Study on the Mechanism of the Variable-Speed Rotor Affecting Rotor Aerodynamic Performance

Abstract

Abstract:The variable-speed rotor has proven to be a promising means to improve helicopter performance. Previous investigations on the aeromechanics of the variable-speed rotor are scarce. This work studies the mechanism of the variable-speed rotor affecting the rotor aerodynamic performance by means of dimensionless parameter analysis and reveals the various effect mechanisms under the various flight speeds and take-off weights. The current work shows that, during hover, the variable-speed rotor improves the rotor aerodynamic performance by reducing the blade dynamic pressure, while the non-uniform thrust distribution is attributed to the reduced rotor speed suppresses the performance improvement. In slow forward flight, the blade dynamic pressure reduction improves the rotor aerodynamic performance. In cruise and fast forward flight, both the blade dynamic pressure and advancing blade tip compression loss reductions improve the rotor aerodynamic performance. The study also shows that in forward flight, the rotor loading is smaller, and the effect of reducing the advancing blade tip compression loss through the variable-speed rotor is greater.

Design and Validation of a Passive Camber Morphing Concept for Rotorcraft

“…Han et al [13] mentions rotor speed change in the range of (100%-53.8%), (100%-31.5%) and (100%-39.2%), explaining that increasing the range of the variation of the rotor speed is beneficial to the helicopter performance. Also, the influence of speed reduction in hover, low-speed, and high speed can be different [14]. In the studies performed by Han et al [15], the helicopter performance benefits by VSR and variable blade twist are investigated.…”

Optimal Segment Control of Active Twist Rotor for Power Reduction in Forward Flight

“…Morphing techniques with variable parameters were utilized in order to enhance the rotor performance [1,2]. Extendable-chord rotors [3,4], variable-span rotors [5,6], and variable-speed rotors [7][8][9] have been examined in order to alleviate the dynamic stall and drag divergence by optimizing the trim states. Higher Harmonic Control (HHC) was originally used for reducing vibration and noise [10,11].…”