Using a generic medium-lift class helicopter, the physical mechanisms for improving helicopter performance in cruise and for increasing the maximum speed and maximum load capability has been investigated. Various potential blade morphing concepts were examined based on an understanding of the physics. Among the examined concepts, the variable rotor speed and the variable blade chord approaches demonstrated a significant benefit for improving the rotor performance in cruise. Further improvements of the rotor performance could be achieved by using the variable rotor speed combined with a 1/rev chord control approach. In addition, the variable rotor speed is an approach that does not consume any additional power. Changing the blade chord needs much less power due to the fact that the chordwise aerodynamic force on the trailing edge of the airfoil is very small. Although the investigations were performed using the generic medium-lift class helicopter, the conclusions of this study can be applied to all helicopters with similar configurations (single main rotor). This is due to the fact that compromises are always required with fixed rotor parameters to obtain a good hover performance, a good high-speed performance, and a good maneuvering performance. Therefore, there is always room for improvement of rotor performance in cruise through the variable rotor speed. Optimization, however, has to be made for various configurations, environmental conditions, and flight conditions. Various blade morphing technologies geared toward increasing the maximum forward speed and the maximum load capability while keeping the required power at a low level were also examined. Among them, the 1/rev dynamic morphing shows promise in terms of rotor performance improvement for the maximum forward speed and the maximum load capability. In particular, the 1/rev dynamic chord was found to be an effective way to improve the aircraft maximum forward speed and maximum load capability while, at the same time, keeping the required power at a low level. The dynamic chord improves the blade section operating conditions by making the angle of attack of the blade sections more uniform around the azimuth. It also improves the rotor performance by delaying the retreating blade stall and reducing the drag and the compressibility effect on the rotor advancing side.
Dynamic blade shape for improved helicopter rotor performance
Dynamische Profilverformung für eine verbesserte Hubschrauber-Rotorleistung
Journal of the American Helicopter Society ; 55 , 3 ; 032008/1-032008/11
2010
11 Seiten, 33 Bilder, 1 Tabelle, 24 Quellen
Aufsatz (Zeitschrift)
Englisch
Dynamic Blade Shape for Improved Helicopter Rotor Performance
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