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Transcript
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MOTIVATION
INTRODUCTION
PROBLEM STATEMENT
- A 4-stage mini axial contra-rotating compressor
- Driven by contra-rotaing gearbox
- Innovative
- Challenging Problem
- Furthering Project
- Primarily focus on aerodynamic design
- Less work on Mechanical Integrity
- Structural Analysis
- Static Stress Analysis
- Vibrational Analysis
- Fatigue Analysis
- Investigate reasons of blade failure
- Suggest appropriate changes
Blade Specifications
Geometry
Material
- Chord Length-3 cm
- Span- 3.2 cm
- Tip Clearance- 0.96 mm
- Maximum thickness at 13% the cord length
- Uneven numbers of blades in consecutive rotors
- Accura-60
- Specific gravity-1.21 gm/cm^3
- Tensile modulus-2690 MPa
- Ultimate Tensile Strength-58 MPa
- Melting Point ~433 K
- Solid-State Stereolithography
NUMERICAL METHOD
Algorithm
Results
METHODS
- Maximum static stress was found at Leading Edge of the blade attachment region
- An airfoil is divided into 60 small areas using airfoil coordinates
- These areas varies from hub to tip w.r.t. radius
- Each area function was interpolated using interp1 (MATLAB function)
- 3-coupled differential equations can be solved using ode45 function
- Boundary conditions
FUTURE WORK TIMELINE
Numerical MODEL
- Developed using basic elasticity equations
- Cauchy Stress Tensor
Results
3D- Elastic Boundary Value Problem
FEM
- Only centrifugal and gravity loads were considered
- Maximum Tensile Strength vs Rotational Speed and Displacement vs Rotational Speed
- Problem formulation
- Solve differential equations using FEM
- Displacement Equation
Standard Blade Model: Beam Analysis
- Solution of coupled equations
- Selection of continuum body followed by displacement model
- Derive the stiffness and global load vector
- Force-displacement and stress-strain relationships helps in calculating unknown values
- Faster calculations with accurate prediction
3D-Photoelastic Model
- Experimental technique for stress and strain analysis
- Heat the object till stress-annealing temperature while loading a dead load
- Cool slowly with the weights still applied
- The elastic state of stress remains fixed in the model together with the deformation
- Slice the object normally to the surface and measure isochromatic fringe order with secondary principal differenece
- Subslice the above part normally and do the same
- Sublice the above part parallel to the the surface and measure the angle of principal stress w.r.t. either of the side
- Calculate principal stresses
- Replacement of integration with summations for calculating section properties
- Runge-Kutta method to integrate differential equations
- Bending stress calculation using stored values
- Above data is sufficient to calculate maximum shear stress and its direction at any point
Advanced Beam Model
Conclusion
- This involves 2-dimensional cross-sectional analysis and geometrically one-dimensional analysis
- Calculation of stiffness and mass properties using VABS
- Exact beam analysis is carried out to find the internal forces and moments
- The variational formulation
- Attachment region will face the maximum load
- From the L.E. of the bottom airfoil, failure will start
- This also second fractographic study’s result of static cracking
- Aerodynamic design criteria can become a constraint for structural analysis
- Critical speed of the compressor will be 2600 rpm
- Tip clearance of current compressor could be increased till 2.6 mm to achieve the same aerodynamic efficiency
- Finite element analysis gives high accuracy
- External aerodynamics forces can be calculated using airfoil design program
- Internal forces and moments can be calculated using external aerodynamics forces
- Strain recovery analysis using 2D-model
Static Analysis
Low Cycle Fatigue Analysis
Dynamic Analysis
Multiphysics Modeling
4- Advanced Beam Model
3. 3D-Photoelastic Stress Analysis
5- 3D BVP
1. Finite Element Analysis
2. Beam Model