| Popis: |
While carrying out researches in a pipeline model (3.5 m length and 0.016 m in diameter)it has been found that in the dependenceQ = f (ΔP) a bending, which can serve as a sign of a possiblefailure of hydraulic flow stability, occurs in stationary flow characteristics at a kerosene concentration above30% when pumping high-viscosity, paraffinic oils with kerosene additives.The analyzes have shown that on the basis of the Reynolds criterion for both viscous and viscouselastic models, it is not possible to determine violations of the laminar regime, i.e. loss of stability of astationary flow.Rheological studies have shown that the noted systems are characterized by relaxation, i.e. viscoelastic properties. Thus, the data of viscosimetric studies, the results of which have been processed accordingto the Cross method, made it possible to determine the availability of linear viscoelasticity in these systemsconfirmed by the strict linearity of the dependences in the coordinates ( ) 22 = 1 f τη. This interpretation inthe case of linear viscoelasticity made it possible to determine the relaxation time parameter (θ ), which fora system with a solvent content of 36, 43, 54, 66 and 72% was 0.074, respectively; 0.061; 0.050; 0.041 and0.029 s.The article makes an attempt to generalize the results of studies of the hydraulic characteristics ofrheological complex fluids described by the Maxwellian viscoelastic model based on the analysis ofsignificant experimental data.A diagnostic criterion has been proposed in the hydraulic calculation of pipelines for taking intoaccount the relaxation properties of pumped multiphase systems. |
