The prediction of relaxation effects in the hydrocarbon working environments by high pressures

The paper considers the rheology of hydrocarbon working environments of hydraulic systems. The authors describe relaxation processes of working liquids of hydraulic high presser actuators. It is analyzed the dependence of the rheological properties such as viscosity, density and relaxation processes on structure of molecular chains of hydrocarbon compounds. It is showed the results of calculation of changing the rheological properties of isomers of hexane and octane by high pressures. The experiment confirms the significant differences of viscosity and density for isomers of the test substances. It is identified the values of the Van der Waals volumes, the Van der Waals surface areas and the length of the molecular chains of isomers structures and identified the dependents of these values on high pressure. The calculation of the Van der Waals volumes and the Van der Waals surface areas is based on the increment method. It is analyzed the profile of changing the Van der Waals volumes and the Van der Waals surface areas of isomers of the test substances. It is also analyzed the influence of the Van der Waals forces on the relaxation processes of the molecular chains which define the profile of these dependence. The method for the calculation of the strain of molecular chains in the mechanical force fields is offered, this method allows in case of deformation of the test substances solving the changing of the length of the molecular chains and the changing of the length of the intermolecular spaces. It is introduced the assumptions which make simplify the mathematical apparatus of the basic model - the Doi-Edwards model. The method developed by the authors makes simplify greatly the calculation of the strain of molecular chains, but maintains high accuracy of the solver results. It is identified the profile of relaxation of the molecular chains of isomers and confirmed the significant dependence of relaxation processes on the structures of carbon chains.