LWB2-3 / 205

ee

_/

Hl |
Military,
vehicle

Figure 1: Schematic of experimental setup for measurement of combustion species

Inhibitant reservoir

1

Detector signal out |

produced during suppressant testing on board military vehicles.


1998 Laser Applications

ae to Chemical and

Volume 3 Environmental
Analysis

Technical

Digest

March 9-11. 1998

Sheraton World Resort Orlando
Orlando, Florida

Conference Edition

OSA Sponsored by the Optical Society of America
‘NX. in cooperation with the Laser Institute of America

Optical Society of America


LWB2-1/ 203

Near -Infrared Tunable Diode Laser Diagnostics in Laboratory and Real-Scale
Inhibited Flames

Kevin L. McNesby, Robert G. Daniel, R. Reed Skaggs, and Andrzej W. Miziolek
U.S. Army Research Laboratory
Craig S. Miser
U.S. Army Aberdeen Test Center
Aberdeen Proving Ground, MD 21005

The goal of this research project is to develop and demonstrate/validate new
laser-based instrumentation for the measurement of concentrations of candidate
suppressants, oxygen, fuels, and combustion byproducts during suppression of flames and
explosions. Time resolved measurement of concentrations of suppressants, oxygen, fuels,
and combustion byproducts serve as a check on the repeatability of the tests and help

determine why a suppressant is behaving well or poorly in a given full-scale suppression

test.

The approach used in the investigation of gas species produced during suppression
of crew and engine compartment fires involves a close interaction between laboratory
based combustion diagnostics facilities currently in place at ARL and similar, ruggedized,
facilities in place at ATC. Instrument utility, response, and quantitative calibration are
performed at ARL prior to application of a particular technique to large
scale fire scenarios. This protocol has been used successfully for the quantification of HF

gas produced during chemical inhibition of JP-8 fuel pool fires’.


204 / LWB2-2

Key benefits to implementation of laser-based sensing devices derive from real-time
sensing and the ability to use multiple sensors from a single laser source. Real time
sensing is important because it provides information on how and at what rate fuel and
oxidizer are consumed, the time required following agent release for suppressant to be
effective, and the rate at which toxic gases are produced during a suppression event.
Typically, fire suppression on-board military vehicles is accomplished within 250
milliseconds of fire detection. Gases measured using NIRTDL absorption spectroscopy
include HF, CO, CHy, O2, NO2, and HO. Use of multiple sensors, enabled because the
lasers and detectors are fiber coupled, is required because of the need to know how well a
given agent suppresses a fire at different locations within the vehicle. Together, the use of
real-time sensing and multiple sensor measurement provide a means to judge why a

suppressant behaves the way it does in different fire scenarios.
Examples will be presented of NIRTDL absorption spectroscopy of several gases

in laboratory-scale, atmospheric pressure opposed flow flames and in full scale testing on

board military vehicles (see Figure 1).

1. Applied Optics, vol. 35, p4004 (1996).