JP4795912B2 - Variable diffuser and compressor - Google Patents

Description

  The present invention relates to a variable diffuser applied to, for example, a centrifugal compressor, a mixed flow compressor, and the like, and a compressor provided with the variable diffuser.

Conventionally, for example, a centrifugal compressor such as a turbocharger used for an internal combustion engine for automobiles is known.
FIG. 17 is a cross-sectional view showing a main part of a conventional centrifugal compressor. The illustrated centrifugal compressor 10 compresses a fluid such as gas or air introduced from the outside of the housing 11 by rotating an impeller 13 having a large number of blades 12 in the housing 11. The fluid flow (airflow) formed in this way is sent to the outside through an impeller outlet (hereinafter also referred to as “diffuser inlet”) 14, a diffuser 15, and a scroll (not shown), which are the outer peripheral ends of the impeller 13. In addition, the code | symbol 16 in a figure is an axial centerline with which the impeller 13 rotates.

The diffuser 15 described above is an airflow passage provided between the impeller outlet 14 and the scroll, and has a function of recovering the dynamic pressure to a static pressure by decelerating the airflow discharged from the impeller outlet 14. Yes. The diffuser 15 is usually formed of a pair of opposed wall surfaces. In the following description, one of the pair of opposed wall surfaces is called a shroud side wall surface 17 and the other is called a hub side wall surface 18.
The diffuser 15 described above includes, for example, a vane diffuser having a diffuser blade (hereinafter referred to as “vane”) 19 as shown in FIG. 18 and a vaneless diffuser without the vane 19.

A general centrifugal compressor provided with a vane diffuser employs a fixed vane diffuser in which a vane 19 is stationary. However, when the flow range of the centrifugal compressor needs to be expanded, the vane 19 can be moved to change the blade leading edge angle βk (hereinafter referred to as “blade angle βk”) shown in FIG. A variable diffuser is used.
For example, as shown in FIG. 18, the variable diffuser has a general structure in which a vane 19 is provided with a pivot shaft 20 to be supported by the shroud side wall surface 17 and the hub side wall surface 18, and the vane 19 is centered on the pivot shaft 20. The blade angle βk is changed by rotating.

For such a variable diffuser, a drive device has been proposed in which the angles of a plurality of diffuser blades are variable with a simple structure. This drive device includes a large gear rotated by an actuator or the like and a plurality of gears meshed with the large gear, and changes the angle by rotating the diffuser blade connected to each gear. (For example, see Patent Document 1)
Furthermore, in a centrifugal compressor provided with a vaned diffuser, it has been proposed to provide a rotatable second stationary blade for the purpose of expanding the operation on the small flow rate side. (For example, see Patent Documents 2 and 3)
Japanese Patent Laid-Open No. 7-310697 Japanese Patent No. 2865834 Japanese Patent No. 3513729

  By the way, about the vane 19 of a variable diffuser, when designing a vane blade shape, it sets to the shape which becomes an intermediate | middle within a desired flow volume change range. Therefore, in the conventional variable diffuser in which the vane 19 is rotated about the pivot shaft 20 and the blade angle βk is variable, the characteristic change as shown in FIG. 19 occurs. That is, the flow rate range defined by the surge flow rate Qs and the choke flow rate Qc is such that the vane 19 is rotated within the rotation range θ from the maximum blade angle βmax to the minimum blade angle βmin, as shown in FIG. As a result, the fluctuation corresponding to each of the surge flow rate Qs and the choke flow rate Qc greatly increases.

However, when the above-described flow rate range (the range in which the flow rate can be changed) is set to be greatly widened, as shown in FIG. 21, the flow angle β and the blade angle βk of the vane 19 change with different inclinations. For this reason, since the incidence (In) increases in the small flow rate region and the large flow rate region, there is a problem that the efficiency decreases due to an increase in loss. The incidence is a value defined by the difference between the blade leading edge angle βk and the flow angle β.
Further, the rotation type variable diffuser structure allows the vane 19 to rotate smoothly, so that a gap δ is formed between both side ends of the vane 19 and the shroud side wall surface 17 and the hub side wall surface 18 (see FIG. 18). Is provided. For this reason, since the leakage of the airflow flowing through the gap δ occurs, there is a problem that the efficiency is lowered over the entire flow rate range.

As described above, the conventional variable diffuser has a problem that the efficiency decreases due to the increase in the incidence or the leakage from the gap δ. Therefore, the efficiency can be further improved by solving this problem. desired.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a variable diffuser capable of further improving efficiency and a compressor including the variable diffuser.

In order to solve the above problems, the present invention employs the following means.
In the variable diffuser according to the present invention, a diffuser passage is formed between the hub side wall surface and the shroud side wall surface that decelerates the airflow discharged from the outer peripheral end of the impeller rotating in the housing and restores the dynamic pressure to static pressure. In the variable diffuser in which diffuser blades are provided in the diffuser passage, the diffuser blades are alternately fixed in the circumferential direction to the wall surface members forming the hub side wall surface and the shroud side wall surface, and any of the wall surface members A driving means for rotating either one of them coaxially with the rotation of the impeller is provided.

According to such a variable diffuser, the diffuser blades are alternately fixed to the wall surface member forming the hub side wall surface and the shroud side wall surface in the circumferential direction, and one of the wall surface members is rotated coaxially with the rotation of the impeller. Since the driving means is provided, the throat area can be changed without changing the blade leading edge angle by rotating the wall member on the movable side. Further, the gap δ formed between the diffuser blade, the hub side wall surface, and the shroud side wall surface is reduced because it is only one of the surfaces.
In this case, it is preferable that the movable range of the wall surface member rotated by the driving means is set so as to cover the entire width between adjacent diffuser blades fixed to the fixed wall surface member.

  In the above invention, the inlet radius (R1) of the diffuser blade provided on the rotating side of the wall member is set larger than the inlet radius (R2) of the diffuser blade provided on the fixed side of the wall member (R1> R2). Preferably, this can prevent the leading edge thickness of the overlapping wings from increasing.

  In the above invention, the blade leading edge angle (αk1) of the diffuser blade provided on the rotating side of the wall member is the blade leading edge angle (αk2) of the diffuser blade provided on the fixed side of the wall member at the same radial position. It is preferable to set a smaller value (αk1 <αk2), whereby an average blade leading edge angle in a state where two blades overlap each other can be reduced.

  In the above invention, the blade leading edge angle (αk1) of the diffuser blade provided on the rotating side of the wall member is the blade leading edge angle (αk2) of the diffuser blade provided on the fixed side of the wall member at the same radial position. It is preferable to set a larger value (αk1> αk2), whereby an average blade leading edge angle in a state where two blades overlap each other can be increased.

In the above invention, the diffuser blade provided on the fixed side of the wall member is preferably a small chord specific blade, thereby improving characteristics at a small flow rate while maintaining the characteristics of the small chord specific blade. it can.
In this case, the trailing edge radius (R3) of the diffuser blade provided on the rotating side of the wall member is set larger than the trailing edge radius (R4) of the diffuser blade provided on the fixed side of the wall member (R3> R4). It is preferable that a wide flow range and a high pressure ratio can be achieved at the same time.

In the above invention, the setting of the fixed side and the rotating side may be reversed.
That is, the inlet radius (R2) of the diffuser blade provided on the fixed side of the wall surface member may be set larger (R2> R1) than the inlet radius (R1) of the diffuser blade provided on the rotating side of the wall surface member.
Further, the blade leading edge angle (αk2) of the diffuser blade provided on the fixed side of the wall surface member is smaller than the blade leading edge angle (αk1) of the diffuser blade provided on the rotating side of the wall surface member at the same radial position (αk2 < αk1) may be set.
Further, the diffuser blade provided on the rotating side of the wall surface member may be a small chord joint specific blade.
Further, even if the trailing edge radius (R4) of the diffuser blade provided on the fixed side of the wall member is set larger than the trailing edge radius (R3) of the diffuser blade provided on the rotating side of the wall member (R4> R3). Good.

  In the above invention, the drive means may include a sliding mechanism portion in which the rotating side of the wall surface member reciprocates between a gap forming position and a gap reducing position with respect to the fixed side of the wall surface member. Preferably, this makes it possible to improve efficiency by minimizing the gap δ.

  The compressor which concerns on this invention is equipped with the variable diffuser in any one of Claim 1-9 in the outer peripheral end of the impeller which rotates within a housing, It is characterized by the above-mentioned.

  According to such a compressor, it becomes a compressor provided with the variable diffuser which can eliminate the decrease in efficiency due to an increase in the incidence and leakage from the gap δ, and can further improve the efficiency.

According to the above-described present invention, since the throat area can be changed without changing the blade leading edge angle on the movable side, it is possible to eliminate the decrease in efficiency due to the increase in the incidence, and therefore the efficiency is further improved. Thus, a variable diffuser and a compressor including the variable diffuser can be provided.
In addition, since the gap δ formed between the diffuser blade, the hub side wall surface, and the shroud side wall surface is reduced to only one of the surfaces, it is possible to eliminate the decrease in efficiency due to leakage from the gap δ. Become.

Hereinafter, an embodiment of a variable diffuser and a compressor according to the present invention will be described with reference to the drawings.
<First Embodiment>
The variable diffuser 30 shown in FIG. 1 restores the dynamic pressure of the airflow to a static pressure by decelerating the airflow discharged from the outer peripheral end of an impeller that rotates in a housing such as a centrifugal compressor or a mixed flow compressor. Is. The variable diffuser 30 has a diffuser passage 33 formed between the shroud side wall surface 31a and the hub side wall surface 32a facing each other, and a movable diffuser blade (hereinafter referred to as a “movable blade”) 34 and the diffuser passage 33. A fixed diffuser blade (hereinafter referred to as “fixed blade”) 35 is provided.
Although the movable blades 34 are provided on the shroud side wall surface 31a to be movable here, the movable blades 34 may be provided on the hub side wall surface 32a to be movable.

The configuration of the movable diffuser 30 will be specifically described. The movable blade 34 is fixed to a movable disk (wall surface member) 31 that forms a shroud side wall surface 31a, and the fixed blade 35 is a fixed disk (that forms a hub side wall surface 32a). (Wall member) 32 is fixed. The movable blade 34 and the fixed blade 35 have the same blade shape, and the same number of blades (blade number N) are arranged at a predetermined pitch in the circumferential direction with respect to the shroud side wall surface 31a and the hub side wall surface 32a.
FIG. 1A shows a state where a pair of opposed movable disks 31 and fixed disks 32 are separated. From this state, the movable disk 31 and the fixed disk 32 are arranged such that the movable blades 34 of the shroud side wall surface 31a and the fixed blades 35 of the hub side wall surface 32a are alternately arranged at equal pitches in the circumferential direction at a predetermined reference position. As shown, it is integrated by sliding in a combination direction indicated by an arrow in the figure. That is, in the assembled state in which the movable disk 31 and the fixed disk 32 are integrated, the movable blades 31 and the fixed blades 32 are alternately arranged at equal pitches in the circumferential direction at a predetermined reference position. The cross-sectional view of FIG. 1B shows the AA cross section of FIG. 1A with respect to the diffuser passage 33 formed by integrating the movable disc 31 and the fixed disc 32.

  On the movable disk 31 side, there is a drive device 40 for rotating the movable disk 31 in a predetermined rotation range θ in a rotation direction coaxial with the rotation of the impeller (indicated by a white arrow in the figure). Is provided. The drive device 40 is configured by, for example, a gear drive unit 41 provided at the upper end portion of the movable disk 31 and a sliding mechanism portion 45 provided at the lower end portion. In this case, the rotation range θ is substantially different from the pitch in which the movable blade 31 and the fixed blade 32 are alternately arranged in the circumferential direction at the predetermined reference position described above, although a difference corresponding to the thickness of the blade occurs. About twice as much. In other words, the movable range θ is the full width between adjacent blades of the fixed blade 35.

The gear drive unit 41 has a configuration in which a rack gear unit 42 formed on the upper end surface of the movable disk 31 and a pinion gear 43 are engaged with each other. The pinion gear 43 is connected to a drive source such as an electric motor (not shown) and can be rotated in a desired direction as necessary.
The sliding mechanism 45 is a portion where the movable disk 31 is connected to the housing 11 so as to be slidable in the circumferential direction. In the illustrated example, the convex guide rail 46 formed on the housing 11 and the concave groove portion 47 formed on the lower end surface of the movable disk 31 are fitted, and the movable disk 31 slides along the guide rail 46. Is configured to do. Such a sliding mechanism 45 prevents the high-pressure airflow that has recovered static pressure at the outlet of the diffuser passage 33 from leaking from the back surface of the movable disc 31 to the inlet side of the diffuser passage 33. A leakage prevention measure (not shown) is provided between the groove portion 47 and the concave groove portion 47.

  As a result, the movable disk 31 is guided to the sliding mechanism section 45 by rotating the pinion gear 43 of the gear drive section 41 and rotates coaxially with the rotation shaft of the impeller. It moves relative to 32. Then, the movable blade 34 integrated with the movable disk 31 moves from the reference position to both sides in the circumferential direction within the movable range θ. That is, the movable blades 34 move toward the fixed blades 35 on both sides by rotating from the reference positions arranged at an equal pitch, and as shown by the imaginary lines in FIG. Without changing the blade angle from the position where the pressure surface of the movable blade 34 contacts the pressure surface of the adjacent fixed blade 35 to the position where the negative pressure surface of the movable blade 34 overlaps the pressure surface of the adjacent fixed blade 35, It can be rotated within the movable range θ.

The movable range θ of the movable blade 34 will be described more specifically with reference to FIG.
FIG. 2A shows a case where the movable blade 34 is at the reference position. In this state, the same number (N) of movable blades 34 and fixed blades 35 having the same blade shape are arranged at equal pitches in the circumferential direction. In this state, the throats A11 and A12 formed between the blades of the movable blade 34 and the fixed blade 35 adjacent to both sides are equal. For this reason, the throat area of the variable diffuser 30 is a value obtained by multiplying the total number of throats (A11 + A12) formed on both sides of the movable blade 34 by the number N of movable blades 34.

FIG. 2B shows a state where the movable blade 34 is in contact with the pressure surface of the fixed blade 35. In this state, since the blades are in contact with each other, the throat A12 becomes substantially zero and the throat A11 becomes the maximum (A11max). Such a maximum throat is larger than the total throat value at the reference position described above (A11max
> A11 + A12), the throat area increases to about 1.2 to 1.3 times. In the following description, the state where the throat area is maximized is referred to as the throat maximum position.
Even when the movable blade 34 rotates in the opposite direction from the reference position, the same result is obtained because both blades are in contact with each other.

  FIG. 2 (c) shows a case where the movable blade 34 is at an intermediate position between FIG. 2 (a) and FIG. 2 (b). The throat area in this state is a substantially intermediate value between the reference position and the maximum throat position. Therefore, the throat area can be appropriately changed within the range of about 1.2 to 1.3 times the reference value by rotating the movable blade 34 within the movable range θ.

In the variable diffuser 30 having the above-described configuration, the number of diffuser blades composed of the movable blade 34 and the fixed blade 35 is substantially doubled from N to 2N. That is, when N movable wings 34 are attached to the movable disc 31 and N fixed wings 35 are attached to the stationary disc 32, 2N pieces of the movable wing 34 and the fixed wing 35 are separated from each other. There are diffuser wings. However, in the state where the adjacent movable blade 34 and the fixed blade 35 are in contact with each other, the airflow substantially flows between the N diffuser blades.
As a result, the flow rate of the compressor characteristics changes due to the change in the throat area. That is, since the throat area increases about 1.2 to 1.3 times, the flow rate range can be expanded by changing the choke flow rate Qc shown in FIG. 19 by about 20 to 30%.

Further, since the blade leading edge angle (blade angle) β of the movable blade 34 as well as the fixed blade 35 is always constant, as compared with a conventional variable diffuser in which the blade angle β changes as the vane 19 rotates, FIG. As shown by the two-dot chain line, the change in the incidence is extremely small. Therefore, the compressor provided with the variable diffuser 30 can reduce the loss that increases as the incidence increases, so that the efficiency can be improved as compared with the conventional case.
Further, since one end of the movable blade 34 and the fixed blade 35 is fixed to the wall surface forming the diffuser passage 33, the gap δ is formed only on one side in the blade width direction. Therefore, the area of the gap δ can be halved as compared with the conventional structure in which the vane 19 is rotated, so that the loss due to airflow leakage can be halved and the efficiency can be improved.

<Second Embodiment>
Subsequently, a second embodiment of the present invention will be described with reference to FIG.
In the movable blade 34A of this embodiment, the entrance radius R1 is set larger than the entrance radius R2 of the fixed blade 35. That is, the entrance radius R1 of the movable blade 34A is such that the movable blade 34A has a throat A2 between the blades formed between the adjacent fixed blades 35 when the movable blade 34A is at an intermediate position between the adjacent fixed blades 35. The blade leading edge is set to be upstream. In the illustrated example, the throat area changes only in a range where the leading edge of the movable blade 34A is upstream of the throat A2 with respect to the intersection X between the throat A2 and the radius R1.

Hereinafter, it demonstrates concretely based on drawing.
As shown in FIG. 3A, when the movable wing 34A is positioned substantially at the center of the fixed wing 35, the throat area is minimized.
As shown in FIG. 3B, when the leading edge of the movable blade 34A is positioned upstream of the throat A2, the total value (A11 + A12) of the throat A11 and the throat A12 gradually increases.
As shown in FIG. 3C, when the leading edge of the movable blade 34A is located downstream of the throat A2, the throat area becomes a value obtained by multiplying the throat A2 by the number N of blades, and the throat even if the movable blade 34A is rotated. Reaches the maximum A2 and does not increase.

By the way, in the state of FIG. 2B described above, the blade tips of the movable blade 34 and the fixed blade 35 overlap each other with a finite interval, and the blade thickness of the leading edge of the diffuser blade is increased. Such an increase in blade thickness is not only an obstacle to maximizing the throat area, but also increases the loss of the blade leading edge.
However, in the state shown in FIG. 3C, the leading edge of the movable blade 34 </ b> A is located downstream of the leading edge of the fixed blade 35. Therefore, compared with the state shown in FIG. 2B, the size of the throat is A2> A11max. Thus, when the entrance radius R1 is set larger than the entrance radius R2 (R1> R2), the maximum value of the movable range of the throat area becomes large.
Further, in the state shown in FIG. 3C, the blade leading edge is substantially halved to the number of the fixed blades 35, so that the blade leading edge loss is reduced.

<Third Embodiment>
Subsequently, a third embodiment of the present invention will be described with reference to FIGS.
In the movable blade 34B of this embodiment, at the same radial position, the blade leading edge angle (blade angle) αk1 is set smaller than the blade angle αk2 of the fixed blade 35, and the movable blade 34B is moved from the middle of the fixed blade 35 to the fixed blade 35. Drive toward the negative pressure surface.
With such a configuration, the maximum value of the throat A12 is smaller than that of the throat A2, but when the two blades are overlapped, the average blade angle αk
Can be reduced.

As a result, as shown in FIG. 5, the characteristic of the compressor is that the flow angle α at the maximum angle is small, and the comparison between the solid line display and the broken line display shows that the performance when the flow rate is small is improved. . In addition, from the comparison between the solid line display and the dotted line display at the intermediate angle, it can be seen that the performance at a small flow rate where the flow angle α is small is improved although not as high as at the maximum angle.
In other words, setting the blade angle αk to αk1 <αk2 places importance on the performance at a small flow rate with a small flow angle α, and the performance improvement that improves the pressure ratio in the small flow rate region at the maximum angle and intermediate angle Is obtained.

<Fourth Embodiment>
Subsequently, a fourth embodiment of the present invention will be described with reference to FIGS.
In the movable blade 34C of this embodiment, at the same radial position, the blade leading edge angle (blade angle) αk1 is set larger than the blade angle αk2 of the fixed blade 35, and the movable blade 34C is moved from the middle of the fixed blade 35 to the fixed blade 35. Drive towards the pressure surface.
With such a configuration, as in the second embodiment described above, A2 is the maximum value for the throat. On the other hand, the choke flow rate Qc is larger than the pressure surface angle of the fixed vane 35 because the flow angle α at the diffuser inlet flows substantially perpendicular to the throat A2. For this reason, negative incidence is increased, loss is large, and a substantial choke flow rate is reduced.

However, in this embodiment, when the movable blade 34C and the fixed blade 35 are in contact with each other and the two blades are combined, the average blade angle αk can be increased.
As a result, as shown in FIG. 7, the performance of the compressor is improved by increasing the pressure ratio at a maximum flow rate when the flow angle α is large and the flow rate α is large, comparing the solid line display and the broken line display. I understand that. Further, from the comparison between the solid line display and the dotted line display at the intermediate angle, it can be seen that the performance at a large flow rate with a large flow angle α is improved, although not as high as at the maximum angle.
In other words, setting the blade angle αk to αk1> αk2 places importance on the performance at a large flow rate where the flow angle α is large, and the performance improvement that improves the pressure ratio in the large flow rate region at the maximum angle and intermediate angle Is obtained.

<Fifth Embodiment>
Next, a fifth embodiment of the present invention will be described with reference to FIGS.
In vane diffusers, those that do not have the shortest distance in the direction perpendicular to the blade suction surface between adjacent blades, in other words, those that cannot be throated, are called `` small string ratio diffusers '' and are generally recognized. ing. This small string ratio diffuser has the following characteristics.

The vaneless diffuser has a feature that the flow rate is wide but the efficiency is low because the surge flow rate Qs is small and the choke flow rate Qc is large.
On the other hand, the vane diffuser has a feature that the surge flow rate Qs is large and the choke flow rate Qc is only about 10 to 20% larger than the surge flow rate Qs, so that the flow rate is narrow but the efficiency is high.
On the other hand, since the chord ratio diffuser cannot throat, the choke flow rate Qc is larger than the vane diffuser and the surge flow rate Qs is larger than the vane diffuser. Therefore, the low chord ratio diffuser is characterized by higher efficiency than the vaneless diffuser. In the small chord ratio diffuser, the movable wing in which the throat is not formed is referred to as a “small chord ratio wing”.

FIG. 10 shows the relationship between the pressure recovery rate and the number of blades for the vaned diffuser and the low chord ratio diffuser as the characteristics of the diffuser.
When the number of blades is changed, the normal vaned diffuser has a rapid decrease in pressure recovery rate when the number of blades decreases from around 10 to the number of small blades, as shown by the solid line in the figure. Matches the vaneless diffuser.
On the other hand, the small chord ratio diffuser uses a blade whose size is smaller than that of a normal vane diffuser. Therefore, as shown by the alternate long and short dash line in the figure, even if the number of blades is increased, the normal vane diffuser is used. Until the pressure recovery rate does not increase.

Therefore, in the fifth embodiment, as shown in FIG. 8, the hypothetical throat A2 is set in the small chord joint ratio diffuser having the small chord joint ratio wings that have a sufficiently small number of the fixed wings 35 and cannot form the throat. Then, the second embodiment described above is applied.
That is, the movable blade 34 </ b> D of this embodiment is configured such that the inlet radius R <b> 1 is set larger than the inlet radius R <b> 2 of the fixed blade 35. Therefore, when the movable blade 34D is at an intermediate position between the adjacent fixed blades 35, the inlet radius R1 of the movable blade 34D is less than that of the throat A2 hypothesized between the blades formed by the adjacent fixed blades 35. 34D blade leading edge is set to be upstream.

  With such a configuration, when the movable wing 34D and the fixed wing 35 overlap each other, the pressure recovery rate is the same as that of the N chord node specific wings, and when both wings are installed at equal intervals, the number of wings Since there are 2N sheets, the pressure recovery rate is high. Therefore, by adopting the configuration of this embodiment, the performance can be improved by setting the movable blade 34D and the fixed blade 35 at equal intervals when the flow rate is small, while maintaining the characteristics of the low chord ratio diffuser.

Next, a modification of the present embodiment will be described with reference to FIG. In this modification, the fixed wing 35 is a small chord ratio blade as in the embodiment shown in FIG. 8, and the trailing edge radius R3 of the movable wing 34E is set larger than the trailing edge radius R4 of the fixed wing 35. .
With such a configuration, the following characteristics can be obtained. That is, as shown in FIG. 9A, when the movable wing 34E and the fixed wing 35 are separated and the number of blades is 2N, the wing area of the movable wing 34E is larger than the small chord joint ratio diffuser. The pressure recovery rate will increase.
Further, when the movable blade 34E is at the position shown in FIG. 9B, a wide range characteristic in which a throat is not formed is shown.
When the movable blade 34E is located at the position shown in FIG. 9C, a high pressure recovery rate similar to that of a normal vane diffuser with N blades is shown.

  For this reason, when the movable blade 34E is on the pressure surface side of the fixed blade 35 with respect to the substantial throat, the fixed blade 35 functions as a small chord joint blade, and therefore the flow rate range defined by the choke flow rate Qc and the surge flow rate Qs is While maintaining the expanded wide range, the movable blade 34E can increase the pressure. Therefore, if the configuration of this embodiment is adopted, the performance can be improved by setting the movable blade 34E and the fixed blade 35 at equal intervals when the flow rate is small, while maintaining the characteristics of the low chord ratio diffuser. Wide range (expansion of flow range) and high pressure ratio can be achieved at the same time.

<Sixth Embodiment>
Next, a sixth embodiment of the present invention will be described with reference to FIGS.
This embodiment relates to the sliding mechanism portion 45 of the driving device 40 that rotates the movable disk 31 and is particularly suitable for reducing the gap δ between the wall surface of the fixed disk 32 and the movable blade 34. Concerning structure.
A drive device 40A shown in FIG. 11 includes a sliding mechanism 45A configured by a guide groove 48 formed in the housing 11 and a convex portion 49 provided at the lower end of the movable disk 31.

On one side surface of the guide groove 48, there is provided a guide surface 48a having an arcuate shape (radius R). Similarly, on the convex portion 49 side, there is also provided a sliding surface 49a in which concaves and convexes having the same arc shape (radius R) are formed on the side surface facing the guide surface 48a. The sliding surface 49a is in contact with the guide surface 48a, and when the movable disk 31 is rotated, the arc-shaped uneven contact positions formed on both sides move in the circumferential direction.
In addition, a seal member 50 is attached to the housing 11 so as to be in contact with a surface on the outer peripheral side of the movable disc 31 when viewed from the diffuser passage 33 side and exhibit a sealing function. The seal member 50 prevents the airflow flowing through the diffuser passage 33 from leaking through the sliding mechanism portion 45A.

With such a configuration, the movable disk 31 moves in a direction toward or away from the fixed disk 32 in accordance with the uneven contact position between the guide surface 48a and the sliding surface 49a. The distance between the surfaces is changed. Hereinafter, the change in the inter-surface distance will be specifically described with reference to FIGS. 12 and 13.
The movable disc 31 is rotated at the movable disc 31 side so that a convex portion formed on the stationary guide surface 48a and a convex portion formed on the sliding surface 49a come into contact with each other (FIG. 12). An arc between a gap reduction position (indicated by a solid line in FIG. 12A) where the unevenness of the guide surface 48a and the unevenness of the sliding surface 49a come into contact with each other is indicated. Reciprocally move in the radius R direction.

As a result, the gap δ formed between the tip of the movable blade 34 and the hub side wall surface 32a is reduced as shown in FIG. 13 from the maximum value (indicated by a one-dot chain line in the figure) at the gap forming position. It changes within the range up to the minimum value (indicated by a solid line in the figure) at the position.
FIG. 12B shows the change of the gap δ corresponding to the movable range θ of the movable disk 31. The minimum gap at the gap reduction position is the unevenness of the guide surface 48a and the unevenness of the sliding surface 49a. By optimization, δ≈0, which is almost none, can be obtained. For this reason, since the amount of airflow leakage through the gap δ decreases at the gap reduction position, the efficiency of the compressor provided with the variable diffuser can be improved.

In addition, it is preferable that the above-described sliding mechanism portion 45A is rotated stepwise at a pitch of the unevenness using a gap reduction position where the unevenness of the guide surface 48a and the unevenness of the sliding surface 49a mesh.
That is, since the position of the movable blade 34 is fixed in a stepwise manner, it is possible to prevent the blade position from being fluctuated due to backlash of the drive device 40A or external vibration, and the characteristics of the compressor can be stabilized.

In the above-described variable diffuser, for example, as shown in FIG. 14, the shroud side wall surface 31 a and the fixed blade 35 between the blades of the movable blade 34 are obtained so that good slidability can be obtained even without the gap δ. The sliding surface 51 is formed on the hub side wall surface 32a between the blades. Specifically, a sliding surface may be formed by applying, for example, a fluororesin such as tetrafluoroethylene to the wall surface between the blades.
With such a configuration, the movable disk 31 can be smoothly rotated without the gap δ. Further, if the diffuser outlet pressure is pressed from the back side of the movable disk 31, even if there are no irregularities such as the guide surface 48a and the sliding surface 49a described above, the clearance δ can be eliminated and an improvement in efficiency can be achieved. it can.

In the above description, the guide surface 48a and the sliding surface 49a are arcuate. However, as in the first modification shown in FIG. 15, for example, the guide surface 48b and the sliding surface having the same sinusoidal unevenness. 49b may be used.
Alternatively, as in the second modification shown in FIG. 16, a guide groove 48 'is formed in the housing 11 on the fixed side, and a necessary number of rotatable rings 52 are installed at appropriate positions in the guide groove 48'. It is good. In this case, when the movable disk 31 rotates, the arc-shaped or sinusoidal sliding surface 49a slides with respect to the rotating ring 52. Therefore, like the above-described guide surfaces 48a and 48b, the gap is reduced at the gap reduction position. δ can be eliminated.

  Moreover, about the setting of the movable wing | blade and fixed wing | blade demonstrated by said embodiment, you may set a fixed side and a rotation side reversely. In other words, the fixed wing inlet radius and the movable wing inlet radius are reversed, the fixed wing leading edge angle and the moving wing leading edge angle are reversed, or the fixed wing and moving wing are small. Similar effects can be obtained by reversing the wings of the chord joint specific wing or by reversing the size of the trailing edge radius of the fixed wing and the trailing edge radius of the movable wing.

Thus, according to the variable diffuser structure of the present invention, it is possible to eliminate a decrease in efficiency due to an increase in incidence or leakage from the gap δ, and to provide a variable diffuser with further improved efficiency. Therefore, a compressor such as a centrifugal compressor or a mixed flow compressor provided with this variable diffuser can further improve its performance.
In addition, this invention is not limited to embodiment mentioned above, In the range which does not deviate from the summary of this invention, it can change suitably.

  The diffuser and the compressor of the present invention can be applied to, for example, a turbocharger, a marine supercharger, a small aviation gas turbine, and an industrial centrifugal compressor or mixed flow compressor.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows 1st Embodiment which concerns on the variable diffuser of this invention, (a) is a disassembled perspective view of the principal part, (b) is AA sectional drawing of (a). FIGS. 2A and 2B are views showing the operation of the variable diffuser shown in FIG. 1, in which FIG. 1A shows a state where A11 = A12, FIG. And the case where it is set in the middle of (b). FIGS. 8A and 8B are views showing the operation of the variable diffuser according to the second embodiment of the present invention, where FIG. 5A shows the case where the movable blade inlet radius is larger than that of the fixed blade, and FIG. (C) shows the case where the leading edge of the movable blade is downstream of the intersection point X and rotates. It is a figure which shows the variable diffuser which concerns on the 3rd Embodiment of this invention. It is a figure which shows the characteristic of the variable diffuser shown in FIG. It is a figure which shows the variable diffuser which concerns on the 4th Embodiment of this invention. It is a figure which shows the characteristic of the variable diffuser shown in FIG. It is a figure which shows the variable diffuser which concerns on the 5th Embodiment of this invention. It is a figure which shows the modification of the variable diffuser which concerns on 5th Embodiment shown in FIG. It is a figure which shows the relationship between a pressure recovery rate and the number of blades about a vane diffuser and a low chord joint ratio diffuser. It is a perspective view of the principal part which shows the variable diffuser which concerns on the 6th Embodiment of this invention. FIG. 12 is an explanatory diagram of the sliding mechanism shown in FIG. 11, where (a) shows the operation of the sliding surface relative to the guide surface, and (b) shows the gap δ that changes as the movable disk rotates. FIG. It is a figure which shows the state of the movable disc and movable blade which are moved by the sliding mechanism part shown in FIG. It is sectional drawing which shows the structural example which provided the sliding surface in the wall surface between the blades of a movable blade and a fixed blade. It is a figure which shows the 1st modification of the sliding mechanism part shown in FIG. It is a figure which shows the 2nd modification of the sliding mechanism part shown in FIG. It is sectional drawing which shows the principal part of the conventional centrifugal compressor. It is a perspective view of the principal part which shows the prior art example of a variable diffuser. It is a figure which shows the characteristic of the variable diffuser shown in FIG. It is explanatory drawing which shows operation | movement of the variable diffuser shown in FIG. It is a figure which shows the relationship between incidence (In), a flow angle ((beta)), and a blade angle ((beta) k).

Explanation of symbols

30 variable diffuser 31 movable disk 31a shroud side wall surface 32 fixed disk 32a hub side wall surface 33 diffuser passage 34, 34A-E movable diffuser blade (movable blade)
35 Fixed diffuser wing (fixed wing)
40, 40A Drive device 41 Gear drive portion 42 Rack gear portion 43 Pinion gear 45, 45A Sliding mechanism portion 46 Guide rail 47 Concave groove portion 48 Guide groove 48a Guide surface 49 Convex portion 49a Sliding surface

Claims (10)

A diffuser passage is formed between the hub side wall surface and the shroud side wall surface that decelerates the airflow discharged from the outer peripheral end of the impeller rotating in the housing and restores the dynamic pressure to a static pressure, and diffuser blades are formed in the diffuser passage. In the variable diffuser provided,
Drive means for alternately fixing the diffuser blades in a circumferential direction to wall surface members forming the hub side wall surface and the shroud side wall surface and rotating one of the wall surface members coaxially with rotation of the impeller. A variable diffuser characterized by being provided.   2. The variable according to claim 1, wherein a movable range of the wall surface member rotated by the driving means is set so as to extend over the entire width between adjacent diffuser blades fixed to the fixed wall surface member. Diffuser.   The inlet radius (R1) of the diffuser blade provided on the rotating side of the wall member is set to be larger (R1> R2) than the inlet radius (R2) of the diffuser blade provided on the fixed side of the wall member. The variable diffuser according to claim 1 or 2, characterized in that   The blade leading edge angle (αk1) of the diffuser blade provided on the rotating side of the wall member is smaller than the blade leading edge angle (αk2) of the diffuser blade provided on the fixed side of the wall member at the same radial position (αk1 < The variable diffuser according to claim 3, wherein αk2) is set.   The blade leading edge angle (αk1) of the diffuser blade provided on the rotating side of the wall member is larger than the blade leading edge angle (αk2) of the diffuser blade provided on the fixed side of the wall member at the same radial position (αk1> The variable diffuser according to claim 3, wherein αk2) is set.   The variable diffuser according to claim 3, wherein the diffuser blade provided on the fixed side of the wall member is a low-string ratio blade.   The trailing edge radius (R3) of the diffuser blade provided on the rotating side of the wall member is set larger than the trailing edge radius (R4) of the diffuser blade provided on the fixed side of the wall member (R3> R4). The variable diffuser according to claim 6.   The variable diffuser according to claim 3, wherein the fixed side and the rotating side are set in reverse.   The drive means includes a sliding mechanism part in which a rotating side of the wall surface member reciprocates between a gap forming position and a gap reducing position with respect to a fixed side of the wall surface member. The variable diffuser according to any one of 1 to 7.   A compressor comprising the variable diffuser according to any one of claims 1 to 9 at an outer peripheral end of an impeller that rotates within a housing.

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