Combustion Phenomena of High Temperature Air Combustion - High Temperature Air Combustion: From Energy Conservation to Pollution Reduction - page 39

2.2.3 F LAME S TRUCTURE , R ADICALS , AND S PECIES

2.2.3.1 Experimental Furnace for Optical Measuring

The optical measuring method was applied to the combustion flame in the high
temperature air formed in a small regeneration furnace with almost the same structure
as the actual furnace. A regenerative test furnace was made in which openings for
optical measuring were arranged at the upper, lower, and side parts of the furnace.
Its external appearance is shown in Figure 2.12 a nd its specifications in Table 2.1 .
The inside of the furnace is a 1 m square regular cube. The fuel used was city gas
13A or LPG, and four burners were arranged, two pairs of which were on combustion
alternating every 30 s. The layout drawing of holes for the preheated air and fuel
nozzles is shown in Figure 2.13 . The combustion rate when using the 13A fuel was
58 kW/pair at maximum, and the in-furnace temperature was raised to 1300˚C at
maximum. A quartz glass was set up for each opening at the side part in order to
observe the inside of the furnace, and to each opening at the lower part of the furnace
for irradiating the laser beam. Up to the in-furnace temperature of 850˚C, the fuel
and air were mixed within each burner to carry out concentrated combustion (F1
mode), and at a temperature higher than 850˚C, distributed combustion (F2 mode)
was practiced to enable operation of the test furnace.

2.2.3.2 Combustion Conditions

A schematic diagram of the laser induced fluorescence (LIF) measurement experi-
ment is shown in Figure 2.14 . The airflow velocity, the fuel jet velocity, and the fuel
jet angle were changed to generate combustion flames with different concentrations
of exhaust NO x , which were the objects to be measured. Table 2.2 shows the
conditions for measurement. All the conditions were unified on the basis of fuel
13A, air ratio 1.2 (airflow rate 52

m 3 m 3

/h, fuel flow rate 4 /h), and in-furnace

CCD camera

Windows for measuring
the in-furnace

FIGURE 2.12 Combustion test furnace to be measured.