Using Petroleum and Biomass-Derived Fuels in Duel-fuel Diesel Engines - Novel Combustion Concepts for Sustainable Energy Development - page 249

= 3, pressure = 1 atm, and strain rate = 200 s − 1 , using the Chemkin software and
GRI-3.0 mechanism. For all

ϕ

ame
structure with a RPZ located on the fuel side (at about 0.9 cm from the fuel nozzle)
and a NPZ on the oxidizer side near the stagnation plane (at about 1.05 cm from the
fuel nozzle). These two reaction zones are clearly seen in the NO 2 pro

three cases, the fl flames exhibited a double fl

les. The NO

and NO 2 pro les indicate signi cantly lower level of NO x formation in biogas

fl flames. This may be attributed to the less

thermal NO and prompt NO formed, indicated by lower temperatures and C 2 H 2
peaks, in biogas

flames compared to that in methane fl

flames. The lower C 2 H 2
peaks also imply lower prompt NO and soot formation in biogas

fl flames compared to those in methane fl

fl flames, although

soot emission is not a major concern in natural gas and biogas fl ames.

3.3 Syngas and Biogas Combustion in Practical Devices

There have been numerous studies in recent years dealing with various aspects of
syngas-fueled combustion systems. Many of these studies are discussed in a special
issue of Combustion Science and Technology ( 2008 ). There is signi

cant interest in
using syngas in gas turbine engines (Luessen 1997 ; Lieuwen et al. 2008 ; Dam et al.
2011 ), especially in the context of an IGCC facility, for efficient, low-emission
power generation, and for carbon capture and storage. Extensive literature exists
dealing with the natural gas (NG)- red combustors, which is beyond the scope of

this review. Some research in this area has also focused on using syngas in natural
gas- red combustors (Colantoni et al. 2010 ). The viability of using syngas and

biogas in spark ignition (SI) and compression ignition (CI) engines has been a
subject of numerous investigations (Boehman and Le Corre 2008 ; Sahoo et al.
2012 ; Bika et al. 2011 ; Korakianitis et al. 2011 ). With regard to CI engines, much
of the research has focused on dual-fuel operation, which is discussed in the next
section. The use of syngas in SI engines offers many advantages, such as better anti-
knocking properties and operation with leaner mixtures. Improved knock resistance
is due to the presence of CO and enables operation at higher compression ratio,
leading to higher thermal ef

ciency. However, higher burning rate due to the
presence of H 2 can lead to higher end gas temperature and increased propensity to
knocking. The presence of H 2 can also increase NO x emissions, which may be
controlled by using leaner mixtures (Boehman and Le Corre 2008 ). Bika et al.
( 2011 ) examined such issues by performing single-cylinder experiments for dif-
ferent syngas compositions, compression ratios, and equivalence ratios. For a given
ϕ and spark timing, the knock-limited compression ratio was observed to increase

with increasing CO fraction. The burn duration and ignition lag also increased with
increasing CO fraction.
Compared to CI engines, the NG-fueled SI engines for automobiles have been
used with reasonable success, especially in South America. For instance, there are
nearly 3.4 million natural gas vehicles (NGVs) in operation in Brazil and Argentina.
A number of studies have examined the performance and emission characteristics of