Film cooling characteristics on the leading edge of a rotating turbine blade with various mainstream Reynolds numbers and coolant densities

This paper reports on an experimental investigation of the influences of mainstream Reynolds number and coolant density on film cooling characteristics on the leading edge of a twisted turbine blade under rotational conditions. The experiments were carried out at a test facility with a 1-stage turbine using the thermochromic liquid crystal (TLC) technique. The mainstream Reynolds number varied from 4.4201 × 10⁴ to 7.1797 × 10⁴. All tests were carried out at three rotational speeds of 400 r/min, 500 r/min and 650 r/min to fix the rotation number at 0.0018. The coolant-to-mainstream density ratios were fixed at 1.04 and 1.56 with N₂ and CO₂ as coolants, respectively. The blowing ratio effect was also considered. The results showed that under the same blowing ratio, the averaged film cooling effectiveness on the measurement area increased with increasing mainstream Reynolds number for both coolant gases. Under the same Reynolds number, the span-wise averaged film cooling effectiveness increased as the blowing ratio increased for both coolant gases. Under the same Reynolds number and blowing ratio, higher-density coolant jets (CO₂) provided higher averaged film cooling effectiveness than lower-density coolant jets (N₂) on the measurement area. Overall, mainstream Reynolds number, blowing ratio and coolant density played significant roles in the film cooling characteristics of the leading edge under rotational conditions.