Combustion Phenomena of High Temperature Air Combustion - High Temperature Air Combustion: From Energy Conservation to Pollution Reduction - page 47

285mm 100 285mm

Fue l

Air

Fue l

FIGURE 2.21 OH distribution, condition (e), upstream and downstream of flame.

combustion flame that produces a low NO x combustion, the EGR in the vicinity of
the burners is small, but the airflow is diluted by the EGR at the lower portion of
the flame stream, to become an airflow with a low oxygen concentration, and low
NO x combustion is attained since no domain at a high temperature is locally formed.
Further, the authors carried out PIV (particle image velocimetry) measurement
in the vicinity of the burners under condition (c) (fuel parallel jetting) and condition
(d) (fuel oblique jetting) for distributed combustion, as shown in Table 2.2 , with a
view to measuring the difference of the in-furnace flow according to the fuel jetting
conditions. A twofold wave of Nd:YAG lasers emitting from two machines was used
as the light source, and the time difference between two laser pulses was set at 10
µs. Such laser beams as formed in a sheet-shape were radiated into the furnace, to
obtain two images from their scattered light. At that time, tracer grains of SiO 2
(average grain diameter: 2.7 µm, apparent specific gravity: 0.45 g/cm 3 ) with enough
heat resistance even in the flame were seeded into the 13A fuel, and the measure-
ments were carried out in a combustion state at an in-furnace temperature of 950˚C.
The results obtained are shown in Figures 2.22 and 2.23 .

140mm

Air

Fuel

PIV result Direct photograph

FIGURE 2.22 Results of measuring the in-furnace flow by PIV, condition (c), in-furnace
temperature 950˚C.