Introduction - High Temperature Air Combustion: From Energy Conservation to Pollution Reduction - page 7

emperature history of heat-recirculating combustion of premixed reactants in
one-dimensional adiabatic system.

FIGURE 1.1 T

the cases with and without heat recirculation. The maximum temperature in heat-

recirculating combustion is determined by the amount of recycled heat that is
independent of the equivalent ratio of the mixture or the calorific value of the fuel
used. This is certainly true for premixed combustion in adiabatic condition. Accord-
ingly, it has been held that heat-recirculating combustion brings a temperature rise
throughout combustion processes in proportion to the amount of recycled heat.
At normal ambient temperature, an ordinary hydrocarbon gaseous fuel mixed
with atmospheric air exhibits a combustible domain around the stoichiometry, and
an increase of temperature of the mixture expands the combustible limits signifi-
cantly, as illustrated in Figure 1.2 .

10

A large increase in the temperature may cause

FIGURE 1.2

Flammable domain e xpressed by calorific value of fuel, Q , initial temperature

f

of mixture, T , and mixture equi valence ratio, φ .

i