Transcript Modern Design Concepts - Delta State University

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
requirements.
– This was called the inverse design.
NASA
• 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
characteristics
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)0416.
– 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
Designs
• 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
Designs
• 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
Designs
• Development in Propulsion systems
• Turboprops
– prime performance for business & commuter
planes
– 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.