Turbine blade

The invention relates to a turbine blade. Turbine blades, in particular turbine blades for gas turbines during operation to high temperatures, which quickly exceed the limit of the material stress. This is particularly true in the areas in vicinity of the flow inlet edge. To use turbine blades at high temperatures, it has been known for a long time, turbine blades for cooling adapted so that they have a higher temperature resistance. With turbine blades, which have a higher temperature resistance, in particular, higher energy efficiencies can be achieved.

Known types of cooling are inter alia convection cooling, impingement cooling and film cooling. When convection is probably the most widespread type of blade cooling. In this type of cooling is carried out cooling air through passages inside the blade and uses the convective effect, to remove the heat. In the impingement cooling a cooling air flow from the inside impinges on the blade surface. In this way, a very good cooling effect is made possible at the impact point, which is, however, limited to the narrow range of the impact point and the surrounding area. This type of cooling is therefore usually to cool the flow leading edge of a turbine blade used is subjected to high temperature stresses. In film cooling, cooling air is led to the outside via openings in the turbine blade from the inside of the turbine blade. This cooling air flows around the turbine blade and forms an insulating layer between the hot process gas and the blade surface. The cooling methods described above are appropriately combined depending on the application in order to achieve as effective as possible blade cooling.

In addition to the cooling methods described above, the use of coolants, such as turbulators, which are usually provided in the form of ribs, very common. These are arranged within the prescribed for the convection cooling passages extending in the interior of the turbine blade. The incorporation of ribs in the cooling passages causes the flow of the cooling air is separated and swirled in the border layers. By so forced disturbance of the flow can be increased at a given temperature difference between cooling channel wall and the cooling air of the heat transfer. The ribbing, the flow is constantly forming prompted new "re-attachment fields" in which a substantial increase of the local heat transfer coefficients can be achieved. The service life of known ribs is limited due to the high operating temperatures, which is particularly a result of known ribs underlying geometry. The thermal stresses associated with the known fin geometries have internal cracks result, which can limit the lifetime of the rib and ultimately the service life of the turbine blade.

In order to cool the thermally most heavily stressed during operation flow inlet edge or leading edge of turbine blades parallel and close running transversely to the flow leading edge cooling channels are formed in turbine blades often, which cooling air is supplied by further formed in the blades of the cooling channels. The so realized convective cooling of the flow leading edge is usually supplemented by impingement cooling of the inner wall of the flow near leading edge cooling channel extending in film sensed blades. In applications where no film cooling of the turbine blades is made, the convective cooling is intensified by arranged on the inner wall of the cooling channel turbulators.

Overall, there is present in both film-cooled as well as non-film cooled blades with respect to cooling, particularly with respect to the cooling of the flow leading edge, nor significant need for improvement. In particular, the current cooling solutions also take into account any that forms during use of turbine blades inhomogeneous temperature distribution.

The invention has for its object to provide a turbine blade, which can be cooled effectively both existing as well as in the absence of film cooling over known solutions and which has a higher service life.

This object is according to the invention with a turbine blade with at least one cooling element and a cooling passage for passing a cooling medium, in which flow the at least one cooling element is arranged, dissolved, wherein the at least one cooling element is formed pin-shaped.

According to the invention, the incident flow of the cooling medium cooling elements are configured pin-shaped. Zapf shaped trained cooling elements cause a very strong turbulence of the cooling medium, for example in the form of cooling air, are being increased by the so-enforced strong disturbance of the flow at a given temperature difference between a wall of the cooling channel and the cooling medium, the heat transfer, accompanied by a significant increase in local heat transfer coefficient.

In addition, the forming in the cooling elements during operation of the turbine blade to thermal stresses can with the inventively provided pin-shaped design of the cooling elements to be minimized, so that there can be no internal cracks, in particular in this case the thermal stresses are significantly lower than the thermal stresses, the trained in known cooling fins. According to the invention therefore, the total voltage situation is improved, and there can be obtained a significant increase of the lifetime of the cooling elements with respect to known solutions, wherein the high lifetime of the cooling elements is also connected to a high Einatzdauer or life of the turbine blade.

The turbine blade according to the invention can be exposed to known solutions, higher gas temperatures, even if no film cooling is provided. Provided that film cooling is provided, higher gas temperatures are possible. This in turn results in the ability to form the turbine blade according to the invention with thinner exterior walls.

In one advantageous embodiment of the invention, the turbine blade on an extending on one side of the turbine blade flow inlet edge, wherein the cooling channel to the flow inlet edge is bounded by a wall section and starting extending the at least one cooling element of this wall portion in the cooling passage into it.

By means of this development of the invention can be very effectively cooled in particular the generally thermally highly stressed flow inlet edge. By means of the pin-shaped cooling elements according to the invention, extending from the wall portion in the cooling channel inside, and cause particular a strong turbulence of the cooling medium, can be increased significantly at a given temperature difference between the wall section and the cooling medium, the heat transfer, accompanied by a significant increase of the local heat transfer coefficients. Overall, can be removed very effectively in around the flow inlet edge in this way the heat, accompanied by a very effective cooling of the flow inlet edge.

In a further advantageous embodiment of the invention, the cooling channel is preferably defined by a wall portion facing the cooling channel has a curved wall surface, wherein two or more cooling elements are provided, wherein the cooling elements have in the cooling passage into it extending longitudinal extension, and the two or more cooling elements are oriented with their longitudinal extent towards the center of curvature of the wall surface.

By means of cooling elements, which are directed with their longitudinal extension to the center of curvature of the wall surface, a very effective turbulence of the cooling elements inflowing cooling medium can be achieved. In particular, the realized by means of the cooling elements convection cooling, by means of this further development of the present invention are very effective in combination with an impingement cooling such that the cooling medium flows in a manner to the cooling elements that it impinges on the cooling elements, so that in the respective point of incidence achieves a very high cooling effect may be, which causes in conjunction with the provided convection cooling is a very effective cooling of the turbine blade according to the invention. In a practical development of the invention the wall portion has a to the cooling channel facing wall surface, and the at least one cooling element or the two or more cooling elements extending orthogonal to the wall surface or orthogonal to the curved wall surface into the cooling passage inside. The inventively provided extending in a direction orthogonal to the wall surface of the cooling channel results in a very effective fluidization of the cooling medium, which is accompanied by a very effective cooling, in particular of the flow leading edge, because according to the invention take place at right angles directed essentially to the longitudinal extension of the cooling elements flow towards the cooling elements with the cooling medium can.

In a further practical development of the invention the at least one cooling element or the two or more cooling elements are integrally formed with the wall portion.

In a particularly practical embodiment of the invention, the cooling elements have different lengths, wherein the length of the individual cooling elements preferably is adapted to a predetermined local cooling requirement.

Turbine blades have in operation is usually a very inhomogeneous temperature distribution, which is associated with great, acting on the turbine blades thermal stresses that adversely affect particular the life of the turbine blade. This results, for example, turbine blades, which are used in axial flow turbines, for a flow leading edge along the radial direction forming inhomogeneous temperature distribution. The inventive Einsat for cooling elements within the preferably near the flow inlet edge extending cooling channel whose cooling capacity is adapted along its length to a predetermined cooling requirements, for example for the flow leading edge in the area of the cooling element, the temperature distribution, for example, on the flow inlet edge, are "equalized" because according to the invention at comparatively hot spots by suitably designed cooling elements a correspondingly strong cooling takes place and vice versa. The turbine blade according to the invention can thus be cooled in a manner that counteracts an inhomogeneous temperature distribution, which is particularly in view of an effective cooling of the flow leading edge of advantage.

According to the cooling capacity of each individual pin-shaped cooling element is adjusted via a suitably designed length of the predetermined local cooling requirements around the cooling element. Cooling elements, in their environment, a high demand for cooling, according to the invention have a greater length than the cooling elements in the vicinity of the cooling demand, for example, for the flow inlet edge, is less pronounced. By increasing the length of a single cooling element is the one of "fluidization" as well as the surface to be cooled is increased, accompanied by a significant increase in the local heat transfer coefficients.

The invention further relates to a turbine blade, having a flow inlet edge, one formed in the turbine blade cooling passage for conducting cooling air, the sections extending along at least the flow leading edge and a number of cooling elements which are arranged in the longitudinal direction of the cooling duct in this successively fixed, wherein each cooling element has a cooling capacity which is adapted to a predetermined cooling requirements for the flow leading edge in the area of ​​the cooling element, and wherein the cooling channel preferably parallel to the flow inlet edge extending continuously through the turbine blade.

An exemplary embodiment of a turbine blade according to the invention is explained in detail with reference to the accompanying drawings. Show it:<dl id="dl0001"><dt>1 shows</dt><dd>is a diagrammatic cross-sectional view of a turbine blade according to the invention with a number of cooling channel arranged in a spigot-shaped cooling elements and</dd><dt>FIG 2</dt><dd>a longitudinal section through the turbine blade along a flow inlet edge.</dd></dl>

1 shows a diagrammatic sectional view of a front portion of a turbine blade 10 according to the invention, having a flat sectional area perpendicular to the flow leading edge 12. Inside of the turbine blade 10 close to the flow inlet edge 12 is parallel to the flow leading edge 12 extending cooling duct 14 is formed (that is, a radially extending channel 14 in axial flow turbines), which is opposite to the flow inlet edge 12 is bounded by a wall portion 24th Of a curved wall surface 16 of the cooling channel 14, pin-shaped cooling elements 18 extend into the cooling channel 14, wherein the cooling elements 18 are directed with their longitudinal extension to the center of curvature of the wall surface sixteenth

In a rear wall 20 of the cooling channel 14 openings 22 are formed to the cooling channel 14 of further cooling channels (not shown) formed in the rear region of the turbine blade 10 to supply cooling air.

2 shows a further sectional view of the front portion of the turbine blade 10 according to the invention, having a flat sectional area parallel to the flow inlet edge 12. The formed on the curved wall surface 16 of the cooling passage 14 cooling elements 18 extend perpendicularly from the curved wall surface 16 into the cooling channel 14. As seen from FIG 2 varies in the radial direction R, the length of the cooling elements 18. This serves to erfindungemäß, which counteract with the use of the turbine blade 10 along the flow inlet edge 12 forming inhomogeneous temperature distribution. Thus, in particular the center of the flow leading edge 12 of the turbine blade 10 toward this a higher operating temperature comprise than in the edge areas of the flow leading edge 12. For this reason, the cooling elements 18 in the central region a greater length than in the edge areas because, as stated above, by increasing the length of the cooling elements 18 of the local heat transfer coefficient, and thus the cooling capacity of the cooling elements 18 can be increased.

In addition to the cooling channel 14 is provided by flowing cooling air, and in addition to the cooling by the truncated cone-shaped cooling elements 18 according to the invention is further the use of an impingement cooling of the presently made convection cooling via the. The impingement cooling the present case comprises impact from escaping from the orifices 22 cooling air on the curved wall surface 16 and the cooling elements 18 in order to allow its locally a very good cooling effect. Since the invention provides that the cooling elements 18 are directed with their longitudinal extension of the center of curvature of the wall surface 16, a very effective impingement cooling can be provided, can be provided with in conjunction with the corresponding convection overall a very effective cooling of the turbine blade 10 , The cooling channel 14 is open to both sides 10 of the turbine blade, for flowing the cooling air in two directions from the cooling channel fourteenth Characterized a temperature harmonization of the turbine blade 10 is favored because where cooling air is required, also the cooling air is provided, and the effect of the impingement cooling is not reduced by a cross-flow.

Instead of truncated-cone-shaped structures, the cooling elements 18 can be also formed rib-shaped, extending along the cooling channel 14, ie in the flow direction of the cooling air. The surface of the wall surface 16 is significantly increased to improve the cooling of the then preferably convectively cooled turbine blade 10th It is conceivable that the height of the ribs may be adjusted due to the aforementioned locally different temperatures at the flow inlet edge 12 corresponding thereto.