Turbine Platform Film Cooling Effectiveness and Rotational Effect on Internal Cooling Passages with a Converging Tip Turn

Through the advancement of gas turbine cooling technologies, gas turbine engines remain one of the most reliable technologies in the aviation and power generation industries. The combined cycle efficiency of a power generation gas turbine is expected to reach 65% by the year of 2020. The internal and external cooling designs of gas turbine components play an essential role in achieving this goal. In the first part, experimental investigations were conducted on a five-blade linear rotor cascade platform with upstream purge flow, slashface leakage flow, and discrete film cooling using both cylindrical and fan-shaped holes. Detailed film cooling effectiveness distributions were obtained using the pressure sensitive paint (PSP) technique. Parametric studies on the coolant to mainstream mass flow ratio (0.5% - 1%), blowing ratio (0.5 - 1.5), density ratio (1 – 2), or the purge flow swirl ratio (0.6 and 1) were performed. The area-averaged film cooling effectiveness values of the two film hole geometries are compared and discussed. In general, the design with the fan-shaped cooling holes provides better film effectiveness and coverage at higher blowing, density, and momentum flux ratios. In the second part, heat transfer and pressure measurements were performed in a two-pass rectangular channel with varying aspect ratios: AR = 4:1 in the first pass and AR = 2:1 in the second pass after a 180 deg converging tip turn. In addition to the smooth-wall case, surfaces roughened with 60 deg angled ribs and 45 deg angled ribs with three different rib coverages were investigated. Regionally averaged heat transfer measurement method was used to obtain the heat transfer coefficients on all surfaces within the flow passages. The Reynolds number ranges from 10,000 to 70,000 in the first passage, and the rotational speed ranges from 0 to 400 rpm. Under a pressurized condition, the highest rotation number achieved was Ro = 0.39 in the first passage and 0.16 in the second passage. The results showed that both heat transfer and pressure coefficients are sensitive to the geometrical and rib design of the channel. More importantly, significant heat transfer reduction was identified on the tip wall under rotation