Sensitivity Analysis - Dynardo GmbH

dynardo

Sensitivity Analysis - Dynardo GmbH

Optimization and

Robustness Evaluation

of an Axial Turbine using

Fluid-Structure

Interaction

Johannes Einzinger

ANSYS Continental Europe

johannes.einzinger@ansys.com

Dirk Roos & Veit Bayer

DYNARDO GmbH

dirk.roos@dynardo.de

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Outline

• Parametric Process Integration

Sensitivity Analysis

• Design Optimization

– Evolutionary Algorithm

– Adaptive Response Surface Method

• Robustness Evaluation

• Outlook

– Random Fields

– Design for Six Sigma (Reliability Analysis)

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Motivation

Power Plant 1000 MW

Efficiency 50 %

Increase of 1% +20 MW

=Electricity for 120 000

Inhabitants

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Workbench Platform & optiSLang

Process integration

CAD / PDM

ANSYS Workbench

Structural Mechanics - Fluid Dynamics - Heat Transfer - Electromagnetic

A Multi-Physics Design and Analysis System

Sensitivity Optimization Robustness Reliability Robust Design

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Parameterization

Process & Geometry

Sensitivity Analysis

Design Optimization

Robustness Evaluation

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Parameterization of the Workflow

Parametric Workflow for

Multi Physic Application

• Extended solver support

• Embedded analysis tool

• Automatic user interaction

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Parameterization of the Geometry

Define Parameter

1. Rotation Angle, Guide Vane

2. Rot. Angle, Shroud Profile

3. Rot Angle, Hub Profile

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1

2

3


Parameterization of the Geometry

1 2

1. CHT Model: Multi Body Part

2. CSD Model: Single Part

3. Add Blend for CSD, as Parameter

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3


Parameter Manager

Parameter List

Input Parameter = 15

Output Parameter = 9

List of Design Points

………….

Linked Parameter,

by Expressions, for

parameter restrictions or

further output

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Workbench Interface to optiSLang

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Workbench Interface to optiSLang

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Parameter Attributes

Input Parameter Parameter Name Initial Value Type

Blade Angels α GV,α Hub,α Shroud 0°, 0°, 0° deterministic

Rotational Velocity of Rotor Ω -2094 [rad/s] deterministic

Rotor Blend Radius r Blend 1 [mm] deterministic

Total Temperature Inlet T t,Inlet 1000 [K] deterministic

Total Pressure Inlet p t,Inlet 400 [kPa] deterministic

Pressure Outlet p out 187 [kPa] stochastic

All Material Properties - - stochastic

Output Parameter Parameter Name Initial Value Target

Total Temperature Ratio Θ T=T t,Inlet/T t,Outlet 1.115 -

Total Pressure Ratio Π p=p t,Inlet/p t,Outlet 1.673 -

Torque/Power at Rotor M P, P -577 [Nm], 1.21 [MW] maximize

Mass Flow Rate m 11.56 [kg/s] -

Isentropic Efficiency η 71.64 [%] maximize

Maximal v. Mises Stress σ max 218.6 [MPa] below limit

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Parameter Physics, Fluid Flow

c0 r

( Π , )

m& = f α

p

GV

( )

η = f Θ , Π

T

p

w r

α GV

c1 r

α Hub /

( Ω)

Shroud

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1

u r

1

= f

P

w r

c2 r

P, M ~ m&

Δ ⋅


1−2

2

u 2

r

( u c )

u


Parameter Physics, Mechanic

ΔT

rBlend

Δumax

σ max

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Parameterization

Process & Geometry

Sensitivity Analysis

Design Optimization

Robustness Evaluation

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Sensitivity Analysis

1. Scanning the Design Space with

optimized LHS, variation and

correlation are investigated

2. Identification of important variables

• Check Variation of Design Space

• Check Coefficient of Importance

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Latin Hypercube and Confidences

• n = 7 design variables

• N = 40 design evaluations (4 failed)

• Confidence levels are quite acceptable

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Variation of Design Space

initial

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Coefficient of Importance, CoI

CoI=94%>80% CoI=91%>80%

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Coefficient of Importance, CoI

Deactivation

of outliers

50% variance of the stress variation can be

explained by the given n = 7 design variables

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Meta-Model of Prognosis, MoP

Response Surface

Output: Power

Meta-Model

Output: Power

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Meta-Model of Prognosis, MoP

Response Surface

Output: Efficiency

Meta-Model

Output: Efficiency

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Coefficient of Importance, CoI vs.

Coefficient of Prognosis, CoP

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Objective Function

Target Function for Optimization:

⎛ −


1 P ⎞

= ( 1−

) + ⎜⎜ 1 ⎟⎟ min;

4 ⎝ 2[

MW]


f η = σ < σ

Target

seqv

Limit

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!


Anthill Plots Objective

initial

Good Design

Points

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Conclusion Sensitivity Analysis

• Is Sensitivity reliable, CoI?

• Is Sensitivity reliable, CoP?

• Is Sensitivity plausible, physics?

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Parameterization

Process & Geometry

Sensitivity Analysis

Design Optimization

Robustness Evaluation

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Design Optimization

Gradient-Based

Algorithms

Response

Surface Method

Evolutionary

Algorithm

Local

Adaptive RSM

Pareto

Optimization

Global

Adaptive RSM

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Optimization Strategy

Sensitivity Analysis

• Shows Potential

• Indicates multiple local

optima

• No parameter reduction

Strategy:

• Global search, EA

• Start design(s) from SA

• Local improvement, ARSM

initial

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Outlook Strategy

Sensitivity Analysis

• Shows Potential

• Indicates global optimum

• Parameter reduction

Strategy:

• Pre-optimization in sub space,

ARSM

• Local improvement, EA (full space)

• Start design(s) from ARSM

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Evolutionary Algorithms (EA)

Optimization in Nature:

- Survival of the fittest

- Evolution due to mutation, recombination and selection

Evolution Algorithms [EA]

Genetic Algorithms [GA]

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Evolutionary Algorithms (EA)

• History of the Evolutionary Algorithm

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Evolutionary Algorithms (EA)

best design 257

start population

initial

• Due the non-convex

behavior of the

efficiency and

nonlinear power

function a global

search strategy

using genetic

algorithm is

recommended

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Design variable 2

Design variable 2

Adaptive Response Surface

Methods (Local)

Design variable 1

Design variable 1

objective

objective

1. Iteration

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objective

5. Iteration

3. Iteration


Adaptive Response Surface (ARSM)

• The ARSM does not provide differentiable and smooth

problems; very efficient for n < 15 design parameters

• Starting solution is based on the best design of the EA

• The design space is reduced to 20% around start solution

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Adaptive Response Surface (ARSM)

best design ARSM

best design EA

start population

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initial


Initial vs. Optimized Design

Input Initial

Design

Optimized

α Hub 0 -0.34

α Shroud 0 -0.18

Ω [rev/s] -335 -365

α Guide Vane 0 -9.68

Output Initial Design Optimized

T t Ratio 1.116 1.151

p t Ratio 1.674 1.848

η [%] 71.65 81.54

Power [MW] 1.208 1.329

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1,8

1,6

1,4

1,2

1

0,8

0,6

0,4

0,2

0

Initial vs. Optimized Design

Initial

Optimized

Initial

Optimized

Span=0.95

Span=0.50

Isentropic Mach Number

Initial vs. Optimized

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1

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Initial vs. Optimized Design

Isotropic Mach Number

Initial Rotor

Optimized

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Initial vs. Optimized Design

• n = 7 design variables

• N = 76 + 257 + 84 = 417 design evaluations

(SA + EA + ARSM)

• How robust is the initial design?

• How robust is the optimized design?

• How reliable is the optimized design?

• How large is the influence of surface uncertainties?

Output Initial SA EA ARSM

Objective 1.0766 0.90034 0.86841 0.86259

η [%] 71.65 80.60 81.26 81.54

Power [MW] 1.208 1.304 1.343 1.329

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Parameterization

Process & Geometry

Sensitivity Analysis

Design Optimization

Robustness Evaluation

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Robustness Evaluation

1. Scanning the Robust Space with

optimized LHS, variation and

correlation are investigated

2. Identification of important variables

• Check Variation of Robust Space

• Check Histogram, limits, probabilities

• Check Coefficient of Importance

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Variation of Robust Space

• n = 15 random parameters

• N = 50 design evaluations

• Initial vs. optimized design

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Correlation, CoI, Histogram

Guide vane angle

vs. mass flow rate

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Define Objective Limits

• Limit state conditions

• Random parameters

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Evaluation of Histogram

Limit for Variable

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Evaluation of Histogram

Non-robust

initial design

Robust

optimized

design up to a

sigma level of

4.5

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Conclusion Robustness Evaluation

• Is there a problem?

• Can we explain, CoI?

• Who is responsible?

CoI>80%

Allowed Limit

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Parameterization

Process & Geometry

Sensitivity Analysis

Design Optimization

Robustness Evaluation

Summary

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Summary

• Workbench supports full Workflow

– Geometry, Meshing, Simulation, Post-Processing

• Multi Physics support

• Parametric Workflow management

• Automatic and embedded solution procedure

Sensitivity Analysis

• Design Optimization

• Robustness Evaluation

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