Document Sample
AEROlec10LASTONE Powered By Docstoc
					Modern Design Concepts

         Chapter 10
         Second Half
 Last Lecture of the Semester
       Modern Airfoil Design
• NASA looked at developing an airfoil for
  general aviation that combine the high lift
  of the early 4-digit airfoils and the low drag
  of the 6- digit airfoils.
  – The key was the achievement of true laminar
    flow over a significant portion of the airfoil
    strictly by the shape.
     • No external blowing or artificial means of
       preserving the laminar boundary layer
  Natural Laminar Flow Airfoils
• These new airfoils were called natural laminar
  flow airfoils
• The old NACA airfoils could only be altered one
  parameter at a time
• The new approach that NASA used was to first
  specify the desired characteristics that a particular
  airfoil required; then design it to meet those
   – This was called the inverse design.
• NASA worked with the Eppler method
  which began with a prescribed pressure
  disturbance over the airfoil, and applied
  various aerodynamic theories to analyze the
  flow and establish the boundary layer
            Eppler Method
• The Eppler method had provisions to
  account for altitude at gross weight.

• This method allowed NASA to account for
  a variety of considerations
  First Airfoil Intended for Light
     Single Engine Airplanes
• The first airfoil intended for light single
  engine airplanes was the NASA NFL (1)-
  – The fist two numbers(04) signify a design lift
    coefficient of 0.4 and the 16 refers to a
    maximum thickness of 16% of the chord.
  – The 1 in parenthesis refers to the first
    generation of such airfoils
       Newer Design Details
• Swept vertical Fins & T-tail arrangements
• Winglets, improved cowl shapes, carefully
  designed fillets

• *** All these aerodynamic refinements are
  quite beneficial
     Potential Airliner Designs
• Engine Efficiency/Aerodynamic efficiency
  – higher aspect ratios
• Very Narrow Chord Wings
  – reducing skin friction drag, increasing
    favorable pressure gradient; increasing laminar
    flow at higher speeds
• Span Loading
  – distributing the payload over all of the span
    Potential General Aviation
• Composite structures
  – can be molded & bound for very smooth
    aerodynamic surfaces
  – boron or carbon fibers give high strength with
    little weight
  – composites smoother & stronger
    Potential General Aviation
• Development in Propulsion systems
• Rotary/Wankel engine
  – an internal combustion engine without pistons
  – the combustion process drives the rotor in
    continuous, smooth, rotating manner
  – can run on a variety of fuels
  – it does not produce a tremendous amount of
    power for its weight
    Potential General Aviation
• Development in Propulsion systems
• Turboprops
  – prime performance for business & commuter
  – single and multi engine
  – pictures on pages 295-298
    Quiz on Chapter 10

     Take out a sheet of paper
Include today’s date and your name
         Quiz on Chapter 10
• How has the study of aerodynamics affected
  modern aircraft design? Support your
  answer with an example.

Shared By: