THE DEVELOPMENT OF PRESSURE BASED COMPRESSIBLE SOLVER WITH ACTUATOR MODEL FOR COAXIAL ROTOR ANALYSIS

Purpose This paper aims to present bifurcation analysis of a magnetically supported coaxial rotor model in auxiliary bearings, which includes gyroscopic moments of disks and geometric coupling of the magnetic actuators. Design/methodology/approach Ten nonlinear equations of motion were solved using the Runge–Kutta method. The vibration responses were analyzed using dynamic trajectories, power spectra, Poincaré maps, bifurcation diagrams and the maximum Lyapunov exponent. The analysis was carried out for different system parameters, namely, the inner shaft stiffness, inter-rotor bearing stiffness, auxiliary bearing stiffness and disk position. Findings It was shown that dynamics of the system could be significantly affected by varying these parameters, so that the system responses displayed a rich variety of nonlinear dynamical phenomena, including quasi-periodicity, chaos and jump. Next, some threshold values were provided with regard to the design of appropriate parameters for this system. Therefore, the proposed work can provide an effective means of gaining insights into the nonlinear dynamics of coaxial rotor–active magnetic bearing systems with auxiliary bearings in the future. Originality/value This paper considered the influences of the inner shaft stiffness, inter-rotor bearing stiffness, auxiliary bearing stiffness and disk position on the bifurcation behavior of a magnetically supported coaxial rotor system in auxiliary bearings.

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Inflow Prediction and First Principles Modeling of a Coaxial Rotor Unmanned Aerial Vehicle in Forward Flight

International Journal of Aeronautical and Space Sciences ◽

10.5139/ijass.2015.16.4.614 ◽

2015 ◽

Vol 16 (4) ◽

pp. 614-623 ◽

Cited By ~ 2

Author(s):

Mohammad Harun-Or-Rashid ◽

Jun-Beom Song ◽

Young-Seop Byun ◽

Beom-Soo Kang

Keyword(s):

Unmanned Aerial Vehicle ◽

First Principles ◽

Forward Flight ◽

Coaxial Rotor ◽

Aerial Vehicle ◽

Inflow Prediction

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Unsteady loads for coaxial rotors in forward flight computed using a vortex particle method

The Aeronautical Journal ◽

10.1017/aer.2018.8 ◽

2018 ◽

Vol 122 (1251) ◽

pp. 693-714 ◽

Cited By ~ 13

Author(s):

J. Tan ◽

Y. Sun ◽

G. N. Barakos

Keyword(s):

Flow Model ◽

Particle Method ◽

Reversed Flow ◽

Aerodynamic Loads ◽

Unsteady Aerodynamic ◽

Vortex Particle Method ◽

Coaxial Rotor ◽

Aerodynamic Interaction ◽

Coaxial Rotors ◽

Vortex Particle

ABSTRACTRecent advances in coaxial rotor design have shown benefits of this configuration. Nevertheless, issues related to rotor-head drag, aerodynamic performance, wake interference, and vibration should also be considered. Simulating the unsteady aerodynamic loads for a coaxial rotor, including the aerodynamic interactions between rotors and rotor blades, is an essential part of analysing their vibration characteristics. In this article, an unsteady aerodynamic analysis based on a vortex particle method is presented. In this method, a reversed-flow model for the retreating side of the coaxial rotor is proposed based on an unsteady panel technique. To account for reversed flow, shedding a vortex from the leading edge is used rather than from the trailing edge. Moreover, vortex-blade aerodynamic interactions are accounted for. The model considers the unsteady pressure term induced on a blade by tip vortices of other blades, and thus accounts for the aerodynamic interaction between the rotors and its contribution to the unsteady airloads. Coupling the reversed-flow model and the vortex-blade aerodynamic interaction model with the viscous vortex-particle method is used to simulate the complex wake of the coaxial rotor. The unsteady aerodynamic loads on the X2 coaxial rotor are simulated in forward flight, and compared with the results of PRASADUM (Parallelized Rotorcraft Analysis for Simulation And Design, developed at the University of Maryland) and CFD/CSD computations with the OVERFLOW and the CREATE-AV Helios tools. The results of the present method agree with the results of the CFD/CSD method, and compare to it better than the PRASADUM solutions. Furthermore, the influence of the aerodynamic interaction between the coaxial rotors on the unsteady airloads, frequency, wake structure, induced flow, and force distributions are analysed. Additionally, the results are also compared against computations for a single-rotor case, simulated at similar conditions as the coaxial rotor. It is shown that the effect of tip vortex interaction plays a significant role in unsteady airloads of coaxial rotors at low speeds, while the rotor blade passing effect is obviously strengthened at high-speed.

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Development and Analysis of a Coaxial Rotor Test Bench in Axial Flow Conditions

Notes on Numerical Fluid Mechanics and Multidisciplinary Design - New Results in Numerical and Experimental Fluid Mechanics XIII ◽

10.1007/978-3-030-79561-0_32 ◽

2021 ◽

pp. 335-344

Author(s):

Jan-Arun Faust ◽

Nikolai Herzog ◽

Michael Cerny ◽

Christian Breitsamter

Keyword(s):

Test Bench ◽

Axial Flow ◽

Flow Conditions ◽

Coaxial Rotor

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Iterative Blade Element Momentum Theory for Predicting Coaxial Rotor Performance in Hover

Journal of the American Helicopter Society ◽

10.4050/jahs.65.042005 ◽

2020 ◽

Vol 65 (4) ◽

pp. 1-12

Author(s):

Seongkyu Lee ◽

Maxime Dassonville

Keyword(s):

Figure Of Merit ◽

Measurement Data ◽

Separation Distance ◽

Blade Element Momentum Theory ◽

Momentum Theory ◽

Coaxial Rotor ◽

Aerodynamic Properties ◽

Induced Velocity ◽

Empirical Constants ◽

Blade Element

This paper presents a new blade element momentum theory (BEMT) for a coaxial rotor in hover. The new BEMT iteratively solves the upper and lower rotor induced velocities to account for the mutual rotor-to-rotor interaction. The upper rotor induced velocity is affected by the lower rotor thrust and induced velocity, whereas the lower rotor induced velocity is affected by the upper rotor thrust and induced velocity. Two empirical constants are included in each rotor calculation. This new BEMT provides the performance of each rotor as a function of the rotor separation distance. The new BEMT is validated with measurement data for two coaxial rotor experiments. The first experiment validates the thrust to power coefficients at a given separation distance. The second experiment validates each rotor's figure of merit, thrust, power, interference loss factors, etc. as a function of the rotor separation distance. It is shown that the BEMT captures the trends and magnitudes of the performance as a function of the rotor separation distance compared to the measurement data. Detailed radial distributions of aerodynamic properties are also presented at several separation distances.

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Blade Passage Loads and Deformation of a Coaxial Rotor System in Hover

Journal of Aircraft ◽

10.2514/1.c035469 ◽

2019 ◽

Vol 56 (6) ◽

pp. 2144-2157 ◽

Cited By ~ 2

Author(s):

Daiju Uehara ◽

Jayant Sirohi ◽

Roland Feil ◽

Jürgen Rauleder

Keyword(s):

Rotor System ◽

Blade Passage ◽

Coaxial Rotor

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Spectrum Analysis of a Coaxial Dual-Rotor System with Coupling Misalignment

Shock and Vibration ◽

10.1155/2020/5856341 ◽

2020 ◽

Vol 2020 ◽

pp. 1-19

Author(s):

Hongxian Zhang ◽

Liangpei Huang ◽

Xuejun Li ◽

Lingli Jiang ◽

Dalian Yang ◽

...

Keyword(s):

Spectral Characteristics ◽

Element Model ◽

Rotor System ◽

Harmonic Frequencies ◽

Coaxial Rotor ◽

Outer Rotor ◽

Frequency Components ◽

Harmonic Resonance ◽

The Finite Element Model ◽

Engine Rotor

The finite element model of a dual-rotor system was established by Timoshenko beam element. The dual-rotor system is a coaxial rotor whose supporting structure is similar to that of an aero-engine rotor system. The inner rotor is supported by three bearings, which makes it a redundantly supported rotor. The outer rotor connects the inner rotor by an intershaft bearing. The spectrum characteristics of the dual-rotor system under unbalanced excitation and misalignment excitation were analysed in order to study the influence of coupling misalignment of the inner rotor on the spectral characteristics of the rotor system. The results indicate that the vibration caused by the misaligned coupling of the inner rotor will be transmitted to the outer rotor through the intershaft bearing. Multiple harmonic frequency components, mainly 1x and 2x, will be excited by the coupling misalignment. The amplitudes of all harmonic frequencies increase with the misalignment in both the inner and outer rotors. The vibration level of the outer rotor affected by the misalignment is lower than that of the inner rotor because it is far from the misaligned coupling. Harmonic resonance occurs when any harmonic frequencies of the misalignment response coincide with a natural frequency of the system. In order to verify the theoretical model, experiments are performed on a test rig. Both the experimental and simulation results are in good accordance with each other.

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