Аннотация:It is well known that a helicity is one of the main factors in magnetic field self-generation. The helicity of a flow is generated by such called "divertors" inside a channel in Perm dynamo experiment. The flow of a liquid metal itself is developed when a rotating toroidal channel is suddenly broken. In a generated helical flow the dynamo action is reportedly possible. But it is supposed that a flow becomes helical and turbulent in a whole toroidal channel. In a presentation we show that an MHD dynamo is also possible at least theoretically even when a helicity is propagated only partly in a laminar flow in the channel. Magnetic Reynolds thresholds will be calculated for a range of hydrodynamical Reynolds of a flow beyond a divertor. Distributions of a velocity and a magnetic field will be shown also for a saturated regime when growing magnetic field influences on a flow backwards.