Small-Scale Airfoil Aerodynamic Efficiency Improvement by Surface Temperature and Heat Transfer

The improvement of aerodynamic efficiency of small-scale airfoils using surface temperature and heat transfer is investigated using numerical simulations, asymptotic analysis, and experimental work. The basic idea is to take a direct advantage of heat transfer that dominates microscale systems to enhance lift, reduce drag, and increase the envelope of operation of airfoils. This is achieved by cooling the upper surface and heating the lower surface of the airfoil. The numerical simulations show that, although varying surface temperature does not produce significant impact at the full-scale (Reynolds numbers > 10 6 ), because the thickness of the thermal boundary layer is very small compared to the airfoil chord, its effect is very pronounced at the microscale, where the thermal and velocity boundary layers are larger. The asymptotic theory demonstrates that most of the effect actually comes from the heat transfer in the much smaller nose region of the small-scale airfoil. The experimental apparatus consists of a microrotor system that uses the Peltier effect to produce different temperatures on the surfaces of the blades