U.S. patent number 3,899,267 [Application Number 05/355,150] was granted by the patent office on 1975-08-12 for turbomachinery blade tip cap configuration.
This patent grant is currently assigned to General Electric Company. Invention is credited to Robert J. Corsmeier, Ronald E. Dennis, William D. Treece.
United States Patent |
3,899,267 |
Dennis , et al. |
August 12, 1975 |
Turbomachinery blade tip cap configuration
Abstract
An improved tip cap configuration for a turbomachinery blade
includes tip cap seats formed integrally with and located on the
inner sides of a hollow turbomachinery blade. Tip cap retaining
members are also formed integrally with the inner wall of the blade
and are spaced a short radial distance from the tip cap seats. The
blade is initially provided with a flared open end and the tip caps
are positioned on the seats and the flared end is crimped so as to
capture the tip cap between the seats and the retaining members.
The crimping operation is stopped at a point wherein a smooth outer
contour is obtained for the blade in the region of the tip cap. A
method of making such a blade is also disclosed.
Inventors: |
Dennis; Ronald E. (Cincinnati,
OH), Treece; William D. (Forest Park, OH), Corsmeier;
Robert J. (Cincinnati, OH) |
Assignee: |
General Electric Company
(Cincinnati, OH)
|
Family
ID: |
23396414 |
Appl.
No.: |
05/355,150 |
Filed: |
April 27, 1973 |
Current U.S.
Class: |
416/92; 416/96R;
416/232; 416/228 |
Current CPC
Class: |
B23P
15/04 (20130101); F01D 5/20 (20130101) |
Current International
Class: |
B23P
15/04 (20060101); F01D 5/14 (20060101); F01D
5/20 (20060101); F01d 005/08 () |
Field of
Search: |
;416/92,95,96,97,232,228 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
2213940 |
September 1940 |
Jendrassik |
3626568 |
December 1971 |
Silvertein et al. |
3628885 |
October 1969 |
Sidenstick et al. |
3635587 |
January 1972 |
Giesman et al. |
3732031 |
May 1973 |
Bowling et al. |
3761201 |
September 1973 |
Silvertein et al. |
|
Foreign Patent Documents
Primary Examiner: Powell, Jr.; Everette A.
Attorney, Agent or Firm: Bigelow; Dana F. Lawrence; Derek
P.
Claims
What is claimed is:
1. In a turbomachinery blade of the type comprising an
airfoil-shaped, hollow body portion having a pair of side walls
defining an internal cavity therebetween, and an airfoil-shaped tip
cap defining the outer bounds of said internal cavity, the
improvement comprising:
each of said side walls includes a tip cap seat formed integrally
therewith on the inner side thereof and at least one tip cap
retaining member formed integrally therewith on the inner side
thereof and radially spaced from said seat so as to be capable of
capturing said tip cap between said seats and said retaining
members such that said tip cap is mechanically secured to said
blade.
2. The improved turbomachinery blade of claim 1 further
characterized in that said hollow body portion has a smooth
radially extending outer contour in the region of said tip cap.
3. The improved turbomachinery blade of claim 1 further
characterized in that said tip cap has a generally U-shaped cross
section including a bight portion and a pair of leg members and
each of said leg members is sized so as to fit between said seat
and one of said retaining members.
4. The improved turbomachinery blade of claim 3 further
characterized in that said bight portion is provided with a
plurality of coolant holes.
5. The improved turbomachinery blade of claim 4 further
characterized in that said holes are spaced around the
circumference of said tip cap.
6. The improved turbomachinery blade of claim 5 further
characterized in that said holes are angled so as to direct coolant
toward said retaining members and said side walls.
7. The improved turbomachinery blade of claim 4 further
characterized in that said holes are angled so as to direct coolant
toward said retaining members and said side walls.
8. The improved turbomachinery blade of claim 3 further
characterized in that said hollow body portion has a smooth outer
contour from a point below the region of said tip cap to the outer
end of said hollow body portion.
Description
BACKGROUND OF THE INVENTION
This invention relates primarily to tubomachinery blading and, more
particularly, to an improved tip cap configuration for a hollow
turbomachinery blade and a method of making such a
configuration.
The invention herein described was made in the course of or under a
contract, or a subcontract thereunder, with the United States
Department of the Air Force.
It is well known that significant increases in gas turbine engine
performance, in terms of thrust of work output per unit of fluid
input, can be obtained by increasing the turbine inlet temperature
of the motive fluid or hot gas stream flowing through the engine.
It is also recognized that one major limitation on turbine inlet
temperature is that which is imposed by the turbine blade
temperature capability. In an effort to extend turbine blade
capabilities, numerous complex turbomachinery blade structures have
been proposed which employ one or more modes of cooling using fluid
extracted from the gas turbine engine compressor.
One such mode of cooling which is becoming prevalent is the
provision of impingement inserts within an internal cavity defined
by a hollow body portion of the turbomachinery blade. Coolant is
delivered to the interior of such an insert and is expelled through
a multiplicity of small holes against an internal wall of the
turbomachinery blade, thereby cooling that portion of the
turbomachinery blade which is exposed to the hot gas stream.
In order to permit insertion of the impingement inserts into the
interior of the turbomachinery blade, many such blades are provided
with open tip ends. As is known to those skilled in the art, in
order to maximize turbine efficiency, it becomes necessary to
minimize the amount of cooling air which is expended in cooling
each component. For this reason, it has become necessary to seal
the tip ends of the blades in order to prevent cooling fluid from
being wastefully discharged into the gas stream. In many prior art
designs, the open tip end of the blade is sealed by means of a tip
cap which is joined to the blade in a suitable manner. While a
number of alternative methods have been proposed in the past for
joining the tip cap to the blade, none of these methods has proven
universally acceptable for numerous reasons. When one considers
that these tip caps must operate in an environment where they are
subjected to centrifugal forces on the order of 100,000 times the
normal gravitational force and metal temperatures in excess of
1500.degree.F, it becomes easy to envision why no single method of
joining the tip cap to the blade has proven universally
acceptable.
When one further considers the fact that the tip cap is inserted in
an airfoil-shaped blade and that any distortion in the shape of the
airfoil at its tip end can greatly reduce the aerodynamic
efficiency of the blade, the problems of joining the tip cap to the
blade increase. The problems are even further complicated when
cooling requirements for that portion of the blade tip which
extends above the tip cap are considered.
SUMMARY OF THE INVENTION
It is an object of this invention, therefore, to provide a
turbomachinery blade tip cap configuration which overcomes the
problems of the prior art configurations. It is a further object of
this invention to provide such a tip cap configuration which is
mechanically secured by the blade member and which provides an
airfoil-shaped tip which is free from distortion and which is
capable of being cooled by coolant from the interior of the blade.
Another object of this invention is to provide a new method for
making a turbomachinery blade which includes the inventive tip cap
configuration.
Briefly stated, the above and similarly related objects are
attained in the present instance by providing a hollow
turbomachinery blade which is initially formed with a flared, open
tip end. The flared, open end is provided with tip cap seats which
are formed integrally with and located along the inner walls of the
hollow blade member. Tip cap retainers are also formed integrally
with the inner walls of the hollow blade member and are spaced a
short distance from the tip cap seat. The tip cap, which may have a
generally U-shaped cross section, is inserted into the flared, open
end and is positioned upon the tip cap seats. The flared end is
then crimped into a nondistorted airfoil-shaped member such that
the tip cap retainers are positioned above the tip cap, thereby
capturing the tip cap between the seats and the retainers. Coolant
holes are positioned around the perimeter of the tip cap and are
angled so as to impinge coolant against the inner sides of the tip
portion of the airfoil-shaped member.
DETAILED DESCRIPTION OF THE DRAWING
While the specification concludes with a series of claims which
distinctly claim and particularly point out the subject matter
which Applicants believe to be their invention, a complete
understanding of the invention will be gained from the following
detailed description, which is given in connection with the
accompanying drawing, in which:
FIG. 1 is an axial, cross-sectional view of a prior art tip cap
configuration;
FIG. 2 is a top plan view of another prior art tip cap
configuration;
FIG. 3 is a sectional view, taken along line 3--3 of FIG. 2;
FIG. 4 is a partial sectional view of the inventive tip cap
configuration showing an initial step of manufacture;
FIG. 5 is a partial cross-sectional view, similar to FIG. 4, taken
generally along line 5--5 of FIG. 6 and showing the completed tip
cap configuration; and
FIG. 6 is a top plan view of the inventive tip cap
configuration.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring to the drawings wherein like numerals correspond to like
elements throughout, attention is directed initially to FIGS. 1
through 3 wherein prior art attempts at tip cap retention are
shown. For example, one initial attempt at retaining a tip cap 10
in the open end 12 of the airfoil-shaped blade consisted simply of
brazing the tip cap end directly to the side walls 14 and 16 of the
airfoil-shaped blade. In such a case, a suitable braze alloy 18 was
placed at the joint between the tip cap 10 and the side walls 14
and 16, and the assembly was heated in an appropriate furnace. This
type of configuration normally was adequately sealed but had poor
mechanical integrity due to the inconsistency of the braze
joint.
In order to improve the reliability of this design, separate
retention members, such as a pin 20, were occasionally inserted
through holes 22 positioned in the side walls 14 and 16 of the
blade. The pins 20 were then brazed to the side walls 14 and 16
with a suitable braze alloy 24. This configuration improved the
mechanical integrity of the joint and kept the tip cap 10 in place,
but the configuration disrupted the external airfoil shape due to
the projecting portion of the pins 20 and the braze alloy 24
located on the outer side of the side walls 14 and 16. The pins 20
also increased the tip stress and added weight and complexity to
the design.
A further attempt at retaining the tip caps without adding
complexity to the blade is shown in FIGS. 2 and 3 wherein a tip cap
26 is positioned between a pair of side walls 28 and 30, and tip
portions 32 and 34 of the side walls 28 and 30, respectively, are
crimped toward one another at certain locations along the airfoil
as shown in FIGS. 2 and 3. By crimping the portions 32 and 34, the
tip cap 26 was secured to the airfoil blade. The design shown in
FIGS. 2 and 3, however, distorts the desired airfoil shape at the
blade tip thereby potentially reducing the overall efficiency of
such a blade.
Referring now to FIGS. 4 through 6, a turbomachinery blade
constructed in accordance with the present invention is designated
by the general numeral 36. The blade 36 is provided with a hollow
airfoil section 38 which includes a pair of side walls 40 and 42
which define an internal cavity 44.
As best shown in FIG. 4, the turbomachinery blade 36 is formed
initially with a flared, open end 46, which is provided by angled
tip ends 48 and 50 of the side walls 40 and 42. At the approximate
location where the angled tip ends 48 and 50 begin, the side walls
40 and 42 are indented so as to provide tip cap seats 52 and 54,
respectively. At a short radial distance above each of the tip cap
seats 52 and 54, the side walls 40 and 42 are provided with tip cap
retaining members, which in the present case take the form of a
plurality of rabbets 56 and 58 formed integrally with the angled
tip ends 48 and 50 of the side walls 40 and 42.
As further shown in FIG. 4, the flared open end 46 of the
turbomachinery blade is flared to a sufficient width such that a
tip cap 60 may be inserted through the opening formed between the
rabbets 56 and 58 and positioned on the tip cap seats 52 and 54.
The tip cap 60 may take the form of a casting or of a coined piece
and, as shown in FIGS. 4 and 5, may be provided with a generally
U-shaped cross section having a bight portion 62 and a pair of
upstanding leg members 64 and 66. As shown in FIG. 6, the tip cap
60 provides a generally airfoil-shaped flat plate capable of
sealing the entire opening formed between side walls 40 and 42 of
the turbomachinery blade 36.
The tip cap 60 is provided with a plurality of coolant holes 68,
which extend through the bight portion 62 thereof. Each of the
holes 68 is drilled or cast at an angle .alpha. (FIG. 5) with
respect to the vertical so as to direct coolant fluid against the
inner sides of the side walls 40 and 42 near the region of the
rabbets 56 and 58. Furthermore, as shown in FIG. 6, the holes 68
are spaced around the entire perimeter of the tip cap 60. The
angled holes and the spacing around the entire perimeter of the tip
cap provide two basic features, namely improved tip region cooling
and improved aerodynamic sealing at the blade tip. With a plurality
of smaller holes uniformly spaced around the perimeter eof the tip
cap, the hot gas stream air is further precluded from leaking over
the blade tip into the cavity formed above the tip cap 60 even more
than was true in the case of a smaller number of larger holes 70
provided in the tip cap shown in FIG. 2.
Once the tip cap 60 is positioned on the tip cap seats 52 and 54,
as shown in FIG. 4, the angled ends 48 and 50 of the side walls 40
and 42 are formed, such as by crimping, to the configuration shown
in FIGS. 5 and 6, wherein the tip cap 60 is captured between the
seats 52 and 54 and the rabbets 56 and 58. As further shown, when
the crimping operation is complete, the side walls 40 and 42 are
provided with smooth outer contours 72 and 74 which, in turn,
provide a desired airfoil configuration along the entire radial
height of the blade. In other words, no disruptions in the external
airfoil shape are caused near the tip of the blade, while the tip
cap 60 is mechanically secured theeto. As seen in FIG. 5, the
smooth outer contour results in a straight radial line for the
outer contour when a section is taken through the blade tip at any
point between the leading and trailing edge of the blade.
In some applications, it may be desirable to provide a better
fluidic seal for the tip cap 60. In such a case, a suitable braze
alloy may be positioned around the perimeter of the tip cap 60
before or after it is placed on the tip cap seats 52 and 54, as
shown in FIG. 4. Once the side walls 40 and 42 are formed as shown
in FIGS. 5 and 6, the blade can thereafter be placed in a furnace
in which the braze alloy is heated to form a seal and to further
retain the tip cap 60 in place. As best shown in FIGS. 4 and 5, the
upstanding leg portions 64 and 66 of the tip cap 60 are sized so as
to fit between the tip cap seats 52 and 54 and the retaining
members or rabbets 56 and 58. In this manner, the tip cap 60 is
both mechanically secured and, if necessary, brazed to the
turbomachinery blade in a desired location.
While Applicants have described a preferred embodiment of an
inventive tip cap configuration and have further described a novel
method for making a turbomachinery blade using a separate tip cap
configuration, it should be clear to those skilled in the art that
changes could be made in the embodiment described herein without
departing from the broad aspects of Applicants' invention. It is
intended, therefore, that the appended claims cover all such
modifications which fall within the broad aspects of Applicants'
invention.
* * * * *