Determination and Comparison of Modal Parameters of a High Lifting Low Pressure Turbine Blade Under Ni-Based Superalloys Using Computational Modal Analysis

Abstract

Low-pressure turbine (LPT) is the last stage in a gas turbine engine where energy remnants are extracted from the exhaust air. The blade profile of an LPT is designed with a high camber to generate maximum lift from the upstream flow at a low Reynold's number. Such highly cambered blades are called high lifting blades. Airflow over a highly cambered blade maximizes boundary layer separation on the suction side of the blade, thereby resulting in vortex shedding which subsequently generates blade vibrations. These vibrations can be detrimental to the blade's fatigue life due to resonance. So, selecting a strong material for the blade is important and this can be done through modal analysis. This paper aims to investigate the modal parameters (natural frequencies, amplitudes and mode shapes) of a high lifting T106 blade under Nickel-based superalloys U-500, IN-738 and Mar-M246 using Euler-Bernoulli beam theory and validation of results through computational modal analysis. For each turbine material, parameters such as blade mass, natural frequency and maximum amplitude will be obtained, validated and compared and the most suitable material for a high lifting T106 blade will be proposed based on these results.