CA1207559A - High shear rate/high temperature viscometer - Google Patents
High shear rate/high temperature viscometerInfo
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- CA1207559A CA1207559A CA000448238A CA448238A CA1207559A CA 1207559 A CA1207559 A CA 1207559A CA 000448238 A CA000448238 A CA 000448238A CA 448238 A CA448238 A CA 448238A CA 1207559 A CA1207559 A CA 1207559A
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Abstract
ABSTRACT
This invention involves an apparatus and a method involving such apparatus for making rapid viscometric measurements of fluids at high shear rates and high temperatures, said apparatus comprising:
a) container means for housing a sample fluid and movable piston means, b) inlet means for providing a sample to said container, c) capillary tube outlet means located at one end of said container means, said capillary tube means having a temperature control means, d) piston means movably positioned within said container.
e) constant speed motor means connected with piston drive means for moving said piston through said container at a constant speed to force sample fluid through the outlet capillary at a constant volumetric flow rate, f) pressure transducer means for measuring the pressure generated in said container at the capillary tube entrance, and g) the container means being adapted with heating means for heating sample fluid to a selected temperature.
This invention involves an apparatus and a method involving such apparatus for making rapid viscometric measurements of fluids at high shear rates and high temperatures, said apparatus comprising:
a) container means for housing a sample fluid and movable piston means, b) inlet means for providing a sample to said container, c) capillary tube outlet means located at one end of said container means, said capillary tube means having a temperature control means, d) piston means movably positioned within said container.
e) constant speed motor means connected with piston drive means for moving said piston through said container at a constant speed to force sample fluid through the outlet capillary at a constant volumetric flow rate, f) pressure transducer means for measuring the pressure generated in said container at the capillary tube entrance, and g) the container means being adapted with heating means for heating sample fluid to a selected temperature.
Description
2 This invention relates to an apparatus and
3 method for making rapid viscometric measurements of
4 fluids at high shear rates and high temperatures.
Viscosity, which is a measure of the resis-6 tance of a fluid to flow is one of the most significant 7 physical properties of any particular fluid. Because 8 viscosity is the parameter which affects the flow of g fluids, its measurement is essential in many industrial processes, engineering calculations and the more funda-11 mental sciences.
12 Generally, there are three fundamental types 13 of viscometers in use, i.e., capillary viscometers, 14 rotational viscometers and falling-sphere viscometers.
Most capillary tube viscometers are based on 16 Poiseuille's Law and relate the viscosity to the time of 17 flow for a constant volume of liquid. Viscometers of 18 this type include the Cannon-Fenske type viscometer, 19 the Saybolt Universal Viscometer, ~he SIL tStandard In~pection Laboratory) viscometer and the Ubbelohde 21 viscometer.
22 Rotational viscometers are mechanically more 23 complicated than capillary viscometers. They are 24 generally comprised of two members, a rotor and a stator ~5 which are separated by the test fluid. The test fluid 26 is contained in the gap between the rotor and stator 27 and is sheared by the rotation of the rotor relative to 28 the stator. The rotor produces shearing action on the 29 liquid which is transmitted to the stator. The torque required to produce a given angular velocity or the 31 angular velocity resulting from a given torque is a i 1~207559 l measurement of the viscosity. One commonly used rota-2 tional viscometer is the Brookfield Synchro-Lectric 3 viscometer and others of this type include the Stormer 4 and MacMichael viscometers.
Viscometers of the falling~sphere type are 6 based on the application of Stokes' Law. While such 7 viscometers are useful over a fairly wide viscosity 8 range, they usually are not capable of as high precision 9 and accuracy as the capillary and rotational viscometers Further information regarding viscome~ry and ll the types of viscometers noted above, may be found in 12 Kirk-Othmer's "Encyclopedia of Chemical Technology, 13 Second Edition, 1970, vol. 21, pp. 460 to 484.
14 While generally, the various types of vis-cometers illustrated above, have been used over a long 16 period of time to provide very useful viscosity measure-17 men~s for different fluids, a growing interest has 18 recently developed to obtain viscosity measurements at 19 much higher shear rates than available instrumentation can provide. One area where such need exists is in the 21 field of automotive engine oils and other lubricants 22 where high shear rates are quite common. Currently, 23 the method of determining the SAE viscosity grade of 24 multigrade engine oils at high temperature is based on a kinematic viscosity at 100C measured in the Cannon-26 Fenske glass capillary viscometer (ASTM D445). This 27 Cannon-Fenske viscometer shears the liquid at very slow 28 rates typically 200 to 300 s-l and by comparison, a 29 running engine can shear the lubricant at a rate of 3~ approximately 10~ s-l and engine oil temperatures can 31 re~ch lS0C.
~ ~2075S9 While some instruments are available to measure viscosity under the desired conditions of high shear rate and temperature, they are typically labor intensive, require larse sample volumes and/or have 910w sample turnover times. Consequently, they are not particularly suitable for routine every dsy operations where rapid measurements are desired with less d~pendence on a skilled operator.
S~HMARY OF THE INVENTION
Now in sccordance with this invention, an apparstus Qnd method have been developed for making rapid viscometric measurements of fluids at high shear rates ~nd high temperatures.
~ore particularly, this invention is directed to an apparatus for measuring the viscosity of a fluid comprislng:
a) container means for housing a sample fluid and mo~able piston means, b) inlet means for providing a sample to said container, c) capillary tube outlet means located at one end of said container me~ns, said capillary tube means having a temper~ture control means, d~ piston means movably positioned within said container, e) constant speed motor means connected with piston drive mesns for moving said piston through said container at a constant speed to force sample fluid through the outlet capillary at a constant volumetric flow rate, f? pressure transducer means for messuring the pressure generated in sald container at the capillary tube entrance, and g~ the container means being adapted with heating means for heating sample fluid to a selected temperature.
, - 3 -lZ07SS~
Another embodiment of this invention relates to a method for the rapid measurement of the viscosity of a fluid under high shear and high temperature conditions comprising:
a) placing a test fluid sample into a container housing an outlet capillary tube and a movable piston, b~ h~ating said sample $1uid to a selected temperature, c) driving said piston at a selected constant speed to force the test fluid through the outlet capillsry at a constQnt volumetric flow rate, d) measuring the pressure generated in said container at the entrance o$
the capillary while said fluid is being force through, and e~ converting said pressure measurement to a value corresponding to the - viscosity of said test fluid.
In a preferred embodiment, the present apparatus may include temperature control means for said capillary tube outlet ~eans which comprises a hesting means wrapped around said capillary tube means.
BRIEF DESCRIPTION OF THE DRAWINGS
The instant invention may be better understood by reference to the accompanying drawing wherein:
~ - 4 -:1~07~;59 1 Figure 1 illustrates schematically the overall 2 viscometer apparatus of this invention;
3 Figure 2 illustrates schematically in more 4 detail, the piston-cylinder arrangement of the vis-cometer apparatus of this invention; and 6 Figure 3 is a graphical îllustration of volts 7 (pressure analog) vs viscosity (cP) for a particular 8 fluid at a selected æhear rate. I
!
This invention involves an apparatus and 11 method for measuring the viscosity of a fluid at high 12 shear rates and high temperatures in a relatively rapid 13 manner.
14 Dynamic viscosity is a proportionately con-stant which relates the rate at which a fluid shears to 16 the shear stress applied to that fluid. For fluid flow 17 through a capillary, the shear rate and shear stress are 18 defined by the following equations: !
19 SR = 4Q (1) ~ r3 i .
where SR = shear rate 21 ~ Q = volumetric flow rate 22 r = capillary radius 23 Ss = pr (2) 24 where Ss = shear stress p = pressure differential 26 a~ross the capillary , ,.
1~07~Sg 1 1 = length of capillary 2 r = capillary radius 3 The viscosity n can be determined from the 4 Poiseuille-~agen equation:
n = S5 ~ pr4 (3j Sr 8Q1 6 For a constant flow rate ~, and fixed capil-7 lary dimensions, r and 1, examination of equation 3 8 shows that the viscosity n is directly proportional to 9 the pressure differential across the capillary p. By rearranging equation 3, this pressure differential 11 across the capillary p is defined by equation 4 as 12 follows: !:
13 P =n ( 8Q 1 ) (4) ~ r4 -14 The viscometer apparatus of this invention forces a 1uid through the capillary at a constant 16 volumetric flow rate and this allows the viscosity 17 to be measured as a function of the pressure generated 18 in the cylinder. However, the pressure generated in 19 the cylinder, i.e. p observed, represents the pressure f-at the mouth or entrance of the capillary and is not 21 simply the pressure drop across the capillary as requir-22 ed in equation 3. The reason for this is that the 23 pressure observed also contains a pressure contribution 24 due to the kinetic energy of the effluent strea~. Thus, 25 the pressure observed is therefore greater by the amount l~
26 of the kinetic energy of the effluent stream than the ¦;
27 actual pressure drop across the capillary. The pressure j~
28 observed can be corrected for this kinetic energy L .
i:, 1~207~59 1 contribution in accordance with the following equation - 2 5:
3 P = Pobserved ~ d(Va)2/~ (5) 4 where d = density of the fluid Va = average velocity of fluid 6 in the capillary 7 ~ = a correction factor 8 By rearranging equation 5 and substituting 9 the differential pressure across the capillary p, by equation 4, the relationship between the pressure 11 observed in the cylinder and the viscosity can be 12 rewritten as follows:
13 Pobserved = ~ ( 4) + d~Va)2/~ t6) 14 The correction factor found in the above equations 5 and 6, is usually about 1 for the vast 16 majority of fluids and therefore, generally can be 17 dropped out of the equation making the relationship 18 between the pressure observed and the viscosity as 19 follQws:
PObserved ~ n ( 8Q 4) + d(Va)2 21 Equation (7) demonstrates that a plot of the 22 pressure observed within the cylinder can be related to 23 the viscosity by a straight line having a positive 24 intercept equal to the kinetic energy term and a slope egual to a constant. With a capillary of known radius 26 and a cylinder of known dimensions, a piston speed 27 needed to give a particular shear rate can be calculated :' i2(:~7S:;9 1 For a given shear rate, a calibration curve can then be 2 constructed with Newtonion calibration oils of known 3 viscosity. A typical cali~ration curve is illustrated 4 by Figure 3, which shows the volts (analogous to pres-
Viscosity, which is a measure of the resis-6 tance of a fluid to flow is one of the most significant 7 physical properties of any particular fluid. Because 8 viscosity is the parameter which affects the flow of g fluids, its measurement is essential in many industrial processes, engineering calculations and the more funda-11 mental sciences.
12 Generally, there are three fundamental types 13 of viscometers in use, i.e., capillary viscometers, 14 rotational viscometers and falling-sphere viscometers.
Most capillary tube viscometers are based on 16 Poiseuille's Law and relate the viscosity to the time of 17 flow for a constant volume of liquid. Viscometers of 18 this type include the Cannon-Fenske type viscometer, 19 the Saybolt Universal Viscometer, ~he SIL tStandard In~pection Laboratory) viscometer and the Ubbelohde 21 viscometer.
22 Rotational viscometers are mechanically more 23 complicated than capillary viscometers. They are 24 generally comprised of two members, a rotor and a stator ~5 which are separated by the test fluid. The test fluid 26 is contained in the gap between the rotor and stator 27 and is sheared by the rotation of the rotor relative to 28 the stator. The rotor produces shearing action on the 29 liquid which is transmitted to the stator. The torque required to produce a given angular velocity or the 31 angular velocity resulting from a given torque is a i 1~207559 l measurement of the viscosity. One commonly used rota-2 tional viscometer is the Brookfield Synchro-Lectric 3 viscometer and others of this type include the Stormer 4 and MacMichael viscometers.
Viscometers of the falling~sphere type are 6 based on the application of Stokes' Law. While such 7 viscometers are useful over a fairly wide viscosity 8 range, they usually are not capable of as high precision 9 and accuracy as the capillary and rotational viscometers Further information regarding viscome~ry and ll the types of viscometers noted above, may be found in 12 Kirk-Othmer's "Encyclopedia of Chemical Technology, 13 Second Edition, 1970, vol. 21, pp. 460 to 484.
14 While generally, the various types of vis-cometers illustrated above, have been used over a long 16 period of time to provide very useful viscosity measure-17 men~s for different fluids, a growing interest has 18 recently developed to obtain viscosity measurements at 19 much higher shear rates than available instrumentation can provide. One area where such need exists is in the 21 field of automotive engine oils and other lubricants 22 where high shear rates are quite common. Currently, 23 the method of determining the SAE viscosity grade of 24 multigrade engine oils at high temperature is based on a kinematic viscosity at 100C measured in the Cannon-26 Fenske glass capillary viscometer (ASTM D445). This 27 Cannon-Fenske viscometer shears the liquid at very slow 28 rates typically 200 to 300 s-l and by comparison, a 29 running engine can shear the lubricant at a rate of 3~ approximately 10~ s-l and engine oil temperatures can 31 re~ch lS0C.
~ ~2075S9 While some instruments are available to measure viscosity under the desired conditions of high shear rate and temperature, they are typically labor intensive, require larse sample volumes and/or have 910w sample turnover times. Consequently, they are not particularly suitable for routine every dsy operations where rapid measurements are desired with less d~pendence on a skilled operator.
S~HMARY OF THE INVENTION
Now in sccordance with this invention, an apparstus Qnd method have been developed for making rapid viscometric measurements of fluids at high shear rates ~nd high temperatures.
~ore particularly, this invention is directed to an apparatus for measuring the viscosity of a fluid comprislng:
a) container means for housing a sample fluid and mo~able piston means, b) inlet means for providing a sample to said container, c) capillary tube outlet means located at one end of said container me~ns, said capillary tube means having a temper~ture control means, d~ piston means movably positioned within said container, e) constant speed motor means connected with piston drive mesns for moving said piston through said container at a constant speed to force sample fluid through the outlet capillary at a constant volumetric flow rate, f? pressure transducer means for messuring the pressure generated in sald container at the capillary tube entrance, and g~ the container means being adapted with heating means for heating sample fluid to a selected temperature.
, - 3 -lZ07SS~
Another embodiment of this invention relates to a method for the rapid measurement of the viscosity of a fluid under high shear and high temperature conditions comprising:
a) placing a test fluid sample into a container housing an outlet capillary tube and a movable piston, b~ h~ating said sample $1uid to a selected temperature, c) driving said piston at a selected constant speed to force the test fluid through the outlet capillsry at a constQnt volumetric flow rate, d) measuring the pressure generated in said container at the entrance o$
the capillary while said fluid is being force through, and e~ converting said pressure measurement to a value corresponding to the - viscosity of said test fluid.
In a preferred embodiment, the present apparatus may include temperature control means for said capillary tube outlet ~eans which comprises a hesting means wrapped around said capillary tube means.
BRIEF DESCRIPTION OF THE DRAWINGS
The instant invention may be better understood by reference to the accompanying drawing wherein:
~ - 4 -:1~07~;59 1 Figure 1 illustrates schematically the overall 2 viscometer apparatus of this invention;
3 Figure 2 illustrates schematically in more 4 detail, the piston-cylinder arrangement of the vis-cometer apparatus of this invention; and 6 Figure 3 is a graphical îllustration of volts 7 (pressure analog) vs viscosity (cP) for a particular 8 fluid at a selected æhear rate. I
!
This invention involves an apparatus and 11 method for measuring the viscosity of a fluid at high 12 shear rates and high temperatures in a relatively rapid 13 manner.
14 Dynamic viscosity is a proportionately con-stant which relates the rate at which a fluid shears to 16 the shear stress applied to that fluid. For fluid flow 17 through a capillary, the shear rate and shear stress are 18 defined by the following equations: !
19 SR = 4Q (1) ~ r3 i .
where SR = shear rate 21 ~ Q = volumetric flow rate 22 r = capillary radius 23 Ss = pr (2) 24 where Ss = shear stress p = pressure differential 26 a~ross the capillary , ,.
1~07~Sg 1 1 = length of capillary 2 r = capillary radius 3 The viscosity n can be determined from the 4 Poiseuille-~agen equation:
n = S5 ~ pr4 (3j Sr 8Q1 6 For a constant flow rate ~, and fixed capil-7 lary dimensions, r and 1, examination of equation 3 8 shows that the viscosity n is directly proportional to 9 the pressure differential across the capillary p. By rearranging equation 3, this pressure differential 11 across the capillary p is defined by equation 4 as 12 follows: !:
13 P =n ( 8Q 1 ) (4) ~ r4 -14 The viscometer apparatus of this invention forces a 1uid through the capillary at a constant 16 volumetric flow rate and this allows the viscosity 17 to be measured as a function of the pressure generated 18 in the cylinder. However, the pressure generated in 19 the cylinder, i.e. p observed, represents the pressure f-at the mouth or entrance of the capillary and is not 21 simply the pressure drop across the capillary as requir-22 ed in equation 3. The reason for this is that the 23 pressure observed also contains a pressure contribution 24 due to the kinetic energy of the effluent strea~. Thus, 25 the pressure observed is therefore greater by the amount l~
26 of the kinetic energy of the effluent stream than the ¦;
27 actual pressure drop across the capillary. The pressure j~
28 observed can be corrected for this kinetic energy L .
i:, 1~207~59 1 contribution in accordance with the following equation - 2 5:
3 P = Pobserved ~ d(Va)2/~ (5) 4 where d = density of the fluid Va = average velocity of fluid 6 in the capillary 7 ~ = a correction factor 8 By rearranging equation 5 and substituting 9 the differential pressure across the capillary p, by equation 4, the relationship between the pressure 11 observed in the cylinder and the viscosity can be 12 rewritten as follows:
13 Pobserved = ~ ( 4) + d~Va)2/~ t6) 14 The correction factor found in the above equations 5 and 6, is usually about 1 for the vast 16 majority of fluids and therefore, generally can be 17 dropped out of the equation making the relationship 18 between the pressure observed and the viscosity as 19 follQws:
PObserved ~ n ( 8Q 4) + d(Va)2 21 Equation (7) demonstrates that a plot of the 22 pressure observed within the cylinder can be related to 23 the viscosity by a straight line having a positive 24 intercept equal to the kinetic energy term and a slope egual to a constant. With a capillary of known radius 26 and a cylinder of known dimensions, a piston speed 27 needed to give a particular shear rate can be calculated :' i2(:~7S:;9 1 For a given shear rate, a calibration curve can then be 2 constructed with Newtonion calibration oils of known 3 viscosity. A typical cali~ration curve is illustrated 4 by Figure 3, which shows the volts (analogous to pres-
5 sure observed) vs. viscosi~y for a selected shear rate.
6 This curve is applicable only for a single shear rate r
7 but is essentially independent of temperature.
,~
,~
8 The viscometer apparatus of this invention, as g shown schematically in Figure 1 consists of three basic 10 components: a piston-cylinder, a constant speed motor 11 and a pressure transducer. More specifically, this 12 apparatus involves a cylinder or container 1 into 13 which a capillary tube 2 is fastened or attached. The 14 cylinder houses a movable piston 3 which is driven by 15 a drive rack shown generally as 4 attached or connected 16 to a constant speed motor 5. The piston drive rack 4 17 comprises a brace 6 which bears upon the piston 3 and 18 drives it through the cylinder 1 at a constant speed.
19 This results from the action of the constant speed motor 20 5 which uses a gear set 7 to drive shaft 8 threaded at 21 one end which is supported by bearings 9 suitable for 22 radial and axial loads. The constant rotational speed 23 f the threaded shaft 8 generated by the constant speed 24 motor 5 is converted to a constant translational motion 25 by the brace 6 which is threaded and which is not 26 permitted to rotate. While Figure 1 as described above 27 shows one type of drive rack associated with the con-28 stant speed motor to provide constant translational 29 motion of the piston, other types of drive racks such 30 as a rack and pinion assembly can also be used.
31 The piston-cylinder arrangement of the vis-32 cometer apparatus is illustrated in more detail in 33 Figure 2 wherein the 5yl inder 1 is shown housing the 34 piston 3 and containing a capillary tube 2, pressure 12()7SS~
g 1 transducer means 10, a sample inlet means or injection 2 port 11, "On-ring 12 fitted around the piston to provide 3 dynamic sealing of the piston under the pressures 4 generated, and heating means such as heating tape and insulation wrapped around the cylinder, not shown, 6 and thermocouple 13. The piston drive rack 4 also has 7 stop positions within the cylinder or container, not 8 shown, to limit piston travel and to allow for appli-g cations such as charging the cylinder with fluid and completion of a viscometric determination.
i 11 Pressure transducer means shown generally as 12 10 in Figures 1 and 2 provides an electrical signal that 13 is the analog of pressure generated in the cylinder.
14 This transducer means includes an amplifier/controller 15 which converts and amplifies ~he transducer signal and 16 reads the pressure generated in the cylinder either in 17 volts or directly in psi. A further description of 18 instruments of this type can be found in McGraw-Hill 19 Encyclopedia of Science and Technology, Vol. 10, 1971, 20 pp. 670-674.
21 The method of measuring the viscosity of a 22 fluid in accordance with this invention and the basic 23 operational procedure for the viscometer described above 24 generally involves feeding a fluid, such as an oil, into 25 the cylinder. This may be done using a syringe equipped 26 with a coarse filter. The fluid is then heated to the 27 desired temperature, typically up to about 150C or even 28 higher and the temperature of the capillary is also con- I
29 trolled using means such as an electrical resistance 30 ring heater wrapped around the capillary plug and a 31 thermocouple imbedded close to the capillary wall.
32 The piston is driven by the constant speed motor at a 33 speed suitable to obtain ~he desired shear rate. This 34 will depend on the capillary dimensions as well as t 35 the flow rateO As the piston progresses through the 1~0'7S59 1 cylinder it pushes fluid through the cylinder and out 2 the capillary tube at a constant flow rate. The maximum 3 steady state pressure generated within the cylinder 4 is measured by the voltage signal from the pressure 5 transducer means. This voltage signal is directly 6 proportional or analogous to the pressure and through 7 the use of a calibration curve of the type shown in 8 Figure 3 the viscosity of the sample fluid is determined g for the selected shear rate. The calibration curve of 10 Figure 3 represents a plot of volts vs. viscosity for a 11 series of standard test fluids of known viscosity using 12 the viscometer apparatus of this invention at a selected 13 shear rate.
14 The viscometer apparatus and method of this 15 invention is generally applicable to any fluid for which 16 viscosity measurements are desired and is particularly 17 useful for viscosity determinations of petroleum hydro-18 carbon products such as lubricants and engine oils.
19 This apparatus and method is particularly u~eful at high 20 shear rates of up to about 105 to 2 to 3 x 106 S-l and 21 even higher, preferably in the range of about 1 to 2 x 22 106 S-l. Generally, this apparatus and method is appli-23 cable at fairly high temperatures, typically up to the 24 smoke point of the petroleum product or fluid, i.e. the 25 point at which the fluid gives off some rancid fumes or 26 becomes too hot and begins to decompose. Temperatures 27 may be as high as about 200C and even higher and pre- t 28 ferably up to about 175C.
29 The following examples are further illustra-30 tive of this invention and are not intended to be 31 construed as limitations thereof.
:-~07~S5~
2 The viscosity of eight reference oils was 3 determined using the viscometer of this invention. The 4 procedure involved taking a 12 ml. oil sample and intro-ducing it into the viscometer cylinder via a syringe 6 and then heating to 150C in about 2-3 minutes. The 7 cylinder was made from 303 stainless steel with a 8 copper-beryllium sleeve in the cylinder to act as a g bushing for non-binding motion of the piston. The capillary tube was also fabricated of stainless steel.
11 An oil resistant rubber "O" ring was fitted about 5 mm 12 from the piston top and provided dynamic sealing of the 13 piston. The cylinder was wrapped with heating tape and -14 insulation to provide the desired temperature.
15 The piston constructed of 316 stainless steel 16 was driven at a speed suitable to achieve a shear rate 17 of 106 s-l for this particular apparatus configuration.
18 As the piston was driven down the cylinder, the maximum 19 steady state pressure generated within the cylinder was 20 noted as indicated on the pressure transducer means. i-21 This signal, which was in volts, was converted to vis- ' 22 cosity through the use of a calibration curve such as r 23 Figure 3~ The attached table shows the results of ~;
24 the eight reference oils for this viscometer and the 25 comparable results for a number of different viscometers 26 used in the industry.
27 The results show that the viscometer of this 2~ invention gives viscosity measurements for sample refer- j 29 ence oils which are of comparable order to measurements 30 obtained using other viscometers. Further, the results t 31 show that the apparatus of this invention is capable of 32 high temperature, high shear measurements using small 33 samples with fast turnover time and involves relatively 34 simple procedures to carry out. t-~07S59 Ul O~ 0 r~
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19 This results from the action of the constant speed motor 20 5 which uses a gear set 7 to drive shaft 8 threaded at 21 one end which is supported by bearings 9 suitable for 22 radial and axial loads. The constant rotational speed 23 f the threaded shaft 8 generated by the constant speed 24 motor 5 is converted to a constant translational motion 25 by the brace 6 which is threaded and which is not 26 permitted to rotate. While Figure 1 as described above 27 shows one type of drive rack associated with the con-28 stant speed motor to provide constant translational 29 motion of the piston, other types of drive racks such 30 as a rack and pinion assembly can also be used.
31 The piston-cylinder arrangement of the vis-32 cometer apparatus is illustrated in more detail in 33 Figure 2 wherein the 5yl inder 1 is shown housing the 34 piston 3 and containing a capillary tube 2, pressure 12()7SS~
g 1 transducer means 10, a sample inlet means or injection 2 port 11, "On-ring 12 fitted around the piston to provide 3 dynamic sealing of the piston under the pressures 4 generated, and heating means such as heating tape and insulation wrapped around the cylinder, not shown, 6 and thermocouple 13. The piston drive rack 4 also has 7 stop positions within the cylinder or container, not 8 shown, to limit piston travel and to allow for appli-g cations such as charging the cylinder with fluid and completion of a viscometric determination.
i 11 Pressure transducer means shown generally as 12 10 in Figures 1 and 2 provides an electrical signal that 13 is the analog of pressure generated in the cylinder.
14 This transducer means includes an amplifier/controller 15 which converts and amplifies ~he transducer signal and 16 reads the pressure generated in the cylinder either in 17 volts or directly in psi. A further description of 18 instruments of this type can be found in McGraw-Hill 19 Encyclopedia of Science and Technology, Vol. 10, 1971, 20 pp. 670-674.
21 The method of measuring the viscosity of a 22 fluid in accordance with this invention and the basic 23 operational procedure for the viscometer described above 24 generally involves feeding a fluid, such as an oil, into 25 the cylinder. This may be done using a syringe equipped 26 with a coarse filter. The fluid is then heated to the 27 desired temperature, typically up to about 150C or even 28 higher and the temperature of the capillary is also con- I
29 trolled using means such as an electrical resistance 30 ring heater wrapped around the capillary plug and a 31 thermocouple imbedded close to the capillary wall.
32 The piston is driven by the constant speed motor at a 33 speed suitable to obtain ~he desired shear rate. This 34 will depend on the capillary dimensions as well as t 35 the flow rateO As the piston progresses through the 1~0'7S59 1 cylinder it pushes fluid through the cylinder and out 2 the capillary tube at a constant flow rate. The maximum 3 steady state pressure generated within the cylinder 4 is measured by the voltage signal from the pressure 5 transducer means. This voltage signal is directly 6 proportional or analogous to the pressure and through 7 the use of a calibration curve of the type shown in 8 Figure 3 the viscosity of the sample fluid is determined g for the selected shear rate. The calibration curve of 10 Figure 3 represents a plot of volts vs. viscosity for a 11 series of standard test fluids of known viscosity using 12 the viscometer apparatus of this invention at a selected 13 shear rate.
14 The viscometer apparatus and method of this 15 invention is generally applicable to any fluid for which 16 viscosity measurements are desired and is particularly 17 useful for viscosity determinations of petroleum hydro-18 carbon products such as lubricants and engine oils.
19 This apparatus and method is particularly u~eful at high 20 shear rates of up to about 105 to 2 to 3 x 106 S-l and 21 even higher, preferably in the range of about 1 to 2 x 22 106 S-l. Generally, this apparatus and method is appli-23 cable at fairly high temperatures, typically up to the 24 smoke point of the petroleum product or fluid, i.e. the 25 point at which the fluid gives off some rancid fumes or 26 becomes too hot and begins to decompose. Temperatures 27 may be as high as about 200C and even higher and pre- t 28 ferably up to about 175C.
29 The following examples are further illustra-30 tive of this invention and are not intended to be 31 construed as limitations thereof.
:-~07~S5~
2 The viscosity of eight reference oils was 3 determined using the viscometer of this invention. The 4 procedure involved taking a 12 ml. oil sample and intro-ducing it into the viscometer cylinder via a syringe 6 and then heating to 150C in about 2-3 minutes. The 7 cylinder was made from 303 stainless steel with a 8 copper-beryllium sleeve in the cylinder to act as a g bushing for non-binding motion of the piston. The capillary tube was also fabricated of stainless steel.
11 An oil resistant rubber "O" ring was fitted about 5 mm 12 from the piston top and provided dynamic sealing of the 13 piston. The cylinder was wrapped with heating tape and -14 insulation to provide the desired temperature.
15 The piston constructed of 316 stainless steel 16 was driven at a speed suitable to achieve a shear rate 17 of 106 s-l for this particular apparatus configuration.
18 As the piston was driven down the cylinder, the maximum 19 steady state pressure generated within the cylinder was 20 noted as indicated on the pressure transducer means. i-21 This signal, which was in volts, was converted to vis- ' 22 cosity through the use of a calibration curve such as r 23 Figure 3~ The attached table shows the results of ~;
24 the eight reference oils for this viscometer and the 25 comparable results for a number of different viscometers 26 used in the industry.
27 The results show that the viscometer of this 2~ invention gives viscosity measurements for sample refer- j 29 ence oils which are of comparable order to measurements 30 obtained using other viscometers. Further, the results t 31 show that the apparatus of this invention is capable of 32 high temperature, high shear measurements using small 33 samples with fast turnover time and involves relatively 34 simple procedures to carry out. t-~07S59 Ul O~ 0 r~
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Claims (10)
IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An apparatus for measuring the viscosity of a fluid comprising:
a) container means for housing a sample fluid and movable piston means, b) inlet means for providing a sample to said container, c) capillary tube outlet means located at one end of said container means, said capillary tube means having a temperature control means, d) piston means movably positioned within said container, e) constant speed motor means connected with piston drive means for moving said piston through said container at a constant speed to force sample fluid through the outlet capillary at a constant volumetric flow rate, f) pressure transducer means for measuring the pressure generated in said container at the capillary tube entrance, and g) the container means being adapted with heating means for heating sample fluid to a selected temperatures.
a) container means for housing a sample fluid and movable piston means, b) inlet means for providing a sample to said container, c) capillary tube outlet means located at one end of said container means, said capillary tube means having a temperature control means, d) piston means movably positioned within said container, e) constant speed motor means connected with piston drive means for moving said piston through said container at a constant speed to force sample fluid through the outlet capillary at a constant volumetric flow rate, f) pressure transducer means for measuring the pressure generated in said container at the capillary tube entrance, and g) the container means being adapted with heating means for heating sample fluid to a selected temperatures.
2. The apparatus of claim 1 wherein said piston drive means comprises a gear set, threaded shaft and brace adapted to said constant speed motor to cause the brace and the piston upon which it bears to move with constant translational motion.
3. A method for measuring the viscosity of a fluid under high shear and high temperature conditions comprising:
a) placing 8 test fluid sample into a container housing an outlet capillary tube and a movable piston, b) heating said sample fluid to a selected temperature of up to about 200°C, c) driving said piston at a selected constant speed to force the test fluid through the outlet capillary at a constant volumetric flow rate and to achieve a shear rate of up to about 2 to 3 x 106 S-1 at a substantially constant temperature, d) measuring the pressure generated in said container at the entrance of the capillary while said fluid is being forced through, and e) converting said pressure measurement to a value corresponding to the viscosity of said test fluid.
a) placing 8 test fluid sample into a container housing an outlet capillary tube and a movable piston, b) heating said sample fluid to a selected temperature of up to about 200°C, c) driving said piston at a selected constant speed to force the test fluid through the outlet capillary at a constant volumetric flow rate and to achieve a shear rate of up to about 2 to 3 x 106 S-1 at a substantially constant temperature, d) measuring the pressure generated in said container at the entrance of the capillary while said fluid is being forced through, and e) converting said pressure measurement to a value corresponding to the viscosity of said test fluid.
4. The method of claim 3 wherein said fluid is heated to a temperature of up to about 200°C and the piston is driven at a constant speed such as to achieve a shear rate of up to about 2 to 3 x 106 S-1.
5. The method of claim 3 wherein said pressure measurement is converted to viscosity using a curve of pressure vs viscosity derived from the equation:
Pobserved= where Pobserved = pressure observed within the container n = viscosity Q = volumetric flow rate 1 = length of capillary r = capillary radius d = density of fluid Va = average velocity of fluid in capillary
Pobserved= where Pobserved = pressure observed within the container n = viscosity Q = volumetric flow rate 1 = length of capillary r = capillary radius d = density of fluid Va = average velocity of fluid in capillary
6. The method of claim 5 wherein said fluid is heated to a temperature of up to about 200°C and the piston is driven at a constant speed such as to achieve a shear rate of up to about 2 to 3 x 106 S-1.
7. The method of claim 6 wherein the piston is driven at a constant speed such as to achieve a shear rate in the range of about 1 to 2 x 106 S-1.
8. The method of claim 6 wherein said fluid is a petroleum hydrocarbon.
9. The method of claim 8 wherein said fluid is an automotive engine oil.
10. The apparatus of claim 1 wherein the temperature control means for said capillary tube outlet means comprises a heating means wrapped around said capillary tube means.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US47792183A | 1983-03-23 | 1983-03-23 | |
| US477,921 | 1983-03-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1207559A true CA1207559A (en) | 1986-07-15 |
Family
ID=23897872
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000448238A Expired CA1207559A (en) | 1983-03-23 | 1984-02-24 | High shear rate/high temperature viscometer |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1207559A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5076096A (en) * | 1986-12-24 | 1991-12-31 | American Telephone And Telegraph Company, At&T Bell Laboratories | Molding of thermoset materials |
| US6023962A (en) * | 1998-01-22 | 2000-02-15 | Cornell Research Foundation, Inc. | Reservoir-slit rheometer for the viscosity measurement of fast-reacting polymers |
| CN114112794A (en) * | 2021-12-02 | 2022-03-01 | 中国建筑材料科学研究总院有限公司 | Measuring device and measuring method for shear viscosity of chalcogenide glass |
-
1984
- 1984-02-24 CA CA000448238A patent/CA1207559A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5076096A (en) * | 1986-12-24 | 1991-12-31 | American Telephone And Telegraph Company, At&T Bell Laboratories | Molding of thermoset materials |
| US6023962A (en) * | 1998-01-22 | 2000-02-15 | Cornell Research Foundation, Inc. | Reservoir-slit rheometer for the viscosity measurement of fast-reacting polymers |
| CN114112794A (en) * | 2021-12-02 | 2022-03-01 | 中国建筑材料科学研究总院有限公司 | Measuring device and measuring method for shear viscosity of chalcogenide glass |
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