Whirl flutter of flapped blade rotor systems

Rao, Krishna KV and Sundararajan, D (1969) Whirl flutter of flapped blade rotor systems. Technical Report. National Aeronautical Laboratory, Bangalore, India.

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    Abstract

    With a view to understand the whirl flutter phenomenon in flapped blade rotor systems and also to shed some light in bridging the existing gap between theoretical and experimental results, the equations of motion of an idealised mathematical model of a multi-bladed rotor system were formulated. Generalised aerodynamic forces were obtained from quasi-steady blade element theory. These13; equations were linearised and solved for a symmetric case of the system. The stability boundaries for different hinge offsets of the blades are presented as nacelle frequency parameter for neutral instability against blade flapping frequency parameter. It was found that for a particular value of the flapping frequency parameter, which is a function of blade hinge offset and restraint spring constant at the flapping hinge, the nacelle frequency parameter required for neutral instability is minimum. From these results it can be shown that an optimum flapping hinge position from the whirl flutter point of view can be determined. Low speed wind tunnel experiments were performed on a simplified model with different hinge offset conditions. Both 10 per cent and 13.6 per cent hinge offsets resulted in backward whirl flutter as predicted by theory.

    Item Type: Proj.Doc/Technical Report (Technical Report)
    Uncontrolled Keywords: Whirl flutter;Multi-bladed;Rotor systems;Generalised aerodynamic forces;Blade flapping
    Subjects: AERONAUTICS > Aerodynamics
    Division/Department: Structures Division, Structures Division
    Depositing User: M/S ICAST NAL
    Date Deposited: 19 Dec 2006
    Last Modified: 24 May 2010 09:54
    URI: http://nal-ir.nal.res.in/id/eprint/3721

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