Transactions of the Canadian Society for Mechanical Engineering
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Volume 38 (2014), Issue 4
Dynamic two-dimensional nonlinear vibration modeling and analysis for shield TBM cutterheads driving system
Xianhong Li, Hiabin Yu, Peng Zeng, Mingzhe Yuan, Lanxiang Sun, Yu Zhao
This paper establishes a general dynamic two-dimensional nonlinear time-varying (TDNLTV) vibration model with multi-drive shaft for shield tunnel boring machine (TBM) cutterhead driving system. Multipleinput and multiple- output (MIMO) state-space vibration model of cutterhead driving system is also presented. TDNLTV vibration model is simulated, and physical parameters’ effects on the vibration response are detailed investigated. A preliminary approach is proposed to reduce vibration or nonlinear vibration behaviors. Dynamic TDNLTV vibration model provides a basic foundation of fault detection and diagnosis (FDD) and health monitoring for cutterhead driving system.
Combined vibration isolator of disc springs for closed high-speed precision press: design and experiments
F. Jia, F.Y. Xu
The structure, strength, and stiffness of disc springs are analyzed or investigated. Based on the previous studies, two finite element models of combined disc springs are established and their loading and unloading deformation patterns are analyzed to determine the optimal combination of disc springs for a desirable vibration isolator of high-speed press. The structural parameters and loading data of JF75G-200 high-speed press are used for simulation and other experiments. The dynamic working points of disc springs in different combinations are drawn, and complete test data are collected. Results show that combined vibration isolator, an isolator with nonlinearly combined disc springs functioning as a whole for vibration isolation, is the best choice. Results from both simulation and tests confirm the feasibility and validity of the proposed isolator. The isolator can efficiently minimize the vibration of the high-speed press.
Mesh convertence study for 2-D straight-blade vertical axis wind turbine simulations and estimation for 3-D simulations
Saman Naghib Zadeh, Matin Komeili, Marius Paraschivoiu
Mesh resolution requirements are investigated for 2-D and 3-D simulations of the complex flow around a straight-blade vertical axis wind turbine (VAWT). The resulting flow, which may include large separation flows over the blades, dynamic stall, and wake-blade interaction, is simulated by an Unsteady Reynolds-Averaged Navier–Stokes analysis, based on the Spalart–Allmaras (S–A) turbulence model. A grid resolution study is conducted on 2-D grids to examine the convergence of the CFD model. Hence, an averagedgrid residual of y+ > 30 is employed, along with a wall treatment, to capture the near-wall region’s flow structures. Furthermore a 3-D simulation on a coarse grid of the VAWT model is performed in order to explore the influence of the 3-D effects on the aerodynamic performance of the turbine. Finally, based on the 2-D grid convergence study and the 3-D results, the required computational time and mesh to simulate 3-D VAWT accurately is proposed.
Design and performance analysis of an automobile-removable solar system for water and cabin heating
A detachable, automotive solar system for water and passenger compartment heating is developed. The study shows that an adjustable 1 m2 solar collector is sufficient to satisfy the needs of a small group during a short camping trip in Saudi Arabia desert. Also it is found that an adequate water temperature in the storage tank, due to ambient solar heating, is maintained in all cold months, except December when it is insufficient. Among the advantages of the system is its entire operation on renewable solar energy and its ability to heat the car compartment whenever the heated water reaches the required temperature and solar energy is still available.
Preliminary experimental and numerical investigations of the flow in the contraction of a boundary layer wind tunnel
Mohamed Bouriga, Jean-Sébastien Lemyre-Baron, François Morency, Julien Weiss
The time-averaged flow in the contraction of a new boundary-layer wind tunnel is investigated experimentally using Pitot probes and numerically using RANS simulations. Numerical simulations are performed to rule out any risk of flow separation. Experimental and numerical results show a good flow uniformity in the potential core at the contraction exit. Small non-uniformities of the boundary-layer thickness close to the sidewalls centerline are explained by the presence of longitudinal vortices near the sidewall boundary layers. The numerical results confirm an earlier hypothesis concerning the generation of these longitudinal vortices by skew-induced vorticity.
On high bandwidth output pressure control design of hydraulic actuators using quantitative feedback theory
Masoumeh Esfandiari, Nariman Sepehri
Although high bandwidth for the pressure tracking of hydraulic actuators is highly desirable in many industrial applications, it has been a challenge to achieve, mainly due to the natural velocity feedback path in these actuators. In this paper, we investigate the extent to which a fixed-gain linear controller designed based on quantitative feedback theory (QFT) can improve the pressure tracking bandwidth while considering other design criteria including closed-loop stability, disturbance rejection, and robust tracking. Simulation and experimental results are presented to demonstrate that the designed QFT controller satisfies the mentioned design criteria over a wide range of parametric uncertainties, and at the same time provides 6 Hz pressure tracking bandwidth.
Design and analysis of Geneva mechanism with curved slots
A simple yet comprehensive method is proposed for the design of a Geneva indexing mechanism with curved slots. In the proposed approach, conjugate surface theory is used to derive an analytical description of the profile of the curved slots with and without an offset feature. Analytical formulae are then presented for the pressure angle of the Geneva mechanism and the principal curvatures of the curved slots. The effectiveness of an appropriate offset angle in eliminating the singular points and double-points on the curved slot profile is then demonstrated. Finally, a Geneva mechanism is fabricated in order to demonstrate the feasibility of the proposed approach.
Full journal title: Transactions of the Canadian Society for Mechanical Engineering
Abreviated journal title: Trans. Can. Soc. Mech. Eng.
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