Investigation of Heat Transfer in Stationary and Rotating Internal Cooling Channels with High Rotation Numbers Mandana Sheikhzad Saravani Saman Beyhaghi Advisor: Prof. Ryoichi S. Amano Department of Mechanical Engineering

Overview Introduction Define the Problem Computational Setup (Cases) Experimental Apparatus Summary and Conclusion

Introduction Gas turbines are typically used for power generation in power plants or jet engines. To increase the efficiency of gas turbines, designers are continually trying to raise the maximum turbine inlet temperature. With an increase of the temperature, improvements in blade cooling technology is required. Alloys with improved material properties are used to withstand high temperatures.

Define the Problem Gas turbine rotor and stator blades can fail due to excessive temperatures and high thermal stresses. Several cooling techniques are proposed and implemented. Using Impinging jets and internal cooling passages are some of the most common techniques. In the latter, some of the cold inlet air flow is directed through Internal serpentine cannels to remove the excess heat.

Problem Description Our objective is to investigate the heat transfer characteristics in a high-speed rotating two-pass square channel, mimicking the cooling passages drilled inside a gas turbine blade. Air enters channel at ambient temperature with a uniform inlet velocity. Test section rotates around an off-set axis parallel to channel inlet plane, placed about 15 cm away from that plane. Both CFD and experimental analyses are considered.

Computational Setup (Cases) Inlet velocity of air was 12.5 m/s, giving the Reynolds number based on hydraulic diameter ReDh~ 43,000. Rotation number Ro is defined as Case# 1 2 3 4 5 Rotation speed (RPM) 300 600 1200 1530 Angular velocity  (rad/s) 31.4 62.8 125 160 Rotation number Ro 0.125 0.25 0.5 0.65

Temperature Distribution at the Horizontal Mid-Plane Stationary Uin =12.5 m/s Ro=0.51,ω=1200 rpm, Uin=12.5 m/s

Velocity Distribution at the Horizontal Mid-Plane Stationary Uin =12.5 m/s Ro=0.51,ω=1200 rpm, Uin=12.5 m/s

Velocity distribution on vertical planes Outlet Inlet Stationary, Uin=12.5m/s

Velocity distribution on vertical planes Outlet Inlet Ro=0.51,ω=600 rpm, Uin=6.25 m/s

Experimental Apparatus An experimental test apparatus is designed, fabricated and currently being assembled at the University of Wisconsin Milwaukee.

Summary and Conclusion A computational framework is established, and primary results are obtained for stationary cases with Reynolds numbers of up to 34000, and rotating cases with Rotation numbers of up to 0.75. Velocity and temperature contours on the horizontal mid-plane of the channel are presented. Increasing the Reynolds number while keeping Ro fixed, will increase the average Nusselt number. Once a good agreement between the computational and experimental sets of results are obtained, several modifications will be made to the design, and the influence of various parameters, such as the channel shape and aspect ratio will be studied.

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