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Real Time Thermal Imaging Capability for Propulsion Systems

Description:

OBJECTIVE: Develop a low-cost portable real-time infrared imaging and visualization capability for high speed turbine and internal combustion (IC) engine components to improve inspection capability and enhance engine life cycle management. 

DESCRIPTION: Small Turbine and IC engine designs employing novel combustion features, advanced thermal materials, and high speed components impose challenges on collecting appropriate data for analysis and evaluation in situ. Large turbine maintenance evaluation of critical components is accomplished with visual inspection using a bore-scope through case access points or through the back of the engine at scheduled intervals. More detailed capability to determine the state of health of the turbo-machinery components is needed to push reliability improvements and accommodate new requirements for achieving condition based maintenance plus (CBM+) goals. Applications of this capability to uninstalled engines in the test cell is desired. Current state-of- the-art (SOA) optical IR imaging used in aerospace component demonstration, test and evaluation is fragile, costly, and limited in ability to capture/process imaging phenomenon (visible and hidden defects, cooling effectiveness) in real time. Commercial industrial imaging includes real time process monitoring (metals, furnaces, plastics, semiconductors), safety, and product performance where the optics and electronics are at ambient conditions. Most military applications to date are for long range imaging, surveillance, and data collection. Immediate (real-time) availability of the imaging data is important for operator efficiency and decision analysis. SOA technology is limited to large low speed, ground based (power generation) turbines where high cost sensing systems are justified. Processing is typically accomplished off line where there are no hardware and time constraints. No suitable solutions are available for aero ground engines in test cell applications. Development of a multi-wavelength short (0.9-1.7 micron) or mid-band (1.5-5 micron) imaging capability using electronically scanned detectors, no cooling, and a robust ability to operate in a shop or flight line environment (above 150 F) is desired to enhance performance and reduce cost of engine maintenance. The imaging capability must have the ability to scan in a limited space and tight access such as borescope locations. This capability must accommodate rotor rotation frequencies over 500 Hz with imager integration times below 500 nanoseconds and high pixel rates. Extracting a thermal 2-dimensional profile of the turbine blades along with a 3-dimensional point map showing blade deflection is desired. The technique should be able to accommodate inspection and detection of blade coating artifacts. The IR detectors (cameras, arrays, sensors) that operate at ambient temperature or above, are a significant cost, operability, and usability benefit compared to IR detectors that require cooling to liquid nitrogen (-196 degrees C) temperatures. An IR and visible thermographic approach is an NDE technique that can also be especially useful in finding precursors to flaws and damage in composite aerospace structures. Active IR imaging (natural excitation) also closes the gap for testing the near surface region between the surface and moderate depths of structural elements. Identification of the feature domain of the components imaged as part of the design will potentially reduce the need for extensive high speed computation. 

PHASE I: In the Phase I program, a prototype concept will be designed that meets imaging capture speed, flexibility, robustness, and real time performance goals of the topic. Suitable laboratory tests will be performed to verify the concept can be implemented for flight line and real-time applications. 

PHASE II: In Phase II, relevant hardware will be refined and fabricated based on the Phase I design and testing. Demonstration of the flight line and real-time capability will be performed with a state-of-the-art or legacy engine bench test. Operational limitations and capability will be documented as well as applicability to a wide family of engines. 

PHASE III: In Phase III, implementation issues documented with Phase II will be addressed and a fielded design will be developed that meets the depot or aircraft technical and operational requirements. 

REFERENCES: 

1: Markham James, et al., "Aircraft engine-mounted camera system for long wavelength infrared imaging of in-service thermal barrier coated turbine blades", Review of Scientific Instruments, Vol. 85, Issue 12, December 2014.

2:  Thurner, Thomas,"Real-Time Detection and Measurement of Cracks in Fatigue Test Applications", AMA Conference 2015, - SENSOR 2015 and IRS2 2015.

3:  Lindgren Eric and Buynak Charles, "Materials State Awareness for Structures Needs and Challenges", 12th International Symposium on Nondestructive Characterization of Materials, Blacksburg, VA., June 2011.

KEYWORDS: Real Time, Optical Imaging, State Awareness, Flaw Detection, Flight Line Maintenance, Diagnostics, Harsh Environment, Turbine Engine 

CONTACT(S): 

Kenneth Semega 

(937) 255-6741 

kenneth.semega@us.af.mil 

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