JP6926550B2 - Centrifugal compressor - Google Patents

Description

The present invention relates to a centrifugal compressor.

A centrifugal compressor in which a diffuser having a plurality of vanes is arranged on the outer circumference of an impeller is known. The diffuser restores the static pressure of the flow after leaving the impeller of the centrifugal compressor. Such a centrifugal compressor may be operated at a flow rate at which the rotation speed is constant and the pressure ratio is maximized. The point indicated by this flow rate and the maximum pressure ratio is called a specification point. When the flow rate decreases or increases with respect to the flow rate that becomes the maximum pressure ratio, the pressure ratio tends to decrease. That is, the operating efficiency of the centrifugal compressor is reduced. If the diffuser vane is designed to obtain high efficiency (pressure ratio) for a specific condition, the pressure ratio tends to decrease with respect to a slight fluctuation in flow rate. On the contrary, if the diffuser vane is designed so that the pressure ratio does not change easily even if the flow rate fluctuates, the maximum pressure ratio tends to be low.

For example, Patent Documents 1 and 2 disclose a technique for suppressing a decrease in pressure ratio when the flow rate of a fluid provided to a centrifugal compressor changes. In the technique of Patent Document 1, each of the plurality of vanes is composed of two vane bodies. Then, the relative positional relationship between the vanes is changed according to the flow rate.

Japanese Unexamined Patent Publication No. 58-160597 Japanese Unexamined Patent Publication No. 2001-214896

The centrifugal compressor disclosed in Patent Documents 1 and 2 includes a mechanism for driving each of a plurality of vanes. That is, it has a drive mechanism that drives the vane body by the number of vanes. Therefore, as the number of drive mechanisms increases, the structure of the centrifugal compressor tends to be complicated as a whole.

Therefore, an object of the present invention is to provide a centrifugal compressor capable of suppressing a decrease in the pressure ratio due to a fluctuation in the flow rate by a simple configuration.

A centrifugal compressor according to an embodiment of the present invention includes an impeller and a vaned diffuser having a plurality of vanes arranged around the impeller, and the vaned diffuser has a rotation axis of the impeller as a central axis. It has a first annular base formed around the impeller, a second annular base formed around the first base so that the rotation axis of the impeller is the central axis, and a first blade angle. The relative positions of the first vane fixed to the first base, the second vane fixed to the second base so as to have the second blade angle, and the first and second bases change around the rotation axis. Driven to.

According to this configuration, the vanes are divided in the circumferential direction, and the relative positions of the first vane and the second vane are changed according to the operating state of the centrifugal compressor. Therefore, it is possible to suppress a decrease in the pressure ratio due to fluctuations in the flow rate. Then, the first and second vanes share one central axis and can change their positions relative to the central axis. Therefore, since the drive mechanism is simplified, the configuration of the centrifugal compressor can be simplified.

In one form, the first and second bases have a first form in which the trailing edge of the first vane is combined with the leading edge of the second vane, and the trailing edge of the first vane with the leading edge of the second vane. It may be driven to switch between the second form shifted in the circumferential direction on the rotation axis. According to this configuration, the positional relationship between the first vane and the second vane can be adjusted so as to correspond to each time when the flow rate increases and when the flow rate decreases. Therefore, it is possible to suppress a decrease in the pressure ratio due to a change in the flow rate from the specification point.

In one form, the ratio of the chord length of the first vane to the pitch of the first vane may be 1 or less. According to this configuration, the secondary flow generated between the vanes as the flow rate decreases suppresses the mainstream separation. Therefore, it is possible to suppress a decrease in the pressure ratio due to the separation of the flow.

In one form, in the first form, the first flow path is formed by the third vane formed by overlapping the trailing edge of the first vane and the leading edge of the second vane, and in the second form, the first A second flow path is formed by the virtual line regarding the position of the second vane in the form and the second vane, and a third flow path is formed by another first vane and the second vane adjacent to the first vane. The first throat length (r1) in the first flow path is the total throat length (r2 + r3) which is the sum of the second throat length (r2) in the second flow path and the third throat length (r3) in the third flow path. ) May be smaller (r1 <r2 + r3). According to this configuration, the throat length of the second form can be made larger than that of the first form. Therefore, the flow rate that can flow between the vanes increases. Therefore, since the tendency toward the blocked state is suppressed as the flow rate increases, the decrease in the pressure ratio can be suppressed.

According to the present invention, there is provided a centrifugal compressor that suppresses a decrease in pressure ratio due to fluctuations in flow rate by a simple configuration.

FIG. 1 is a diagram schematically showing a configuration of a turbocharger including a centrifugal compressor according to the present embodiment. FIG. 2 is a diagram showing a first form of the vaned diffuser. FIG. 3 is a diagram showing a second form of the vaned diffuser. FIG. 4 is a graph showing the characteristics of the centrifugal compressor. FIG. 5 is a diagram for explaining an example of the second form of the vaned diffuser. FIG. 6 is a diagram for explaining another example of the second form of the vaned diffuser.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate description will be omitted.

As shown in FIG. 1, the supercharger 1 is applied to, for example, an internal combustion engine 100 of a ship or a vehicle. The supercharger 1 includes a turbine 2 and a compressor 3 (centrifugal compressor). The turbine 2 includes a turbine housing 4 and a turbine impeller 6 housed in the turbine housing 4. The compressor 3 includes a compressor housing 7 and a compressor impeller 8 (impeller) housed in the compressor housing 7. The turbine impeller 6 is provided at one end of the rotating shaft 9, and the compressor impeller 8 is provided at the other end of the rotating shaft 9. A bearing housing 13 is provided between the turbine housing 4 and the compressor housing 7. The rotating shaft 9 is rotatably supported by the bearing housing 13 via a bearing, and the rotating shaft 9, the turbine impeller 6 and the compressor impeller 8 rotate about the rotating axis X as an integral rotating body 14.

The turbine housing 4 is provided with an exhaust gas inlet (not shown) and an exhaust gas outlet 16. The exhaust gas discharged from the internal combustion engine 100 flows into the turbine housing 4 through the exhaust gas inlet, rotates the turbine impeller 6, and then flows out of the turbine housing 4 through the exhaust gas outlet 16.

The compressor housing 7 is provided with a suction section 17 and a discharge section (not shown). When the turbine impeller 6 rotates, the compressor impeller 8 rotates via the rotating shaft 9. The rotating compressor impeller 8 sucks in an external fluid such as air through the suction section 17, compresses it, and discharges (pressure feeds) it from the discharge section. The compressed fluid discharged from the discharge unit is supplied to the internal combustion engine 100 described above.

As shown in FIG. 2, the compressor 3 further includes a vaned diffuser 18. FIG. 2 is a schematic view of the compressor impeller 8 and the vaned diffuser 18 of the compressor 3 as viewed from the direction of the rotation axis X. The vaned diffuser 18 is arranged around the compressor impeller 8. The vaned diffuser 18 has a plurality of vanes 19. These plurality of vanes 19 satisfy the condition of having a throat. This content will be explained in detail in a later paragraph. The plurality of vanes 19 are arranged at equal intervals around the rotation axis X and extend from the inside to the outside of a circle centered on the rotation axis X. For example, the vane 19A cooperates with another vane 19B adjacent to each other to form the third flow path FP3.

The vaned diffuser 18 has a base 21 to which a plurality of vanes 19 are fixed. The base 21 has an inner base 22 (first base) and an outer base 23 (second base). The inner base 22 is formed around the compressor impeller 8. The inner base 22 has an annular shape with the rotation axis X of the compressor impeller 8 as the central axis. The inner base 22 is an area set as a part of the compressor housing 7.

The outer base 23 is formed around the inner base 22. Like the inner base 22, the outer base 23 also has an annular shape with the rotation axis X of the compressor impeller 8 as the central axis. Here, unlike the inner base 22, the outer base 23 is a component having an annular shape attached to the compressor housing 7. That is, the outer base 23 is a separate component from the compressor housing 7. The outer base 23 has an inner peripheral edge 23a and an outer peripheral edge 23b. Then, the inner peripheral edge 23a of the outer base 23 comes into contact with the outer peripheral edge 22b of the inner base 22. According to such a configuration, the outer base 23 can rotate with the rotation axis X of the compressor impeller 8 as the rotation axis.

The vane 19 (third vane) is divided in the circumferential direction and has an inner vane 24 (first vane) and an outer vane 26 (second vane).

The inner vane 24 is arranged on the side of the rotation axis X. That is, the inner vane 24 is fixed to the inner base 22. More specifically, the inner vane 24 is formed integrally with the inner base 22 so as to have a first blade angle. Since the inner vane 24 is a part of the compressor housing 7, the inner vane 24 does not rotate around the rotation axis X. The leading edge 24a of the inner vane 24 overlaps the inner peripheral edge 22a of the inner base 22. Further, the trailing edge 24b of the inner vane 24 overlaps the outer peripheral edge 22b of the inner base 22. The inner vane 24 satisfies the condition of low solidity. This content will be explained in detail in a later paragraph.

The outer vane 26 is arranged outside the inner vane 24. That is, the outer vane 26 is fixed to the outer base 23. More specifically, the outer vane 26 is formed integrally with the outer base 23 so as to have a second blade angle. As described above, since the outer base 23 is rotatable around the rotation axis X of the compressor impeller 8, the outer vane 26 can also rotate around the rotation axis X. The leading edge 26a of the outer vane 26 overlaps the inner peripheral edge 23a of the outer base 23. Therefore, the leading edge 26a of the outer vane 26 is combined with the trailing edge 24b of the inner vane 24. Specifically, the leading edge 26a contacts the trailing edge 24b. Alternatively, the leading edge 26a faces the trailing edge 24b with a slight gap. Further, the trailing edge 26b of the outer vane 26 overlaps with the outer peripheral edge 23b of the outer base 23.

According to such a configuration, as shown in FIG. 2, the vaned diffuser 18 changes the relative positions of the inner base 22 and the outer base 23 around the rotation axis X. According to this change in relative position, the inner vane 24 and the outer vane 26 form a single vane 19 (first form), and the inner vane 24 and the outer vane 26 are independent as shown in FIG. It can take a form treated as a vane (second form). That is, the inner base 22 and the outer base 23 are driven so as to switch between the first form and the second form.

In the first form (see FIG. 2), the trailing edge 24b of the inner vane 24 and the leading edge 26a of the outer vane 26 are brought into contact with each other to form a single vane 19A. Then, one third flow path FP3 is formed between the vane 19A and the vane 19B adjacent to the vane 19A. The third flow path FP3 has a portion formed between the inner vanes 24 and a portion formed between the outer vanes 26.

In the second form (see FIG. 3), the outer base 23 is rotated clockwise CW from the first form to separate the leading edge 26a of the outer vane 26 from the trailing edge 24b of the inner vane 24. According to this second form, the first flow path FP1 and the second flow path FP2 having different properties are formed. The first flow path FP1 is formed by an inner vane 24 and an outer vane 26 that is in contact with the inner vane 24. The second flow path FP2 is formed by another inner vane 24 adjacent to the inner vane 24 and an outer vane 26. As described above, the second form is a form in which the inner vane 24 and the outer vane 26 do not form one vane 19, so that a plurality of forms can be taken depending on the rotation angle of the outer base 23 (the second form). (See FIG. 5).

The first form and the second form are switched between each other by a drive mechanism 27 (see FIG. 1) attached to the outer base 23. The drive mechanism 27 applies torque to the outer base 23 by a predetermined mechanism (for example, a link mechanism) to rotate the outer base 23. Further, the drive mechanism 27 holds the position of the outer base 23. That is, the position of the outer base 23 which is the first form is held. It also holds the position of the outer base 23, which is the second form. The drive mechanism 27 maintains the second form after receiving the first control signal from the controller 28 and switching from the first form to the second form. On the contrary, the drive mechanism 27 maintains the first form after receiving the second control signal from the controller 28 and switching from the second form to the first form.

Here, the configuration of the inner vane 24 and the outer vane 26 will be described in detail.

Part (a) of FIG. 4 is a diagram showing the characteristics of the compressor 3. Specifically, the pressure ratio obtained when the rotation speed of the compressor impeller 8 is constant and a fluid having a predetermined flow rate is introduced into the compressor 3 is shown. Generally, the compressor 3 is operated in a state where a flow rate that maximizes the pressure ratio is introduced. The point indicated by the maximum pressure ratio and the flow rate that maximizes the pressure ratio is referred to as a specification point P1.

The graph G1 shows the characteristics when the inner vane 24 and the outer vane 26 are regarded as one vane 19, that is, in the first form (see FIG. 2). As can be seen from the graph G1, when the flow rate introduced into the compressor 3 increases more than the flow rate at the specification point P1, the pressure ratio decreases.

The configuration of the vaned diffuser 18 in the first embodiment will be described in more detail. As shown in FIG. 2, the vaned diffuser 18 in the first form has a throat between the vanes 19. “Having a throat” means that a plurality of inscribed circles C having a first contact point on the inner vane 24 of the vane 19B and a second contact point on the outer vane 26 of the vane 19A can be defined. The locus at the center of these inscribed circles C can also be called a streamline. Then, according to the diameter of the inscribed circle C, the cross-sectional area intersecting the streamline can be shown. Then, as shown in the part (b) of FIG. 4, when the cross-sectional area of the flow path along the streamline is shown, there is a position PS where the cross-sectional area is the smallest. This position is where the throat was formed.

Once the cross-sectional area of the flow path in the throat is determined, the flow rate at which the flow path can smoothly flow the fluid is determined. Therefore, when the flow rate of the air provided to the compressor 3 becomes larger than the flow rate, it becomes difficult to smoothly discharge the sucked air. Therefore, it can be said that it is difficult for the compressor 3 to suck in air. That is, it can be said that the compressor 3 is heading toward the closed state. That is, it is difficult to suck air into the compressor 3.

In order to improve the above-mentioned state, the cross-sectional area of the flow path may be increased. The cross-sectional area of the flow path can be obtained by using the diameter of the inscribed circle C and the height of the flow path described above. The diameter of the inscribed circle C1 in the throat that minimizes the cross-sectional area is referred to as the throat length r1 (first throat length). Therefore, in order to eliminate the blocked state, the throat length r1 of the vaned diffuser 18 may be made larger than that of the first form. Therefore, the outer base 23 is rotated as in the second form.

Part (a) of FIG. 5 shows the configuration of the second form of the vaned diffuser 18. Specifically, it is the second form when the flow rate increases. It has already been described that in the second form, the first flow path FP1 and the second flow path FP2 are formed. Inscribed circles C2 and C3 corresponding to these first flow path FP1 and second flow path FP2 can be defined, respectively.

First, in the first flow path FP1, an inscribed circle C2 having a contact on the virtual line VL and also having a contact with the outer vane 26 of the vane 19A is defined. According to this inscribed circle C2, the throat length r2 (second throat length) is shown. The virtual line VL is an outer line of the outer vane 26 in contact with the inner vane 24 in the first form.

On the other hand, the second flow path FP2 defines an inscribed circle C3 having a contact point on the inner vane 24 of the vane 19B and a contact point on the outer vane 26 of the vane 19A. According to this inscribed circle C3, the throat length r3 (third throat length) is shown.

The total throat length (r2 + r3) in the second form is the sum of the throat length r2 of the first flow path FP1 and the throat length r2 of the second flow path FP2. The sum (r2 + r3) may be larger than the throat length r1 in the first form. That is, the second form of the vaned diffuser 18 when the flow rate increases is a form that satisfies the relationship of r1 <r2 + r3.

Part (a) of FIG. 5 is an example of the second form satisfying the above-mentioned throat length relationship. In this example, if the arrangement angle of the inner vane 24 is the pitch t1 and the rotation angle of the outer vane 26 is the angle t2, t2 can be shown as 3/4 × t1. According to this configuration, the rotation angle of the outer base 23 (that is, the outer vane 26) is the smallest projected area D of the inner vane 24 and the outer vane 26 with respect to the air inflow direction (diffuser inflow flow direction) into the vaned diffuser 18. (See part (b) of FIG. 5). As shown in part (b) of FIG. 5, when the flow rate increases (that is, the first component V1a corresponding to the flow rate extends), the vector Va indicating the inflow direction to the diffuser changes from the circumferential direction to the radial direction. Get closer. By providing an overlap in the arrangement of the inner vane 24 and the outer vane 26 so as to correspond to this inclination, the throat is increased and the fluid loss is reduced.

Even if the flow rate introduced into the compressor 3 is smaller than the flow rate at the specification point P1 (also referred to as an operating point), the pressure ratio is lowered. However, the cause is considered to be different from the case where the flow rate is increased.

Part (a) of FIG. 6 shows the velocity vector V (diffuser inflow velocity vector) of the fluid flowing into the vaned diffuser 18. The velocity vector V is a vector sum of the first component V1 (radial velocity vector) proportional to the flow rate and the second component V2 (circumferential velocity vector) in the circumferential direction around the rotation axis X. The blade angle of the vane 19 is set to correspond to the direction of the velocity vector V. That is, it corresponds to the direction of the velocity vector V when the flow rate indicates the specification point P1 (see part (a) of FIG. 4).

The velocity vector V contains a first component V1 that is proportional to the flow rate. Then, when the flow rate decreases, the length of the first component V1 becomes shorter, so that the direction of the velocity vector V changes. When the direction of the velocity vector V changes, a secondary flow called a secondary flow FS is generated in addition to the main flow in the flow path (see FIG. 2). Due to this secondary flow FS, the pressure ratio drops.

This secondary flow FS is reduced in the vane 19 in which the configuration of the vane 19 satisfies the condition of low solidity. This is because the vane 19 satisfying the condition of low solidity can exert a stall suppressing effect. Here, the solidity is a value indicated by the ratio (c / t) of the chord length (c) of the vane and the pitch (t). And low solidity means that the ratio is less than 1 (c / t <1). According to this condition, there is no throat between vanes. Specifically, an inscribed circle tangent to each of the inner vanes 24 cannot be defined between the inner vanes 24 of the vanes 19A and the inner vanes 24 of the vanes 19B.

The outer vane 26 is separated from the inner vane 24 as much as possible so that the inner vane 24 controls the flow in the vaned diffuser 18. In other words, as shown in part (b) of FIG. 6, the rotation angle t3 of the outer base 23 is set to 1/2 × t1 with reference to the state of the first form. According to this setting, the distance between the trailing edge 24b of the inner vane 24 and the leading edge 26a of the outer vane 26 is the longest. Therefore, it is possible to suppress the interference (effect) of the outer vane 26 with respect to the flow field of the inner vane 24.

Next, the operation of the compressor 3 will be described. In the initial state, the vaned diffuser 18 of the compressor 3 is in the first form (see FIG. 2). This first form is a form adapted to the operation at the specification point P1 (see the part (a) of FIG. 4). During the operation of the compressor 3, the compressor 3 measures the flow rate and the pressure ratio by using the inlet sensor S1 provided in the suction unit 17 and the outlet sensor S2 provided in the discharge port. The flow rate and pressure ratio measurements are transmitted to the controller 28. The controller 28 outputs the first control signal or the second control signal to the drive mechanism 27 as needed based on the flow rate and the pressure ratio. The first control signal includes a command to the second form corresponding to the case where the flow rate increases and the pressure ratio decreases. The second control signal includes a command to the second form corresponding to the case where the flow rate decreases and the pressure ratio decreases.

For example, when the flow rate increases and the pressure ratio becomes smaller than a predetermined value, the controller 28 outputs the first control signal to the drive mechanism 27. The drive mechanism 27 that has received the first control signal rotates the outer base 23 clockwise CW by 3/4 pitch to maintain its position. The flow rate-pressure ratio characteristic of the compressor 3 at this time is shown in graph G2 in FIG. Explaining the operation using the graphs G1 and G2, first, the pressure ratio (PR1) decreases to the point P2 in the graph G1 by increasing the flow rate to the flow rate FB1. Therefore, by switching to the second mode, the characteristics of the compressor 3 change to the characteristics shown in the graph G2. Then, when the flow rate is FB1, the characteristics of the compressor 3 change from the point P2 to the point P3. The pressure ratio at point P3 is PR2. The pressure ratio (PR2) of the graph G2 is larger than the pressure ratio (PR1) of the graph G1. Therefore, the pressure ratio recovers.

On the other hand, when the flow rate decreases and the pressure ratio becomes smaller than the predetermined value, the controller 28 outputs the second control signal to the drive mechanism 27. The drive mechanism 27 that has received the second control signal rotates the outer base 23 clockwise CW by 1/2 pitch to maintain its position. The flow rate-pressure ratio characteristic of the compressor 3 at this time is shown in graph G3 in FIG. Explaining the operation using the graphs G1 and G3, first, the flow rate decreases to the flow rate FB2, so that the pressure ratio (PR3) decreases to the point P4 in the graph G1. Therefore, by switching to the second mode, the characteristics of the compressor 3 change to the characteristics shown in the graph G3. Then, when the flow rate is FB2, the pressure ratio in the graph G3 is PR4. The pressure ratio (PR4) of the graph G3 is larger than the pressure ratio (PR3) of the graph G1. Therefore, the pressure ratio recovers.

In short, the compressor 3 measures the flow rate and the pressure ratio as described above during its operation period, determines whether or not the flow rate and the pressure ratio satisfy the conditions, and if the conditions are satisfied, the first form is used. It is maintained, and if the conditions are not satisfied, the first control signal or the second control signal is output.

When designing such a vaned diffuser 18, first, a specification point P1 for which efficiency is desired to be maximized is determined. Next, the shape of the vane 19 in the first form is determined. That is, the vanes 19 are designed to have a throat between the vanes 19. Next, the division position of the vane 19 is determined. The division position is a position where the inner vane 24 satisfies the condition of low solidity and the total throat length (r2 + r3) becomes larger than the throat length (r1) in the first form when the outer vane 26 is shifted. Set. That is, the inner vane 24 is set to satisfy the condition of low solidity in order to cope with the decrease in the flow rate. Further, in order to cope with the increase in the flow rate, the condition that the total throat length (r2 + r3) becomes larger than the throat length (r1) in the first form is set.

Hereinafter, the action and effect of the compressor 3 will be described.

In the compressor 3, each of the vanes 19 is divided in the circumferential direction, and the relative positions of the inner vane 24 and the outer vane 26 are changed according to the operating state of the compressor 3. Therefore, it is possible to suppress a decrease in the pressure ratio due to fluctuations in the flow rate. The inner vane 24 and the outer vane 26 share one central axis, and their positions can be changed relative to the central axis. Therefore, since the drive mechanism 27 is simplified, the configuration of the compressor 3 can be simplified.

According to the vaned diffuser 18, the positional relationship between the inner vane 24 and the outer vane 26 can be adjusted so as to correspond to each time when the flow rate increases and when the flow rate decreases. Therefore, it is possible to suppress a decrease in the pressure ratio due to a change in the flow rate from the specification point P1.

In the second form of the vaned diffuser 18, the ratio of the chord length of the inner vane 24 to the pitch of the inner vane 24 is 1 or less. That is, the inner vane 24 satisfies the condition of low solidity. According to this configuration, it is possible to reduce the secondary flow FS generated between the vanes 19 as the flow rate decreases. Therefore, it is possible to suppress a decrease in the pressure ratio due to the secondary flow FS.

According to the second form of the vaned diffuser 18, the total throat length (r2 + r3) of the second form can be made larger than the throat length r1 of the first form. Therefore, the flow rate that can flow between the vanes 19 increases. Therefore, since the tendency toward the blocked state is suppressed as the flow rate increases, the decrease in the pressure ratio can be suppressed.

The present invention has been described in detail above based on the embodiment. However, the present invention is not limited to the above embodiment. The present invention can be modified in various ways without departing from the gist thereof.

In the second form, the inner vane 24 and the outer vane 26 need only be displaced relative to each other. In the above embodiment, the configuration in which the outer vane 26 is rotated has been described as an example. However, the outer vane 26 (that is, the outer base 23) may be fixed and the inner vane 24 (that is, the inner base 22) may be rotated. Further, both the inner vane 24 and the outer vane 26 may be configured to be rotatable.

Further, in the transition from the first form to the second form, in the above embodiment, the outer base 23 is rotated in the clockwise direction CW. However, there is no particular limitation on this rotation direction. In the transition from the first form to the second form, the outer base 23 may be rotated counterclockwise.

1 Supercharger 2 Turbine 3 Turbine 4 Turbine housing 6 Turbine impeller 7 Compressor housing 8 Compressor impeller 9 Rotating shaft 13 Bearing housing 14 Rotating body 16 Exhaust gas outlet 17 Suction part 18 Vane Diffuser 19, 19A, 19B Vane ( 3rd vane)
21 Base 22 Inner base (1st base)
23 Outer base (2nd base)
22a, 23a Inner peripheral edge 22b, 23b Outer peripheral edge 24 Inner vane (first vane)
26 Outer vane (second vane)
24a, 26a Front edge 24b, 26b Rear edge 27 Drive mechanism 28 Controller 100 Internal engine C, C1, C2, C3 Inscribed circle CW Clockwise D Projected area FP1 First flow path FP2 Second flow path FP3 Third flow path FS Secondary flow G1, G2, G3 Graph P1 Specification point PS Position r1, r2, r3 Throat length S1 Inlet sensor S2 Exit sensor t1 Pitch t2 Angle t3 Rotation angle V Velocity vector V1 First component V2 Second component VL Virtual line X rotation Axis

Claims (3)

With an impeller
A vaned diffuser having a plurality of vanes arranged around the impeller.
The vaned diffuser is
An annular first base formed around the impeller so that the rotation axis of the impeller is the central axis, and
An annular second base formed around the first base so that the rotation axis of the impeller is the central axis, and
A first vane fixed to the first base so as to have a first blade angle,
A second vane fixed to the second base so as to have a second blade angle,
The first base and the second base are driven so that their relative positions around the rotation axis change.
The first base and the second base, a first embodiment the front edge of the second vane to the trailing edge of the first vane is contact, of the second vane with respect to the trailing edge of the first vane A centrifugal compressor driven to switch between a second form in which the leading edge is shifted in the circumferential direction on the rotation axis. The centrifugal compressor according to claim 1, wherein the ratio of the chord length of the first vane to the pitch of the first vane is 1 or less. In the first form, a third flow path is formed by a third vane formed by abutting the trailing edge of the first vane and the leading edge of the second vane.
In the second form, the first flow path is formed by the virtual line regarding the position of the second vane in the first form and the second vane, and at the same time, with another first vane adjacent to the first vane. A second flow path is formed by the second vane.
The first throat length (r1) in the third flow path is the total throat length which is the sum of the second throat length (r2) in the first flow path and the third throat length (r3) in the second flow path. The centrifugal compressor according to claim 1, which is smaller than (r2 + r3) (r1 <r2 + r3).

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