Development and research of efficiency of a new low-pressure turbine with one and a half exhaust based on forked two-tier blades

Abstract

The maximum power of single-flow 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. It is this path that is currently being intensively used in the world turbomachinery industry. As a result, over the past decades, the blade lengths of the last stages of condensing steam turbines have increased from 1200 mm to 1500 mm. The presented materials consider an alternative solution based on the Bauman stage. This method was used in steam turbines until the middle of the twentieth century and was rejected due to the very low efficiency of such LPCs. It is shown that such a decision was made without a proper analysis of the reasons for the low efficiency of cylinders with Bauman stages. Elimination of these reasons will allow creating a low-pressure cylinder with one and a half exhaust steam, the efficiency of which may be higher than the efficiency of a modern low-pressure cylinder made on the basis of the last stage rotor blades with a length of 1400-1500 mm. When developing a new low-pressure cylinder with one and a half steam exhaust, two-tier stages were considered as stages made on the basis of two-tier fork blades, which made it possible to sharply reduce losses from the fan, and nozzle diaphragm of these stages were equipped with upstream distribution grids, which ensured a uniform distribution of steam flow rates over all sections of the two-tier stages.