Performance analysis of a new LP stage located upstream of the extraction point in a 225 MW turbine

A new design of steam turbine stages upstream an extraction point is presented. In this solution a special ring guides the steam leakage flow directly to the heat exchanger. The experiments and calculations have confirmed advantages of the new design as manifested by turbine operating features and efficiency. The design has been applied in 30 old turbines with Baumann stages. Recently, the patent was used in the LP exit ND-41A of modernised 225 MW turbines in the Polaniec and Kozienice power plants.