Article Archive

Crude Oil Pour Point Reduction And Rent Reduction Transportation Technology (Part 6)
3. Action principle of crude oil drag reducer
(1) Toms' pseudoplastic hypothesis
Polymer drag reducer solution has pseudoplasticity, that is, the shear rate is inversely proportional to the apparent viscosity. With the increase of shear rate, the apparent viscosity decreases, resulting in the decrease of resistance.
(2) Virk's effective slip hypothesis
When the fluid flows in turbulent flow in the pipe, the layer of fluid close to the wall is the viscous bottom layer, followed by the elastic layer, and the center is the turbulent core.
It is found that the velocity distribution in the turbulent core region of drag reducer solution is larger than that of pure solvent, but the velocity distribution law is the same, and the velocity gradient of elastic layer increases, resulting in the decrease of resistance.
(3) Viscoelastic hypothesis
The viscoelastic hypothesis suggests that the drag reduction effect of polymer solution is the result of the interaction between solution viscoelasticity and turbulent vortex. Part of the kinetic energy of turbulent vortex is absorbed by polymer molecules and stored in the form of elastic properties, so as to reduce the kinetic energy of vortex and achieve the effect of drag reduction.
(4) Turbulence suppression hypothesis
The turbulence retention inhibition hypothesis holds that after the drag reducer is added to the pipeline, the drag reducer relies on its own viscoelasticity and the molecular long chain stretches naturally along the flow, and its micro elements directly affect the movement of fluid micro elements. The radial force from the fluid micro element distorts and rotates the drag reducer micro element. The intermolecular gravity of drag reducer resists the above forces and reacts on the fluid micro elements, changing the size and direction of the force of the fluid micro elements, so that part of the radial force is transformed into the axial force along the flow direction, so as to reduce the consumption of reactive work and reduce the friction loss macroscopically. That is, polymer molecules inhibit the generation of turbulent vortices, so as to reduce the pulsation intensity and finally reduce the energy loss.
Based on the above hypothesis, it can be considered that the drag reducer added to the oil flow depends on its own characteristics
Viscoelastic, macromolecular chains naturally stretch along the flow direction, and this orientation will affect the flow
Physical point movement. The radial force of fluid particles distorts and rotates the drag reducer molecules. The drag reducing agent molecules rely on the mutual attraction between molecules to resist the force of fluid particles, change the action direction and size of fluid particles, and convert part of the radial force for reactive work into the axial force along the flow direction, so as to reduce the consumption of reactive work, and macroscopically reduce the friction loss of fluid, that is, play the role of drag reduction.