Material Selection and Thermomechanical Performance Evaluation of Gas Turbine Blades using FEA

Blades in gas turbines should be capable of operating under severe thermomechanical loads, like high rotation speeds, high pressure and centrifugal loads, high axial loads, high tangential loads and may lead to undue stress, deformation and premature failures unless the appropriate materials are employed. The presented study presents a systematic thermo-mechanical study of five possible materials i.e., aluminium alloy, grey cast iron, magnesium alloy, stainless steel, and titanium alloy - using three-dimensional finite element method. The ANSYS was used to model and analyse a blade geometry using quadratic tetrahedra elements (SOLID187) based on patents. The final mesh consisted of 2974 nodes and 1405 elements and 1.13 was the difference in the stress which provided the convergence of the mesh. Mechanical loading (axial 16 N, tangential 995 N and centrifugal 39, 000 N at 8 000 rpm) was added and centrifugal loading was also adjusted to 80 to 120 percent. Constant thermal gradient was also used at 1030 o C (1680 o C surface of the blade and 650 o C root) too. In nominal loading, optimized von Mises stress of stainless steel and titanium alloy were 510.66 Mpa and 426.34 Mpa respectively. The safety factor of titanium and stainless steel was 39,000 N (1.947) and 39,000 N (1.175), which was structurally unsafe of aluminium (0.965), magnesium (0.616) and cast iron (0.504). Its safety factor at full load of 120 percent was 1.708. According to the thermo stress analysis, the lowest experimental thermally induced stress of titanium alloy (1543 Mpa) was lower than stainless steel (4566 Mpa). The main input of the work is the structural and thermal performance of the most common engineering materials used when subjected to varying centrifugal forces to 120 percent of working conditions with mesh convergence and analytical confirmation (2.98 percent error). These findings make titanium alloy the material that is most structurally stable as it possesses the highest strength to mass ratio, containment of deformation and thermal indifference. The suggested methodology provides a rationalized computational model of selecting the turbine blade material, preliminary design check, and, later optimization of the high-speed rotating parts production using the CAD/CAM.