Thin-Filament Pyrometry in Flickering Laminar Diffusion Flames.
Thin-Filament Pyrometry in Flickering Laminar Diffusion
Flames.
(1243 K)
Pitts, W. M.
Combustion Institute, Symposium (International) on
Combustion, 26th. Proceedings. Volume 1. July
28-August 2, 1996, Napoli, Italy, Combustion Institute,
Pittsburgh, PA, 1171-1179 pp, 1996.
Keywords:
combustion; diffusion flames; flickering flames;
methane; temperature measurements; thermal radiation;
thin filament pyrometry
Abstract:
This paper describes an experimental system for
thin-filament pyrometry (TFP) in acoustically
phase-locked flickering laminar methane/air diffusion
flames. The physical basis of the technique is
discussed. The experiment utilizes a 15-mu m beta-SiC
fiber, which is simultaneously imaged at 540 points over
a length of 27.5 mm using a cooled CCD camera. This
arrangement provides measurements over a 1200-2100-K
temperature range having a spatial resolution of ~100 mu
m, a temporal resolution of 1.5 ms, and a precision of
1.5 + 1.0 K for temperatures on the order of 2000 deg.
K. The TFP is calibrated assuming that the strongest
filament emission at a height 7 mm above the burner for
a steady laminar flame corresponds to a temperature of
2000 deg. K. Temperatures at different positions along
the filament are then determined by recording relative
emission intensities and assuming that the filament acts
as a gray-body emitter. Measured filament temperature
profiles are found to be in good agreement with earlier
radiation-corrected thermocouple results by Richardson
and Santoro for the same steady laminar flame. The
calibrated TFP is then used to make filament temperature
measurements at various heights and phases of a
previously studied flickering flame entering a
low-velocity air flow. The use of a two-dimensional CCD
allows a baseline to be determined, and measurements can
be made in the presence of background luminosity, which
is observed in sooting regions. In order to demonstrate
the effectivenss of the approach, measurements are
well-characterized flame for calibrating TFP is
discussed. Knowledge of flow velocities and molecular
composition in both the calibration and flickering
flames is required to improve the accuracy of flame
temperature measurements using TFP.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899