Komandur Sunder Raj Power & Energy Systems Services Last Stage Performance Considerations in LP Turbines of Power Plants – A Case Study
2006 ASME Power Conference Last Stage Performance Considerations in LP Turbines of Power Plants - A Case Study Sunder Raj Presentation
Apr 11, 2017
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Komandur Sunder Raj
Power & Energy Systems Services
Last Stage Performance Considerations in LP Turbines of Power Plants – A Case Study
Factors Affecting Last Stage Performance of LP Turbines Case Study – Relationships Between Last Stage, Unit Rating, End Loading & Operating Range of Condenser Last Stage Exhaust Loss Curves Recommendations for Optimum Performance
Objectives
Last Stage Blades (LSB) Historically Specified & Designed by Matching Turbine to Condenser Cooling System for Specified Unit Rating Last Stage End Loadings Vary from 8000 lb/hr-sq.ft to 14000 lb/hr-sq.ft Corresponding Unit Loadings 1.1 to 2.1 Mwe/sq.ft
Background
Several Plants Upgrading/Replacing LP Turbines Considerations Include Efficiency, Reliability, SCC, Power Uprates, Aging, Inspection, Maintenance, etc. New LP Rotors, Blading, Steam Paths, Longer LSB, Redesigned Exhaust Hoods
Background
Condensers Typically Have Not Been Upgraded to Match Turbine Retrofits, Modifications Potential Mismatch Between Upgraded LP Turbine and Condenser/Cooling System
Background
For LSB Sizes 38” to 52”, Pitch Diameters 10’ to 13’ Blade Velocities 1000-1300 fps for 1800 RPM Last Stage Performance Function of Load & Pressure Ratio Last Stage Output Reaches Maximum at Critical Pressure Ratio (Choked Flow)
General
Exhaust Loss Curve Composite of: Leaving Loss (Kinetic Energy) Pressure Loss in Exhaust Hood Turn-Up Loss Occurring at Low Annulus Velocities
Choke Conditions for Diffusing Hoods Occur at Axial Mach Nos. 0.87-0.90 (Annulus Velocity of ~1058 fps)
General
Figure 1 – Exhaust Loss Curves
0
5
10
15
20
25
30
35
40
45
50
55
100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400
Annulus Velocity, Fps
Dry
Exh
aust
Lo
ss, B
tu/lb
43" 44"
52"
40"
44"47"
45"
AppoximateChoke Point
Figure 2 – Annulus Velocity for Different End Loadings, Exhaust Pressures
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00
Exhaust Pressure, in.HgA
Last
Sta
ge A
nnul
us V
elocit
y, fp
s
Condenser Operating Range
52 "LSB
40 "LSB
43 "LSB
47 "LSB
Case Study 1100 Mwe Power Plant (TC6F-43”LSB) Condenser Operating Range 2.0 - 4.0 in.HgA (35.0 F to 80.0 F Circulating Water Inlet Temperature) Design Pressure 2.3 in.HgA at 52.0 F Once-Through Cooling End Loading ~ 11,000 lb/hr-sq.ft
General
Table 1 – Last Stage Performance for 43”LSB
(1) (2) (3) (4) = (3)/(2) (5) (6) (7) (8) = (5) - (7) (9) (10)2.0 4.85 0.98 0.203 1044.2 1.70763 953.0 91.2 967.9 8,093,2332.5 4.89 1.23 0.251 1044.5 1.70726 964.7 79.8 977.3 8,154,1283.0 4.92 1.47 0.299 1044.7 1.70702 974.4 70.3 985.2 8,205,5063.5 4.95 1.72 0.347 1044.9 1.70675 982.8 62.2 991.9 8,250,1724.0 4.98 1.96 0.394 1045.1 1.70643 990.0 55.0 997.9 8,289,834
(11) (12) = (10) x (11)
(13) See Note 1 (14) (15) (16) = {(5) -
(15)}/(8)(17) See Note 2 (18)
(19) = {(17)/(18)} x
100
(20) = (10)/742.8
294.206 2.381E+09 890 21.1 982.5 67.70% 146.4 1128.851 12.97% 10,896239.937 1.956E+09 732 12.5 986.0 73.26% 139.7 1121.771 12.46% 10,978203.160 1.667E+09 623 8.5 991.1 76.20% 128.8 1110.617 11.60% 11,047176.526 1.456E+09 545 7.1 997.0 77.13% 115.9 1097.568 10.56% 11,107156.312 1.296E+09 485 7.2 1003.0 76.47% 102.3 1083.781 9.44% 11,160
NOTES:1. Annulus area per last stage is 123.8 sq.ft. For six exhaust ends, total last stage annulus area is 742.8 sq.ft.
Annulus Velocity, fps = Last Stage Volumetric flow/(742.8 x 3600)2. Last Stage Output, Mw = Last Stage Flow x (Last Stage Bowl Enthalpy - Used Energy End Point)/3412141.63
End Loading,
lb/hr-sq.ft.
Last Stage Annulus
Velocity Van, fps
Dry Exhaust Loss EL,
btu/lb
Used Energy
End Point UEEP, btu/lb
Last Stage UEEP
Efficiency, %
Generator Output,
Mwe
Last Stage Specific
Volume v, cft/lb
Last Stage
Exhaust Flow W,
lb/hr
Cond. Press., in.HgA
Expansion Line End
Point ELEP, btu/lb
Last Stage Press. Ratio, PSh/PB
Last Stage Output, % of Gen. Ouput
Last Stage Bowl Press.
PB, psia
Last Stage Bowl
Entropy SB, btu/lb
Last Stage Available
Energy AE, btu/lb
Isentropic Enthalpy
HISEN, btu/lb
Last Stage Shell Press.
PSh, psia
Last Stage Bowl
Enthalpy HB,
btu/lb
Last Stage Volumetric Flow Wv,
cft/hr
Last Stage Output,
Mw
Table 2 – Last Stage Performance for 52”LSB
(1) (2) (3) (4) = (3)/(2) (5) (6) (7) (8) = (5) - (7) (9) (10)2.0 4.85 0.98 0.203 1044.1 1.70753 953.0 91.2 967.9 8,093,6672.5 4.89 1.23 0.251 1044.4 1.70716 964.6 79.8 977.3 8,153,8343.0 4.92 1.47 0.299 1044.7 1.70695 974.4 70.3 985.2 8,204,9123.5 4.95 1.72 0.347 1044.9 1.70670 982.7 62.1 991.9 8,249,4844.0 4.98 1.96 0.394 1045.1 1.70643 990.0 55.0 997.9 8,289,181
(11) (12) = (10) x (11)
(13) See Note 1 (14) (15) (16) = {(5) -
(15)}/(8)(17) See Note 2 (18)
(19) = {(17)/(18)} x
100
(20) = (10)/1055
294.190 2.381E+09 627 10.0 974.7 76.10% 164.6 1146.978 14.35% 7,672239.924 1.956E+09 515 10.5 984.6 75.00% 143.0 1125.284 12.71% 7,729203.151 1.667E+09 439 12.0 993.6 72.68% 122.8 1104.932 11.12% 7,777176.522 1.456E+09 383 13.7 1001.6 69.67% 104.7 1086.645 9.63% 7,819156.310 1.296E+09 341 15.2 1008.7 66.18% 88.5 1070.27 8.27% 7,857
NOTES:1. Annulus area per last stage is 175.8333 sq.ft. For six exhaust ends, total last stage annulus area is 1055 sq.ft.
Annulus Velocity, fps = Last Stage Volumetric flow/(1055 x 3600)2. Last Stage Output, Mw = Last Stage Flow x (Last Stage Bowl Enthalpy - Used Energy End Point)/3412141.63
End Loading,
lb/hr-sq.ft.
Last Stage Annulus
Velocity Van, fps
Dry Exhaust Loss EL,
btu/lb
Used Energy
End Point UEEP, btu/lb
Last Stage UEEP
Efficiency, %
Generator Output,
Mwe
Last Stage Specific
Volume v, cft/lb
Last Stage
Exhaust Flow W,
lb/hr
Cond. Press., in.HgA
Expansion Line End
Point ELEP, btu/lb
Last Stage Press. Ratio, PSh/PB
Last Stage Output, % of Gen. Ouput
Last Stage Bowl Press.
PB, psia
Last Stage Bowl
Entropy SB, btu/lb
Last Stage Available
Energy AE, btu/lb
Isentropic Enthalpy
HISEN, btu/lb
Last Stage Shell Press.
PSh, psia
Last Stage Bowl
Enthalpy HB,
btu/lb
Last Stage Volumetric Flow Wv,
cft/hr
Last Stage Output,
Mw
Table 3 – Impact of 15% Power Uprate on Last Stage Performance for 43”LSB
(1) (2) (3) (4) = (3)/(2) (5) (6) (7) (8) = (5) - (7) (9) (10)2.76 6.01 1.36 0.226 1039.5 1.67891 953.8 85.7 968.1 9,576,7362.85 6.02 1.40 0.233 1039.5 1.67871 955.5 84.1 969.5 9,588,8143.25 6.07 1.60 0.263 1039.5 1.67783 962.0 77.5 974.7 9,637,1863.95 6.14 1.94 0.316 1039.4 1.67649 971.9 67.5 982.6 9,711,3705.00 6.24 2.46 0.394 1039.3 1.67488 984.1 55.2 992.4 9,804,425
(11) (12) = (10) x (11)
(13) See Note 1 (14) (15) (16) = {(5) -
(15)}/(8)(17) See Note 2 (18)
(19) = {(17)/(18)} x
100
(20) = (10)/742.8
215.802 2.067E+09 773 14.5 978.0 71.79% 172.7 1268.413 13.62% 12,893209.450 2.008E+09 751 13.4 978.6 72.49% 171.3 1266.769 13.52% 12,909185.840 1.791E+09 670 9.9 981.5 74.81% 163.7 1258.675 13.01% 12,974155.439 1.510E+09 565 7.3 987.7 76.60% 147.2 1241.382 11.86% 13,074125.309 1.229E+09 459 7.6 997.7 75.32% 119.6 1212.802 9.86% 13,199
NOTES:1. Annulus area per last stage is 123.8 sq.ft. For six exhaust ends, total last stage annulus area is 742.8 sq.ft.
Annulus Velocity, fps = Last Stage Volumetric flow/(742.8 x 3600)2. Last Stage Output, Mw = Last Stage Flow x (Last Stage Bowl Enthalpy - Used Energy End Point)/3412141.63
End Loading,
lb/hr-sq.ft.
Last Stage Annulus
Velocity Van, fps
Dry Exhaust Loss EL,
btu/lb
Used Energy
End Point UEEP, btu/lb
Last Stage UEEP
Efficiency, %
Generator Output,
Mwe
Last Stage Specific
Volume v, cft/lb
Last Stage
Exhaust Flow W,
lb/hr
Cond. Press., in.HgA
Expansion Line End
Point ELEP, btu/lb
Last Stage Press. Ratio, PSh/PB
Last Stage Output, % of Gen. Ouput
Last Stage Bowl Press.
PB, psia
Last Stage Bowl
Entropy SB, btu/lb
Last Stage Available
Energy AE, btu/lb
Isentropic Enthalpy
HISEN, btu/lb
Last Stage Shell Press.
PSh, psia
Last Stage Bowl
Enthalpy HB,
btu/lb
Last Stage Volumetric Flow Wv,
cft/hr
Last Stage Output,
Mw
Table 4 – Impact of 15% Power Uprate on Last Stage Performance for 52”LSB
(1) (2) (3) (4) = (3)/(2) (5) (6) (7) (8) = (5) - (7) (9) (10)2.74 6.01 1.35 0.224 1039.5 1.67891 953.5 86.1 967.8 9,574,5762.84 6.02 1.40 0.232 1039.5 1.67873 955.2 84.3 969.3 9,587,7243.26 6.07 1.60 0.264 1039.5 1.67782 962.1 77.4 974.7 9,637,5993.98 6.14 1.95 0.318 1039.4 1.67646 972.2 67.1 982.9 9,713,2045.05 6.24 2.48 0.398 1039.3 1.67483 984.6 54.7 992.8 9,807,062
(11) (12) = (10) x (11)
(13) See Note 1 (14) (15) (16) = {(5) -
(15)}/(8)(17) See Note 2 (18)
(19) = {(17)/(18)} x
100
(20) = (10)/1055
217.219 2.080E+09 548 10.1 974.7 75.29% 181.8 1277.477 14.23% 9,075210.288 2.016E+09 531 10.3 976.3 75.04% 177.8 1273.083 13.96% 9,088185.559 1.788E+09 471 11.2 982.5 73.63% 161.0 1256.005 12.82% 9,135154.451 1.500E+09 395 13.3 992.1 70.42% 134.6 1229.071 10.95% 9,207124.251 1.219E+09 321 16.0 1003.9 64.63% 101.7 1195.266 8.51% 9,296
NOTES:1. Annulus area per last stage is 175.8333 sq.ft. For six exhaust ends, total last stage annulus area is 1055 sq.ft.
Annulus Velocity, fps = Last Stage Volumetric flow/(1055 x 3600)2. Last Stage Output, Mw = Last Stage Flow x (Last Stage Bowl Enthalpy - Used Energy End Point)/3412141.63
End Loading,
lb/hr-sq.ft.
Last Stage Annulus
Velocity Van, fps
Dry Exhaust Loss EL,
btu/lb
Used Energy
End Point UEEP, btu/lb
Last Stage UEEP
Efficiency, %
Generator Output,
Mwe
Last Stage Specific
Volume v, cft/lb
Last Stage
Exhaust Flow W,
lb/hr
Cond. Press., in.HgA
Expansion Line End
Point ELEP, btu/lb
Last Stage Press. Ratio, PSh/PB
Last Stage Output, % of Gen. Ouput
Last Stage Bowl Press.
PB, psia
Last Stage Bowl
Entropy SB, btu/lb
Last Stage Available
Energy AE, btu/lb
Isentropic Enthalpy
HISEN, btu/lb
Last Stage Shell Press.
PSh, psia
Last Stage Bowl
Enthalpy HB,
btu/lb
Last Stage Volumetric Flow Wv,
cft/hr
Last Stage Output,
Mw
Figure 3 – Performance of 43”LSB & 52”LSB Before and After Power Uprate
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00
Exhaust Pressure, in.HgA
Last
Sta
ge A
nnul
us V
eloc
ity, f
ps
Original Range for 52 "LSB
Power Uprate Range for 43 "LSB
Original Range for 43 "LSB
Power Uprate Range for 52 "LSB
Original Operating RangePower Uprate Operating Range
For Optimum Last Stage Performance, Evaluate Performance Over Entire Operating Range Consider Mods if Evaluation Reveals Mismatch or Less than Optimum Performance For Power Uprates, LP Turbine Mods with Different LSB Offerings, Evaluate Performance Over Entire Operating Range Consider Condenser/Cooling System Mods to Properly Match LSB
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