Automotive Engineering - July/August 2019 - 29

COVER STORY

collaborative R&D projects with the U.S. Dept. of Energy (DoE), networking with top universities and suppliers, in addition to spearheading North American market emissions validation and certification.
"In advanced combustion engines there are two main areas that
we're involved in," notes Phil Zoldak, Hyundai Powertrain's manager
of engine development and testing, who joined our meeting with
Juriga and Lee. "One is furthering traditional boosted SI engines. The
other is lean-burn engines, and within that space are two branches:
Spark-ignited, which looks at dilution with EGR and advanced ignition systems, and lean-burn compression ignition.
"We're focusing more on the lean-burn development side, in what
we call Technology Enablers-advanced ignition systems, advanced
boosting and controls," he said. "We use CFD extensively to co-optimize and select the right hardware."
A DoE-sponsored program that ran from 2011 to 2018, dubbed
GDCI, focused on a gasoline-fueled compression-ignition engine with
Hyundai working with partners Delphi and the Wisconsin Engine
Research Consultants. It yielded significant learnings, Juriga said, but
had two pitfalls. "The hardware we had to use-a turbocharger and
supercharger-drove system complexity and cost. It also had no
spark mode; it relied exclusively on compression ignition, which compromised things like cold start. It was perhaps too aggressive."

LINDSAY BROOKE

Mixed-mode controller
GDCI was followed by the Co-Optima Initiative, launched in January
2019 and running to 2021. Co-Optima is short for "Co-optimized Fuel
and Multi-Mode Gasoline Compression-Ignition Engine for Meeting
Future Emission Standards." Funded by the DoE's Vehicle Technology
Office, the program aims to create engines and fuels that are more
effectively optimized together. Nine U.S. National Labs are collaborating on the project. Hyundai North America is collaborating with
Michigan Technological University (MTU - simulation) and Phillips 66
(fuel development). A Hyundai 2.2-L diesel is serving as a mule test
rig; "we may end up with a gas engine in the end, with a unique head
geometry," Juriga noted.
"This program is our effort to put everything into a package that is
production-intent and uses more off-the-shelf-type hardware," explained Zoldak. "The engine has the ability to start out in an SI mode,
operating in a stoichiometric or lean-combustion mode, and transition into a more low-temperature combustion mode using internal
residuals [EGR]. Then make another transition into a compressionignition mode using external EGR. So, there's three transitional
modes we're looking at as you increase load.
"The complexity of mode switching comes into play, and as you
can imagine fuel octane starts to bear on this," Juriga noted. Phillips
66 is providing a range of fuels with different octanes and reactivity.
The fuels are then being modeled; "we're using a real-fuel modeling
technique that MTU has developed," said Zoldak.
The program aims to achieve steady-state performance first, combining simulation and hardware selection, before trying to tackle the
transients that have challenged the drivability of virtually every leanburn engine development effort.
"We're building an engine that can capture all the modes, at specific points, on the dyno," Zoldak explained. "The main scope of the
AUTOMOTIVE ENGINEERING

An engine guy to the core, veteran powertrain engineer John
Juriga is still having fun despite the complexity of developing
multiple propulsion solutions.

"The intent is to create an engine
that seamlessly transitions from
spark-ignition stoichiometry
to compression-ignition mode,
depending on load, using low-cost
hardware."
work wasn't to do transient testing. It wasn't a requirement of the project, but we'll be doing some testing in
transients. We'll handle them using a mixed-mode
controller-we have different combustion modes that
are calibration-optimized for that region and use algorithms to transition from one mode to another."
The changeovers will be dependent on the development team's grasp of system dynamics-the operating-speed deltas among production-intent, rather
than R&D-spec hardware including injectors, EGR
valves, turbo boost levels, etc.-and how they can be
adjusted to operate rapidly, on command. "We'll look
at how lean can we go, and what fuel and air systems
do we need to support it." Juriga noted. New ignition-system technologies are being investigated as a
sideline of the project.
"As we go through development, we'll be refining
the characteristics of the compression-ignition gasoline engine with the goal of reducing emissions in
cylinder," he explained. "The merging of gas and diesel technologies is something we've been looking at
for years."
July/August 2019 29

Automotive Engineering - July/August 2019

Table of Contents for the Digital Edition of Automotive Engineering - July/August 2019