P. J. Gamez-Montero
Bio: P. J. Gamez-Montero is an academic researcher from Polytechnic University of Catalonia. The author has contributed to research in topic(s): Gear pump & Gerotor. The author has an hindex of 15, co-authored 45 publication(s) receiving 613 citation(s).
Abstract: The flow in the suction chamber of an external gearpump is numerically analysed. The evolution of the boundaries of the domain is very complex, and an arbitrary Lagrangian–Eulerian (ALE) formulation is used with mesh deformation and local remeshing. Nevertheless, a mesh replacement strategy is also adopted in order to avoid skewed meshes and allow for simulation of solid contact between gears. This process approximates a more realistic flow behaviour when the working pressure is larger than 10 bar, which is an important in fluid power systems where the pressure is usually greater than 100 bar. Aside from the laminar model, which fails as a result of the vortex configuration in the suction chamber, Standard k – e , RNG k – e , Realizable k – e and Reynolds Stress Models (RSM) are tested. The numerical flow is compared with experimental data obtained with Time Resolved Particle Image Velocimetry. Although all of the models failed in some respect, the RSM and RNG k – e were the best choice provided its behaviour close to the gearing zone and general shape of the vortex distribution.
Abstract: The work presented in this article demonstrates the use of an empirical and simplified approach based on an optical technique and a home-made ad hoc code that give knowledge of the shape and fallin...
Abstract: The aim of the approach of this paper is to characterise contact stress of a trochoidal-gear set when it works as part of the hydraulic machine. It is important to know that the contact stress forces in a trochoidal-type machine is important because the machine cannot be adjusted for wear. The main difficulty in calculating the contact forces is to determine the forces that are transmitted through each contact point. Since there are many points of contact, at any instant, the problem is statically indeterminate. The first part of this paper presents a simplified analytical model of a trochoidal-type machine when friction at the contact points is neglected. From this study, the performance of the gear set is evaluated through the calculation of the normal maximum contact stress in the gear teeth. Then the second part of the paper presents a finite element model of the same machine. The analysis of both models is for quasi-static conditions. An experimental approach using a prototype model of the gear set provides the maximum contact stress on a pair of teeth through photoelasticity measurement techniques of the same machine. The results from the two models and the experimental work are compared and important conclusions are drawn and discussed.
Abstract: Analytical and experimental investigations of typical hydraulic cylinders have indicated that their load capacities are significantly different from those obtained from simple buckling analysis of idealized systems. In any case, an increase in the friction coefficient at the restrained ends changes the actuator's limit load, while an increase in the initial maximum deflection (initial misalignment) decreases the limit load. A common practice of most cylinder manufacturers is to use a safety factor (between 2.5 and 4) to determine the service load after the critical load (buckling) is obtained by simple analytical procedures treating the cylinder as a perfect stepped column. The intricate aspects of friction effects have been deliberately left aside in this present work. Nevertheless, friction and interaction between mechanism and actuator in the buckling characteristics will be presented in the ongoing paper, which will follow this work. Authors know that, in a real system, the cylinder tube–rod interface is not rigid. Due to the flexibility of guide rings and clearances between components, misalignment (an angular deflection which increases with increasing axial load) exits at the interface. When initial imperfection angle exists, there is no sudden buckling. Then, stresses and deflections increase with increasing load. After repetitive use, the tolerance between the parts will become larger, consequently increasing the initial deflection, which has been proved to considerably decrease the load capacities of the power cylinders. From this analysis, a theoretical and experimental work has been carried out in order to show the advantages and disadvantages of the current design methods, characterizing the critical factors that cause the collapse and proposing useful design criterions. The present work aims to describe the behaviour of actuators under load capacity with experimental validation.
TL;DR: The aim of the present work is to contribute to the understanding of the fluid flow inside an EGP by means of a complete three-dimensional (3D) parallel simulation on a cluster.
Abstract: Recently several works have been published on numerical simulation of an external gear pump (EGP). Such kinds of pumps are simple and relatively inexpensive, and are frequently used in fluid power applications, such as fluid power in aeronautical, mechanical, and civil engineering. Nevertheless, considerable effort is being undertaken to improve efficiency and reduce noise and vibration produced by the flow and pressure pulsations. Numerical simulation of an EGP is not straightforward principally for two main reasons. First, the gearing mechanism between gears makes it difficult to handle a dynamic mesh without a considerable deterioration of mesh quality. Second, the dynamic metal-metal contact simulation is important when high pressure outflow has to be reproduced. The numerical studies published so far are based on a two-dimensional (2D) approximation. The aim of the present work is to contribute to the understanding of the fluid flow inside an EGP by means of a complete three-dimensional (3D) parallel simulation on a cluster. The 3D flow is simulated in a LINUX cluster with a solver developed with the OPENFOAM Toolbox. The hexahedral mesh quality is maintained by periodically replacing the mesh and interpolating the physical magnitudes fields. The meshing contact point is simulated with the viscous wall approach, using a viscosity model based on wall proximity. The results for the flow rate ripples show a similar behavior to that obtained with 2D simulations. However, the flow presents important differences inside the suction and the discharge chambers, principally in the regions of the pipes' connection. Moreover, the decompression slot below the gearing zone, which can not be simulated with a 2D approximation, enables a more realistic simulation of a contact ratio greater than 1. The results are compared with experimental measurements recently published.
30 Dec 2017
TL;DR: A review on machinery prognostics following its whole program, i.e., from data acquisition to RUL prediction, which provides discussions on current situation, upcoming challenges as well as possible future trends for researchers in this field.
Abstract: Machinery prognostics is one of the major tasks in condition based maintenance (CBM), which aims to predict the remaining useful life (RUL) of machinery based on condition information. A machinery prognostic program generally consists of four technical processes, i.e., data acquisition, health indicator (HI) construction, health stage (HS) division, and RUL prediction. Over recent years, a significant amount of research work has been undertaken in each of the four processes. And much literature has made an excellent overview on the last process, i.e., RUL prediction. However, there has not been a systematic review that covers the four technical processes comprehensively. To fill this gap, this paper provides a review on machinery prognostics following its whole program, i.e., from data acquisition to RUL prediction. First, in data acquisition, several prognostic datasets widely used in academic literature are introduced systematically. Then, commonly used HI construction approaches and metrics are discussed. After that, the HS division process is summarized by introducing its major tasks and existing approaches. Afterwards, the advancements of RUL prediction are reviewed including the popular approaches and metrics. Finally, the paper provides discussions on current situation, upcoming challenges as well as possible future trends for researchers in this field.
01 Jan 1989
Abstract: Arthur Chickering is Distinguished Professor of Higher Education at Memphis State University. On leave from the Directorship of the Center for the Study of Higher Education at Memphis State, he is Visiting Professor at George Mason University. Zelda Gamson is a sociologist who holds appointments at the John W. McCormack Institute of Public Affairs at the University of Massachusetts-Boston and in the Center for the Study of Higher and Postsecondary Education at the University of Michigan.
01 Jan 2016
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01 Jan 1982