The Use of Air-Measured Profile Data for Application in a High Pressure Steam Turbine

Abstract

This paper investigates the validity of the current industrial procedure of measuring optimized blade profiles in a wind tunnel under air condition although they are applied in a steam turbine. Therefore, it is important to analyze the possibility of using air-measured profile data for optimizing steam turbine blades. To this end, experimental data is collected using the cylindrical datum blade of a steam turbine in a three-stage high pressure steam turbine and in an annular air cascade wind tunnel. Three-dimensional CFD simulations are separately performed for both setups and show a good agreement with the experimental data. The numerical simulations can therefore be assumed to represent the real flow conditions. Firstly, for analyzing aerodynamic transferability, two optimized profiles are measured in the annular air cascade wind tunnel at Reynolds number of 6 × 105. These profile sections are designed for high and intermediate pressure applications by employing an optimizer. The optimization is performed with the focus on reducing the profile loss for steam conditions. The experimental data verifies that the losses of the optimized profiles are reduced significantly compared to the datum blade profile measured in the same air rig. Secondly, the air-measured optimized blade profiles are used to design a 3D-optimized blade. In a numerical investigation, this optimized blade is analyzed in the steam turbine by applying steam conditions. The outlet Reynolds number of the 2nd stage is 8 × 105. This configuration is compared with the numerical results of the datum blade profile simulations. The relative isentropic total-to-total efficiency is increased by 0.6% due to the use of the optimized rotor blades. The benefit persists also for a maximum outlet Reynolds number of 9 × 106.