Shaft labyrinth seal clearance effect in one and half steam turbine stage with various reactions Free

This contribution deals with an experimental study of an influence of a purge flow caused by a shaft labyrinth seal in combination with various reaction of a steam turbine stage. Effects of degree of reaction on shrouded rotor sealing flow are also discussed. The experimental work was performed in VZLU air test turbine and it belongs to a long term cooperation with Doosan Škoda Power (DSPW). The configuration of the VZLU air test turbine simulated real drum-stage geometry of DSPW. The stage was consisted of the first stator equipped with labyrinth sealing, shrouded rotor and the second stator, equipped with the labyrinth sealing as well. The first stator labyrinth sealing configuration was variable to simulate small, commonly used and extremely large clearances. There were three stage reactions tested during the investigation. The change of the reaction was reached by three different rotor geometries testing; both stators were kept the same in all cases. The influence of the clearance in the labyrinth was studied by overall measurement of the stage characteristics and also by detailed flow field measurement at the rotor and second stator outlet. Four-hole wedge pressure probes were used for the detailed time averaged measurement as well as a fast response pressure probe for an unsteady measurement.