The improvement of the operational efficiency of a two-stage ejector unit for steam-turbine condenser vacuuming systems

Liquid-gas ejectors are widely used in steam-turbine condenser vacuuming systems of power units installed in state district power plants in Russia and the CIS countries. Such a wide distribution of these jet devices is explained by their simple design, which makes them technologically advanced and cheap to manufacture. During operation they require almost no significant maintenance. However, the development and implementation of liquid-gas ejectors are associated with the need to optimize use plans and complex calculations of the geometric and operating parameters of the ejector and the vacuum system for the initial data of each specific project. Besides, energy efficiency is a key design requirement for ejectors operating continuously and consuming a lot of active water. This article proposes a set of technical measures to reduce the power spent on vacuuming the steam space of a steam turbine. The proposed set of measures includes: the use of a two-stage unit with a first-stage liquid-gas ejector and a second-stage ejector, in which the active medium is water and the passive medium is a liquid-gas mixture; an improved hydraulic circuit diagram for feeding the unit with one pump; calculation of the optimal pressure at the first-stage outlet corresponding to the maximum efficiency of the unit. To calculate the optimal pressure at the second-stage inlet, an equation was obtained for the dependence of the consumed power of the two-stage vacuum unit on the second-stage suction pressure. It is shown that the obtained dependence has an extremum, which corresponds to the second-stage suction pressure, ensuring the minimum consumed power.