 1a are provided on the side of the surface 11 of the first wall member 1 that joins with the second wall member 2.
To the outer periphery 1b from the groove portion (first groove portion) 12 having a desired shape
Are provided at a predetermined angle with respect to the radial direction of the diffuser D. Further, a second groove portion 22 corresponding to the first groove portion 12 is formed on the joint surface 21 side of the second wall member 2 with the first wall member 1. The first groove portion 12 and the second groove portion 22 cooperate with each other to form the flow path or the passage 3 of the diffuser D when the first wall surface member 1 and the second wall surface member 2 are joined. In addition, in FIG. 3, in order to facilitate understanding of the drawing, corresponding elements of the second wall surface member 2 are indicated by reference numerals with parentheses, and the vane 5 is provided with a horizontal line,
The area of R is clearly indicated by the contour line. The arrow A in FIG. 3 indicates the direction of rotation of the impeller I.

The cross section of the flow path or passage 3 in the lateral direction is basically rectangular up to the throat portion 4, and a radius R having a predetermined radius is formed at a corner (corner) of the throat and the adjoining two. The tip (front edge) 5a of the vane 5 left uncut between the two flow paths or passages 3 is close to the impeller I on the wall surface side, and the central portion between the wall surfaces (joint surfaces 11 and 21).
It is formed by retreating from this (see FIG. 4), which improves the flow at the diffuser inlet. The radius of the radius R and the tip of the vane 5
The angle formed by both sides of a, the so-called wedge angle (2δ in FIG. 3)
Is selected appropriately, the leading edge 5a can have a desired shape, that is, an optimum shape for the angular distribution of the flow of the air ejected from the impeller I. As a result, the flow at the inlet of the diffuser D can be improved and the efficiency of the diffuser D can be improved.

Further, the cross section in the lateral direction after the throat portion 4 is
Both the wall surface and the side surface are widened toward the end, that is, three-dimensionally expanded rectangles, and the corners (corners) thereof are formed with a radius R having a predetermined radius (see FIG. 5). This makes it possible to optimize the cross section of the flow passage or the passage 3, efficiently reduce the speed along the flow passage or the passage 3, improve the flow in the corners, and efficiently convert the dynamic pressure into the static pressure.

The formation of the first groove portion 12 for forming the flow path or the passage 3 is performed as follows, for example.

The shape data, array angle, array pitch, etc. of the first groove portions 12 are input to the numerically controlled machine tool.

The joint surface 11 of the first wall member 1 is set as a surface to be machined in the numerically controlled machine tool.

A surface to be machined is cut or ground by a numerically controlled machine tool based on input data to form a large number of first groove portions 12 in a desired shape on the joint surface 11 side of the first wall member 1 at predetermined intervals. Here, in order to secure the positional accuracy of the groove to be formed, a reference reamer hole (not clearly shown in the first embodiment, three reamer holes are formed on the same circumference in the joining surface 11). (Formed) 61 is drilled, and grooving is performed using this reamer hole 61 as a reference. In addition, the through holes 81 and 91 for inserting the bolts and the through holes 71 in which the female screw to be screwed into the bolt 73 inserted from the second wall surface member 2 side is formed.
Are formed in a predetermined position at a predetermined number.

Next, the first wall surface member 1 of the second wall surface member 2
Similarly, the reamer holes 62 are formed on the side of the joint surface 21 with and the second groove portions 22 are formed in a desired shape at predetermined intervals with reference to this. In addition, a through hole 82 formed with a female screw that is screwed into the bolt 83 inserted through the through hole 81, a through hole 92 corresponding to the through hole 91, and a bolt corresponding to the through hole 71 formed with the female screw. A through hole 72 for insertion is formed.

Then, the joint surface 2 of the second wall member 2
After a knock pin (not shown) is press-fitted into the reamer holes 62, 62, 62 of No. 1, the joint surface 11 of the first wall member 1 is made to face and the portion protruding from the joint surface 21 of the second wall member 2 of the knock pin is removed. Reamed holes 61, 6 of the first wall member 1
The first wall surface member 1 and the second wall surface member 2 are positioned by fitting them to Nos. 1 and 61, and then the bolt 73 is inserted through the through hole 72 provided in the second wall member 2, The bolt 73 is screwed into the through hole 71 in which the internal thread is formed in the first wall member 1 corresponding to 72, and the bolt 83 is inserted through the through hole 81 provided in the first wall member 1. Then, the bolts 83 are screwed into the through holes 82, which are formed in the second wall surface member 2 so as to correspond to the through holes 81, and in which the internal threads are formed, so that the first wall surface member 1 and the second wall surface member. Combine 2 to complete diffuser D. After that, the diffuser D is set at a predetermined position of the housing H of the centrifugal compressor by bolting with a bolt 93 inserted through the through holes 92 and 91.

As described above, according to the first embodiment, the first groove portion 12 serving as the flow path or passage 3 of the diffuser D is formed in the first wall member 1 and the second wall member 2 by cutting or grinding.
The diffuser D having the flow path or the passage 3 having a desired shape can be manufactured by a simple operation of forming the second groove portion 22 and the second groove portion 22, and then bolting the both.

Next, Example 1 produced in this way
The static pressure recovery rate (the ratio of the dynamic pressure at the impeller outlet converted to static pressure by the diffuser) C _P and the compressor adiabatic efficiency η _ts when using the diffuser D are measured, and the measurement results are shown in FIG. 6 (a) and FIG. 6 (b) are shown by solid lines. For comparison, the conventional passage diffuser (see FIG.
To FIG. 9), the static pressure recovery rate C _P and the adiabatic efficiency η _{ts of the} compressor are measured, and the measurement results are also shown by dotted lines in FIGS. 6A and 6B. It can be seen from FIG. 6 that the diffuser D of the first embodiment has a markedly higher diffuser static pressure recovery rate C _{P at} the design flow point of the compressor than the conventional passage diffuser. 7. FIG. 7 is a sectional view of a main part of a conventional passage diffuser used for measuring the static pressure recovery rate and the compressor efficiency, and FIG.
FIG. 8 is a sectional view taken along the line VIII and corresponds to FIG. 4, showing the front edge shape, and FIG. 9 is a sectional view taken along the line IX-IX in FIG. 7, corresponding to the throat section in FIG. A throat cross section is shown.

As described above, in the first embodiment, the diffuser has its inlet shape adapted to the flow distribution of the jet flow ejected from the impeller at the design flow rate, and the subsequent passage shape is also optimum for the design flow rate. Therefore, it is possible to improve the diffuser static pressure recovery rate at the design flow point and improve the compressor adiabatic efficiency.

Embodiment 2 A diffuser according to Embodiment 2 of the present invention is shown in FIGS. 10 and 11. The second embodiment is a modification of the first embodiment. In the first embodiment, the radius of the radius R, which is the same on the first wall surface member 1 side and the second wall surface member 2 side, is set to the first wall surface member 1 side. The side is enlarged and the position of the joint surface is moved from the left-right symmetrical position to the second wall member 2 side. With this configuration, the angular distribution of the tip (front edge) of the vane 5 of the diffuser D can be further matched with the angular distribution of the flow ejected from the impeller I, and the static pressure recovery rate of the diffuser D can be further improved. Can be improved.

The remaining structure of the second embodiment is the same as that of the first embodiment.
The detailed description of the configuration is omitted.

Although the present invention has been described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made. In the present embodiment, the cross section after the throat portion is a rectangle with rounded corners having a predetermined radius, but the cross section may be an ellipse or a modified ellipse having parallel portions at the upper and lower portions. .

[0032]

As described above in detail, in the present invention, the first wall surface member having the first groove portion and the second wall surface member having the second groove portion which cooperate to form the flow path or the passage are joined. Since the diffuser is formed by the above, there is an excellent effect that the flow passage or the passage having the desired shape can be formed in the diffuser without being restricted by the work in producing the passage or the passage. Therefore, a diffuser having an optimum flow path or passage shape can be obtained, so that the dynamic pressure generated by the impeller can be converted into static pressure with high efficiency, and the excellent effect of improving the heat insulation efficiency of the compressor can be obtained. To be In addition, since the flow path or passage is formed by joining flat plates with grooves formed, it is not necessary to consider working restrictions when designing the flow path or passage, and the degree of freedom in design is greatly improved. It also has the effect of increasing.

[Brief description of drawings]

FIG. 1 is an axial sectional view of a main part of a centrifugal compressor to which a diffuser according to a first embodiment of the present invention is applied.

FIG. 2 is an enlarged sectional view of the diffuser shown in FIG.

3 is a sectional view taken along line III-III in FIG.

4 is a sectional view taken along line IV-IV in FIG.

5 is a sectional view taken along line VV of FIG.

FIG. 6 shows the static pressure recovery rate and compressor adiabatic efficiency of the example,
It is a graph shown in comparison with that of the conventional passage diffuser, where (a) shows the static pressure recovery rate and (b) shows the adiabatic efficiency of the compressor.

FIG. 7 is a sectional view of a main part of a conventional passage diffuser used for measuring a static pressure recovery rate and a compressor adiabatic efficiency.

8 is a sectional view taken along line VIII-VIII of FIG. 7, corresponding to FIG. 4 and showing a leading edge shape.

9 is a sectional view taken along the line IX-IX in FIG. 7, which corresponds to the throat section in FIG. 5 and shows the throat section.

FIG. 10 is a diagram corresponding to FIG. 2 in Example 1 of Example 2 of the present invention.

FIG. 11 is a diagram corresponding to FIG. 4 in the first embodiment of the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st wall surface member 11 Joining surface 12 1st groove part 2 2nd wall surface member 21 Joining surface 22 2nd groove part 3 Flow path, passage 4 Throat part 5 Vane 61, 62 Reamer hole 71 Female threaded through hole 72 Transparent Hole 73 Bolt 81 Through hole 82 Female thread formed through hole 83 Bolt 91,92 Through hole 93 Bolt R Earl D Diffuser S Shroud H Housing I Impeller, Impeller C Return channel

Claims (6)

[Claims] 1. A diffuser provided around an impeller of a centrifugal compressor, wherein a flow passage or passage of the diffuser is formed with a large number of groove portions communicating from an inner circumference to an outer circumference. And a second wall surface member in which a large number of groove portions corresponding to the groove portions are formed, and the groove portions are opposed to each other and are joined together. 2. The lateral cross section of the flow passage or passage is formed by rounding a radius of a predetermined radius at the corner up to the throat portion and leaving uncut between two adjacent flow passages or passages. The diffuser according to claim 1, wherein the tip of the vane is formed closer to the impeller on the wall surface side and retracted from the wall surface at a central portion between the wall surfaces. 3. The cross section in the lateral direction of the flow passage or the passage is formed into a three-dimensionally enlarged rectangle after the throat portion, and is formed with rounded corners having a predetermined radius. Item 2. The diffuser according to item 2. 4. A method of manufacturing a diffuser surrounding an impeller of a centrifugal compressor, comprising the steps of forming a large number of groove portions communicating from the inner periphery to the outer periphery on a first wall member.
And a step of forming a large number of groove portions corresponding to the groove portions on the second wall surface member, and a step of joining the first wall surface member and the second wall surface member with the groove portions facing each other. A method for manufacturing a diffuser. 5. A radius of a predetermined radius is formed in a corner of the groove up to a position corresponding to a throat, and
The vane tip, which is left uncut between two adjacent groove portions, is close to the impeller on the wall surface side, and a step of forming the vane by retracting from the joining surface is added. 4. The method for manufacturing the diffuser according to 4. 6. A procedure of forming a lateral cross section of a flow path or a passage in the groove portion in a rectangular shape three-dimensionally expanded from a position corresponding to a throat portion and forming a radius of a predetermined radius in a corner portion thereof. 6. The method for manufacturing a diffuser according to claim 5, further comprising: