14th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
The maximum power of single-row steam turbines is determined by the amount of steam that can be passed through its last stage. With a fixed length of the blades of this stage, the passage of steam into the condenser can be increased by increasing the number of steam flows. Structurally, this problem is solved by using double-flow low-pressure cylinders (LPC) and increasing the number of LPCs while increasing the length of the blades at the level of the steps.It is this path that is currently intensively used in the world turbomachinery. As a result, over the past decades, the lengths of the blades of the last stages of condensing steam turbines have increased from 1200 mm to 1500 mm. The materials presented consider an alternative solution based on the Bauman stage. The indicated method was used in steam turbines until the mid-twentieth century and was rejected due to the very low efficiency of such low-pressure cylinders. It is shown that such a decision was made without proper analysis of the reasons for the low efficiency of cylinders with Bauman stages, the elimination of which allows one to create a low-pressure cylinder with one and a half exhaust steam of efficiency which can be higher than the efficiency of modern low-pressure cylinder, made on the basis of rotor blades of the last stage with a length of 1400-1500 mm. When developing a new low-pressure cylinder with one and a half steam exhaust, two-tier steps were considered as steps made on the basis of two-tier fork blades, which made it possible to sharply reduce losses from the fan, and nozzle apparatuses of these stages were equipped with pre-switched distribution grids, which ensured a uniform distribution of steam flow rates over all sections of the two-tier stages.