Truck & Off-Highway Engineering - December 2024 - 11

POWERTRAIN FEATURE
Cummins provided its X15N natural gas engine that SwRI
converted to run on port-injected hydrogen.
include Bosch, Phinia, SuperTurbo, Mahle, SEM,
Woodward and Eaton.
" From custom-built parts and prototype components
to specially formulated lubricants, this has truly
been an industry-wide effort, " Williams said. " We
could never have completed the demonstration vehicle
in the short time that we did without the support and
collaboration of the consortium. "
SwRI built on experience from previous heavy-duty
low-NOx projects to develop a novel aftertreatment
system specifically adapted to the hydrogen exhaust
environment. Paired with the H2-ICE's already low engine
emissions, the addition of the aftertreatment system
reduces NOx emissions to 0.008 g/hp-hr with
aged catalysts, which is well below the 2027 EPA limit
of 0.035 g/hp-hr.
Challenges met
Truck & Off-Highway Engineering interviewed Williams
at SAE COMVEC 2024, where he discussed the driving
forces behind the development of the truck as well as
some of the obstacles that the consortium overcame
to meet their goals.
" Obviously we've got a big challenge of decarbonizing
transportation, " he said. " We're seeing the challenges
and the limitations of the current zero-carbon offerings,
as well as just the practicality of being able to make
enough of those vehicles at scale to replace everything
that's on the road right now. That was a big part of the
motivation behind this project. "
TRUCK & OFF-HIGHWAY ENGINEERING
The hydrogen demonstrator truck was on display at SAE's 2024 COMVEC
symposium in Schaumberg, Illinois.
" This truck was created to show what technology options are available
that we think will help us to ramp things up a lot faster and
eventually will be more cost effective, " he explained. " We've got all
this great technology. We've been evolving technology for combustion
engines over the last hundred years. So why not take all that
technology and use it? "
Williams also discussed the emissions side of SwRI's efforts.
" Another big part of this program is to demonstrate the emissions because
that's the other half of the question everybody asks. So, we've
been able to demonstrate through this vehicle that we've significantly
lowered NOx more than any other program or engine that's out there.
" For context, the current standards that have been settled on for
2027 are 35 milligrams per horsepower hour. We set out with the goal
of at least meeting that, " he continued. " But then California also has a
voluntary ultra-low NOx standard of 20 milligrams. What we were able
to demonstrate is below 10 milligrams on every regulatory cycle. "
SwRI built upon knowledge gained in past low-NOx demonstrations.
" We started with the same architecture of the aftertreatment
system, but thanks to the benefits of hydrogen, we were able to get
the NOx emissions about ten times lower than a typical diesel engine, "
Williams said. " That allowed us to significantly simplify the aftertreatment
system. We've taken out most of the precious metal
content and about half of the volume of catalyst. The DEF consumption
is about a tenth of what you would expect from a diesel engine. "
Controlled combustion
Williams also discussed the challenges of achieving clean combustion
with hydrogen fuel. " Hydrogen has a very low lean flammability limit, "
he explained. " It's a little more analogous to natural gas. You can run
about one and a half Lambda [with CNG], that's one and a half times
December 2024 11
BOTH IMAGES: SAE/MATT WOLFE
Truck & Off-Highway Engineering - December 2024

Table of Contents for the Digital Edition of Truck & Off-Highway Engineering - December 2024
