Validation of a Computational Method for the Calculation of the Flow in the Exhaust of a Low- Pressure Steam Turbine

This study presents the validation of a computational method for predicting flow characteristics in the exhaust of a low-pressure steam turbine, with specific focus on modeling the last stage and exhaust hood as an integrated system. Using the ANSYS CFX solver, numerical simulations were carried out on both a one-passage model and a full-geometry model, including variations in tip clearance, mesh density, and interface treatment. Experimental data from a scaled turbine model at ITSM Stuttgart were used for validation. The study investigates the influence of rotor tip clearance, mesh refinement strategies, and circumferential non-uniformities on diffuser and exhaust hood performance. Simulation results were benchmarked against measurements under different operating conditions—part load, design, and overload. After validating the computational method, it was applied to a Siemens-type single side exhaust hood to evaluate performance and identify loss mechanisms. The findings support the feasibility of the Last Stage Modeling (LSM) approach and offer optimization insights for future low-pressure steam turbine designs.