Aperiodic Instability of a Once-Through Steam Generator with a Feedwater Line

Aperiodic (static) flow instability is an instability related to the change of a flow direction in individual steam generating U-shaped channels operating at given pressure difference. The nature of an aperiodic instability is close to a Ledinegg instability [1] related to the presence of multiple flows at the full hydraulic curve of a U-shaped channel. In this paper, the conditions for a reverse flow for a once-through steam generator (OTSG) with U-shaped modular feedwater line (MFL) are studied. From the results of the studies, it is revealed that the change of a flow direction in the MFL is due to the boiling of the feedwater in the downcomer branch of the U-shaped MFL and that multiple flows start in an area of the extremes corresponding to the minimum pressure difference of the hydraulic curves. Calculation models for predicting a threshold of an aperiodic instability for the OTSG of interest is proposed and the analysis results are compared with the experimental data.

Some Peculiaritiers of the Relativistic Electron-Positron Plasma Dynamics in the Pulsar Magnetosphere

Some aspects of relativistic electron-positron plasma dynamics in the pulsar magnetosphere are discussed. Namely it is shown that if we take into account the influence of centrifugal force, this gives rise to the new dynamical effect of plasma particle radial braking in the pulsar magnetosphere. Also the possibility of aperiodic instability development in the pulsar magnetosphere is demonstrated. The mechanism for the toroidal magnetic field generation is proposed. Besides, the possible changes of the pulsar magnetosphere structure caused by above mentioned processes is considered.