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Advanced optical smoke meters for jet engine exhaust measurementSmoke meters with increased sensitivity, improved accuracy, and rapid response are needed to measure the smoke levels emitted by modern jet engines. The standard soiled tape meter in current use is based on filtering, which yields long term averages and is insensitive to low smoke levels. Two new optical smoke meter techniques that promise to overcome these difficulties have been experimentally evaluated: modulated transmission (MODTRAN) and photothermal deflection spectroscopy (PDS). Both techniques are based on light absorption by smoke, which is closely related to smoke density. They are variations on direct transmission measurements which produce a modulated signal that can be easily measured with phase sensitive detection. The MODTRAN and PDS techniques were tested on low levels of smoke and diluted samples of NO2 in nitrogen, simulating light adsorption due to smoke. The results are evaluated against a set of ideal smoke meter criteria that include a desired smoke measurement range of 0.1 to 12 mg cu.m. (smoke numbers of 1 to 50) and a frequency response of 1 per second. The MODTRAN instrument is found to be inaccurate for smoke levels below 3 mg/cu.m. and is able to make a only about once every 20 seconds because of its large sample cell. The PDS instrument meets nearly all the characteristics of an ideal smoke meter: it has excellent sensitivity over a range of smoke levels from 0.1 to 20 mg/cu.m. (smoke numbers of 1 to 60) and good frequency response (1 per second).
Document ID
19870003396
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Pitz, R. W.
(General Electric Co. Schenectady, NY, United States)
Date Acquired
September 5, 2013
Publication Date
September 1, 1986
Subject Category
Instrumentation And Photography
Report/Patent Number
NASA-CR-179459
NAS 1.26:179459
Accession Number
87N12829
Funding Number(s)
CONTRACT_GRANT: NAS3-24084
PROJECT: RTOP 505-62-01
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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