Emissions and Soot in Partially Premixed Combustion - Novel Combustion Concepts for Sustainable Energy Development - page 444

Fig. 9 Variation of NO
concentration with premixing
equivalence ratio

Normalized NO

0.8

0.6

0.4

0.2

0.0

1 2 3 4 5 6 7 8 9

Φ

p

Fig. 10 Variation of soot
concentration with premixing
equivalence ratio

6

Normalized Soot Mass Concentration

5

4

3

2

1

0

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Φ

p

increase in soot production. However, for higher degree of premixing, soot particles
start to get oxidized resulting in a decrease in soot concentration and beyond
Φ p = 3.77, the soot is almost completely eliminated.
The primary soot particle size for the set of premixing conditions considered for
this study varied between 9 and 28 nm approximately as shown in Fig. 11 . Initially,
as the premixing air was increased, the particle size remained almost constant up to
around Φ p = 5 and beyond that an increase in particle size is observed till

Φ p = 3.32. Similar tends in CO and UHC concentrations were observed in Figs. 7
and 8 which implies that during the incomplete and improper combustion, which
resulted in higher concentrations of CO and UHC, the soot particles might have
agglomerated to form larger size particles.
An interesting area for further study is measurements of pressure oscillations in the
combustor that can be correlated with sound vibrations in order to analyse the impact
of partial premixing on the acoustic characteristics of the system. Problem areas like