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Aeroelastic Energy Harvesting on Aircraft

Project Objective

A novel aeroelastic energy-harvesting device mounted on a helicopter blade offers an on-board local power source for embedded wireless sensing applications. However, the energy from flow-induced vibrations requires power management and switching techniques for intermittent operation of the load due to the relatively large power requirements. This technology would facilitate powering structural health monitoring sensors, accelerometers for active vibration control while simultaneously allowing placement of these sensors in areas where batteries or hardwired power is impractical. Figure 1 shows a side view of the device and its intended purpose at the trailing edge of a helicopter blade. The length of the elastic beam element has been exaggerated to show the first bending mode of the proposed thin beam.

Concept

Figure 1: Top view of aeroelastic energy harvester with flexural joints

Project Description

 The velocity at the trailing edge of a helicopter blade would exceed critical flutter airspeed and excite the elastic beam. The energy harvesting device will experience airspeeds of approximately 80 m/s in steady hover and vary sinusoidally between 0 m/s and 160 m/s at 80 m/s (155 knots) forward flight as seen in Figure 2 and Figure 3. The piezoelectric films attached at the base of the elastic beam convert mechanical to electrical energy where strain levels are the highest. Results show that the elastic beam bending frequencies at the onset of flutter occur in a range of desired frequencies when considering power requirements for a low power wireless system. In hover, we can expect oscillations around 120 Hz while in forward flight, we expect a range from 0 Hz to approximately 242 Hz.

Figure 2

Figure 2: Trailing edge airspeed experienced by energy harvesting device as a function of azimuth angle during blade rotation for hover, 40 m/s forward flight, 60 m/s forward flight, and 80 m/s forward flight.

Figure 3

Figure 3: Top view of blade path showing induced velocities in forward flight. The blade experiences a higher airspeed in the advancing side compared to the retreating side. A region of reverse flow is encountered if the tab is placed too close to the hub.

Funding Agencies

  • Sikorsky
  • Cornell Center for Sustainable Future