Item 1612

DESIGN: AeroVantage ~ PropRotor - Disk - Aerodynamically Variable Disk Area

 

 

 

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Tandem

for

Lift

 

 

Related page:  OTHER: Aerodynamics ~ General - Optimum PropRotor

Coaxial

for

Speed

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Overview:

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·        The effective aerodynamic disk area is 50% smaller during cruise then it is during hover. This is achieved by combining the two rotors into one coaxial counter-rotating propulsor.

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Perceived Advantages:

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Wake Contraction:

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Streamtube ~ Some Initial Thoughts:

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Concern:

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Outside Information on the subject:

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Convergence of the Two Streamtubes:

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A one-fifth-scale wind tunnel model has undergone testing in the Transonic Dynamics Tunnel (a unique transonic wind tunnel) at NASA's Langley Research Center during summer 2006. The "semi-span" model (representing the right half of the aircraft) measured 213 inches in length, and had powered 91-inch rotors, operational nacelles, "dynamically representative" wings.[5]

The primary test objective was to study the aeroelastic effects on the aft wing of the forward wing's rotors and establish a baseline aircraft configuration.[1] Alan Ewing, Bell's QTR program manager, reported that "Testing showed those loads from that vortex on the rear rotor [are the] same as the loads we see on the front [rotors]," and "Aeroelastic stability of the wing looks exactly the same as the conventional tiltrotor". These tests used a model with a three-bladed rotor, future tests will explore the effects of using a four-bladed system.[4]

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Contra-rotating Coaxial Propellers:

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Optimal PropRotor Diameter - Fore and Aft

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Related Information:

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Playing Around:

 

 

Hover:

Cruise:

Non-dimensional Ratio:

 

Disk Area:

A + a = Aa

0.91A

 

 

Blade Area:

B + b = Bb

Bb

 

 

Solidity Ratio:

Bb / Aa

Bb / 0.91A

 

 

Induced Velocity:

 

 

 

 

 

 

 

 

 

 

 

 

 

o   Based on balanced torque; not balanced thrust

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Comment:

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Rough Notes:

    1. Coaxial counterrotating PropRotors rotating at a reduced speed (and lower motor and propeller efficiency)
    2. Either Propeller: Stop and feathering the front or the rear PropRotor(s) and use one only for propulsion
    3. Front propeller: Stop the rear PropRotor(s) and have its blade fold back against or into, the nacelle and use only the front proprotor for propulsion.

o   The Quad V-44 rotor may be able to do 2 and 3.

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Comparison of Rotor diameter to Propeller diameter for comparable rotary-wing and fixed-wing craft;

This is done to see what the change in diameters should be to be optimized for both types.

Types:

Rotary-wing:

Fixed-wing:

Ratio:

Manufacturer:

Robinson

Diamond

 

Model:

R22 Beta II

DA 20

 

Gross weight:

1370 lb

1,764 lbs

 

Empty weight:

855 lb

 

 

Passengers & baggage w/ standard fuel:

400 lb

600 lbs

0.67:1

Horsepower:

Lycoming O-360  180 hp

TCM IO-240-B3B  125 hp

1.44:1

Disk/prop diameter:

25 ft 2 in. dia.

5 ft 6.9 in. dia.

 

Disk/prop area:

498 sq. ft.

24.4

20.4:1

Wing area:

 

125 sq. ft.

 

 

 

 

 

 

 

 

 

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Information related to Contra-rotating Propellers:

·        DESIGN: AeroVantage ~ PropRotor - Outside Information - Contra-Rotating Props and Related Material

Introduction Page | SynchroLite Home Page | Electrotor Home Page | UniCopter Home Page | Nemesis Home Page | AeroVantage Home Page

Initially displayed: January 30, 2008 ~ Last Revised: May 17, 2014

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