1
DESCRIPTION
MIXED FLOW TURBINE OR RADIAL TURBINE
Technical Field
[0001]
The present invention relates to a mixed flow turbine or
a radial turbine used in a small gas turbine, a turbocharger,
an expander, and the like.
Background Art
[0002]
In this type of turbine, a plurality of blades is
disposed in a radial pattern on the outer circumference of a
hub as disclosed for example in Patent Document 1.
The efficiency of a turbine is shown with respect to a
theoretical velocity ratio (=U/C0) being a ratio of peripheral
velocity U of the blade inlet, to a maximum flow velocity of a
working fluid (gas) accelerated by the turbine entry
temperature and its compression ratio, that is, a theoretical
velocity CO.
[0003]
A radial turbine has a certain theoretical velocity ratio
U/C0 where its efficiency reaches a peak. The theoretical

2
velocity CO is changed by changes in the state of the gas,
such as changes in gas temperature and gas pressure.
When the theoretical velocity CO changes, the inflow
angle of the gas that flows in to a leading edge of the blade
changes, and thus the angular difference between the leading
edge and gas inflow angle becomes greater.
When the angular difference between the leading edge and
the gas inflow angle becomes greater in this way, the
inflowing gas separates at the leading edge and collision loss
becomes greater, resulting in the occurrence of incidence loss.
[0004]
On the other hand, in a mixed flow turbine as shown in
FIG. 13, a blade 101, seen from a sectional surface 105 along
the outer circumference surface of a hub 103, is generally
configured such that a camber line (center line of the blade
thickness) 107 has a curved shape convexed toward a rotational
direction 109 side.
Therefore, since a shape that follows the flow of gas
flowing in on the blade angle α of a leading edge 102, in
other words, a shape that allows the blade angle α to match
the relative flow angle β, is possible, then for example the
blade angle α may be such as to reduce incidence loss at a low
theoretical velocity ratio (low U/C0).

3
Thus, if the efficiency at low U/CO can be improved, the
outline shape of the mixed flow turbine can be suppressed,
which is effective for response.
[0005]
Patent Document 1: Japanese Unexamined Patent Application,
Publication, No. 2002-364302
Disclosure of Invention
[0006]
Incidentally, a gas flow field in a mixed flow turbine is
basically formed by a free vortex. Therefore, for example,
the absolute circumferential flow velocity Cu is inversely
proportional to the radial position as shown in FIG. 3. On
the other hand, since the peripheral velocity U of the blade
101 is proportional to the radial position, a relative
circumferential flow velocity Wu occurs between the gas flow
and the blade 101.
Plotting the relative circumferential flow velocity Wu
against the radial position yields a curved line that is
convex-curved downward (convex curved in the counter-
rotational direction) as shown in FIG. 4. In other words, the
rate of change toward the rotational direction becomes greater
as the radial direction position becomes smaller, that is to
say, there is a rate of change toward the rotational direction.

4
FIG 5 schematically shows the changing trajectory of the
relative flow velocity at this time. The relative flow
velocity W is the synthesis of the relative circumferential
flow velocity Wu that changes according to FIG. 4, and the
substantially constant relative radial velocity Wr. The
change in the size in the relative flow velocity W has a trend
similar to that of the relative circumferential flow velocity
Wu shown in FIG. 4.
The angle formed between the relative flow velocity W and
the relative circumferential flow velocity Wu is a relative
flow angle β at that radial position.
[0007]
Even if the blade angle α of the leading edge is aligned
with the relative flow angle β (that is to say, the leading
edge is matched with the trajectory of the relative flow
velocity W), the distance therebetween rapidly increases
downstream from the leading edge, since the relative flow
velocity W is convex-curved in the counter-rotational
direction while the camber line 107 of the blade 101 is
convex-curved in the rotational direction (in other words, the
rate of change of the blade angle a in the rotational
direction becomes smaller as the radial direction position
becomes smaller, that is to say, there is a rate of change
toward the rotational direction). Since the distance between
them, that is, the load Fc applied on the blade, rapidly

5
increases, this load gives rise to a leakage flow from a
pressure surface side to a suction surface side, and incidence
loss occurs.
Moreover, when the gas inflow angle changes in response
to changes in the theoretical velocity CO, the inflowing gas
separates at the leading edge, so that collision loss becomes
greater and incidence loss occurs.
[0008]
In consideration of the above problems, an object of the
present invention is to provide a mixed flow turbine or a
radial turbine that suppresses a rapid increase in load
applied on the leading edge of the blade, and that can reduce
incidence loss.
[0009]
In order to solve the above problems, the present
invention employs following solutions.
That is to say, the present invention provides a mixed
flow turbine or a radial turbine comprising; a hub, and a
plurality of blades provided on an outer circumference surface
of the hub at substantially equal intervals, the camber line
of the blade section being convex-curved to the rotational
direction side as seen entirely from a leading edge side
toward trailing edge side, wherein on a leading edge section
of the blade, there is provided an inflected section that is
inflected so that a camber line in a sectional surface along

6
the outer circumference surface is concave-curved to the
rotational direction side.
[0010]
As described above, on the leading edge of the blade,
there is provided the inflected section that is inflected so
that the camber line in the section surface along the outer
circumference surface of the hub is concave-curved to the
rotational direction side. As a result, in the inflected
section, the rate of change of the blade angle in the
rotational direction becomes greater as the radial direction
position becomes smaller, that is to say, it has a rate of
change toward the rotational direction.
Therefore, in the case where the blade angle of the
leading edge is aligned with the relative flow angle (that is
to say, in the case where the leading edge is matched with the
trajectory of the relative flow velocity), the blade angle in
the inflected section changes to substantially follow the
changes in the relative flow velocity. As a result, the
distance between the blade surface and the relative flow
velocity can be made small, and a rapid increase can be
suppressed.
Therefore, a rapid increase in the load on the blade at
the leading edge section can be prevented so that occurrence
of leak flow from the pressure surface side to the suction

7
surface side due to this load can be suppressed, and incidence
loss can be reduced.
[0011]
Furthermore, in the above invention, it is preferable
that, on a leading edge section when the blade is projected
onto a cylindrical surface, there be provided an inflected
section that is inflected so that the camber line is concave-
curved to the rotational direction side.
[0012]
Moreover, in the above invention, it is preferable that,
at least on an upstream side outer surface and/or on a
downstream side outer surface in the rotational direction of
the inflected section, there be provided a thickened section
that smoothly increases the blade thickness from the leading
edge.
[0013]
As described above, on at least the upstream side outer
surface and/or the downstream side outer surface in the
rotational direction of the inflected section there is
provided the thickened section that smoothly increases the
blade thickness from the leading edge. As a result, tangent
line angles formed by the tangent lines at the ends on the
upstream side and the downstream side of the leading edge
become greater.

8
In the case where the tangent line angle of the leading
edge becomes greater, and the blade thickness increases
smoothly, even if the inflow angle of the working fluid is
significantly different from the angle of the camber line, the
working fluid can be moved along the outer surface, so that
separation of the working fluid on the leading edge can be
prevented. Therefore, collision loss can be suppressed and
incidence loss can be reduced.
Accordingly, incidence loss with respect to a wide range
of theoretical velocity ratios (U/CO) can be reduced.
It is preferable that the thickened section be smoothly
decreased after the smooth increase so that the working fluid
can flow smoothly and can be prevented from separating after
the smooth increase.
[0014]
Moreover, in the above invention, it is preferable that
the inflected section be configured so that a curvature of the
camber line becomes smaller as it gets closer to an outer
diameter side from the hub side.
[0015]
The rate of change of the relative flow velocity W toward
the rotational direction becomes greater as the radial
direction position becomes smaller, that is to say, since it
has a rate of change toward the rotational direction, the
smaller the radial direction position becomes, that is to say,

9
the closer to the hub side, the greater the rate of change
becomes.
According to the present invention, the inflected section
is configured such that the curvature of the camber line
becomes smaller closer to the outer diameter side from the hub
side. As a result, the load applied on the blade surface can
be significantly reduced on the hub side, where the load is
significant, while the load reduction rate gradually decreases
toward the outer diameter side, where the load is smaller.
Therefore, the load Fr in the height direction of the
blade can be made substantially uniform, and an incidence loss
increase due to unbalanced load can be suppressed.
As a result, incidence loss can be reduced across the
entire region in the height direction of the blade.
[0016]
According to the present invention, on the leading edge
of the blade there is provided the inflected section that is
inflected so that the camber line on the section surface along
the outer circumference surface of the hub is concave-curved
to the rotational direction side. Therefore a rapid increase
in load applied to the blade at the leading edge section can
be prevented.
The occurrence of a leak flow from the pressure surface
side to the suction surface side due to this load can be
suppressed, and incidence loss can be reduced.

10
Brief Description of Drawings
[0017]
FIG. 1 shows a blade portion of a mixed flow turbine
according to a first embodiment of the present invention,
wherein (a) is a partial sectional view showing a meridional
plane sectional surface, and (b) is a partial sectional view
showing a sectional surface of the blade cut along an outer
circumference surface of a hub.
FIG. 2 is a developed partial projection view of the
outer circumference surface of the hub according to the first
embodiment of the present invention, projected onto a
cylindrical surface.
FIG. 3 is a graph showing states of a flow field in a
mixed flow turbine or the like.
FIG. 4 is a graph showing variation in relative direction
flow velocity in FIG. 3.
FIG. 5 is a schematic drawing showing a trajectory of
changes in relative flow velocity W in the states in FIG. 3.
FIG. 6 is a graph showing relative flow velocity and
states of load applied on the blade.
FIG. 7 is a graph showing the relationship between
relative flow angle and blade angle.
FIG. 8 shows a blade portion of a radial turbine
according to another embodiment of the first embodiment of the

11
present invention, wherein (a) is a partial sectional view
showing a meridional plane sectional surface, and (b) is a
partial sectional view showing a sectional surface of the
blade cut along an outer circumference surface of a hub.
FIG. 9 is a partial sectional view showing a blade of a
mixed flow turbine according to a second embodiment of the
present invention, cut along an outer circumference surface of
the hub.
FIG. 10 is a graph showing changes in the curvature
radius of the inflected section in the height direction of a
blade of a mixed flow turbine according to a third embodiment
of the present invention.
FIG. 11 shows a blade portion of a mixed flow turbine
according to the third embodiment of the present invention,
wherein (a) is a partial sectional view showing a meridional
plane sectional surface, and (b) through (d) are partial
sectional views showing a sectional surface of the blade cut
along an outer circumference surface of a hub, (b) showing a
height position 0.2H, (c) showing a height position 0.5H, and
(d) showing a height position 0.8H.
FIG. 12 is a graph showing a relationship between the
relative flow angle and the blade angle of a mixed flow
turbine according to the third embodiment of the present
invention.

12
FIG. 13 shows a blade portion of a conventional mixed
flow turbine, wherein (a) is a partial sectional view showing
a meridional plane sectional surface, and (b) is a partial
sectional view showing a sectional surface of the blade cut
along an outer circumference surface of a hub.
Explanation of Reference Signs:
[0018]
1 Mixed flow turbine
2 Radial turbine
3 Hub
5 Outer circumference surface
7 Blade
9 Leading edge
11 Trailing edge
17 Rotational direction
19 Pressure surface
21 Suction surface
23 Camber line
25 Suction surface thickened section
27 Pressure surface thickened section
K Inflected section
Best Mode for Carrying Out the Invention
[0019]

13
Hereinafter, embodiments according to the present
invention are described, with reference to the drawings.
[First Embodiment]
Hereinafter, a mixed flow turbine 1 according to a first
embodiment of the present invention is described, with
reference to FIG. 1 through FIG. 7. This mixed flow turbine 1
is used in a turbocharger (turbocharger) for a diesel engine
in a motor vehicle.
FIG. 1 shows a blade portion of the mixed flow turbine 1
of the present embodiment, wherein (a) is a partial sectional
view showing a meridional plane sectional surface, and (b) is
a partial sectional view showing a sectional surface of the
blade cut along an outer circumference surface of a hub. FIG.
2 is a spread partial projection drawing of the outer
circumference surface of the hub projected on a cylindrical
surface.
[0020]
The mixed flow turbine 1 is provided with; a hub 3, a
plurality of blades 7 provided at substantially equal
intervals on an outer circumference surface 5 of the hub 3 in
its circumferential direction, and a casing (not shown in the
drawing).
The hub 3 is configured such that it is connected to a
turbocompressor (not shown in the drawing) by a shaft, and a
rotational driving force of the hub 3 rotates the

14
turbocompressor to compress air and supply it to a diesel
engine.
The outer circumference surface 5 of the hub 3 is of
shape that smoothly connects a large diameter section 2 on one
end side and a small diameter section 4 on the other end side,
with a curved surface that is concaved toward the axial center.
[0021]
The blade 7 is a plate shaped member and is provided in a
standing condition on the outer circumference surface 5 of the
hub so that a surface section of the blade 7 extends in the
axial direction.
The hub 3 and the blade 7 are integrally formed by means
of casting or machining. The hub 3 and the blade 7 may be
separate bodies firmly fixed by means of welding or the like.
The blade 7 is configured such that in the region in
which it rotates, combustion exhaust gas, which serves as a
working fluid, is relatively introduced from the outer
circumference on the large diameter section 2 side in roughly
the radial direction.
[0022]
The blade 7 has: a leading edge 9 positioned on the
upstream side in the combustion exhaust gas flow direction; a
trailing edge 11 positioned on the downstream side; an outside
edge 13 positioned on the radial direction outside; an inside
edge 15 positioned on the radial direction inside and

15
connected to the hub 3; a pressure surface (upstream side
outer surface) 19, which is a surface on the upstream side in
the rotational direction 17; and a suction surface (downstream
side outer surface) 21, which is a surface on the downstream
side in the rotational direction 17.
An intersecting point C of the leading edge 9 and the
outside edge 13 is positioned to the outside in the radial
direction, of an intersecting point B of the hub 3 and the
leading edge 9.
[0023]
When seen on a cross-section D along the outer
circumference surface 5, the blade 7 has a main body section T
in which a camber line 23, which is a center line of the blade
thickness, convex-curves in the rotational direction 17 (the
center of a curvature radius R2 is positioned on the pressure
surface 19 side), and an inflected section K in which the
camber line 23 concave-curves in the rotational direction 17
(the center of a curvature radius Rl is positioned on the
suction surface 21 side), on either side of an inflection
point A.
In other words, for example, as shown in FIG. 2, the
inside edge 15 of the blade 7 (section D along the outer
circumference surface 5) is of elongated S shape when seen
from the radial direction.
[0024]

16
Since the section surface D follows the outer
circumference surface 5, it follows the flow direction of the
combustion exhaust gas, and the height in the radial direction
gradually becomes lower.
Therefore, in the inflected section K, the rate of change
toward the rotational direction becomes greater as the radial
direction position becomes smaller, in other words, the
inflected section K has a rate of change in the rotational
direction.
The curvature centers Rl and R2 may respectively exist in
a plurality of locations.
[0025]
Operation of the mixed flow turbine 1 according to the
above described present embodiment is described.
Combustion exhaust gas is introduced in a substantially
radial direction from the outer circumference side of the
leading edge 9 and travels between the blades 7 to be
discharged through the trailing edge 11. At this time, the
combustion exhaust gas pushes the pressure surface of the
blade 7 to move the blade 7 in the rotational direction 17.
As a result, the hub 3 integrated with the blade 7
rotates in the rotational direction 17. The rotational force
of the hub 3 rotates the turbocompressor. The turbocompressor
compresses air and supplies the compressed air to the diesel
engine.

17
[0026]
At this time, the combustion exhaust gas is basically
formed as a free vortex. Therefore, for example, the absolute
circumferential direction velocity Cu is such that, with
respect to a radial direction position (distance from the
axial center) HO, Cu/HO is constant, in other words, there is
an inversely proportional relationship between them.
On the other hand, the peripheral velocity U of the blade
7 is proportional to the radial direction position HO. As a
result, a relative circumferential flow velocity Wu occurs
between the flow of the combustion exhaust gas and the blade 7.
Plotting the relative circumferential flow velocity Wu
against the radial position yields a curved line that is
convex-curved downward (convex curved in the counter-
rotational direction) as shown in FIG. 4. In other words, the
rate of change toward the rotational direction 17 becomes
greater as the radial direction position HO becomes smaller,
that is to say, there is a rate of change toward the
rotational direction 17.
[0027]
FIG 5 schematically shows the changing trajectory of the
relative flow velocity W at this time. The relative flow
velocity W is a synthesis of the relative circumferential flow
velocity Wu that changes according to FIG. 4, and the
substantially constant relative radial velocity Wr. The

18
change in the size of the relative flow velocity W have a
trend similar to that of the relative circumferential flow
velocity Wu shown in FIG. 4, in other words, it has a trend
such that the rate of change toward the rotational direction
17 becomes greater as the radial direction position HO becomes
smaller (refer to FIG. 6).
The angle formed between the relative flow velocity W and
the relative circumferential flow velocity Wu is a relative
flow angle 3 at that radial position.
[0028]
FIG. 6 shows the relative flow velocity W and states of
the load on the blade 7. FIG. 7 shows a relationship between
the relative flow angle (3 and the blade angle a.
In the present embodiment, the blade angle a in the
leading edge 9 is aligned with the relative flow angle |3 in
the radial direction position HO of the leading edge 9. As a
result, in the radial direction position HO, the leading edge
9 matches the relative flow velocity W in FIG. 6 and matches
the relative angle £ in FIG. 7.
In the present embodiment, since the inflected section K,
in which the rate of change toward the rotational direction 17
becomes greater as the radial direction position HO becomes
smaller, is provided on the leading edge 9 side of the blade 7,
the shape of the region between the leading edge 9 and the
inflected section K changes substantially along the trajectory

19
of the relative flow velocity W, the rate of change of which
toward the rotational direction 17 becomes greater as the
radial direction position HO becomes smaller.
[0029]
The distance between the trajectory of the relative flow
velocity W and the blade 7 in FIG. 6 equates to a load Fr on
the blade 7. This load Fr is significantly reduced compared
to a load Fc in the case of a conventional blade 101 not
having the inflected section K.
As described above, since there is provided the inflected
section K, where the rate of change toward the rotational
direction 17 becomes greater as the radial direction position
HO becomes smaller, the distance between the trajectory of the
relative flow velocity W and the blade 7 can be made small and
a rapid rise in the load Fr can be suppressed.
Accordingly, a rapid increase in the load Fr on the blade
7 in the leading edge 9 can be prevented, so that the
occurrence of a leak flow from the pressure surface 19 side to
the suction surface 21 side can be suppressed and incidence
loss can be reduced.
At this time, if the curvature radius Rl of the inflected
section K is set to follow the trajectory of the relative flow
velocity W, incidence loss can be further reduced.
[0030]

20
The blade angle a of the inflected section K becomes
greater as the radial direction position HO becomes smaller.
On the other hand, the relative flow angle (3 also becomes
greater as the radial direction position HO becomes smaller.
Therefore, compared to the conventional blade 101 in
which the blade angle a in the leading edge section becomes
smaller as the radial direction position HO becomes smaller,
the blade angle a of the blade 7 changes to follow the
trajectory of the relative flow angle [3.
Since the difference between the relative flow angle (3
and the blade angle a in the radial direction position HO
equates to the load Fr, this load Fr is significantly reduced
compared to the load Fc in the case of the conventional blade
101, which does not have the inflected section K.
As described above, the situation in which the
abovementioned effects are provided, can also be explained
from the relationship between the relative flow angle (3 and
the blade angle a.
[0031]
In the present embodiment, the present invention is
described in application to a mixed flow turbine 1, however it
can also be applied to a radial turbine 2 as shown in FIG. 8.
[0032]
[Second Embodiment]

21
Next, a second embodiment of the present invention is
described, with reference to FIG. 9.
FIG. 9 is a partial sectional view of the blade 7 of a
mixed flow turbine 1 cut on a section D along the outer
circumference surface of the hub 3.
The mixed flow turbine 1 in the present embodiment
differs from the one in the first embodiment in the
configuration of the leading edge 9 section of the blade 7.
Other constituents are the same as in the first embodiment
mentioned above, and repeated descriptions of these are
therefore omitted here.
The same reference symbols are given to members that are
the same as in the first embodiment.
[0033]
In the present embodiment, a suction surface thickened
section 25 is provided on the suction surface 21 side of the
leading edge 9 portion, and a pressure surface thickened
section 27 is provided on the pressure surface 19 side. That
is to say, the blade thickness of the leading edge 9 section
is increased.
In FIG. 9, the suction surface thickened section 25 and
the pressure surface thickened section 27, are shown as
portions of increased blade thickness on the blade 7 of the
first embodiment, however they are not separate bodies from
the blade 7.

22
The suction surface thickened section 25 and the pressure
surface thickened section 27 are configured so as to
respectively gradually increase from the leading edge 9 toward
the downstream side and then to gradually decrease.
[0034]
A tangent line 29 on the suction surface 21 side end
section in the leading edge 9 intersects with a tangent line
31 on the pressure surface 19 side end section. The angle in
this intersecting portion is referred to as a tangent line
angle 6.
This tangent line angle 9 is formed as a wide angle since
the suction surface thickened section 25 and the pressure
surface thickened section 27 are gradually increased.
[0035]
For example, the temperature and pressure of the
combustion exhaust gas change according to operating
conditions of a motor vehicle. When the temperature and
pressure of the combustion exhaust gas change, the theoretical
velocity ratio U/CO changes. As a result, the relative flow
angle [3 of the combustion exhaust gas flowing to the leading
edge 9 changes.
For example, a low U/CO flow 33, the temperature and
pressure of which are high and the theoretical velocity ratio
U/CO of which is low, tends to flow in from the upstream side
of the rotational direction 17, while a high U/CO flow 35, the

23
temperature and pressure of which are low and the theoretical
velocity ratio U/CO is high, tends to flow in from the
downstream side of the rotational direction 17.
[0036]
In the case where a low U/CO flow 33 such as is shown in
FIG. 9, in which the relative flow angle (3 differs
significantly from the blade angle a in the leading edge 9 of
the camber line 23, flows in, with the conventional blade,
there is a possibility of separation at the load pressure
surface 21 side end section of the leading edge 9.
In the present embodiment, since an outer surface of the
suction surface thickened section 25 has an angle greater than
this relative flow angle 0, this combustion exhaust gas can be
made to travel along the outer surface of the suction surface
thickened section 25 toward the flow direction downstream side.
Moreover, the suction surface thickened section 25 is
such that the blade thickness gradually increases and then
gradually decreases. As a result, combustion exhaust gas does
not separate. Accordingly, the occurrence of collision loss
due to collision of the combustion exhaust gas can be
suppressed, and the incidence loss can be therefore reduced.
[0037]
On the other hand, in the case where a high U/CO flow 35
with a relative flow angle β that differs significantly from
the blade angle a in the leading edge 9 of the camber line 23

24
shown in FIG. 9 flows in, with a conventional blade there is a
possibility that it will separate at the pressure surface 19
side end section of the leading edge 9.
In the present embodiment, since an outer surface of the
pressure surface thickened section 27 has an angle greater
than this relative flow angle p, this combustion exhaust gas
can be made to travel along the outer surface of the pressure
surface thickened section 27 toward the flow direction
downstream side.
Moreover, the pressure surface thickened section 27 is
such that the blade thickness gradually increases and then
gradually decreases. As a result, combustion exhaust gas does
not separate. Accordingly, the occurrence of collision loss
due to collision of the combustion exhaust gas can be
suppressed, and incidence loss can be therefore reduced.
[0038]
As described above, since the suction surface thickened
section 25 and the pressure surface thickened section 27 are
provided, even if the combustion exhaust has a relative flow
angle β that is significantly different from the blade angle a
in the camber line 23 in the leading edge 9, collision loss
can be suppressed and incidence loss with respect to a wide
range theoretical velocity ratio (U/CO) can therefore be
reduced.

25
The suction surface thickened section 25 and the pressure
surface thickened section 27 need only cover the range of
changes of states of the combustion exhaust gas. Therefore,
if this change range is narrow, either one of them may be
provided alone, or the size of the tangent line angle 9 may be
made smaller.
[0039]
In the present embodiment, the present invention is
described in application to the mixed flow turbine 1. However
it can also be applied to a radial turbine.
[0040]
[Third Embodiment]
Next, a third embodiment of the present invention is
described, with reference to FIG. 10 to FIG. 12.
FIG. 10 is a graph showing changes in the curvature
radius Rl of the inflected section K in the height direction
of the blade 7. FIG. 11 shows a blade portion of a mixed flow
turbine of the present embodiment, wherein (a) is a partial
sectional view showing a meridional plane sectional surface,
and (b) through (d) are partial sectional views showing a
sectional surface of the blade 7 cut along an outer
circumference surface of a hub 3, (b) showing a height
position 0.2H, (c) showing a height position 0.5H, and (d)
showing a height position 0.8H. FIG. 12 shows a relationship
between the relative flow angle β and the blade angle a.

26
The mixed flow turbine 1 in the present embodiment
differs from the one in the first embodiment in the
configuration of the leading edge 9 section of the blade 7.
Other constituents are the same as in the first embodiment
mentioned above, and repeated descriptions of these are
therefore omitted here.
The same reference symbols are given to members that are
the same as in the first embodiment.
[0041]
The present embodiment is configured such that, the
curvature radius R1 of the camber line 23 in the inflected
section K becomes greater, in other words the curvature
becomes smaller, toward the outside edge 13 side (external
diameter side) from the hub 3 side in the height direction of
the blade 7 as shown in FIG. 10.
In the leading edge 9, the blade angle a thereof is
matched with the relative flow angle P in the radial direction
position thereof.
[0042]
The blade angle α of the blade 7 changes to correspond to
the trajectory of the relative flow angle p.
Since the difference between the relative flow angle β
and the blade angle a in the radial direction position HO
equates to the load Fr, this load Fr is significantly reduced

27
compared to the load Fc in the case of the conventional blade
101, which does not have the inflected section K.
[0043]
The blade angle a of the inflected section K becomes
greater as the radial direction position HO becomes smaller.
The ratio by which this blade angle becomes greater gets
higher for a smaller curvature radius (greater curvature).
Changes in the blade angle α of a smaller curvature radius
(greater curvature) approach more closely to the trajectory of
the relative flow angle β compared to changes of the blade
angle a of a greater curvature radius (smaller curvature).
In other words, the inflected section K on the hub 3 side
gets more significantly closer to the trajectory of the
relative flow angle β than the inflected section K on the
outside edge 13 side.
As shown in FIG. 10, this change occurs gradually and
smoothly from the hub 3 side toward the outside edge 13 side.
[0044]
On the other hand, the rate of change toward the
rotational direction, of the relative flow velocity W becomes
greater as the radial direction position becomes smaller.
That is to say, because the relative flow angle β becomes
greater, the radial direction position becomes smaller. That
is to say, the relative flow angle β becomes greater the
closer it is to the hub 3.

28
Therefore, the change in the blade angle α becomes more
significantly close to the trajectory of the relative flow
angle β on the hub 3 side where there is a greater relative
flow angle β. As a result, the load on the blade surface can
be reduced on the hub 3 side where the load is significant.
Meanwhile, the load decrease rate gradually decreases toward
the outside edge 13 side where load gradually decreases.
Therefore, the load Fr in the height direction of the
blade 7 can be made substantially uniform. As a result, an
incidence loss increase due to unbalanced load Fr can be
suppressed.
Therefore, incidence loss can be reduced across the
entire region in the height direction of the blade.
[0045]
In the present embodiment, the present invention is
described in application to the mixed flow turbine 1. However
it can also be applied to a radial turbine.
Furthermore, the configuration of the present embodiment
and the configuration of the second embodiment may be provided
together.

29
CLAIMS
1. A mixed flow turbine or a radial turbine comprising;
a hub, and
a plurality of blades provided on an outer circumference
surface of the hub at substantially equal intervals, a camber
line of the blade section being convex-curved to the
rotational direction side as seen entirely from a leading edge
side toward trailing edge side,
wherein on a leading edge section of said blade, there is
provided an inflected section that is inflected so that a
camber line in a sectional surface along said outer
circumference surface is concave-curved to said rotational
direction side.
2. A mixed flow turbine or a radial turbine according to
claim 1, wherein on a leading edge section when said blade is
projected onto a cylindrical surface, there is provided an
inflected section that is inflected so that the camber line is
concave-curved to said rotational direction side.
3. A mixed flow turbine or a radial turbine according to
claim 1 or claim 2, wherein at least on an upstream side outer
surface and/or on a downstream side outer surface in said
rotational direction of said inflected section, there is

30
provided a thickened section that smoothly increases the blade
thickness from said leading edge.
4. A mixed flow turbine or a radial turbine according to any
one of claim 1 through claim 3, wherein said inflected section
is configured so that a curvature of said camber line becomes
smaller as it gets closer to an outer diameter side from said
hub side.

An object is to provide a mixed flow turbine or a radial
turbine that suppresses a rapid increase in load applied on a
leading edge of a blade, and that can reduce incidence loss.
There is provided a mixed flow turbine or a radial turbine
including; a hub, and a plurality of blades provided on an
outer circumference surface of the hub at substantially equal
intervals, the camber line of the blade section being convex-curved to the rotational direction side as seen entirely from
a leading edge side toward trailing edge side, wherein on a
leading edge section of the blade, there is provided an
inflected section that is inflected so that a camber line in a
sectional surface along the outer circumference surface is
concave-curved to the rotational direction side.