JP6785623B2 - Fluid machine - Google Patents

Description

The present invention relates to a fluid machine including a bladed diffuser.

Centrifugal fluid machines having a rotating centrifugal impeller have been conventionally used in various plants, air conditioners, liquid pressure pumps, turbochargers and the like. In response to the increasing demand for reduction of environmental load in recent years, fluid machines such as centrifugal fluid machines are required to have higher efficiency and higher operating range than before.

In a single-stage centrifugal blower, which is a type of centrifugal fluid machine, one impeller is fastened to a cantilever shaft, and a diffuser and a scroll are generally provided on the downstream side thereof. .. As the diffuser, a vaneless diffuser and a diffuser with blades are installed according to the use and purpose.

A small chord ratio diffuser, which is a type of winged diffuser, is so short that the line drawn perpendicular to the line along the entrance angle at the leading edge of the diffuser wing does not intersect the adjacent wing. For this reason, the small chord ratio diffuser is characterized by having no throat in the blade row, and prevents the blade surface from peeling off due to the effect of sweeping out the boundary layer on the blade surface due to the secondary flow in the low flow rate range. It is often used when you want to secure.

A two-dimensional blade in which a reference airfoil is laminated in parallel in the blade height direction (blade span direction) is generally used for a bladed diffuser for centrifugal fluid machines represented by a small chord ratio diffuser. ing. However, due to the demand for further performance improvement, the blade shape has been made three-dimensional.

For example, in Patent Document 1, when stacking reference airfoils in the blade height direction in order to define the blades of the diffuser, the airfoils are moved in the forward or reverse direction with respect to the rotation direction of the impeller. The technique of laminating is disclosed. As a result, the pressure plane and the negative pressure plane formed in the blade height direction are represented by the free curved surface.

Japanese Unexamined Patent Publication No. 2012-122443

The diffuser described in Patent Document 1 controls the direction of the wing force acting from the wing to the fluid by expressing the pressure plane and the negative pressure plane of the wing with a free curved surface, and suppresses the development of the secondary flow. It is a feature. The shape of the blade of the diffuser described in Patent Document 1 is applied to a fluid machine including a closed impeller with blades provided between a hub plate and a shroud plate.

On the other hand, a fluid machine equipped with an open type impeller without a shroud plate is a closed type impeller in that the presence of a blade tip leak flow that develops on the shroud surface side of the impeller affects the flow in the diffuser. It is different from the equipped fluid machine. Therefore, the shape of the blades of the diffuser described in Patent Document 1 cannot sufficiently suppress the backflow generated in the diffuser of the fluid machine provided with the open impeller.

The present invention has been made in view of the above circumstances, and an object of the present invention is to further suppress backflow in a bladed diffuser in a fluid machine provided with an open impeller.

In order to achieve the above problems, the fluid machine according to the present invention includes a hub plate having a circular tube shape, an open type impeller having a plurality of blades arranged on the outer peripheral surface of the hub plate, and the impeller. The bladed diffuser is provided with a bladed diffuser arranged downstream of the impeller, and the bladed diffuser is spaced in the circumferential direction in a flow path formed between a hub surface and a shroud surface on the downstream side of the impeller. Each of the blades is perpendicular to the blade height direction in the blade height direction in which the reference blade shape is the axial direction of the rotation axis of the impeller. It is formed in a laminated shape with movement in the plane, and is a chord connecting the front edge and the trailing edge of the reference blade shape in the movement direction in the plane perpendicular to the blade height direction. The dihedral distribution, which is a component in the direction perpendicular to the direction and whose forward movement is to move in the direction opposite to the rotation direction of the impeller, is monotonous from the hub surface toward the shroud surface. After increasing and showing one maximum value, it monotonically decreases from the position showing the maximum value to the shroud surface, and the position showing the maximum value is said to be higher than the central position in the blade height direction of the blade. It is set on the hub surface side, and is characterized in that 70% or more of the total area of the blade surface of the blade is inclined with respect to the rotation axis .

According to the present invention, in a fluid machine including an open impeller, backflow in a bladed diffuser can be further suppressed.

It is a cross-sectional view of the meridional plane which shows the fluid machine which concerns on one Embodiment of this invention. It is a figure for demonstrating the method of defining the shape of a blade by laminating the reference airfoil. It is a figure which shows an example of the dihedral distribution of the blade of a diffuser. It is a figure which shows the appearance of the blade of the diffuser which concerns on the conventional comparative example. It is a figure which shows the appearance of the blade of the diffuser which concerns on this embodiment. FIG. 6A is a cross-sectional view of the meridional plane schematically showing the flow of the design points at the flow rate in the diffuser according to the comparative example. FIG. 6B is a cross-sectional view of the meridional plane schematically showing the flow of the design points at the flow rate in the diffuser according to the present embodiment. FIG. 7A is a cross-sectional view of the meridional plane schematically showing the flow at the flow rate of the non-design point in the diffuser according to the comparative example. FIG. 7B is a cross-sectional view of the meridional surface schematically showing the flow of the non-design point at the flow rate in the diffuser according to the present embodiment. It is a graph comparing the performance of the fluid machine equipped with the diffuser according to the conventional comparative example, and the fluid machine equipped with the diffuser according to this embodiment. FIG. 9A is a diagram schematically showing an example of a flow field around the diffuser obtained by numerical analysis in a fluid machine equipped with a diffuser according to a conventional comparative example. FIG. 9B is a diagram schematically showing an example of a flow field around the diffuser obtained by numerical analysis in the fluid machine equipped with the diffuser according to the present embodiment.

Embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
In each figure, common components and similar components are designated by the same reference numerals, and duplicate description thereof will be omitted as appropriate.

FIG. 1 is a cross-sectional view of the meridional plane showing the fluid machine 100 according to the embodiment of the present invention. The meridional cross section is a projection of each part on a cross section of the fluid machine 100 cut by a plane including the central axis of the rotating shaft 2. In the present embodiment, an example in which the fluid machine 100 is a single-stage (one-stage) centrifugal fluid machine will be described.

In the following description, the centrifugal fluid machine means, for example, a centrifugal blower, a centrifugal blower, or a centrifugal compressor. Further, the present invention can be applied to all single-stage and multi-stage centrifugal fluid machines, and is not particularly limited to single-stage ones.

As shown in FIG. 1, the fluid machine 100 includes a centrifugal impeller (hereinafter, also simply referred to as “impeller”) 1, a rotating shaft 2, a suction port pipe 3, an inlet guide vane 4, and a diffuser with blades (hereinafter, simply referred to as “impeller”). It also has a (also referred to as a "diffuser") 5 and a scroll 6.

The impeller 1 mainly applies energy to the fluid by rotating. The rotating shaft 2 is for rotating the impeller 1. The suction port pipe 3 is provided upstream of the air introduction portion of the impeller 1. The inlet guide vane 4 is provided downstream of the suction port pipe 3 and imparts an arbitrary turning speed to the inflow flow to the impeller 1. The diffuser 5 is arranged downstream of the impeller 1, that is, outside in the radial direction. The diffuser 5 is a small string ratio diffuser, and converts the dynamic pressure of the fluid flowing in from the outlet of the impeller 1 into a static pressure. The scroll 6 is provided downstream of the diffuser 5.

The impeller 1 has a hub plate 1a having a circular tube shape, and a plurality of blades 1b arranged on the outer peripheral surface of the hub plate 1a at intervals in the circumferential direction, and does not have a shroud plate. .. That is, the impeller 1 is an open type impeller.

The diffuser 5 has a plurality of blades 11 arranged at intervals in the circumferential direction in a flow path formed between the hub surface 12 and the shroud surface 13 on the downstream side of the impeller 1. Here, the blade 11 is erected on the hub surface 12 which is the surface of the hub plate portion 8 attached to the casing 7. The blade 11 of the diffuser 5 appropriately diverts the flow from the outlet of the impeller 1 to improve the efficiency of static pressure recovery.

The impeller 1 and the diffuser 5 are covered with a casing 7 to form a flow path. In the fluid machine 100 including the open type impeller 1, a gap is formed between the blade 1b of the impeller 1 and the inner wall surface 14 of the casing 7 due to its structure. Further, the casing 7 forms a shroud surface 13 at the portion of the diffuser 5. The casing 7 has a hollow shape, and the rotating shaft 2 is supported by a bearing (not shown) at the center of the casing 7. A drive device (not shown) is connected to the end of the rotating shaft 2.

The casing 7 is formed with a suction passage 22 in which the fluid is sucked toward the impeller 1 along the axial direction of the impeller 1. The fluid is taken into the impeller leading edge 15 through the suction passage 22. Further, the casing 7 is formed with a discharge passage 23 for discharging the fluid compressed by the impeller 1 along the radial direction orthogonal to the axial direction of the impeller 1. The discharge passage 23 is arranged on the outer peripheral side of the impeller 1.

In the fluid machine 100 configured in this way, when the rotating shaft 2 is rotated by a drive device (not shown), the impeller 1 rotates and the fluid is sucked into the casing 7 through the suction port pipe 3. The sucked fluid is boosted in the process of passing through the inlet guide vane 4 and the rotating impeller 1, and then the dynamic pressure of the compressed fluid is converted to static pressure when passing through the diffuser 5 and the scroll 6, and the discharged fluid is not shown. It is discharged from the outlet to the outside.

FIG. 2 is a diagram for explaining a method of defining the shape of the airfoil 11 by stacking (stacking) the reference airfoils 11a.
As shown in FIG. 2, each blade 11 of the diffuser 5 of FIG. 1 is perpendicular to the airfoil height direction with the reference airfoil 11a maintaining the size of the airfoil 11a in the airfoil height direction. It is formed in a laminated shape with movement in a plane. Here, the blade height direction is the axial direction of the rotating shaft 2 of the impeller 1. The plane perpendicular to the blade height direction is a plane parallel to the paper surface of FIG.

Here, among the moving directions in the plane perpendicular to the blade height direction, the rotation of the impeller 1 is a component in the direction perpendicular to the chord C direction connecting the leading edge 101 and the trailing edge 102 of the airfoil 11a. Moving in the direction opposite to the direction is called forward dihedral movement. Further, the movement amount in the dihedral movement direction is defined as the dihedral amount Δδ. The distribution showing the relationship between the position in the blade height direction and the dihedral amount Δδ is called a dihedral distribution.

On the other hand, among the moving directions in the plane perpendicular to the blade height direction, the component in the direction parallel to the chord C direction connecting the front edge 101 and the trailing edge 102 of the airfoil 11a is to be moved downstream. Is called a forward sweep movement. Further, the movement amount in the sweep movement direction is defined as the sweep amount Δσ. In this embodiment, the case where the sweep amount Δσ = 0 will be described.

FIG. 3 is a diagram showing an example of the dihedral distribution of the blade 11 of the diffuser 5. In FIG. 3, the dihedral quantity Δδ is made dimensionless by being divided by the length of the chord C (chord length) L (see FIG. 2). Further, the position in the blade height direction is based on the edge position on the hub surface 12 (= 0), and is dimensionless by being divided by the total height of the blade.

As shown in FIG. 3, the dihedral distribution of the blade 11 (see FIG. 1, the same applies hereinafter) of the diffuser 5 according to the present embodiment is from the hub surface 12 (see FIG. 1, the same applies hereinafter) to the shroud surface 13 (see FIG. 1, the same applies hereinafter). It increases toward (the same applies thereafter), shows one maximum value P, and then decreases. On the other hand, the dihedral distribution of the blade 21 (see FIG. 4) of the diffuser 20 according to the comparative example does not change from the hub surface 12 to the shroud surface 13.

In the present embodiment, the position showing the maximum value P in the dihedral distribution is set on the hub surface 12 side of the center position M in the blade height direction of the blade 11. Here, the position showing the maximum value P intersects the shroud surface 13 with the edge position intersecting with the hub surface 12 at 0% (indicated by “0.0” in FIG. 3) in the blade height direction of the blade. When the edge position is 100% (indicated by "1.0" in FIG. 3), the position is set to 25% or more and less than 50%, preferably 30% or more and 45% or less.

FIG. 4 is a diagram showing the appearance of the blade 21 of the diffuser 20 according to the conventional comparative example. FIG. 5 is a diagram showing the appearance of the blade 11 of the diffuser 5 according to the present embodiment.

As shown in FIG. 5, the line defining the leading edge 101 of the blade 11 of the diffuser 5 according to the present embodiment is the impeller 1 (FIG. 1) with reference to a point on the hub surface 12 or a point on the shroud surface 13. A curve is formed so as to be separated from the trailing edge 16 (see FIG. 1) of the impeller (see, the same applies hereinafter).

Further, in the present embodiment, 70% or more of the total area of the blade surface of the blade 11 is inclined with respect to the rotation shaft 2 of the impeller 1 (see FIG. 1, the same applies hereinafter). Here, as shown in FIG. 3, the dihedral distribution monotonically increases from the hub surface 12 to the position showing the maximum value P from the hub surface 12 toward the shroud surface 13, and from the position showing the maximum value P to the shroud surface 13 It is decreasing monotonically. That is, here, of the entire region of the blade surface of the blade 11, the region other than the position showing the maximum value P is inclined with respect to the rotation axis 2 of the impeller 1.
The blade surface is a general term for the pressure surface 103 and the negative pressure surface 104, which will be described later. Further, "monotonically increasing" means constantly increasing in the entire target section, and "monotonically decreasing" means constantly decreasing in the entire target section.

As shown in FIG. 4, the blade 21 of the diffuser 20 according to the conventional comparative example is used when stacking the reference airfoil 11a (see FIG. 2, the same applies hereinafter) in the blade height direction which is the axial direction of the rotation shaft 2. In addition, it is formed in a shape in which they are stacked parallel to each other in the blade height direction.

On the other hand, as shown in FIG. 5, the blade 11 of the diffuser 5 according to the present embodiment is formed in a shape in which the airfoils 11a are laminated according to the dihedral distribution as shown in FIG. Therefore, the pressure surface 103 and the negative pressure surface 104 of the blade 11 have a curved surface. Further, the curved surface is formed so that the dihedral distribution first increases (moves in the positive direction) from the hub surface 12 to the shroud surface 13. Further, the curved surface shows one maximum value P (see FIG. 3) from the hub surface 12 to the central position M in the blade height direction, and then decreases from the shroud surface 13 (negative). It's turning in the direction). The negative pressure surface 104 is a blade surface on the back side with respect to the rotation direction of the impeller 1.

By having the shape in which the blades 11 of the diffuser 5 are laminated and formed according to the dihedral distribution as shown in FIG. 3, the direction of the blade force acting on the fluid passing between the adjacent blades 11 changes. .. As a result, the static pressure distribution in the flow path between the adjacent blades 11 changes. Then, according to the present embodiment, the hub surface 12 or the location where the backflow region is generated on the hub surface 12 side or the shroud surface 13 side of the negative pressure surface 104 of the blade 21 in the shape of the blade 21 according to the conventional comparative example The wing force toward the shroud surface 13 can be applied, and the occurrence of backflow can be suppressed.

It is said that the backflow region in the diffuser 5 is generated when the equilibrium of the radial outward force generated by the flow is lost with respect to the static pressure rising outward in the radial direction. The radial outward force generated by this flow is due to the centrifugal force caused by the circumferential component of the flow and the radial momentum per unit time passed when the radial component is decelerated. The peeling and backflow that occur on the hub surface 12 and the shroud surface 13 are caused by the radial outward force due to the flow not overcoming the cross-sectional average static pressure gradient and flowing from the region where the static pressure is high to the region where the static pressure is low. It is considered to be. That is, by controlling the direction of the blade force acting on the blade surface of the blade 11, peeling and backflow can be suppressed.

Next, with reference to FIGS. 6 to 7, the mechanism for suppressing peeling and backflow in the diffuser 5 according to the present embodiment will be described.
FIG. 6A is a cross-sectional view of the meridional plane schematically showing the flow of the design point at the flow rate in the diffuser 20 according to the comparative example. FIG. 6B is a cross-sectional view of the meridional plane schematically showing the flow of the design points at the flow rate in the diffuser 5 according to the present embodiment. FIG. 7A is a cross-sectional view of the meridional plane schematically showing the flow at the flow rate of the non-design point in the diffuser 20 according to the comparative example. FIG. 7B is a cross-sectional view of the meridional plane schematically showing the flow of the non-design point at the flow rate in the diffuser 5 according to the present embodiment.
The arrows shown in FIGS. 6 and 7 represent the streamlines of the flow passing through the negative pressure surface 104 side of the blades 11 and 21 of the diffuser 5. FIG. 6 shows an example of the flow field in the case of the vicinity of the design point and FIG. 7 shows the case of the flow rate lower than the design point.

Basically, the flow field boosted by the impeller 1 has a non-uniform flow distribution 201 from the hub surface 12 to the shroud surface 13 as shown on the left side of FIGS. 6 and 7. In FIGS. 6 and 7, the flow distribution 201 is represented as a two-dimensional line, but in reality, not only the flow velocity is different, but also the flow angle is different, so that the flow is three-dimensionally very complicated. It will be. In particular, in the fluid machine 100 having the open type impeller 1 targeted in the present embodiment, there is a blade tip leakage flow between the blade 1b of the impeller 1 and the inner wall surface 14 of the casing 7 (FIG. 1). reference). Therefore, the meridional direction (direction along the flow path in the meridional cross section; radial direction in the diffuser 5) component of the flow is very low, and the circumferential component is often dominant. Depending on the flow rate conditions, there may be conditions such as backflow to the impeller 1 side. When such a flow field flows into the diffuser 20 according to the conventional comparative example, the flow near the hub surface 12 and the shroud surface 13 cannot overcome the cross-sectional average static pressure gradient in the flow path of the diffuser 20. , The backflow D shown by the broken line in FIGS. 6 (a) and 7 (a), and peeling will occur.

In the case of a fluid machine having a closed impeller, the flow velocity at the outlet of the impeller is often high in the meridional direction on the shroud side, and as shown in FIG. 6, the flow velocity in the meridional direction suddenly occurs near the shroud surface 13. It is basically different from the flow distribution 201 in which the value is reduced. As a result, in a fluid machine having a closed type impeller, backflow is likely to occur mainly on the hub surface 12 side, and backflow phenomenon does not occur so much on the shroud surface 13 side. Therefore, it is not necessary to pay much attention to the shape of the wing 11 on the shroud surface 13 side.

On the other hand, in the fluid machine 100 having the open type impeller 1 which is the target of the present embodiment, the flow angle on the shroud side is small and the flow velocity in the meridional direction is also low. For this reason, backflow D often occurs on the shroud surface 13 side at the time when the fluid flows into the blade row portion composed of the plurality of blades 11 of the diffuser 5 (see FIG. 6A).

Therefore, in the present embodiment, the dihedral distribution of the blade 11 is monotonically reduced from the central position M in the blade height direction having the dihedral amount Δδ in the positive direction to the shroud surface 13. That is, in the present embodiment, the radial amount Δδ in the positive direction is given from the central position M in the blade height direction to the shroud surface 13, and the blade 11 is deformed so that the blade surface is inclined with respect to the rotation axis 2. Has been done. As a result, as shown in FIG. 6B, it is possible to apply a blade force that forcibly brings the streamline on the negative pressure surface 104 of the blade 11 toward the shroud surface 13 side. Since this wing force exerts the effect of pushing back the backflow D as shown in FIG. 6A, the backflow D on the shroud surface 13 can be suppressed.

Further, as shown in FIG. 7, when the operating conditions of the fluid machine 100 are different from the design points, the flow distribution 201 generally tends to have a sharp decrease in the flow velocity in the meridional direction on the hub surface 12 side. It is in. Therefore, backflow D occurs on the hub surface 12 regardless of whether the impeller 1 is an open type or the impeller is a closed type (see FIG. 7A).

Therefore, in the present embodiment, the dihedral distribution of the blade 11 increases from the hub surface 12 toward the central position M in the blade height direction, and shows one maximum value P up to the central position in the blade height direction. .. That is, in the present embodiment, the impeller 1 is provided with the positive dihedral amount Δδ from the hub surface 12 to the central position M in the blade height direction, and the dihedral amount Δδ starts to decrease. A convex portion having a convex shape in the direction opposite to the rotation direction is provided. As a result, as shown in FIG. 7B, it is possible to apply a blade force that forcibly brings the streamline on the negative pressure surface 104 of the blade 11 toward the hub surface 12 side. Since this wing force exerts the effect of pushing back the backflow D as shown in FIG. 7A, the backflow D on the hub surface 12 can be suppressed.

It is important to properly apply the wing force to both the hub surface 12 side and the shroud surface 13 side. In particular, in the flow field at the non-design point, a relatively large backflow tends to occur on the hub surface 12 side, while the backflow on the shroud surface 13 side has a large difference between the design point and the non-design point. Hard to appear. Therefore, as shown in FIG. 3, in the dihedral distribution of the blade 11, a steeply inclined portion A showing a steep inclination is provided on the hub surface 12 side, and a gently inclined portion B showing a relatively gentle inclination on the shroud surface 13 side. It is important to adjust the wing force by providing. Therefore, it is an important factor to further suppress backflow on both the hub surface 12 side and the shroud surface 13 side by providing a convex portion on the hub surface 12 side as much as possible so that the dihedral amount Δδ that increases in the positive direction starts to decrease. It becomes. Here, the inclination is a value obtained by dividing the amount of change in the dihedral amount Δδ by the amount of change in the position in the blade height direction.

FIG. 8 is a graph comparing the performance of the fluid machine equipped with the diffuser 20 (see FIG. 4) according to the conventional comparative example and the fluid machine 100 equipped with the diffuser 5 (see FIG. 5) according to the present embodiment. is there. The graph shown in FIG. 8 shows a comparison of the insulation efficiencies of fluid machinery.
As shown in FIG. 8, the fluid machine 100 including the diffuser 5 according to the present embodiment is improved in efficiency by 1.2% at the design point E as compared with the fluid machine including the diffuser 20 according to the conventional comparative example. You can see that there is. From this, it can be said that the superiority of the shape of the blade 11 of the diffuser 5 according to the present embodiment is shown.

FIG. 9A is a diagram schematically showing an example of a flow field around the diffuser 20 obtained by numerical analysis (three-dimensional fluid analysis) in a fluid machine equipped with the diffuser 20 according to a conventional comparative example. FIG. 9B is a diagram schematically showing an example of a flow field around the diffuser 5 obtained by numerical analysis in the fluid machine 100 equipped with the diffuser 5 according to the present embodiment. The flow fields around the two diffusers shown in FIGS. 9 (a) and 9 (b) are those obtained at the same flow point.
As shown in FIG. 9A, in the diffuser 20 according to the comparative example, backflow flows onto the hub surface 12 and the shroud surface 13 on the negative pressure surface 104 side of the blade 21 of the diffuser 20 as shown in FIGS. 6 to 7. It can be seen that there is a region (backflow region) that causes D. On the other hand, as shown in FIG. 9B, it can be seen that the backflow region disappears on the negative pressure surface 104 side of the blade 11 of the diffuser 5 according to the present embodiment.
Further, in FIGS. 9 (a) and 9 (b), the limit streamlines on the hub surface 12 are also displayed. The critical streamline on the hub surface 12 in the downstream portion of the blade 11 of the diffuser 5 draws a streamline that swirls in the circumferential direction in the comparative example, whereas in the present embodiment, it slightly approaches in the radial direction. You can see that it draws a changed streamline. This means that in the present embodiment, the flow angle on the hub surface 12 side is increased, and the flow field is less likely to cause backflow.
As described above, from FIGS. 8 and 9, the superiority of the shape of the blade 11 of the diffuser 5 according to the present embodiment can be confirmed from both the performance (insulation efficiency) and the flow field.

As described above, in the present embodiment, each of the blades 11 of the diffuser 5 is laminated with the reference airfoil 11a moving in the blade height direction in a plane perpendicular to the blade height direction. It is formed in a vertical shape. Here, among the moving directions in the plane perpendicular to the blade height direction, the rotation of the impeller 1 is a component in the direction perpendicular to the chord C direction connecting the leading edge 101 and the trailing edge 102 of the airfoil 11a. Moving in the direction opposite to the direction is called forward dihedral movement. Then, the distribution showing the relationship between the position in the blade height direction and the dihedral amount is increased from the hub surface 12 to the shroud surface 13 and then decreased after showing one maximum value P. .. Further, the position showing the maximum value P in the dihedral distribution is set on the hub surface 12 side of the center position M in the blade height direction of the blade 11.

In such an embodiment, in the fluid machine 100 having the open impeller 1, a blade force toward the hub surface 12 and the shroud surface 13 is applied to the flow on the negative pressure surface 104 of the blade 11 of the diffuser 5. be able to. As a result, it is possible to suppress the occurrence of backflow on the hub surface 12 and the shroud surface 13. Moreover, since the position showing the maximum value P in the dihedral distribution is set on the hub surface 12 side of the center position M in the blade height direction of the blade 11, the hub is formed by the steeply inclined portion A formed on the hub surface 12 side. The wing force toward the surface 12 can be exerted more. As a result, it is possible to suppress the occurrence of backflow even in a flow field at a non-design point (at a low flow rate) where a relatively large backflow tends to occur on the hub surface 12 side.
That is, according to the present embodiment, in the fluid machine 100 including the open impeller 1, the backflow in the bladed diffuser 5 can be further suppressed.
Then, by suppressing the backflow in the bladed diffuser 5, it is possible to provide the fluid machine 100 capable of achieving high efficiency without impairing the operating range.

Further, in the present embodiment, the position showing the maximum value P is the case where the edge position intersecting the hub surface 12 is 0% and the edge position intersecting the shroud surface 13 is 100% in the blade height direction of the blade. It is set at a position of 25% or more and less than 50%. By setting the position showing the maximum value P within a predetermined range in this way, the flow field at the non-design point (at low flow rate) where a relatively large backflow tends to occur on the hub surface 12 side is included. Backflow can be further suppressed on both the hub surface 12 side and the shroud surface 13 side.

Further, in the present embodiment, 70% or more of the total area of the blade surface of the blade 11 is inclined with respect to the rotation shaft 2 of the impeller 1. According to such a configuration, since the inclined blade surface is formed in a wide range in the blade 11, it is possible to apply a larger blade force from the blade surface of the blade 11.

Further, in the present embodiment, the dihedral distribution monotonically increases from the hub surface 12 to the position showing the maximum value P from the hub surface 12 to the shroud surface 13, and monotonically decreases from the position showing the maximum value P to the shroud surface 13. doing. According to such a configuration, a larger blade force can be applied from the blade surface of the blade 11, and the flow on the negative pressure surface 104 of the blade 11 becomes smoother, so that the efficiency is improved.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications are included. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the described configurations. Further, it is possible to add / delete / replace a part of the configuration of the above-described embodiment with another configuration.

For example, in the above-described embodiment, the centrifugal fluid machine 100 is a centrifugal blower, a centrifugal blower, or a centrifugal compressor, but the present invention is not limited thereto. The present invention is also applicable to other centrifugal fluid machines such as pumps. The present invention is also applicable to a mixed flow type fluid machine.

Further, in the above-described embodiment, the blade 11 is erected on the hub surface 12 which is the surface of the hub plate portion 8 attached to the casing 7, but the present invention is not limited thereto. For example, the wing 11 may be erected on the shroud surface 13 which is the surface of the shroud plate portion attached to the casing 7. Alternatively, the blade 11 may be provided between the hub plate portion 8 and the shroud plate portion.

Further, in the above-described embodiment, the movement direction of the airfoil 11a when laminating the airfoil 11a as a reference for defining the blade 11 is only the movement in the dihedral movement direction (sweep amount Δσ = 0). However, the present invention is not limited to this. For example, the present invention can be applied even when the movement in the dihedral movement direction and the movement in the sweep movement direction are combined, and even in this case, the same effect as that of the above-described embodiment can be obtained. That is, the most important point in the present invention is that the dihedral distribution when stacking the airfoils 11a for defining the airfoils 11 has a shape as illustrated in FIG.

Further, in the dihedral distribution shown in FIG. 3, the dihedral amount on the shroud surface 13 is the same as the dihedral amount on the hub surface 12, but is not limited to this, and the dihedral amount on the hub surface 12 is not limited to this. It may be deviated in the positive direction or the negative direction with respect to the quantity.

1 Impeller 1a Hub plate 1b Blade 2 Rotating shaft 3 Suction port piping 4 Inlet guide vane 5 Diffuser 6 Scroll 7 Casing 8 Hub plate part 11 Wing 11a Airfoil 12 Hub surface 13 Shroud surface 14 Inner wall surface 15 Leading edge of impeller 16 blades Car trailing edge 22 Intake passage 23 Discharge passage 100 Fluid machinery 101 Leading edge 102 Trailing edge 103 Pressure surface (wing surface)
104 Negative pressure surface (wing surface)
201 Impeller outlet flow distribution A steep slope part B gentle slope part C chord D backflow E design point M center position P maximum value Δδ dihedral amount Δσ sweep amount

Claims (3)

A hub plate having a circular tube shape, and an open type impeller having a plurality of blades arranged on the outer peripheral surface of the hub plate, and
With a bladed diffuser located downstream of the impeller,
The bladed diffuser has a plurality of blades arranged at intervals in the circumferential direction in a flow path formed between a hub surface and a shroud surface on the downstream side of the impeller.
Each of the blades has a shape in which the reference airfoil is laminated in the blade height direction, which is the axial direction of the impeller rotation axis, with movement in a plane perpendicular to the blade height direction. Has been formed and
Of the moving directions in the plane perpendicular to the blade height direction, the component in the direction perpendicular to the chord direction connecting the front edge and the trailing edge of the reference airfoil and opposite to the rotation direction of the impeller. The dihedral distribution whose forward movement is to move in the direction monotonically increases from the hub plane toward the shroud plane, shows one maximum value, and then shows the maximum value. It decreases monotonically from to the shroud surface ,
The position showing the maximum value is set on the hub surface side of the center position in the blade height direction of the blade .
A fluid machine characterized in that 70% or more of the total region of the blade surface of the blade is inclined with respect to the rotation axis . The dihedral distribution monotonically increases from the hub surface toward the shroud surface, shows one maximum value at one point, and then monotonically decreases from the position showing the maximum value to the shroud surface. Ori,
The fluid machine according to claim 1, wherein a region other than the position showing the maximum value in the entire region of the blade surface of the blade is inclined with respect to the rotation axis. The position showing the maximum value is 25% or more and 50 when the edge position intersecting the hub surface is 0% and the edge position intersecting the shroud surface is 100% in the blade height direction of the blade. The fluid machine according to claim 1 or 2 , wherein the position is set to less than%.

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