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July 31, 2023
Technology Fuels a New Future for
Internal Combustion Engine
The Secret Lies in the Use of
Greener Fuels
![](images/images_08_09_2023/Feature-LEDE--Cummins-1200.jpg)
Cummins’ factory assembly line at
its Jamestown Engine Plant in Lakewood, N.Y., where its X15N engine
will be produced. (Michael Freeze/Transport Topics)
According to fleet executives as well
as fleet maintenance managers, the death of the internal combustion
engine may prove to be greatly exaggerated in spite of the excitement
about electric powertrains. Industry leaders have been working to give
the basic piston engine an extended life.
SPARK: Go in-depth on the future of ICEs in our half-day virtual event
The secret to this life extension for ICEs lies in the use of greener
fuels as they allow reduced cost of fuel and maintenance for fleets
while at the same time reducing greenhouse gases. These newer engines
will also have a much easier time keeping up with stringent upcoming
emission standards for primary pollutants like NOx, particulates and
unburned hydrocarbons. Experts believe the likely final result of new
fuel technology will be a far greener future that, at the same time,
will often resemble the familiar present.
“The problems of the diesel engine are more related to the fuel than
to the engine itself,” said BJ Johnson, co-founder and CEO of
ClearFlame Engine Technologies.
The new engines will all use lower-carbon fuels, many of them derived
from nonmineral sources that derive their energy directly from the
sun, thus reducing CO2 in the atmosphere. Renewable natural gas will
capture low-carbon methane from present sources like farming and
landfills, and burn the fuel in engines. Although these engines
release CO2, the amount is less than when running on diesel fuel,
resulting in a “carbon-negative” result.
![](images/images_08_09_2023/Feature-ClearFlame-650.jpg)
An engine is retrofitted with the ClearFlame
combustion system, including a ClearFlame Engine Control Module. (ClearFlame)
Cummins will introduce the X15N in 2024, a
spark-ignited natural gas engine that will be the first of the
company’s engines based on their new fuel-agnostic platform that uses
common parts below the cylinder head. “The natural gas engine will
have a unique cylinder head for the necessary cooling, and its spark
ignition system,” said David King, Cummins’ North American on-highway
product manager, natural and renewable gas engines, adding that the
15-liter engine will be a game changer because of its “get up and go.”
The natural gas engine will have 1,850 pound-feet of torque available
by 1,100 rpms and 1,800 pound-feet at the X15 diesel’s torque peak of
1,000 rpms. King also noted that it’s quieter than a diesel whether
idling or generating grunt.
Westport Fuel Systems
CEO David Johnson describes a different type of natural gas engine
based on Rudolf Diesel’s original theory. Powered via its high
pressure direct injection system developed by Westport, the engine
burns natural gas as its primary fuel with a tiny shot of diesel for
ignition. The patented HPDI injector provides both fuels under extreme
pressure via a dual concentric needle design. It retains diesel-like
efficiency, power and torque, but needs to use liquefied natural gas
so its onboard fuel pump can produce the high-injection pressure
needed. It will also need a selective catalytic reduction system for
NOx and a simple diesel particulate filter. Westport and Volvo Group
recently signed a letter of intent to use the system to reduce CO2
emissions, especially when renewable natural gas is the fuel.
Hyliion has created a hybrid model, ERX Powertrain, which runs on
renewable natural gas. It combines a large battery pack at the rear of
the cab with a 12-liter engine that runs on RNG. It can be charged off
the grid to produce 75 miles of all-electric operation. Its 12-liter
natural gas engine drives only a generator, which charges the
batteries and provides drive via tandem electric axles. The axles also
regenerate during braking, the result being about 1,000 miles of total
range. As much as 672 peak horsepower is available, and the batteries
power all hotel loads during rest breaks.
Charles Mueller, scientist at Sandia National
Laboratories, led an effort to develop ducted fuel injection, which
provides a small duct a short distance from each spray produced by a
diesel’s injector for better fuel/air mixing. The system reduces
particulate to the point where EGR can be used to kill NOx in the
cylinder, eliminating the SCR system. When running on
oxygen-containing biofuels, the system may make it possible to meet
NOx standards without exhaust gas recirculation while also reducing
net-carbon emissions by 70%. Mueller is working with engine OEMs and
low-net-carbon fuel providers to retrofit a heavy-duty engine with DFI
and demonstrate the technology with a commercially available,
low-net-carbon fuel and quickly move the technology closer to
commercial applications.
Johnson described ClearFlame’s system that capitalizes on all the heat
already available in a diesel engine to support the combustion of
green fuels. Engines modified via ClearFlame’s system run on low-cetane
fuels like ethanol that won’t ignite in ordinary diesels. The key is
allowing heat ordinarily removed by the charge air and the EGR coolers
to remain in the intake air. This greatly raises the temperature in
the cylinder at the top of the compression stroke, and that is all
that is necessary to ignite green fuels that don’t produce soot —
meaning no DPF is needed. The engine’s ability to keep its exhaust hot
allows a simple SCR system that will meet future, tighter NOx
standards.
Alternative Fuels
At the Engine Research Center symposium at the University of Wisconsin
last summer, Andre Boehman, professor of mechanical engineering and
director of the W.E. Lay Automotive Laboratory, discussed low-net
greenhouse gas fuel and engine technologies and brought attention to
the diesel fuel known as dimethyl ether.
![](images/images_08_09_2023/Feature-Hydrogen-.jpg)
This illustration shows the top of the upcoming Cummins
hydrogen engine to be built on the company's fuel-agnostic engine
platform. (Cummins)
He noted that DME is an ideal diesel fuel with a
cetane rating just above what present diesel has and, containing
oxygen, it burns without smoke. It can easily be made out of renewable
fuels like ethanol and many others, even agricultural byproducts, and
its smokeless character means a high tolerance for EGR to combat NOx
emissions. While it needs a pressurized tank, the pressure generated
is much lower than even with propane, meaning far lower pressures than
those needed for natural gas.
The fuel requires a different injection and combustion system from
standard diesels as it evaporates very fast and has no natural
lubricity, but likely can be adapted for use in engines with familiar
injection and combustion systems.
OEMs such as Volvo have on-road tested DME before, while countries
like Sweden have seen large-scale testing, where 10 heavy-duty
commercial trucks drove more than 1.5 million kilometers powered by
the fuel. One of the major challenges is engineering enough durability
into DME injection systems, a process that may be augmented with
exotic lubricity agents.
A notable alternative fuel, hydrogen, is 100% green and easily created
from green electricity. Westport’s Johnson points out that fuel cells
are most efficient at low loads, while piston engines are more
efficient as loads increase. Thus, an ICE may be the ideal way to use
hydrogen in commercial hauling, as opposed to passenger cars where
engines cruise at low loads. He said Westport’s HPDI natural gas fuel
system is easily adapted for retrofit to any internal combustion
engine including one that runs on hydrogen. He argues that the
company’s extensive experience supplying engines with gaseous fuels
will give his company a leg up in the hydrogen internal combustion
engine market.
Cummins is developing a spark-ignited, hydrogen
engine. Jim Nebergall, general manager of Cummins Hydrogen Engine
Business, told Transport Topics that the company’s hydrogen engine,
another built on its fuel-agnostic platform, will be “a hybrid of our
natural gas and diesel engines. It will be spark-ignited, yet direct
injected.”
He explained that hydrogen creates such rapid flame travel that
supplying fuel and air premixed in the intake manifold to the
cylinders can allow flame to travel back into the manifold. Thus, a
low-pressure fuel system a bit like diesel injection will supply fuel
to the combustion chamber. The engine will resemble a diesel in that
it will run very lean, with the extra air allowing about 20% more
power.
Green Play Ammonia™, Yielder® NFuel Energy.
Spokane, Washington. 99212
www.exactrix.com
509 995 1879 cell, Pacific.
Nathan1@greenplayammonia.com
exactrix@exactrix.com
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