Fire Suppression Research Papers - Academia.edu (original) (raw)

The combustion of kerosene spray under hot-diluted conditions and
conventional conditions was experimentally investigated. By examining
flame photographs, chemiluminescence images, and in-field temperature
measurements, the separate effect of different variables
including oxygen concentration, temperature and velocity of the coflowing
air, fuel flow rate and injection pressure, and eventually the
type of spray nozzle on multiple parameters such as flame stability,
structure, luminosity, temperature field, and qualitative CH radical
distribution, as well as HCO and NO2 with lower precision, in the
reaction region, have been studied. It was observed that an increment
in injection pressure and co-flow temperature enhances the spray
flame stability, while dilution exacerbates it. Also, a solid cone spray
pattern with a lower spray angle has better stability than hollow cone
ones with a higher spray angle. Moreover, it was noted that liquid
fuels, compared to gaseous fuels, require higher preheating temperatures,
for the same dilution level, to engender a stable flame. For
combustion of spray in conventional conditions, a double-flame structure
was observed consisting of a bluish section at the leading edge
emerging into a yellowish sooting trail. An increase in co-flow velocity,
as well as injection pressure, strengthens the inner flame front,
whereas raising the co-flow temperature or diluting the oxidant, deteriorates
the inner flame front. In the case of highly preheated air
(without dilution), the flame liftoff height is reduced to as close to
the atomizer as a few millimeters, forming a single flame structure
similar to gaseous flames. In this case, the peak temperature was
considerably higher than the conventional combustion, yet the gain
was much lower than the preheating level. Combined effects of preheating
and dilution alter the spray flame structure in a way that the
flame volume is reduced, the temperature field has become more
homogeneous, the peak temperature is limited to less than 1500 K,
and temperature fluctuations have significantly decreased, seemingly
approaching MILD combustion regime conditions.