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In an attempt to investigate the acoustic resonance effect of serpentine passages on internal convection heat transfer, the present work examines a typical high pressure turbine (HPT) blade internal cooling system, based on the geometry of the NASA E3 engine. In order to identify the associated dominant acoustic characteristics, a numerical finite-element method (FEM) simulation (two-step frequency domain analysis) is conducted to solve the Helmholtz equation with and without source terms. Mode shapes of the relevant identified eigenfrequencies (in the 0–20 kHz range) are studied with respect to induced standing sound wave patterns and the local node/antinode distributions. It is observed that despite the complexity of engine geometries, the predominant resonance behavior can be modeled by a same-ended straight duct. Therefore, capturing the physics observed in a generic geometry, the heat transfer ramifications are experimentally investigated in a scaled wind tunnel facility at a representative resonance condition. Focusing on the straight cooling channel's longitudinal eigenmode in the presence of an isolated rib element, the impact of standing sound waves on convective heat transfer and aerodynamic losses are demonstrated by liquid crystal thermometry, local static pressure and sound level measurements. The findings indicate a pronounced heat transfer influence in the rib wake separation region, without a higher pressure drop penalty. This highlights the potential of modulating the aerothermal performance of the system via acoustic resonance mode excitations.

In light of the potential of acoustic excitation for heat transfer enhancement, the research effort herein is geared towards a better understanding of the underlying physical mechanisms of aero-thermal laminar and turbulent boundary layer development under the influence of directed sound excitation. An experimental measurement campaign is carried out throughout which the effects of small amplitude periodic flow oscillations on convective heat transfer in straight channels are investigated. A low velocity wind tunnel facility has been designed and built for this purpose. Measurements of convective heat transfer are conducted by means of steady wide band liquid crystal thermometry at several acoustic and aerodynamic parameters. The findings of this investigation indicate that modification of convective heat transfer by directed sound excitations is possible. Dependent on the source frequency, the net effect can be a heat transfer augmentation or a local reduction. Although the acoustically induced changes are small in magnitude, the dependence on the excitation frequency is still quantifiable beyond measurement error.

In an attempt to investigate the acoustic resonance effect of serpentine passages on internal convection heat transfer, the present work examines a typical high pressure turbine blade internal cooling system, based on the geometry of the NASA E3 engine. In order to identify the associated dominant acoustic characteristics, a numerical FEM simulation (two-step frequency domain analysis) is conducted to solve the Helmholtz equation with and without source terms. Mode shapes of the relevant identified eigenfrequencies (in the 0–20kHz range) are studied with respect to induced standing sound wave patterns and the local node/antinode distributions. It is observed that despite the complexity of engine geometries, as a first order approximation, the predominant resonance behavior can be modeled by a same-ended straight duct. Therefore, capturing the physics observed in a generic geometry, the heat transfer ramifications are experimentally investigated in a scaled wind tunnel facility at a representative resonance condition. Focusing on the straight cooling channel’s longitudinal eigenmode in the presence of an isolated rib element, the impact of standing sound waves on convective heat transfer and aerodynamic losses are demonstrated by liquid crystal thermometry, local static pressure and sound level measurements. The findings indicate a pronounced heat transfer influence in the rib wake separation region, without a higher pressure drop penalty. This highlights the potential of modulating the aero-thermal performance of the system via acoustic resonance mode excitations.