NTRS - NASA Technical Reports Server

Back to Results
Advanced Optical Diagnostics for Ice Crystal Cloud Measurements in the NASA Glenn Propulsion Systems LaboratoryA light extinction tomography technique has been developed to monitor ice water clouds upstream of a direct connected engine in the Propulsion Systems Laboratory (PSL) at NASA Glenn Research Center (GRC). The system consists of 60 laser diodes with sheet generating optics and 120 detectors mounted around a 36-inch diameter ring. The sources are pulsed sequentially while the detectors acquire line-of-sight extinction data for each laser pulse. Using computed tomography algorithms, the extinction data are analyzed to produce a plot of the relative water content in the measurement plane. To target the low-spatial-frequency nature of ice water clouds, unique tomography algorithms were developed using filtered back-projection methods and direct inversion methods that use Gaussian basis functions. With the availability of a priori knowledge of the mean droplet size and the total water content at some point in the measurement plane, the tomography system can provide near real-time in-situ quantitative full-field total water content data at a measurement plane approximately 5 feet upstream of the engine inlet. Results from ice crystal clouds in the PSL are presented. In addition to the optical tomography technique, laser sheet imaging has also been applied in the PSL to provide planar ice cloud uniformity and relative water content data during facility calibration before the tomography system was available and also as validation data for the tomography system. A comparison between the laser sheet system and light extinction tomography resulting data are also presented. Very good agreement of imaged intensity and water content is demonstrated for both techniques. Also, comparative studies between the two techniques show excellent agreement in calculation of bulk total water content averaged over the center of the pipe.
Document ID
Document Type
Conference Paper
Bencic, Timothy J.
(NASA Glenn Research Center Cleveland, OH, United States)
Fagan, Amy
(NASA Glenn Research Center Cleveland, OH, United States)
Van Zante, Judith F.
(NASA Glenn Research Center Cleveland, OH, United States)
Kirkegaard, Jonathan P.
(Jacobs Technology, Inc. Cleveland, OH )
Rohler, David P.
(Plexar Associates, Inc. Shaker Heights, OH, United States)
Maniyedath, Arjun
(Plexar Associates, Inc. Shaker Heights, OH, United States)
Izen, Steven H.
(Case Western Reserve Univ. Cleveland, OH, United States)
Date Acquired
January 29, 2014
Publication Date
June 24, 2013
Subject Category
Air Transportation And Safety
Report/Patent Number
Meeting Information
Atmospheric and Space Environments Conference(San Diego, CA)
Funding Number(s)
WBS: WBS 648987.
Distribution Limits
Public Use Permitted.
No Preview Available