Fluid Effects on Mechanical Efficiency of Hydraulic Pumps: Dynamometer Measurements and Molecular Simulations

2019 ◽  
Author(s):  
Pawan Panwar ◽  
Michelle Len ◽  
Ninaad Gajghate ◽  
Paul Michael ◽  
Ashlie Martini
Keyword(s):  
Mechanical Efficiency ◽  
Solution Viscosity ◽  
Fluid Viscosity ◽  
Hydraulic Systems ◽  
Specific Viscosity ◽  
Base Oil ◽  
Base Oils ◽  
Lower Viscosity ◽  
Viscosity Modifiers ◽  
Dynamics Simulations

Abstract The mechanical efficiency of hydraulic pumps is affected by the viscosity of the hydraulic fluid. Viscosity modifiers that thicken the fluid, therefore, play an important role in efficiency. Viscosity modifiers are believed to improve the mechanical efficiency of hydraulic systems partially by enabling formulation with lower molecular weight base oils. Here, this concept was directly tested in a pump dynamometer using mixtures of low traction synthetic poly(alphaolefin) base oils, bis(2-ethylhexyl) adipate ester, and poly(isobutylene). Lower viscosity fluids directly correlated to better mechanical efficiency but decreasing the viscosity of the synthetic base oil by adding viscosity modifier did not have the same effect. However, molecular dynamics simulations showed that solution viscosity was directly correlated to elongation of the polymer under shear which, together with calculations of the critical shear rate range in a pump, suggested ways of designing viscosity modifiers to achieve a specific viscosity profile that maximizes mechanical efficiency.

scholarly journals Critical Shear Rate of Polymer-Enhanced Hydraulic Fluids

Lubricants ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 102
Author(s):  
Pawan Panwar ◽  
Paul Michael ◽  
Mark Devlin ◽  
Ashlie Martini
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Shear Thinning ◽  
Hydraulic Systems ◽  
Newtonian Viscosity ◽  
Critical Shear Rate ◽  
Base Oil ◽  
Hydraulic Fluids ◽  
Theoretical Predictions ◽  
Dynamics Simulations

Many application-relevant fluids exhibit shear thinning, where viscosity decreases with shear rate above some critical shear rate. For hydraulic fluids formulated with polymeric additives, the critical shear rate is a function of the molecular weight and concentration of the polymers. Here we present a model for predicting the critical shear rate and Newtonian viscosity of fluids, with the goal of identifying a fluid that shear thins in a specific range relevant to hydraulic pumps. The model is applied to predict the properties of fluids comprising polyisobutene polymer and polyalphaolefin base oil. The theoretical predictions are validated by comparison to viscosities obtained from experimental measurements and molecular dynamics simulations across many decades of shear rates. Results demonstrate that the molecular weight of the polymer plays a key role in determining the critical shear rate, whereas the concentration of polymer primarily affects the Newtonian viscosity. The simulations are further used to show the molecular origins of shear thinning and critical shear rate. The atomistic simulations and simple model developed in this work can ultimately be used to formulate polymer-enhanced fluids with ideal shear thinning profiles that maximize the efficiency of hydraulic systems.

Kinetic Study of the Thermo-Oxidative Degradation of Squalane (C30H62) Modelling the Base Oil of Engine Lubricants

2009 ◽  
Author(s):  
Moussa Diaby ◽  
Michel Sablier ◽  
Anthony Le Negrate ◽  
Mehdi El Fassi
Keyword(s):  
Oxidative Degradation ◽  
Engine Oil ◽  
Ongoing Research ◽  
Base Oil ◽  
Rate Law ◽  
Tert Butyl ◽  
Oxidation Rates ◽  
Base Oils ◽  
Wide Range ◽  
Thermo Oxidative Degradation

On the basis of ongoing research conducted on the clarification of processes responsible for lubricant degradation in the environment of piston grooves in EGR diesel engines, an experimental investigation was aimed to develop a kinetic model which can be used for the prediction of lubricant oxidative degradation correlated to endurance test conducted on engines. Knowing that base oils are a complex blend of paraffins and naphtenes with a wide range of sizes and structures, their chemistry analysis during the oxidation process can be highly convoluted. In the present work, investigations were carried out with the squalane (C30H62) chosen for its physical and chemical similarities with the lubricant base oils used during the investigations. Thermo-oxidative degradation of this hydrocarbon was conducted at atmospheric pressure in a tubular furnace, while varying temperature and duration of the tests in order to establish an oxidation reaction rate law. The same experimental procedures was applied to squalane doped with two different phenolic antioxidants usually present in engine oil composition: 2,6-di-tert-butyl-4-methylphenol (BHT), and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (OBHP). Thus, the effect of both antioxidants on the oxidation rate law was investigated. Data analysis of the oxidized samples (FTIR spectroscopy, gas chromatography/mass spectrometry GC/MS) allowed to rationalize the thermo-oxidative degradation of squalane. The resulting kinetic modelling provides a practical analytical tool to follow the thermal degradation processes, which can be used for prediction of base oil hydrocarbon ageing. If experiments confirmed the role of phenolic additives as an affective agent to lower oxidation rates, the main results lay in the observation of a threshold temperature where a reversed activity of these additives was observed.

scholarly journals The Investigation of Viscometric Properties of the Most Reputable Types of Viscosity Index Improvers in Different Lubricant Base Oils: API Groups I, II, and III

Lubricants ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 6
Author(s):  
Seyed Ali Khalafvandi ◽  
Muhammad Ali Pazokian ◽  
Ehsan Fathollahi
Keyword(s):  
Viscosity Index ◽  
Behavioral Differences ◽  
Base Oil ◽  
Polymer Molecules ◽  
Base Oils ◽  
Two Temperatures ◽  
Higher Temperature ◽  
Viscosity Index Improvers ◽  
Lower Temperature ◽  
Definition Of

Four commercial viscosity index improvers (VII) have been used to investigate the behavioral differences of these compounds in three types of universally applicable base oils. The used VIIs are structurally three types of co-polymer: ethylene-propylene, star isoprene, and two di-block styrene-isoprene. After dissolving of different amounts of VIIs in different base oils, the kinematic viscosities at two standard temperatures were determined and the intrinsic viscosities were calculated according to Huggins method, then the effects of changes in base oil and polymer type were investigated. Intrinsic viscosities as criteria for polymer molecules sizes were found to be higher at lower temperature than at higher temperature. Dependence of intrinsic viscosity on the polymer molecular weight was observed. In the previous works, one or two types of VIIs were studied in only one type of base oil and/or solvent, not different base oils. Furthermore, different ranges of temperatures and concentrations not necessarily applied ranges were selected, but in this work, common base oils and most commercial VIIs were used and the viscometric properties were compared at two temperatures. Viscosities at these temperatures are used for determining VI and definition of lubricant’s viscosity grades. VI improvement is the main cause of VII usage.

scholarly journals Comparative Study on Mechanical Properties of Sealing Grease Composed of Different Base Oils for Shield Tunnel

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 692 ◽  
Author(s):  
Xiangqian Li ◽  
Yuyou Yang ◽  
Fan Li
Keyword(s):  
Mechanical Properties ◽  
Vegetable Oil ◽  
Exponential Function ◽  
Flow Rate ◽  
Temperature Sensitivity ◽  
Mineral Oil ◽  
Shield Tunnel ◽  
Fixed Temperature ◽  
Base Oil ◽  
Base Oils

This study proposes a novel sealing grease with improved mechanical properties and environmental performance. A series of sealing grease samples were made with different base oils, including mineral oil and renewable oil (vegetable oil and lard). In this study, thermogravimetric analysis (TGA) was conducted to study the adsorption capacity of the thickener to the base oil. The fluidity of the sealing grease was also tested at different temperatures. Furthermore, an exponential function was proposed for the flow rate of the sealing grease and the temperature. Moreover, a cone penetration test was conducted to study the consistency of the sealing grease. The results indicated that the capacity of the thickener to adsorb vegetable oil was greater than that of mineral oil, but less than that of lard. Additionally, the flow rate of the sealing grease increased with an increase in temperature. At a fixed temperature, the flow rate of the sealing grease increased with the base oil content. According to the exponential function, the composition of the base oil is the key factor that determines the temperature sensitivity of the sealing grease. In addition, the sealing grease made of vegetable oil has the minimum temperature sensitivity coefficient.

scholarly journals Tribological behavior of oils additised with a phosphonium-derived ionic liquid compared to a commercial oil

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Marlene Bartolomé Sáez ◽  
Antolin E. Hernández Battez ◽  
Jorge Espina Casado ◽  
José L. Viesca Rodríguez ◽  
Alfonso Fernández-González ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Peer Review ◽  
Formation Rate ◽  
Antiwear Additives ◽  
Stribeck Curve ◽  
Content Type ◽  
Base Oil ◽  
Base Oils ◽  
Antiwear Properties ◽  
Commercial Oil

Purpose The purpose of this paper is to study the antifriction, antiwear and tribolayer formation properties of the trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl) phosphinate ionic liquid (IL) as additive at 1 wt.% in two base oils and their mixtures, comparing the results with those of a commercial oil. Design/methodology/approach The mixture of the base oils used in the formulation of the commercial oil SAE 0W20 plus the IL was tested under rolling/sliding and reciprocating conditions to determine the so-called Stribeck curve, the tribolayer formation and the antifriction and antiwear behaviors. Findings The use of this IL as additive in these oils does not change their viscosity; improves the antifriction and antiwear properties of the base oils, making equal or outperforming these properties of the SAE 0W20; and the thickness and formation rate of the tribolayer resulting from the IL-surface interaction is highly dependent on the type of base oil and influence on the friction and wear results. Originality/value The use of this IL allows to replace partial or totally commercial antifriction and antiwear additives. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2020-0179/

Solvents for Synthetic Rubbers

1967 ◽  
Vol 40 (4) ◽  
pp. 1170-1182
Author(s):  
L. F. King
Keyword(s):  
Viscosity Solutions ◽  
Relative Viscosity ◽  
Solution Viscosity ◽  
Solvent Viscosity ◽  
Acrylonitrile Copolymer ◽  
General Correlation ◽  
Synthetic Rubber ◽  
Lower Viscosity ◽  
Rubber Cement ◽  
Solvent Volume

Abstract The effects of solvent characteristics on viscosities of several synthetic rubber hydrocarbon solutions was determined. Normal and isoparaffins (Ce and C7) yielded lower viscosity solutions than naphthenes and aromatics at 10 weight per cent of solvent and 8 grams of rubber per 100 cm3 of solvent, concentrations of interest to rubber cement and adhesive manufacturers. Solubility varied markedly with elastomer and solvent. Butadiene acrylonitrile copolymer and ethylene propylcnc tcrpolymer were the least soluble; cis-polyisoprene, butyl rubbers, and ethylene propylene copolymer were soluble in all thinners. No general correlation was found on a solvent volume basis between solution viscosity and solvent viscosity or between relative viscosity and hydrocarbon type.

Improving the Performance of Gas Engine Oils: A New Generation of Geo-Specific Additive Systems

2003 ◽  
Author(s):  
Laurent Chambard ◽  
John Smythe
Keyword(s):  
High Performance ◽  
Additive Technologies ◽  
Performance Limits ◽  
Base Oil ◽  
Gas Engine ◽  
Engine Oils ◽  
Base Oils ◽  
Beaten Track ◽  
Excellent Control ◽  
New Generation

Additive technologies able to successfully lubricate gas engines have been available for many years, but in recent years the acceleration of both commercial and technical demands placed on gas engine lubricants has highlighted the performance limits of traditional additive solutions. One of these limits is the ability to reach long and very long oil drains, required by an increasing number of operators. Since traditional additive chemistries on conventional base oil systems have reached their limits in that respect, focus has been increasingly placed on using higher performance base oils so that longer oil drains can be reached. However, traditional additive chemistries have often proved to struggle in these higher performance base oils, particularly in the aspect of deposit control — demonstrating that a new generation of additive systems for the formulation of gas engine oils is needed. The authors present one such generation of additive systems, developed around off-the-beaten-track detergent technology; providing superior control of oxidation and deposits. Such additive systems can be used either in conventional base oil systems with improved drain interval, or in high performance base oil systems with very long drain interval and excellent control of deposits. Besides the description of the chemistry involved, the authors also present a methodology of performance evaluation in the laboratory, and compare this methodology with the performance perceived in the field.

scholarly journals On the Crystallinity and Durability of ZDDP Tribofilm

2019 ◽  
Vol 67 (4) ◽  
Author(s):  
Mao Ueda ◽  
Amir Kadiric ◽  
Hugh Spikes
Keyword(s):  
Steel Substrate ◽  
Current Trend ◽  
Outer Region ◽  
Surface Damage ◽  
Amorphous Structure ◽  
Antiwear Additives ◽  
Metallic Surfaces ◽  
Base Oil ◽  
Low Concentrations ◽  
Lower Viscosity

Abstract The current trend for using lower-viscosity lubricants with the aim of improving fuel economy of mechanical systems means that machine components are required to operate for longer periods in thin oil film, mixed lubrication conditions, where the risk of surface damage is increased. Consequently, the performance and durability of the tribofilms formed by antiwear additives, and in particular zinc dialkyldithiophosphate (ZDDP), the main antiwear oil additive used in engine oils, has become an increasingly important issue. In this paper, it is confirmed that ZDDP tribofilms are initially relatively easily removed by rubbing but that they become more durable during prolonged rubbing. FIB-TEM analyses at different stages of tribofilm formation show that during the early stages of rubbing only the tribofilm close to the steel substrate is nanocrystalline, while the outer region is amorphous and easily removed. However, after prolonged rubbing all regions of the tribofilm become nanocrystalline and able to withstand rubbing in base oil without being removed. XPS analysis shows that after extended rubbing the outermost polyphosphate structures change from longer-chain structures such as metaphosphate and polyphosphate to shorter-chain structures including orthophosphate. This depolymerization of ZDDP tribofilm from long- to short-chain phosphate and consequent nanocrystallization are driven by heat and shear stress. EDX analysis shows that this conversion is promoted by diffusion of Fe cation into the bulk of the tribofilm. The finding that ZDDP tribofilms evolve during rubbing from a weaker amorphous structure to a more durable nanocrystalline one has important implications in terms of the behaviour of ZDDPs at low concentrations, on non-metallic surfaces and at very high contact pressures, as well as for the development of ZDDP tribofilm, friction and wear models.

High Temperature Tribological Behavior of Nano-Al2O3 in Different Base Oils

2008 ◽  
Vol 373-374 ◽  
pp. 568-571 ◽  
Author(s):  
X.F. Sun ◽  
Yu Lin Qiao ◽  
Jia Wu He ◽  
Shi Ning Ma ◽  
C.H. Hu
Keyword(s):  
High Temperature ◽  
Ball Bearing ◽  
Tribological Behavior ◽  
Test System ◽  
High Load ◽  
Friction Coefficients ◽  
Base Oil ◽  
Base Oils ◽  
Al2o3 Particles ◽  
Reducing Properties

High temperature tribological behavior of nano-Al2O3 in different base oils were tested by a SRV multifunctional test system. The results show that the nano-Al2O3 particles can obviously improve the antiwear and friction reducing properties of the base oil under high temperature and high load. The friction coefficients of the base oil with added nano-Al2O3 are reduced about 35%, and abrasion loss reduces about 60%. When temperature is 500°C and load is 500N the pure base oil has lost lubricative function, but the base oil with added nano-Al2O3 can still remain the lower friction coefficients. Tribological behavior should be similar to the “ball bearing” lubrication action of the nano-Al2O3 particles, so the movement between the two tribological pairs becomes sliding/rolling.

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