Fuel & Combustion 03

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Fuel & Combustion

Engler Viscometer

Fahad Ali Rabbani (M07-126)

Tanveer (M07-110)

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Viscosity

• Viscosity is a measure of the resistance of a fluid which is being deformed by either shear stress or extensional stress.

• Viscosity coefficients– Dynamic viscosity, also absolute viscosity, the

more usual one;– Kinematic viscosity is the dynamic viscosity divided

by the density

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Need?• Process engineers• Design engineers• Unit operations• Storage• Injection• Transportation

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Newton's theory• In general, in any flow, layers move

at different velocities and the fluid's viscosity arises from the shear stress between the layers that ultimately opposes any applied force.

• Isaac Newton postulated that, for straight, parallel and uniform flow, the shear stress, τ, between layers is proportional to the velocity gradient, ∂u /∂y, in the direction perpendicular to the layers.

• Here, the constant μ is known as the coefficient of viscosity, the viscosity, the dynamic viscosity, or the Newtonian viscosity.

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fluids

Newtonian Non-Newtonian

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Factors Affecting Viscosity

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Effect of viscosity on Fuel Oil• Atomization• Preheating• Fluidity • Pumping Cost• Lubrication Cost• Bearing friction• Heat generation• Rate of flow under particular conditions of load,

speed and design

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Types of Viscometer

• CAPILLARY VISCOMETERS – OSTWALD VISCOMETER – MODIFIED OSTWALD VISCOMETERS – Cannon-Fenske Routine Viscometer– Cannon-Manning Semi-micro Viscometer

– Pinkevich Viscometer

• SUSPENDED LEVEL VISCOMETERS FOR TRANSPARENT LIQUID– Ubbelohde Viscometer 29

– Fitzsimons Viscometer 31

– Atlantic Viscometer 33

– Cannon - Ubbelohde Dilution Viscometer

REVERSE FLOW VISCOMETERS 40

• ORIFICE VISCOMETERS 46– RED WOOD VISCOMETER 47

– ENGLER VISCOMETER 51

– SAYBOLT VISCOMETER 51

– FORD VISCOSITY CUP VISCOMETER 54

•

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APPARATUS DESCRIPTIONEngler Viscometer• Mainly used in Germany• It shows the viscosity in Degree Engler

◦E= Efflux time of oil for 200ml Efflux time of water for 200ml

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ENGLER VISCOMETEREngler viscometer is mainly used in former Eastern Europe for measuring viscosities of

lubricating oils. Engler recommended that all viscosities be compared with water. By comparison with standards, lubricating oils may be rated as to its viscosity thus giving one of the values required for a lubricant. A full description of the instrument is given by Stillman19. It is also used for determination of specific viscosity of tars and their fluid products according to ASTM D1665-98 standard. The constructional features of the viscometer are shown in Fig. 2.23. The principle of operation is similar to that of Redwood viscometer. The jet is made of platinum instead of agate. The oil cup of this type of viscometer is made in such a manner that the time for the out flow of 200 mL of water at 20oC is 52 s. However for standardization and calibration of viscometer, the efflux time for 200 mL of distilled water at 20oC is first determined and then the factor representing the efflux time for 50 mL of water at 25oC. The oil container is surrounded by a thermostat and is closed with a lid through which a thermometer, a valve plug and a hand stirrer are introduced. The height of the oil is noted by means of three inverted point gauges (which also indicate the level of the apparatus). The measuring flask is graduated at 100 mL and 200 mL for checking purposes. Engler specific viscosity which is usually expressed as Engler degrees is defined as the ratio of the time ofoutflow of 50 mL of sample at the selected temperature to the time of out flow of the same volume of water at 25oC.

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Engler Viscometer

Basic Parts:

Thermostat

Thermometer

Cover

Valve pin

Level Gauge

Electric Heater

Leveling Screws

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Procedure• Viscometer was cleaned• Sample was taken in oil

cup• Valve was throtled• Time of efflux was noted

for 200ml sample• Same procedure was

repeated for other samples at room temperature

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Observation & Calculation

S.No Temperature

(F)

Time of

Flow

(sec)

Degree Engler

E

Kinematic Viscosity

(Stokes)

Kinematic Viscosity

(Poise)

1 76 398 8.468 0.641 0.73074

2 140 124 2.638 0.1786 0.203262

3 180 95 2.021 0.1189 0.1355

4 210 78 1.660 0.0807 0.092055

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Graph Between Temperature and Kinematic Viscisity

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 50 100 150 200 250

Temperature (F)

Kin

emat

ic V

isco

sity

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Observations and Calculations for the Viscosity of Three Different Lube oils Room Temperature= 20CTime for Water to flow= 60sec

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APPLICATIONS• To find the Viscosity of

Petroleum Products like “Tar”

• Used for finding the viscosity of lube oils.

• Used to test the viscosity of emulsible asphlatum