Truck & Off-Highway Engineering - April 2022 - 20

HITTING THE GAS ON
HYDROGEN
TECH
With the Clarity, Honda was one of the first OEMs to offer a
hydrogen-powered light vehicle for retail customers.
" While there remain a few unknowns in the hydrogen engine space,
Cummins soon will
offer a full line of fuelagnostic
engines. Its new
B6.7 Octane (gasoline)
engine, shown, is similar
in architecture to what
the hydrogen-fueled ICE
will look like.
long-haul trucking market, hydrogen-powered engines
are an excellent mid-term, zero-emissions solution that
utilizes current technology and chassis while also
meeting customer needs.
In practice, a hydrogen-fueled ICE truck is similar in
operation to a CNG-powered unit, the main differences
being that H2
engines will require different hardware
and software. The second major difference lies in the
fuel system. Cummins specifies that the carbon-fiber
fuel tanks of an H2
(10,000 psi) versus 250 bar (3,625 psi) for CNG.
Cummins notes that this is not an industry standard;
systems can range from 350 bar (5,000 psi) to
700 bar. However, the company claims that 700-bar
pressure enables greater onboard fuel storage and
range. This storage pressure does increase the number
of windings required for each fuel tank, which
increases weight and cost of the system versus natural
gas, but these tanks can be used for either a hydrogen
ICE or FCEV.
Production advantages of H2
ICEs include shared
componentry with diesel and CNG engines, such as
the engine block, crank, ancillaries, and installation
parts (flywheels, piping, mounts) as well as utilizing
existing manufacturing tooling and processes. An H2
specific motor will require a unique fueling system,
electronics and ignition system.
20 April 2022
truck will store the fuel at 700 bar
H2 injection methods
Yousef Jeihouni, project manager of FEV North America's engine and
powertrain systems, expanded on the capabilities of hydrogen ICEs
and the various types of H2
injection currently in development. While
there are a wide variety of ignition methods that can be employed in
H2
ICEs, Jeihouni states that the most common method currently in
use is spark-ignition.
" The majority of conversions we are seeing right now are utilizing
spark-ignited engines and essentially using CNG engines to be converted
into H2
combustion engines, " Jeihouni said. " This type of engine
is applicable to light-duty passenger cars as well as heavy-duty
long-haul trucks. "
According to FEV, Otto cycle premixed ignition is the most convenient
method for smaller bore diameters. The bore limit for most
CNG engines with open chamber ignition is 170 mm (6.7 inches) or
less. Due to higher flammability limits and the increased flame speed
required for hydrogen combustion, larger bore diameter applications
can be equipped with only one spark plug.
Jeihouni elaborated that for medium duty (trucks equipped with
8-liter engines) and heavy duty (trucks equipped with 13L engines) the
most favorable method of meeting the required engine outputs was
the combination of low- to mid-pressure direct injection resulting in
lean full load and ultra-lean part load operation. Turbocharging is still
utilized for H2
combustion engines with boost pressure managed by a
wastegate and supplemented by a variable-geometry turbo. The culmination
of all these methods is the best possible durability, efficiency
and range available with current technology, he said.
There are some challenges with H2
ICEs such as management of
NOX emissions, which are still a critical factor in hydrogen combus-
tion.
However, they can be reduced to extremely low levels with
properly selected and dimensioned exhaust gas aftertreatment systems
and dedicated control algorithms. Other challenges of developing
hydrogen engines include avoiding preignition at high BMEP
TRUCK & OFF-HIGHWAY ENGINEERING
we've witnessed a significant amount of interest within the industry for
hydrogen engines over the last 12 months, " said Nebergall. " Fleet operators
are very interested in leveraging hydrogen engines to accelerate
and decarbonize their commercial vehicle fleets. "
FROM LEFT: CUMMINS; HONDA
Truck & Off-Highway Engineering - April 2022

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