Усовершенствованная математическая модель динамики уровня жидкости в барабан-ном парогенераторе как объекте управления

Abstract

The features of mathematical modeling of the dynamic properties of the level of a steam-water mixture in a drum-type steam generator are considered. It is shown that boiling up of the steam-water mixture level in the drum-type steam generator, which is extremely unfavorable for automatic control system, is a consequence of occurrence of complex thermophysical processes and design features of the technological section. Therefore it is not appropriate to use mathematical models for modeling the level dynamics which do not take into account the effect of the accumulating and throttling properties of the steam line on the saturated vapor flow from the steam generator and the main disturbing action (steam consumption) is considered as an independent variable. The article proposes a linear mathematical model of the power supply section of the drum-type steam generator which takes into account the dynamic properties of the steam line connecting the steam generator with a consumer. The structural scheme analysis of the proposed mathematical model showed that between the drum-type steam generator and the steam line there is an inverse relationship with steam consumption. The negative nature of this connection explains the self-leveling associated with a change in the position of the steam flow control valve of heat generation in the combustion chamber. Accordingly, a change in the flow area of the turbine control valve, without changing the heat release by the heat load regulator in a combustion chamber or a nuclear reactor leads to a temporary change in steam consumption. This leads to less intense boiling up of the level and its transition to a new steady-state value. The level stabilization occurs below the initial value due to a brief disruption of the balance between the feed water supply to the steam generator and the steam extraction. Identified, as a result of solving the system of differential equations, peculiarities of the behavior of the steam- water mixture level make it possible to simulate more adequately the operation of existing and prospective power control systems for drum-type steam generators.