Friction reduction

The tenn tribology translates literally into the study of nibbing . In modem parlance this field is held to include four phenomena adhesion, friction, lubrication and wear. For the most part these are phenomena that occur between pairs of solid surfaces in contact with one another or separated by a thin fluid film. Adhesion describes the resistance to separation of two surfaces in contact to while friction describes their tendency to resist shearing. Lubrication is the phenomenon of friction reduction by the presence of a fluid (or solid) film between two surfaces. Finally, w>ear describes the irreversible damage or defonnation that occurs as a result of shearing or separation. 

Packiug may not provide a completely leak-free seal. With shaft surface speeds less than approximately 2.5 m/s (500 ft/min), the packiug may be adjusted to seal completely. However, for higher speeds some leakage is required for lubrication, friction reduction, and cooling. 

Other fields Friction reduction agents, dispersants, adhesives, fiber dressers... 

The drag reduction experiments show that the characteristics of drag reduction are the same as Habon-G solution reported earlier The amount of drag reduction stays almost the same for the first several hours. Then the amount of drag reduction falls off to zero abruptly as shown in Fig. 1. In the figure we plot the % friction reduction against sheared time, where the % friction reduction, % FR, is defined as follows ... 

Fig. 1. % Friction reduction vs. shear time for STAC solutions.

Guar Gum 1 34 3 C N.S. N.S, R Drilling fluids, spacers, friction reduction, in stimulation, fracturing and lost circulation (crosslinked guar gum gels), fluid loss additive in drilling, spacer and fracturing fluids... 

KEC 2 37 3 C N.S. N.S. RF Fluid loss additive for cementing spacers, completion and workover fluids, fracturing fluids, friction reduction in stimulation, enhanced recovery... 

Polyacrylamide (Partially Hydrolyzed) 3 34 2 IC S S RF Fluid loss additive in cementing, drilling fluids, friction reduction in fracturing, enhanced oil recovery, scale inhibitor... 

Slagel, R.C. and Bloomquist, A.E. "Friction Reduction in Flowing Hydrocarbon Fluids," US Patent 3,779,969(1973). 

Liu, J.-F. Nistorica, C. Gory, I. Skidmore, G. Mantiziba, F. M. Gnade, B. E. 2005. Layer-by-layer deposition of zirconium oxide films from aqueous solutions for friction reduction in silicon-based microelectromechanical system devices. 

Nonetheless, there can be nonnegligible atmosphere frictional reduction of the rate constant when the electrolyte concentration is sufficiently high that the coupling force magnitude is important [51] (this reduction requires GH theory for its description the zero frequency friction Kramers prediction can give an order of magnitude too large a reduction in the rate). 

FIGURE5.12 Friction reduction due to lubrication by adsorbed film (bilayer) of amphiphiles (as lubricant). 

Increase in equipment life-cycles by reducing machinery wear (frictions reduction) ... 

Fig. 9. Friction reduction effectiveness of synthetic polymers and polysaccharides during one pass through a turbulent flow rheometer (data taken from Kenis)...

Fabula AG (1971) Fire fighting benefits of polymeric friction reduction Trans ASME, J Basic Eng 453... 

Gold PI, Amar PK, Swaidan BE (1973) Friction reduction degradation in dilute polyethylene oxide) solutions J Appl Polym Sci 17 333... 

Kenis PR, Hoyt JW (1971) Friction reduction by algal and bacterial polymers J Fluid Mech 50 133... 

Kenis PR (1971) Turbulent flow friction reduction effectiveness and hydrodynamic degradation of polysaccharides and synthetic polymers J Appl Polym Sci 15 607... 

Kinnier JW (1970) A correlation between friction reduction and molecular size for the flow of dilute aqueous polyethyleneoxide solutions in pipes Thesis, Y. S. Naval Postgraduate School... 

An extended version of the hybrid technique of PIV/LIF/SIT is reported by Kitagawa et al. (2005), in which the PTV technique is employed to measure the velocity field in liquid phase and track the velocity distribution of dispersed bubbles, in addition to the SIT measurement of bubbles shape and location in a microbubble-laden turbulent channel flow. It is well known that microbubbles injected into the turbulent boundary layer developing on a solid wall have a significant skin friction reduction effect. To investigate the interactions between the injected microbubbles (the void fraction is actually low but... 

Esters stick to the surface better than mineral oils. Since ester groups are polar, they form physical bonds with metal surfaces. At high loads, esters will tend to form chemisorbed films. Under extreme boundary conditions, esters tend to break down to form acids which leads to wear protection and friction reduction (Randles, 1999). These acids readily react with freshly exposed metal surfaces to form metal carboxylates tribofilms. 

The friction reduction is from MoDTC deterioration. Other antioxidants are essential to extend friction reducing capability (Korcek et ah, 1996). 

The Case Study. Comparison of laboratory test, sequence VIA and vehicle aging tests of the SAE 5W-20 engine oil modified by MoDTC additive, [Mo] = 700 ppm. Used oil samples were analyzed for the following properties MoDTC (%) left, antioxidant (%) left, ZDDP (%) left, and friction- reduction effectiveness. The case study includes a description of ... 

Friction reduction None None Good None... 

Prolonging friction-reduction capabilities of ZDDP/MoDTC additives. One... 

In the laboratory aging procedure (Johnson and Korcek, 1991), high temperature antioxidant capabilities were assessed at 160°C in a batch reactor using blow by components to accelerate oil degradation. The sample analyzed after five hours of accelerated aging of (MoDTC + ZDDP) without MPH, had lost its ability to reduce friction coefficient to below that which would be observed for a ZDDP - only system. The five hour sample from the mixture (MoDTC + ZDDP) containing added MPH still provided substantial friction reduction and the results are very similar to those observed for the fresh mixtures, p 0.05. 

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