RuAviation

Researchers at Perm National Research Polytechnic University (PNRPU), a Russian engineering university, have developed a variable-geometry propeller blade capable of adapting to changing flight regimes. The concept uses embedded piezoelectric actuators to deflect the trailing edge under applied voltage, enabling active flow control.

Propeller efficiency is governed by blade geometry and airfoil shape. Precise shaping directly affects specific fuel consumption, vibration levels, and cabin noise. Deviations from optimal geometry increase drag, degrade flow attachment, and elevate structural and acoustic loads.

The transition from takeoff to acceleration is a critical regime. High angles of attack are required at liftoff to generate thrust. As airspeed increases, this configuration becomes inefficient. Drag rises, flow quality deteriorates, and trailing-edge separation may occur, inducing vibration.

According to the developers, conventional piezoelectric systems provide insufficient actuation authority for meaningful aerodynamic impact. The PNRPU design increases trailing-edge flap deflection by approximately 20% versus comparable solutions.

Conventional pitch-control systems rotate the entire blade using hydraulic or mechanical drives. These assemblies are bulky and can weigh tens of kilograms, increasing fuel burn and system complexity. The proposed piezo actuators weigh only a few hundred grams and locally deform the blade surface with sufficient amplitude to control the flow.

The concept distributes a dense array of piezoelectric cells across the blade surface. Each cell has a tailored electrode orientation optimized for local load conditions. When voltage is applied, each cell deforms in a prescribed manner, collectively producing the required blade bending or twist.

Numerical simulations and virtual prototyping indicate that controlled trailing-edge deflection reduces drag during acceleration and mitigates flow separation. The result is lower vibration, reduced cabin noise, and improved fuel efficiency without a mass penalty.

The next phase includes fabrication of full-scale demonstrators and ground and flight testing. Russian patent RU 2854922 C1 confirms the novelty of the design and its potential for industrial application. The technology is applicable to both propeller-driven aircraft and helicopters.