structural mechanics of steam turbines: facing · pdf filestructural mechanics of steam...

© Siemens AG 2012. All rights reserved.

E F PR SU R&D HP 3

Structural Mechanics

of Steam Turbines:

Facing Challenges in

FE-Postprocessing

with STARpost

Dr. Benjamin Kloss-Grote

Siemens Energy

Large Scale Steam Turbines R&D

Mülheim/Ruhr, Germany


May 2012 Siemens Energy


Dr. B. Kloss-Grote SCC 2012

Contents

1. Introduction

2. The Challenge

3. Existing Solutions in Abaqus

4. Siemens Energy’s Solution: STARpost

5. Summary




1. Introduction

Boiler

HP + IP + LP Steam Turbines

Condenser

Generator

Coal Fired Steam Power Plant SPP




1. Introduction

Siemens Steam Turbine SST5-6000 (900MW, H-I-L-Turboset)

Example:

total mass >1000 tons

rotor: 55 m long, 430 tons

HP: inlet 540°C (1000°F), 270 bar (3900psi)

IP: inlet 580°C (1080°F), 70 bar (1000psi)

LP: inlet 204°C (400°F), 4 bar (60psi)

power output: 900 MW

typical lifetime: 30 years




Outer Casing (schematic)

1. Introduction

Topology of a Siemens Intermediate Pressure (IP) Turbine (schematic)

Example Steam Conditions:

Inner Casing

HP TurbineLP Turbines,

GeneratorRotor (schematic)

Exhaust: 204°C (400°F), 4 bar (60psi)

Inlet: 580°C (1080°F), 70 bar (1000psi)




Contents

1. Introduction

2. The Challenge



5. Summary




Non-Isothermal Assembly

(Loadcase: Steady State Operation)

! Material Strength( , , )( , , ) ( , , )existing allowable

allowable

x y zx y z x y z

SF

high

low

low

high

high

low

(2)

Legend:

2. The Challenge (I)

Strength Assessments in Isothermal vs. Non-isothermal Assemblies

Isothermal Assembly

(Loadcase: Pressure Test)

Existing

Stress (Mises)

! Material Strength( , , )existing allowable

allowable

x y z constSF

Strength

Assessment

SF: Safety Factor

(1)

Temperature

Material Strength Inhomogeneous temperature distribution

prevents classic stress based assessments




2. The Challenge (I)

Solution I: New Field Output

! Material Strength( , , )( , , ) ( , , )existing allowable

allowable

x y zx y z x y z

SF

Equation 2 from slide 7:

divided by the material strength:

!( , , ) 1( , , )

Material Strength( , , )

existing

existing allowable

allowable

x y zMU x y z MU

x y z SF

(3)

…results in a new variable: the material utilization MU.

%502

1%25

200

50

allowableexistingMUMU

MPa

MPa

Example: Existing Mises stress: 50 MPa; material strength: 200 MPa, allowable safety factor: 2

!( , , ) 1( , , )


existing

existing allowable

allowable

x y zMU x y z MU

x y z SF

!( , , ) 1( , , )


existing

existing allowable

allowable

x y zMU x y z MU

x y z SF

!

%502

1%25

200

50

allowableexistingMUMU

MPa

MPa

Advantage:

The allowable MU is constant over the whole assembly even in non-isothermal

assemblies if the allowable safety factor is constant.

Constant limits are easy to display in field output contour plots




2. The Challenge (II-VI)

More Challenges for Steam Turbine Mechanics

II. Material strength is in general not contained in .inp and .odb

(e.g. Creep Rupture Strength Rm,t,T)

III. Different materials; assemblies with more than one material

(tedious input; material association has to be identified)

IV. Many frames need to be evaluated

(process automation required)

V. Many different output variables necessary

(material utilization (MU) based on different stresses; also strains, multi-axiality

factors etc.)

VI. Varying allowable safety factors

(e.g. for creep range and non creep range)




Contents

1. Introduction

2. The Challenge



5. Summary





User Subroutine UVARM in the Light of the Challenges

Advantages +

Material utilizations can be calculated

during the solver process

Major Disadvantages –

a) No self-explanatory output variable

names significant confusion and

possible quality issues,

b) A solver run is required. If a user output

has not been requested before the solver

run and should be added afterwards to the

ODB

a new solver run is required.

Inconvenient for long lasting creep

calculations (t=several weeks).

c) Material handling is very tedious (input

of material properties, material association

identification)

= User subroutine (Abaqus/Standard) for the generation of element output

It is possible to calculate the

utilizations with UVARM,

although limitations regarding

effectiveness and possible

quality concerns apply.




Contents

1. Introduction

2. The Challenge



5. Summary





Structure of the Python Plug-Ins

Structure of STARpost, the

post processing suite

for static and creep analyses,

including relevant inputs and

outputs:

STARvisSTARvisEffective Visualization of

STARmech‘s user variablesSTARvisSTARvisEffective Visualization of

STARmech‘s user variables

STARmechSTARmechCalculation of strength

assessment output variables

Effective strength assessment

contour plots in Abaqus/CAE

STARpostSteam Turbine Analysis Routines Post Processing Suite

ODBODB

R&D-Materials

Dpt. material

files

R&D-Materials

Dpt. material

files

User

input

(GUI)

User

input

(GUI)

User

input

(GUI)

User

input

(GUI)

ODB

with added user variables

ODB

with added user variables




XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

XX Material Name XXXXXXXXXX

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

MF

MF

MF

MU

_M

is

MU

_M

ax

MU

_M

axP

MU

_M

inP

DM

UC


Screenshot of the STARmech GUI

Screenshot of the GUI of

the STARmech-Plug-In:

Requesting user field

outputs for an efficient

strength assessment

during post processing,

suitable for

• non-isothermal,

• multi-material,

• multi-frame,

• static and

• creep

analyses

Frames

Requesting Field Outputs

ODB, Materials




MF

MF

MU_Mis_200k

MU_Max_200k

DMUC_200k


Screenshot of the STARpost GUI

Screenshot of the GUI of the

STARpost-Plug-In:

Effective visualization of the

user output variables

calculated by STARmech

Existing Field Outputs

Frames

STARvis

STARmech

STARvis presents each user

output variable in a unique,

predefined way





Comparison between Mises Stress and Material Utilization (after creep)

STARpost user field output

Mises Material Utilization

(User01)

Mises Stress

Significant difference

in the distribution

Challenge met

successfully

high

low

high

low





Excerpt from STARpost’s Advanced Field Outputs

Name Description

User10_TempZone

Temperature Zone

Ti: Intersection Temperature

Tallowed: Maximum allowed application temperature of the material

User11_Min(Rp/Rm) min (Yield Strength Rp0.2,T, Creep Rupture Strength Rm,t,T)

User05_DMUC Dominant Material Utilization Criterion of User02_MU_Max

red, prohibited range ( )

yellow, creep range ( )

blue, non creep range ( )

allowed

i allowed

i

if T T

if T T T

if T T

, , ,

, , ,

, , ,

yellow ( ), min( , )

red ( ), min( , )

blue ( ), min( , )

Mises

m t T p T

I

I

m t T p T

III

III

m t T p T

Mises if MU_maxR R

if MU_maxR R

if MU_maxR R





Advanced Field Outputs: Differentiating between Temperature Zones


Tempzone (User10) Prohibited Temperature Range

Creep Range

Non Creep Range

Color Coding:

very handy for strength assessments,

because different criteria apply for the creep and the non creep range





Advanced Field Outputs: Material Strength and DMUC


Material strength

(Minimum of Yield Stress and

Creep Rupture Stress, User11)


Dominant Material Utilization Criterion

(DMUC, User05)

Max. Principal MU dominates

Mises MU dominates

Min. Principal MU dominates

Color Coding DMUC:

very handy for plausibility checks

high

low




Contents

1. Introduction

2. The Challenge



5. Summary




5. Summary

Challenge: In non-isothermal assemblies, the stress (or strain) cannot be used solely

for strength assessments, because the material strength varies over the assembly

Abaqus offers the UVARM subroutine, which has some disadvantages regarding the

ease of use

Siemens Energy has developed STARpost, a Python based plug-in for Abaqus/CAE

for efficient post processing of non-isothermal assemblies, especially for creep

calculations

STARpost is fully automated with an intuitive GUI

STARpost can effectively generate and visualize strength assessment field output

variables

Standard and advanced user variables enable a quick and quality assured strength

assessment

With Abaqus and STARpost, we can reduce the development time and enhance the

value we deliver for our customers




Thank you for your attention!

structural mechanics of steam turbines: facing · pdf filestructural mechanics of steam...

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