Rapid dynamic load estimation procedure for lifting propellers in forward flight

CEAS Aeronautical Journal, vol. 16, pp. 1105–1125

Abstract

Abstract Lifting propellers operate at oblique inflow and thus encounter severe dynamic loads during forward flight, impacting structural integrity, fatigue, and vibration. Numerical optimization approaches consider aerodynamic, structural mechanical, and aeroacoustic aspects within preliminary design. To also account for dynamic loads during forward flight, a novel procedure allows their rapid estimation. Based on steady-state simulations combining strip theory and finite beam elements, aerodynamic excitation, damping, and stiffness are defined in the frequency domain. Loads are derived through a linear inflow model and quasi-steady aerodynamics. Damping and stiffness loads are linearized and transferred into matrix form to calculate the frequency response. The computationally expensive need for simulations in the time domain is thus avoided. Applicability extends to both fixed and variable pitch lifting propellers utilized in large multicopters for cargo or passenger transportation. Comparisons to time-marching simulations show good agreement with deviations of approximately 10 %. The analytical derivation yields physical insights to understand and reduce dynamic loads and their magnification due to resonance.

Authors 5

1. Felix Möhren corresponding Aachen Faculty of Aerospace Engineering Institute of Structural Mechanics and Lightweight Design

   RWTH Aachen University · FH Aachen

   Affiliation as printed

   Faculty of Aerospace Engineering, FH Aachen UAS, Hohenstaufenallee 6, 52064, Aachen, NRW, Germany

   Institute of Structural Mechanics and Lightweight Design, RWTH Aachen University, Wüllnerstrasse 7, 52062, Aachen, NRW, Germany

2. Ole Bergmann Aachen Faculty of Aerospace Engineering

   RWTH Aachen University · FH Aachen

   Affiliation as printed

   Faculty of Aerospace Engineering, FH Aachen UAS, Hohenstaufenallee 6, 52064, Aachen, NRW, Germany

3. Frank Janser Aachen Faculty of Aerospace Engineering

   RWTH Aachen University · FH Aachen

   Affiliation as printed

   Faculty of Aerospace Engineering, FH Aachen UAS, Hohenstaufenallee 6, 52064, Aachen, NRW, Germany

4. Carsten Braun Aachen Faculty of Aerospace Engineering

   RWTH Aachen University · FH Aachen

   Affiliation as printed

   Faculty of Aerospace Engineering, FH Aachen UAS, Hohenstaufenallee 6, 52064, Aachen, NRW, Germany

5. Kai‐Uwe Schröder Aachen Institute of Structural Mechanics and Lightweight Design

   RWTH Aachen University

   Affiliation as printed

   Institute of Structural Mechanics and Lightweight Design, RWTH Aachen University, Wüllnerstrasse 7, 52062, Aachen, NRW, Germany