scholarly journals Research on modeling and dynamic characteristics of complex coaxial rotor system

2017 ◽  
Vol 19 (3) ◽  
pp. 1524-1545 ◽  
Author(s):  
Fei Wang ◽  
Gui-Huo Luo ◽  
Xi-Guan Yang ◽  
Hai-Tao Cui
Keyword(s):  
Dynamic Characteristics ◽  
Rotor System ◽  
Coaxial Rotor

scholarly journals Dynamic characteristics of the gear-rotor system in compressed air energy storage considering friction effects

2021 ◽  
Vol 12 (1) ◽  
pp. 677-688
Author(s):  
Xinran Wang ◽  
Wen Li ◽  
Dongxu Hu ◽  
Xingjian Dai ◽  
Haisheng Chen
Keyword(s):  
Energy Storage ◽  
Friction Coefficient ◽  
Dynamic Characteristics ◽  
Surface Friction ◽  
Rotor System ◽  
Compressed Air ◽  
Contact Temperature ◽  
Tooth Surface ◽  
Compressed Air Energy Storage ◽  
Rotating Speed

Abstract. The tooth surface friction effects and the resulting tooth surface contact temperature are important factors for the dynamic characteristics of a gear-rotor system in compressed air energy storage (CAES). Therefore, a 3∘ of freedom finite-element model of the system is set up in which the lubrication state of the gear pair, tooth surface friction, contact temperature of the tooth surface, backlash and unbalanced excitation are considered. The friction coefficient is calculated according to the variation of the lubrication state, and the tooth surface contact temperature is derived based on the friction coefficient. The tooth profile deformation caused by the change in the contact temperature is calculated, and the resulting effects on backlash and comprehensive meshing stiffness are considered. The influence of rotating speed, torque load and viscosity of lubricating oil on the system response is studied, and the variation of the friction coefficient, flash temperature of the tooth surface, pressure of the tooth surface and so on are discussed in detail. The results indicate that when the friction coefficient is derived according to the variation of the lubrication state, the variation of the contact temperature of the tooth surface with rotating speed is quite different from that calculated based on a friction coefficient which is set artificially. This leads to a new variation of the dynamic response of the gear-rotor system, and the method of stabilizing the operation of the system is put forward based on the optimization curve for the operation of the system. The results obtained in this paper will provide a reference for the study and design of a gear-rotor system in CAES.

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

2019 ◽  
Vol 56 (6) ◽  
pp. 2144-2157 ◽  
Author(s):  
Daiju Uehara ◽  
Jayant Sirohi ◽  
Roland Feil ◽  
Jürgen Rauleder
Keyword(s):  
Rotor System ◽  
Blade Passage ◽  
Coaxial Rotor

Effect of flight/structural parameters and operating conditions on dynamic behavior of a squeeze-film damped rotor system during diving–climbing maneuver

2020 ◽  
pp. 095441002094261
Author(s):  
Xi Chen ◽  
Xiaohua Gan ◽  
Guangming Ren
Keyword(s):  
Dynamic Characteristics ◽  
Rotor System ◽  
Elastic Support ◽  
Outer Ring ◽  
Squeeze Film ◽  
Inertial Forces ◽  
Oil Film ◽  
Maneuvering Flight ◽  
Mass Unbalance ◽  
Static Eccentricity

During aircraft maneuvering flights, engine's rotor-bearing systems are subjected to parametric excitations and additional inertial forces, which may cause severe vibration and abnormal operation. Based on Lagrange's principle combined with finite element modeling, the differential equations of motion for a squeeze film damped rotor-bearing system mounted on an aircraft in maneuvering flight are derived. Using Newmark–Hilber–Hughes–Taylor integration method, dynamic characteristics of the nonlinear rotor system under maneuvering flight are investigated. The factors are considered, involving mass unbalance, oil–film force, gravity, parametric excitations and additional inertial forces, and instantaneous static eccentricity of journal induced by maneuvering loads. The effects of forward velocity, radius of curvature, rotating speed, mass unbalance, oil–film clearance, and elastic support stiffness on transient responses of rotor system are discussed during diving–climbing maneuver. The results indicate that when the aircraft performs a diving–climbing maneuver in the vertical plane, the journal deviates from the center of oil–film outer ring, and the excursion direction of whirl orbit is determined by centrifugal acceleration and additional gyroscopic moment. The journal whirls asynchronously around the instantaneous static eccentricity and its magnitude is related to the maneuvering loads and the supporting stiffness. Increasing forward velocity or decreasing pitching radius, the rotor vibration will enter earlier into or withdraw later from the relatively large eccentricity. Rotating near critical speeds or excessive mass unbalances should be prevented during maneuvering flights. For large maneuver, the oil–film radial clearance needs to be enlarged properly to avoid hard contact between journal and outer ring. In addition, the stiffness of elastic support needs to be appropriately determined for damping performance. Overall, it provides a flexible approach with good expandability to predict dynamic characteristics of on-board squeeze-film damped rotor system during maneuvering flights in the design process.

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

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.

scholarly journals Dynamics of a rotor system coupled with water-lubricated rubber bearings

2018 ◽  
Vol 232 (23) ◽  
pp. 4263-4277 ◽  
Author(s):  
YF Shi ◽  
M Li ◽  
GH Zhu ◽  
Y Yu
Keyword(s):  
Elastic Deformation ◽  
Dynamic Characteristics ◽  
Hydrodynamic Lubrication ◽  
Dynamic Performance ◽  
Elastohydrodynamic Lubrication ◽  
Rotor System ◽  
Critical Speeds ◽  
Rotor Systems ◽  
Mass Unbalance ◽  
Rubber Bearings

Dynamic behaviour is significantly important in the design of large rotor systems supported on water-lubricated rubber bearings. In this study, the mathematical model of elastohydrodynamic lubrication of the bearing is established based on the theory of hydrodynamic lubrication after considering the elastic deformation of rubber, and the dynamic characteristics of water-lubricated rubber bearings are analysed under small perturbation conditions according to the load increment method and the finite difference method. Next, the differential equation of rotor systems coupled with the water-lubricated rubber bearing is deduced using Lagrange’s approach, and its critical speeds, stability, and unbalanced responses are analysed in detail. The numerical results show that several parameters, such as the eccentricity, length–diameter ratio, and clearance of bearing and the rotating speed of the rotor, have a great impact on the dynamic performance of water-lubricated rubber bearings, and this influence cannot be ignored, especially in the case of large eccentricity ratios. The dynamic characteristics of rotor systems guided by water-lubricated rubber bearings reveal that the critical speeds are much lower than the ones under the rigid supports because of the elastic deformation, and they also indicate that the rotor system supported on water-lubricated rubber bearings has a weaker stability. In addition, the steady-state responses of the rotor system are analysed when the mass unbalance of the propeller exists, and the effect of the thickness of the rubber liner is also considered.

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