Fluid reaction surfaces (i.e. – impellers) – With heating – cooling or thermal insulation means – Changing state mass within or fluid flow through working...
Reexamination Certificate
1999-03-19
2001-09-18
Ryznic, John E. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
With heating, cooling or thermal insulation means
Changing state mass within or fluid flow through working...
Reexamination Certificate
active
06290462
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a gas turbine cooled blade and more specifically to a gas turbine cooled blade having a seal air supply passage for supplying therethrough a seal air from an outer peripheral side to an inner peripheral side of a stationary blade. The present invention also relates to a gas turbine cooled blade having a structure for enhancing a heat transfer rate in a cooling passage of a moving blade or a stationary blade.
2. Description of the Prior Art
Examples of the above-mentioned type gas turbine cooled stationary blade in the prior art will be described with reference to
FIGS. 7 and 8
.
FIG. 7
is a schematic cross sectional view of one example of a prior art gas turbine cooled blade, wherein FIG.
7
(
a
) is a longitudinal cross sectional view and FIG.
7
(
b
) is a cross sectional view taken on line III-III of FIG.
7
(
a
).
FIG. 8
is a schematic cross sectional view of another example of a prior art gas turbine cooled blade, wherein FIG.
8
(
a
) is a longitudinal cross sectional view and FIG.
8
(
b
) is a cross sectional view taken on line IV-IV of FIG.
8
(
a
).
In an actual unit of the gas turbine, the number of stages is decided by the capacity of the turbines. For example, in a gas turbine constructed in four stages, its second, third and fourth stage stationary blades, respectively, have moving blades disposed in front and back thereof and each of the stationary blades is structured to be surrounded by adjacent moving blades and rotor discs supporting them. Hence, it is important that a main flow high temperature gas does not flow into a gap of each portion in an interior of the stationary blade, in which the gap is formed there during manufacture, assembly, etc.
As a countermeasure therefor, a construction is usually employed so that a bleed air from a compressor flows into the interior of the stationary blade from its outer peripheral side to be supplied into a cavity portion on an inner peripheral side of the stationary blade as a seal air. Thus, a pressure in the cavity portion is kept higher than that in a main flow high temperature gas path, thereby preventing inflow of the main flow high temperature gas.
The prior art example of
FIG. 7
is of a seal air supply structure using a seal tube
4
for leading therethrough a seal air. The seal tube
4
is provided in a stationary blade at a position apart from an inner surface of a blade portion
5
to pass through a first row cooling passage A of a leading edge portion in the blade portion
5
. Thus, a blade outer peripheral side communicates with a-cavity portion of a blade inner peripheral side so that a seal air
3
is supplied into the cavity portion through the seal tube
4
.
Numeral
2
designates a cooling medium, which is supplied for cooling of the stationary blade to flow through the first row cooling passage A and further through a second row cooling passage B and a third row cooling passage C in the blade portion
5
. The cooling medium is then discharged into the main flow high temperature gas from a blade trailing edge portion.
Also, another example in the prior art shown in
FIG. 8
is constructed such that a sealing air
3
is supplied directly into a first row cooling passage A to be used both for a sealing air and a blade cooling air, wherein a seal tube such as used in the example of
FIG. 7
is not used.
In the moving blade and stationary blade of a conventional gas turbine including those blades shown in
FIGS. 7 and 8
, there are provided cooling passages so that cooling medium is led to pass therethrough for cooling of the interior of the blade. By such cooling, gas turbine portions to be exposed to the main flow high temperature gas flowing outside thereof are cooled so that the strength of these gas turbine portions is maintained so as not to be deteriorated by the high temperature.
FIG. 9
is a longitudinal cross sectional view of the conventional gas turbine cooled blade. In
FIG. 9
, numeral
21
designates a-cooled blade (moving- blade), in which a cooling passage
22
is provided passing therethrough. Numeral
23
designates a cooling medium, which flows into the blade from a base portion of the cooled blade
21
to flow through cooling passages
22
a
,
22
b
and
22
c
sequentially and is discharged into a gas path where a high temperature gas
25
flows. A plurality of ribs
24
are arranged inclinedly on inner walls of the cooling passages
22
a
,
22
b
,
22
c
, as described later, so that the cooling medium
23
flows in each of the cooling passages as shown by arrow
29
with a heat transfer rate therein being enhanced.
FIG. 10
is an enlarged view of one of the cooling passages of the cooled blade
21
in the prior art as described above, wherein FIG.
10
(
a
) is a plan view thereof and FIG.
10
(
b
) is a perspective view thereof. As shown there, in the cooling passage
22
of the cooled blade
21
, the plurality of ribs
24
are provided, each extending in an entire width W of the cooling passage
22
to be disposed at an incline with a constant angle
0
relative to a flow direction of the cooling medium
23
with a rib to rib pitch P and projecting a height e. The cooling medium
23
is led into the cooling passage
22
from outside of the cooled blade
21
to flow through the cooled blade
21
for sequential cooling therein and is discharged into the high temperature gas
25
, as described in FIG.
9
. At this time, the rib
24
causes turbulences in the flow of the cooling medium
23
so that the heat transfer-rate of the cooling medium
23
flowing through the cooling passage
22
is enhanced.
FIG. 11
is a schematic explanatory view of a flow pattern and a cooling function thereof of the cooling medium
23
flowing in the cooling passage
22
of
FIG. 10
, wherein FIG.
11
(
a
) shows a flow direction of the cooling medium
23
seen on a plan view of the cooling passage
22
, FIG.
11
(
b
) shows a flow of the cooling medium
23
seen from one side of FIG.
11
(
a
),
FIG. 11
(
c
) shows the flow of the cooling medium
23
seen perspectively and FIG.
11
(
d
) shows a heat transfer rate distribution in the cooling passage
22
.
As shown there, in a space between each of the ribs
24
, the cooling medium
23
becomes a swirl flow
23
a
as in FIG.
11
(
a
) to flow downstream from upstream there so as to move in a constant direction along the rib
24
inclined as in FIG.
11
(
c
). For this reason, as shown conceptually by the heat transfer rate distribution of FIG.
11
(
d
), there is generated a high heat transfer rate area
30
on an upstream side thereof where the swirl flow
23
a
approaches a wall surface of the cooling passage
22
(boundary layer there is thin) . On the other hand, on a downstream side thereof where the swirl flow
23
a
leaves the wall surface of the cooling passage
22
(boundary layer there is thick), the heat transfer rate tends to lower as compared with the upstream side. As a result, there occurs a non-uniformity of the heat transfer rate according to the place, which results in suppressing enhancement of an average heat transfer rate as a whole.
In the first prior art example shown in
FIG. 7
, there is provided the seal tube
4
which is disposed at the position apart from the inner surface of the blade portion
5
for exclusively leading therethrough the seal air
3
. Hence, in this system, while there is an advantage that the seal air
3
, making no direct contact with the inner surface of the blade portion
5
, can be supplied as the seal air before it is heated by heat exchange, there is also a disadvantage of inviting an increased number of parts and increased time in providing the seal tube
4
.
Also, in the second prior art example shown in
FIG. 8
, while no such seal tube as the seal tube
4
is used and reduction of the parts and time can be realized, the seal air
3
is supplied passing through the blade leading edge portion where there is a large thermal load. Hence, there is needed a large heat exchange rate for cooling of the blade
Ishiguro Tatsuo
Masada Junichiro
Matsuura Masaaki
Suenaga Kiyoshi
Takeishi Kenichiro
Mitsubishi Heavy Industries Ltd.
Ryznic John E.
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Gas turbine cooled blade does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Gas turbine cooled blade, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gas turbine cooled blade will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2449515