Pneumatic controlol of aerodynamic high lift configurations has been studied for more than 65 years. Wind tunnel, computational, and flight experiments have shown significant benefits of pneumatically controlling the flow field using steady tangential blowing over the rounded Coanda trailing edge of a wing. In spite of the benefits, these techniques have not frequently been applied to production aircraft. Many of the roadblocks have been associated with the engine bleed requirements and cruise penalties associated with blunt blown trailing edges. The desire to use a larger radius Coanda surface for maximum lift is often a trade-off with a smaller radius Coanda surface for minimum cruise drag. This paper will focus on two airfoil configurations that address these issues through the use of pulsed or unsteady pneumatics. Two independent experimental investigations have been conducted to evaluate the ability of pulsed blowing to reduce the mass flow requirements for high lift generation of CCW-type blown configurations. The basic difference in these CCW (Circulation Control Wing) configurations is founded in the streamline turning mechanisms. The GACC required more jet entrainment to achieve the same streamline deflection as the Dual Radius CCW configuration. However the Dual Radius is limited in streamline turning by it' s fixed separation defined by the tip of the flap (135 degree), whereas the GACC airfoil has a greater potential for larger streamline turning as jet separation extends auto the lower Coanda surface well beyond 165 degree. These limits were not evaluated in these experiments. Pulsed pneumatic control for both the Dual-Radius and GACC airfoil configurations tested, reduced the mass How requirements for a desired CL by more than 50 %. Conversely, for the same available mass flow rates, pulsing allowed considerably higher lift to be generated. Due to limitations in the pulsed actuator systems, the benefit of pulsed blowing was limited to separation control. It is believed that similar mass flow reductions can be achieved in the super-circulation region where time dependent penetration would occur. These blown airfoil configurations also showed the ability to reduce cruise drag either by retraction of a small-chord curved CCW flap or by creating a 'virtual' sharp trailing edge by blowing both the upper and lower slots of a dual-slot configuration. Pulsed blowing configurations also verified that they could achieve the same equivalent lift-to-drag ratio as the steady-state case, but at 55-60 % reductions in required mass flow rates. CFD analyses presented indicated that additional gains could be expected from pulsed blowing at higher frequencies, but the experimental mechanisms of the current tests have not yet achieved that capability.


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    Titel :

    Advances in pneumatic-controlled high-lift systems through pulsed blowing


    Weitere Titelangaben:

    Fortschritte bei pneumatisch geregelten Hochauftriebssystemen durch pulsierendes Ausblasen


    Beteiligte:
    Jones, G.S. (Autor:in) / Englar, R.J. (Autor:in)


    Erscheinungsdatum :

    2003


    Format / Umfang :

    14 Seiten, 31 Bilder, 25 Quellen



    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Print


    Sprache :

    Englisch