Influence Of Rotational Inertia Research Articles

Dynamic Modeling and Analysis of Nonlinear Compound Planetary System

In the vehicle composite planetary gear transmission system, nonlinear excitations such as time-varying meshing stiffness, backlash and comprehensive error would lead to large vibration and noise, uneven load distribution, unstable operation and other problems. To address these issues, this work focuses on compound planetary gears and develops the bending-torsion coupling nonlinear dynamic model of the system based on the Lagrange equation. There are internal and external multi-source excitations applied to the system. This model is used to study the bending-torsion coupling meshing deformation relationship of each meshing pair along with the translational and torsional directions. The natural frequencies and vibration modal characteristics of the system are extracted from the model, and the influence of rotational inertia and meshing stiffness on the inherent characteristics of the system are studied. The coupling vibration characteristics of the system under operating condition are analyzed in terms of the inherent characteristics and time–frequency characteristics of the system. The simulation results exhibit that the planetary gear system has three modes. The change in natural frequency trajectory has two phenomena: modal transition and trajectory intersection. The main frequencies include engine rotating frequency, meshing frequency and its double frequency, and the rotation frequency and harmonic frequency of the engine have a great influence on the vibration response of the system. Finally, the virtual prototype of the composite planetary system is used to verify the accuracy of the established model from speed, inherent characteristics, meshing force and frequency composition.

Influence of rotational inertia on the runner radial forces of a model pump‐turbine running away through the S‐shaped characteristic region

To enhance the power grid's stability and safety, pumped-storage power stations (PSPSs) have to keep themselves stable and safe strictly. However, instabilities happen frequently in some PSPSs due to the S-shaped characteristics of pump-turbines. When the operating point goes through the S-shaped region, intensive radial forces on the runner could cause shaft swing of the turbine-generator unit. In this study, the runaway transient scenarios of a pump-turbine in a model PSPS were simulated by using a one-dimensional and three-dimensional coupled computational fluid dynamics model, and the influence of the unit rotational inertia on the runner radial forces was investigated. The results show that when the pump-turbine runs in the S-shaped region, large rotational inertia is easier than a small one to induce abrupt increases in runner radial forces. The reason is that large rotational inertia gives slower changes in rotational speed and discharge, providing enough time to generate unstable and uneven flow patterns in the pump-turbine. This indicates that apart from the running away region in the characteristics plane, the running away duration is also essential for the transient instability of a pump-turbine. The finding is different from the traditional understandings and should be considered when selects the rotational inertia of a pump-turbine unit.

Improvement of sinusoidal pitch for vertical-axis hydrokinetic turbines and influence of rotational inertia

In previous study (Chen et al., 2018), performances of a fixed pitch and a sinusoidal pitch H-Darrieus vertical-axis turbine (VAT) are compared by numerical simulations. With an appropriate amplitude of sinusoidal pitching, the power efficiency could be improved by 33%, and the fluctuation in power output, rotation speed and shaft torque are suppressed meanwhile. In this study, to reduce the hydrodynamic resistant torque, the original sinusoidal pitching is modified to keep the pitch angle at zero or at a small initial angle in the downstream half of rotation cycle. Numerical simulation results show this modification increases power efficiency by 20% over that of an original sinusoidal pitch turbine. Furthermore, systemically study confirms that as rotational inertia of rotor increases, the power coefficient and tip-speed ratio do not change much, and the fluctuation in output torque can be dramatically reduced. However, a very large rotational inertia turbine would perform very poor unless the rotor be accelerated over a threshold speed with exterior assistance.

Influence of Rotational Inertia on Performance of a Stand-alone Wind Turbine-Generator System(Analysis for Each Operation Mode)

Influence of Rotational Inertia on Performance of a Stand-alone Wind Turbine-Generator System(Analysis for Each Operation Mode)

Exact Controllability of a Semilinear Thermoelastic System with Control Solely in Thermal Equation

A result concerning the exact controllability of a semilinear thermoelastic system, in which the control term occurs solely in the thermal equation, is derived under the influence of rotational inertia and Lipschitz nonlinearity, subject to the clamped/Dirichlet boundary conditions. In the proof, we make use of the result given by Avalos (Differential and Integral Equations, 2000; 13(4–6):613–630), which states that the corresponding linear system is exact controllable.

Exact controllability of a semilinear thermoelastic system with control and nonlinearity in thermal component only

AbstractA result concerning the exact controllability of semilinear thermoelastic system, in which the control and nonlinear term occurs solely in the thermal equation, is derived under the influence of rotational inertia and Lipschitz nonlinearity, subject to the clamped/Dirichlet boundary conditions. In the proof we make use the result given by Avalos G. [Differential and Integral Equations, 13 (2000), 613‐630] which states that the corresponding linear system is exact controllable. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Influence of rotational inertia on turning performance of theropod dinosaurs: clues from humans with increased rotational inertia.

The turning agility of theropod dinosaurs may have been severely limited by the large rotational inertia of their horizontal trunks and tails. Bodies with mass distributed far from the axis of rotation have much greater rotational inertia than bodies with the same mass distributed close to the axis of rotation. In this study, we increased the rotational inertia about the vertical axis of human subjects 9.2-fold, to match our estimate for theropods the size of humans, and measured the ability of the subjects to turn. To determine the effect of the increased rotational inertia on maximum turning capability, five subjects jumped vertically while attempting to rotate as far as possible about their vertical axis. This test resulted in a decrease in the average angle turned to 20 % of the control value. We also tested the ability of nine subjects to run as rapidly as possible through a tight slalom course of six 90 degrees turns. When the subjects ran with the 9.2-fold greater rotational inertia, the average velocity through the course decreased to 77% of the control velocity. When the subjects ran the same course but were constrained as to where they placed their feet, the average velocity through the course decreased to 65 % of the control velocity. These results are consistent with the hypothesis that rotational inertia may have limited the turning performance of theropods. They also indicate that the effect of rotational inertia on turning performance is dependent on the type of turning behavior. Characters such as retroverted pubes, reduced tail length, decreased body size, pneumatic vertebrae and the absence of teeth reduced rotational inertia in derived theropods and probably, therefore, improved their turning agility. To reduce rotational inertia, theropods may have run with an arched back and tail, an S-curved neck and forelimbs held backwards against the body.

Influence of rotational inertia on the natural vibrations frequency spectrum of a cylindrical shell

Influence of rotational inertia on the natural vibrations frequency spectrum of a cylindrical shell