Vextec Small Gas Turbine Testing

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Vextec Small Gas Turbine Testing

  1. 1. Laboratory Group Small Turbine Engine Testing: Evaluate New Design TechnologiesReplicate Failure in Fielded Components http://Gas-Turbine-Testing.com 1
  2. 2. Presentation Outline Current Conditions of Engine Testing Technology Need – Filling the Gap Between Engine Design and Full Scale Testing Small Turbine Testing Method & Characterization Failure Mechanisms Replicated Using Small Turbine Testing Developing Acceptance Test for Corrosion Induced Cracking Capabilities & Benefits of Small Turbine Testing 2
  3. 3. Current Conditions of Engine Testing Full scale gas turbine engine testing is expensive & time consuming Testing to failure is seldom performed on full scale engines Testing to failure is needed to fully assess the fatigue durability of components Other conventional testing methods used early in design process do not replicate the actual environmental conditions produced in operational enginesToday’s conditions leave a gap between conventional testingmethods used during the design process and expensive full scale testing 3
  4. 4. Filling the Gap Between Engine Design and FullScale Testing Need for a cost effective testing method that allows: Testing components to failure; multiple times Assess the durability of components in realistic operating environment Timely test turn around & acquisition of data Small engine tests produces component failures in realistic operating conditions and tests them to failure multiple times quickly and inexpensively 4
  5. 5. Small Turbine Engine Testing Monitor & acquire data from operating turbine Reproduce realistic environmental conditions Successfully test multiple failure mechanisms Compare & validate scaled turbine test data with full scale engine testing resultsReproduce & effectively measure realistic turbine engine environmental conditions 5
  6. 6. Example Small Turbine EngineSpecifications • Burner temperature 1700F • Uses 12 gallons per hour of fuel • 5.1” diameter • 112,000 RPM at max • Axial flow, integrally bladed, INCO-713 turbine rotor Realistic environment, fast turn around & cost efficient 6
  7. 7. Full Characterization of Small TurbineEngine  Rotating thermocouples  Static thermocouples  Strain gages  Pressure probes Small turbine testing is fully instrumented 7
  8. 8. Failure Mechanisms Reproduced in RealisticOperating Conditions  Fatigue crack growth  High cycle fatigue  Creep  Creep crack growth  Weld Repair  Corrosion Surface oxidation Sulfide Creep crack along blade root induced grain boundary cracking 8
  9. 9. Developing an Acceptance Test forCorrosion Damage 9
  10. 10. Issue Identification  Air Force field issues with corrosion lead to HCF failures in steel compressor blades  HCF failure results from crack initiation in corrosion pit  Multiple compressor stages exhibit corrosion  Prior efforts to reproduce corrosion in lab environment were unsuccessful Objective is to replicate field corrosion under realistic operation conditions utilizing small turbine 10
  11. 11. Testing Approach  Experience demonstrates that the free turbine application best meets the testing objectives  Starting point - USAF provided full scale engine performance  Test stand consist of four major sub systems – Gas generator – Rotor with full size blades – Drive system – Air handling/ contaminate system Variable Forced cooling pressure bleed Air Rotor Blade assembly Gas Generator Drive Contaminate system System Motor 11
  12. 12. Rotor/blade attachment• Two piece split rim design for easy assembly• Blades spacer application allows for multiple blade spacer combination.• Rotor designed for robust operation in adverse environment 12
  13. 13. Drive system• System uses belt drive• 15 Hp motor is controlled by Variable Frequency Drive (VFD)• Drive system produces 12,000 RPM loaded speed 13
  14. 14. Instrumentation Signals from instrumentationGas Generator Instrumentation• K-type thermocouple - EGT• Magnetic pickup – turbine speed Compact• PCB accelerometers – vibratory load DAQ system Test stand Instrumentation • Vane flow meter – contaminate dosing • PCB accelerometers – belt/pulley imbalance National Instruments Modules •K-type thermocouple – rotor inlet gas temperature • Two NI9239 general purpose •VFD statistics • One NI9233 accelerometer oMotor speed • One NI9211 thermocouple oMotor load oDrive frequency 14
  15. 15. Small Turbine Testing for Corrosion Blades tested - 10 Detailed blade examination – 20 hrs of operation  Photo documentation  Replicas created Total Test time – 75 hrs - Corrosion Reproduced 15
  16. 16. Comparison of USAF Fielded and SmallEngine Tested Blades 42 µm 60 µm Damage of fielded blade after Damage on tested blade after 51 583 hours hours Test damage mechanism is same as field damage mechanism 16
  17. 17. Small Turbine Testing Results of USAFCorrosion Test  Confirmed corrosion is the cause of initial damage  Confirmed sulfur was primary corrosion driver  Test replicated the corrosion observed in the fielded blades Corrosion HCF failure Sulfur drives Crack initiates Corrosion in Large damage sites Corrosion Pit size is not at grain indicative of boundary damage Reproduced blade corrosion in just 60-90 days 17
  18. 18. Capabilities & Benefits of Small Turbine Testing 18
  19. 19. Small Turbine Engine Capability  Accurate, realistic testing capability designed for early identification of failure issues  Reducing the amount of small scale specimen testing  Improving the validity of full scale engine testing  Accelerating design certificationAbility to bridge the gap between specimen & full scale testing for turbine engines 19
  20. 20. Benefits of Small Turbine Engine PRE-EMPTIVE Identify Issues During Design Phases, Prevent Fielded Failures TIMELY RESULTS ENGINE RELEVANT Useable Information in Weeks, Complex Capabilities Provide Not Months Real World Results COST EFFECTIVE A Fraction of the Cost of Traditional Methods 20
  21. 21. VEXTEC Laboratory Group Contact Info• http://Gas-Turbine-Testing.com• Ed Pope – 317-750-3414 / epope@vextec.com 21

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