A Comparison of Coaxial and Conventional Rotor Performance
- 1 January 2010
- journal article
- Published by AHS International dba Vertical Flight Society in Journal of the American Helicopter Society
- Vol. 55 (1), 12004-1200420
- https://doi.org/10.4050/jahs.55.012004
Abstract
The performance of a coaxial rotor in hover, in steady forward flight, and in level, coordinated turns is contrasted with that of an equivalent, conventional rotor with the same overall solidity, number of blades, and blade aerodynamic properties. Brown's vorticity transport model is used to calculate the profile, induced, and parasite contributions to the overall power consumed by the two systems, and the highly resolved representation of the rotor wake that is produced by the model is used to relate the observed differences in the performance of the two systems to the structures of their respective wakes. In all flight conditions, all else being equal, the coaxial system requires less induced power than the conventional system. In hover, the conventional rotor consumes increasingly more induced power than the coaxial rotor as thrust is increased. In forward flight, the relative advantage of the coaxial configuration is particularly evident at pretransitional advance ratios. In turning flight, the benefits of the coaxial rotor are seen at all load factors. The beneficial properties of the coaxial rotor in forward flight and maneuver, as far as induced power is concerned, are a subtle effect of rotor-wake interaction and result principally from differences between the two types of rotor in the character and strength of the localized interaction between the developing supervortices and the highly loaded blade-tips at the lateral extremities of the rotor. In hover, the increased axial convection rate of the tip vortices appears to result in a favorable redistribution of the loading slightly inboard of the tip of the upper rotor of the coaxial systemKeywords
This publication has 5 references indexed in Scilit:
- A Rational Approach to Comparing the Performance of Coaxial and Conventional RotorsJournal of the American Helicopter Society, 2010
- Efficient High-Resolution Wake Modeling Using the Vorticity Transport EquationAIAA Journal, 2005
- Predicting the Onset of Wake Breakdown for Rotors in Descending FlightJournal of the American Helicopter Society, 2003
- Rotor Wake Modeling for Flight Dynamic Simulation of HelicoptersAIAA Journal, 2000
- The Wake Geometry of a Hovering Helicopter Rotor and Its Influence on Rotor PerformanceJournal of the American Helicopter Society, 1972