INVESTIGATION OF GAS-DYNAMIC PROCESSES IN PIPELINE COMMUNICATIONS DURING THEIR TRENCHLESS RECONSTRUCTION WITH THE TECHNOLOGY "TRACTION PISTON"

Abstract

The technology of the trenchless reconstruction of pipeline communications "Traction Piston", which consists in running a new polyethylene pipeline into a steel one worn by pigis described. At the same time, in order to maintain the necessary pressure in the cavity, the space between the new polyethylene pipeline and the worn steel one is sealed.
 A 3D modeling of the annulus and space behind the piston, where the complex turbulent flow of air flows, is carried out. A CFD modeling of gas-dynamic processes in the annulus and space behind the piston while laying a worn steel pipeline with a polyethylene pipeline in the ANSYS Fluent software system is performed. The mathematical model is based on the solution of the Navier-Stokes equations and the continuity of the flow closed by a two-parameter turbulence model of Launder-Sharma with the use of a wall function with corresponding initial and boundary conditions. A dynamic grid model was used to simulate the motion of the piston and the polyethylene pipeline. The type of adjustment of the dynamic grid parameters during the stroke of a new polyethylene pipeline into a defective steel one – Layering was chosen.
 The simulation results were visualized in the postprocessor of the software complex by constructing flow lines, velocity vectors, pressure fields on the contours and in the longitudinal section of the annulus and space behind the piston. The exact values of velocity, pressure at different points between the annulus and space behind the piston were determined. The structure of the air flow in the cavity and interstitial space is studied. The places of slowdown and acceleration of air flow, falling and increase of pressure are found. The loss of pressure in the annular space is determined.