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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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Preliminary Layouts & Down-select:
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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
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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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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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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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