EP1101901A1 - Turbine blade and method of manufacture for the same - Google Patents

Abstract

The aim of the invention is to produce a turbine blade (1), comprising an outer wall (4), surrounding a hollow cavity, through which a cooling fluid (6) flows and which has an increased life expectancy, even under heavy loading and is simple to produce. The aim of the invention is achieved, whereby the thickness (8) of the outer wall (4), at least over an extent of the blade leading-edge region (7), is such that, at least in pre-determined areas of the external wall (4), pre-determined temperature thresholds (TM) and/or pre-determined temperature gradients ( DELTA TM) are not exceeded.

Description

The invention relates to a turbine blade, in particular Gas turbine blade, which is one of a hot action fluid flowed outside wall, which may have a multi-part Surrounding cavity, which is flowed through by a cooling fluid is, the outer wall over the circumference of the airfoil area in a cross section through the airfoil area the turbine blade is of different thickness, and a method for the production of a cast turbine blade, in particular gas turbine blade, according to the generic term of Claim 27.

To achieve high levels of efficiency and performance during operation one with an action fluid, especially a hot gas, operated turbine, especially a gas turbine, it will Action fluid heated to a high temperature. The ones from are called action fluid, first flow guide and rotor blades are therefore used internally to avoid damage cooled, in particular by means of a cooling fluid flowing through it, for example a cooling gas or a slightly overheated one Cooling steam.

U.S. Patent 5,320,483 discloses how the cooling fluid is in the form of Cooling steam in a closed circuit in the turbine blade is initiated and after flowing through with various flow chambers and inner walls, internal cavity of the turbine blade again is brought out. The cavity is from the outside wall of the Turbine blade surrounded by the hot action fluid of the Turbine is flowing. The outer wall essentially has one constant thickness by considering a cross section through the airfoil area. Despite the training of complex and quite complex to produce channels and Turbulature is within the cavity of the turbine blade it with this type of turbine blade formation, however does not guarantee that the cooling is homogeneous and everywhere to the extent necessary takes place what the lifespan the shovel greatly lowers.

The object of the present invention is an internally cooled Specify turbine blade with the above characteristics, which has an extended service life compared to conventional turbine blades even under very high loads, with low Manufacturing effort is high, as well as high in a turbine Performance and efficiency levels with low NOx emissions enabled and - as a sub-task - a suitable one Production method.

The task directed at the turbine blade becomes thereby solved that the thickness of the outer wall at least over a Partial circumference of the airfoil area in accordance with the course the external heat transfer coefficient on the outside of the Outer wall and the course of the internal heat transfer coefficient the inside of the outer wall is continuous so that predetermined temperature threshold values on the outer wall and / or predetermined temperature gradients between predetermined ones Places on the outer wall must not be exceeded.

The outer wall of the turbine blade is exposed to the hot action fluid not flowed around equally fast and equally strong everywhere, resulting in locally very different heat inputs or heat transfer leads action fluid / outer wall. The external heat transfer coefficient is a measure of this heat transfer. A heat transfer coefficient indicates the amount of heat which passes per unit of time and area. The higher the heat transfer coefficient, the greater the heat transfer, for example by convection or radiation in the material brought in warmth. With an increased external heat transfer the cooling requirement increases at this point on the airfoil.

This locally increased cooling requirement is thereby inventively encountered that the thickness of the metal wall and thus the Exterior wall in places with a high external heat transfer coefficient is reduced. This arises with inclusion the solution of a system of equations that the heat transfer within the different areas of the turbine airfoil describes. The heat transfer includes the one hand Heat transfer from the hot action fluid to the outside of the Outer wall and from the inside of the outer wall to the cooling fluid. Furthermore, the heat conduction in the system of equations described inside the outer wall. A thinner outer wall increases heat conduction. As boundary conditions for the solution of the system of equations are the temperature threshold values, the temperature gradients are set. They are characteristic for the outer wall and essentially make one upper limit for the action fluid temperatures Compliance with these values ensures that no temperatures to be exceeded on the bucket, causing local damage and ultimately to the early failure of the turbine blade could lead. The temperature threshold corresponds to the Rule of an oxidation limit of the outer wall material, the temperature gradient is a measure of due to different Temperatures between two places on the outer wall thermal stresses. To ensure a long service life the turbine blade may have a critical value that of the material, the composition of all involved Voltages and depends on the operating load spectrum, not exceed.

The solution of the system of equations shows that a thinner Formation of the outer wall in a kind of dynamic Balance the temperature level and the applied temperature gradients reduced. In principle, one leads thinner design of the outer wall for an improved cooling effect due to the increased heat dissipation through the blade outer wall material. However, this is still subject to the requirements the stability of the thickness of the outer wall set lower limit. With skillful training of the interior, for example by inserting ribs as below described, this lower limit is still a little too shifted to smaller thicknesses.

By locally varying the thickness, the local can increased cooling requirements in places with high external heat transfer coefficients be met in a simple manner. In places with a low external heat transfer coefficient, the Outer wall can be made even thicker, which is stability elevated. Due to the adjustment of the outer wall thickness achieved, individually adapted cooling effect can be complicated trained channels inside the cavity become. This simplifies the manufacture of the turbine blade and lowers costs. In addition, the required Cooling fluid mass flow reduced by the adapted cooling, which improves the efficiency and performance of the turbine.

It is advantageous if the outer wall has a multilayer structure is and a thin ceramic on the outside wall Protective layer and inside has a metal wall and that one The temperature gradient between the Outside and the inside of the metal wall. By the multilayer structure can the outer wall with a suitable Choice of layers of different tasks and requirements fulfill. The metal wall, especially from a high-temperature resistant Metal alloy, ensures in addition to sufficient mechanical strength and good thermal elasticity what due to the changing mechanical loads and temperatures necessary is. A ceramic protective layer protects the metal wall from excessive temperature loads or prevented an oxidation or corrosion. The protective layer should among other things, prevent that by the inflow through the hot action fluid on the bucket outer wall caused highest temperature a material-specific maximum value exceeds, or an emerging temperature gradient between the outside of the outside wall and the inside the outer wall exceeds a certain critical value. Usual high-performance blades are sufficient thick ceramic protective layers are instructed for thermal insulation, so that temperature and voltage limits can be maintained. By the high loads during the operation of the turbine, in particular through rapid temperature changes respectively large voltage differences between different areas the outer wall and due to the already existing in the cold state Lattice parameter differences between the ceramic Protective layer and the metal wall and different coefficients of thermal expansion ceramic thermal insulation layers burst prematurely from the metal wall. This closes then a failure of the shovel. This is according to the invention thereby preventing the thickness of the metal wall from being correct the heat transfer coefficient is set and the temperature threshold and the temperature gradient between the Outside and inside of the metal wall predetermined Do not exceed values. These values are according to the corresponding ones Requirements of the protective layer or the boundary layer designed between protective layer and metal wall. So that's enough it, a very compared to usual protective layer thicknesses apply a much thinner protective layer to the metal wall. The thinner formation of the layer also improves the Adhesion of the protective layer on the blade surface and prevents a local chipping because the different thermal expansion of the materials due to the thin layer thickness no longer have such an impact. At the same time this thin layer is much easier to apply, among other things because they have lower requirements with regard to homogeneity. This reduces the manufacturing costs and at the same time increases the service life the shovel.

If the temperature threshold on the entire outer wall and / or predetermined temperature gradients over the entire Outer wall not be exceeded are particularly good conditions for a low thermal or voltage Given a load on a turbine blade. This is special important for coated turbine blades. By a more even, lower temperature due to the outer wall the thickness of the outer wall according to the invention good adhesion of the ceramic protective layer to the metal wall guaranteed without further manufacturing Measures would have to be taken or the hot gas temperature would have to be reduced, which would reduce the efficiency.

For thermal reasons it is possible to use ceramic Omit protective layer completely when the temperature threshold and the temperature gradient critical material-dependent Values. A possible protective layer in this case it is still used for prevention from corrosion or oxidation attacks and can therefore at least thinner than conventional ceramic protective layers be trained. This reduces manufacturing costs and increases the lifespan of the bucket.

It is particularly advantageous if the outer wall has one layer and is made of metal. The metal is also with relatively high temperatures still stable and conducts at the same time the heat well, so that the cooling inside and the adapted thicknesses of the outer wall the temperature threshold values and the temperature gradients can be maintained.

To be increased especially with thin metal wall sections Tensions in the outer wall, for example due to a high internal pressure to counter increased primary voltages, it is proposed that a field of ribs in the cavity is provided where an outer wall area of reduced thickness is present. In this way, thinner areas of the outer wall strengthened to have approximately the same stability, like thicker areas. This allows a homogeneous Stress on the turbine blade outer wall and a achieve uniform material utilization. Because of the homogeneous Stress and strain distribution becomes better long-term adhesion the ceramic protective layer on the base material reached, which leads to an extension of the blade life leads. By limiting the primary stresses caused by internal pressure by attaching rib fields depending on the wall thickness in the cavity and limitation of thermal stresses by adhering to a limit value for the temperature gradient will damage the material due to too many cycles the resulting total van Mises reference voltage, which are the primary voltage, the thermal voltage as well includes other voltages, reliably prevented. At key and Blades are used to calculate the thermal Guide values, i.e. the thickness variation is approximately the same. For the The design of the rib fields is to be taken into account for blades, that tensions due to centrifugal force are added, as well as additional secondary flows.

These advantages mentioned above are achieved in particular by that the ribs of the field according to the thickness of the Outer wall, the temperature threshold and / or the temperature gradient and / or that predetermined by Mises reference voltage Have dimensions, distances and spatial arrangements. An optimal combination of parameters enables wide areas compliance with the temperature target values, so that a homogeneous loading of the material and an even Material utilization can be achieved. A limitation of Thermal stresses already occur through the Adherence to the predetermined temperature gradient by setting the thickness of the metal wall and thus the outer wall. The primary voltage is limited by the attached ones rib panels depending on the wall thickness on the inside the outer wall. Are predetermined distances between the ribs adhered to, on the one hand, an optimal cooling effect, at the same time, however, an optimal stability of the material can be achieved. Other parameters are the height and the width of the ribs and their spatial arrangement. By it is a certain arrangement of ribs in rib fields possible, thin and at the same time durable outer walls for optimal thermal wall design with or without ceramic To produce protective layers. These measures can be taken in the Usually used for both guide and rotor blades become.

If in particular the field of the ribs at least in sections runs across the flow of the cooling fluid, the Turbulence of the cooling fluid increases, which improves the cooling effect, without using additional turbulators ought to. Due to the transverse to the flow direction of the cooling fluid arranged rib fields is just in the areas with thinner wall thickness where there is a higher internal heat transfer coefficient is required, a desired higher cooling effect is achieved. In order to achieve the desired swirl, it is important to that the ribs are neither too narrow nor too far apart be arranged, because otherwise they are not sufficient Turbulence or insufficient stability achieved become.

If the ribs have transverse openings, the cooling fluid is added flowing through the interior more turbulent. This improves again the cooling effect. The openings are designed that they do not affect the stability of the ribs.

It is advantageous if the cavity from the pressure side to Suction side in the longitudinal direction of the turbine blade from the inner walls is crossed, the inner walls to the pressure side or suction-side outer wall with a continuous course connected the continuous course of the thickness of the outer wall are. By dividing the cavity from the Pressure side to the suction side ensures that the stability the turbine blade is preserved or improved becomes. At the same time, the cavity is divided into several chambers. The shape and number of interior walls used for this is selected depending on the type of cooling and cooling fluid properties, that the simplest possible construction of the cavity results. This means that an inexpensive, conventional one Investment casting technology can be applied. If the inner walls to the pressure-side or suction-side outer wall under continuous Course on the continuous course of the thickness are connected to the outer wall, voltage peaks in the outer wall are reduced. The inner walls reinforce the Outside wall areas and thus absorb tensions caused by a changing thickness, and different temperatures in the outer wall and thus different heat transport arise. It also takes into account that everywhere an optimal speed level of the cooling fluid and thus gives an optimal internal heat transfer coefficient. Due to the division of the cavity, only a small number occur Pressure losses. It is therefore a high proportion of energy recoverable from the heated cooling fluid.

An additional improvement in corrosion resistance is given that the cavity with an aluminizing layer is provided, in particular the steam-wetted inner surfaces.

The efficiency of the turbine is hardly affected by the cooling fluid or only minimally reduced if the cooling fluid in one closed circuit through the turbine blade becomes. Leadership in a cycle can also be more Turbine blades include, which also saves cooling fluid becomes. The fact that no cooling mixture by in the cooling fluid escaping, the fluid remains Efficiency and thus the performance of the turbine preserved. It no cooling fluid is consumed, which reduces the operating costs of the Turbine lowers. The cooling fluid inside the turbine blade Most of the heat absorbed can be reused. This improves energy utilization and increases the Efficiency.

An advantageous spatial arrangement of the cavity of the turbine blade is supported by the fact that the inlet and the outlet of the cooling fluid are arranged in the foot area. From The cooling fluid is then in the different area other cooling areas. The foot area is for supply lines of the cooling fluid more easily accessible.

The cooling fluid is used economically if that the head and foot area of the turbine blade at the same time is cooled with the cooling fluid of the airfoil region. This is the structure of the head, foot and shovel area and especially the transitions between areas simplified.

A more precise adaptation to the really required cooling is given that the turbine blade is a moving blade is and the wall thickness of cooling chambers in the cavity as required a local heat transfer coefficient varies locally. By The rotary motion of the blade will cool the fluid in some areas of the cooling chambers against the inner walls or pressed against the outer walls. This causes one inhomogeneous internal heat transfer coefficients. This is changed by changing the wall thickness of the inner walls or the outer wall balanced according to the invention. Through the Adjusting the wall thickness is only the absolutely necessary Used amount of material and at the same time a more adapted Coolant consumption reached. This will increase efficiency the turbine increased and at the same time one in all areas the Scahuefl ensures adequate cooling.

It is advantageous if in the central area of the airfoil area Central cooling chambers formed by inner walls are provided are flowed through by the cooling fluid. The Middle cooling channels are located in the one with the most through areas of the turbine blade exposed to high heat input. They therefore carry a large proportion of the heat input in itself. The serial flow ensures a long, meandering path of the cooling fluid through the turbine blade and thus a good use of the heat capacity of the cooling fluid. The cooling fluid is in particular at deflection points strongly swirled and thus improves the cooling effect. The amount of cooling fluid required is reduced.

A quick flow of the cooling fluid and thus an improved one Heat dissipation is given by the fact that in the central area of the airfoil area formed by inner walls Central cooling chambers are provided which are parallel to the cooling fluid are flowed through. At the same time, this means the construction of the cavity in which the cooling chambers are located, simplified and thus a less wasted casting enables in the manufacture.

The flow rate of the cooling fluid just before the impact on the outer wall is raised if at least one of the Central cooling chambers an impingement cooling insert with outward-facing Impingement bores, which are at a distance of arranged on the inside of the outer wall and that of the cooling fluid are flowed through. Due to the increased flow rate of the cooling fluid hitting the inside of the outer wall the cooling effect is significantly improved. This is it possible, also using a coolant with low pressure achieve a good cooling effect without going through the outer wall to stress high primary voltages due to the internal pressure.

A simple, safe and inexpensive way of holding of the impact cooling insert is given when the impact cooling insert from on the inside of the outside wall and / or from on the inside wall and / or spacers mounted on ribs is held.

A further improvement of the cooling is given by that additional cooling at the rear edge of the turbine blade is available. This is particularly advantageous because there External walls converge more closely and thus connect to the other cooling chambers is often difficult.

In particular, it is a separate, closed one Steam cooling.

If, alternatively, one at the rear edge of the turbine blade open air cooling with free outlet is available no return line required. The air used is freely introduced into the action fluid space. Since it's just A relatively small amount of cooling air is the efficiency the turbine thereby reduced little.

To achieve a higher internal heat transfer coefficient it is advantageous if the cooling fluid is steam. The scarce, for low pollutant emissions with pulsation-free operation required compressor air does not have to be used. A closed air cooling requires a lot of air and causes high pressure drops. When using steam as the cooling fluid are 1.5 to three times higher internal heat transfer numbers than air achievable. The use of steam enables thus operating the turbine with a hotter action fluid, which in turn increases efficiency. When cooling air is introduced into the action fluid, high Efficiency losses. Maintaining the temperature of the action fluid it is possible to use cooling steam, to make the turbine blade outer wall thicker, which the Stability of the bucket increases and the demands on the Rib fields reduced. They are also solutions without rib fields possible. Cooling steam possesses air at the same time even higher heat capacity, resulting in an improved Heat removal from the turbine blade leads.

When using a low pressure steam is an embodiment of the cavity with few cooling chambers in the leaf area possible. This low pressure steam is characterized by a Inlet pressure of 15 bar or an inlet temperature of about 250 ° C. Due to the low pressure is the burden the outer wall is reduced by primary stresses caused by internal pressure and there will be fewer ribs to stabilize the Outside wall needed. The interior can be designed in this way, for example be that two cooling chambers formed by an inner wall are flowed through by cooling fluid in series. Advantageously is at least in one of the cooling chambers Impingement cooling insert, which has impingement cooling holes, which from Cooling fluid flows through, and that of on the inside the outer wall and / or on the inner wall and / or on some the webs attached to the ribs is held. Because of the engagement Impact cooling bores make the cooling steam locally strong accelerates and thus increases its cooling effect. The acceleration takes place through the baffle cooling holes on the inside the outer wall, and thus increases the internal heat transfer coefficient.

The steam has particularly good cooling properties when it is on Is medium pressure steam. Medium pressure steam is marked through inlet data of approximately 30 bar pressure and 350 ° C inlet temperature. At the same time, the internal compressive stress level not very high yet, so the tensions that arise still are manageable. The medium pressure steam is in modern combined cycle power plants directly available and does not have to lose energy be additionally provided. By the higher one Vapor pressure is higher than that of low-pressure steam Heat transfer numbers and better heat transfer. Under The wall thickness is the guarantee of a constant cooling effect the turbine blade can thus be made thicker, as a result of which the Stability of the turbine blade is increased and the wall increased primary voltages due to the high pressure of the medium pressure steam withstands better. The cavity also exhibits Using a medium pressure cooling steam only cooling chambers on. Impact cooling inserts can be dispensed with. This simplifies it manufacture and reduce costs.

The outer contour of the turbine blade advantageously corresponds to that Course of an aerodynamically predetermined shape, the The thickness of the outer wall towards the cavity varies. The shape points thus the advantage of maintaining the temperature threshold values and at the same time does not deviate from its external form from the usual profiles, so that the turbine blade in usual Turbines can be used and the already known Has flow properties.

The sub-task related to the manufacturing process is solved in that the mold is arranged so that the profile course of the outer contour of the casting core of the difference between an aerodynamically predetermined, in particular outer Profile course of a turbine airfoil and one Function that corresponds to the course of the external Heat transfer coefficient on the outside of the outer wall of the Turbine blade and the course of the internal heat transfer coefficient on the inside of the outer wall of the turbine blade runs continuously so that at least at predetermined Setting the outer wall predetermined temperature threshold values and / or predetermined temperature gradients between predetermined places of the outer wall are not exceeded. In particular, the outer profile profile corresponds to this a standardized profile.

So only a cast core is used, the outer curvature or geometry with the variable thickness of the outer wall as well as possibly with the geometries of the corresponding rib fields relative to a surrounding mold or outer contour is changeable. This core is compact, possesses an easy to manufacture shape that is easily supported can and is not subject to excessively narrow tolerance requirements. This means that conventional investment casting processes, as well as methods with directional solidification or single crystal solidification feasible without additional costs. The turbine blade can be cast in one piece in their airfoil area become. The committee for casting is due to the simple shape reduced. The outer wall of the Cast product of the turbine blade of different thickness, essentially no post-processing is necessary is. By simply taking the different thickness trained external walls can comply with temperature limits are made without expensive coatings should be, which also easily flake off again.

Both for low pressure and medium pressure steam constructions common, low-reject methods are used, since the minimum outer wall thicknesses are approximately 1 to 2 mm compared to the usual outer wall thickness of steam-cooled Turbine blades are almost twice as big and that Casting tolerances are approximately 0.15 mm, which in one for usual casting process problem-free area. This simplifies it the manufacture and reduces the manufacturing cost considerably.

The invention is illustrated in the figures Exemplary embodiments explained in more detail.

Fig.1 einen Querschnitt durch eine niederdruckdampfgekühlte Turbinenleitschaufel mit variierender Außenwanddicke,

Fig.2 eine schematische Ausschnittsvergrößerung der Außenwand zur Darstellung des Wärmeübertragungsmechanismus in der Außenwand,

Fig.3 einen schematischen Schnitt durch einen Schaufelblattbereich und einen Fußbereich einer niederdruckdampfgekühlten Turbinenleitschaufel von Fig.1,

Fig.4 ein Fließschema des Kühldampfes durch eine niederdruckdampfgekühlte Turbinenleitschaufel im Längsschnitt von Fig.1,

Fig.5 einen Schnitt durch ein Rippenfeld,

Fig.6 Queröffnungen der Rippen,

Fig.7 einen Querschnitt durch eine mitteldruckdampfgekühlte Turbinenleitschaufel,

Fig.8 einen schematischen Schnitt durch einen Schaufelblattbereich und einen Fußbereich einer mitteldruckdampfgekühlten Turbinenleitschaufel von Fig.7,

Fig.9 ein Fließschema des Kühldampfes einer niederdruckdampfgekühlten Turbinenleitschaufel im Längsschnitt von Fig.7,

Fig.10 ein Fließschema mit Fließwiderständen der Schaufel,

Fig.11 einen schematischen Schnitt durch eine mitteldruckdampfgekühlte Turbinenleitschaufel und

Fig.12 ein Fießschema der Turbinenleitschaufel von Fig.11.

Show it:

1 shows a cross section through a low-pressure steam-cooled turbine guide vane with a varying outer wall thickness,

2 shows a schematic enlargement of the outer wall to show the heat transfer mechanism in the outer wall,

3 shows a schematic section through an airfoil area and a foot area of a low-pressure steam-cooled turbine guide vane from FIG. 1,

4 shows a flow diagram of the cooling steam through a low-pressure steam-cooled turbine guide vane in the longitudinal section of FIG. 1,

5 shows a section through a rib field,

Fig. 6 cross openings of the ribs,

7 shows a cross section through a medium-pressure steam-cooled turbine guide vane,

8 shows a schematic section through an airfoil area and a foot area of a medium-pressure steam-cooled turbine guide vane from FIG. 7,

9 shows a flow diagram of the cooling steam of a low-pressure steam-cooled turbine guide vane in the longitudinal section of FIG. 7,

10 shows a flow diagram with flow resistances of the blade,

11 shows a schematic section through a medium-pressure steam-cooled turbine guide vane and

12 shows a flow diagram of the turbine guide vane from FIG. 11.

1 shows a cross section through an airfoil area 7 a low-pressure steam-cooled turbine guide vane 1 with varying outer wall thickness 34. The turbine blade 1 is on the outside 9 of the outer wall 4 of a hot action fluid 2, in particular a hot gas. For cooling is the turbine blade 1 in its inner, in general multi-part cavity 5, which from the outer wall 4th is surrounded by a cooling steam 6, namely a low-pressure cooling steam, flows through. The cavity 5 is in the longitudinal direction the turbine blade 1 is traversed by inner walls 20, which the blade profile in the direction from the pressure side 46 pull through to suction side 45 so that several central cooling chambers 21 arise, in this case two, the inner walls 20 to the pressure-side or suction-side outer wall 4 below continuous course to the continuous course of Thickness 34 of the outer wall 4 are connected. The central cooling chambers 21 have impingement cooling inserts 22, the walls of a plurality of small impingement cooling holes 23 broken are. The low pressure cooling steam is through the impingement cooling holes 23 pressed through and on the inside 13 of the Outer wall 4 accelerated. Because of the quick impact the inside 13 of the outer wall 4 is then uniformly intense chilled. The cavity has in the leading edge region 32 5 two front cooling chambers 31 through which also Cooling steam flows through and the inside 13 of the outer wall 4 is cooled. The cooling takes place here by convection.

The outer wall 4 may have a multi-layer structure and has a metal wall 3, if necessary a ceramic protective layer 15 on the outside and an aluminum alloy layer 54 on the inside, as shown in FIG. The metal wall 3 has different thicknesses 8 along a cross section through the airfoil region 7. The thickness 8 of the metal wall 3 varies continuously, ie without jumps or continuously in order not to cause stress peaks, in accordance with the external heat transfer coefficient W _ex on the outside 9 of the outer wall 4 The thickness 33 of the ceramic protective layer 15 is approximately constant. The thickness 34 of the outer wall 4 thus also varies with the thickness 8 of the metal wall 3. The external heat transfer coefficient W _ex is given by the size of the heat transfer from the hot gas 2 into the outer wall 4. The principle of heat transfer through the outer wall 4 is illustrated in Fig.2. The external heat transfer takes place with a locally different size, indicated by the external heat transfer coefficient W _ex , to which the thickness 8 of the metal wall 3 or the thickness 34 of the outer wall 4 is adapted.

The thickness 34 of the outer wall 4 or the thickness 8 of the metal wall 3 is also set according to the invention in accordance with the internal heat transfer coefficient W _int on the inside 13 of the outer wall 4. The type and the physical parameters of the cooling fluid 6 have a decisive influence on the internal heat transfer coefficient W _int . The internal heat transfer coefficient W _{int can also be} changed by the construction of the cavity 5 on the inside 13 of the outer wall 4, for example by means of ribs 16.

The cavity 5 has ribs 16 in the areas 14 of the outer wall 4 which are particularly thin or which are particularly strong Are subjected to loads and thus stabilized have to. Ribs 16 are, for example, on both inner sides 13 of the outer wall 4 with an impact cooling insert 22 provided middle cooling chamber 21 transverse to the flow 18 of the cooling fluid 6 running attached. The middle middle cooling chamber 21 only indicates on the inside 13 of the outer wall 4 the suction side 45 of the turbine guide vane 1 ribs 16 on the pressure side 46, however, only spacers 44, the Hold the baffle insert 22 in place. On some of the ribs 16 are also spacers 44 for positioning of the impact cooling insert 22 available.

The ribs 16 have predetermined dimensions, such as the thickness 37, the height 41, their foot radius 39, their head radius 40, their load-bearing width 38 and spatial arrangements that are special are suitable for swirling the cooling fluid flow 18 contribute or a sufficient cooling surface to deliver on the inside 13 of the outer wall 4. A depiction can be found in Fig. 5 and 6. A good swirl is particularly given when the ribs 16, which in Rib fields are arranged that are transverse to the direction of flow 18 of the cooling fluid 6 are.

The thickness 8 of the metal wall 3 or the thickness 34 of the outer wall 4 moves between approximately 0.6 mm to 1.0 mm in the rear edge area 36 up to approximately 2 mm in the printing area 46. The changes between the individual thickness ranges that are delimited by inner walls 20, have a reduction continuous transitions 10 of voltage peaks for example by means of a linear interpolation between the different target thicknesses.

Fig. 2 shows schematically the heat transfer from an action fluid 2 to a cooling fluid 6 via an outer wall 4 and a schematic profile of the temperature T. The outer wall 4 of the Thickness 34 is constructed in several layers. It has an external one ceramic protective layer 15 of thickness 33, a load-bearing Metal wall 3 of thickness 8. In cavity 5 and in particular on the inside 13 of the outer wall 4 is optional an aluminization layer 54 against corrosion is provided. The coating 54 can be made very thin. Is the Coating 54 is not attached, the inside 13 of the Outer wall 4 is equal to the inside 12 of the metal wall.

The hot action fluid 2 flowing on the outside has a temperature T that is higher than that of the outer wall 4. Heat transfer to the outer wall 4 takes place on the outside 9 of the ceramic protective layer 15. The external heat transfer is characterized by the external heat transfer coefficient W _ex , the size of which indicates how much heat is transferred to the outer wall 4. The local heat transfer between the action fluid 2 and the outer wall 4 has different external heat transfer coefficients W _ex for different outer wall sections 14 of the airfoil area 7 of the turbine blade 1 and thus different thicknesses 8 of the metal wall 3.

After the heat has entered the outer wall 4, there is first heat conduction through the ceramic protective layer 15 and then through the metal wall 3. The heat conduction of the ceramic protective layer 15 is different from that of the metal wall 3. Thus, the temperature profile T at the transition from the inside 35 has ceramic protective layer 15 on the outside 11 of the metal wall 3 on a discontinuity. On the inside 12 of the metal wall 3, which in this case corresponds to the inside 13 of the outside wall 4, the heat emerges from the outside wall 4, which is described by the internal heat transfer coefficient W _int . On the inside 13, the cooling fluid 6 flowing past takes the heat with it. The temperature curve T shows a sharp drop in this area.

In the area of the transition from the ceramic protective layer 15 to the metal wall 3, a temperature threshold value T _{M is} defined which is characteristic of the temperature resistance of the outer wall material, inter alia for the adhesive quality of the ceramic protective layer 15 on the metal wall 3. Between the maximum metal temperature </ = T _M and the temperature on the inside 12 of the metal wall 3, a temperature gradient ΔT _{M is} defined. It is a measure of temperature differences and thus also of the voltage load on the outer wall 4. By setting the thickness 8 of the metal wall 3 according to the invention, it is achieved that at least at predetermined locations on the outer wall 4 predetermined temperature threshold values T _M and / or predetermined temperature gradients ΔT _M between the The outside 11 of the metal wall 3 and the inside 12 of the metal wall 3, that is to say predetermined locations on the outside wall 4, are not exceeded. This ensures that the outer wall 4 of the turbine blade 1 is not excessively stressed, the ceramic protective layer 15 adheres better to the metal wall 3, no oxidation occurs and thus a permanent use of the turbine blade 1 is possible. For a target lifespan of the blade of at least 25,000 equivalent operating hours or approximately 1000 normal load cycles for current blade materials or operating load spectra, the predetermined temperature threshold value T _M is approximately 930 ° C to 950 ° C and the predetermined temperature gradient ΔT _M is approximately 200 to 220 ° C or at approximately 260 to 290 ° C above the metal wall thickness 8.

3 shows a top view of the foot region 26 of a turbine blade according to Fig.1. The foot region 26 has one Inlet 27 and an outlet 28 for the cooling fluid 6. Schematic is the position of the airfoil area 7 relative to Foot region 26 of the turbine blade 1 indicated. The cooling fluid 6 flows through the turbine blade 1 in central cooling chambers 21 with impact cooling inserts 22 and convective in front cooling chambers 31 in the leading edge area 32. On the trailing edge 36 of the turbine blade 1, additional cooling 56 is provided, which is preferably a separate, closed one Steam cooling is concerned.

4 shows a side view with a flow diagram of the Cooling fluid 6. After the inlet 27 of the cooling fluid 6 in the foot area 26 of the turbine blade 1 flows through the cooling fluid 6 the trailing edge region in a branched cooling fluid partial flow 47 36 of the turbine blade 1. Another branched Cooling fluid partial flow 48 flows through a front cooling chamber 31 in Leading edge area 32. after leaving the airfoil area 7, the cooling fluid 6 passes through the head region 25 of the Turbine blade 1. Thereupon it first flows through the the front cooling chamber 31 lying on the suction side 45 and after one Redirection of the adjacent front cooling chamber on the pressure side 31 to outlet 28 in foot area 26.

Another cooling fluid partial flow branched off from the supplied cooling fluid 6 49 flows through a first central cooling chamber 21, which has an impact cooling insert 22. After passing through the cooling fluid 6 flows serially through the head region 25 second cooling chamber 21, which also has an impact cooling insert 22 has, in the opposite direction to the first. After reaching of the foot region 26 of the turbine blade 1 various streams are brought together and through outlet 28 released from the turbine blade 1. The cooling fluid 6 is at the same time to flow through the airfoil area 7 and the Head 25 and foot area 26 used. It's just a only closed circuit for the cooling fluid 6 is necessary, which simplifies handling and the manufacturing costs decreased.

The head area 25 and the foot area 26 are simpler by means of Weld or solder joints 24 on the airfoil area 7 of the turbine blade 1 attached or with end plates 17th locked. This simple type of attachment is due the simple construction of the cavity 5 possible. In the head 25 and foot area 26 can support the cooling effect of the cooling fluid 6 impingement inserts 22 are housed what is not shown.

Fig. 5 shows schematically ribs in an enlarged section 16, which reinforce the thinned areas of the outer wall 4 are used. The supervision of the ribs 16 from Fig.1 takes place in the transverse direction, so that only ribs 16 transverse to Flow direction of the cooling fluid 6 are visible. Along one Rib 16 are transverse rib openings 19 of predetermined dimensions and spacing attached, as shown in Fig. 1 and Fig. 7. They serve the cross exchange and the additional swirling of the cooling fluid 6, whereby the cooling effect of the cooling fluid 6 is improved. This can be varied, for example the height 42 of the rib openings 19 and their distance 52 from the head 50 of the rib 16, s. Fig.6, as well as the distance 43 of the cross rib openings 19. When tuning the Ribbed field to the requirements based on the set Thickness 34 of the outer wall 4 can have the above dimensions, distances and spatial arrangements changed within certain limits become. The limits are determined on the one hand by that good cooling must be maintained, on the other hand Adequate stability in accordance with the heat transfer coefficients locally formed with a small thickness Outside wall 4 may be given. For the latter it is necessary that Arrange ribs 16 closer, on the other hand they must not be tight so that the cooling fluid 6 is not just over it flows away and may not be swirled. The Height 41 of the ribs 16 is approximately one to two times the outer wall thickness 34. The load-bearing width 38 of the ribs 16 is approximately four times the thickness 34 of the outer wall 4. In the areas of the leading edge 32 are preferably no ribs or conventional Turbulators as well as in the rear edge area 36.

6 shows an exemplary arrangement of cross rib openings 19. They have an elongated oval shape. They effect a cross exchange and a swirl of the flowing past Cooling fluid 6, but arranged so spaced are that they do not affect the stability of the ribs 16, to stabilize the thin outer wall areas 14 serve.

7 shows a section through an airfoil area 7 of a medium-pressure-steam-cooled turbine guide vane 1 with a varying outer wall thickness 34. The cavity 5 surrounded by the outer wall 4 has six cooling chambers 21, two front cooling chambers 31 in the region of the leading edge 32 and a rear cooling chamber 53 in the rear edge region 36 six middle cooling chambers 21 are separated from one another by inner walls 20. The central cooling chambers 21 have approximately the same flow cross sections. The cooling steam 6 flows through them in series according to a flow diagram shown in FIG. The wall thickness 8 of the metal wall 3 varies over the circumference from approximately 1 to 2.2 mm, according to the same principle as already described for the low-pressure steam-cooled turbine guide vane, ie to compensate for the heat transfer coefficients W _ex , W _int that change over the cross section of the airfoil 7. The transitions between areas 14 of different wall thicknesses 8 are each continuous, corresponding to areas 10, that is to say continuous, preferably linear or interpolated by means of other functions.

The turbine blade 1 has rib fields on the entire inside 13 of the outer wall 4, with the exception of the trailing edge region 36, which serve to support the thinned outer wall 4. The medium pressure steam is almost twice as large as the low pressure steam (approximately 30 bar compared to approximately 15 bar). Thus, the internal pressure load on the outer wall 4 is much stronger and additional rib fields are required. However, it is advantageous that the medium-pressure steam ensures improved heat dissipation and thus more favorable internal heat transfer coefficients W _int . The ribs 16 again have predetermined distances and dimensions and are equipped with cross-flow openings 19. The ribs 16 are essentially transverse to the flow direction 18, which is parallel to the radial axis of the airfoil 7.

The cooling mass flow can be adjusted by adding or omitting flow resistances 51, which are only indicated schematically in FIG. 4, in such a way that a desired cooling flow and an internal heat transfer or heat transfer coefficient W _int occurs, which is adapted to the varying wall thickness 34 of the outer wall 4 is.

8 shows a top view of a foot region 26 of a medium-pressure steam-cooled Turbine blade from Figure 7 with a Inlet 27 and an outlet 28 for the cooling fluid 6.

9 shows a longitudinal section of a medium-pressure steam-cooled Turbine blade according to Figure 7 with a foot 26, one Airfoil 7 and a head region 25 and a flow diagram of the medium pressure cooling steam. The middle cooling chambers 21 are serial and the front 31 and the rear cooling chamber partially flows in parallel from the cooling fluid 6. The foot 26 and the Head area 25 are welded to the airfoil area 7 or soldered. They are closed by a Circuit cooled with the same cooling fluid 6 as the airfoil area 7. This reduces the amount of coolant required and simplifies the construction of the cavity 5 respectively the interiors of the head 25 and foot areas 26.

10 shows a schematic drawing of the coolant flow through a medium-pressure steam-cooled turbine blade from Fig. 7. In The inlet area 27 can have different flow resistances 51 are placed in different cooling chambers 21, so that the partial mass flows of the cooling fluid 6 can be adjusted. An enlarged mass flow causes an enlarged one Cooling effect, but also increased pressure drops.

11 shows a schematic drawing of a medium-pressure steam-cooled Turbine guide vane. The cavity 5 has five Partial cooling chambers 21, the front region 32 two front cooling chambers 31 and the rear area 36 a rear cooling chamber 53 on. The central cooling chambers 21 have approximately the same flow cross sections, the wall thickness 8 of the outer wall 4 is almost constant. Due to the sufficient stiffening by the Inner walls 20 do not require ribs 16.

12 shows a flow diagram of the turbine blade from FIG. 11.

Claims (27)

Turbine blade (1), in particular gas turbine blade, which has an outer wall (4) against which a hot action fluid (2) flows, which surrounds a possibly multi-part cavity (5) through which a cooling fluid (6) flows, the outer wall (4) the thickness of the blade area (7) of the turbine blade (1) is different,
characterized in that the thickness (34) of the outer wall (4) at least over a partial circumference of the airfoil area (7) in accordance with the course of the external heat transfer coefficient (W _ex ) on the outside (9) of the outer wall (4) and the course of the internal Heat transfer coefficient (W _int ) on the inside (13) of the outer wall (4) runs continuously such that predetermined temperature threshold values (T _M ) on the outer wall (4) and / or predetermined temperature gradients (ΔT _M ) over the outer wall (4) between predetermined Positions of the outer wall (4) must not be exceeded. Turbine blade according to claim 1
characterized in that the outer wall (4) has a multilayer structure and has a thin ceramic protective layer (15) on the outside of the outer wall (4) and a metal wall (3) on the inside, and that the temperature gradient (ΔT _M ) that is between the outside is decisive (11) and the inside (12) of the metal wall (3). Turbine blade according to one of claims 1 to 3
characterized in that the temperature threshold (T _M ) on the entire outer wall (4) and / or predetermined temperature gradients (ΔT _M ) over the entire outer wall (4) are not exceeded. Turbine blade according to one of claims 1 to 4
characterized in that the temperature threshold value (T _M ) and the temperature gradient (ΔT _M ) correspond to critical, material and voltage-dependent values. Turbine blade according to claim 3 or 4
characterized in that the outer wall is single-layer and consists of metal. Turbine blade according to one of claims 1 to 5,
characterized in that a field of ribs (16) is provided in the cavity (5) where there is an outer wall region (14) of reduced thickness (34). Turbine blade according to claim 6
characterized in that the ribs (16) of the field in accordance with the thickness (34) of the outer wall (4), the temperature threshold (T _M ) and / or the temperature gradient (ΔT _M ) and the dimensions, distances and have spatial arrangements. Turbine blade according to claim 6 or 7,
characterized in that the field of the ribs (16) extends at least in sections transversely to the flow (18) of the cooling fluid (6). Turbine blade according to one of claims 6 to 8,
characterized in that the ribs (16) have transverse openings (19). Turbine blade according to one of claims 1 to 9,
characterized in that the cavity (5) from the pressure side (46) to the suction side (45) in the longitudinal direction of the turbine blade (1) is traversed by inner walls (20), the inner walls (20) being connected to the pressure-side or suction-side outer wall (4 ) are continuously connected to the continuous course of the thickness (34) of the outer wall (4). Turbine blade according to one of claims 1 to 10,
characterized in that the cavity (5) is provided with an aluminizing layer (54). Turbine blade according to one of claims 1 to 11,
characterized in that the cooling fluid (6) is guided in a closed circuit through the turbine blade (1). Turbine blade according to one of claims 1 to 12,
characterized in that the inlet (27) and the outlet (28) of the cooling fluid (6) are arranged in the foot region (26). Turbine blade according to one of claims 1 to 13,
characterized in that the top (25) and foot region (26) of the turbine blade (1) is cooled at the same time as the cooling fluid (6) of the blade area (7). Turbine blade according to one of claims 1 to 14,
characterized in that the turbine blade (1) is a moving blade and the wall thicknesses (30) of the inner walls (20) in the cavity (5) vary locally in accordance with a local heat transfer coefficient. Turbine blade according to one of claims 1 to 15,
characterized in that central cooling chambers (21) formed by inner walls (20) and through which cooling fluid (6) flows are provided in the central region (55) of the airfoil region (7). Turbine blade according to one of claims 1 to 15,
characterized in that central cooling chambers (21) formed by inner walls (20) and through which the cooling fluid (6) flows in parallel are provided in the central region (55) of the airfoil region (7). Turbine blade according to claim 16 or 17,
characterized in that at least one of the central cooling chambers (21) has an impingement cooling insert (22) with outward impinging cooling bores (23) which are arranged at a distance from the inside (13) of the outer wall (4) and through which the cooling fluid (6) flows . Turbine blade according to claim 18,
characterized in that the impact cooling insert (22) is held on the inside (13) of the outer wall (4) and / or on the inner wall (20) and / or on spacers (44) attached to ribs (16). Turbine blade according to one of claims 1 to 19,
characterized in that additional cooling (56) is provided on the rear edge (36) of the turbine blade (1). Turbine blade according to claim 20,
characterized in that the additional cooling (56) is a separate, closed steam cooling. Turbine blade according to claim 20
characterized in that the additional cooling (56) is air cooling with a free outlet. Turbine blade according to one of claims 1 to 22,
characterized in that the cooling fluid (6) is steam. Turbine blade according to claim 23
characterized in that the steam is a low pressure steam. Turbine blade according to claim 23
characterized in that the steam is a medium pressure steam. Turbine blade according to one of claims 1 to 25,
characterized in that the outer contour of the turbine blade (1) corresponds to the shape of an aerodynamically predetermined shape and that the thickness (34) of the outer wall (4) varies towards the cavity (5). A method for producing a turbine blade, in particular a gas turbine blade, with an outer wall (4) which has different thicknesses along a cross section through the blade area (7) of the turbine blade (1), and with the further features of one of claims 1 to 26, wherein the A method comprises a casting process, in which a casting mold containing a casting core is used for producing a turbine blade according to the features of one of claims 1 to 26,
characterized in that the casting mold is arranged in such a way that the profile profile of the outer contour of the casting core corresponds to the difference between an aerodynamically predetermined external profile profile of a turbine airfoil (7) and a function which corresponds to the profile of the external heat transfer coefficient (W _ex ) on the outside (9) the outer wall (4) of the turbine blade (1) and the course of the internal heat transfer coefficient (W _int ) on the inside (13) of the outer wall (4) of the turbine blade (1) so that at least at predetermined locations on the outer wall (4) predetermined temperature threshold values (T _M ) and / or predetermined temperature gradients (ΔT _M ) are not exceeded.

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