The Influence of Air Inleakages on the Dynamic Characteristics of the Steam Turbine Unit Condenser‒Ejector System

Abstract

The results obtained from experimental investigations of the dynamic characteristics of a condenser and new ejector are presented. The investigations were carried out at a thermal power plant under the turbine commercial operation conditions using an extended arrangement for measuring the ejector operation parameters and an automated data-acquisition system. The dependences of the ejector’s first stage suction pressure on the dry (atmospheric) air flowrate and the pressure in the condenser and in the ejector’s first stage receiving chamber on the steam–air mixture flowrate during their joint operation are obtained. It is proposed to determine the maximal volumetric throughput of the ejector operating on dry air with using the minimal slope factor as a function of the air flowrate. With an increase of air inleakages into the steam turbine unit vacuum chamber, the pressure difference at the initial and total air inleakages at the ejector suction varies according to a linear law and that in the condenser according to an exponential law. By using the measurement system, the condenser’s and ejector’s dynamic characteristics were determined. It has been found that the pressure growth rate at the ejector suction increases with increasing the amount of air admitted into the condenser. The time taken for the pressure to become stable remains approximately the same. However, the pressure growth rate in the condenser does not depend on the amount of air admitted, and the time taken for the pressure to become stable increases exponentially with increasing the amount of air admitted. For diagnosing the vacuum system malfunctions in controlling the steam turbine unit’s operation mode, it is recommended to provide indication of the ejector suction pressure on the turbine control board. As regards the pressure sensor, it is proposed to install it on the common pipeline supplying steam–air mixture to the ejectors. The investigation of the condenser–ejector system dynamic characteristics will make it possible to improve the turbine vacuum protection, which is one of the turbine protection system components.