Abstract: As tubular turbine power generation technology develops, wider application is found in industries to recover the residual pressure energy of circulating water systems. This paper combines the 1D method of characteristics (MOC) and the 3D computational fluid dynamics (CFD) method to develop a coupling method for simulating the flows in a pipeline network equipped with a tubular turbine. We focus on the simulations of the runaway process in the real system and an analysis of its flow and runner stress characteristics. The results show that the time required to switch from the steady state to the runaway state shortens as the moment of inertia decreases. For the pressure fluctuations at the monitoring points in the runner and draft tube sections, their amplitudes take greater values at the runner blade frequency and its higher harmonics. During runaway, the axial force on the runner decreases greatly, while the radial force increases greatly and oscillates violently; an evident alternating trend appears in the blade surface pressure, and a negative pressure zone occurs near the blade edge on its inlet side. And large vortices develop gradually in the draft tube and diffuse towards the pipe wall along the main flow.

Key words: tubular turbine, residual pressure, coupling simulation method, runaway, flow characteristic, runner stress