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Small Gas Turbine Testing - Fits Between Specimen & Full SCale Testing VEXTEC Laboratory Group's Small Gas Turbine Testing provides a cost-effective way of emulating many of the failure modes or other phenomena experienced in full scale gas turbine engines. By creating a similar operating environment, (high temperature and high rotating speeds), our patented rig greatly reduces test time and fuel burn by using scaled components and off the shelf JetCat P200SX engines. Our test environment has successfully recreated fatigue cracks, validated crack growth models, generated a statistically significant number of "failures" for Weibull distributions, replicated corrosion phenomena found in full scale engines and evaluated corrosion coatings, welds or other repairs and Test Instrumentation prior to installation in a full size engine. As shown in the chart on the left, small turbine testing fills the void between simplistic specimen testing & more expensive full size component & engine testing.


Failure Mechanisms

Gas Turbine Testing - Rotor Fatigue Crack

Fatigue

Fatigue can easily be achieved in the rig by increasing and decreasing RPM to vary the centrifugal stress. One cycle (idle to max to idle) can be applied in about 10 seconds. Therefore, 360 cycles can be applied in one hour, or 2,880 cycles in one 8-hour shift.
Gas Turbine Testing - Corrosion

Corrosion

Corrosion is achieved by adding contaminants into the gas strean while maintaining the proper temperature in the test stage. The damage on the left was generated by adding sulfur to the gas stream and maintaining a temperature of 300F. Our rig was used for an Air Force program that evaluated corrosion coatings
Creep Crack Growth

Creep

Creep and creep crack growth can be obtained with our rig by applying a combination of high temperature and high rotational speed to obtain high stress. The photo on the left show a creep crack in an airfoil.


Rig Design

VEXTEC Test Rig Schematic
JetCat P70 The JetCat P70 (shown at left) or the larger P200 (used when more air flow is needed) functions as the gas generator and provides the high temperature air flow needed for testing. If temperatures higher than 1700F are required, a propane fueled afterburner can be inserted directly after the gas generator to provide temperatures up to 2700F. Test articles (airfoils, rotors or blisks) are positioned behind the gas generator. An electric motor is used to control the speed of the test stage. The electric motor is capable of spinning a 10 inch diameter blisk at 50,000 RPM, which yields a tip speed of 2,200 feet per second.

Additives (such as salt or sulfur) can be injected into the gas stream ahead of the test stage to simulate harsh operating environments. If the exhaust temperatures are higher than the desired test temperature, cooling air can be brought in to bring the temperature down.


Advantages of Small Gas Turbine Testing

Comparison Chart
The advantages of scaled turbine testing are listed in the chart above. Turnaround time is quick, as detailed to the right. Missions can be very simple, as shown in the chart below, or as complex as desired. RPM and gas temperature are recorded continuously. By using a split rotor design (lower right), test airfoils can be inserted easily. This makes it easy to do "rainbow" tests, where a variety of items are tested simultaneously (Perhaps a corrosion test with uncoated blades & several blades with different anti-corrosion coatings).

Turnaround Time

  • Remove Rotor (< 1/2 Hour)
  • Item Removed from Rotor (5 Minutes)
  • Measurements / Photos Made
  • Rotor Mounted (< 1/2 Hour)
  • Total Turnaround Time < 2 Hours
Mission Disk


Downloadable Documents

Listed below are some downloadable pdf documents that describe various aspects of small gas turbine testing. Please download these & pass them on to your colleagues who might be interested.

Small Gas Turbine Testing - Overview
Small Gas Turbine Testing - Corrosion
Small Gas Turbine Testing - Salt Fog


Acknowledgements

VEXTEC would like to gratefully acknowledge the support of the Department of Defense through its SBIR (Small Business Innovative Research) program. These programs have allowed VEXTEC to develop its testing capability while supporting DOD research efforts. These test methods are protected by U.S. Patents 8006544 B2, and data rights are protected by U.S. FAR 52.227-20 and U.S. DFAR252.227-7018.

Service Contract Numbers Title Years
Air Force FA-8650-06-M-5230
FA8650-07-C-5224
Three-Dimensional Nonlinear Structural Analysis Methods for Gas Turbine Engine Metallic components and Component Assemblies 2006-2011
Air Force FA-8650-07-M-2775
FA-8650-08-C-2850
Optimal Durability and Reliability Testing of Gas Turbine Components 2007-2010
Air Force FA-8650-07-M-2767 Integrally Bladed Rotor (IBR) Sustainment 2007

To view the original 2006 video VEXTEC put together for the Air Force regarding using our rig for fatigue testing, please visit You Tube. Please note that we have made many improvements since then.

About VEXTEC

VEXTEC Corporation was founded in 2000 by Loren Nasser, Bob Tryon and Animesh Dey. They set out to develop a computational process to predict long term durability. Their software fills a gap in the existing capabilities provided by CAD/CAM, FEA, statistical modeling, and physical testing, and makes all of these disciplines more valuable. Along the way, they realized a faster and cheaper way was needed to generate test data required by their models for gas turbine components. This lead to the formation of the VEXTEC Laboratory Group. For more information about VEXTEC's software and how it can benefit your business, please visit our main web site at vextec.com.

VEXTEC Laboratory Group VEXTEC Laboratoy Group
1033 South Hunt Street
Terre Haute, IN 47803
VEXTEC - America's Most Promising Company
America's Most Promising Company
Forbes Magazine - October, 2009
E-mail
epope@vextec.com
URL
http://gas-turbine-testing.com
Phone
1-317-750-3414
Ed Pope
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