Internal hydrodynamics of an inspection projectile for low-pressure gas pipelines

Abstract

Speed control of an inspection projectile in low-pressure gas pipelines can be performed by changing the cross-section of the central channel when turning the flap, and it is more effective the lower the resistance to gas flow through the central channel. Peripheral bypass channels are used to reduce the resistance. We conducted analysis of gas flow in these channels with cut-outs intended to accommodate the flap turning device and brakes. A design of the channels that provides a 15% decrease in drag force is proposed (the maximum decrease in force in the design with bypasses without cut-outs is 20%). The dependence of the damper drag force on the angle of its rotation, used in controlling the movement of the inspection projectile, was also calculated. In a wide range of angles, the drag force was found to be proportional to the fraction of the overlapped area.