Modal Analysis of Conventional Gas Turbine Blade Materials (Udimet 500 and IN738) For Industrial Applications

Abstract

Finite element method (FEM) was utilized to determine the natural frequency of two turbine blade materials applicable to Trans-amadi power plant in Port Harcourt, Nigeria. Comparing the two gas turbine blade materials, the fundamental frequency under the same load condition was 751Hz for IN 738 and 896Hz for U500 turbine blade material. This implies that the natural frequencies obtained for both materials were much higher than the operational frequency of 85Hz for resonance to occur. Therefore, resonance would be delayed across the blade materials in service condition, indicating that gas turbine blades designed with both materials would be dynamically stable under operational frequency approaching 745Hz. It was observed that U500 gas turbine blade material which had a higher fundamental frequency has a better mechanical properties that can undergo a longer service condition in extreme working phase before failure compared to IN 738 material. This justification was deduced from the difference between the operational frequency and the fundamental frequency; as the closer the value obtained for fundamental frequency to the operational frequency, the higher the possibility of failure and vice versa. To avoid unforeseen failure and downtime in service operation, vibration test should be conducted on routine schedule in order to meet the expected performance of the gas turbine blade.