Lubrication Properties of Biodiesel: Experimental Investigation and Molecular Dynamics Simulations

2013 ◽  
Vol 316-317 ◽  
pp. 1075-1079 ◽  
Author(s):  
Hui Luo ◽  
Wei Yu Fan ◽  
Yang Li ◽  
Guo Zhi Nan
Keyword(s):  
Molecular Dynamics ◽  
Diesel Fuel ◽  
Cohesive Energy ◽  
Ethyl Oleate ◽  
Md Simulations ◽  
Ethyl Linoleate ◽  
Carbon Chain ◽  
Ethyl Stearate ◽  
Lubrication Performance ◽  
Low Sulfur

In this work, biodiesels, such as such as ethyl stearate, ethyl oleate, ethyl linoleate, ethyl ricinoleate, were adopted as lubricity additives for low-sulfur diesel fuel, at the concentration range of 0.1~2 wt%. Tribological evaluation obtained from the High-Frequency Reciprocating Rig (HFRR) showed that double bonds or hydroxyl introduced in the carbon chain of the esters could lead to a higher lubrication performance. The lubricity efficiency order was explained by the molecular dynamics (MD) simulations. The lubricity enhancing properties of the esters are mainly determined by the cohesive energy of adsorbed films formed on iron surface. The greater the cohesive energy, the more efficiently it is that the esters enhance the lubricity of low-sulfur diesel fuel.

scholarly journals Investigating the Compatibility of Various Components in Marine Low-Sulfur Fuel Oil by Molecular Dynamics Simulations

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Daping Zhou ◽  
Haijun Wei ◽  
Shuye Xue ◽  
Ye Qiu ◽  
Shen Wu ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Distribution Function ◽  
Radial Distribution Function ◽  
Radial Distribution ◽  
Md Simulations ◽  
Peak Height ◽  
Fuel Oil ◽  
Solubility Parameters ◽  
Heavy Fuel Oil ◽  
Low Sulfur

Asphaltene aggregation and precipitation are one of the major issues for marine low-sulfur fuel oil used on board. Many research studies have been carried out to investigate the aggregation behavior of asphaltene under different conditions, but the mechanism of asphaltene aggregation in low-sulfur fuel oil at the molecular level is still unclear. In this work, molecular dynamics (MD) simulations were performed to calculate the solubility parameters, intermolecular interaction energies, and radial distribution function (RDF) curves of each component in marine low-sulfur fuel oil to examine their mutual compatibility. Simulation results indicate that the solubility parameter of resin gains the highest value and it is close to asphaltene. The solubility parameters of aromatic, hexadecane, and saturate decrease successively. The interaction energy between resin and asphaltene molecules is higher than that between the same kind of molecules, which means that resin can inhibit the aggregation of asphaltene molecules. Typically, a light distillate component (hexadecane) is added to heavy fuel oil to yield low-sulfur oil, and our calculations reveal that this has a negative effect on asphaltene aggregation. Specifically, asphaltene is more likely to self-aggregate, as shown by the increase in peak height in the radial distribution function of the asphaltene-asphaltene pair. The findings of this study will provide theoretical support for the production of marine low-sulfur fuel.

Lubricity assessment of ultra-low sulfur diesel fuel (ULSD), biodiesel, and their blends, in conjunction with pure hydrocarbons and biodiesel based compounds

2021 ◽  
pp. 146808742098407
Author(s):  
Mustafa Ertunc Tat ◽  
Osman Nuri Çelik ◽  
Umit Er ◽  
Hakan Gasan ◽  
Mustafa Ulutan
Keyword(s):  
Wear Rate ◽  
Chain Length ◽  
Vegetable Oils ◽  
Diesel Fuel ◽  
Carbon Chain ◽  
Carbon Chain Length ◽  
Wear Properties ◽  
Wear Rates ◽  
Ultra Low Sulfur Diesel ◽  
Low Sulfur

This research aimed to investigate the lubricity and wear properties of ultra-low sulfur diesel fuel (ULSD) blended with biodiesel and doped with biodiesel-based organic compounds. In this work, neat n-dodecane served as a surrogate for ultra-low sulfur diesel fuel (ULSD), Fischer Tropsch, and renewable diesel fuels. Additionally, some pure hydrocarbons were also investigated for unsaturation and carbon chain length. Tribological characterization was conducted on quenched and tempered AISI 4140 steel, substituting diesel fuel pump material, and using the ball-on-disc technique. The wear rates of biodiesel samples were about 2–4 times less than the vegetable oils. Esterification improves the lubricity of vegetable oils. The wear rate of biodiesel is about 5–7 times greater than that of fossil base commercial Eurodiesel fuel. Using biodiesel as an additive had a significant effect on the lubricity of pure n-dodecane, adding 2 wt% biodiesel resulted in 5–7 times wear rate reduction that equivalent to the lubricity level of commercial Eurodiesel fuel. Wear rates of pure hydrocarbons showed that wear is reduced with increasing chain length and unsaturation.

A molecular dynamics study: Structures and thermal stability of PdmPt(13−m)Ag42 ternary nanoalloys

2018 ◽  
Vol 29 (09) ◽  
pp. 1850084 ◽  
Author(s):  
Ali Kemal Garip
Keyword(s):  
Molecular Dynamics ◽  
Cohesive Energy ◽  
Canonical Ensemble ◽  
Interatomic Interaction ◽  
Md Simulations ◽  
Many Body ◽  
Melting Temperatures ◽  
Body Potential ◽  
Basin Hopping ◽  
Thermal Stability Of

Structural optimization of ternary PdmPt[Formula: see text]Ag[Formula: see text] nanoalloys was performed using the basin-hopping algorithm, and the Gupta many-body potential was adopted to model interatomic interaction. The optimization results show that all compositions have a structure based on icosahedron with a core–shell segregation. While the Ag atoms prefer to segregate to the surface, Pd and Pt atoms were located at the core of the cluster due to the higher surface and cohesive energy. The single platinum atom with the highest cohesive energy in Pd[Formula: see text]Pt1Ag[Formula: see text] nanoalloy was located at the center of the cluster. Also in all other compositions except Pd[Formula: see text]Ag[Formula: see text], Pd atoms occupy the second shell position of the icosahedron structure. We used classical molecular dynamics (MD) simulations in canonical ensemble conditions (NVT) to investigate the melting temperatures of ternary PdmPt[Formula: see text]Ag[Formula: see text] nanoalloys with the interatomic interactions modeled by the same potential with optimizations. The icosahedral structures were taken as the initial configurations for MD simulations. We obtained caloric curves and Lindemann indexes to investigate the melting transitions. The simulation results showed that varying the composition gives rise to a fluctuation in melting temperatures. The highest melting temperature belongs to the Pd9Pt4Ag[Formula: see text] nanoalloy cluster within the other compositions. However, the relative stability investigation indicates the Pd8Pt5Ag[Formula: see text] nanoalloy cluster as the most stable composition. The Lindemann indexes obtained for the second and third shell of icosahedral structures show that the melting takes place as a whole without any surface premelting.

scholarly journals Anti-Diabetic Activity and Nuclear Magnetic Resonance (NMR) Characterization of Natural Esters from Hexane and Dichloromethane Crude Extracts from Calyces of Hibiscus sabdariffa Linn

2019 ◽  
Vol 8 (2S7) ◽  
pp. 102-105
Keyword(s):  
Inhibitory Activity ◽  
Ethyl Oleate ◽  
2D Nmr ◽  
Ethyl Linoleate ◽  
Hibiscus Sabdariffa ◽  
Ethyl Stearate ◽  
Phytochemical Study ◽  
Crude Extracts ◽  
Nmr Characterization ◽  
Solid Liquid

Non-polar crude extracts obtained from the calyces of Hibiscus sabdariffa Linn. (Roselle) and their α-glucosidase inhibitory activity has been investigated. Roselle extracts potentially act as an anti-diabetic activity. However, most of the previous studies on Roselle were just focused on the polar crude extracts. Therefore, hexane and dichloromethane crude extracts were selected for these study. 3 kg of samples were air dried at room temperature, ground and serially extracted by solid-liquid extraction technique using hexane and dichloromethane. Compounds were isolated and purified by various chromatographic techniques. Their structures were elucidated with 1D and 2D-NMR, and other spectroscopic methods including MS, IR and UV as well as comparison with data reported in the literature. The phytochemical study has led to the isolation of three compounds namely squalene, triglyceride fatty acids (consist of ethyl oleate, ethyl linoleate and γ-ethyl linolenate) and ethyl stearate. Based on the literature, this is the first reported squalene isolated from the calyces of Roselle. The α-glucosidase inhibitory activity on the crude extracts was conducted and showed moderate inhibitory activity was detected on hexane crude extract. Thus, results from this study can be used as future references for the discovery of natural esters and the potential of Roselle as an anti-diabetic source.

Efficient Treatment of Fixed and Induced Dipolar Interactions

2000 ◽  
Vol 653 ◽  
Author(s):  
Celeste Sagui ◽  
Thoma Darden
Keyword(s):  
Molecular Dynamics ◽  
Md Simulations ◽  
Lagrangian Formalism ◽  
Dipolar Interactions ◽  
Time Step ◽  
Efficient Treatment ◽  
Particle Mesh Ewald ◽  
Fixed Charges ◽  
Self Consistency ◽  
Induced Dipoles

AbstractFixed and induced point dipoles have been implemented in the Ewald and Particle-Mesh Ewald (PME) formalisms. During molecular dynamics (MD) the induced dipoles can be propagated along with the atomic positions either by interation to self-consistency at each time step, or by a Car-Parrinello (CP) technique using an extended Lagrangian formalism. The use of PME for electrostatics of fixed charges and induced dipoles together with a CP treatment of dipole propagation in MD simulations leads to a cost overhead of only 33% above that of MD simulations using standard PME with fixed charges, allowing the study of polarizability in largemacromolecular systems.

Split the Charge Difference in Two! a Rule of Thumb for Adding Proper Amounts of Ions in MD Simulations

2020 ◽  
Author(s):  
Matías R. Machado ◽  
Sergio Pantano
Keyword(s):  
Molecular Dynamics ◽  
Ionic Strength ◽  
Molecular Simulations ◽  
Md Simulations ◽  
Good Practices ◽  
Rule Of Thumb ◽  
Ionic Concentrations

<p> Despite the relevance of properly setting ionic concentrations in Molecular Dynamics (MD) simulations, methods or practical rules to set ionic strength are scarce and rarely documented. Based on a recently proposed thermodynamics method we provide an accurate rule of thumb to define the electrolytic content in simulation boxes. Extending the use of good practices in setting up MD systems is promptly needed to ensure reproducibility and consistency in molecular simulations.</p>

Assessing the Antimalarial Potentials of Phytochemicals: Virtual Screening, Molecular Dynamics and In-Vitro Investigations

2019 ◽  
Vol 16 (3) ◽  
pp. 291-300
Author(s):  
Saumya K. Patel ◽  
Mohd Athar ◽  
Prakash C. Jha ◽  
Vijay M. Khedkar ◽  
Yogesh Jasrai ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Structural Integrity ◽  
Md Simulations ◽  
Tylophora Indica ◽  
Multidrug Resistance Protein 1 ◽  
Receptor Complexes ◽  
Resistance Protein ◽  
Dynamics Simulations ◽  
Stable Trajectory

Background: Combined in-silico and in-vitro approaches were adopted to investigate the antiplasmodial activity of Catharanthus roseus and Tylophora indica plant extracts as well as their isolated components (vinblastine, vincristine and tylophorine). </P><P> Methods: We employed molecular docking to prioritize phytochemicals from a library of 26 compounds against Plasmodium falciparum multidrug-resistance protein 1 (PfMDR1). Furthermore, Molecular Dynamics (MD) simulations were performed for a duration of 10 ns to estimate the dynamical structural integrity of ligand-receptor complexes. </P><P> Results: The retrieved bioactive compounds viz. tylophorine, vinblastin and vincristine were found to exhibit significant interacting behaviour; as validated by in-vitro studies on chloroquine sensitive (3D7) as well as chloroquine resistant (RKL9) strain. Moreover, they also displayed stable trajectory (RMSD, RMSF) and molecular properties with consistent interaction profile in molecular dynamics simulations. </P><P> Conclusion: We anticipate that the retrieved phytochemicals can serve as the potential hits and presented findings would be helpful for the designing of malarial therapeutics.

scholarly journals On the Use of the Discrete Constant pH Molecular Dynamics to Describe the Conformational Space of Peptides

Polymers ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 99
Author(s):  
Cristian Privat ◽  
Sergio Madurga ◽  
Francesc Mas ◽  
Jaime Rubio-Martínez
Keyword(s):  
Molecular Dynamics ◽  
Amino Acids ◽  
Md Simulations ◽  
Point Of View ◽  
Conformational Space ◽  
Conformational Sampling ◽  
Protonation State ◽  
Constant Ph ◽  
Biochemical Systems ◽  
Constant Ph Molecular Dynamics

Solvent pH is an important property that defines the protonation state of the amino acids and, therefore, modulates the interactions and the conformational space of the biochemical systems. Generally, this thermodynamic variable is poorly considered in Molecular Dynamics (MD) simulations. Fortunately, this lack has been overcome by means of the Constant pH Molecular Dynamics (CPHMD) methods in the recent decades. Several studies have reported promising results from these approaches that include pH in simulations but focus on the prediction of the effective pKa of the amino acids. In this work, we want to shed some light on the CPHMD method and its implementation in the AMBER suitcase from a conformational point of view. To achieve this goal, we performed CPHMD and conventional MD (CMD) simulations of six protonatable amino acids in a blocked tripeptide structure to compare the conformational sampling and energy distributions of both methods. The results reveal strengths and weaknesses of the CPHMD method in the implementation of AMBER18 version. The change of the protonation state according to the chemical environment is presumably an improvement in the accuracy of the simulations. However, the simulations of the deprotonated forms are not consistent, which is related to an inaccurate assignment of the partial charges of the backbone atoms in the CPHMD residues. Therefore, we recommend the CPHMD methods of AMBER program but pointing out the need to compare structural properties with experimental data to bring reliability to the conformational sampling of the simulations.

scholarly journals Unveiling Carbon Dioxide and Ethanol Diffusion in Carbonated Water-Ethanol Mixtures by Molecular Dynamics Simulations

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1711
Author(s):  
Mohamed Ahmed Khaireh ◽  
Marie Angot ◽  
Clara Cilindre ◽  
Gérard Liger-Belair ◽  
David A. Bonhommeau
Keyword(s):  
Carbon Dioxide ◽  
Molecular Dynamics ◽  
Diffusion Coefficients ◽  
Hydrodynamic Radius ◽  
Md Simulations ◽  
Molecular Models ◽  
Experimental Values ◽  
Carbon Dioxide Co2 ◽  
Dynamics Simulations ◽  
Apparent Disagreement

The diffusion of carbon dioxide (CO2) and ethanol (EtOH) is a fundamental transport process behind the formation and growth of CO2 bubbles in sparkling beverages and the release of organoleptic compounds at the liquid free surface. In the present study, CO2 and EtOH diffusion coefficients are computed from molecular dynamics (MD) simulations and compared with experimental values derived from the Stokes-Einstein (SE) relation on the basis of viscometry experiments and hydrodynamic radii deduced from former nuclear magnetic resonance (NMR) measurements. These diffusion coefficients steadily increase with temperature and decrease as the concentration of ethanol rises. The agreement between theory and experiment is suitable for CO2. Theoretical EtOH diffusion coefficients tend to overestimate slightly experimental values, although the agreement can be improved by changing the hydrodynamic radius used to evaluate experimental diffusion coefficients. This apparent disagreement should not rely on limitations of the MD simulations nor on the approximations made to evaluate theoretical diffusion coefficients. Improvement of the molecular models, as well as additional NMR measurements on sparkling beverages at several temperatures and ethanol concentrations, would help solve this issue.

Mechanism of stacking fault annihilation in 3C-SiC epitaxially grown on Si(001) by molecular dynamics simulations

CrystEngComm ◽  
2021 ◽  
Author(s):  
Andrey Sarikov ◽  
Anna Marzegalli ◽  
Luca Barbisan ◽  
Massimo Zimbone ◽  
Corrado Bongiorno ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Stacking Faults ◽  
Md Simulations ◽  
Stacking Fault ◽  
Dynamics Simulations

In this work, annihilation mechanism of stacking faults (SFs) in epitaxial 3C-SiC layers grown on Si(001) substrates is studied by molecular dynamics (MD) simulations. The evolution of SFs located in...

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