Blade

Abstract

The invention relates to a blade (1), in particular a turbine blade, comprising a blade airfoil (2) which extends in a longitudinal direction (L) and which has an outer wall (3), the outer wall forming: a front leading edge (4); a rear trailing edge (5); a suction-side blade wall portion (6); a pressure-side blade wall portion (7) which is recessed relative to the suction-side blade wall portion (6) on the trailing side; and, in the interior, a cavity (8) for conducting a cooling fluid, wherein, in the region of the trailing edge (5), pressure-side cooling fluid outlet openings (10) spaced apart from one another in the longitudinal direction (L) and connected to the cavity (8) are provided and ribs (11) positioned between the cooling fluid outlet openings (10) are provided, the ribs protruding from an inner surface of the suction-side blade wall portion (6) toward the pressure side and extending transversely to the longitudinal direction (L) toward the trailing edge (5), characterized in that an angle (α) which mutually opposite side surfaces (12) of the ribs (11) include with the inner surface of the suction-side blade wall portion (6) is greater than 90°, in particular greater than 110°.

Description

[0001] shovel

[0002] The invention relates to a blade, in particular a turbine blade, comprising a blade airfoil extending in a longitudinal direction with an outer wall which forms a front leading edge, a rear trailing edge, a suction-side blade wall section, a pressure-side blade wall section set back on the downstream side relative to the suction-side blade wall section, and a cavity in the interior for the passage of a cooling fluid, wherein cooling fluid outlet openings arranged on the pressure side in the region of the trailing edge, connected to the cavity and arranged spaced apart from one another in the longitudinal direction, and webs positioned between the cooling fluid outlet openings are provided, which protrude from an inner surface of the suction-side blade wall section in the direction of the pressure side and extend transversely to the longitudinal direction in the direction of the trailing edge.

[0003] Turbomachines, for example in the form of gas turbines, are known in the art in a wide variety of designs. They serve to convert thermal energy and flow energy of a hot gas into mechanical rotational energy. In the turbine section of the turbomachine, the hot gas is guided through an annular flow channel defined internally by a rotor. In the flow direction, the rotor stages have several turbine stages, each comprising a stationary guide vane ring and a rotor blade ring held on the rotor. The guide vanes protruding into the flow channel have the task of directing the hot gas flow to drive the rotor at the most favorable angle possible onto the downstream rotor blades, which also protrude into the flow channel, in order to apply the greatest possible force to the rotor blades, which causes the rotor to rotate.The rotational energy of the rotor can then be converted into electrical energy, for example using a generator.

[0004] The thermodynamic efficiency of a gas turbine increases with increasing turbine inlet temperature of the hot gas. However, the hot gas temperature is limited, among other things, by the thermal load capacity of the components arranged in the flow channel. One way to achieve the highest possible hot gas inlet temperature is to cool components subject to particularly high thermal stress, such as the guide vanes and / or rotor blades. The aim is to keep the required cooling fluid mass flow as low as possible.

[0005] For this purpose, the blade can have a blade airfoil extending in a longitudinal direction with an outer wall which forms a leading edge, a trailing edge, a suction-side blade wall section, a pressure-side blade wall section set back on the downstream side relative to the suction-side blade wall section, and a cavity inside for the passage of a cooling fluid. In the region of the trailing edge, cooling fluid outlet openings are arranged on the pressure side, connected to the cavity and spaced apart from one another in the longitudinal direction. Between the cooling fluid outlet openings, webs are provided which protrude from an inner surface of the suction-side blade wall section towards the pressure side and extend transversely to the longitudinal direction towards the trailing edge. During operation, a cooling fluid is passed through the cavity of the blade airfoil, cooling the blade airfoil from the inside.The cooling fluid then exits the blade, at least partially, through the cooling fluid outlet openings provided in the trailing edge region. To optimize the aerodynamics of the trailing edge and achieve the most efficient cooling possible in the trailing edge region, the pressure-side blade wall section is set back from the suction-side blade wall section on the downstream side, so that the suction-side blade wall section forms a thin trailing edge vane. This type of design is also referred to as a "cut-back design." Between the cooling fluid outlet openings, webs are provided that protrude from an inner surface of the suction-side blade wall section toward the pressure side and extend transversely to the longitudinal direction toward the trailing edge.These webs, also called "teardraps," primarily serve as stiffening ribs for the portion of the suction-side blade wall section exposed by the recessed pressure-side blade wall section. They typically comprise two opposing side surfaces projecting perpendicularly from the inner surface of the suction-side blade wall section and a top surface connecting them.

[0006] One problem is that, despite the cooling of the trailing edge vane, overheating and oxidation can occur due to the cooling fluid escaping from the cooling fluid outlets, which can cause cracking in particular. Therefore, the trailing edge vane frequently needs to be shortened during maintenance, which impairs its aerodynamic properties.

[0007] Based on this prior art, it is an object of the present invention to provide a blade of the type mentioned at the outset which has an alternative structure. To achieve this object, the present invention provides a blade of the type mentioned at the outset which is characterized in that an angle which opposing side surfaces of the webs form with the inner surface of the suction-side blade wall section is greater than 90°, in particular greater than 95°, and better still greater than 110°. Thanks to side surfaces facing at an angle to one another in this way, the respective upper side of the webs, which is particularly affected by the high temperatures of the hot gas flowing past, is reduced in size compared to those of webs with side surfaces arranged perpendicular to the inner surface of the suction-side blade wall section, as a result of which the webs overheat less quickly.On the other hand, the webs are more effectively cooled by the cooling fluid exiting the blade's cooling fluid outlets. Overall, the turbomachine can therefore operate at higher temperatures or with less cooling fluid, which contributes to high efficiency.

[0008] Preferably, the side surfaces of the webs are curved, in particular concavely curved. This achieves a particularly effective cooling fluid flow along the side surfaces of the webs.

[0009] According to one embodiment of the present invention, the webs have an upper side which has the shape of a triangle tapering towards the trailing edge or the shape of a truncated triangle tapering towards the trailing edge.

[0010] According to a further embodiment of the present invention, the webs have a linear upper surface, thereby minimizing the surface area of ​​the upper surface. Preferably, the webs have an upper surface that adjoins the outer surface of the pressure-side blade wall section flush.

[0011] Alternatively, the webs may have an upper side that is offset in relation to the pressure-side blade wall section in the direction of the suction side, thereby reducing the exposure to hot gas.

[0012] Advantageously, the webs have an upper surface that is not provided with a ceramic coating. Accordingly, the structure of the blade according to the invention is simplified, which also has a positive effect on manufacturing costs.

[0013] Preferably, an intermediate space delimited by the pressure-side blade wall section and two adjacent webs is trapezoidal in plan view when viewed from the pressure side.

[0014] Further features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings.

[0015] Figure 1 is a perspective view of an airfoil of a blade according to an embodiment of the present invention;

[0016] Figure 2 is an enlarged view of section II in Figure 1;

[0017] Figure 3 is an enlarged view analogous to Figure 2, showing an alternative embodiment of webs of the airfoil, and Figure 4 is an enlarged view analogous to Figure 2, showing a further alternative embodiment of webs of the airfoil.

[0018] The same reference numbers refer to the same or similar components or component areas.

[0019] Figure 1 shows a section of a blade 1 according to an embodiment of the present invention, which in this case is a guide vane of a turbine. The blade 1 comprises an airfoil 2 extending in a longitudinal direction L. Furthermore, although not shown here, the blade 1 comprises two platforms that adjoin the free ends of the airfoil 2 in the longitudinal direction L. These platforms serve to fasten the blade 1, on the one hand, to a stator and, on the other hand, to a retaining ring positioned near the rotor.

[0020] The blade 2 has an outer wall 3 which forms a leading edge 4, a trailing edge 5, a suction-side blade wall section 6, a pressure-side blade wall section 7 which is set back on the downstream side relative to the suction-side blade wall section 6, and a cavity 8 inside for the passage of a cooling fluid. The suction-side blade wall section 6 and the pressure-side blade wall section 7 are connected to one another in the present case via two struts 9 which are designed as dividing walls and serve to stabilize the blade 2 and to form a meandering flow path for the cooling fluid within the cavity 8. In the region of the trailing edge 5, cooling fluid outlet openings 10 are arranged on the pressure side, connected to the cavity 8, spaced from one another in the longitudinal direction L, and webs 11 are positioned between the cooling fluid outlet openings 10.The webs 11 protrude from an inner surface of the suction-side blade wall section 6 in the direction of the pressure side, connect the suction-side blade wall section 6 to the pressure-side blade wall section 7 and extend transversely to the longitudinal direction L in the direction of the trailing edge 5. The webs 11 each have, as shown in Figure 2, two side surfaces 12 arranged opposite one another and an upper side 13. The side surfaces 12 of a web 11 are inclined to one another, wherein an angle α, which the side surfaces 12 form with the inner surface of the suction-side blade wall section 6, is greater than 90°, in particular greater than 95°, and better still greater than 110°. In the embodiment shown, the side surfaces 12 of the webs 11 are concavely curved. Alternatively, they can also be designed as flat surfaces, even if this is not shown here.In this case, the upper side 13 adjoins the outer surface of the pressure-side blade wall section 7 and is inclined towards the inner side of the suction-side blade wall section 7 in the direction of the trailing edge 5. In this case, the inclination is selected such that the respective upper side 13 of the webs 11 merges flush with the inner side of the suction-side blade wall section 6. In this case, the upper side 13 has the shape of a triangle tapering towards the trailing edge 5. Intermediate spaces 14 delimited by the inner surface of the suction-side blade wall section 6 and two adjacent webs 11 are trapezoidal in plan view, viewed from the pressure side. In the present embodiment, the outer wall 3 of the blade 2 is provided with a ceramic coating. The upper sides of the webs 11, however, are free of such a ceramic coating.

[0021] Figure 3 shows an alternative embodiment of webs 11 according to the invention, which differs from the design of the webs 11 shown in Figure 2 only in that the upper side 13 of the webs 11 is linear.

[0022] Figure 4 shows a further embodiment of the webs 11 according to the invention, which differs from the design of the webs 11 shown in Figure 2 only in that the upper sides 13 of the webs 11 are not flush with the outer surface of the pressure-side blade wall section 7 but are arranged offset in the direction of the suction side with respect to the pressure-side blade wall section 7, so that a step 15 is formed between the outer surface of the pressure-side blade wall section 7 and the upper side 13 of the webs 11.

[0023] Although the invention has been illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

[0024] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

Claims

Patent claims 1. Blade (1), in particular a turbine blade, comprising a blade airfoil (2) extending in a longitudinal direction (L) with an outer wall (3) which forms a front leading edge (4), a rear trailing edge (5), a suction-side blade wall section (6), a pressure-side blade wall section (7) set back on the downstream side relative to the suction-side blade wall section (6), and a cavity (8) in the interior for the passage of a cooling fluid, wherein in the region of the trailing edge (5) cooling fluid outlet openings (10) are arranged on the pressure side, connected to the cavity (8) and arranged at a distance from one another in the longitudinal direction (L), and webs (11) are positioned between the cooling fluid outlet openings (10), which protrude from an inner surface of the suction-side blade wall section (6) in the direction of the pressure side and extend transversely to the longitudinal direction (L) in the direction the trailing edge (5), characterized in that an angle (a),which encloses the oppositely arranged side surfaces (12) of the webs (11) with the inner surface of the suction-side blade wall section (6), is greater than 90°, in particular greater than 95°, better still greater than 110°., 2. Blade (1) according to claim 1, characterized in that the side surfaces (12) of the webs (11) are curved, in particular concavely curved.

3. Blade (1) according to claim 1 or 2, characterized in that the webs (11) have an upper side (13) which has the shape of a triangle tapering towards the trailing edge (5) or the shape of a truncated triangle tapering towards the trailing edge.

4. Blade (1) according to claim 1 or 2, characterized in that the webs (11) have a linear upper side (13).

5. Blade (1) according to one of the preceding claims, characterized in that the webs (11) have an upper side (13) which adjoins flush with the outer surface of the pressure-side blade wall section (7).

6. Blade (1) according to one of claims 1 to 4, characterized in that the webs (11) have an upper side (13) which is arranged offset in the direction of the suction side with respect to the outer surface of the pressure-side blade wall section (7).

7. Blade (1) according to one of the preceding claims, characterized in that the webs (11) have an upper side (13) which is not provided with a ceramic coating.

8. Blade (1) according to one of the preceding claims, characterized in that an intermediate space (14) delimited by the inner surface of the suction-side blade wall section (6) and two adjacent webs (11) is trapezoidal in plan view when viewed from the pressure side.

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