Investigation of the influence of the gas pipeline tee geometry on hydraulic energy loss of gas pipeline systems

CFD simulation investigated turbulent flows in equal gas pipeline tees, in which the gas flow completely moves from the main line to the branch. The study was performed for tees of different geometry – stamped with different bending radii of the transition from the branch to the main line and weld, where the main line and branch connection is made at right angles. The outer diameter of the tees varied from 219 mm to 1,420 mm, the bending radius of the transition from the branch to the main line from the minimum permissible to the maximum possible, the pressure in the gas pipeline at the tee location from 3 MPa to 7 MPa. The mathematical model is based on the solution of the Navier-Stokes and energy transfer equations closed by a two-parameter high-Reynolds k – e Launder-Sharma turbulence model. To describe the processes occurring at the wall, the wall function was used. It was found that the bending of the transition from the branch to the main line, the increase in the bending radius lead to a decrease in the intensity of flow separation at the bending point and a decrease in turbulence kinetic energy in recirculation areas. The velocity field of the gas flow after it moves from the main line to the branch becomes more uniform. All this greatly affects the magnitude of hydraulic energy loss of the gas flow in the tees. In this case, the greatest energy losses were observed in the tees located at the lowest pressure points in the gas pipeline system. An analysis of the results showed that if the ratio of the bending radius of the main line and branch connection to the outer diameter is more than 0.25, then the influence of such a tee on the energy loss of the gas pipeline system is minimal. Local resistance coefficients of equal gas pipeline tees are calculated and the resulting equation for their calculation will be useful for specialists designing gas pipeline systems