Study of Technology for Detecting Pre-Ignition Conditions of ... - NIST

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CPSC-IAG95-1145
(9/16 in) inside diameter ends of 1.2 mm (3/64 in) wall thickness and 31.8 mm (1 .25 in) height,
and the support tubes were 113 cm (44.5 in) long. The probe end was located approximately
36 cm (14 in) above the burner surface and centered above the pan. Since most velocity
measuring instruments are hindered by particle-laden flows, a hi-directional probe was
implemented because of its ability to perform in smoke-laden flows such as are produced by prefire
and fire conditions.6 The probe was connected to a Setra model 264 pressure transducer for
which the range was +J4.9 Pa (M. 1 inches of water) with an output of 2.5 Vdc for zero
differential pressure and 10 Pa/Vdc sensitivity. The transducer excitation was accomplished with
a Setra model 2195 regulated 12-28 Vdc power supply.
2.2.4 Fourier Transform Infrared Spectrometer
The spectrum clf major gas species above the cooking area was measured using an openpath
Fourier transform infrared spectrometer (FTIR). A MIDAC Corporation Model M2501-C
detector and Model M2402-C source were placed approximately 1.6 m (63 in) apart with the
burner of interest approximately centered between them. The two units were positioned at a
height such that the center of the 3.8 cm (1.5 in) diameter infrared beam passed through the
center axis of the pan approximately 15 cm (6 in) above the burner surface. The spectrometer
spectral resolution wax set to 4 cm- 1. Each set of sixty-four spectra was signal-averaged over
20 seconds to provide each data point.
2.2.5 Infrared Video
& infrared video camera was used to obtain thermal imagery of the cooking environment
over time so comparisons could be made of maximum temperatures and temperature gradients
in the period preceding ignition. The camera used was an Inframetrics model 525 camera and
power supply. It was connected to a Canon VR-20 portable video recorder and a JVC TM-22U
color video monitor. The camera was directed from an angle approximately 20° above the
horizontal plane of the burner and was located at sufficient distance to focus on a view that
included the burner, pan, some of the food, about 15-20 cm (6-8 in) on each side of the pan, and
about 25 cm (10 in) above the pan. The area framed by each image was about 56 cm (22 in)
wide by 39 cm (15 in) tall. The videotapes were reviewed, and individual Ill image frames were
digitally analyzed at 1 second, 45 seconds, and 90 seconds before ignition.
Two blackbody sources were utilized for calibration of the infrared video images. The
Mikron model M-310 source was set at 300 “C, and the Barnes Engineering source was set at
511 “C. The Mkron source provided a continuous readout of the temperature, but a Fluke model
52 IUJ thermometer was necessary to monitor the Barnes Engineering source while recording the
calibration video.
2.2.6 Standanl Video and Photographic Equipment
A VHS video tamer% Panasonic AG-170 Proline, was approximately centered outside of
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