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Small Turbine Engine Testing: Evaluate New Design Technologies

Replicate Failure in Fielded Components

Laboratory Group

http://Gas-Turbine-Testing.com

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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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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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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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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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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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Full Characterization of Small Turbine Engine

Rotating thermocouples

Strain gages

Static thermocouples

Pressure probes

Small turbine testing is fully instrumented

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Failure Mechanisms Reproduced in Realistic Operating Conditions

Fatigue crack growth

High cycle fatigue

Creep

Creep crack growth

Weld Repair

Corrosion

Creep crack along blade rootSulfide induced grain boundary cracking

Surface oxidation

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Developing an Acceptance Test for Corrosion Damage

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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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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

Gas Generator

Variable pressure bleed

Forced cooling Air

Contaminate System

Rotor Blade assembly

Motor

Drive system

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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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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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Instrumentation

Compact DAQ system

Signals from instrumentation

National Instruments Modules• Two NI9239 general purpose• One NI9233 accelerometer• One NI9211 thermocouple

Gas Generator Instrumentation• K-type thermocouple - EGT• Magnetic pickup – turbine speed• PCB accelerometers – vibratory load

Test stand Instrumentation• Vane flow meter – contaminate dosing• PCB accelerometers – belt/pulley imbalance•K-type thermocouple – rotor inlet gas temperature•VFD statistics

oMotor speedoMotor load oDrive frequency

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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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Comparison of USAF Fielded and Small Engine Tested Blades

Damage of fielded blade after 583 hours

42 µm

Damage on tested blade after 51 hours

60 µm

Test damage mechanism is same as field damage mechanism

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Small Turbine Testing Results of USAF Corrosion Test

Reproduced blade corrosion in just 60-90 days

Crack initiates in Large

damage sites

CorrosionCorrosion HCF failureHCF failure

Sulfur drives Corrosion

Corrosion at grain

boundary

Pit size is not indicative of

damage

Confirmed corrosion is the cause of initial damage

Confirmed sulfur was primary corrosion driver

Test replicated the corrosion observed in the fielded blades

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Capabilities & Benefits of Small Turbine Testing

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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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TIMELY RESULTSUseable Information in Weeks,

Not Months

COST EFFECTIVEA Fraction of the Cost of

Traditional Methods

ENGINE RELEVANTComplex Capabilities Provide

Real World Results

PRE-EMPTIVEIdentify Issues During Design

Phases, Prevent Fielded Failures

Benefits of Small Turbine Engine

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VEXTEC Laboratory Group Contact Info

• http://Gas-Turbine-Testing.com

• Ed Pope– 317-750-3414 / epope@vextec.com