Spectroscopic Methods and Visualization Applied to Combustion Diagnoses - Novel Combustion Concepts for Sustainable Energy Development - page 172

In addition, spatial distributions, or pro les of these parameters, and their temporal

changes are very important for unraveling combustion phenomena and improving
the system ef

ciency and suppressing toxic emission.
For this purpose, measurement methods are inevitable for monitoring spatial
distributions of temperature and intermediate chemical species in fl flames during

combustion.
Spectroscopic methods and 2D visualization are powerful and promising tools to
meet the requirement described above. In this chapter, several different spectro-
scopic methods and visualizations, and their applications to combustion systems
will be described. The spectroscopic applications here include spontaneous optical
molecular emission spectroscopy or spectrometry (OMES or MES), planar laser-
induced fluorescence spectroscopy (PLIF), and laser ionization mass spectrometry

(LI-MASS).

fl

1.1 Spontaneous Emission Spectroscopy and Visualization
and Application to Ecological Industrial Furnace
High-Temperature Air Combustion (HITAC)
(Hino et al. 2004 ; Shimada et al. 2005 )

Flames are chemical reaction fields to maintain high temperatures and excite

chemical species to higher energy levels. Consequently, the excited species, or
molecules, and atoms emit spontaneously radiation when they return to their stable
lower or ground states. In other word,

flames at high temperatures are regarded as
thermal excitation source and have been used for

fl

flame photometry for trace analyses
of alkali elements, alkaline elements, sulfur, phosphorus, etc. On the other hand,
spontaneous emission from intermediate chemical species such as OH, CH, and C 2
gives us useful information for combustion conditions. Gray body emission from
soot in combustion

fl

flame temperatures spectroscopi-
cally. Since the measurement systems for spontaneous emission spectrometry, or
molecular/atomic emission spectrometry, simply consist of a converging lens and
spectrometer, they are suitable for on-site measurements of, e.g., industrial furnaces.
When the spectrometer is replaced by a spectro-camera (Kubota et al. 1998 ),
a monochromator or an optical bandpass

fl flames enables us to measure fl

filter attached to a CCD camera, spatial
resolution of spectral information becomes available. Furthermore, a spectro-video
camera is used instead, and time resolution is given. Thus, we can obtain spectral,
spatial, and time resolutions. In this chapter, such a systems were applied to mea-
surements of combustion temperatures and chemical species during combustion in a
regenerative industrial furnace used for reheating of steal slabs. The furnace is based
on a high-temperature air combustion technology, enabling us to save energy con-
sumption up to 30 %, leading to less CO 2 emission. This new type of combustion
had not been unraveled in conjunction with temperature uniformity and low NO x
emission.