Research Areas

- Vane internal cooling

Gas turbine vanes are exposed to extremely high-temperature combustion gases, often exceeding the allowable metal temperature. To maintain structural integrity and extend component life, compressor bleed air is supplied through internal cooling passages. Various cooling techniques, including impingement jets, ribs, pin fins, and film-cooling holes, are used to enhance internal convection and reduce wall temperature (Fig. 1). In particular, pin fins are commonly applied near the trailing edge, where the passage becomes narrow, because they provide both heat-transfer enhancement and structural support between the pressure-side and suction-side walls.

Figure 1. Schematic of internal cooling techniques in a gas turbine vane [1].

- Pin-fin cooling

Pin-fin cooling is commonly used in the trailing-edge region of gas turbine vanes to enhance internal heat transfer and provide structural support. The pin array promotes flow acceleration, turbulence, and wake interaction, while its arrangement strongly affects both cooling performance and pressure loss (Fig. 2). Our study focuses on these thermal–hydraulic characteristics under representative trailing-edge flow conditions.

Figure 2. Flow structure near the single pin fin [2].

- Magnetic resonance velocimetry (MRV)

Magnetic resonance velocimetry (MRV) is a non-intrusive technique that measures three-dimensional, three-component mean velocity fields without requiring optical access. In the scaled triangular trailing-edge channel, a 0.06 M copper-sulfate aqueous solution was circulated through the test section and scanned in a 3 T MRI system. The measurement captures volumetric flow through the impingement region, pin-fin array, and trailing-edge cutback slot, providing a direct view of the internal flow structures that govern cooling performance (Fig. 3).

Figure 3. Test setup for MRV measurements.

- Flow structure of pin-fin arrays

The MRV data show that post-impingement flow turns downstream along the pressure- and suction-side surfaces and forms low-speed wakes and counter-rotating vortices around the pin bases. As the channel contracts toward the trailing edge, the streamwise velocity increases, the wakes become narrower, and the wall-normal velocity profile becomes more uniform. The downstream acceleration suppresses secondary horseshoe-vortex structures while maintaining strong through-flow between the pins (Fig. 4).

Figure 4. Normalized velocity distribution and in-plane flow vectors in the pin-fin region measured by MRV.

- Experiment facility

Cooling air is supplied to the test section by a blower, and the inlet and outlet flow rates are monitored using flowmeters. An infrared camera records the spatial wall-temperature distribution through an optical window. Based on the measured wall temperature, applied heat flux, and bulk coolant temperature, local heat-transfer coefficients and Nusselt numbers are evaluated. The downstream valve is used to control the exit-flow split and reproduce the flow conditions applied in the MRV experiments.

Figure 5. Schematic of the heat-transfer experimental facility.

- Heat-transfer characteristics of pin-fin arrays

The local heat-transfer distribution was measured on the suction-side wall of a triangular pin-fin cooling channel. The Nusselt number generally increases toward the downstream region as the flow accelerates through the converging passage. Although secondary flow structures around the pins weaken downstream, the acceleration caused by the decreasing channel area maintains the heat-transfer enhancement.

Figure 6. Local Nusselt-number distribution on the suction-side wall of a triangular pin-fin cooling channel.