Emissions and Soot in Partially Premixed Combustion - Novel Combustion Concepts for Sustainable Energy Development - page 440

tangential slots and flame holder. The

perforated plate used has a circumferential row of 32 holes, with each hole of
diameter 2 mm. There is another circumferential row of 24 holes, of 2 mm diameter
each, just beneath the perforated plate. This is to facilitate proper ventilation and
cooling of the burner, as well as to ensure proper secondary air supply to the
reaction zone without any choking.
The diffusion or secondary or the main combustion air passes through a separate
supply line to the burner, and comes out of the holes in the perforated plate, on the
outside of the

finally comes out through the centre of the fl

flame holder. A cylindrical Quartz glass tube (length 400 mm, inner
diameter 60.3 mm, thickness 3 mm) acts as the combustion chamber and is placed
around the burner. The chamber is open to the atmosphere at the top. Glass is used
as it is needed for optical access during videography and imaging of the

fl

ames, and
quartz is preferred as it can withstand the high temperatures occurring during
combustion without shattering or bending.
For taking measurements, the probes for the emission analyser, the LII as well as
the thermocouple were inserted one by one, into the centre of the glass chamber
from the top, with the probe tip at a distance of 190, 32 and 305 mm, respectively,
as measured from the top of the glass chamber.
Temperature measurements were taken using a K-type thermocouple (with an
accuracy of

fl

± °

C, with a digital indicator). The thermocouple was
placed vertically inside and in the centre quartz tube combustor at a distance of
305 mm, measured from the top of the glass.
Emissions were measured using an AVL Ditest 444 gas analyser set for LPG.
The exhaust gases, the concentrations of which were recorded, were Carbon
monoxide (CO), Carbon dioxide (CO 2 ), Oxides of Nitrogen (NO x ) and Unburnt
Hydrocarbons (UHCs). The probe was positioned at the centre inside the glass
chamber, at a distance of 190 mm from the top of the glass. The position was
decided such that the probe was able to suck the

0.7 % and 1

fl flue gases properly. That is why it

was decided to keep the probe at the ame.

Measurements of soot primary particle size, soot volume fraction and soot mass
concentration were done through the LII 300 instrument manufactured by Artium
Technologies. The probe was inserted into the centre of the glass chamber, at a
distance of 32 mm from the top of the glass. The probe was connected to an
external vacuum pump, which sucked the sample from the probe tip and pumped it
to the LII unit.

fl flame tip of the tallest fl

3 Results and Discussions

For a pure diffusion fl flame, at the set fuel fl flow rate of 0.0254 g/s, the fl ame was deep

yellow ame was narrow, and had a

small bluish component towards the left side. This blue component could be
attributed to the effect of swirling, which promoted complete combustion in that
region. Also, as seen in the photograph taken of the

- orange in colour, with a signi cant height. The fl

fl flame holder (Fig. 4 ) after