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Loss of frequency response along sampling tubes for the measurements of gaseous composition at high temperature and pressures

Published online by Cambridge University Press:  26 April 2006

Ronald Smith
Ronald Smith
Affiliation:
Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW, UK
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Abstract

Measurements of the rapidly changing gaseous composition in engines at low speed can be made via narrow tubes which convey the gases to monitoring equipment in a less hostile environment. This paper quantifies the extent to which the tube smooths out any changes in concentration. Exact (and approximate) formulae are derived for the temporal variance as weighted double (and single) integrals of the steady flow properties along the tube. Such is the non-uniformity that typically the region near the engine contributes 100 times as much to the spreading as does the region near the monitoring equipment. The advantages of keeping the sampling tubes short and heated are made explicit.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 208 , November 1989 , pp. 25 - 43
Copyright
© 1989 Cambridge University Press

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