Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
  • F01D5/12—Blades
  • F01D5/14—Form or construction
  • F01D5/18—Hollow blades, i.e. blades with cooling or heating channels or cavities; Heating, heat-insulating or cooling means on blades
  • F01D5/187—Convection cooling
  • F01D5/188—Convection cooling with an insert in the blade cavity to guide the cooling fluid, e.g. forming a separation wall
  • F01D5/189—Convection cooling with an insert in the blade cavity to guide the cooling fluid, e.g. forming a separation wall the insert having a tubular cross-section, e.g. airfoil shape

Definitions

• the present invention relates to a gas turbine blade.
• the present invention relates to a gas turbine stator blade.
• a known type of stator blade comprises a main hollow body substantially extending along a longitudinal axis and having a leading edge, a trailing edge, opposite to the leading edge, and a suction side and a pressure side, both comprised between the leading edge and the trailing edge.
• a hollow cooling element which extends along the longitudinal axis, is equipped with a plurality of cooling holes and is set within the main body so as to define a gap between the main body and the cooling element.
• the stator blade moreover comprises at least one rib, which is set within the gap on the leading edge for connecting the main body with the cooling element.
• Stator blades of this type exploit the technique of cooling referred to as "impingement cooling”.
• the cooling fluid generally air, supplied within the cooling element, exits from the holes of the cooling element in a direction substantially orthogonal to the wall of the cooling element, comes to impinge upon the internal surface of the blade and laps it, guaranteeing proper cooling thereof.
• the fluid is then expelled from the gap by means of one or more holes for communication between the gap and the outside of the blade on the suction side and/or the pressure side and/or the trailing edge of the blade. In this way, the temperature of the metal of the blade is maintained substantially below the critical values.
• the presence of a rib in the gap optimizes cooling in the areas surrounding it in so far as it generates at the sides of the rib itself two areas of stagnation of the cooling fluid.
• the flow of the cooling fluid does not have components tangential to the wall of the cooling element due to the return of "hot" fluid from other areas of the gap, but only components orthogonal to the wall of the cooling element basically due to exit of the cooling fluid from the holes.
• stator blades of this type suffer from a main drawback due to the fact that the holes for passage of the cooling fluid have a very small section and consequently are frequently subject to phenomena of partial or total occlusion on account of the presence of impurities in suspension in the cooling fluid that tend to aggregate. Furthermore, difficult environmental conditions can aggravate the phenomena of soiling referred to above, for example in desert environments or in the proximity of industrial settlements, in particular siderurgical centres, or in the case of use of cooling systems external to the gas turbine of the "cooler and booster" type.
• the area most concerned by this phenomenon of "soiling" is the leading edge, which is impinged upon directly by the hot gases coming from the combustion chamber. Said area, in fact, requires a particularly large quantity of cooling fluid, being most subject to thermal stresses.
• the presence of the rib on the leading edge in conditions of soiling of the holes does not lead to an optimization of the cooling action but rather a worsening, if not a practically total absence, of cooling.
• the flow of cooling fluid does not present components tangential to the wall of the cooling element but only orthogonal components determined basically by the fluid leaving the holes. Consequently, if the fluid leaving the holes decreases drastically on account of "soiling" cooling in said area is practically absent.
• An aim of the present invention is to provide a blade that is free from the drawbacks of the known art highlighted herein.
• an aim of the invention is to provide a blade that is capable of guaranteeing a correct cooling also in conditions of soiling of the holes of the cooling element and is at the same time easy and inexpensive to produce.
• the present invention relates to a gas turbine blade comprising a main hollow body substantially extending along a longitudinal axis A and having a leading edge, a trailing edge, opposite to the leading edge, a suction side, and a pressure side, both comprised between the leading edge and the trailing edge.
• a hollow cooling element extends along the axis A, which is equipped with a plurality of cooling holes and is set within the main body so as to define a gap between the main body and the cooling element, and a rib, which is set within the gap for connecting the main body with the cooling element, the blade being characterized in that the rib is set on the suction side in an area of the main body without holes for communication between the gap and the outside of the blade.
• FIG. 1 is a cross-sectional view, with parts removed for reasons of clarity, of a gas turbine blade according to the present invention
• FIG. 2 is a cross-sectional view at an enlarged scale, with parts removed for reasons of clarity, of a detail of the blade of Figure 1;
• FIG. 3 is a cross-sectional view at an enlarged scale, with parts removed for reasons of clarity, of a further detail of the blade of Figure 1; and - Figure 4 is a partial perspective view, with parts removed for reasons of clarity, of the blade of Figure 1.
• the blade 1 comprises a main hollow body 2, a cooling element 3, a rib 4, and a plurality of spacers 5.
• the main body 2 extends along a longitudinal axis A and has a leading edge 6, a trailing edge 7 opposite to the leading edge 6, a suction side 8 (also referred to as “suction face” or “back”) and a pressure side 9 (also referred to as “pressure face”) , both comprised between the leading edge 6 and the trailing edge 7.
• the main body 2 defines a cavity 13, within which the cooling element 3 is set so as to define a gap 14, comprised between the main body 2 and the cooling element 3.
• the cooling element 3 extends along the longitudinal axis A for the entire extension of the main body 2 and comprises a metal insert 16 shaped and closed in a loop, which is equipped with a plurality of holes 17 suitable for being traversed by a cooling fluid and defines a duct 18 suitable for being supplied with the cooling fluid.
• the holes 17 are set according to a pre-set scheme on the metal insert 16 of the cooling element 3.
• the holes 17 are set so as to form columns parallel to the axis A of the blade 1 and staggered with respect to one another in a direction perpendicular to the axis A.
• the cooling element 3 preferably has a shape similar to the shape of the blade 1 so that the gap 14 will have a substantially constant width.
• the rib 4 is set in the gap 14 in the gap 14 for connecting the main body 2 with the cooling element 3.
• the rib 4 is set on the suction side 8 in an area of the main body 2 without holes for communication between the gap 14 and the outside of the blade 1 and extends substantially parallel to the longitudinal axis A throughout the length of the blade 1.
• the rib 4 is positioned at a distance from the leading edge 6, measured externally to the blade 1 along the suction side 8, comprised between approximately 20% and approximately 40%, and preferably between approximately 25% and approximately 35%, in particular substantially equal to approximately 30%, of the overall distance, again measured externally to the blade 1 along the suction side 8, between the leading edge 6 and the trailing edge 7.
• the rib 4 is defined by an external projection of the cooling element 3, but it remains understood that it is also possible to provide a blade 1 in which the rib 4 is defined by an internal projection of the main body 2.
• the metal insert 16 of the cooling element 3 has two terminal flaps 22, bent and coupled to one another to define the rib 4.
• the rib 4 is connected throughout its length to the main body 2 and to the cooling element 3 so as to define two chambers 20 and 21 of the gap 14.
• the first chamber 20 of the gap 14 comprises the area of the gap 14 that extends along the suction side 8 starting from the rib 4 up to the trailing edge 7, whilst the second chamber 21 of the gap 14 comprises the area of the gap 14 that extends starting from the rib 4 along the leading edge 6 and the pressure side 9 up to the trailing edge 7.
• the blade 1 moreover comprises further spacers 23 set in the cavity 13 of the main body 2 substantially in a position corresponding to the trailing edge 7 to maintain the distance between opposite walls of the main body 2 fixed during operation of the turbine.
• the cooling fluid (schematically represented by the arrows in Figure 1) is supplied to the cooling element 3 and sent, through the holes 17, into the gap 14 for cooling the blade 1.
• the rib 4 generates, in the gap 14 at the sides of the rib 4 itself, two areas of stagnation of the cooling fluid, in which the flow of the cooling fluid is substantially without components F ⁇ tangential to the metal insert 16 of the cooling element 3, principally due to the return of fluid from other areas of the blade 1, but only components F 0 orthogonal to the metal insert
• the presence of the rib 4 substantially on the suction side 8 of the blade 1 imposes upon the flow of the cooling fluid an obligate path such as to determine, in the gap 14 in a position corresponding to the leading edge 6, a tangential component F ⁇ of the flow of cooling fluid.
• the tangential component F ⁇ of the flow of cooling fluid laps the main body 2 internally, guaranteeing a minimum cooling action, which, by possibly being associated to the adoption of an appropriate external coating of the blade (the so-called "thermal barrier", which is per se known) , is sufficient to maintain the blade 1 intact.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Turbine Rotor Nozzle Sealing (AREA)

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• 2007
  • 2007-01-04 EP EP07713410A patent/EP2115272A1/de not_active Withdrawn
  • 2007-01-04 WO PCT/IT2007/000004 patent/WO2008081486A1/en active Application Filing
  • 2007-01-04 US US12/522,051 patent/US20100143154A1/en not_active Abandoned
  • 2007-01-04 JP JP2009544497A patent/JP2010515850A/ja active Pending

Non-Patent Citations (1)

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