Automotive Engineering - April 2022 - 20

Keeping combustion
in the conversation
ADVANCED PROPULSION FEATURE
quirements, up to putting in everything you can right
now, " he noted. " There's a wide array of different
technologies - efficiency optimization obviously
plays a very big role - otherwise from a CO2 and fueleconomy
perspective, you won't meet the targets. "
He also mentioned the menu of existing technologies
that can be improved in the quest for the " better "
ICE, particularly " higher stroke-to-bore ratios combined
with cooled EGR to deliver higher efficiencies at
stoichiometric combustion. " Tomazic added that
" [fuel]-injection pressures going up beyond 350 bar
and pre-chamber applications could also become very
important technologies which potentially also would
allow us to go very lean to a point where we would see
very low NOx emissions - from an aftertreatment perspective,
that could mean some relief. "
Audi's HVO diesel fuel is said to drastically reduce CO2 from current-production
4- and 6-cylinder diesels. It is available in 600 retails stations in Europe.
Hybrid, long-stroke hope
There no longer is absolute consensus among powertrain developers
that hybridization will be ubiquitous in most light-vehicle segments.
Not long ago, hybridized ICEs had driven the case for continuing ICE
development and was its reason for being. Without hybridization,
many experts believe, a conventional ICE powertrain will not be fueleconomy
or emissions compliant in many world regions.
The AVL engineers see ICEs for hybrids that adopt and enhance a
variety of existing technologies to narrow the engine's operating
range even more than in today's " full " hybrids. Such specialized designs'
operating characteristics make the engine more of a type of
" generator " than a full-range powerplant. Their enabling technologies
include some combination of cooled EGR, high compression ratio
and longer-stroke dimensions.
" One area which I think still has not been fully exploited - and is
under exploration at the moment - is low-pressure EGR in gasoline, "
said AVL's Howell. " This can be a pretty impressive enabler; AVL's
been developing dedicated hybrid engines for quite a while. We've
achieved 45 percent [brake thermal efficiency] out of a 11:1 [compression-ratio]
engine. That uses a plethora of technologies, which are all
known, but it's a matter of optimizing in order to achieve that. "
The key enabler for that type of application, Howell explained, is a
" very high " stroke-to-bore ratio. But the challenge that comes with
that type of application is it requires a 'new' engine. " So, it seems
unlikely to be a mainstream in EU and U.S. because of the sunsetting
of the IC engine, " he said. " But there is a lot of interest in China.
We've done several engine platforms in the Chinese market. "
FEV's Tomazic sees a developmental difference between ICEs designated
for micro-hybrid and mild-hybrid duty, versus " dedicated "
hybrid engines that would include those designed for HEV and
PHEV applications. OEM strategies will range from, " You would only
add as much technology as you need to meet the regulatory re20
April 2022
Total tech papers: 803
AUTOMOTIVE ENGINEERING
Powertrain, propulsion continue to
lead SAE tech-paper topics
For 2022, advanced powertrain/propulsion-related topics
continued to dominate the categories of published SAE
technical papers, more than doubling the number papers
in the next most-prolific general topic area. Some 281
powertrain/propulsion papers were written for 2022 publication,
comprising 35% of the 803-paper total.
Despite the difficulties imparted by the COVID-19 pandemic,
2022's technical-paper production was down less
than 10% compared to 2021. The powertrain/propulsion
category includes papers addressing ICEs and hybrids
and there continued to be considerable contributions in
IC-related areas of combustion for spark-ignited and compression-ignition
engines, fuel-injection and use of alternative
and advanced fuels.
TOP: AUDI
Automotive Engineering - April 2022

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