Team Members

Mentors

▸  Kushal S Gowda (231ME123)

▸  Nallola Harshavardhan Goud (231ME330)

▸  Nishadeep H (231ME131)

Mentees

▸  Aarav Gautam (241ME202)

▸  Anagha Tanmayee Sripathi (241MT001)

▸  Anaswara Prakashan (241MT004)

▸  Pramathesh Vishwanath (241ME341)

Introduction

Jet engine turbine blades operate under extreme conditions, including high rotational speeds, elevated gas temperatures exceeding 1000°C, and cyclic mechanical loads, making them highly susceptible to thermal fatigue, creep, and structural deformation. Accurate analysis of blade behaviour under such conditions is essential for ensuring engine reliability and service life.

This project presents a computational approach to evaluate and optimise the performance of a jet engine turbine blade using Finite Element Analysis (FEA) in ANSYS. A 3D CAD model of the turbine blade was first developed in Fusion 360, capturing the key geometric features. The geometry was subsequently optimised by rounding the bottom holding section of the root to minimise stress concentrations and scaling down the overall blade size. The optimised model was then meshed and subjected to a sequential simulation in ANSYS, a steady-state thermal analysis followed by a static structural analysis under realistic boundary conditions. A few high-temperature candidate materials were evaluated across key performance metrics, including temperature distribution, total heat flux, total deformation, equivalent elastic strain, and Von Mises stress. 

Objectives

1) Design and Modelling – Develop a precise 3D CAD model of a jet engine turbine blade with geometry optimised for reduced thermal and mechanical stress concentrations.

2) Computational Analysis – Conduct detailed thermal and structural simulations, including coupled thermo-structural analysis, in ANSYS to evaluate blade performance under simplified operating conditions.

3) Material Selection –Analyse and compare different high-temperature materials to identify the most suitable material with improved thermal and structural performance.

4) Performance Evaluation – Evaluate key parameters such as temperature distribution, stress distribution, and deformation to assess the structural behaviour of the turbine blade.

5) Optimisation – Identify the most efficient blade configuration based on simulation results to improve overall performance and structural integrity.

6) Propose design and material improvements to enhance blade service life and operational reliability in aerospace applications.

Theory

Finite Element Method (FEM)

This project uses the Finite Element Method (FEM) as its core computational framework. FEM is a numerical technique used to obtain approximate solutions to complex engineering problems governed by partial differential equations. The method works by discretising a continuous domain, in this case, the turbine blade geometry, into a finite number of smaller subdomains called elements, connected at points known as nodes. This collection of elements forms a mesh.

Within each element, the behaviour of the physical field (such as temperature or displacement) is approximated using interpolation functions known as shape functions. By assembling the governing equations for all elements, a global system of equations is formed and solved to obtain the field variables across the entire domain. The accuracy of the FEM solution improves with mesh refinement, particularly in regions of high stress or thermal gradient.

Mesh quality in this project was verified using the skewness metric, where a value of zero represents a perfect element and a value close to one indicates a highly distorted element prone to solver instability. The mesh produced in this study exhibited the majority of elements in a low skewness range, confirming high mesh quality and numerically reliable results.

Thermal Analysis

The thermal analysis was conducted as a steady-state simulation, in which the temperature distribution is solved for equilibrium conditions that is, when heat input and output are balanced, and temperatures no longer change with time. Convection boundary conditions were applied to the blade surfaces to simulate hot combustion gas flow at an operating temperature of 1200°C with a film coefficient of 8×10⁻⁴ W/mm²·°C, while a fixed temperature of 377°C was assigned to the blade root to represent the cooled rotating structure that holds the blade in practice. An initial uniform temperature of 22°C was set as the reference starting condition. The key outputs of the thermal analysis are the temperature distribution across the blade and the total heat flux, which describes the rate and direction of heat flow per unit area through the material. These results are subsequently imported into the structural solver as a thermal load.

Structural Analysis

The static structural analysis determines how the blade deforms and where stresses develop under the combined effect of thermal loading and rotational forces. A rotational velocity of 1050 rad/s was applied about the z-axis to simulate the high-speed rotation experienced during engine operation, while a fixed support was applied at the blade root faces to constrain the blade in place. The elastic behaviour of each material is characterised by its Young's Modulus (E), which defines the stiffness of a material as the ratio of applied stress to resulting strain:

E = σ / ε

Poisson's Ratio (ν) captures the ratio of lateral strain to axial strain under uniaxial loading, while the Bulk Modulus (K) describes the material's resistance to uniform volumetric compression. Together, these properties govern how each candidate material responds mechanically to the loads imposed on the blade.

The Von Mises stress criterion is used to assess the onset of yielding in the blade material. It combines the contributions of all stress components into a single equivalent stress value, which can be directly compared against the material's yield strength to determine whether plastic deformation is likely to occur.

Material Behaviour at High Temperatures

At elevated temperatures, turbine blade materials can experience creep that is time-dependent deformation under sustained stress  as well as a notable reduction in yield strength and stiffness. This makes material selection a critical aspect of turbine blade design. In this project, few candidate materials were evaluated, spanning nickel-based superalloys, ceramic matrix composites, and carbon-based composites. Material properties including Young's modulus, Poisson's ratio, thermal conductivity, and coefficient of thermal expansion were sourced from standard technical literature and research papers and entered into ANSYS for each simulation run.

Geometry and model

Initially we took the following rudimentary model of the blade to analyze. 

This design was optimised by rounding the bottom holding part (to reduce stress concentration) and scaling down the overall size.

Meshing

The meshing procedure prepares the geometry for a sequential simulation involving a steady state thermal analysis followed by a static structural analysis to evaluate heat transfer and mechanical stresses.

The computational grid was created using the mechanical physics preference in Ansys. A primary requirement for this setup was to stay within the computational limits of the Ansys Student version, which restricts the model to a maximum of 100000 nodes. To achieve the highest possible resolution without exceeding this limit, a specific body sizing control was applied to the entire geometry. The element size was precisely set to 1.585 millimeters with a soft sizing behavior. This exact sizing strategy yielded a final mesh of 99185 nodes and 66622 elements, making maximum use of the available node allowance while ensuring detailed capture of the complex root geometry and blade surfaces.

The software automatically selected a Tet10 element formulation, creating a mesh composed of ten node tetrahedrons. These higher order elements are highly suitable for conforming to the curved surfaces of the blade and the sharp internal corners of the root. To verify the quality of this generated mesh, the skewness metric must be evaluated. 

Skewness measures how much a generated element deviates from an ideal, perfectly equilateral shape. A skewness value of zero indicates a perfect element, while a value close to one represents a highly distorted element that could cause calculation errors, poor interpolation, or solver instability.

The mesh metrics histogram for the generated grid shows an excellent distribution of element quality. The vast majority of the elements have very low skewness values, with the largest concentrations falling between the 0.12 and 0.38 marks on the metric axis. There are very few elements approaching the higher, undesirable end of the scale. This low average skewness confirms that the mesh is of high quality and will provide stable, reliable mathematical results when the thermal boundary conditions, fixed supports, and rotational velocities are applied in the solver phases.

Boundary conditions

The boundary conditions for the thermal analysis are as follows.

Initial temperature:

Convection:

Hot air and gases are assumed to flow over the highlighted surfaces of this blade. Operating temperature is taken as 12000C.

Fixed temperature:

We assumed that the bottom of the blade is at constant temperature to simplify the analysis. In practice, the blade is held inside a cooled rotating structure.

The boundary conditions for static structural analysis are as follows.

Rotational velocity:

Fixed support:

In a coupled static thermal-structural analysis, the structural solver automatically imports the thermal load from the results of the thermal solution. This load differs for each material.

Materials

Material properties were found from standard papers and websites. They are tabulated as follows. 

Results

Carbon-carbon composites were found to have the best responses to loads.

Temperature:

Total Heat Flux:

Thermal Error:

Total Deformation:

Equivalent Stress:

Equivalent Strain:

References

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