Abstract

This work presents the development of an optical setup for quantitative, high-temporal resolution line-of-sight extinction imaging in harsh optical environments. The application specifically targets measurements of automotive fuel sprays at high ambient temperature and pressure conditions where time scales are short and perceived attenuation by refractive index gradients along the optical path (i.e., beam steering) can be significant. The illumination and collection optics are optimized to abate beam steering, and the design criteria are supported by well-established theoretical relationships. The general effects of refractive steering are explained conceptually using simple ray tracing. Three isolated scenarios are analyzed to establish the lighting characteristics required to render the observed radiant flux unaffected by the steering effect. These criteria are used to optimize light throughput in the optical system, enabling minimal exposure times and high-temporal resolution capabilities. The setup uses a customized engineered diffuser to transmit a constant radiance within a limited angular range such that radiant intensity is maximized while fulfilling the lighting criteria for optimal beam-steering suppression. Methods for complete characterization of the optical system are detailed. Measurements of the liquid–vapor boundary and the soot volume fraction in an automotive spray are presented to demonstrate the resulting improved contrast and reduced uncertainty. The current optical setup reduces attenuation caused by refractive index gradients by an order of magnitude compared to previous high-temporal resolution setups.

© 2017 Optical Society of America

Full Article  |  PDF Article
OSA Recommended Articles
Diffuse-light two-dimensional line-of-sight attenuation for soot concentration measurements

Kevin A. Thomson, Matthew R. Johnson, David R. Snelling, and Gregory J. Smallwood
Appl. Opt. 47(5) 694-703 (2008)

Forward-illumination light-extinction technique for soot measurement

Yi Xu and Chia-fon F. Lee
Appl. Opt. 45(9) 2046-2057 (2006)

Two-dimensional imaging of soot volume fraction in laminar diffusion flames

David R. Snelling, Kevin A. Thomson, Gregory J. Smallwood, and Ömer L. Gülder
Appl. Opt. 38(12) 2478-2485 (1999)

References

You do not have subscription access to this journal. Citation lists with outbound citation links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Cited By

You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Figures (13)

You do not have subscription access to this journal. Figure files are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Equations (9)

You do not have subscription access to this journal. Equations are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription