Truck & Off-Highway Engineering - August 2024 - 6

TECHNICAL INNOVATIONS
The CFD optimization process to improve the mixing by choosing the best engine aerodynamic architecture and injector targeting. Good matching was
observed between simulation and experiments for a mid-load operating point.
and targeting) " is of first interest " to
achieve further improvements relating
to hydrogen/air mixing and engine performance,
the experts said.
IFPEN's engine research team
spearheaded the development of an
in-house-designed engine test bench:
a 2.1-liter displacement single-cylinder,
direct injection engine with a
maximum injection pressure of 40 bar
(580 psi). IFPEN's partners in building
the test engine were Tenneco
Powertrain (supplier of the spark
plug), Phinia (supplier of the hydrogen
injector), and Danielson
Engineering (manufacturer of the hydrogen
combustion engine).
" In the end, it was possible for us to
realize a full engine map based on the
proposed CFD design, " Giuffrida said,
noting that an indicated efficiency of
47% was predicted by CFD and confirmed
experimentally on the test
bench with the 2.1-liter hydrogen engine.
A maximum efficiency of 48% is
possible with a lambda ratio ranging
from 1.8 to 3.
Three-dimensional combustion modeling
of a hydrogen engine still presents
challenges for engineers. For example,
the supersonic hydrogen jet occurring
in the combustion chamber with hydrogen
direct injection is difficult to model
due to unaccounted hydrogen specific
properties, namely vortices and diffusion.
The CFD team also noted significant
differences in the hydrogen/air
mixing function of turbulence modeling
approaches via RANS (ReynoldsAveraged
Navier-Stokes) and LES
(Large Eddy Simulation).
Another software modeling challenge
for the hydrogen combustion engine
relates to wall heat transfers, especially
considering the inherent differences of
physical properties, such as quenching
distance, between hydrogen and other
conventional fuels, such as gasoline and
methane. The bottom line is the need
for additional research work to identify
the causes of pre-ignition and knock so
that those unwanted phenomena can
be addressed in the modeling process.
Various challenges related to a hyComparison
between experimental (dotted line) and simulated (full line) in-cylinder pressure for
a spark advance sweep at 1200 rpm and 9 bar Indicated Mean Effective Pressure (IMEP), showing
good accordance in all variation spectra of the spark advance variation.
6 August 2024
drogen internal combustion engine are
being addressed at IFPEN with ongoing
research, according to Giuffrida. IFPEN
engineers and researchers are also
working with Convergent Science to
improve CFD modeling of hydrogen
combustion via different research programs,
including projects focused on
advanced experimental tools.
Kami Buchholz
TRUCK & OFF-HIGHWAY ENGINEERING
BOTH IMAGES: IFPEN

Truck & Off-Highway Engineering - August 2024

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