The High Pressure Rheology of Mixtures

2004 ◽  
Vol 126 (4) ◽  
pp. 697-702 ◽  
Author(s):  
Scott Bair
Keyword(s):  
Molecular Weight ◽  
High Pressure ◽  
Binary Systems ◽  
Viscosity Coefficient ◽  
Shear Thinning ◽  
Newtonian Viscosity ◽  
Double Shear ◽  
Ideal Mixing ◽  
Viscosity Behavior ◽  
Single Flow

The Newtonian mixing rules for several binary systems have been experimentally investigated. Some systems show non-ideal mixing response and for some systems the non-ideal response is pressure-dependent, yielding an opportunity for manipulation of the pressure-viscosity behavior to advantage. The mixing of differing molecular weight “straight cuts” can produce very different pressure-viscosity response. This behavior underscores the difficulty in predicting the pressure-viscosity coefficient based upon chemical structure and ambient viscosity since the molecular weight distribution is also important, but it also provides another opportunity to control the high-pressure response by blending. The first experimental observation of double shear-thinning within a single flow curve is reported. Blending then provides the capability of adjusting not only the Newtonian viscosity but also the non-Newtonian shear-thinning response as well.

New Central Film Thickness Equation for Shear Thinning Lubricants in Elastohydrodynamic Lubricated Rolling/Sliding Point Contact Conditions

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Puneet Katyal ◽  
Punit Kumar
Keyword(s):  
High Pressure ◽  
Equation Of State ◽  
Film Thickness ◽  
Point Contact ◽  
Viscosity Coefficient ◽  
Shear Thinning ◽  
Numerical Approach ◽  
Present Formulation ◽  
Contact Conditions ◽  
Doolittle Equation

This paper offers central film thickness formula pertaining to shear-thinning lubricants under rolling/sliding point contact conditions. The shear-thinning behavior of the lubricants is modeled using Carreau viscosity equation and the piezo-viscous response employed herein is the free-volume based Doolittle equation in conjunction with Tait's equation of state for lubricant compressibility. The present formulation is based on reciprocal asymptotic isoviscous piezo-viscous coefficient as it is a more accurate measure of the high pressure piezo-viscous response of elastohydrodynamic lubricated (EHL) lubricants compared to the conventional pressure–viscosity coefficient. Comparisons between simulated, curve-fitted values, and experimental results validate both the employed numerical approach and rheological model.

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.

Experimental setup with automatic control. High pressure VLE data of binary systems 2–Butanol with n–Heptane and 2,2,4–Trimethylpentane at both 1.5 MPa and 2.0 MPa

2020 ◽  
Vol 142 ◽  
pp. 105997
Author(s):  
P. Susial Badajoz ◽  
D. García-Vera ◽  
A.J. Marrero-Pérez ◽  
P. Herrera-Vega ◽  
C. Rodríguez-Domínguez ◽  
...  
Keyword(s):  
High Pressure ◽  
Automatic Control ◽  
Binary Systems ◽  
Experimental Setup ◽  
Vle Data

The Use of Novel F-RAFT Agents in High Temperature and High Pressure Ethene Polymerization: Can Control be Achieved?

2007 ◽  
Vol 60 (10) ◽  
pp. 788 ◽  
Author(s):  
Markus Busch ◽  
Marion Roth ◽  
Martina H. Stenzel ◽  
Thomas P. Davis ◽  
Christopher Barner-Kowollik
Keyword(s):  
Molecular Weight ◽  
High Pressure ◽  
High Temperature ◽  
Degree Of Polymerization ◽  
Molecular Weight Distributions ◽  
High Pressure High Temperature ◽  
Reversible Addition ◽  
Weight Distributions ◽  
Raft Agent ◽  
Initial Results

Simulations are employed to establish the feasibility of achieving controlled/living ethene polymerizations. Such simulations indicate that reversible addition–fragmentation chain transfer (RAFT) agents carrying a fluorine Z group may be suitable to establish control in high-pressure high-temperature ethene polymerizations. Based on these simulations, specific fluorine (F-RAFT) agents have been designed and tested. The initial results are promising and indicate that it may indeed be possible to achieve molecular weight distributions with a polydispersity being significantly lower than that observed in the conventional free radical process. In our initial trials presented here (using the F-RAFT agent isopropylfluorodithioformate), a correlation between the degree of polymerization and conversion can indeed be observed. Both the lowered polydispersity and the linear correlation between molecular weight and conversion indicate that control may in principle be possible.

Scaling of high-pressure viscosity data in low-molecular-weight glass-forming liquids

1999 ◽  
Vol 60 (5) ◽  
pp. 2979-2982 ◽  
Author(s):  
M. Paluch ◽  
Z. Dendzik ◽  
S. J. Rzoska
Keyword(s):  
Molecular Weight ◽  
High Pressure ◽  
Low Molecular Weight ◽  
Viscosity Data ◽  
Glass Forming

Scale Effects in Generalized Newtonian Elastohydrodynamic Films

2008 ◽  
Author(s):  
I. I. Kudish ◽  
P. Kumar ◽  
M. M. Khonsary ◽  
S. Bair
Keyword(s):  
Film Thickness ◽  
Scale Effects ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Viscosity Coefficient ◽  
Shear Thinning ◽  
Effective Pressure ◽  
Practical Advantage ◽  
Inlet Zone ◽  
Real Machine

The prediction of elastohydrodynamic lubrication (EHL) film thickness requires knowledge of the lubricant properties. Today, in many instances, the properties have been obtained from a measurement of the central film thickness in an optical EHL point contact simulator and the assumption of a classical Newtonian film thickness formula. This technique has the practical advantage of using an effective pressure-viscosity coefficient which compensates for shear-thinning. We have shown by a perturbation analysis and by a full EHL numerical solution that the practice of extrapolating from a laboratory scale measurement of film thickness to the film thickness of an operating contact within a real machine may substantially overestimate the film thickness in the real machine if the machine scale is smaller and the lubricant is shear-thinning in the inlet zone.

Study of the permeability of fluorinated high-pressure polyethylene for temporary fuel storage

2021 ◽  
pp. 65-69
Author(s):  
Юрий Николаевич Рыбаков ◽  
Александр Васильевич Дедов ◽  
Роман Игоревич Кюннап ◽  
Сергей Владимирович Ларионов
Keyword(s):  
Molecular Weight ◽  
High Pressure ◽  
Diesel Fuel ◽  
Permeability Coefficient ◽  
Layer Structure ◽  
Storage Period ◽  
High Pressure Polyethylene ◽  
Fuel Storage ◽  
Two Stages ◽  
Kinetics Of

Исследована проницаемость фторированного полиэтилена высокого давления (ПВД), предназначенного для изготовления ремонтных и технологических вкладышей резервуаров складов временного хранения топлива. Использование таких вкладышей позволяет снизить технологические потери углеводородов и увеличить надежность хранилищ из полимерных материалов. В качестве объекта исследования использовали пленки ПВД 10204-003 толщиной 100 мкм. Проницаемость пленок определяли при контакте с бензином марок Нормаль-80, Премиум-95, авиационным керосином ТС-1 и дизельным топливом. Рассмотрен механизм формирования структуры поверхностного фторированного слоя. Исследована кинетика изменения коэффициента проницаемости исходного и модифицированного полиэтилена в течение возможного срока хранения топлив. По результатам исследования установлено: 1) в полиэтилене перенос топлива протекает в две стадии, что определяется раздельной диффузией низкомолекулярных и высокомолекулярных фракций углеводородов; 2) фторирование полиэтилена приводит к уменьшению коэффициента проницаемости (что имеет практическое значение для сохранения качества топлива), но не влияет на перенос фракции углеводородов минимальной молекулярной массы. The permeability of fluorinated high-pressure polyethylene (HDPE), intended for the manufacture of repair and technological liners of tanks for temporary fuel storage has been investigated. As the object of research, 10204-003 HDPE films with 100 μm thickness were used. The permeability of the films was determined by contact with gasoline of the Normal-80 and Premium-95 brands, aviation kerosene TS-1, and diesel fuel. The formation mechanism of the surface fluorinated layer structure was considered. The kinetics of changes in the permeability coefficient of the original and modified polyethylene during the possible fuel storage period has been studied. It has been established that the transfer of fuel in polyethylene proceeds in two stages, which is determined by the separate diffusion of low-molecular and high-molecular hydrocarbon fractions. Fluoridation of polyethylene decreases the permeability coefficient, but does not affect the transfer of hydrocarbon fraction with the minimum molecular weight.

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