Gas turbine blade with modular structure

p0001The invention relates to a gas turbine blade according to the preamble of claim 1.

p0002In detail, the invention relates to a gas turbine blade having an airfoil, which is radially on the outside provided with a shroud and is radially inwardly secured to a platform. The platform in turn is connected via a shaft (lying inside load carrier) 6 is provided with a foot and anchored to a plate, so as in the prior art.

p0003The prior art is applied to the two <patcit id="pcit0001" dnum="US20060120869A1"><text>US 2006/0120869 A1</text></patcit> and the <patcit id="pcit0002" dnum="US7080971B2"><text>US 7,080,971 B2</text></patcit> referenced.

p0004Most gas turbine rotor blades are nowadays made of forgings or investment casting.

p0005Compressor blades are typically made from forgings and have thin, radially packed sections.

p0006Turbine blades are typically made complicated fine fonts (<figref idrefs="f0001">Fig. 1</figref>) Prepared using a Wachsaufschmelz-casting process. This is very time-consuming and costly.

p0007To cope with a creep and the harmful effects of the environment of hot gas turbine blades have radially packed and thicker cross-sections as compressor blades. They contain cool air discharge holes (cooling of the surface layer and of the outlet edges emissions) which require additional internally cast cooling air supply passages. The pressure difference is always positive, so that cooling air exits into the gas path always outwards.

p0008Turbine blades are typically manufactured as coaxial, aligned solidified or single crystal castings. These cast parts are then finished by machining and polishing of the airfoil surfaces in order to obtain a high degree of surface treatment. To avoid oxidation and sulfidation, the blades are finally coated with a thin and expensive aluminized coating.

p0009Since turbine blades are subjected to very high mechanical speeds (and therefore large CF forces / centrifugal) (<figref idrefs="f0002">FIG. 2</figref>are exposed) and a Hot chemically aggressive environment, the blades suffer from a certain degree of creep and deterioration.

p0010The lost-wax casting method is a manual, time-consuming and labor-intensive production methods, which sometimes leads to defects, such as shrinkage, particularly if internal cooling passages are affected.

p0011In addition to make restrictions in the production sometimes an optimized design of internal cooling passages impossible.

p0012To support the very large centrifugal forces (CF-train), experienced by the blades due to the high speed rotation, the sidewall wing of the blades must be quite thick in cross-section, whereby the weight is increased and the CF-train to the Tannenbaum roots of the blades is increased due to the increased weight of the blade.

p0013The disadvantages of this conventional design process are as follows:<ul><li>Need to establish a single casting with the only material that offers the best solution in terms of creep, but a compromise is with regard to other performance requirements on the blade.</li><li>The wing-shaped surface serves as both a centrifugal load carrier as well as the aerodynamic load carrier. These conflicting requirements may jeopardize the aerodynamic optimization of the side panels.</li><li>The one-piece construction leads to problems and limitations with regard to blade repair. Frequent problem areas in turbine blades are burnout of the thin trailing edge about the center span, the same problem also occurs at the leading edge, albeit rare, and sulfidation of the aerodynamic surfaces.</li></ul>

p0014The invention is based is to provide a gas turbine blade of the type mentioned, which the disadvantages of the prior art avoids a simple structure and simple, cost-effective producibility the task.

p0015According to the invention the object is achieved by the feature combination of claim 1, the subclaims show further advantageous embodiments of the invention.

p0016The invention thus relates to a novel design and a new manufacturing method for the turbine blades.

p0017The invention is characterized in that turbine blades are designed and manufactured from separate modular parts, which are then combined subsequently to form a complete turbine blade assembly.

p0018This modular design principle may be used for blades for blowers and compressors. The biggest advantage in terms of cost, performance and production is being achieved in the turbine blade design.

p0019The advantage is that optimizes each modular part to fulfill its role and function in that the optimal material is selected for this purpose. This offers advantages over a monolithic blade assembly, in which the selection of a single material has to withstand various loads, a spectrum must cover at contradictory functions and is exposed to various potential failure mechanisms.

p0020The centrifugal force-tension load due to the rotational speed is carried by a radially arranged, central and / or disposed between the inner and outer platform module shank module. This central shaft module is located in the interior of the airfoil-shaped bushing module and is externally cooled by cooling air in the vane cavity around the central shaft (lying inside load carrier) flows 6th

p0021The aerodynamic loads are carried by an internally cooled, airfoil-shaped bushing module. The bush is subject to aerodynamic loads as well as a compressive Zentrifugalkraftlast due to its own weight and the sliding Innenendaufbau. However, these compressive loads are typically only 10% of the centrifugal force-tensile loads. The expansion of the liner due to the temperature is similar to the contraction of due to the centrifugal-tensile loads.

p0022In the following the invention will be described with reference to embodiments in conjunction with the drawing. In which:<dl id="dl0001"><dt>Fig. 1</dt><dd>a perspective, schematic illustration of a gas turbine blade according to the prior art,</dd><dt>FIG. 2</dt><dd>a representation of the loads occurring a gas turbine blade,</dd><dt>Fig. 3A</dt><dd>a first embodiment of a gas turbine blade according to the invention in exploded view with assignment of the manufacturing steps,</dd><dt>Fig. 3B</dt><dd>a second embodiment, analog <figref idrefs="f0003">Fig. 3A</figref>.</dd><dt>Fig. 3C</dt><dd>a further embodiment of a gas turbine blade according to the invention, analogously to <figref idrefs="f0003">FIGS. 3A</figref> and <figref idrefs="f0004">3B</figref>.</dd><dt>Fig. 3D</dt><dd>a further embodiment of a gas turbine blade according to the invention, and</dd><dt>Fig. 4</dt><dd>a sectional view of a fully assembled embodiment of a gas turbine blade according to the invention.</dd></dl>

p0023In the following embodiments, the same parts are provided with the same reference numerals.

p0024The <figref idrefs="f0001">Fig. 1</figref> shows a perspective view of a gas turbine blade according to the prior art. This comprises a shroud 1, a blade 2, a platform 3, a shank 4 and a foot 5, which is designed as a fir-tree root.

p0025The <figref idrefs="f0002">FIG. 2</figref> shows occurring loads of a gas turbine blade according to the prior art. A gas loading 21 (large arrow) results in a moment arm 22 for the gas load. With a rotation about a machine axis 23 results in a centrifugal force 24, which is associated with a centrifugal force-moment arm 25th Numeral 26 designates a centrifugal-force couple, a gas power-couple of forces is indicated by 27th Numeral 28 shows a it seeks to clamping of the blade root. 5

p0026Four different embodiments of the gas turbine blade according to the invention are in the <figref idrefs="f0003">FIGS. 3A</figref>. <figref idrefs="f0004">3B</figref>. <figref idrefs="f0005">3C</figref> and <figref idrefs="f0006">3D</figref> shown.

p0027The construction of the invention in <figref idrefs="f0003">Fig. 3A</figref> has the following components:<ul><li>It 6 is provided with integral firtree 5 a radially disposed, central shaft (internal load carrier). The central shaft (internal load carrier) 6 transmits the CF-traction from the Christmas tree attachment to the outer tip of the airfoil. 2</li><li>The shaft (internal load carrier) 6 is made of a twisted strand fiber of carbon nanotube (CNT). Twisted CNT-strand fibers have a much higher load capacity than high-strength steel fibers of the same diameter and can also be very hot environments endure (if they are not impregnated with a bonding matrix). The flexible CNT fiber shank (internal load carrier) 6 is inserted into the upper platform and conical ceramic end fittings in the fir-tree. These prevent the same time a separation of fibers.</li><li>Furthermore, a one-piece, airfoil-shaped sheet member 8 (bush) is provided, which replaces the conventional airfoil of the airfoil 2 and has the aerodynamic surface for the gas loads. The compressive loads on the blade member 8 (box) itself only arise due to the mechanical CF-loads of their own construction.</li><li>The outer platform 10 is a single part and is the radial shaft (lying inside porters) 6 connected radially inward. The aerodynamic blade member 8 is in the outer platform 10 (bearing block) to the groove 11 in the inner platform 3, plugged into an airfoil-shaped groove 9, similarly. The CNT-shaft (internal load carrier) 6 is inserted into the upper outer platform 10th</li><li>An inner platform 3 is covered with a thin groove 11 is inserted with large wing aspect, in which the wing box (blade member 8). The lower end of the wing box (blade member 8) is inserted into this groove 11 having the shock absorber projections to limit the wing box (blade member 8) side, and a vibration at its lower end (which is a free end substantially) to prevent. However, the shock absorber projections allow a sliding movement in the radial direction. For ease of manufacture and assembly, the inner platform 3 is formed as a split element that is divided into a right and a left part. The inner platform is screwed together and connected to the central shaft (lying inside porters) 6 securely connected to form a complete blade assembly.</li><li>A small amount of radial play in the sheet member 8 is allowed due to thermal expansion. The sheet member 8 and the Plattformnuten 9, 11 turn the original blade stability when the turbine is stationary (not rotating).</li><li>Once the turbine begins to rotate, the CF-tensile load of the CNT-shaft (lying inside load carrier) is added 6.</li></ul>

p0028The construction according to <figref idrefs="f0006">Fig. 3D</figref> consisting of:<ul><li>This construction is the same as described above for <figref idrefs="f0005">Fig. 3C</figref> , except that the fir-tree is 5 now replaced by a dovetail. The central shaft (internal load carrier) 6 transmits the CF-tensile load from the dovetail attachment to the outer tip of the blade.</li><li>The dovetail construction is easier to manufacture than the Tannebaumfuß design and can provide the best solution as modular turbine blades according to the invention are lighter than the currently conventional constructions. A heavier part undergoes a stronger CF train and requires a fir-tree root attachment to distribute the load evenly.</li></ul>

p0029The <figref idrefs="f0003 f0004 f0005 f0006">FIGS. 3A to 3D</figref> each show with A to F provided arrows illustrating the producible step:

p0030According to <figref idrefs="f0003">Fig. 3A</figref> it is provided that in steps A and B the inner halves of the platform 3 are joined together so that grooves 12 engage a socket 13 of the foot fifth In step C there is a locking, in step D the aerodynamic blade member 8 is inserted into the grooves 11 of the inner platform third In step E, the outer platform 10 is attached, so that the sheet member 8 is inserted into the groove 9 and a radially outer base 15 of the inboard load carrier 6 is inserted in a recess 14 of the outer platform 10th Subsequently, in step F, a sealer.

p0031The assembly method according to <figref idrefs="f0004">Fig. 3B</figref> in the same way.

p0032In the assembly method according to <figref idrefs="f0005">FIGS. 3C</figref> and <figref idrefs="f0006">3D</figref> is in addition a recess 16 is provided in the base 13, in which the base 17 of the inboard load carrier 6 is inserted. All other production steps are carried out analogously.

p0033The <figref idrefs="f0007">Fig. 4</figref> shows an assembly drawing of an embodiment of a gas turbine blade according to the invention.

p0034Advantages of the inventive construction:<ul><li>The modular design allows to tune the material properties and the production of exact location requirements.</li><li>The central shaft (internal load carrier) 6 (<figref idrefs="f0003">Fig. 3A</figref> and <figref idrefs="f0004">3B</figref>) Can be made of a rod-forging or similar material with optimized tensile strength.</li><li>Alternatively, the central shaft (internal load carrier) can be 6 made in two parts: one part fir-tree or dovetail from a forged alloy plus a part of a progressive material such as twisted strand fiber of carbon nanotube (CNT). wearing The central shaft (internal load carrier) 6, the platforms 3, 10 and the wing-shaped bush (sheet member 8) is much easier and reduces the overall CF-load on the blade 5. Twisted strand fibers of CNT have a much higher load capacity as high-strength steel fibers of the same diameter and can be very hot environments endure (if they are not impregnated with a bonding matrix).</li><li>The constructions of the invention may be easier, thereby eliminating the need for a heavier and more expensive fir-tree-structure is removed. A dovetail construction may be sufficient.</li><li>Since the airfoil-shaped bush (sheet member 8) does not have to be made of a single crystal casting, the right material (eg a Nimonic alloy, a ceramic metal, etc.) can be used to obtain the best properties and a resistance to sulfidation.</li><li>The new airfoil shaped bushes (leaf element 8) can be tested more quickly and cheaply than conventional blades, simply by changing the wing-shaped bush (sheet member 8) is replaced.</li><li>Since the new constructions are lighter, the Versetzwinkel the blade roots may be almost parallel to the motor axis, whereby a load of Fußecken is eliminated. Thus, thinner, lighter discs are possible.</li><li>The demands on the cooling can be reduced, so that less cooling air is required.</li></ul>

Advantages in the production:

p0035<ul><li>The shaft (internal load carrier 6) can be produced from a one-piece forged part. Operations: rotating the cylindrical shank (internal load carrier 6) (if cylindrical), incision of the Tannenbaum foot, milling of surfaces on the cylindrical shaft (internal load carrier 6) for indoor and outdoor platform attachment points.</li></ul>

p0036Alternatively, the stem (internal load carrier 6) are produced as a separate part of twisted CNT-strand fibers.<ul><li>Indoor and outdoor platforms: casting or forging and machining by milling. The groove can be produced by spark erosion machining.</li><li>Airfoil shaped bush (sheet member 8): can be molded as one piece super elastic or as a left and a right part are rolled into shape and then the two halves are welded together.</li><li>No Sulfidierungsbeschichtung required on the blades.</li><li>No need for a sheet outlet between the airfoil-shaped bush (sheet member 8) and the indoor and outdoor platforms.</li></ul>

Advantages during repair

p0037In addition to the design according to the invention and the preparation according to the invention, the invention is advantageous with respect to the repair of damaged blade surfaces.<ul><li>Engine turbine blades of gas turbines are often damaged at the leading edges and trailing edges of the wings, due to the extremely hard and aggressive operating room environment. The modular construction method allows each damaged module can be replaced separately, so that a repaired vane assembly is "like new" generated.</li><li>For example (inside or outside), a damaged wing-box (sheet member 8) or platform (10 3) to be replaced quickly and easily, without the expensive part of the blade, which in this case, the central shaft (internal load carrier) 6 and Turbinenscheibenfußbefestigung is to change.</li></ul>

LIST OF REFERENCE NUMBERS

p0038<dl id="dl0002" compact="compact"><dt>1</dt><dd>shroud</dd><dt>2</dt><dd>airfoil</dd><dt>3</dt><dd>Platform / inner platform</dd><dt>4</dt><dd>shaft</dd><dt>5</dt><dd>foot</dd><dt>6</dt><dd>internal load carrier</dd><dt>7</dt><dd>cavity</dd><dt>8th</dt><dd>leaf member</dd><dt>9</dt><dd>groove</dd><dt>10</dt><dd>Outdoor platform</dd><dt>11</dt><dd>groove</dd><dt>12</dt><dd>groove</dd><dt>13</dt><dd>base</dd><dt>14</dt><dd>recess</dd><dt>15</dt><dd>base</dd><dt>16</dt><dd>recess</dd><dt>17</dt><dd>base</dd><dt>18</dt><dd>Cooling chambers for film cooling of the blade member 8</dd><dt>19</dt><dd>Cooling channels in the foot 5</dd><dt>20</dt><dd>damping element</dd><dt>21</dt><dd>gas load</dd><dt>22</dt><dd>moment arm</dd><dt>23</dt><dd>machine axis</dd><dt>24</dt><dd>centrifugal</dd><dt>25</dt><dd>Centrifugal-moment arm</dd><dt>26</dt><dd>Centrifugal force couple</dd><dt>27</dt><dd>Gas power-force couple</dd><dt>28</dt><dd>compensation part</dd></dl>