Using Petroleum and Biomass-Derived Fuels in Duel-fuel Diesel Engines - Novel Combustion Concepts for Sustainable Energy Development - page 264

used for analyzing the combustion and emission characteristics of biogas. For both
syngas and biogas, a major challenge to combustion system designers is due to the
wide variation in their composition. This also provides opportunities for funda-
mental and applied research on both the production and utilization aspects of such
fuels. Fundamental combustion aspects requiring further research include cellular
instabilities, ames, and

emission characteristics. Such efforts would lead to the development of optimized
systems for producing these fuels and provide guidelines for optimizing their
composition for a given set of operating conditions.
The use of syngas and biogas in dual-fuel diesel engines has been a subject of
numerous experimental and computational studies. In a dual-fuel operation, the
gaseous fuel-air mixture is introduced through the intake valve, while the diesel fuel
is injected and compression ignited. A general observation from these studies is that
the engine performance and emission characteristics are signi

fl flame stabilization and blowout behavior, turbulent fl

ed by
the presence of gaseous fuel. For instance, the two-stage ignition process associated
with the diesel fuel can be noticeably in

cantly modi

uenced depending upon the engine load
and the relative amounts of gaseous and liquid fuels. The combustion characteristics
are also signi

fl

cantly altered due to the presence of gaseous fuel. While the heat
release in a diesel engine generally occurs through a hybrid combustion mode,
involving rich premixed combustion and diffusion combustion, that in a dual-fuel
engine also involves a lean combustion mode with a propagating flame. The dual-
fuel operation at high-load conditions can provide signi cant reduction in soot and

CO soot emissions, while maintaining the engine ef ciency, provided the injection

characteristics including the amount of pilot fuel can be optimized. However, the
NO x emission may increase, requiring a suitable strategy for lowering the tem-
peratures. The dual-fuel strategy may be less effective at low load, resulting in
lower thermal ef

ciency and higher UHC and CO emissions. Future work should be
directed at optimizing the various parameters, such as injection timing, amount of
pilot fuel injected, EGR, and multiple injections.

Acknowledgments Prof. Aggarwal s research over the years has been funded by several federal

agencies, including NSF, NASA, AFOSR, EPA, Wright-Patterson Air Force Base, and ANL, as
well as industry. His work concerning engine combustion and biomass-derived fuels has been
supported by ANL. Many results in this monograph were computed by graduate students, Mr.
Francesco Quesito and Mr. Xiao Fu.

'

References

Aggarwal SK (2009) Extinction of laminar partially premixed fl flames. Prog Energy Combust Sci

570
Aggarwal SK (2013) Simulations of combustion and emissions characteristics of biomass-derived
fuels. In: Dahlquist E (ed) Technologies for converting biomass to useful energy: combustion,
gasi cation, pyrolysis, torrefaction and fermentation. CRC Press, Boca Raton
Aggarwal SK, Awomolo O, Akber K (2011) Ignition characteristics of heptane-hydrogen and
heptane-methane fuel blends at elevated pressures. Int J Hydrogen Energy 36:15392 - 15402

35:528

-