US3373970A

US3373970A - Gas turbine blade

Info

Publication number: US3373970A
Application number: US600540A
Authority: US
Inventors: Brockmann Heinz
Original assignee: Daimler Benz AG
Current assignee: Daimler Benz AG
Priority date: 1965-12-11
Filing date: 1966-12-09
Publication date: 1968-03-19
Anticipated expiration: 1985-03-19
Also published as: GB1097300A; FR1503348A

Description

March 19, 1968 H. BROCKMANN GAS TURBI NE BLADE Filed Dec. 9, 1966 S A. w

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' INVENTOR HEINZ BROCKMANN BY My? ATTORNEYS United States Patent 12 Claims. c1: 2s3-39.1s

ABSTRACT OF THE DISCLOSURE The present disclosure relates to a blade for a gas turbine, particularly a turbine to be used in a flight propulsion unit. The blade is constructed of inner and outer substantially identically contoured hollow blade members, which are connected together by cooling fins or ribs that extend substantially in the plane of propulsion gas flow. A cooling fluid is introduced into the inner hollow blade and is discharged through radially elongated slots in the forward edge of the inner blade against the interior surface of the outer hollow blade forward edge. The cooling fluid will travel from the forward edge between the inner and outer hollow blade members rearwardly where it is discharged through radially elongated slots in the rearward edge of the outer hollow member smoothly into the flow of propulsion gases so that it will not disturb the flow of propulsion gases and enhance the aerodynamic effect of the turbine blade. The blade construction may be employed in either a rotating blade or a stationary guide vane.

Background of the invention It is known to provide rotating gas turbine blades with interior radial cooling fins. The cooling air enters the inside of the blade from the base and flows, under the influence of centrifugal force, along the cooling ribs where heat transfer takes place and is discharged radially outwardly from the blade tip. This prior are blade construction has a serious disadvantage that the cooling fluid discharged from the blade tip will disturb the flow pattern of the propulsion or working gases. The area of the blade tip usually contributes a considerable portion of the turbine torque; therefore, a disturbance within the area of the blade tip results in a considerable loss of power.

Brief description of the disclosure The present invention avoids the above-mentioned disadvantages while obtaining a good heat transfer within the blade. The blade of the present invention comprises inner and outer hollow substantially identically contoured blade members that are connected together by cooling ribs or fins extending in the plane of working fluid flow. Cooling gases are conducted from the interior of the inner hollow blade through conduits at its forward edge against the inner surface of the outer hollow member forward edge. From this point, the cooling gases extend along the fins rearwardly and pass through ducts in the rearward edge of the outer hollow blade member.

By discharging the cooling air through the rearward edge of the outer blade member, the cooling gases enter the working fluid without producing any eddies, turbulence or other friction loss producing disturbances. In fact, the flow pattern of the working gases is improved, because any vertexes that might form in the area immediately rearward of the rearward edge are eliminated by the discharge of fluid into this area.

The inner hollow blade or insert body may be formed in any way according to the broader aspects of the present invention, for example, by means of a small separate 3,373,970. Patented Mar. 19, 1968 ice tube inserted into the inside of the outer hollow blade. Advantageously, a more narrow aspect of the present invention employs an inner hollow blade member or insert body that matches the internal contour of the outer hollow blade and is mounted on or supported by the cooling fins or ribs that are integral with the outer hollow blade member. The strength of the overall blade structure is enhanced by rigidly connecting the cooling fins between and to the outer and inner hollow blade members. Many prior art structures have required separate reinforcement struts, which are not required with the preferred construction of the present invention. Furthermore, by filling up the outer hollow blade cavity with a substantially identically formed inner hollow blade member, the cooling air is forced to flow in uniform narrow passages closely adjacent to the interior walls of the outer hollow blade member so that the heat exchange efliciency is improved and a relatively small quantity of cooling fluid is required. The arrangement of the cooling fins according to the present invention not only increases the heat exchange surface area, but they also decrease the cross-section of the cooling air flow channel to further increase the heat exchange efficiency. Furthermore, the present invention recognizes the fact that the forward edge of the outer blade member is heated to the greatest extent; by discharging the cooling air against the interior surface of the outer blade member forward edge, the cooling air first contacts the hottest portion of the outer blade member so that the blade member is more uniformly cooled. Even though this is a very considerable advantage over the preferred construction, the cooling air may be discharged from the insert body or inner hollow blade member at any arbitrary point according to the broader aspects of the present invention.

According to the broader aspects of the present invention, the apertures in the insert body and in the rear edge of the outer hollow member may be shaped in any way. However, it is a particular advantage of the present preferred construction that the conduits in the forward edge of the insert body extend the entire height or radial dimension of the insert body and that the ducts in the rearward edge of the outer hollow blade member also extend for the entire height or radial dimension of the outer blade. With this construction, the conduits and ducts may be relatively narrow to conform to the relatively small transverse dimension of the forward and rearward edges while providing a suflicient cross-sectional area to assure proper cooling fluid flow. Furthermore, it is contemplated that the flow cross-sectional area may be varied along the radial dimension to match the temperature distribution, that is, a greater cooling fluid flow may be provided at the areas of highest temperature while a smaller cooling fluid flow may be provided at an area of lower temperature that is radially spaced from the higher temperature area. A very precise control of the radial fluid flow distribution may be obtained by a plurality of radially spaced transverse slots that each extend in the plane of the cooling fins or working fluid flow; the size of the slots may vary in the radial direction or their radial spacing may vary in the radial direction to obtain the proper fluid flow distribution and to match the temperature distribution. These slots may be easily and automatically produced by rotating cutters in a. separate insert body.

The manufacture of the blade may be accomplished in any manner. For example. each of the components may be assembled individually. However, this would be quite costly and complicated. Preferably and most advantageously, the entire blade structure is manufactured in a single casting. With this preferred construction, the assembly time is greatly reduced and the blade strength is greatly increased. For casting the blade, the so-called wax melting process is especially suitable. With this preferred manufacture, the insert body is integrally cast in the one piece structure. However, the insert body may preferably be made separately of thin sheet metal when very small blades are being manufactured.

Other objects, features, and advantages of the present invention will become more apparent from the following description of the drawing:

Brief description of the drawing FIGURE 1 is a cross-sectional view of a preferred embodiment of the present invention taken on a plane parallel to the flow of working fluid;

FIGURE 2 is a cross-sectional view taken along line IIII of FIGURE 1;

FIGURE 3 is a cross-sectional view taken along line III-III of FIGURE 1; and

FIGURE 4 is an elevation view of the rear edge of the blade taken in the direction of arrow A in FIGURE 1'.

Detailed description of the disclosure The preferred embodiment of the present invention includes an outer hollow blade member integrally cast in one piece with a plurality of reinforcing and cooling ribs or fins 11 that are also integrally connected at their inside portions with an insert body or inner hollow blade member 12. The fins 11 extend in the plane of FIGURE 1, that is, in the plane of the working fluid and perpendicular to the radial axis of the blade. Preferably, as shown in FIGURE 1, the profile of the insert body 12 is substantially identically contoured with respect to the outer hollow blade 10. The fins 11 integrally extend between the blade member 10 and the insert body 12 to reinforce them so that additional struts are unnecessary and a rigid strong blade structure is obtained.

Also, the insert body 12 forms a plenum or distribution chamber for the cooling air within its hollow interior. As shown in FIGURE 2, the cooling air enters the blade head or radially outward portion of the insert body 12 through an opening 13. However, it is contemplated that if the present invention is used in a rotating blade, the opening 13 would most advantageously be placed in the foot or radially inward portion 14 of the blade to take advantage of the centrifugal forces. However, a stationary blade has been shown for purposes of illustration and the opening in the foot portion 14 of the insert body 12 is closed by means of a plate 15.

As shown in FIGURES 1 and 3, the insert body 12 is provided with two relatively narrow radially elongated slots 16, 17 in its forward edge for discharging cooling air against the inside surface 18 of the outer hollow blade 10 forward edge portion. Preferably, the slots 16 and 17 provide the only discharge opening in the insert body 12. With this preferred construction, the cooling effect of the fresh cooling air is especially intensive at this highly thermally stressed area 18 of the outer hollow blade 10. From the area 13, the cooling air flows rearwardly around both sides of the insert body, FIGURE 1, along the inner wall portions of the blade member 10 between the cooling fins 11 to the rear edge 19 of the blade member 10. The slots 16 and 17 constitute conduits for discharging the cooling air from the insert body 12. The walls of the insert body 12 and blade member 10 form, along with the cooling fins 11, relatively small cross-sectional area passageways for conducting the cooling air rearwardly from area 18 to area 19. With these small passageways, a relatively small amount of cooling air will be conducted in efficient heat exchange relationship with a relatively large area of the blade member 10 and cooling fins 11. Thus, a very efficient heat exchange relationship is obtained. The thus heated cooling air is discharged from the rear edge 19 in the direction of the working or propulsion gases flowing along the outer surface of the blade member 10 by means of three relatively narrow radially elongated slots or

ducts

20, 21, 22, as shown in 4 FIGURES 1 and 4. The cooling air that is discharged from the

slots

20, 21, 22 mixes with the working gases without producing and disturbance and improves the flow of the working gases within the region of the rearward edge of the blade structure.

As shown in FIGURE 3, the cooling fins are integral with the outer blade member 10 and spaced from the forward edge of the insert body 12. In the figures, the blade member 10 and the insert body 12 have been shown with different cross-hatching to more clearly define their extent and shape; however, it appears to be understood that the preferred embodiment of the present invention relates to an integral one-piece single cast construction for the blade member 10, the cooling fins 11 and the insert body 12. However, these elements may be separate according to the broader aspects of the present invention. In either case, the cooling fins 11 are preferably rigidly attached to both the blade member 10 and the insert body 12 along their sides as was clearly shown in FIGURE 2 to increase the rigidity of the blade structure.

Although a preferred embodiment has been described and illustrated according to the more narrow aspects of the present invention, and various modifications have been described according to the broader aspects of the present invention, it is contemplated that other modifications, variations and embodiments are within the spirit and scope of the present invention as defined in the following claims.

It is claimed:

1. A turbine blade with an outer hollow blade member having an axially forward edge portion and an axially rearward edge portion, hollow insert body means within said blade member for feeding cooling air into the inside of said blade member; said blade member rearward portion having duct means for axially discharging the cooling air generally in the same direction as the driving gases passing said blade member, in combination with the improvement comprising: said insert body means having conduit means for feeding air into said blade member only at its forward edge portions; said blade member having a plurality of integral cooling fins on its inside surface that are generally within flow planes of the driving gases.

2. The device of claim 1, wherein said insert body means generally matches the internal contours of said blade member and has an outer surface generally uniformly spaced from the adjacent inside surface of said blade member; said insert body means being mounted on and engaging said cooling fins.

3. The device of claim 2, wherein said insert body means has a turbine blade profile and an axially forward edge spaced a substantial distance from the cooling fins to constitute a radial conduit.

4. The device of claim 3, wherein said duct means consists of a plurality of relatively narrow radially elongated slots in the rearward edge of said blade member; and said conduit means include a plurality of relatively narrow radially elongated slots in the forward edge of said insert body means.

5. The device of claim 4, wherein said blade member, cooling fins and insert body means are a single homogeneous integral cast unit.

6. The device of claim 5, wherein said insert body means is hollow, and said conduit means includes a cooling fluid inlet radially opening into the interior of said hollow insert body means, and said conduit means slots providing the only discharge openings in said insert body means.

7. The device of claim 1 wherein said insert body means has a turbine blade profile and an axially forward edge spaced a substantial distance from the cooling fins to constitute a radial conduit.

8. The device of claim 1, wherein said duct means consists of a plurality of relatively narrow radially elongated slots in the rearward edge of said blade member; and said conduit means include a plurality of relatively narrow radially elongated slots in the forward edge of said insert body means.

*9. The device of claim 1, wherein said blade member, cooling fins and insert body means are a single homogeneous integral cast unit.

10. The device of claim 2, wherein said duct means consists of a plurality of relatively narrow radially elongated slots in the rearward edge of said blade member; and said conduit means include a plurality of relatively narrow radially elongated slots in the forward edge of said insert body means.

11. The device of claim 2, wherein said blade member, cooling fins and insert body means are a single homogeneous integral cast unit.

12. The device of claim 3, wherein said blade member, cooling fins and insert body means are a single homogeneous integral cast unit.

References Cited UNITED STATES PATENTS 2,514,105 7/1950 Thomas. 2,858,100 lO/l958 Stalker 25339.l5 2,879,028 3/1959 Stalker 253-39.15 2,920,866 1/1960 Spurrier 25339.l5 3,032,314 5/1962 David 25339.15

FOREIGN PATENTS 767,546 11/1952 Germany.

EVERETTE A. POWELL, JR., Primary Examiner.