scholarly journals Low-temperature behaviour of the engine oil

2013 ◽  
Vol 61 (6) ◽  
pp. 1763-1767 ◽  
Author(s):  
Vojtěch Kumbár ◽  
Artüras Sabaliauskas
Keyword(s):  
Low Temperature ◽  
Temperature Dependence ◽  
Low Temperatures ◽  
Kinematic Viscosity ◽  
Engine Oil ◽  
Economic Losses ◽  
Temperature Behaviour ◽  
Engine Oils ◽  
Theoretical Assumptions ◽  
Automobile Engines

The behaviour of engine oil is very important. In this paper has been evaluated temperature dependence kinematic viscosity of engine oils in the low temperatures. Five different commercially distributed engine oils (primarily intended for automobile engines) with viscosity class 0W–40, 5W–40, 10W–40, 15W–40, and 20W–40 have been evaluated. The temperature dependence kinematic viscosity has been observed in the range of temperature from −15 °C to 15 °C (for all oils). Considerable temperature dependence kinematic viscosity was found and demonstrated in case of all samples, which is in accordance with theoretical assumptions and literature data. Mathematical models have been developed and tested. Temperature dependence dynamic viscosity has been modeled using a polynomials 3rd and 4th degree. The proposed models can be used for prediction of flow behaviour of oils. With monitoring and evaluating we can prevent technical and economic losses.

Peotoemission Study of Si (001) Surfaces Exposed to as Flux

1989 ◽  
Vol 148 ◽  
Author(s):  
H. Okumura ◽  
K. Miki ◽  
K. Sakamoto ◽  
T. Sakamoto ◽  
S. Misawa ◽  
...  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Electronic Structures ◽  
Low Temperatures ◽  
Dimer Model ◽  
Surface And Interface ◽  
High And Low Temperatures ◽  
Interface Structures ◽  
Temperature Sample

ABSTRACTPhotoemission spectra (XPS and UPS) of As-covered Si (001) surfaces prepared at high (>600ºC) and low (<450ºC) temperatures and GaAs epilayers subsequently grown on them were measured without exposing to air. It was found that the surface electronic structures of As/Si prepared at the low temperature are different from those of the high temperature sample, the spectra of which can be interpreted as a symmetric dimer model. Differences were also observed between the GaAs epilayers on the As—covered Si surfaces prepared at the high and low temperatures. The temperature dependence of the surface and interface structures are discussed.

scholarly journals Rheological profiles of blends of the new and used motor oils

2013 ◽  
Vol 61 (1) ◽  
pp. 115-121 ◽  
Author(s):  
Vojtěch Kumbár ◽  
Adam Polcar ◽  
Jiří Čupera
Keyword(s):  
Mathematical Model ◽  
Temperature Dependence ◽  
Dynamic Viscosity ◽  
Rheological Behaviour ◽  
Engine Oil ◽  
Engine Oils ◽  
Used Engine Oil ◽  
And Performance ◽  
Increasing Temperature ◽  
Motor Oils

The objective of this paper is to find changes of a rheological profile of the new engine oil if the used engine oil will be add. And also find changes of a rheological profile of the used engine oil if the new engine oil will be add. For these experiments has been created the blends of the new and the used engine oil. The temperature dependence of the density [kg.m−3] has been measured in the range of −10 °C and +60 °C. The instrument Densito 30PX with the scale for measuring engine oils has been used. The dynamic viscosity [mPa.s] has been measured in the range of −10 °C and +100 °C. The Anton Paar digital viscometer with the concentric cylinders geometry has been used. In the accordance with the expected behaviour, the density and the kinematic viscosity of all oils was decreasing with the increasing temperature. To the physical properties has been the mathematical models created. For the temperature dependence of the density has been used the linearly mathematical model and the exponentially mathematical model. For the temperature dependence of the dynamic viscosity has been used the polynomial 6th degree. The knowledge of density and viscosity behaviour of an engine oil as a function of its temperature is of great importance, especially when considering running efficiency and performance of combustion engines. Proposed models can be used for description and prediction of rheological behaviour of engine oils.

Anomalies in the temperature dependence of the yield stress of metals at low temperatures

1983 ◽  
Vol 61 (11) ◽  
pp. 1528-1530 ◽  
Author(s):  
S. M. Raza
Keyword(s):  
Low Temperature ◽  
Temperature Dependence ◽  
Yield Stress ◽  
Low Temperatures ◽  
Structural Changes ◽  
Zero Point ◽  
Quantum Effects ◽  
Enhancement Effect ◽  
Polycrystalline Nickel ◽  
Creep Equation

Yield stress "anomalies" have been studied in polycrystalline nickel at low temperatures. Both quantum effects and structural changes below 0.1–0.2 of the Debye temperature contribute to low-temperature anomalies in the temperature dependence of the yield stress. The anomalies appear to be basically a consequence of the effect of zero-point vibrations on the rates of transition in the localized process of activation. An attempt is made to explain the anomalies by introducing a "strain-enhancement" effect, i.e., f(T), semiempirically in the logrithmic creep equation [Formula: see text] where Teff = T0 + AT2 (T0 and A are constants), which allows for quantum effects below a certain temperature.

SPIN FLUCTUATIONS IN TCo2 STUDIED BY RESISTIVITY AND THERMOPOWER EXPERIMENTS (T = Y, Lu, Sc, Hf, Zr, Ce)

1993 ◽  
Vol 07 (01n03) ◽  
pp. 370-373 ◽  
Author(s):  
N. BARANOV ◽  
E. BAUER ◽  
E. GRATZ ◽  
R. HAUSER ◽  
A. MARKOSYAN ◽  
...  
Keyword(s):  
Low Temperature ◽  
Specific Heat ◽  
Temperature Dependence ◽  
Temperature Region ◽  
Low Temperatures ◽  
Spin Fluctuations ◽  
General Tendency ◽  
Electronic Specific Heat ◽  
Temperature Dependent

The temperature dependence of the resistivity and the thermopower in the region from 4.2K up to 1000K for the six isostructural paramagnetic compounds TCo 2 (T=Y, Lu, Sc, Hf, Zr, Ce) is studied. The resistivity ρ (T) follows a T 2 dependence at low temperatures in all these compounds. Plotting the A values into an A vs. γ2 diagram shows that YCo 2, LuCo 2, and ScCo 2 are spinfluctuation systems (A and γ denote the coefficients in ρ (T) = ρ0 + AT 2 and that of the electronic specific heat, respectively) HfCo 2 and ZrCo 2 do not fit into this general tendency in the ( A , γ2)-diagram. The temperature dependent thermopower S(T) in YCo 2, LuCo 2 and ScCo 2 exhibits a pronounced minimum in the low temperature region. These minima are obviously connected with the existence of spin fluctuations (paramagnon-drag). Spin fluctuations in HfCo 2 and ZrCo 2 are less important. This we conclude also from the ten times smaller A-values and the missing minimum in the thermopower at low temperatures.

The low-temperature behaviour of analcime. 1: high-resolution neutron powder diffraction

1996 ◽  
Vol 60 (400) ◽  
pp. 499-507 ◽  
Author(s):  
C. M. B. Line ◽  
M. T. Dove ◽  
K. S. Knight ◽  
B. Winkler
Keyword(s):  
Phase Transitions ◽  
High Resolution ◽  
Low Temperature ◽  
Powder Diffraction ◽  
Low Temperatures ◽  
Neutron Powder Diffraction ◽  
Water Molecules ◽  
Temperature Behaviour ◽  
Synthetic Sample ◽  
Sodium Cations

AbstractThe structure of a synthetic sample of analcime has been determined as a function of temperature between 30–300 K by high-resolution neutron powder diffraction. Although there are some reports of samples of analcime having non-cubic structures, the sample in our experiments remained cubic (space group la3d), and hence disordered, down to low temperatures. The absence of phase transitions involving ordering of the orientations of the water molecules, ordering of the sodium positions, or a displacive instability as in leucite and related materials, is discussed. We speculate that part of the reason for the absence of ordering of the water molecules or sodium cations is associated with the Al/Si disorder, which cannot order at low temperatures. We also discuss the likely distribution of the orientations of the water molecules at low temperatures, and propose that the water diads lie close to any of the crystal diads with the H-H Vectors lying close to the triads.

scholarly journals Temperature-dependence of open-complex formation at two Escherichia coli promoters with extended −10 sequences

1996 ◽  
Vol 317 (1) ◽  
pp. 305-311 ◽  
Author(s):  
Helen D. BURNS ◽  
Tamara A. BELYAEVA ◽  
Stephen J. W. BUSBY ◽  
Stephen D. MINCHIN
Keyword(s):  
Escherichia Coli ◽  
Low Temperature ◽  
Complex Formation ◽  
Temperature Dependence ◽  
Low Temperatures ◽  
Dna Fragments ◽  
Promoter Sequences ◽  
E Coli ◽  
Base Sequences ◽  
Open Complex Formation

We have studied the formation of open complexes between purified RNA polymerase from Escherichia coli and DNA fragments carrying the galP1 promoter, a promoter with an extended -10 region. Unusually, these complexes are formed readily at low temperatures. This low-temperature opening is unaffected by deletions of either upstream or downstream promoter sequences. We conclude that low-temperature open-complex formation is due to specific base sequences in and just upstream of the extended -10 region. In contrast, open complexes are not formed at low temperatures with DNA fragments carrying the E. coli cysG promoter, which also has an extended -10 region. This demonstrates that an extended -10 sequence alone is not sufficient for low-temperature opening. Additionally, we report the temperature dependence of a hybrid galP1–cysG promoter, the related galP2 and galP3 promoters and a derivative of galP1 with an improved -10 hexamer sequence.

scholarly journals EFFECT OF THE ESTER ON THE RESISTANCE OF ISOPARAFFIN OILS THICKENED WITH ESTER THICKENERS TO MECHANICAL DEGRADATION

2021 ◽  
pp. 58-61
Author(s):  
L. Bagdasarov ◽  
E. Mikhailov
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Entire Range ◽  
Combustion Engine ◽  
Mechanical Degradation ◽  
Lubrication System ◽  
Engine Oils ◽  
Alkyl Chains ◽  
Gear Oil ◽  
Motor Oils

This article examines the effect of esters on the resistance to mechanical degradation of ester thickeners as viscosity modifiers in thickened isoparaffin oils. The main reason for triggering such engine oils is the destruction of the thickener. The introduction of the ester should increase the polymer's resistance to rupture when passing through mechanisms with small gaps – gear oil pumps, in the lubrication system of an internal combustion engine. Also, esters with long alkyl chains should increase the solubility of polar thickeners in low-polar base oils, which can expand the application ranges of such thickeners and increase the resistance of thickened oils to low temperature-to eliminate the precipitation of the thickener at low temperatures. Depending on the thickening capacity of the viscosity modifier, its application may allow the production of motor oils with an extended service life in the entire range of viscosities of commercial oils according to SAE J300.

scholarly journals Analysis of selected results of engine oil tests

2019 ◽  
Vol 302 ◽  
pp. 01010
Author(s):  
Bogdan Landowski ◽  
Monika Baran
Keyword(s):  
Kinematic Viscosity ◽  
Viscosity Index ◽  
Engine Oil ◽  
Lubricating Oil ◽  
Drive Unit ◽  
Passenger Car ◽  
Engine Oils ◽  
Different Temperatures ◽  
Rotary Viscometer

The study presents selected results of viscosity tests performed for different temperatures of lubricating oil with viscosity marked as 5w30. Viscosity tests of new oil and oil right after being used have been compared. Lubricating oil used in a drive unit of a passenger car was tested. A vehicle in which oil had been changed irregularly was purposefully selected for the tests. Its mileage was over 15-20 thousand kilometers. Upon testing the vehicle mileage was above 265 thousand kilometers. The values of selected characteristics of the analyzed engine oils have been determined including: density, kinematic viscosity and viscosity index. FUNGILAB rotary viscometer was used for measurement of the oil kinematic viscosity.

scholarly journals Oils degradation in agricultural machinery

2013 ◽  
Vol 61 (5) ◽  
pp. 1297-1303 ◽  
Author(s):  
Vojtěch Kumbár ◽  
Petr Dostál
Keyword(s):  
Mathematical Models ◽  
Temperature Dependence ◽  
Dynamic Viscosity ◽  
Flow Behavior ◽  
Economic Losses ◽  
Agricultural Machinery ◽  
Theoretical Assumptions

Evaluating of oils condition in agricultural machinery is very important. With monitoring and evaluating we can prevent technical and economic losses. In this paper there were monitored the liquid lubricants taken from mobile thresher New Holland CX 860. Chemical and viscosity degradation of the lubricants were evaluated. Temperature dependence dynamic viscosity was observed in the range of temperature from −10 °C to 80 °C (for all oils). Considerable temperature dependence dynamic viscosity was found and demonstrated in case of all samples, which is in accordance with theoretical assumptions and literature data. Mathematical models were developed and tested. Temperature dependence dynamic viscosity was modeled using a polynomial 6th degree. The proposed models can be used for prediction of flow behavior of oils.

scholarly journals STUDY OF THE COMPATIBILITY OF S-CONTAINING PHENOLIC ANTIOXIDANT ADDITIVES AND OILS FOR TWO-STROKE ENGINES

2021 ◽  
pp. 94-97
Author(s):  
Д.М. Каримова ◽  
А.Ф. Хайдаров ◽  
Г.Ю. Климентова
Keyword(s):  
Low Temperature ◽  
Kinematic Viscosity ◽  
Viscosity Index ◽  
Engine Oil ◽  
Sterically Hindered Phenols ◽  
Base Oils ◽  
Multifunctional Additives ◽  
Hindered Phenols ◽  
High Antioxidant Activity ◽  
Sterically Hindered

Двухтактные двигатели за счет простоты своей конструкции, небольшого количества деталей и компактности пользуются большим спросом во многих отраслях, преимущественно для садовой техники и мотоциклов. В таких двигателях используется бензо-масляная смесь для создания масляной пленки, обеспечения достаточной смазки трущихся деталей и защиты их от коррозии. К современному моторному маслу для двухтактного двигателя существует ряд требований: полное выгорание без образования кокса, золы, отложений, хорошее растворение и перемешивание с топливом, противоизносные, антикоррозионные, смазывающие свойства при высоких температурах. Одновременного выполнения всех требований достичь представляется проблематично. Производители моторных масел используют различные присадки, улучшающие функциональные свойства масел. Известно, что содержание присадки в масле может достигать 3%. В настоящей статье рассматривается возможность использования S-содержащих пространственно-затрудненных фенолов как многофункциональных присадок. Эти вещества обладают высокой антиокислительной активностью за счет своего строения, благодаря которому замедляются процессы окисления. В качестве объекта сравнения были взяты показатели базовых масел, полученные при исследовании низкотемпературных свойств, кинематической вязкости и определении индекса вязкости. Низкотемпературные свойства присадок в смеси с маслом показали возможность использования этих веществ и в качестве пеногасящей присадки. Результаты исследования кинематической вязкости масел с присадками показали небольшое увеличение адсорбционной способности масла на деталях двигателя. Использование S-содержащих пространственно-затрудненных фенолов в составе смазывающей композиции представляется целесообразным. По исследуемым показателям можно видеть, что данные соединения совместимы с базовыми маслами. Two-stroke engines, due to their simplicity of design, a small number of parts and compactness, are in great demand in many industries, mainly for garden equipment and motorcycles. These engines use a petrol-oil mixture to create an oil film, ensure sufficient lubrication of rubbing parts and protect them from corrosion. There are a number of requirements for a modern engine oil for a two-stroke engine: complete burnout without the formation of coke, ash, deposits, good dissolution and mixing with fuel, antiwear, anti-corrosion, lubricating properties at high temperatures. It seems problematic to achieve the simultaneous fulfillment of all requirements. Motor oil manufacturers use a variety of additives to improve the performance of oils. It is known that the additive content in oil can be up to 3%. This article discusses the possibility of using S-containing sterically hindered phenols as multifunctional additives. These substances have high antioxidant activity due to their structure, due to which oxidation processes are slowed down. As an object of comparison, the indicators of base oils were taken, obtained in the study of low-temperature properties, kinematic viscosity and determination of the viscosity index. The low-temperature properties of the additives mixed with oil have shown the possibility of using these substances as a defoaming additive. The results of studying the kinematic viscosity of oils with additives showed a slight increase in the adsorption capacity of the oil on engine parts. The use of S-containing sterically hindered phenols in the composition of the lubricating composition seems to be expedient. According to the studied indicators, it can be seen that these compounds are compatible with base oils.

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