Aeroelastic analysis of a shipboard helicopter rotor with ship motions during engagement and disengagement operations

Yang

Aerospace Science and Technology

2018

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Extendable blade sections are investigated as a method for reducing rotor power and improving helicopter performance. A validated helicopter power prediction method, based on an elastic beam model is utilized. The static extendable chord can deliver a rather small power reduction in hover, and significant power savings at high speed flight, however, the cruise power is increased. In hover, the active chord is best deployed in the middle part of the blade, and just inboard of the tip at high speed flight. The increase in chord length can lead to power savings at high speed flight but the benefits decrease in other speeds. The 1/rev dynamically extendable chord can lead to an overall power reduction over the speed range of a helicopter. The best deployment location is at the blade tip, which is different from the statically extendable chord. It is best extended out in the retreating side, and retracted back in the advancing. The power reduction by the 1/rev dynamically extendable chord increases with the increase in the length of the chord extension and takeoff weight of the helicopter. Generally, a lower harmonic extendable chord can save more power than one actuated at higher harmonics. The dynamic chord can reduce more power than the corresponding static chord.

Section: Performance Prediction Methodsmentioning

confidence: 99%

Extendable chord for improved helicopter rotor performance

Yang

Aerospace Science and Technology

2018

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“…It includes a main rotor model, a fuselage model, a tail rotor model and a propulsive trim method. The rotor modeling follows [21,22]. A moderate deflection beam model is employed to describe the elastic deformations of the rotor blades.…”

Section: Empirical Modelmentioning

confidence: 99%

Helicopter performance improvement by variable rotor speed and variable blade twist

Pastrikakis

Aerospace Science and Technology

2016

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Variable rotor speed and variable blade twist are combined to reduce rotor power and improve helicopter performance.Two modeling methods are respectively utilized. One is based on an empirical aerodynamic model and the other is based on CFD (computational fluid dynamics). The flight data of the UH-60A helicopter is used to validate the methods. The predictions of the rotor power by the empirical method are in good agreement with the test data and the CFD method, which verifies the application of present methods in analyzing helicopter performance. The analyses indicate that significant rotor power reduction can be achieved by decreasing rotor speed. It is not appropriate to decrease the rotor speed too much in high forward flight. More power reduction can be attained by varying rotor speed than by variable blade twist.The individual variation of rotor speed or blade twist can reduce the rotor power by 17.8% or 10.4%, at a forward speed 250 km/h and weight coefficient of 0.0065. A combination of rotor speed reduction and blade twist can save 20.9%. The maximum power reduction increases with forward speed and then decreases. The optimal performance improvement occurs at the medium to high forward speed. With increasing takeoff weight, the benefit in power saving decreases. Variable blade twist has the potential in reducing blade loads introduced by variable rotor speed.

“…To evaluate the potential of the dynamically extendable chord in controlling the rotor loads, an aeroelastic model is used, consisting of a main rotor, fuselage, tail rotor and a propulsive trim method. The rotor model follows [13,14], adopting a beam structural model, an airfoil aerodynamic model and an rotor induced velocity model. The employed elastic beam model allows for moderate deflections, and captures the nonlinear coupling effects between deformations of advanced helicopter blades.…”

Section: A Rotor Loadsmentioning

confidence: 99%

“…The induced velocity over the rotor disk is captured by the Pitt-Peters inflow model [15]. Assembling the structural, kinetic, and aerodynamic terms yields the equations of motion based on the generalized force formulation [13]. The Newmark integration method without numerical dissipation ( = .…”

Section: A Rotor Loadsmentioning

confidence: 99%

Rotor Loads Reduction by Dynamically Extendable Chord

2020

AIAA Journal

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Dynamically extendable blade chord sections show promise for reducing helicopter rotor loads. A rotor model based on elastic beam concept, and capable to predict helicopter power, is utilized. A stiff in-plane four bladed rotor with the shape similar to the UH-60A rotor, is used as baseline for comparisons. For the control of the 4/rev vertical hub force, it is not beneficial to actuate the extendable chord at hover and low speed flight. At a high speed of 270km/h, the extendable chord, with a width of 10% rotor radius and responded to an extension of 10% chord length, obtained a maximum force reduction of 89.4%. The magnitude of the dynamic chord needs to be optimized according to the flight state. The performance can be enhanced by increasing the extension or width of the dynamic chord. The dynamically extendable chord was not suitable for reducing the 2/rev blade flapwise root bending moment. A 3/rev dynamic chord extension though showed great potential in reducing the 3/rev flapwise root bending moment and the 4/rev rotor rolling and pitching moments, simultaneously. The effectiveness of a 5/rev dynamic chord in reducing the 4/rev rotor rolling or pitching moment degraded significantly compared with a 3/rev actuation.