Анализ причин низкой экономичности цилиндра низкого давления паровой турбины К-200-130

Abstract

Designing a low-pressure cylinder (LPC) with a one-and-a-half steam exhaust from it is the only way in which a larger steam flowrate can be passed to a condensing steam turbine’s condenser without increasing the length of the turbine last-stage blades. For implementing this idea, K. Baumann has developed a special next-to-last two-tier stage, which diverts part of the steam passing through the stage’s upper tier directly into the condenser in bypass of the last-stage bucket. In the former Soviet Union, this solution was implemented in a number of medium- and high-pressure turbines, as well as in the K-200-130 turbine produced by the Leningrad Metal Works (LMZ). However, field experience gained from operation of this turbine, as well as special investigations, showed that the LPC fitted with the Baumann stage had poor efficiency, and during the subsequent modernizations the Baumann stage was removed from the K-200-130 turbine’s LPC flow path. Factors that have caused dramatic degradation of the cylinder efficiency are analyzed. It is shown that the factors relating directly to the Bauman stage that were considered in the scientific literature could not play the key role in degrading the stage efficiency and, accordingly, in affecting the cylinder efficiency. It has been shown from the performed analysis that poor efficiency of the LPC equipped with the Baumann stage is not due to the stage itself, but due to the conditions of steam admission to it and to the K-200-130 LMZ turbine last stage. As a result, two out of four (in total) stages contained in this cylinder operate with dramatically degraded efficiency. These design drawbacks removed, the Baumann stage can well be used to increase the maximum possible steam passage through the LPC.