GAS TURBINE BUCKET FINITE ELEMENT ANALYSIS

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GAS TURBINE BUCKET FINITE ELEMENT ANALYSIS
BY SERGIO A. SANCHEZ
FRONTERA GENERATION FACILITY
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PROJECT OUTLINE

• PERFORMANCE AND RELIABILITY IMPROVEMENTS FOR
  HEAVY DUTY GAS TURBINES
• GAS TURBINE STARTS/HOURS CRITERIA
• FIRING TEMPERATURE CONDITIONS
• START/SHUTDOWN CYCLES
• GAS TURBINE FIRST STAGE BUCKETS
• BUCKET MATERIAL PROPERTIES
• FINITE ELEMENT ANALYSIS ON BUCKET
• ACTIONS TO TAKE
• BUCKET IMPROVEMENTS
• GENERAL PICTURES

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GAS TURBINES STARTS / HOURS CRITERIA

• GAS TURBINE COMBUSTION INSPEC- TION EVERY 8000
  HRS. OR 400 STARTS.
• HOT GAS PATH INSPECTION EVERY 24000 HRS. OR 1200
  STARTS.
• MAYOR INSPECTION EVERY 48000 HRS.
• COMPRESSOR WATER WASH ON LINE AT 720 HRS.
• COMPRESSOR WATER WASH OFF LINE AT 4000 HRS.
  

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CAUSES OF WEAR HOT GAS PATH COMPONENTS

• THERMAL MECHANICAL FATIGUE
• HIGH-CYCLE FATIGUE
• RUBS/WEAR
• FOREIGN OBJECT DAMAGE
• METAL OXIDATION
• CORROSION
• EROSION
• CREEP DEFLECTION
• RUPTURE

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GAS TURBINES FIRING TEMPERATURE

• FIRING TEMPERATURE AFFECTS BUCKETS LIFE ( FIRST
  STAGE GROUP )
• GAS TURBINE OPERATING AT PEAK LOAD EACH HOUR ON
  FIRING TEMPERATURE AT 100 F (56 C) IS THE SAME,
  FROM A BUCKET PARTS LIFE STANDPOINT, AS SIX HOURS
  OF OPERATION AT BASE LOAD.
• THIS TYPE OF OPERATION WILL RESULT IN A
  MAINTENANCE FACTOR OF SIX.
• HIGHER FIRING TEMPERATURES REDUCE HOT GAS PARTS
  LIFE WHILE LOWER FIRING TEMPERATURE INCREASES
  PARTS LIFE.

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BUCKET LIFE FIRING TEMPERATURE EFFECTS
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• REDUCTION IN LOAD DOES NOT ALWAYS MEAN REDUCTION
  IN FIRING TEMPERATURE.
• FIRING TEMPERATURE DOES NOT DECREASE UNTIL LOAD
  IS REDUCED BELOW APPROXIMATELY 80 OF RATED
  OUTPUT.
• BUCKETS PART LIFE IS AFECTED FOR THESE MODES OF
  OPERATIONS.

FIRING TEMPERATURE AND LOAD RELATIONSHIP
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GAS TURBINE START/STOP CYCLE FIRING TEMPERATURE
CHANGES
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RAPID CHANGE IN GAS TEMPERATURE EFFECTS

• START-UP/SHUT DOWN CYCLES
• ACCELERATION
• LOADING/UNLOADING
• EDGES OF THE BUCKET RESPOND MORE QUICKLY THAN THE
  THICKER BULK SECTION.
• TEMPERATURE GRADIENT, IN TURN,PRODUCE THERMAL
  STRESS THAT,WHEN CYCLE CAN EVENTUALLY LEAD TO
  CRACKING.

FIRST STAGE BUCKET TEMPERATURE DISTRIBUTION
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GAS TURBINE BUCKET
ISOMETRIC VIEW
FRONT VIEW
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GAS TURBINE BUCKET
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BUCKET MATERIAL PROPERTIES
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FEA WITH CENTRIFUGE FORCE
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GAS TURBINE BUCKET FEA
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GAS TURBINE BUCKET FEA
GAS TURBINE BUCKET AT 1800 F
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GAS TURBINE BUCKET
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GAS TURBINE BUCKET
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ACTIONS TO TAKE

• BETTER CONTROL WITH FIRING TEMPERATURE AT PEAK
  AND BASE LOAD OF UNITS.
• REDUCE LOAD AT GAS TURBINES (LESS CAPACITY ).
• LESS START/SHUTDOWN AT GAS TURBINES.
• APPLY WATER WASH MONTLY INSTEAD OF WEEKLY.

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BUCKET IMPROVEMENT

• AUTO COOLING SYSTEM ON THE BUCKET ITSELF USING
  AIR FROM THE COMPRESSOR.
• ADD NEW AUXILIARY STEAM SYSTEM TO FORCE COOLING
  THE BUCKET.
• APPLY COATING PROTECTION MATERIAL TO THE BUCKET
  IN ORDER TO REDUCE METAL TEMPERATURE.
• USING ANOTHER SUPERALLOY WITH HIGHER YIELD STRESS
  VALUE.

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FIRST STAGE BUCKETS AND NOZZLES
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CRACK ON FIRST STAGE BUCKET
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CRACK AT 7th STAGE COMPRESSOR BLADES
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THANK YOU