Gas Turbine Technology Testing
Full-scale gas turbine technology testing engines are quite expensive and require a lot of fuel to operate. Therefore, it has been looking for a cheaper method to simulate the gas turbine technology testing environment for gas turbine testing for a long time. In 2006, VEXTEC submitted a proposal for the SBIR program to the Air Force, and the proposal was accepted. info technology hub The VEXTEC method uses a Jet Cat P70 turbine engine. These COTS (commercial, ready-to-use) turbine technology testing are small, about 4 inches in diameter, about 1 foot in length, and weighing several pounds. They are usually use by very serious remote-control aircraft enthusiasts. Since these motors cost thousands of dollars instead of millions of dollars for full-size motors, they may fail. They have a single-stage radial compressor and a single-stage axial turbine technology testing made of Inconel 713.
Small Turbine to Propagate Fatigue Cracks Technology:
In the initial plan, VEXTEC hopes to use this small turbine technology testing to propagate fatigue cracks when the crack path is not obvious. The rotor of the integral blade axial turbine technology testing has 23 aerodynamic blades. In order to obtain as much data as possible, 8 notches were machine radially on the rotor between the airfoils. These spaces serve as crack initiation points and the crack propagation path will be monitored.
There are two possible paths: The crack can rotate and grow tangentially below the adjacent airfoil and free it from the rest of the technology testing rotor. The crack may continue to propagate radially inward until the rotor splits into two or more major parts. VEXTEC can initiate and enlarge cracks by applying a full idle cycle to the engine. The turbine technology testing engine can accelerate from an idle RPM of 35,000 to a maximum RPM of 125,000 in four seconds.
VEXTEC Stops Gas Turbine Technology Testing at Approximately 300 Cycle Intervals:
It takes 6 seconds to decelerate back to 35,000 RPM, so a full cycle can be applied in 10 seconds. This allows to apply more than 300 cycles per hour. VEXTEC stops gas turbine technology testing at approximately 300 cycle intervals, so all eight cracks can be traced. One of the cracks grew tangentially and release an airfoil after just over 1000 cycles.
After the initial SBIR procedure successfully produce fatigue cracks, the next SBIR procedure attempted to use the small motor method to generate creep (elongation due to continuous application of high temperature stress over time) in the aerodynamic surface of the turbine technology testing rotor. The procedure had only limited success because the temperature was not as high as required to obtain significant creep deformation. A later project from attempted to use our small turbine technology testing method to test anti-corrosion coatings.
Using a Jet Cat Turbine to Generate a Flow of Hot Air and Using an Electric Motor: Turbine Technology Testing
For this project, VEXTEC came up with the idea of using a Jet Cat turbine technology testing to generate a flow of hot air and using an electric motor to rotate the test object behind it. This method has two advantages: test objects do not have to be streamline, they can be simple flat “paddle wheels”. This makes gas turbine technology testing easier and cheaper. Contaminants can be introduce directly into the airflow behind the engine to better simulate the corrosive environment.
For corrosion coating processes, sulfur is mix with water and inject into the gas turbine technology testing stream. Use this method. VEXTEC can simulate 5000 hours of corrosion in the field during a 300 hour test. After establishing this baseline, three different anti-corrosion coatings were tested and evaluated. To further increase the temperature range that can be simulate by small turbo-drills, VEXTEC has develop an afterburner that can be insert into the rear of the engine.