An Investigation of Transient Thermal Analysis of 1st Stage Gas Turbine Blade Manufactured by Directional Solidification and Mechanically Alloyed Nickel-Based Superalloys

Abstract

The turbine rotor blades of a gas turbine engine are designed for operation at elevated temperatures, particularly first stage gas turbine blades. During operation, the turbine blades are subjected to high temperatures and large centrifugal forces. In addition to these, the temperature variations occur at start-up and shutdown cycles of the engine. Due to sudden changes in temperature, transient thermal effects are sighted and time-dependent temperature gradients appear. The estimates of the thermal variations sighted on the turbine blade at various operational speeds of the gas turbine rotor are important in determining the fatigue life. The thermal condition during the startup sequence initiated is considered as a major factor in determining the rotor maintenance interval and individual rotor component life. This work has primarily focused on transient thermal stresses arising in the rotor blade by using Finite Element Analysis. Nowadays, the thermal stresses of the gas turbine parts are determined by user defined software’s that is based on numerical methods which are being used significantly. A typical turbine rotor blade has been modeled by using CATIA V5R21. Turbine blades are made of Nickel-based superalloys have been selected for transient thermal analysis by using ANSYS 15.0. Comparative analysis has also been carried out to determine the suitability and strength of turbine blade material under the same operating conditions. Two blade materials such as IN 792 DS and IN 754 MA have been selected for comparative analysis and these blades were manufactured by Directional solidification and mechanical alloying methods respectively. The physical and mechanical properties are updated to the model and appropriate boundary conditions are applied. Thermal stresses are evaluated for both materials and the results have been compared with IN 738 LC. Static analysis has also been carryout out to examine the structural performance of the alloys. It has been observed that maximum stress and strain are sighted near the root of the turbine blade. The temperature gradients sighted on the turbine blade during acceleration and decelerations are below the melting temperature of the blade materials. It has been noticed that the transient thermal stresses are higher than the steady state thermal stresses. It has been observed that IN 792 DS has better physical and thermo mechanical properties that can withstand higher turbine inlet temperatures and could be suitable material for the manufacturing of turbine blade at Marine and Related Environments.