Patent Application
20100135822
The technical field generally relates to gas turbine engines and, in particular, to turbine blades used in gas turbine engines.
In a gas turbine engine, to maximize efficiency the turbine blade tip is positioned as close as possible to the interior of the static shroud surrounding the blade tips. However, although the clearance between the tip of the blades and the surrounding shroud is kept to a minimum, some of the gas on the pressure side tends to leaks over the blade tip to the suction side, thereby resulting in a loss since the leaking gas does not do any work. So-called squealer tips attempt to reduce tip leakage because of the tip recess presence but additionally by blowing cooling air in the tip region of the blade, but room for improvement remains. It is thus desirable to further improve turbine blade design.
In one aspect, the present concept provides a turbine blade comprising an airfoil having opposite pressure and suction sidewalls extending from a platform to a free end tip and in a chordwise direction from a leading edge to a trailing edge, the blade having a chamfer extending between the pressure sidewall and the tip, the chamfer extending in a chordwise direction, the blade having a plurality of cooling passageways, each extending from an inlet in fluid communication with a pressurized cooling circuit inside the airfoil to an outlet on the chamfer.
Further details of these and other aspects will be apparent from the detailed description and figures included below.
Referring to
A plurality of cooling passageways 60 pass from internal pressurized cooling air circuit(s), in this example generically illustrated as 62, to the exterior through the chamfer 54. The passageways 60 are angled at an angle B to the vertical.
In use, cooling air passing through the passageways 60 is injected at the chamfer 54 to create a curtain of air which between the pressure sidewall 22a and the tip rail 58.
Angle A can be selected depending on the blade pressure loading distribution from leading edge to trailing edge of the tip 50, and can be dependant upon and optimized for a particular blade design. For instance, angle A of the chamfer 54 may be from about 30 to 60 degrees from a vertical reference line. The angle A need not be the same from the leading edge to the trailing edge of the tip 50. Angle B of the passageways 60 can range from about 30 to 60 degrees from a vertical reference line, for instance, but tends to be dependant somewhat on the positioning of the cooling air circuit(s) 62 relative to the chamfer 54. Angle B need not necessarily to be equal from one passageway 60 to the next, and the passageways 60 are not necessarily straight and need not have the same supply location from the cooling air circuit(s) 62. The passageways 60 need not be normal to the chamfer 54. For instance, they can be within about ±15 degrees in orthogonality to the chamfer 54, but may have any suitable interface angle.
Without intending to limit the scope of the protection sought herein, it is believed that this curtain of air may disrupt the amount of, and/or the damaging effects of, the tip leakage flow by creating path resistance for the leakage fluid as it migrates from pressure sidewall 22a to suction sidewall 22b. From a durability point of view, in the case of a tip rub event, the chamfer 54 may allow the outlet of passageways 60 to remain unblocked by debris liberated by the tip rub event, and thereby continue to provide blade tip cooling after such a tip rub event has occurred.
The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the examples described without departing from the scope of what is disclosed herein. For example, the chamfer may have any suitable shape and angle. The row or rows of outlet holes provided thereon may have any suitable configuration. The term “row” is used herein in broad sense and encompasses using staggered or other unaligned sets of outlet holes. Still other modifications will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.
