1. Laboratory Group
Small Turbine Engine Testing:
Evaluate New Design Technologies
Replicate Failure in Fielded Components
http://Gas-Turbine-Testing.com
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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
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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
engines
Today’s conditions leave a gap between conventional testing
methods used during the design process and expensive full
scale testing
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4. Filling the Gap Between Engine Design and Full
Scale 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
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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 results
Reproduce & effectively measure realistic turbine engine
environmental conditions
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6. Example Small Turbine Engine
Specifications
• 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
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7. Full Characterization of Small Turbine
Engine
 Rotating thermocouples  Static thermocouples
 Strain gages  Pressure probes
Small turbine testing is fully instrumented
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8. Failure Mechanisms Reproduced in Realistic
Operating 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
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9. Developing an Acceptance Test for
Corrosion Damage
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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
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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
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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
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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
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14. Instrumentation
Signals from
instrumentation
Gas 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
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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
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16. Comparison of USAF Fielded and Small
Engine 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
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17. Small Turbine Testing Results of USAF
Corrosion 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
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18. Capabilities & Benefits of Small
Turbine Testing
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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 certification
Ability to bridge the gap between specimen & full scale testing for
turbine engines
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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
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21. VEXTEC Laboratory Group Contact Info
• http://Gas-Turbine-Testing.com
• Ed Pope
– 317-750-3414 / epope@vextec.com
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