第三组5-专利全文外文ep2426316

1、&(19)EP 2 426 316 A1(11)EUROPEAN PATENT APPLICATION(12)(43) Date of publication:07.03.2012 Bulletin 2012/10(51) Int Cl.:F01D 5/18 (2006.01)(21) Application number: 10175230.1(22) Date of filing: 03.09.2010(54)Turbine blade(57)The invention relates to a turbine blade (1) for a(37), wherein the cavity

2、 (37) is covered by said airfoil tip shelf (17), which is separately manufactured from the airfoil main body (12). In order to specify a turbine blade, in which improved cooling of the airfoil tip is provided and which is especially simple to produce for saving both time and costs, it is suggested t

3、hat the suction side wall (14) and the pressure side wall (16) of the airfoil main body(12) both having a wall thickness (63) along its span di- rection, which in tip region (27) is constant.gas turbine, comprising one after the other along a blade axis (11) towards a turbine blade tip (29), a platf

4、orm re- gion (13) and a airfoil (15) attached to said platform re- gion, the airfoil (15) comprising an airfoil main body (12) and an airfoil tip shelf (17), the airfoil main body (12) comprises integrally formed a suction side wall (14) and a pressure side wall (16) bordering at least one cavityPri

5、nted by Jouve, 75001 PARIS (FR)EP 2 426 316 A1(84) Designated Contracting States:AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK SM TRDesignated Extension States:BA ME RS(71) Applicant: Siemens Aktiengesellschaft 80333 Mnchen (DE)(72) Inventor

6、s: Bolms, Hans-Thomas45481, Mlheim an der Ruhr (DE) Marra, John J.Winter Springs, FL, 32708 (US)1EP 2 426 316 A12Descriptioning-air opening and a cooling-air outlet are connected to the hollow profile around this shroud. Furthermore, the shroud is deformed and has a narrow central section, such that

7、 this shroud becomes a lightweight shroud. In a similar manner, a multiplicity of shroud cooling open- ings are formed parallel to one another in such a way that a form is provided which enables the cooling air to be discharged outwards from the cooling-air outlet. 0006Furthermore, US 6,164,914 show

8、s a turbine blade having a squealer tip.0007 It is also known to intensively cool a moving airfoil tip by holes being provided in the hollow profile of the airfoil tip itself in order to cool an airfoil tip shelf in the course of film cooling. In this case, a cooling fluid is forced out of the holes

9、 and settles in the form of a film on the outer surface of the hollow profile in a cooling manner. There is the problem in the abovementioned turbine blades that, on the one hand, the cooling of an airfoil tip can be arranged even more efficiently, but that, on the other hand, the cooling design of

10、an airfoil tip, compared with the airfoil, is too complex for it to be produced ad- vantageously from the manufacturing technology point of view.0008To increase the output and the overall efficiency of a gas turbine, a turbine blade in which the use of cooling medium can be arranged as efficiently a

11、s possible and which is also easier to produce would be desirable. 0009This is where the invention comes in, the object of which is to specify a turbine blade, in which improved cooling of the airfoil tip is provided and which is especially simple to produce for saving both time and costs. 0010The o

12、bject is achieved by the invention by means of the turbine blade mentioned at the beginning, in which, according to the invention, the suction side wall of the airfoil main body and the pressure side wall of the airfoil main body both having a wall thickness along its span direction, which is in its

13、 tip region almost constant. In other words: the airfoil main body does not have at its tip region any projections extending transversely to the side walls.0011 The invention is based on the knowledge, that the casting of the turbine blade or at least of its airfoil main body can be improved, if the

14、 outer end of the airfoil main body - the tip region - do not have any projections extending perpendicular to the pressure side wall and suction side wall. Due to the avoidance of the projections, the section side wall and the pressure side wall both hav- ing a wall thickness along its span directio

15、n, which in tip region is almost constant. This avoids an outer opening of the airfoil main body having a bottle neck - the outer opening of the airfoil main body is large as possible. Such an airfoil main body or a turbine blade having such an airfoil main body can be cast more easily with respect

16、to precision, time and costs. Because of the big outer open- ing - also known as a core exit hole - in the blade tip region especially control of wall thickness and core po- sition can be improved significantly.0012 The airfoil tip shelf is a cast and/or machine part0001 The invention relates to a t

17、urbine blade com- prising a root region for attaching the turbine blade to a carrier, a platform region and an airfoil attached to said platform region, the airfoil comprising integrally formed a suction side wall and a pressure side wall extending from a common leading edge to a trailing edge and t

18、rans- versely from said platform region to a tip region bordering at least one cavity, wherein the cavity is covered by an airfoil tip shelf.0002 In a gas turbine temperatures within the range of between 1000C and 1800C can occur in the flow duct when a working fluid in the form of hot gas is admitt

19、ed to said gas turbine. Turbine blades which are exposed to the working fluid in order to absorb the kinetic energy of the latter are to be designed with regard to such loads. A turbine blade may be designed in the form of a moving blade fastened to a rotor. Furthermore, a turbine blade may be desig

20、ned in the form of a guide blade firmly at- tached to the casing of a turbine. Equally, in both blade types, in particular the tip of the turbine blade is subjected to high thermal loads. In a moving blade, there is also the high mechanical load caused by the rotary move- ment.5101520250003The exter

21、nal contour of the airfoil tip shelf isprimarily determined by an aerodynamic definition of the object. Furthermore, technical considerations relating to production are an important factor with regard to the shaping. In addition, a cooling design is relevant to the further development of a turbine b

22、lade, and in this case in particular the airfoil tip, as a result of the high thermal loads. This is because the tip must be cooled in order to achieve a long service life. Without cooling of the airfoil tip, it would rapidly oxidize. Nonetheless, the service-life requirements imposed on guide blade

23、s and in particular on moving blades are constantly increasing. That is to say that the component temperature must be kept within readily acceptable limits through the use of a cooling fluid. In addition, in the cooling design of a turbine blade, in particular of a moving blade, in which in particul

24、ar the design of the airfoil tip is relevant, the use of cooling fluid must be arranged efficiently in order to increase the over- all efficiency and the output of a gas turbine.0004 To cool a turbine blade and in particular an airfoil tip, a number of measures have been proposed. To cool an airfoil

25、 in the form of a hollow profile, US 4,519,745 recommends a corrugated partition of the inner wall of the hollow profile. To cool an airfoil tip, a multiplicity of passages and an aperture in a bearing surface are pro- vided for the airfoil tip, such that the airfoil tip can be cooled from outside w

26、ith a cooling fluid transported via the passages and the aperture.0005 DE 198 131 15 A1 discloses a cooled turbine blade of a gas turbine, the airfoil of which has a multiplicity of webs in the hollow profile, these webs serving as swirl elements. Furthermore, a shroud or blade-stiffening band is ar

27、ranged on the end of the turbine blade. A cool-30354045505523EP 2 426 316 A14preferable from the same base material like the airfoil main body or the turbine blade. The bonding surfaces of the airfoil main body and the airfoil tip shelf are machined to allow a sufficient bonding and to stand up the

28、thermal as well mechanical loadings.0013 The casting process for manufacturing the air- foil main body (itself or as a part of a turbine blade main body) is improved due to the totally open design of the tip region.0014 After bonding both parts the airfoil main body and the airfoil tip shelf, the wh

29、ole airfoil surface will be finished to prepare for metallic and/or ceramic oxidation and thermal protection coatings.0015 The main advantage is the decreased complex- ity of casting, which improves the precision of the cast turbine blade with regard to wall thickness. The scrap rate can be lowered,

30、 which save time and costs. Further- more, the free arrangement of film cooling holes in the airfoil tip shelf using established bonding technologies improves the service-lifetime. Also an efficient tip cooling can be applied due to an easy access of the cavity. This can lead to a reduced thermal lo

31、ading and less mass at the airfoil tip. The latter is mostly reached due to the avoid- ance of said perpendicular projections.0016 Advanced developments of the invention can be gathered from the sub claims and specify in detail advantage possibilities for configuring the turbine blade with regard to

32、 the cooling of the airfoil tip shelf with the whole series of further advantages over hitherto conven- tional measures.0017In the first preferred embodiment the airfoil tip shelf comprises a shelf bottom, projections extending transversely from the shelf bottom and parallel to the side walls into t

33、he cavity and an impingement cooling plate spaced apart from said shelf bottom by said projections attached to the shelf bottom. The Projections arranged on the cold side of the shelf bottom acting as distance elements which will prevent buckling of the impingement cooling plate due to the centrifug

34、al force. The shelf bot- tom is cooled by impingement cooling air which is flowing through the impingement cooling openings arranged in the impingement cooling blade to the hot shelf bottom. 0018In another preferred embodiment the airfoil tip shelf is joined to the airfoil main body, the airfoil mai

35、n body and the airfoil tip shelf being brazed or welded in place.0019 According to an advantageous development of the invention the airfoil tip shelf comprises at least one squealer tip extending outwardly from the shelf bottom. In a preferred embodiment the squealer tip has a wall thickness thinner

36、 than the thickness of the pressure side wall or/and suction side wall. This leads to a reduced centrifugal loading in comparison to conventional one- piece-casted airfoils.0020 Using an impingement cooling plate has the ad- vantage that the mass of the airfoil tip shelf can be kept as small as poss

37、ible. Furthermore, it is possible to pro- duce the airfoil and the airfoil tip shelf from different ma-terials or same materials in order to be able to realize at the same time special advantages, such as, for example, low weight or high thermal conductivity of the airfoil tip shelf or, for example,

38、 high strength of the airfoil.0021 In a further preferred embodiment the airfoil tip shelf and/or the tip region of the airfoil main body contain a number of cooling openings. The cooling openings are advantageously formed and/or arranged as film cooling openings, which, in cooling fluid is admitted

39、 to the turbine blade, enable a film of cooling fluid to be produced on the outer surface of the turbine blade. This allows addi- tional cooling of thermal high loaded areas. The arrange- ment of the film cooling holes is very flexible, since the holes can be drilled from both the hot side as well a

40、s cold side of the shelf.51015Fig. 1shows a schematic illustration of a turbine blade, to which cooling fluid is admitted, on a rotor of a gas turbine,20Fig. 2shows in a perspective sectional view a turbine blade having an airfoil main body and an airfoil tip shelf according to the preferred embodim

41、ent of the invention.250022Figure 1 shows a turbine blade 1 fastened to arotor 3 of a gas turbine (not described in any more detail). The turbine blade 1 in this case is one of a number of moving blades which are arranged in an annular manner extend radially in a flow duct 5 of the gas turbine and w

42、hich in their entirety form a blade ring which extends into the annular cross section of the flow duct 5. A mul- tiplicity of such annular blade rings are arranged along an axis 7 of the gas turbine (not described in any more detail) in the same way as the flow duct. A working fluid 9 in the form of

43、 a hot-gas mixture is admitted to the flow duct 5 and this hot-gas mixture expands, with the turbine blade 1 being driven, and thus delivers its kinetic energy, with the rotor rotating for driving a generator (not de- scribed in any more detail).0023 The turbine blade 1 has - along a blade axis 11 a

44、rranged one after the other towards a turbine blade tip 29 - at least a platform region 13 and an airfoil 15. The airfoil 15 comprises an airfoil main body 12 arranged in the form of a hollow profile and an airfoil tip shelf 17 also arranged in the form of a hollow profile. The platform region 13 su

45、rrounds a blade platform for delimiting the flow duct 5 and a blade root, which are not shown in detail. The airfoil 15 comprises a suction side wall 14 and a pressure side wall 16 (FIG 2). Both suction side wall 14 and pressure side wall 16 extend from a common leading edge 18 to a trailing edge 20

46、 while surrounding a cavity 22 containing a passage system 19. As indicated schematically, a cooling fluid 21 can be admitted to the turbine blade 1 via a passage system 19.0024 The cooling of the turbine blade 1 also extends in this case in particular to the airfoil main body 12 and the airfoil tip

47、 shelf 17.30354045505535EP 2 426 316 A160025 Figure 2 shows in a perspective sectional view the embodiment according to the invention with regard to a tip region 27 of the turbine blade 1.0026 Whereas the concept of the invention explained above proves to be especially useful for the embodiments of

48、a turbine blade 1 shown here, it should nonetheless be clear that the concept described can be equally real- ized within the scope of a turbine blade 1 of a gas or steam turbine and independently from their internal de- sign of airfoil cooling.0027 The airfoil main body 12 and the airfoil tip shelf

49、17 being produced separately. The airfoil main body 12 is usually produced by casting and designed as a hollow profile. The airfoil tip shelf 17 is - with regard to its cross- section - designed with shelf bottom 31, shoulders 33, spacers 34 and an impingement cooling plate 35. The shoulders 33 and

50、spacers 34 are projections extending transversely from the shelf bottom 31 into the cavity 22. The impingement cooling plate 35 is spaced apart from the shelf bottom 31 by said shoulders 33 and spacers34. The impingement cooling plate 35 is fixed to the shoulders 33 located close to the side walls 1

51、4, 16. The spacers 34 located between the shoulders 33 prevent buckling of the impingement cooling plate 35 due to cen- trifugal forces occurring during operation of the turbine blade 1.0028 The hollow profile of the airfoil 15 contains the cavity 22 and the airfoil tip shelf 17 has a another cavity

52、 37, which both are part of the cooling system 19 shown in Figure 1 and to which cooling fluid can be admitted. On its side facing the turbine blade tip 29, shown in Figure 1, the airfoil main body 12 has in its tip region 27 - in contrast to the turbine blade known from prior art - no wall running

53、transversely to the blade axis 11. In other words: both the suction side wall 14 and the pressure side wall 16 having a wall thickness t along their span direction 11, which is also in the tip region 27 of the airfoil main body 12 almost constant. Hence, there exists no bottle neck between the sucti

54、on side wall 14 and the pres- sure side wall 16 due to any casted perpendicular wall extensions.0029 The impingement cooling plate 35 and the shelf bottom 31 are opposite to one another forming a raised floor 45. By this raised floor 45 the other cavity 37 is formed between the impingement cooling p

55、late 35 and the shelf bottom 31, which both extend horizontally over the entire cross section of the hollow airfoil main body12. This leads to a reduced mass in comparison to known turbine blades, which having impingement cooling plates being at least partially casted together with the airfoil main

56、body.0030 The thickness of the shelf bottom 31 is larger than the thickness of the impingement cooling plate, since the shelf bottom 31 has not only the objection to cover the cavity 22. Besides this, the shelf bottom 31 shall also enhance the mechanical rigidity of the airfoil15. Due to this, the s

57、helf bottom 31 is firmly connected by bonding, welding or brazing to the airfoil main body12 directly and not via the impingement cooling plate 35. 0031The raised floor 45 has cooling means, which are explained in detail below. In particular, impingement- cooling openings 43 are arranged in the impi

58、ngement cooling plate 35. In addition, the impingement cooling plate 35 is arranged so close to the shelf bottom 31 that an appropriately pressurized cooling medium impinges on the shelf bottom 31 via the impingement-cooling open- ings 43 and effectively cools the airfoil tip shelf 17 in the course

59、of impingement cooling. This impingement cool- ing explained could be intensified further by swirl ele- ments (not shown) in the form of nipples and/or dimples arranged on the inner surface of the shelf bottom 31. That is to say that heat absorbed in the airfoil tip shelf is ef- fectively dissipated by the