AEDC camera assists in turbine tests
By Darbie Sizemore
/ Published May 02, 2007
ARNOLD AIR FORCE BASE, TENN --
A periscope camera on loan from Arnold Engineering Development Center (AEDC) provided images of a Williams International full annular turbine engine augmentor rig during recent testing in the first of several different augmentor concepts at the Air Force Research Laboratory (AFRL) at Wright-Patterson Air Force Base, Ohio.
The camera provided visuals of the augmentor flame zone in areas of concern that otherwise would not have been known. "The use of the periscope camera provided a great deal of information on the flame location and propagation in the rig, along with visual access to witness light-off of the augmentor - something that would have been difficult to detect otherwise," said Dr. Joe Zelina, senior research engineer for the AFRL Combustion Branch.
The camera assembly, enclosed by a water cooled periscope, was mounted through the augmentor casing, providing an unobscured view of a sizeable section within the augmentor during testing. Although this is not the first time an augmentor camera has been used, previous generation cameras were located far downstream of the engine exit plane. While these cameras provided a good general view of the augmentor, they were unable to focus in on areas of interest within the augmentor.
Furthermore, intervening facility cooling water sprays obstructed the views from these cameras.
"The new generation augmentor camera probes are mounted directly at the exit plane of the engine and provide the capability to focus on particular regions of the augmentor," said Dr. Robert Hiers, ATA technical fellow for instrumentation and diagnostics technology. "In addition, the new generation of augmentor camera probes is relatively portable, requiring minimal penetration into the facility, whereas the older augmentor cameras require a large penetration and a large support structure. These features all allowed an AEDC camera probe to be installed at the AFRL facility, which has no augmentor camera capability of its own."
Typically during testing, the augmentor is instrumented to provide various diagnostic measurements - temperatures, pressures and flow rates. Even though these data give extremely useful quantitative information, thermocouples for instance can only sense temperature at predetermined locations. A camera view gives an immediate qualitative visual indication of the core combustor and hot spots throughout the augmentor. Additionally, the camera reveals important aspects of the flowfield within the augmentor, such as ignition, flameholding, flame proportioning, intensity and structure in the tailcone recirculation zone.
"From a safety standpoint, this technique can be used to observe metal surfaces and areas of thermal stress during testing that potentially could prevent hardware failure," said Dale Shouse, senior research engineer, AFRL Combustion Branch. "Using this device to evaluate and compare the combustion system concepts will provide great insight into the operation of these advanced concepts and is a must for future testing in all combustor and augmentor rigs."
AEDC has arranged to provide an advanced cooled periscope camera concept design to AFRL for future research.
The Williams rig is being developed in support of a U.S. Air Force/Defense Advanced Research Project Agency (DARPA) program for the Turbine Engine Division of the Propulsion Directorate at the ARFL.