Combustion Phenomena of High Temperature Air Combustion - High Temperature Air Combustion: From Energy Conservation to Pollution Reduction - page 37

Firing Description Side 'A' Firing Side 'B' Firing

F1 F1

Mode I
Fuel/Air Mixed Flow

E E

A A

A side B side A side B side

F2 F2

Mode II
Fuel/Air parallel Flow

A E E A

F2 F2

F2 F2

Mode III
Fuel/Air counter Flow

E E

A A

F2 F2

F: Fuel injection , A: Preheated combustion air, E: Cold exhaust gas

FIGURE 2.9 Fuel-air nozzle confi gurations.

Temperature, C Temperature, C Temperature, C

1200 1200

1200

1100 1100 1100

1000 1000 1000

900 900 900

3.8 3.8 3.8

2.85 2.85 2.85

1.9 1.9

1.9

L/W L/W 0 L/W 0

0

0.95 0.95 0.95

0.0 0.0 0.0

0.5 0.5 0.5

0.5 0.5

0.5

W W W

(a) Mode I (b) Mode II (c) Mode III

Fuel/Air mixed flow Fuel/Air parallel flow Fuel/Air counter flow

FIGURE 2.10 Temperature distribution averaged over one switching cycle in 350 kW-scale
test rig.

and CO emissions for Mode I were 213 and 16 ppm, respecti vely, at 11% O

2

correction, whereas the y were both 15 ppm in Mode II. In Mode III, NO and CO

x

emission levels were 13 and 17 ppm, respectively, which is very similar to the Mode
II performance.
In these combustion tests, the average temperature of the preheated air reached
1150˚C when the average flue gas temperature was 1250˚C in the test rig. This
temperature was obtained by using the high-cycle switched regenerator with 30 s
switching time. The air side temperature efficiency for this condition was 91%, and
the efficiency of the waste heat recovery was 77%. These results demonstrated that
significant energy saving can be attained by introducing the high-cycle regenerator.