sco2 turbomachinery and low-leakage sco2 end seals · motivation for using non-contact face seals...

sCO2 Turbomachinery and Low-Leakage sCO2 End Seals

GE Global Research Rahul Bidkar Doug Hofer Chiranjeev Kalra Andrew Mann Max Peter Rajkeshar Singh Edip Sevincer Azam Thatte Jifeng Wang

Southwest Research Institute Tim Allison Klaus Brun Stefan Cich Meera Day Chris Kulhanek Jeff Moore Grant Musgrove Aaron Rimpel

Disclaimer: "This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United

States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal

liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or

represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service

by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or

favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily

state or reflect those of the United States Government or any agency thereof."

Acknowledgement: "This material is based upon work supported by the Department of Energy under Award Number DE-FE0024007"

2 / GE sCO2 Turbines & Seals – UTSR

Nov 2015

Outline

• Overview – sCO2 power cycles

• sCO2 turbomachinery at GE

• 10 MWe turbine

• 450 MWe turbine

• End seals for sCO2 turbines

• sCO2 Seals test rig


Nov 2015

sCO2 Application Space

700

600

500

400

300

200

Steam

10 100 1000

Power Output [MWe]

So

urc

e T

em

pe

ratu

re [

C]

sCO2 CSP

50+ % th 2020-2025

ORC

LWR

HDGT CC

Direct Fired sCO2

2030+

Gen 4 Nuclear

2030+

sCO2 WHR Compact

th>ORC 2015-2020

sCO2 Fossil

th 2-5 pts above Steam

2025+

(From Hofer, 2014)


Nov 2015

Recompression sCO2 Cycle

• Recompression sCO2 cycle for CSP and utility-scale applications

• Recompression loop added for better recuperation

• Ongoing research in developing power plant components (turbines, compressors, recuperators)

• This presentation focuses on turbine maturation and turbine end seals for enabling higher cycle efficiencies

HEA

T

SOU

RC

E

T

HIGH TEMP RECUPTR

LOW TEMP RECUPTR

RECOMP COMP

COOLER

1

2

3

4

5

6

7

8 8

GEN

1

2

3

4

5

6

7

8

Te

mp

era

ture

Entropy

Typical sCO2 recompression cycle

T-S diagram

(From Kalra et al., 2014)


Nov 2015

sCO2 power cycle roadmap & technology gaps

Parallel development on components (Seals, bearings, valves) and materials to enable higher efficiencies

1

10

100

1000

No

min

al S

ize

(MW

)

2010 2015 2020 2025 2030

Sunshot SwRI-GE 10 MW Demo

(axial turbine)

CSP Application

(Hofer, 2014)

Echogen

Waste-Heat Recovery

Kacludis et al. 2012)

Medium scale Demo

(axial turbine)

(Nominal 50MW)

(Hofer. 2014)

Utility scale Demo

(axial turbine)

(Nominal 500MW)

RCBC Sandia

National Lab

(Wright et. al,

2011) IST, Bechtel Marine Prop.

Corp. (Clementoni et al.

2014)

Timeline for sCO2 turbomachinery development

Published work Projected Date

Technology gaps

(From Hofer, 2014)


Nov 2015

10 MWe SunShot turbine

Not to scale

• Very high power density turbine for CSP applications

• Key features

• Supercritical CO2 aero design

• Seals with thermal management

• Bearings and rotordynamics

10 MWe turbine

test stand

Thermodynamic cycle

10 MWe turbine rotor


Nov 2015

Test Loop –10 MWe turbine

SwRI B278

Heater

sCO2 Pump

Compressor

Cooler

GE partnering with Southwest Research Institute in demonstrating the turbine

Thermodynamic cycle Representation of Southwest

Research Test Loop

Picture of Southwest Research Test Loop


Nov 2015

450 MWe – Layout Conceptual design & Cycle design

450 MWe Thermodynamic cycle

Single shaft , single speed option

Dual shaft , dual speed option

Final turbine layout – single shaft , single speed, dual flow, single casing

Reheat cycle with single-shaft, single speed layout and dual flow turbines to maximize efficiency


Nov 2015

450 MWe Conceptual Design

Final layout – single shaft , single speed, dual flow, single casing

Systems Aero & Mechanical Rotordynamics

Turbine concept analyzed with thermodynamic cycle optimization, turbine aerodynamic and rotordynamic calculations


Nov 2015

450 MWe turbine-compressor layout

SEAL

TPB TC

SEAL TPB

BP

HPT

LPT

SEAL

TPB

TC

CP2

HPT

LPT

SEAL TPB

CP1

Key Features • 450 MW net electric power

• 3600 rpm, single-shaft

• Reheat cycle 52% efficiency

• Single casing dual flow LPT, dual flow HPT

• Single casing back-to-back compressors


Nov 2015

Motivation for using non-contact face seals (dry gas seals)

• Laby seal:

• Seal physical clearance varies during start-up, shut-down and cycle variations.

• Teeth radius can be designed only for one operating condition leading to non-optimal gap and leakage loss at other operating points

• Non-contact Face seals

• Stationary ring axially pushed towards the rotating ring. Spring biasing ensures a small physical gap under all operating conditions

• Stationary and rotating rings have spiral grooves (or some other geometry) that generates lift-off pressure with speed & avoid contact

Rotor

Non-adaptive Laby seal

Phigh

Plow

Seal physical clearance

Adaptive Dry gas seal

Spiral groove geometry on

rotor


Nov 2015

End seals for sCO2 turbines

• sCO2 cycles are unique

• closed loop (unlike open loop gas turbines)

• leaked CO2 needs to be recompressed as vapor (efficiency loss) unlike steam where the end leakage can be condensed to liquid and pumped back

• Seal CO2 leakage has implications for cycle efficiency as well as CO2 replenishment cost

Difference between Steam and CO2 leakage flow compression

End seal layout for a sCO2 turbine


Nov 2015

Turbine End Seal penalty analysis

• 2 x end seals on 450 MWe turbine are worth 0.55% cycle efficiency (1% loss of efficiency is worth $12/KWe)

• Alternate ways of regaining this efficiency (like increasing inlet temperature) are costly compared to developing seals

• Low-leakage seals are an effective method of keeping sCO2 cycles competitive over other power cycles

2 X Turbine End Seals

50.6

50.8

51

51.2

51.4

51.6

51.8

52

52.2

0 0.2 0.4 0.6 0.8 1

Ne

t C

ycl

e E

ffic

ien

cy

(%)

End Seal Total Leakage (% of turbine flow)

Desired Face Seal

Existing

Labyrinth Seal


Nov 2015

Seal Design Challenges

• Maintaining parallelism between rotating & stationary rings is needed for successful seal operation

• Pressure & thermal loads, manufacturability at large diameter limit simple scaling of existing designs

• Innovative seal design features & detailed analysis needed to ensure parallelism

CTQ Value

Diameter 24 inch

Pressure differential > 1000 psi

Seal operating conditions

Force vs. Gap for a face seal (assuming parallel faces)

Deformed rings (rotation converging) 0 0.5 1 1.5 2 2.5 3 3.5

Se

pa

rati

ng

Fo

rce

Rotating-Stationary Ring Gap (1/1000 inch)

< 1/1000 inch

Stationary Ring

Rotating Ring

Stationary Ring

Rotating Ring

Stationary Ring

Rotating Ring

Stationary Ring

Rotating Ring

Deformed rings (rotation & distortion)

Deformed rings (rotation diverging)


Nov 2015

Seal Concept

• Springs & pressure bias the stationary ring towards the rotor

• Spiral grooves generate separating force

• Seal tracks rotor axial transients

Seal stator

Seal stationary

ring

Springs

Casing

Stationary Ring

Rotor

Stator

Spring

Secondary seal

Casing

Stator Stationary

Ring

Rotor

Spiral grooves on the rotor


Nov 2015

sCO2 Seals test rig concept

Skid/frame

Pressure vessel (48” OD)

Electric

motor

CO2 inlet CO2 exit

sCO2 Test Loop Concept

Seal test rig concept developed for high pressure, high temperatures and large diameter seals


Nov 2015

Summary

• sCO2 turbine development at GE

• 10 MWe CSP application

• 450 MWe utility-scale application

• Seal leakage can be significant penalty on cycle efficiency

• Seal concept and analysis, along with a Seals test rig concept


Nov 2015

References 1. Wright, S A, et al. “Summary of the Sandia Supercritical CO2 Development Program,” SCO2 Power Cycle Symposium,

Boulder CO, 2011.

2. Clementoni, E M, et al, “Startup and Operation of a Supercritical Carbon Dioxide Brayton Cycle,” J Eng for Gas Turbines and Power 136, 2014.

3. Kacludis, A, et al, “Waste Heat to Power Applications Using a Supercritical CO2-Based Power Cycle,” Power-Gen International, Orlando FL, 2012

4. Hofer, D. “Development of Supercritical CO2 Power Cycle Applications – The Pathway Forward”, IGTI Turbo Expo, Dusseldorf, Germany, June 2014.

5. Kalra, C. et al. “Development of High Efficiency Hot Gas Turbo-expander for Optimized CSP supercrtical CO2 power block operation,” 4th International SCO2 Power Cycle Symposium, Pittsburgh PA, 2014.

sco2 turbomachinery and low-leakage sco2 end seals · motivation for using non-contact face seals...

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