The Experts below are selected from a list of 4677 Experts worldwide ranked by ideXlab platform
Hossein Ghasemi - One of the best experts on this subject based on the ideXlab platform.
-
a novel second order thermal model of stirling engines with consideration of Losses due to the speed of the crack system
Energy Conversion and Management, 2018Co-Authors: Hoseyn Sayyaadi, Hossein GhasemiAbstract:Abstract Very accurate second-order thermal models have been developed for the thermal simulation of Stirling engines in recent years. One of the last ones is the comprehensive polytropic model of Stirling engine called the CPMS model. The accuracy of the CPMS model was found to be sufficient for the nominal operation of a prototype Stirling engine known as the GPU-3 engine. Nevertheless, the accuracy of the CPMS model was drastically reduced at high rotational speeds of the engine. In this paper, power Loss and pressure change due to the inertial force of the crank system were integrated into the CPMS thermal model in order to compensate inaccuracy of the CPMS model at high rotational speeds. Moreover, the effect of rotational speed on the gas temperature in heater and cooler was also incorporated. A precise model for evaluating the Mechanical Friction Loss was also employed and compared with the simple Frictional model of the simple Frictional model used in the CPMS. The model was examined on the GPU-3 engine, and it was found that it has superior accuracy compared to the previous thermal model over the entire working regime of the GPU-3 engine.
Hoseyn Sayyaadi - One of the best experts on this subject based on the ideXlab platform.
-
a novel second order thermal model of stirling engines with consideration of Losses due to the speed of the crack system
Energy Conversion and Management, 2018Co-Authors: Hoseyn Sayyaadi, Hossein GhasemiAbstract:Abstract Very accurate second-order thermal models have been developed for the thermal simulation of Stirling engines in recent years. One of the last ones is the comprehensive polytropic model of Stirling engine called the CPMS model. The accuracy of the CPMS model was found to be sufficient for the nominal operation of a prototype Stirling engine known as the GPU-3 engine. Nevertheless, the accuracy of the CPMS model was drastically reduced at high rotational speeds of the engine. In this paper, power Loss and pressure change due to the inertial force of the crank system were integrated into the CPMS thermal model in order to compensate inaccuracy of the CPMS model at high rotational speeds. Moreover, the effect of rotational speed on the gas temperature in heater and cooler was also incorporated. A precise model for evaluating the Mechanical Friction Loss was also employed and compared with the simple Frictional model of the simple Frictional model used in the CPMS. The model was examined on the GPU-3 engine, and it was found that it has superior accuracy compared to the previous thermal model over the entire working regime of the GPU-3 engine.
Diew, Mohamadou Bocar - One of the best experts on this subject based on the ideXlab platform.
-
Contribution à la compréhension des mécanismes d'action des additifs modificateurs de frottement et du couplage additif/surface dans tous les régimes de lubrification
2013Co-Authors: Diew, Mohamadou BocarAbstract:Le moteur à combustion, utilisé dans l’automobile est en perpétuelle évolution pour des raisons économiques et écologiques. Pour parvenir à de faibles consommations de carburant et émissions polluantes, l’un des axes étudiés est la réduction des pertes mécaniques par frottement du moteur qui constituent 15 à 20% de la consommation totale d’énergie du moteur. 50% de ces frottements proviennent des contacts Segment-Piston- Chemise et de la liaison Maneton-Bielle-Coussinet. De ce fait la compréhension de la tribologie de ce contact, l’optimisation de la lubrification et le vieillissement des lubrifiants deviennent primordiaux. L’objectif de cette thèse est d’étudier les mécanismes de lubrification de ces contacts segment/chemise et maneton/coussinet, et en particulier de comprendre l’influence du couplage additif, surface et matériau dans les différentes régimes de lubrification. Il s’agira de répondre à la question : comment maîtriser le frottement et l’usure en contrôlant la chimie du lubrifiant, la topographie et le matériau ? La démarche expérimentale choisie s’appuie sur l’analyse du comportement tribologique de deux additifs modificateurs de frottement sans cendres d’une part, puis sur l’impact du matériau et enfin sur l’influence de la topographie d’autre part. L’analyse de la cinétique d’évolution du coefficient de frottement et des traces d’usure en régime limite ont notamment permis d’identifier les mécanismes de réduction de frottement induits par les deux modificateurs étudiés.The combustion engine used in automotive industry is constantly changing for economic and ecological reasons. To achieve low fuel consumption and pollutants emissions, one of research axes studied is the reduction of the Mechanical Friction Loss of the motor which constitute 15-20 % of the total energy consumption of the engine. 50% of these come from Friction contacts cylinder /piston rings and conrod bearing. Thereby understanding of tribology of the contact, optimizing lubrication and lubricants aging become paramount. The objective of this thesis is to study the mechanisms of lubrication of these contact (piston ring/cylinder and conrod bearing), and in particular to understand the influence of the additive coupling surface and material in the different lubrication regimes. This will answer the question : how to control the Friction and wear by controlling the chemistry of the lubricant, the topography and the material ? The experimental approach chosen is based on the analysis of the tribological behavior of two Friction modifiers additives ashless at first time, and on the impact of material and finally the influence of topography on the second time. XPS Analysis of the evolution of the coefficient of Friction and wear track under boundary regime have enabled to identify mechanisms to reduce Friction induced by the two modifiers studied
J S Park - One of the best experts on this subject based on the ideXlab platform.
-
development of a highly efficient hard disk drive spindle motor with a passive magnetic thrust bearing and a hydrodynamic journal bearing
Journal of Applied Physics, 2005Co-Authors: G H Jang, J S ParkAbstract:This article presents a highly efficient hard disk drive (HDD) spindle motor with a passive magnetic thrust bearing and a hydrodynamic journal bearing. It eliminates the Mechanical Friction Loss of a thrust bearing which is around 14% of total power consumption of a 3.5 in. HDD spindle motor, by replacing a conventional hydrodynamic thrust bearing with a passive magnetic thrust bearing. The passive magnetic thrust bearing using permanent magnets is inherently unstable in radial direction. However, the radial hydrodynamic force of the hydrodynamic journal bearing counterbalances the radial magnetic force of magnetic thrust bearing to achieve the stability as the motor spins up. Numerical analysis is performed to verify feasibility of the proposed system.
G H Jang - One of the best experts on this subject based on the ideXlab platform.
-
development of a highly efficient hard disk drive spindle motor with a passive magnetic thrust bearing and a hydrodynamic journal bearing
Journal of Applied Physics, 2005Co-Authors: G H Jang, J S ParkAbstract:This article presents a highly efficient hard disk drive (HDD) spindle motor with a passive magnetic thrust bearing and a hydrodynamic journal bearing. It eliminates the Mechanical Friction Loss of a thrust bearing which is around 14% of total power consumption of a 3.5 in. HDD spindle motor, by replacing a conventional hydrodynamic thrust bearing with a passive magnetic thrust bearing. The passive magnetic thrust bearing using permanent magnets is inherently unstable in radial direction. However, the radial hydrodynamic force of the hydrodynamic journal bearing counterbalances the radial magnetic force of magnetic thrust bearing to achieve the stability as the motor spins up. Numerical analysis is performed to verify feasibility of the proposed system.