Wall comprising a film cooling hole

Abstract

A wall of a hot gas part, having a first surface subjectable to a cooling fluid, a second surface located opposite of the first surface and subjectable to a hot gas and, at least one film cooling hole extending from an inlet area located within the first surface to an outlet area located within the second surface for leading the cooling fluid from the first surface to the second surface. The respective film cooling hole has a diffusor section located upstream of the outlet area, the diffusor section is bordered at least by a diffusor bottom and two opposing diffusor side walls, wherein the diffusor section has a delta wedge element for dividing the cooling fluid flow into two sub-flows and subsequent formation of a pair of delta vortices. The respective delta wedge element protrudes in a step-wise manner from the diffusor bottom and is, in a top view, triangular-shaped.

Claims

1. A wall of a hot gas part, comprising: a first surface subjectable to a cooling fluid, a second surface located opposite of the first surface and subjectable to a hot gas and, at least one film cooling hole extending from an inlet area located within the first surface to an outlet area located within the second surface for leading the cooling fluid from the first surface to the second surface, wherein the at least one film cooling hole comprises a diffusor section located upstream of the outlet area with regard to a direction of the cooling fluid flow through the film cooling hole, wherein the diffusor section is bordered at least by a diffusor bottom and two opposing diffusor side walls, wherein the diffusor section comprises a delta wedge element for dividing the cooling fluid flow into two subflows, wherein the delta wedge element extends from a leading edge to a trailing end with regard to direction of the cooling fluid flow, wherein the delta wedge element comprises a top surface and two side surfaces and protrudes in a stepwise manner from the diffusor bottom and is, in a top view, triangular-shape, wherein the top surface of the delta wedge element is lower than the second surface, and whereon the leading edge of the delta wedge element is orthogonally arranged to a plane of the outlet area.

2. The wall according to claim 1, wherein the delta wedge element is adapted to create a pair of delta vortices in the cooling fluid flow during operation.

3. The wall according to claim 1, wherein, when seen in cross section through the film cooling hole, the leading edge protrudes with an angle α of at least 35° from a plane of the diffusor bottom.

4. The wall according to claim 1, wherein the delta wedge element comprises two longitudinal edges, each extending from the leading edge to the trailing end, both two longitudinal edges incorporating a wedge-angle β there between, wherein the wedge-angle β has a value of at least 15°.

5. The wall according to claim 1, wherein the top surface is inclined compared to the diffusor bottom.

6. The wall according to claim 1, wherein the delta wedge element comprises only one single top surface, which is flat.

7. The wall according to claim 1, wherein the diffusor bottom comprises a downstream edge, at which the diffusor section and the second surface merge together in a stepless manner or with an edge, the trailing end of the delta wedge element being located at the downstream edge of the diffusor bottom or upstream thereof.

8. The wall according to claim 1, further comprising: a plurality of said film cooling holes, arranged in one or more rows of film cooling holes.

9. Hot gas part for a gas turbine, comprising: a wall according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention are now described, by way of example only, with reference to the accompanying drawings, of which:

(2) FIG. 1 shows a cross section through a wall comprising a film cooling hole according to the invention as a first exemplary embodiment,

(3) FIG. 2 shows a in a perspective view the film cooling hole according to FIG. 1,

(4) FIG. 3 shows in a perspective view the film cooling hole according to a second exemplary embodiment,

(5) FIG. 4 shows two film cooling holes of a row in a perspective view according to a second exemplary embodiment and

(6) FIGS. 5 to 7 shows in a side view a turbine blade, a turbine vane and a ring segment each representing a wall comprising one or more rows of inventive film cooling holes.

DETAILED DESCRIPTION OF INVENTION

(7) The illustration in the drawings is in schematic form. It is noted that in different figures, similar or identical elements may be provided with the same reference signs. Further, features displayed in single figures could be combined easily with embodiments shown in other figures.

(8) FIG. 1 shows a cross section through a wall 12 of a hot gas part 10 designated to be assembled and used in a gas turbine (not shown). The wall 12 comprises a first surface 14 subjectable to a cooling fluid 17. Opposing to the first surface 14 the wall 12 comprises a second surface 16. The second surface 16 is dedicated to be subjectable to a hot gas 15. In the wall 12 multiple film cooling holes 18 (FIGS. 5-7) are located, from which only one is shown in FIG. 1. Each comprises an inlet area 13 located in the first surface 14. Further the film cooling hole 18 comprises an outlet area 19 located in the second surface 16. Further, the film cooling hole 18 comprises a diffusor section 20 located upstream of the outlet area 19 with regard to the direction of cooling fluid flow though the film cooling hole 18. Upstream of the diffusor section 20 the film cooling hole 18 comprises a metering section 21, which in cross sectional view has a circular shape. Other shapes than circular like elliptical are also possible. The diffusor section 20 is bordered at least by a diffusor bottom 24 and, adjacent thereto, by two opposing diffusor side walls 22 (FIG. 2). Diffusor bottom 24 is that part of the internal surface of the film cooling hole 18 that is opposite arranged to the first surface 14. The diffusor bottom merges laterally into each diffusor side walls 22 via rounded edges.

(9) According to the invention in the film cooling hole 18 onto the diffusor bottom 24 a delta wedge element 26 for dividing the cooling fluid flow into at least two subflows 17a, 17b is located. The delta wedge element 26 acts as means for generating delta-vortices 60 (FIG. 4).

(10) According to the first exemplary embodiment as displayed in the FIGS. 1 and 2, the delta wedge element 26 comprises a leading edge 28 protruding in a stepwise manner from the diffusor bottom 24 as a means for generating delta-vortices 60. The leading edge 28 is straight and orthogonally arranged to the plane of the outlet area 19. In accordance with the cross section displayed in FIG. 1 the leading edge 28 and the diffusor bottom 24 incorporates an angle α. Depending on the manufacturability, in a further embodiment the angle α is 90° or close to that value, as displayed in FIG. 3. Smaller or larger angle values are possible, as long as the leading edge supports the production of delta-vortices 60. In general the delta wedge element comprises only three surfaces, one flat top surface 50 and two side surfaces 52.

(11) As displayed in FIG. 1, the diffusor bottom 24 is embodied as a plane. However, a slight convex or concave curvature is also possible.

(12) As shown in FIG. 2, the delta wedge element 26 is wedged shaped extending from said leading edge 28 in direction of cooling fluid flow to a trailing end 30 in a triangular shaped manner. As a result, the delta wedge element 26 comprises two longitudinal edges 44 extending from said leading edge 28 to said trailing end 30 and incorporating a wedge-angle β there between. In a further embodiment the wedge-angle β has a value not smaller than 15°. However, if desired to optimize the beneficial effects of the delta-vortex, also larger or smaller wedge-angles β are possible. Further, the wedge-angle β is selected such that the longitudinal edges 44 and their just two side surfaces 52 of the delta wedge element 26 are parallel to the diffusor side wall 22 to simplify manufacturing. However, when the wedge-angle β is larger than a lateral opening angle of the diffusor, the strength of the delta-vortices spooling on a top surface 50 can be increased. The lateral opening angle of the diffusor is determined in a top view between the two side walls 22 of the diffusor section 20.

(13) The delta wedge element top surface 50 can be located, as displayed in FIG. 1, underneath the outlet area 19 completely. However, the top surface 50 could also be angled with regard to the outlet area 19. According to FIG. 1, if the top surface 50 is flat and located underneath the outlet area 19 the trailing end 30 is about a distance to a trailing edge 56 of the diffusor section 20.

(14) If the ideal delta wedge element geometry should feature a height of the top surfaces 50 less than the plane of the second surface 16 as displayed in FIG. 2, the laser can take out any amount of material above the delta wedge element to form any desired top surface shape. In that case, the wedge would be completely uncovered as the rest of the diffusor surface is.

(15) FIG. 3 shows also in a perspective view a film cooling hole 18 according to a second exemplary embodiment. Since the main features of the second exemplary embodiment are identical to the features of the first exemplary embodiment, only the differences between the first and second exemplary embodiments are explained here. According to the second exemplary embodiment the trailing end 30 of the delta wedge element 26 merges with the trailing edge 56 of the diffusor section 20, such, that the end of the top surface 50 of the delta wedge element merges with the second surface 16. Depending on the height of the leading edge 28, the top surface 50 merges with or without an edge into the second surface 16 while flushing with the second surface 16.

(16) The effect of the invention will be described in accordance with FIG. 4. FIG. 4 shows a row of film cooling holes 18 comprising a large number of film cooling holes 18, from which only two are displayed in FIG. 4. Each of the displayed film cooling holes 18 comprises the same features according to the second exemplary embodiment. During operation of a gas turbine a hot gas part that comprises the wall 12 having said film cooling holes 18, the hot gas 15 flows along the second surface 16 of said wall 12. The hot gas 15 flows over the outlet area 19 of the film cooling hole 18 and around the jet of cooling fluid emerging from film cooling hole 18 while generating the afore mentioned chimney vortices 62. The chimney vortices 62 are generated pair-wise with first swirl-directions.

(17) The cooling fluid 17 provided to the first surface 14 of the wall 12 enters the inlet area 13 of the film cooling hole 18 and flows first through the metering section 21. After entering the diffusor section 20 the cooling fluid hits the leading edge 28 of the delta wedge element 26 and is separated into o two subflows. Each of the subflows travels along the passage arranged between the side surfaces 52 of the delta wedge element and the diffusor side walls. Parts of each sub flows flow over the longitudinal edges and generates delta-vortices 60 with a second swirl direction. These delta-vortices spool along the longitudinal edges onto the top surface 50. Due to the flow dividing effect of the delta wedge element 26, the delta-vortices are generated pair-wise.

(18) As displayed in FIG. 4 the delta-vortices 60 with the second swirl direction has an opposite swirl direction compared to the first swirl direction of the chimney-vortices 62. These opposing directions compensate the harmful hot gas entrainment-effect between the chimney-vortices 62 of two neighbored film cooling holes. As a result, the lateral film cooling effectively downstream of the film cooling hole 18 is increased while the wall temperature is reduced, compared to the prior art. The improved cooling effectiveness could be used either or in combination to reduce the number of film cooling holes within a row or to reduce the amount of cooling fluid, which has to spend. In summary, said savings leads to an increase of efficiency of a gas turbine using said inventive film cooling holes in their hot gas parts, as described before.

(19) FIGS. 5 and 6 show in a side view a turbine blade 80 and a turbine vane 90 of a gas turbine. Each turbine blade 80 and turbine vane 90 could comprise fastening elements for attaching said part to a carrier, either a rotor disk or a turbine vane carrier. They further comprise a platform and an aerodynamically shaped airfoil 100, which comprise one or more rows of film cooling holes 18, from which only one row is displayed. Either each of the film cooling holes 18 or single ones can be embodied according to the first or second or similar exemplary embodiments.

(20) FIG. 7 shows in a perspective view a ring segment 110 comprising two rows of inventive film cooling holes 18. The displayed ring segment could also be used as a combustor shell element.

(21) Although the present invention has been described in detail with reference to the described embodiment, it is to be understood that the present invention is not limited by the disclosed examples, and that numerous additional modifications and variations could be made thereto by a person skilled in the art without departing from the scope of the invention.

(22) It should be noted that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.