Load analysis for open rotor aircraft engines
Open rotors can burn less fuel than turbofans because they support large diameters, resulting in high bypass ratios without the drag and weight penalties of a large nacelle. The first ‘unducted fan’ was demonstrated in flight in the late 1980s, but the concept was shelved until recently. Work has revived earlier this decade with the Clean Sky programme taking the lead in advancing the maturity of the open rotor as a possible successor of turbofans. Within the EU-funded project OPTIMAL (Optimised model for accurately measured in-flight loads), researchers developed a new methodology to assess flight loads on the pylon. Specifically, researchers sought to support the assessment of loads encountered by the pylon to which the counter-rotating open rotor is mounted. They adapted an inverse finite element method (FEM) to analyse loads at boundaries such as the pylon-fuselage attachment, with the highest possible accuracy. The FEM method is based on strain, temperature and acceleration measurements collected by a network of optical and conventional sensors. Researchers evaluated the performance of two different network configurations during pylon monitoring. The accuracy of the proposed approach was tested using a scaled pylon mock-up, representative of the real structure. Although inverse FEM proved to be robust in theoretical studies, the desired accuracy of 3 % was not attainable during lab tests. Though OPTIMAL has ended, researchers continue to work on the sensing methodology proposed in combination with structural health monitoring to increase its accuracy. Further applications where identification of dynamic loads is necessary are also being considered.
Keywords
Open rotor, aircraft engine, OPTIMAL, flight loads, finite element method
