Quality indicator of the main group of steam jet ejectors of a steam turbine

The article presents an analysis of the influence of ejector characteristics and their number on the vacuum in the steam turbine condenser. An analysis of industrial test results for 12 ejector groups of various steam turbine units (STUs) was conducted. Based on this analysis, a new quantity — the ejector group quality indicator K_eg — was introduced, which depends on the volumetric and mass flow rates of the ejector group, as well as the amount of air leakage into the vacuum system of the condensing unit. A linear relationship was identified between the ejector group quality indicator K_eg and the relative pressure increase in the condenser δP. The coefficients of the approximating linear equation relating the ejector group quality indicator K_eg to the relative pressure increase in the condenser δP were calculated. It was established that at values of K_eg ≈ 2.8 or higher, the pressure in the condenser does not depend on the number of operating ejectors. The ejector group quality indicator K_eg was calculated for 33 different operating ejector groups of STUs with factory characteristics under conditions of normal and threefold excess air leakage. It was found that under normal air leakage conditions, about 94% of ejector groups have a K_eg value greater than 2.8, indicating a high performance margin. It was shown that when air leakage exceeds the normal value by three times, about 78% of the considered STUs fall into the region with K_eg below 2.8. A method is proposed for assessing the technical condition of an ejector without experimental determination of its characteristics on dry air, using the equations of the approximating linear equation relating the ejector group quality indicator K_eg to the relative pressure increase in the condenser δP.

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