OTHER:Aerodynamics - General - Blade Loading Coefficient (Mean Lift Coefficient) [CT/σ]
Note re Twin Rotor Configurations:
There is no consensus amongst the gurus as to what the disk area is for twin rotor helicopters. Therefor it is impossible to have a consensus as to the solidity ratio, for twin rotor configurations. Note that the algorithm above does not use disk area, because it is self-canceling.
Note re Advancing Blade Concept:
The report 'Advancing Blade Concept (ABCTM) Development' says "While blade loadings up to CT/σ ≈ 0.185 have been demonstrated, the full lift capacity of the rotor system is yet to be demonstrated."
The report 'The Impact Missions on the Preliminary Design of an ABC Rotor' makes much reference to L/De plotted against CT/σ. The figures 8 and 9 compare Blade Load Coefficients between Thrust Weighted Solidity and Geometric Solidity. The difference is significant. I wonder how valid this is, when considering that there is dissymmetry of lift in forward flight and there should never be retreating blade stall?
Note re Stepniewski'sImplications of the Low Tip Speed Design Philosophy ~ by Stepniewski, Wieslaw Z:
The above algorithm clearly shows that to maintain the same Blade Loading Coefficient and Thrust, any reduction in RRPM must be accompanied by an increase in the blade area.This is relevant to hover but I suspect that forward velocity and ABC will also benefit from the large blade area.
Related Page; at This Site:
DESIGN: UniCopter ~ Rotor - Disk - Large Chord & Low Tip Speed
Information on this page that is specifically on the subject of Blade Loading Coefficient is locatedhere.
Aerodynamic Blade Loading:[CT/σ] [Ct/sigma]
is a simple concept that lets us see how far from stall the rotor is operating, similar to the coefficient of lift for an airplane's wing. It is thecoefficient of thrust divided by the solidity.
The Sikorsky ABC has demonstrated blade loadings up to 0.185, but the full lift capacity of the rotor system has yet to be demonstrated ~ (1976)
From Prouty "Helicopter Aerodynamics - p.68" "Most rotors are at the peak of their efficiency in forward flight when CT/σ is about .08.
Reference the following rough and temporary info.
The UniCopter's Solidity is0.1583 and the Blade Loading Coefficient is 0.0611.
The SynchroLite's Solidity is0.0448and the Blade Loading Coefficient is 0.0434.
These intermeshing values are based on theTotal Disk Area. There may be a problem here re Sigma and how to define it for the intermeshing configuration.
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Last Revised: May 11, 2009