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Convection and Impingement Cooling/Strut Insert Design

 Convection and Impingement Cooling/Strut Insert Design

  • The strut insert design has a mid chord section that is convection-cooled through horizontal fins, and a leading-edge that is impingement cooled. The coolant is discharged through a split trailing edge. The air flows up
  • the central cavity formed by the strut insert and through holes at the leading edge
  • of the insert to impingement cool the blade leading edge. The air then circulates
  • through horizontal fins between the shell and strut, and discharges through slots
  • in the trailing edge. The temperature distribution for this design .
  • The stresses in the strut insert are higher than those in the shell, and the
  • stresses on the pressure side of the shell are higher than those on the suction
  • side. Considerably more creep strain takes place toward the trailing edge than
  • the leading edge. The creep strain distribution at the hub section is unbalanced.
  • This unbalance can be improved by a more uniform wall temperature distribution.
  • Film and Convection Cooling Design
  • This type of blade design. The midchord region is
  • convection-cooled, and the leading edges are both convection and film-cooled.
  • The cooling air is injected through the blade base into two central and one leading
  • edge cavity. The air then circulates up and down a series of vertical passages.
  • At the leading edge, the air passes through a series of small holes in the wall of the
  • adjacent vertical passages, and then impinges on the inside surface of the leading
  • edge and passes through film cooling holes. The trailing edge is convectioncooled
  • by air discharging through slots. The temperature distribution for film and
  • convection cooling design. From the cooling distribution
  • diagram, the hottest section can be seen to be the trailing edge. The web, which
  • is the most highly stressed blade part, is also the coolest part of the blade.
  • A similar cooling scheme with some modifications is used in some of the latest
  • gas turbine designs. The firing temperature of GE FA units is about 2350 F
  • (1288 C), which is the highest in the power generation industry. To accommodate
  • this increased firing temperature, the FA employs advanced cooling
  • techniques developed by GE Aircraft Engines. The first and second stage blades
  • as well as all three nozzle stages are air-cooled. The first stage blade is convectively
  • cooled by means of an advanced aircraft-derived serpentine arrangement.

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