Bio: M. Khamashta is an academic researcher from Polytechnic University of Catalonia. The author has contributed to research in topic(s): Gear pump & Hydraulic cylinder. The author has an hindex of 4, co-authored 8 publication(s) receiving 154 citation(s).
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.
Abstract: Over the last years, a better comprehension of hydraulic cylinder performance is observed to be a prime objective of many owing to demanding applications. By observing these hydraulic cylinder applications, we see currently proposed models and design criteria do not take into account real factors, and further there are misalignment and boundary conditions in the end supports, mechanism interaction, dust, clearance and imperfections. Since these boundary conditions can develop progressive moments, the ideal simple supported bi-articulated configuration of the actuator is no longer valid, and virtual clamped configuration appears with friction moments that substantially modify the buckling analysis. In a previous work, misalignment effects were studied and discussed. In the present work a study of the influence of friction moments when misalignment effects are deliberately left aside is carried out. In order to separate these two phenomena (friction and misalignment) boundary conditions in a column are analysed. From this analysis, a theoretical and experimental work has been carried out for columns and an actuator characterizing the critical factors that cause the collapse. The aim of this paper is to describe the behaviour of actuators under load capacity with experimental validation when friction moment is taken into account and becomes an unknown variable. Experimental and theoretical results point out the importance and influence of the friction effects in columns and hydraulic cylinders. Then, it is recommended that knowledge of the hydraulic cylinder application to predict its load capacity owing to that direct extrapolation of results from current theories and criterions could lead to incorrect estimations.
••03 Nov 2016
Abstract: A numerical study in a mini trochoidal-gear pump based on an ingenious strategy to adapt the background mesh to the profiles shape and a new boundary condition is presented. The strategy achieves a final background mesh better adapted to the geometries and, additionally, the cells are more homogenous and less distorted when the trochodial-profiles are moved. The new boundary condition to simulate the multi-meshing contact points is applied at every time step by means of the viscous wall approach, a home-made ad-hoc code, which has been integrated in an OpenFOAM solver that also includes the dynamic mesh functionality by deforming the mesh following the trochoidal-gear rotation. The presented numerical study establishes the basis that will allow simulating more realistic aspects of a new design of a mini trochoidal-gear pump once the need for a continuous fluid domain is overcome reproducing actual contacts between the rotors and will guide to a better understanding of the new design.
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.
Abstract: This paper explains development of the general mathematical model of trochoidal gearing that can be applied for gerotor pumps and cyclo reducers. The model analyzes geometry and physics of the gearing pair in trochoidal pump where the outer gear has one tooth more than the inner gear. The inner gear profile is described by peritrochoid equidistance and the outer gear profile by circular arc. Mathematical model of gearing with clearances is based on the principle of an ideal profile development. Minimum clearance height between teeth profiles in relation to instantaneous gear ratio is determined. The influence of gear profile geometrical parameters on gearing process, clearance height change, and pulsation of drive moment is analyzed and presented in numerical examples. Obtained results can be used for the design of the trochoidal gearing where accurate and silent operation is required. [DOI: 10.1115/1.4005621]
Abstract: In this study, an experimental investigation of an indirect solar dryer integrated with phase change material has been carried out for drying Valeriana Jatamansi. The experimentation has been performed under the climatic conditions of Himalayan region, Solan (latitude − 30.91°N, longitude − 77.09°E), Himachal Pradesh (India) in the month of October-November 2016. Paraffin RT-42 has been used as a phase change material in the dryer. Using this system, the moisture content of rhizomes reduced from 89% to 9% in 5 days as compared to heat pump drying and shade drying, which took 8 days and 14 days, respectively. Results of present study infer that the drying time using phase change material in this setup has reduced by 37.50% and 64.29% when compared to heat pump drying and shade drying, respectively. The dried rhizomes obtained are of superior quality in terms of colour, texture, aroma and bio-medical constituents. Analyses show that by using present setup, total valepotriates obtained were 3.47% as compared to traditional shade drying which yield 3.31%.
Abstract: The mechanism of induction of stresses and deformations in plastic cycloidal gears used in gerotor pumps has been analysed using the finite element method and the ABAQUS program. It has been found that the gear system remains under the influence of the mechanical load resulting from the torque on the pump shaft and the hydraulic load resulting from the activity of pressure in the intertooth displacement chambers. It has also been discovered that the intertooth forces and stresses are formed only in the part of the gear that can be referred to as ‘active’. In the other part of the gear, forces and stresses do not occur, and the part can be referred to as ‘passive’. Another finding of the research is that gear deformations occur such that the teeth of the external gear are deformed and moved in the direction of the active part of the mesh, and the teeth of the internal gear in the direction of the passive part. Thus, radial and axial intertooth clearances are formed, which result in internal leakages in the...
Abstract: A current investigation deals with experimental analysis of the heat transfer behavior and optimum relative width parameter of the solar air channel of aspect ratio of 10.0 with 60° angled broken multiple V-type baffles. The current experiment enclosed a wide range of parameter such as Reynolds number varied from 3000 to 8000, relative width varied from 1.0 to 6.0, relative baffle height of 0.5, relative baffle pitch of 10.0, relative discrete distance of 0.67 and relative gap width of 1.0. The obtained experimental results showed that higher overall thermal performance occurred at a relative baffle width of 5.0. Also, the results reveal that the broken multiple V-type baffles are thermo-hydraulically superior as compared to the other baffles shaped solar air channel.