Inertial Method of Viscosity Measurement of the Complex Rheology Medium

Abstract

Modern lubricants have a complex content and complex rheological properties: the viscosity of oils depends on the shear rate, pressure and temperature. Strange as it is, the complication of the rheological properties of the studied medium requires the simplification of thermomechanical testing conditions. It is due to the necessity of development of the homogeneous distribution of the thermomechanical values and the flow conditions with the known type of the stress-strain state. The authors offer a theoretical justification of a new method of the viscosity measurement of the complex rheology medium which combines the advantages of known rotational and capillary methods. The medium under study moves in the torus-shaped channel under the influence of the inertial forces, during this movement the friction torque is measured and the viscosity is calculated. The problem of a non-stationary and non-isothermal movement of the complex rheology medium in the torus-shaped channel has been studied. Based on the similarity theory and the analysis of the equability of the dimensions, the conditions were determined, under which the strain rate tensor has the simplest form, on the surface of the torus the distributions of the thermomechanical values are homogeneous, and pressure and temperature are homogeneous across the whole object. Based on the movement equation projected on one of the axis in the toroidal coordinates, the method of viscosity calculation was developed. Moreover, the prototype of the test rig and the data acquisition and measurement system were developed which allow to apply the automated experimental study on the subject.