Effect of Manufacturing Processes on Blade Throat Size and Position in a Steam Turbine Diaphragm

Abstract

Despite a sustainable energy future, steam turbines are requisite for the reliability and security of the electric power supply in many countries. Accurate and precise manufacturing of the steam path is crucial to turbine efficiency. Before entering the rotor blades, the steam must be correctly guided using stationary blading in a diaphragm. Steam turbine diaphragms are complicated components to manufacture, and welding is the most common fabrication method. A case study presented in this paper employs data from a 3D optical scanner for a geometric deviation analysis of the upper half of the diaphragm at two production steps, after complete welding and after final machining. Unrolled cylinder cross-sections at different diameters are used to evaluate the blade throat sizes and positions compared to the nominal geometry. The results indicate significant geometric changes between the two fabrication steps, and several suggestions are put forward for targeted future work.

Flutter Measurement of a Linear Turbine Blade Cascade with an Angular Position Deviation of One Blade

“…This initial research effort opened the door to a more extensive testing campaign. The intended types of position deviations will be realized according to the actual geometric errors, emphasizing the effect on the blade throat size and position [1][2][3]. In such investigations, a non-dimensional or otherwise generalizable form of the deviations and their effects will be preferred to provide information on the relative importance.…”

“…The quality of production and assembly of bladed discs is essential for the performance and safe operation of turbomachinery. However, geometric errors are unavoidable [1][2][3][4] and manufacturing and assembly imperfections may play a role in dynamic unbalance, mistuning or vibration of the bladed discs. There are two main mechanisms of blade row vibration: forced response due to blade row interaction phenomena or inflow distortion and self-excited oscillation known as flutter.…”