scholarly journals Simulation of journal bearing friction in severe mixed lubrication – Validation and effect of surface smoothing due to running-in

2020 ◽  
Author(s):  
David E Sander ◽  
Hannes Allmaier ◽  
Hans Herwig Priebsch
Keyword(s):  
Friction Torque ◽  
Metal Contact ◽  
Solid Base ◽  
Simulation Approach ◽  
Friction Behavior ◽  
Operation Conditions ◽  
Wide Range ◽  
Metal Metal ◽  
Stribeck Curves ◽  
Effect Of Surface

This paper focuses on the friction behavior of jour-nal bearings operating from hydrodynamic to mixedlubrication regime where severe metal-metal contactoccurs. Therefore, friction tests with two differentstatic loads are carried out on the journal bear-ing test-rig from KS Gleitlager. The test resultsin form of Stribeck curves provide a solid base toproof the isothermal elastohydrodynamic simulationapproach. The simulation approach solves the av-eraged Reynolds equation introduced by Patir andCheng and considers metal-metal contact by usingthe Greenwood and Tripp contact model. All nec-essary surface parameters are derived from surfacescans. No less essential in this approach are theexperimentally identified lubricant properties underhigh pressure and high shear rate.The calculated friction torque matches the mea-surement results within the measurement uncertaintyfor a wide range of operation conditions. With thevalidated simulation approach the influence of surfacesmoothing due to metal-metal contact is discussed.Additionally, the limits of a constant boundary coef-ficient are identified and the effects of flow factors arepresented.

scholarly journals Friction of Metals: A Review of Microstructural Evolution and Nanoscale Phenomena in Shearing Contacts

2021 ◽  
Vol 69 (4) ◽  
Author(s):  
Michael Chandross ◽  
Nicolas Argibay
Keyword(s):  
Shear Strength ◽  
Grain Boundary Sliding ◽  
Deformation Mechanisms ◽  
Low Friction ◽  
Friction Behavior ◽  
Important Conclusion ◽  
Fundamental Properties ◽  
Wide Range ◽  
Boundary Sliding ◽  
Metal Interfaces

AbstractThe friction behavior of metals is directly linked to the mechanisms that accommodate deformation. We examine the links between mechanisms of strengthening, deformation, and the wide range of friction behaviors that are exhibited by shearing metal interfaces. Specifically, the focus is on understanding the shear strength of nanocrystalline and nanostructured metals, and conditions that lead to low friction coefficients. Grain boundary sliding and the breakdown of Hall–Petch strengthening at the shearing interface are found to generally and predictably explain the low friction of these materials. While the following is meant to serve as a general discussion of the strength of metals in the context of tribological applications, one important conclusion is that tribological research methods also provide opportunities for probing the fundamental properties and deformation mechanisms of metals.

scholarly journals MOSAIK and FMI-Based Co-Simulation Applied to Transient Stability Analysis of Grid-Forming Converter Modulated Wind Power Plants

2021 ◽  
Vol 11 (5) ◽  
pp. 2410
Author(s):  
Nakisa Farrokhseresht ◽  
Arjen A. van der Meer ◽  
José Rueda Torres ◽  
Mart A. M. M. van der Meijden
Keyword(s):  
Power System ◽  
Time Domain ◽  
Power Plants ◽  
Transient Stability ◽  
Renewable Energy Sources ◽  
Critical Factor ◽  
Primary Control ◽  
Simulation Approach ◽  
Wide Range ◽  
Grid Side

The grid integration of renewable energy sources interfaced through power electronic converters is undergoing a significant acceleration to meet environmental and political targets. The rapid deployment of converters brings new challenges in ensuring robustness, transient stability, among others. In order to enhance transient stability, transmission system operators established network grid code requirements for converter-based generators to support the primary control task during faults. A critical factor in terms of implementing grid codes is the control strategy of the grid-side converters. Grid-forming converters are a promising solution which could perform properly in a weak-grid condition as well as in an islanded operation. In order to ensure grid code compliance, a wide range of transient stability studies is required. Time-domain simulations are common practice for that purpose. However, performing traditional monolithic time domain simulations (single solver, single domain) on a converter-dominated power system is a very complex and computationally intensive task. In this paper, a co-simulation approach using the mosaik framework is applied on a power system with grid-forming converters. A validation workflow is proposed to verify the co-simulation framework. The results of comprehensive simulation studies show a proof of concept for the applicability of this co-simulation approach to evaluate the transient stability of a dominant grid-forming converter-based power system.

scholarly journals Study on Friction in Automotive Shock Absorbers Part 1: Friction Simulation Using a Dynamic Friction Model in the Contact Zone of an FEM Model

Vehicles ◽  
2021 ◽  
Vol 3 (2) ◽  
pp. 212-232
Author(s):  
Ludwig Herzog ◽  
Klaus Augsburg
Keyword(s):  
Ride Comfort ◽  
Viscous Friction ◽  
Simulation Method ◽  
Friction Model ◽  
Model Parameters ◽  
Dynamic Friction ◽  
Friction Modeling ◽  
Shock Absorbers ◽  
Operation Conditions ◽  
Wide Range

The important change in the transition from partial to high automation is that a vehicle can drive autonomously, without active human involvement. This fact increases the current requirements regarding ride comfort and dictates new challenges for automotive shock absorbers. There exist two common types of automotive shock absorber with two friction types: The intended viscous friction dissipates the chassis vibrations, while the unwanted solid body friction is generated by the rubbing of the damper’s seals and guides during actuation. The latter so-called static friction impairs ride comfort and demands appropriate friction modeling for the control of adaptive or active suspension systems. In this article, a simulation approach is introduced to model damper friction based on the most friction-relevant parameters. Since damper friction is highly dependent on geometry, which can vary widely, three-dimensional (3D) structural FEM is used to determine the deformations of the damper parts resulting from mounting and varying operation conditions. In the respective contact zones, a dynamic friction model is applied and parameterized based on the single friction point measurements. Subsequent to the parameterization of the overall friction model with geometry data, operation conditions, material properties and friction model parameters, single friction point simulations are performed, analyzed and validated against single friction point measurements. It is shown that this simulation method allows for friction prediction with high accuracy. Consequently, its application enables a wide range of parameters relevant to damper friction to be investigated with significantly increased development efficiency.

The chemistry of stabilized clusters

1982 ◽  
Vol 308 (1501) ◽  
pp. 27-34 ◽  
Keyword(s):  
Electron Donor ◽  
Organic Molecules ◽  
Metal Cluster ◽  
Organic Substrates ◽  
Insertion Reactions ◽  
Donor Ligand ◽  
Small Organic Molecules ◽  
Wide Range ◽  
Metal Metal ◽  
High Yields

Studies of the chemistry of metal cluster complexes and, in particular, their reactions with small organic molecules, have been confined to relatively few systems. Among the reasons for this are: (i) not many clusters are easily synthesized in high yields; (ii) their reactions often give a multitude of products that are difficult to separate and characterize; (iii) the conditions required to bring about reactions often lead to fragmentation of the cluster into lower nuclearity (often mononuclear) species. One cluster whose chemistry has been extensively studied is [Os 3 H 2 (CO) 10 ]. This can be synthesized in high yields from [Os 3 (CO) 12 ] + H 2 (Knox et al. 1975) and reacts readily under mild conditions with a wide range of electron-donor molecules by virtue of its coordinative unsaturation (Shapley et al. 1975; Deeming & Hasso 1976; Adams & Golembeski 1979). Formally, one may consider that a metal—metal double bond is present, which is reduced to a single bond on coordination of an additional two-electron donor ligand such as an organophosphine. The presence of metal—hydrogen bonds in this cluster and the cluster’s ability to coordinate organic substrates enable it to undergo a wide variety of insertion reactions, leading to products that may be regarded as intermediates in the reduction of organic molecules by clusters (Deeming & Hasso 1975; Keister & Shapley 1975).

scholarly journals Holistic Approach to Design, Test, and Optimize Stand-Alone SOFC-Reformer Systems

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 348
Author(s):  
Michael Höber ◽  
Benjamin Königshofer ◽  
Philipp Wachter ◽  
Gjorgji Nusev ◽  
Pavle Boskoski ◽  
...  
Keyword(s):  
Rural Communities ◽  
High Efficiency ◽  
Diffusion Processes ◽  
Holistic Approach ◽  
Maximum Error ◽  
Gas Diffusion ◽  
Electrochemical Analysis ◽  
Internal Reforming ◽  
Operation Conditions ◽  
Wide Range

Reliable electrical and thermal energy supplies are basic requirements for modern societies and their food supply. Stand-alone stationary power generators based on solid oxide fuel cells (SOFC) represent an attractive solution to the problems of providing the energy required in both rural communities and in rurally-based industries such as those of the agricultural industry. The great advantages of SOFC-based systems are high efficiency and high fuel flexibility. A wide range of commercially available fuels can be used with no or low-effort pre-treatment. In this study, a design process for stand-alone system consisting of a reformer unit and an SOFC-based power generator is presented and tested. An adequate agreement between the measured and simulated values for the gas compositions after a reformer unit is observed with a maximum error of 3 vol% (volume percent). Theoretical degradation free operation conditions determined by employing equilibrium calculations are identified to be steam to carbon ratio (H2O/C) higher 0.6 for auto-thermal reformation and H2O/C higher 1 for internal reforming. The produced gas mixtures are used to fuel large planar electrolyte supported cells (ESC). Current densities up to 500 mA/cm2 at 0.75 V are reached under internal reforming conditions without degradation of the cells anode during the more than 500 h long-term test run. More detailed electrochemical analysis of SOFCs fed with different fuel mixtures showed that major losses are caused by gas diffusion processes.

scholarly journals Development of a condition monitoring system for the refractory lining of induction crucible steelmaking furnaces

Vestnik IGEU ◽  
2019 ◽  
pp. 58-66
Author(s):  
I.Yu. Dolgikh ◽  
M.G. Markov
Keyword(s):  
Monitoring System ◽  
Refractory Lining ◽  
Control Object ◽  
Practical Implementation ◽  
Microprocessor System ◽  
Induction Melting ◽  
Monitoring And Control ◽  
Operation Conditions ◽  
Emergency Shutdown ◽  
Wide Range

A wide range of technological advantages of induction crucible melting furnaces makes their use in various sectors of metallurgical production relevant. However, hard operation conditions of the refractory lining of such furnaces makes it necessary to constantly monitor its condition, with the aim to extend the crucible life and prevent emergencies. Moreover, traditional methods based on the use of a bottom electrode and indication of current leakage to earth do not provide a continuous display of the lining destruction degree and make it possible to register only a critical level that requires an emergency shutdown and emptying of the furnace. This circumstance makes it necessary to develop and implement specialized electrical systems with a monitoring and control system that ensures the determination and visualization of the lining wear level and, if necessary, makes an emergency shutdown of the equipment from the power source. The developed complex is based on a microprocessor system that continuously measures the temperature at the control points at the boundary between the bottom and crucible base layers and compares the obtained values with the settings, which are determined previously on a two-dimensional axisymmetric model of the designed furnace by solving the stationary heat conduction equation at various levels of lining failure. We have developed the structure, scheme, and program for a microprocessor-based monitoring and emergency shutdown system of an induction furnace, as well as a mathematical model of the control object, which allows determining the temperature settings. The reliability of the results is confirmed by the applicability of the models to real objects, and is verified by debugging the microprocessor part in the MPLab-Sim and Proteus programs. The obtained results can be used in the practical implementation of the monitoring system and emergency shutdown of induction melting furnaces, which allows increasing the safety of their operation and extending the lining life due to timely repair.

scholarly journals Development of a New Stoichiometric Equilibrium-Based Model for Wood Chips and Mixed Paper Wastes Gasification by ASPEN Plus

2019 ◽  
Author(s):  
Sahar Safarianbana ◽  
Runar Unnthorsson ◽  
Christiaan Richter
Keyword(s):  
Moisture Content ◽  
Aspen Plus ◽  
Wood Chips ◽  
Thermochemical Conversion ◽  
Waste Biomass ◽  
Operation Conditions ◽  
High Heating Value ◽  
Cold Gas Efficiency ◽  
Wide Range ◽  
Steady State Simulation

Abstract Wood and paper residues are usually processed as wastes, but they can also be used to produce electrical and thermal energy through processes of thermochemical conversion of gasification. This study proposes a new steady state simulation model for down draft waste biomass gasification developed using the commercial software Aspen Plus for optimization of the gasifier performance. The model was validated by comparison with experimental data obtained from six different operation conditions. This model is used for analysis of gasification performance of wood chips and mixed paper wastes. The operating parameters of temperature and moisture content (MC) have been varied over wide range and their effect on the high heating value (HHV) of syngas and cold gas efficiency (CGE) were investigated. The results show that increasing the temperature improves the gasifier performance and it increases the production of CO and H2 which leads to higher LHV and CGE. However, an increase in moisture content reduces gasifier performance and results in low CGE.

scholarly journals Heat Treatment of Steel 1.1730 with Concentrated Solar Energy

2019 ◽  
Vol 56 (1) ◽  
pp. 261-270
Author(s):  
Maria Stoicanescu ◽  
Aurel Crisan ◽  
Ioan Milosan ◽  
Mihai Alin Pop ◽  
Jose Rodriguez Garcia ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Solar Radiation ◽  
Solar Energy ◽  
Vertical Axis ◽  
Solar Furnace ◽  
Solid Base ◽  
Heating And Cooling ◽  
Concentrated Solar Energy ◽  
Wide Range ◽  
The Impact

This paper presents and discusses research conducted with the purpose of developing the use of solar energy in the heat treatment of steels. For this, a vertical axis solar furnace called at Plataforma Solar de Almeria was adapted such as to allow control of the heating and cooling processes of samples made from 1.1730 steel. Thus temperature variation in pre-set points of the heated samples could be monitored in correlation with the working parameters: the level of solar radiation and implicitly the energy used the conditions of sample exposed to solar radiation, and the various protections and cooling mediums.The recorded data allowed establishing the types of treatments applied for certain working conditions. The distribution of hardness, as the representative feature resulting from heat treatment, was analysed on all sides of the treated samples. In correlation with the time-temperature-transformation diagram of 1.1730 steel, the measured values confirmed the possibility of using solar energy in all types of heat treatment applied to this steel. In parallel the efficiency of using solar energy was analysed in comparison to the energy obtained by burning methane gas for the heat treatment for the same set of samples. The analysis considered energy consumption, productivity and the impact on the environment. Thanks to various data obtained through developed experiences, which cover a wide range of thermic treatments applied steels 1.1730 model, we can certainly state that this can be a solid base in using solar energy in applications of thermic treatment at a high industrial level.

scholarly journals Prediction of Co and Ru Nanocluster Morphology on 2D MoS2 from Interaction Energies

2021 ◽  
Author(s):  
Cara-Lena Nies ◽  
Michael Nolan
Keyword(s):  
Thin Film ◽  
Density Functional ◽  
Bulk Material ◽  
Single Layer ◽  
Metal Substrate ◽  
Single Atom ◽  
Metal Interaction ◽  
Wide Range ◽  
Metal Metal ◽  
Sulphur Vacancy

Layered materials, such as \ce{MoS2}, have a wide range of potential applications due to the properties of a single layer which often differ from the bulk material. They are of particular interest as ultra-thin diffusion barriers in semi-conductor device interconnects and as supports for low dimensional metal catalysts. Understanding the interaction between metals and the \ce{MoS2} monolayer is of great importance when selecting systems for specific applications. In previous studies the focus has been largely on the strength of the interaction between a single atom or a nanoparticle of a range of metals, which has created a significant knowledge gap in understanding thin film nucleation on 2D materials. In this paper, we present a density functional theory (DFT) study of the adsorption of small Co and Ru structures, with up to four atoms, on a monolayer of \ce{MoS2}. We explore how the metal-substrate and metal-metal interactions contribute to the stability of metal clusters on \ce{MoS2}, and how these interactions change in the presence of a sulphur vacancy, to develop insight to allow prediction of thin film morphology. The strength of interaction between the metals and \ce{MoS2} is in the order Co > Ru. The competition between metal-substrate and metal-metal interaction allows us to conclude that 2D structures should be preferred for Co on \ce{MoS2}, while Ru prefers 3D structures on \ce{MoS2}. However, the presence of a sulphur vacancy decreases the metal-metal interaction, indicating that with controlled surface modification 2D Ru structures could be achieved. Based on this understanding, we propose Co on \ce{MoS2} as a suitable candidate for advanced interconnects, while Ru on \ce{MoS2} is more suited to catalysis applications.

scholarly journals A Novel Method for Tuning PID Controller

2013 ◽  
Vol 6 (1) ◽  
pp. 62-74
Author(s):  
Abidaoun H. shallal ◽  
Rawaa A. Karim ◽  
Osama Y. Al-Rawi
Keyword(s):  
Computer Technology ◽  
Pid Control ◽  
Pid Controller ◽  
Control Algorithm ◽  
The Novel ◽  
Operation Conditions ◽  
Wide Range ◽  
Novel Method ◽  
Mechanical Performances ◽  
Dc Servomotor

Proportional integral derivative (PID) control is the most commonly used  control algorithm in the industry today. PID controller popularity can be attributed to the  controller’s effectiveness in a wide range of operation conditions, its functional simplicity, and the ease with which engineers can implement it using current computer technology . In this paper,the Dc servomotor model is chosen according to his good electrical and mechanical performances more than other Dc motor models , discuss the novel method for  tuning PID controller and comparison with Ziegler - Nichols method from through parameters of transient response of any system which uses PID compensator

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