Characteristics of a Cambered Circulation Control Airfoil Having Both Upper and Lower Surface Trailing Edge Slots

摘要

A circulation control (CC) elliptic airfoil section with a thickness- to-chord ratio of 0.17 and 1- percent circular arc camber, was experimentally evaluated to determine its low speed aerodynamic characteristics. The model profile is that of a previously tested single upper surface trailing edge slot airfoil, modified to incorporate an additional blowing slot on the lower surface. The main objective of this initial test was to determine if the control range, that is the range of lift coefficient available at a given angle-of- attack and momentum coefficient, could be increased without compromising the performance previously obtained with the single slot version. Test results show that the control range is more than doubled and there is no impact on upper surface only blowing performance. The range of lift coefficient produced at alpha equals zero degrees, using a combination of upper and lower slot only blowing is C1 from +3.6 to -4.0. Blowing efficiency when using the lower slot was found to be higher than that obtained when using the upper slot. This finding was somewhat unexpected, since lower surface blowing is equivalent to using CC on a negatively cambered airfoil. Data was acquired using either only the upper or lower surface slot or with dual blowing, that is simultaneous upper and lower slot blowing.