Ahn, Jaeyong (2005-12). Film cooling effectiveness measurements on rotating and non-rotating turbine components. Doctoral Dissertation. Thesis uri icon


  • Detailed film cooling effectiveness distributions were measured on the stationary
    blade tip and on the leading edge region of a rotating blade using a Pressure Sensitive
    Paint technique. Air and nitrogen gas were used as the film cooling gases and the
    oxygen concentration distribution for each case was measured. The film cooling
    effectiveness information was obtained from the difference of the oxygen concentration
    between air and nitrogen gas cases by applying the mass transfer analogy. In the case of
    the stationary blade tip, plane tip and squealer tip blades were used while the film
    cooling holes were located (a) along the camber line on the tip or (b) along the span of
    the pressure side. The average blowing ratio of the cooling gas was controlled to be 0.5,
    1.0, and 2.0. Tests were conducted in a five-bladed linear cascade with a blow down
    facility. The free stream Reynolds number, based on the axial chord length and the exit
    velocity, was 1,100,000 and the inlet and the exit Mach number were 0.25 and 0.59,
    respectively. Turbulence intensity level at the cascade inlet was 9.7%. All
    measurements were made at three different tip gap clearances of 1%, 1.5%, and 2.5% of
    blade span. Results show that the locations of the film cooling holes and the presence
    of squealer have significant effects on surface static pressure and film-cooling effectiveness. Same technique was applied to the rotating turbine blade leading edge
    region. Tests were conducted on the first stage rotor of a 3-stage axial turbine. The
    Reynolds number based on the axial chord length and the exit velocity was 200,000 and
    the total to exit pressure ratio was 1.12 for the first rotor. The effects of the rotational
    speed and the blowing ratio were studied. The rotational speed was controlled to be
    2400, 2550, and 3000 rpm and the blowing ratio was 0.5, 1.0, and 2.0. Two different
    film cooling hole geometries were used; 2-row and 3-row film cooling holes. Results
    show that the rotational speed changes the directions of the coolant flows. Blowing
    ratio also changes the distributions of the coolant flows. The results of this study will
    be helpful in understanding the physical phenomena regarding the film injection and
    designing more efficient turbine blades.

publication date

  • December 2005