► SETTINGS | Database | Profiles
The dialog lists all defined profiles. New ones can be added, present profiles can be renamed, deleted and changed.
In the right panels, the properties of the selected profile can be defined. The available parameter vary depending on the profile type.
The buttons for opening and saving offer the possibility of the exchange of profile data between CFturbo installations.
The NACA 4 Digit wing sections are low cambered profiles. This family of profiles allows a separate modification of camber and thickness, which is especially advantageous for blade design.
The profile are defined by:
•First digit describing maximum camber as percentage of the chord.
•Second digit describing the distance of maximum camber from the airfoil leading edge in tens of percents of the chord.
•Last two digits describing maximum thickness of the airfoil as percent of the chord
The thickness distribution is given by:
In case the profile is not cambered, its center of gravity is located at x/l = 42.04 %. This is the default position for the axial positioning in blade position and sweep.
The meanline consists of two parabola arcs, whose transition point is their apex, respectively. The point is defined by the the first two digits.
In addition to the geometric properties lift coefficients and glide numbers need to be set with respect to the angle of attack.
The NACA 65 series is of importance for turbo-machinery because of their systematic cascade studies. In contrast to NACA 4 digit, their aerodynamic data is also known for more heavy cambered profiles.
The meanline can be calculated from a theoretical lift coefficient that is calculated from a user-defined camber angle, see Carolus p. 54, (Eq. 3.11, 3.12):
The nose radius can be modified, thickness values have to be changed in the table. One can type in a camber angle that will result in a cambered profile. This profile can be promoted to Point-based profiles by pressing convert. Please note that the skeleton design is done in the appropriate design step. Therefore the camber angle is not part of the profile description and is given here for informational and conversion reasons.
Besides NACA profiles also user-defined profiles are provided. Therefore the lower and upper side of the profile has to be known. Moreover lift coefficients and glide numbers need to be set with respect to the angle of attack.
Circular profiles are constructed by 2 circular arcs, 1 linear piece and a nose with a certain nose radius. They are described by 3 parameters: profile angle β, nose radius rN/l and a radius offset. The construction details are displayed in the sketch below: