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Development of High Efficiency Hot Gas Turbo-Expander for Optimized CSP Supercritical CO2

Power Block Operation

Chiranjeev Kalra, Doug Hofer, Edip Sevincer GE Global Research Jeff Moore, Klaus Brun Southwest Research Institute

The 4th International Symposium - Supercritical

CO2 Power Cycles

September 9-10, 2014, Pittsburgh, Pennsylvania

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

the authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

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2 April 30, 2014

Sunshot Program Overview

Team: Southwest Research Institute, GE, KAPL, & Thar 3-year, $8.5M program to develop & test an expander &

recuperator for sCO2 power generation from CSP. Schedule: Expander final design complete.

System targets: Expander targets:

• 10MWe net module size

• 50% net thermal efficiency

• ~14MW shaft power

• >700C inlet temp

• >85% aero efficiency

• Multi-stage axial

Not to scale

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3 April 30, 2014

Prior Experience

GE Global Research

• sCO2 Systems

• Thermal Management

GE Power & Water

• USC steam materials

• High pressure casing

• High-power density flowpath GE Aviation

• Manufacturing

GE Oil & Gas

• CO2 Compressors

• Dry Gas Seals

• Rotordynamics

SWRI

• Test Loop Design

• Turbomachinery Design

• Advanced Analysis

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4 April 30, 2014

Target Power Cycle

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5 April 30, 2014

Turbo-machine layout options

Option Generator Compressor Turbine RPM

High speed, Optimal

A. IC

B. PM

A. Single stage centrifugal

B. Multi stage pump

A. Radial

B. Axial Optimized for compressor

High speed, expander only

A. IC

B. PM None A. Radial

B. Axial Optimized for expander

High speed, Geared

A. IC

B. PM

C. 3600 rpm

A. Single stage centrifugal

B. Multi stage pump

A. Radial

B. Axial Both expander and compressor run at optimal speed

3600 rpm integrated

3600 rpm Multi stage pump or compressor

Multi stage Axial at 3600 rpm

3600 rpm

3600 rpm – expander only

3600 rpm None Multi stage Axial at 3600 rpm

3600 rpm

IC: Inductively coupled, PM: Permanent magnet , 3600 / 1800 rpm synchronous generator

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6 April 30, 2014

Preliminary Layouts & Down-select:

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7 April 30, 2014

Overall design & modeling philosophy 1. Correlations & methods originally developed for steam & air will be

valid for conceptual design for CO2 in expander region because it is

nearly an ideal gas.

2. Need to include higher margins, particularly for non-ideal gas regions

(end seals) and fluid-structure interactions.

3. Validate results with CFD.

T=700C P=240 bar

P=85 bar

Calorically Perfect Gas: Cp=const Ideal Gas: 𝑃𝑉

𝑅𝑇= 1

T=700C

T=550C

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8 April 30, 2014

Aerodynamics

Mean-line 1D: Excel • GE proprietary loss model • Ideal gas CO2 properties

2D/3D: TP3, CAFD • GE proprietary design tools • Ideal gas CO2 properties

CFD: TACOMA, ANSYS CFX • Real gas tabular CO2 properties • Used to validate mean-line and

2D/3D design code predictions • Good agreement for efficiency and

flow function

2D Airfoil shapes

1D Mean-line flow path

CFD Analysis

CG

1

23

4

5

6

77

8

9

10

11

12

13

14

0.00| 0.25| 0.50| 0.75| 1.00|

0.200E+00--- - - - -

0.250E+00--- - - - -

0.300E+00--- - - - -

0.350E+00--- - - - -

0.400E+00--- - - - -

Rel

Isentropic

Mach

1

23

4

5

6

77

8

9

10

11

12

13

14

CG

1 1

GDS: /users/204010814/hofer_grc/projects/doe_sunshot_sco2_expander/turbine_study_jan_2013/alternate_cycle_conditions/cafd/design6_7-31-2013/da/try_26 Region: BLADE1

Mult suctn surf peak @ 1%peak suctn M# ~1.2*mexit blade score= 54. %

0.10.060.02 CAREA

-0.02-0.06-0.1

0.000

0.50.30.1 THROT

-0.1-0.3-0.5

0.000

0.50.30.1 STAGGR-0.1-0.3-0.5

0.000

0.50.30.1 DELTA1-0.1-0.3-0.5

0.000

0.50.30.1 RAD_LE-0.1-0.3-0.5

0.000

0.50.30.1 WEDGE-0.1-0.3-0.5

0.000

0.50.30.1 OVT

-0.1-0.3-0.5

0.000

0.50.30.1 UGT

-0.1-0.3-0.5

0.000

Move_an_ESP

X OF TE= 0.0

Y OF TE= 0.0

TE-THCK= 0.0

TE-ALPH= 0.0

CAREA = < knob >

THROT = < knob >

STAGGR = < knob >

DELTA1 = < knob >

RAD_LE = < knob >

WEDGE = < knob >

OVT = < knob >

UGT = < knob >

TMAX = 0.0

PCTZ = 0.0

ZOFF = 0.0

THOFF = 0.0

1

2

3

4

5

6

7

8

on/off: curv solverprefs thick

ref1 ref2 old

adjustscale

zoomblade

RunSolver

updatedisplay

adjref1

adjref2

togglemodeadd/del

points

undo

controlpoints

resetthroat

resetoptions

resetblade

fit old

zero crvLS TE

zero crvUS TE

Savebest

Loadbest

AutoOptimize

Conf Dat Table

jsl Imm carea throt Tmin/T ThrtArea stagger te thick LE Rad Imin

11 1.000 0.1358 0.1516 1.000 0.152 2.45 0.0201 0.012 1.24E-03

plt_angl plt_over tmax pctz betam1 delta1 betam2 ovt ugt wedge

0.00 ******* 0.177 0.504 59.00 -8.73 -62.98 4.11 9.77 8.73

STREAM SHEET

Tip

Pitch

Root

Out

In

Phys

Cross

18:46 08/01/13 mH01184644.bdf 204010814@NSK1204010814D W OGL PLOT 1EGS LIB 6.1a 2009/03/06 (egs rep_wmf 7.0 2010/01/29 on NSK1204010814D)BBP ver tes t-6.70 2013/01/31

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9 April 30, 2014

Seals Labyrinth: Labflo, ANSYS CFX • GE proprietary model validated for steam & air • Applied CO2/air scaling factors • CFD predicts significantly higher leakage

• Need conservatism in conceptual design phase (aero & rotordynamics)

Dry Gas Seals • Commercially available at the required

pressure but limited to low temperature and small diameter.

• GE developing tools to predict performance &

lifing under the PREDICTS program

CFD analysis of interstage laby seal flow in CO2

DGS Face Pressure Distribution from CFD

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10 April 30, 2014

Heat Transfer Challenges • Need to cool shaft from turbine exit (>500C) to DGS

& bearing max T (<200C) in short axial span • sCO2 has high convective heat transfer

Empirical Correlations • Shaft FEA model in ANSYS • Gazley HTC correlation applied as boundary conditions

Conjugate Heat Transfer • Coupled CFD, heat transfer, and shaft FEA in ANSYS

Result • Agreement within 10% • FOCUS program to develop & test advanced thermal

management techniques to maintain gradients

Shaft Temperature Contours

Conjugate HT

Gazley HTC Boundary Condition

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11 April 30, 2014

Rotordynamics

1

1.5

2

2.5

3

3.5

4

0 2 4 6 8

CS

R

Average Gas Density (lbm/ft3)

Region A

Region B

𝐶𝑆𝑅 =𝑂𝑝𝑒𝑟𝑎𝑡𝑖𝑛𝑔 𝑆𝑝𝑒𝑒𝑑

1𝑠𝑡 𝑈𝑛𝑑𝑎𝑚𝑝𝑒𝑑 𝐶𝑟𝑖𝑡𝑖𝑐𝑎𝑙 𝑆𝑝𝑒𝑒𝑑

Challenges • High gas density

• High operating speed • Low critical speed (large L/D)

Interstage laby seals • Texas A&M code • Real gas CO2 properties

Balance piston seal • Texas A&M code • Perfect gas properties

Result • Due to uncertainty in seal damping, we used a factor of safety 10x API level II minimum

(final logdec > 1.0) • PREDICTS program developing mid-span gas bearing

Sunshot

Not to scale

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12 April 30, 2014

Final Rotor Design

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13 April 30, 2014

Summary

• sCO2 turbine design completed by the SunShot project team to meet the program objectives

• The design demonstrates key sCO2 turbine design features – compact & low cost

• Design tools & prior experience in various products cover the operating range of a sCO2 turbine

• Integration of these diverse technologies into a single

machine is challenging but required to achieve high efficiency

• High power density enables compact design and requires development of custom high performance

turbo-machinery components

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