0995

Item 0995

DESIGN: SynchroLite ~ Rotor - Disk - Downwash - Intermeshing Disks in Forward Flight

Drawing:

Direction of rotation is conventional breaststroke.

Notes:

It can be seen that the intermeshing configuration has a larger disk area than that of a comparable coaxial or single rotor ⁽¹⁾. This larger disk area results in a lower disk loading and therefore a greater efficiency.

In addition, it can be seen that the outer portions of the retreating blades have the greatest thrust. This greater thrust is located outside the disk of the other rotor. The result is an improved distribution of the thrust and a further improvement in the efficiency.

".... the upper and lower rotor wakes contracted radially inward at a faster and slower rate, respectively."⁽²⁾ This will also apply to the intermeshing configuration, and thereby add a further improvement to the thrust distribution and efficiency.

"Increasing advance ratio causes the upper rotor wake to be "swept back." This results in more of the lower rotor being exposed to clean air, which leads to better performance." ⁽²⁾This will also apply to the intermeshing configuration, but with not as much effect as with the coaxial.

The above characteristics will result in the intermeshing configuration having a greater thrust to power ratio than the single rotor or the coaxial. Only the side-by-side configuration will have a greater efficiency.

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Footnotes:

This is a comparison of main rotors only. It does not include the single rotor configuration's additional reduction in efficiency, due to its tail rotor. The comparison also assumes that the number of blades on the single rotor configuration equals the total number of blades on the twin rotor configurations.
'A Survey of Theoretical and Experimental Coaxial Rotor Aerodynamic' ~ NASA Technical Paper 3675, March 1997

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Last Revised: October 15, 2011