Syncrude/2000/presentations/lubrication1 Lubricated Transport DD Joseph, May 2000 Office of Basic Energy Sciences, Engineering, DOE Some flow types Ideal

Syncrude/2000/presentations/lubrication 1

Lubricated TransportDD Joseph, May 2000

Office of Basic Energy Sciences, Engineering, DOE

•Some flow types•Ideal core-annual flow•Laminar and turbulent core flow•Wavy core flow

– Instability of smooth waves– Waves shortening and sharkskin– Movie of wave shortening

•Self lubrication (w/o emulsions)– Self-lubrication of bitumen froth– Self-lubrication of midway sunset crude

•Lubrication of concentrated o/w emulsions– Rheometer studies– Comparison of rheometer and pipeline

data•Lubrication of solids in liquids•Steep waves


Some Flow Types


Ideal Core-annular Flow

• Oil moves as a rigid body impelled forward by the pressure P = P1 - P2 and resisted by the shear stress in the water.

• Choose a/b to maximize the total volume flux of oil and water (o/w) for a given P.

• This problem has a solution a 0.

• You can transport very viscous oil in water more cheaply than water alone

• You get drag reductions of the order

oil / water = 1000 1051

100


Laminar and Turbulent Core-annular Flow


Steep Waves Arise from Smooth Waves


Wave Shortening and Sharkskin

Numerical calculation of BKJ (1996). Wavelength L = 13.5 - 14.1 for (IR, h) = (600, 1.4). The wavelength and amplitude tend together to zero as 1 (see JBCR 1997).


Wavy Core FlowOil flow rate fixed:10.125 gal/min.

Water flow rates: gal/min.

0.3

0.6

1.0

1.5

2.0

0.3

0.6

1.0

1.5

2.0

Oil flow rates in gal/min.

Water flow fixed:1 gal/min.


No 6 fuel oil in a 1” pipeline (#4)

4.1water

oil

U

U 826.0b

a

radiuspipe

radiuscoremean

985)1(

Re

water

bU

Flow

Stokesvwater 01.0



4.1water

oil

U

U

826.0b

a

radiuspipe

radiuscoremean

1356)1(

Re

water

bU

Flow Stokesvwater 01.0



4.1water

oil

U

U

857.0b

a

radiuspipe

radiuscoremean

680)1(

Re

water

bU

Flow Stokesvwater 01.0



4.1water

oil

U

U

952.0b

a

radiuspipe

radiuscoremean

228)1(

Re

water

bU

FlowStokesvwater 01.0


Self-Lubrication

• At a critical value of the velocity, the emulsion breaks away from the wall and self-lubricates– Self-lubrication of bitumen froth

– Self-lubrication of an emulsion of water in Midway Sunset Crude

• The formation of lubrication layers in o/w emulsions requires that the emulsion breaks and forms a lubricating layer at the wall. This is self-lubrication because water is not added. There are no papers other than the two here on this subject.

Emulsion of small water drops in oil


Self-Lubrication of Bitumen Froth

Mechanism of Self-Lubrication “Powdering the Dough”

The fouled wall is an excellent wall preparation

After the froth breaks it remains lubricated.


Tiger Waves


Tiger Waves

After a critical speeds, clay water comes out of the

bitumen froth. The clay gives the water a white color and it covers the bitumen froth with a

protective coat of clay particles, powdering the

dough.


Bitumen froth in 1” pipelineU=1.25 m/s, T=41 oC

flow



flow



flow


Blasius Correlation for Self-Lubricated Bitumen

Froth

0.01

0.1

1

10

100

1 10 100 1000 104

35-38 C41-45 C45-47 C49-52 C54-58 Cnot controlledBlasius35-47 fit49-58 fit

pres

sure

gra

dien

t,

(KP

a/m

)

U 1.75/Ro

1.25

Blasius

35-47 fit49-58 fit


R. Bai & D.D. Joseph next to the 24 in. Pipeline Pilot at the Oil Sands in Fort McMurray


SELF-LUBRICATION of an EMULSION of

WATER in MIDWAY SUNSET CRUDE

• The only other experiment on self-lubrication of oil in water emulsions were done in a 1/2-inch pipeline by Veet Kruka at SHELL HOUSTON. His results are for Midway Sunset Crude oil and are described in his patent. In this case there are no clay particles, nothing special.

• Self lubrication of w-o emulsions is of interest to other oil companies but there is no data other than Kruka’s patent and our bitumen froth. We would like to know effects of crude oil type, water fraction, pipe size, etc.


Self-Lubrication of Water in Oil Emulsion Veet Druka’s Patent -- 1/2-inch Pipeline


CRITICAL SPEED vs. VISCOSITY

• Kruka’s three data points fall on a straight line. The critical speeds for self lubrication are smaller when the viscosity is larger. Our Syncrude data does not lie on the line but it is for a 1-inch rather than 1/2-inch pipeline. We don’t know of any other published data.


Lubrication of Concentrated Emulsions

• 70% oil is unstable against inversion; stabilized with surfactants

• The viscosity reduction is a form of lubrication

Concentrated Emulsionsay 70% oil

=water volume

total volume=

3

10

3/10

1

Viscosity reduction

Shear thins

n

K


Three Commercial Lines Have Used o/w Emulsions

to Transport Oil

• Indonesia (Shell) carries 40,000 barrels/day of 70% waxy crude in 20"238 km pipeline

• California (Shell) carries 50% heavy crude in 8"13 mile pipeline

• Venezuela (Bitor) carries 70-80% heavy crude in 36"300 km pipeline

• Other oil companies are working with us to evaluate this transportation option

• The MAIN QUESTION is if, when and how o/w emulsions can be made to enter into core annular flow, giving an additional benefit.


• “Self-lubrication” of o/w emulsions involve migration of oil away and water toward the pipe wall

• Self-lubrication of w/o emulsions involve breaking the emulsion at the wall; it is altogether different

• Because the o/w emulsions shear thin, it is not easy to tell if they self-lubricate


Comparison of Rheometer and Pipeline Data

• We can use the rheometer studies giving K and n to predict pipeline data for a shear thinning fluid.– Dodge-Metzner correlations:

– Laminar flow

– Turbulent flow

Reynolds number Friction factor

22 VL

PgDf

22 VL

PgDf

1

2

8

n

nn

gK

VDR

2.12

1

75.0

4.0ln

41

nRf

nf

n


Rheometer Studies

Rheometer studies are used to get K and n for = K n

The sample may lubricate in the rheometer. If the sample lubricates you will get a different K and n when you change the distance between the plates.

Shear stress vs. shear rate- 1st fresh oil blend ( 70:30 water external ) -

= 4.40870.5662

0.1

1

10

100

1000

0.001 0.1 10 1000 100000Shear rate (s -1 )

Sh

ear

stre

ss (

Pa)


Rheometer Studies

Shear stress vs. shear rate- 1st oil blend after 1 week ( 70:30 water external ) -

= 6.65710.5168

0.1

1

10

100

1000

0.0001 0.01 1 100 10000Shear rate (s -1 )

Shea

r st

ress

(P

a)


Friction Factor vs. Reynolds Number

0.1

1

10

100

0.1 1 10 100Generalized Reynolds number

Fan

nin

g fr

icti

on f

acto

r

1st oil blend - fresh

1st oil blend - 1 week later

2nd oil blend - fresh

2nd oil blend - 4 days later

Dodge-Metzner Correlation for laminar flow

The data points are below the theory line suggesting lubrication


Lubrication of Solids in Liquids

• Lubrication occurs when particles migrate away from walls. We study this by direct numerical simulation, see www.aem.umn.edu/Solid_Liquid_Flows


Migration of Neutrally Buoyant Particles in Pressure

Driven Flow by DNS

• You can isolate and study effects by switching physics on and off in the simulations that you could not do in experiments. (a) Newtonian, (b) Generalized Newtonian with shear thinning index n=0.5, (c) viscoelastic, (d) viscoelastic with shear thinning.

Huang & Joseph JNNFM 1999


Migration of 56 Neutrally Buoyant Particles in a Pressure Driven Flow

In a generalized Newtonian fluid (n=0.5): Re=42

In a Newtonian fluid: Re=12.5

In an Oldroyd-B fluid: Re=0.156,

De=2.50, E=16, M=0.625

In an Oldroyd-B fluid with shear thinning (n=0.5): Re=0.161, De=2.57,

E=16, M=0.643

F:\faculty\joseph\archive\DDJ\1999\presentations\PwrPtMovies\56newton.mpg


Steep Waves

• Extrudate distortion• Melt fracture• Sharkskin• Rubber abrasion• Elastodynamic steep wave• Stress induced cavitation at

the nanoscale


Extruded Polymeric Film from a Slit Die


Melt FractureThese are cracks, fractures or waves on Polymer extrudate, plastics. At low rates of extrusion there is no extrudate distortion; at a critical extrusion the polymer is said to slip. I think that a layer near the wall becomes soft, a lubrication layer. You see the onset of lubrication as a break in the flow curve.

The authors do not remember which way the melt was extruded. We guess that the steep wave advances.


Sharkskin

The short waves on (b), (c) and (d) are called “sharkskin”. On them, and on the larger waves (c) through (b), the steep side advances.


Sharkskin


Rubber Abrasion

Abrasion patterns for different rubber

(a)

(b)

Steep Waves


Elastohydrodynamic Steep Waves Produced by Lubrication in Thin (nanoscale) Films

V

Mica

High p Low p

= 180 p

(Israelachivili - atomic force microstructure)


Velocity Effects

(KRCI 1994) (A-D) The effect of increasing velocity on surface deformation at constant load L. The deformation of the front edge and the separation of the two surfaces increases with increasing velocity. (D-F) At constant sliding velocity, an increased load decreases the film thickness in the gap and increases the area of contact.


Stress Induced Cavitation at the Nanoscopic Scale

Cavitation in a moving fluid is not determined by the pressure. An incompressible fluid cannot find its pressure. Look at principal axis and find the maximum tension to compare against the breaking stress (say vapor pressure). Israelachivili experiments in the atomic force apparatus show that the fluid “cracks” at a critical rate of extension. The critical speed is Uc.

They said, “We consider that in the present case, the ‘fracturing’ or ‘cracking’ of the liquid between the surfaces must be considered synonymous with the ‘nucleation’ or ‘inception’ of a vapor cavity.”

U < Uc

U Uc

U >> Uc

Documents

Syncrude/2000/presentations/lubrication1 Lubricated Transport DD Joseph, May 2000 Office of Basic Energy Sciences, Engineering, DOE Some flow types Ideal