Embodiment
Below, with reference to suitable accompanying drawing, describe embodiments of the present invention in detail.
Mode of execution 1
Mode of execution 1 explanation carrys out the example of the Diffuser that the centrifugal compressor of the fluids such as pressurized gas, liquid possesses by centrifugal impeller.
Fig. 1 be the centrifugal impeller that possesses of centrifugal compressor and Diffuser along the sectional view of meridian plane, Fig. 2 is the sectional view of the Sec1-Sec1 of Fig. 1.
In addition, Fig. 3 means the figure of the static pressure distribution in little chord-pitch ratio Diffuser.
As shown in Figure 1, centrifugal compressor 1 is configured to the Diffuser 4 that comprises centered by rotating shaft 3 centrifugal impeller 2 of rotation and form the mobile stream of the fluid sent for the peripheral portion 2a from centrifugal impeller 2.Diffuser 4 forms the dynamic pressure of sending from the centrifugal impeller 2 of rotation is converted to static pressure, and reduces the stream of stream wall friction.
As shown in Figure 1, centrifugal impeller 2 is configured to and comprises: wheel hub 2b, and it forms from rotating shaft 3 along circumferentially expansion; Guard shield 2c, it configures in the mode relative with wheel hub 2b; Blade 2d, it is upwards formed between wheel hub 2b and guard shield 2c to arrangement across appropriate intervals and in week.The fluid that the centrifugal impeller 2 being rotated centered by rotating shaft 3 sucks the suction port 2e to axially open guides along blade 2d, as shown in Figure 2, utilizes the centrifugal force producing by rotation convection cell, and this fluid is sent from peripheral portion 2a.
In addition, as shown in Figure 1, Diffuser 4 is to be clipped in to have and for the space between two sidewall 4a, 4b of the part of the plane of rotation almost parallel of the wheel hub 2b rotation of centrifugal impeller 2.Then, between sidewall 4a, 4b, form for fluid and carry out mobile stream, and then possess the stator 5 that convection cell carries out rectification.It should be noted that, in mode of execution 1, the sidewall of the wheel hub 2b side of centrifugal impeller 2 is made as to 4a, the sidewall of guard shield 2c side is made as to 4b.
In addition, by from forming a side's of Diffuser 4 sidewall 4a(4b) to the opposing party's sidewall 4b(4a) distance be called the height H d of Diffuser 4.
As shown in Figure 2, at the rounded leaf grating shape of radial outside of centrifugal impeller 2, configure the stator 5 of a plurality of Diffusers 4.In addition, stator 5 forms from the peripheral portion 2a of centrifugal impeller 2 to be expanded laterally, with respect to centrifugal impeller 2, radially has a suitable angle.This angle is such as being suitably defined as the angle consistent with the air-flow angle (absolute air flow angle α) of the fluid of sending with rated flow from the centrifugal impeller 2 rotating with rated speed etc.
It should be noted that shape, quantity for stator 5, can be suitable for the known technology relevant to Diffuser, according to centrifugal compressor 1 desired performance etc., suitably set.
In addition, the Diffuser 4 of mode of execution 1 is little chord-pitch ratio Diffuser, be configured to adjacent stator 5 the distance L of front edge 5a and the ratio of length (following, to be called chord C) along the stator 5 of meridian plane, be that chord-pitch ratio σ is less than 1.That is the mode of, setting up with following formula (1) forms stator 5.
σ=C/L<1 …(1)
The front edge 5a that it should be noted that stator 5 is the end of centrifugal impeller 2 sides in stator 5.
In addition, the front edge 5a of stator 5 is formed on the circumference of the radius r 1 centered by the rotating center of centrifugal impeller 2.The radius r 1 of the circumference below, front edge 5a being formed is called leading-edge radius.
Leading-edge radius r1 is set to the radius (following, to be called impeller radius r2) (r1 > r2) of the peripheral portion 2a that is greater than centrifugal impeller 2.By this structure, front edge 5a is away from the peripheral portion 2a configuration of centrifugal impeller 2.
This leading-edge radius r1 is set as the design load of suitable length in order to suppress the interference of the front edge 5a of stator 5 and the centrifugal impeller 2 of rotation.
The Diffuser 4 forming the like this dynamic pressure that the centrifugal force by the centrifugal impeller 2 of rotation produces by fluid is converted to static pressure.The fluid of sending at the peripheral portion 2a of the centrifugal impeller 2 from rotation, the speed composition (radial velocity component Vr) of generation from centrifugal impeller 2 to radial outside with along the speed composition (circumferential speed composition Vs) of circumferential direction, fluid has the speed composition (absolute velocity composition Vf) of the direction that radial velocity component and the addition of circumferential speed composition are obtained and is sent from peripheral portion 2a.In mode of execution 1, using the angle of this absolute velocity composition Vf and circumferential speed composition Vs formation as " absolute air flow angle α ".
According to the relation of sending the velocity triangle the outlet of fluid from centrifugal impeller 2, when the flow of the fluid of sending from centrifugal impeller 2 tails off, this absolute air flow angle α diminishes.
In addition, at sidewall 4a, the 4b(of Diffuser 4 with reference to Fig. 1) side, form the speed boundary layer of the impact of the caused resistance of viscosity that is subject to fluid.In speed boundary layer, the frictional force producing between the viscosity by fluid and sidewall 4a, 4b, reduces the flow velocity of fluid mobile in Diffuser 4, reduces therewith near the dynamic pressure sidewall of Diffuser 4 together.Here the dynamic pressure of saying represents the pressure by the radial velocity component Vr generation of fluid.
Like this, when the flow of the fluid of sending from centrifugal impeller 2 reduces, radial velocity component Vr reduces and absolute air flow angle α diminishes.Thus, the dynamic pressure that flow into the fluid between stator 5 reduces.
That is, be formed at the speed boundary layer of Diffuser 4, by the viscosity of fluid, the impact of friction or from centrifugal impeller 2(with reference to Fig. 1) flow of the fluid sent reduces to reduce dynamic pressure.
In addition, Diffuser 4 is converted to static pressure by expanding stream by dynamic pressure.Thereby waiting static pressure line shown in solid line PL in Fig. 3, becomes the static pressure distribution increasing downstream at the less static pressure of upstream end.
In addition produce from the larger static pressure in the downstream side power of the less static pressure of side (static pressure gradient Fs) upstream.
It should be noted that the upstream in Diffuser 4 is made as to centrifugal impeller 2(with reference to Fig. 2) side, downstream is made as along stator 5(with reference to Fig. 2) the flow downstream of fluid.In addition, at stator 5, the face that faces upstream becomes suction surface 50a, and the face that faces downstream becomes pressure side 50b.
As mentioned above, when dynamic pressure reduces in speed boundary layer, while reducing the power downstream from upstream producing because of dynamic pressure, exist from upstream power downstream to become and be less than the situation of static pressure gradient Fs.And, in this case, utilize from downstream upstream static pressure gradient Fs, near the speed boundary layer sidewall of Diffuser 4, produce and reflux.In addition, the backflow of generation produces rotating stall along circumferentially moving successively of centrifugal impeller 2.
Because the Diffuser 4 of mode of execution 1 is little chord-pitch ratio Diffuser, as shown in Figure 3, represent that the mobile streamline of fluid becomes obtuse angle with the angle β that line such as static pressure such as grade becomes.Therefore, from downstream upstream and and etc. the static pressure gradient Fs of direction of static pressure line quadrature less the flowing of dynamic pressure between stator 5 upstream turned to.In Fig. 3, static pressure gradient Fs turns to the low-yield fluid between stator 5 counterclockwise.
Particularly in the slack-off speed boundary layer of flow velocity, near the low-yield fluid alar wall face of stator 5 is subject to static pressure gradient Fs and turns to, as shown in dotted line FL in Fig. 3, produce from the Secondary Flow of the pressure side 50b side of the adjacent stator 5 of the suction surface 50a side direction of a stator 5.
When Secondary Flow as shown in Figure 3 results from Diffuser 4, the speed boundary layer of suction surface 50a side scans out pressure side 50b side, therefore can suppress near the peeling off alar wall face of stator 5.
By this structure, in the suction surface 50a side that forms the stator 5 of little chord-pitch ratio, be suppressed near the peeling off alar wall face the speed boundary layer of the less situation of the flow of the fluid of sending from centrifugal impeller 2, suppress the generation of surge.
Like this, as experimental result, obtain following situation: utilize the little chord-pitch ratio Diffuser that chord-pitch ratio σ is " 0.5~0.95 ", improve the effect that near the generation of the peeling off alar wall face of suction surface 50a side is suppressed.Thereby the Diffuser 4 of mode of execution 1 is preferably the little chord-pitch ratio Diffuser of the scope of chord-pitch ratio σ in " 0.5~0.95 ".
In addition, in mode of execution 1, in order to suppress by the rotating stall producing without wing space that forms the Diffuser 4 of little chord-pitch ratio, as shown in Figure 1, 2, stator 5 becomes the front edge 5a possessing from stator 5 and to the peripheral portion 2a of centrifugal impeller 2, extends the structure of the extension setting unit 6 arranging.
As shown in Figure 2, extend setting unit 6 form make stator 5 from front edge 5a upstream, be that the peripheral portion 2a of centrifugal impeller 2 extends the shape arranging.In addition, as shown in Figure 1, extend the height H t of setting unit 6 and form than the height H d lowland of Diffuser 4.
That is, extend setting unit 6 form erect the sidewall 4a(4b that is arranged at a side) and do not arrive the opposing party's sidewall 4b(4a) jut.And the extension setting unit 6 that is configured to the sidewall 4a that is formed at a side is faced with the extension setting unit 6 that is formed at the opposing party's sidewall 4b, two that face extend between setting units 6, do not form blade without wing space (interplane space 6a).It should be noted that reference character 6b represents to extend setting unit leading edge.
Fig. 4 means the figure of the effect of extending setting unit.
When extension setting unit 6 is set as shown in Figure 1, 2, as shown in single-point line in Fig. 4, the flow that can make to be accompanied by fluid reduces and the absolute air flow angle α that diminishes absolute air flow angle α 2(α < α 2 as shown by the solid line) turn to like that significantly.
Like this, can make fluid overcome static pressure gradient Fs(with reference to Fig. 3) and flow, the generation without near the backflow sidewall in wing space suppressed.Thereby, thereby inhibition suppresses the generation of rotating stall without the generation of the backflow in wing space.That is, by arranging, extend setting unit 6, can prevent the generation of recirculation zone, can suppress the generation of rotating stall.
In addition, extend setting unit 6 form erect the sidewall 4a(4b that is arranged at a side) and do not arrive the opposing party's sidewall 4b(4a).Thereby, can the characteristic that waits static pressure line between the stator 5 of little chord-pitch ratio Diffuser 4 not impacted, therefore can maintain the Secondary Flow characteristic of little chord-pitch ratio Diffuser 4, suppress the backflow of the suction surface 50a of stator 5.
In addition, as mentioned above, when extending setting unit 6 near the peripheral portion 2a of centrifugal impeller 2, can suppress the generation without near the backflow sidewall in wing space.
That is, stator 5 places by the Diffuser 4 at little chord-pitch ratio arrange extends setting unit 6, can effectively suppress stator 5 suction surface 50a peel off with sidewall without wing space near the generation of backflow, can effectively suppress the generation of surge, rotating stall.
Yet, extend setting unit 6 and extend and be set near the peripheral portion 2a of centrifugal impeller 2, thus centrifugal impeller 2 with extend setting unit 6 and become and easily interfere thereby easily produce noise.
Therefore, as shown in Figure 1, become following structure: the height H t that is formed at the extension setting unit 6 of sidewall 4a, 4b forms lower than the height H d of Diffuser 4 has interplane space 6a.
Utilize this structure, can reduce and extend height in setting unit 6, that face the extension setting unit leading edge 6b of centrifugal impeller 2, can alleviate centrifugal impeller 2 and the interference of extending setting unit 6.And, can reduce the noise that centrifugal impeller 2 and the interference of extending setting unit 6 produce.
In addition,, due to the speed boundary layer generation that is reduced in the friction that produces fluid and sidewall 4a, 4b of dynamic pressure, therefore, the backflow of fluid also easily produces in speed boundary layer.Thereby, can be the structure turning at sidewall 4a, absolute air flow angle, 4b vicinity α.That is,, even the extension setting unit 6 that forms lowlyer than the height H d of Diffuser 4 also can suitably turn to the absolute air flow angle α in speed boundary layer, can suppress the generation refluxing.And then, can suppress the generation of rotating stall.
It should be noted that extending setting unit 6 can be in the scope of the degree that can allow, closely to extend with centrifugal impeller 2 side joints the structure arranging in the noise suppression that the interference with centrifugal impeller 2 is produced.That is, extending setting unit 6 can be definite design load such as to measure by experiment to the length of centrifugal impeller 2 sides.
In addition, extend the height of setting unit 6, from a side sidewall 4a(4b) to the opposing party's sidewall 4b(4a) length can be the design load of correspondingly suitably setting with the size etc. that results from the speed boundary layer of Diffuser 4.
Variation
Fig. 5, Fig. 6 mean the figure of the variation of mode of execution 1.
As the variation of mode of execution 1, for example, as shown in the (a) and (b) of Fig. 5, can be also the structure that the extension setting unit 6 of stator 5 is formed on the either party in sidewall 4a, 4b.
In the (a) and (b) of Fig. 5, arrow represents the velocity flow profile (distribution of radial velocity component Vr) of fluid, longlyer just represents that flow velocity (radial velocity component Vr) is higher.
As shown in Fig. 5 (a), according to the shape of centrifugal impeller 2, there is at the flow velocity of the guard shield 2c of peripheral portion 2a side liquid the situation that raises, reduces at the flow velocity of wheel hub 2b side liquid.
In this case, even if the flow of the fluid of sending from centrifugal impeller 2 reduces, in guard shield 2c side, the minimizing of absolute air flow angle α is diminished, the reduction of the dynamic pressure of speed boundary layer is diminished.Thereby, need to absolute air flow angle α, not turn to extending setting unit 6 places, be configured to not at the sidewall 4b of guard shield 2c side and arrange and extend setting unit 6 and be also fine.
In addition, as shown in Fig. 5 (b), according to the shape of centrifugal impeller 2, have at the flow velocity of the wheel hub 2b of peripheral portion 2a side liquid and raise, situation about reducing at the flow velocity of guard shield 2c side liquid.
In this case, even if the flow of the fluid of sending from centrifugal impeller 2 reduces, less in the minimizing of wheel hub 2b side absolute air flow angle α, the reduction of the dynamic pressure of speed boundary layer diminishes.Thereby, need to absolute air flow angle α, not turn to extending setting unit 6 places, be configured to the structure that extension setting unit 6 is not set at the sidewall 4a place of wheel hub 2b side and be also fine.
In addition,, as other variation of mode of execution 1, as shown in the (a) and (b) of Fig. 6, also can become the structure that possesses the extension setting unit 6 increasing downstream and highly from upstream.
In Diffuser 4, the closer to downstream, the impact of the friction between fluid and sidewall 4a, 4b more makes speed boundary layer thickening in height H d direction along short transverse propagation.Thereby, by the extension setting unit 6 increasing in downstream side is set, can effectively suppress the generation of backflow of the speed boundary layer of thickening.
In addition,, in the upstream of Diffuser 4, the height that extends setting unit 6 reduces, and can effectively reduce the interference of extending setting unit 6 and centrifugal impeller 2.
For example, as shown in Fig. 6 (a), can be also from upstream downstream and the extension setting unit 6 highly increasing obliquely along meridian plane.
In addition, as shown in Fig. 6 (b), for example, also can be from upstream downstream and along meridian plane, be the extension setting unit 6 that circular-arc height increases.
In addition, though not shown, for example also can be from upstream downstream and along meridian plane, be the extension setting unit 6 that step-like height increases.
As mentioned above, in mode of execution 1, as shown in Figure 1, 2, the front edge side 5a of the stator 5 that the Diffuser 4 of little chord-pitch ratio possesses extends and arranges and formation extension setting unit 6 to centrifugal impeller 2 sides.Utilize this structure, can suppress the generation of the backflow of speed boundary layer, can prevent the generation of rotating stall.
In addition, extend setting unit 6 and form with the height H t lower than the height H d of Diffuser 4, between the extension setting unit 6 of sidewall 4a side and the extension setting unit 6 of sidewall 4b side, form interplane space 6a.Utilize this structure, can shorten the length of extending extension setting unit leading edge 6b in setting unit 6, that face with centrifugal impeller 2.Thereby, can maintain the effect of Secondary Flow at the interplane place of stator 5, can reduce near peeling off and centrifugal impeller 2 and the interference of extending setting unit 6 alar wall face, can reduce the noise that surge, centrifugal impeller 2 and the interference of extending setting unit 6 produce.
Mode of execution 2
Fig. 7 means the figure of the Diffuser of mode of execution 2, and the (a) and (b) of Fig. 8 are sectional views of the Sec2-Sec2 of Fig. 7.
The structure of the centrifugal impeller 2 of mode of execution 2, the structure of Diffuser 4 and mode of execution 1 is roughly the same, at the centrifugal impeller 2 with shown in Fig. 1, composed component that Diffuser 4 is identical, marks identical reference character detailed.
It should be noted that, the Diffuser 4 in mode of execution 2 is also little chord-pitch ratio Diffuser.
And the Diffuser 4 of mode of execution 2 is characterised in that, replaces the extension setting unit 6 shown in Fig. 1, is provided with the rib 7 with stator 5 discontinuous formation.
As shown in Figure 7, stator 5 forms front edge 5a in having the position of the leading-edge radius r1 larger than the impeller radius r2 of centrifugal impeller 2, and stator 5 forms front edge 5a away from the peripheral portion 2a of centrifugal impeller 2.Like this, from impeller radius r2 to leading-edge radius r1, be the region of the peripheral portion 2a side that impales of front edge 5a, form do not exist stator 5 without wing space S 1.And, in mode of execution 2, in without wing space S 1, be provided with rib 7.
Rib 7 erects sidewall 4a, the 4b that is arranged at Diffuser 4, and preferably, its height H t2 is preferably formed as structure lower than the height H d of Diffuser 4, that be connected with a side of sidewall 4a, 4b.By this structure, rib 7 forms and erects the sidewall 4a(4b that is arranged on a side) and do not arrive the opposing party's sidewall 4b(4a) the jut of height.
In addition, 7 pairs of fluids mobile in Diffuser 4 of rib carry out rectification, preferably, also have the function of the suction surface 50a of the adjacent stator 5 of the direct fluid of the sidewall Flow Structure Nearby without wing space S 1.Its plane shape (shape while carrying out projection to sidewall 4a, 4b) is not particularly limited, for example, can be to broaden gradually and then downstream and the shape that width narrows down gradually (wing shape) from upstream width.In addition, the plane shape of rib 7 can suitably determine according to centrifugal compressor 1 desired performance etc.
As shown in Fig. 8 (a), the rib 7 in mode of execution 2 for example in without wing space S 1 the suction surface 50a lateral deviation to stator 5 move formation.In addition, rib 7 is for example configured to expand laterally from the peripheral portion 2a of centrifugal impeller 2, with respect to centrifugal impeller 2, radially has a suitable angle.Angle that the mobile absolute air flow angle α of the fluid that this angle is sent with rated flow such as the centrifugal impeller 2 being suitably defined as from being rotated with rated speed is consistent etc.It should be noted that said rated flow here and rated speed are as the design load of centrifugal compressor 1 and definite value.
Adopt this structure, the absolute air flow angle α diminishing due to the flow minimizing of the fluid of sending from centrifugal impeller 2 etc. (among (a) of Fig. 8 by single-point line diagram) can turn to as larger absolute air flow angle α 2(α < α 2 by rib 7) (in (a) at Fig. 8, by solid line, being illustrated), to the suction surface 50a of adjacent stator 5, suitably import fluid.
In addition, the peripheral portion 2a of rib 7 and centrifugal impeller 2 approaches and forms, and height H t2(is with reference to Fig. 7) form lower than the height H d(of Diffuser 4 with reference to Fig. 7), therefore can reduce the interference with centrifugal impeller 2.Thereby, can suppress to interfere the generation of caused noise.
The thick arrow that it should be noted that Fig. 8 (a) represents flowing of fluid.
In addition, by make rib 7 be formed on to the suction surface 50a lateral deviation of stator 5 from position, can by the fluid high-effective of sending from centrifugal impeller 2 export to the suction surface 50a side of stator 5.Utilize this structure, can make thickness (to the length of the short transverse of the Diffuser 4) attenuation of speed boundary layer of the suction surface 50a side of stator 5, can suppress peeling off of alar wall face vicinity in suction surface 50a.
As shown in Fig. 8 (b), the length along meridian plane of rib 7 is made as to chord C2.In addition, the outer shape of stator 5 and rib 7 is made as to the continuous shape of circumference that makes inscribed circle, the mean camber line L2(of stator 5 is linked to the line that the center of inscribed circle forms) elongation line and the interval between the mean camber line L3 of rib 7 (along the circumferential interval of centrifugal impeller 2) be made as intercostal spacing Pt.
In this case, when the scope of intercostal spacing Pt in " 0 * C2~0.65 * C2 ", as experimental result, obtain can by fluid high-effective export to the situation of the suction surface 50a side of stator 5.Therefore, in mode of execution 2, preferably, so that the mode of the scope of intercostal spacing Pt in " 0 * C2~0.65 * C2 " forms rib 7.
The outer shape that it should be noted that stator 5 and rib 7 is not limited to make the continuous shape of circumference of inscribed circle.For example, stator 5 and rib 7 can be the dull and stereotyped wings of constant thickness, can be also to have the crooked wing.
For example, in the situation of the dull and stereotyped wing of constant thickness, can be made as and substitute mean camber line L2, L3 and crestal line (not shown) based on the dull and stereotyped wing is determined the configuration of stator 5 and rib 7, the structure of intercostal spacing Pt.
Variation
Fig. 9, Figure 10 mean the figure of the variation of mode of execution 2.
As the variation of mode of execution 2, as shown in the (a) and (b) of Fig. 9, also can be made as the structure that either party in sidewall 4a, 4b forms rib 7.In this situation, in the situation that the flow velocity (radial velocity component Vr) of the guard shield 2c side liquid of the peripheral portion 2a of centrifugal impeller 2 raises, as shown in Fig. 9 (a), the sidewall 4a that can become in wheel hub 2b side forms the structure of rib 7.In addition,, in the situation that the flow velocity (radial velocity component Vr) of the wheel hub 2b side liquid of the peripheral portion 2a of centrifugal impeller 2 raises, as shown in Fig. 9 (b), the sidewall 4b that can become in guard shield 2c side forms the structure of rib 7.
In addition as other variation of mode of execution 2, as shown in Figure 10 (a), can be also to tilt and the rib 7 that highly increases downstream and along meridian plane from upstream.Or, can, as shown in Figure 10 (b), be to be also the rib 7 that circular-arc ground level increases downstream and along meridian plane from upstream.In addition, though not shown, can be to be also for example the rib 7 that step-like ground level increases downstream and along meridian plane from upstream.
As mentioned above, in Diffuser 4, the closer to downstream, speed boundary layer is more to height H d direction thickening.Thereby the rib 7 uprising by being made as downstream, can suppress the generation of backflow of the speed boundary layer of thickening effectively.
In addition, at the upstream end of Diffuser 4, reduce the height of rib 7, can effectively reduce the interference between rib 7 and centrifugal impeller 2.
As mentioned above, in mode of execution 2, as shown in Figure 7,8, do not form stator 5 without wing space S 1 in rib 7 is set.Utilize this structure, can suppress the generation of the recirculation zone in speed boundary layer, can prevent the generation of rotating stall.
In addition, rib 7 moves formation in the suction surface 50a of stator 5 lateral deviation, can by the fluid high-effective of sending from centrifugal impeller 2 export to suction surface 50a side.Utilize this structure, can make the thickness attenuation of speed boundary layer of the suction surface 50a side of stator 5, can suppress near the peeling off alar wall face of suction surface 50a.And, can suppress the generation of surge.
In addition, rib 7 is formed by the height H t2 lower than the height H d of Diffuser 4, can shorten the length on end limit in rib 7, that face with centrifugal impeller 2.Thereby, can reduce the interference of centrifugal impeller 2 and rib 7, can reduce the caused noise of interference of centrifugal impeller 2 and rib 7.
It should be noted that, the present invention is not subject to above-mentioned mode of execution and limits.For example, above-mentioned mode of execution describes in detail for the ease of understanding explanation the present invention, not necessarily leaves no choice but to be subject to possessing illustrated entire infrastructure and limits.
In addition, a part for the structure of a certain mode of execution can be replaced into the structure of other mode of executions, or also can in the structure of a certain mode of execution, increase the structure of other mode of executions.
For example, in mode of execution 1, be made as at sidewall 4a, 4b(with reference to Fig. 1) upper formation extend setting unit 6(with reference to Fig. 1) structure, but can be also that a square one-tenth at sidewall 4a, 4b extends setting unit 6, the opposing party, form rib 7(with reference to Fig. 7) structure.That is, can be also mode of execution 1 and the appropriately combined structure forming of mode of execution 2.
In addition, in mode of execution 2, with respect to a stator 5(with reference to Fig. 8 (a)) and form the structure of a rib 7, but can be also with respect to a stator 5, to form the structure of plural rib 7.
In addition, rib 7 is and the discrete structure of stator 5, but can be also the rib 7 of the shape that is connected with stator 5.The mobile structure that in this case, preferably can not hinder fluid.
In addition, as centrifugal compressor 1(with reference to Fig. 1) Diffuser 4(with reference to Fig. 1) be illustrated, but the present invention is not limited to centrifugal compressor 1, also can be applied to the Diffuser that blower, miscellaneous equipment have.
In addition, the present invention is not limited to above-mentioned mode of execution, can in the scope of purport that does not depart from invention, suitably change.