Spark-Ignition Engines - Fundamental Research for an Individual Sustainable Mobility
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RESE ARCH F V V Projects
Spark-Ignition Engines –
Fundamental Research for an Individual
Sustainable Mobility
Spark-ignition combustion engines
make up a considerable share
of the powertrains for individual
mobility applications – not just today,
but also in the decades to come
as a part of electric powertrains.
The Research Association for Com
bustion Engines (FVV) is therefore
dedicating numerous research proj-
ects to reducing the CO2 emissions
from these engines, with a special
focus being placed on real-world
operation with fuels produced in a
CO2-neutral manner.
1 MOTIVATION
The growth of the global population
and prosperity will result in increasing
demand for individual mobility solu-
tions. The industry’s task is to react to
this demand with offers that support the
Sustainable Development Goals (SDG)
[1] outlined by the United Nations.
Alongside climate action (goal 13), the
SDGs contain further targets which
affect engine research, including good
health and well-being (goal 3), decent
work and economic growth (goal 8)
and responsible consumption and pro-
duction (goal 12). Spark-ignition com-
bustion engines currently make up a
large proportion of individual mobility
applications around the world. In light
of the diversity of demands and regional
infrastructural requirements, it currently
appears improbable that a single power-
train technology will completely replace
fossil fuel-powered spark-ignition en
62 www.springerprofessional.com/automotive
VOICES OF THE F V V
Dr.-Ing. André Casal Kulzer is responsi-
ble for Thermodynamics in Advanced
Powertrain Engineering at Porsche AG in
Stuttgart (Germany). At FVV, he is Head
of Planning Group 2 “Combustion SI.”
“The research at FVV enables us to
lay the technical groundwork in order
to answer the geopolitical questions
© FVV
around energy supply.”
Prof. Dr. Friedrich Dinkelacker is Head
of the Institute for Combustion Tech
nology (ITV) at the Leibniz University,
Hanover (Germany), which conducts
FVV projects as an RTD performer.
“Fundamental understanding
and methodical expertise are the
prerequisite for using renewable
© ITV
energy carriers.”
Koichi Nakata is General Manager
of the Toyota Motor Corporation in
Susono, Shizuoka (Japan).
“ In the future, the interface between
engine and fuel development will
be more important when it comes
to reducing greenhouse gases.
The entire world will benefit from
© Toyota
the research in this field.”
Prof. Dr.-Ing. Fabian Mauß is Holder of
the Chair of Thermodynamics/Thermal
Process Engineering at the Institute of
Electrical Systems and Energy Logistics
at the Brandenburg University of Tech
nology Cottbus-Senftenberg (Germany).
“Supplementing conventional fuels
with synthetic components based
© BTU
on hydrogen can make the existing
fleet more climate-friendly.”
http://www.fvv-net.de/en
© Porsche
MTZ worldwide 03|2021 63
RESE ARCH F V V Projects
Efficiency Route A Route B Route C Route D Average
WLTC “Sporty” “Sporty” “Moderate” “Moderate” Efficiency RDE
Efficiency
engine 39.9 % 41.7 % 41.8 % 40.5 % 39.7 % 40.9 %
(without EGR)
Efficiency
engine 40.6 % 42.6 % 43.2 % 41.3 % 40.4 % 41.9 %
(with EGR)
Methanol
43.3 % 46.0 % 45.6 % 44.6 % 42.5 % 44.7 %
engine
TABLE 1 Powertrain efficiency of a high-efficiency engine in various driving cycles (© FVV)
Cluster Fuel ρ norm [kg/m 3] ΔLHV [MJ/kg] ΔLHV [MJ/l] C : H : O [-] ΔRON [-] ΔMON [-] Δη i [%]
Reference RON95E10 756.25 41.16 31.13 6.3 : 11.7 : 0.2 96.7 87.4 39.4
1 M29 765.92 -6.1 -4.27 3.5 : 7.6 : 0.6 +4.70 +0.80 +4.17
1 E49 772.02 -7.07 -4.81 3.5 : 8.0 : 0.7 +9.30 +3.90 +4.83
1 H45 415.98 +35.16 +0.0 0.16 : 13.7 : 0.01 - - +3.09
2 M11 759.97 -2.35 -1.63 4.9 : 9.7 : 0.4 +1.90 +0.30 +3.47
2 E25 764.39 -3.64 -2.45 4.6 : 9.4 : 0.5 +4.80 +2.00 +4.08
2 H45 415.98 +35.16 - 0.16 : 13.7 : 0.01 - - +3.09
Legend = Cluster 1: low CO 2 emissions; Cluster 2: low fuel consumption; M29: M: methanol; E: ethanol; H: hydrogen; ρ norm: density under normal conditions;
ΔLHV: change of the lower heating value compared to the reference; C : H : O: carbon to hydrogen to oxygen ratio; ΔRON: change in Research Octane Num-
ber (RON) compared to the reference; ΔMON: Change in Motored Octane Number (MON) compared to the reference; Δ ηi: change in combustion efficiency
compared to the reference
TABLE 2 Increases in the degree of efficiency caused by different admixtures to standard gasoline (© Fabian Mauß | BTU)
gines in the short term. Indeed, it is nological prerequisites, consciously gart analyzed the effects of combining
far more realistic to expect different integrating small and medium-sized different technologies. The goal was to
technologies to coexist and work in companies in the innovation process. achieve a maximum engine efficiency
parallel in hybrid concepts. Further- at the best possible degree of efficiency
more, the sustainability of the global explicitly throughout the entire power-
2 SYSTEMATICALLY
fleet of around 1.2 billion cars [2] train in real-world driving cycles. In va
OPTIMIZING EFFICIENCY
should also be considered, of which rious technology packages comprising,
a high but unknown percentage are Spark-ignition engines can make a among other things, high compression
powered by spark-ignition engines. key contribution to sustainability and flexible valve timings including
In light of this, further research on if their degree of efficiency in real the Miller procedure, exhaust gas recir-
spark ignition engines with a focus driving operations can be substan- culation, control of the charge motion,
on high sustainability is absolutely tially increased – without simultane- pre-chamber ignition, water injection,
necessary. The entire energy chain ously downgrading the environmen- lean operation and long-stroke engine
(well-to-wheel) and the entire prod- tal balance through higher pollutant design were analyzed. To determine the
uct life cycle (cradle-to-grave) must emissions or lower durability. In the powertrain efficiency, the researchers
be taken into account, and not just FVV project “ICE 2025+” [3], which used various hybrid powertrain com
the energy converters themselves. was completed at the end of 2020, four binations, taking into account electri-
Industrial collective research, as per- research institutes at RWTH Aachen cal energy that was only obtained by
formed by the FVV and described in University, the Technical University of on-board recuperation. The interaction
the following projects as examples, Braunschweig, the Technical University with several alternative, potentially
creates the methodological and tech of Darmstadt and the University of Stutt- CO2-neutral fuels was also examined.
64 www.springerprofessional.com/automotive
Even before the project had con- few fundamental examinations on the platform for fuels and engines was
cluded, it was clear that a powertrain thermodynamic behavior. For a meaning- developed and used at the Brandenburg
efficiency level of over 40 % is possible ful simulation of the combustion itself University of Technology. The results
in C-segment vehicles using standard as well as certain phenomena such as of the project – in the form of both an
gasoline with the combination of suit- uncontrolled self-ignition, exact knowl- extended version of the zero-dimen-
able technologies. While the average edge of the reaction kinetics is necessary. sional calculation program “FVV cylin-
value was 40.6 % in the Worldwide The “Fuel Composition for Reducing CO2” der module” and as detailed collections
Harmonized Light-duty Vehicles research project therefore aims to answer of data on the individual fuel compo-
Test Cycle (WLTC), the average value the question as to how new generations nents – will be available as a knowledge
achieved in simulated Real Driving of fuels and their composition can help base for the entire industry. Completion
Emissions (RDE) cycles was even increase the degree of efficiency [4]. In is planned for 2022.
higher at 41.9 %, as shown in TABLE 1. a collaboration of five research institutes,
By replacing the standard fuel with the behavior of different fuel molecules
4 SPRAY DIAGNOSTICS
methanol, the hybrid powertrain in is analyzed, measured during combus-
a C-segment vehicle reached an effi- tion and transferred to suitable simulation While the chemical properties of new
ciency of 43.4 % in the standard cycle methods. Initially, the project partners fuels are primarily decisive for the
and 42.7 % on average in simulated selected fuel components with the poten- combustion behavior, the physical pro
road driving. Beyond these examina- tial to reduce the knocking tendency and perties play a key role when it comes
tions, the additional potential of lean simultaneously increase combustion to carburation. If direct injection is
operation was also analyzed. Operat- speed, thereby raising combustion effi- used (as is common in spark-injection
ing the methanol-powered engine with ciency. Based on new measurements and engines), the break-up of the injection
excess air resulted in efficiency levels available data from literature, a reaction jet into small droplets determines the
above 40 % across a large section of the mechanism is currently being developed efficiency and pollutant emissions.
engine characteristic map – with a peak and applied in Computational Fluid There is currently little data on the
of 46.9 %. Compared to a spark-ignition Dynamics (CFD) simulations. A model primary disintegration of the spray,
engine corresponding to the current is being derived with which mixtures of particularly when using synthetic
state of the art, this would result in standard gasoline and alternative fuels so-called e-fuels. In the “Spray Diag
a CO2 reduction of up to 25 %. can be created with the objective of gen- nostics of Gasoline E-Fuels” project
erating minimal CO2 emissions. concluded in 2020, two research insti-
Just one year after the project started, tutes at Friedrich-Alexander University
3 OPTIMIZED FUEL COMPOSITION
it was already evident that admixtures Erlangen-Nuremberg (FAU) and Leibniz
Admixing renewable fuels can quickly again offer additional potential to reduce University in Hanover analyzed spray
result in significant reductions in CO2 CO2 over an increased efficiency in a disintegration of standard gasoline,
emissions throughout the existing fleet. tank-to-wheel observation, TABLE 2. methyl formate (MeFo), ethanol, water
However, up to now there are no or A virtual simultaneous optimization and a water-gasoline emulsion using
FIGURE 1 Comparison of spray structure
of different fuels at an injection pres-
sure of 350 bar (© FAU)
MTZ worldwide 03|2021 65
RESE ARCH F V V Projects
different measuring techniques [5]. systems. The main challenge when ulation processes developed. The project
In a different project, the same analy- designing these engines is the operat- will be concluded in early 2022.
ses were conducted simultaneously on ing behavior in areas close to full load.
future diesel fuels. The spray structure Reducing the temperature through wide-
6 OUTLOOK FOR
was analyzed using a fluorescence open-throttle enrichment is no longer
FURTHER RESEARCH
microscope and x-ray phase-contrast a possibility due to pollutant emissions
imaging. Both procedures show similar and consumption. Water injection rep- The current research on spark-ignition
results: The structure images for gaso- resents an alternative solution here and engines is characterized by the deploy-
line, MeFo and ethanol barely differ, has already been examined as part of ment of new operating materials and
whereas water and the water-gasoline an FVV research project. However, the fuels, and the goal of reducing or even
emulsion display substantially coarser task of achieving the highest possible neutralizing CO2 emissions in real opera-
spray break-up, FIGURE 1. The break-up “water efficiency” still remains. FIGURE 2 tions. Future projects will place even
speed was analyzed using an x-ray shows CFD simulations of the tem greater emphasis on this aspect. Several
contrast process, as well as the new perature fields for the combustion of projects are planned or are currently
camera-based Structural Image Velo RON95E10 and EFR50 H2OE50 incor being started, in which hydrogen com-
cimetry (SIV) technique. The compara- porating Reynolds-averaged Navier- bustion in a reciprocating piston engine
tively easy-to-implement SIV process Stokes (RANS) models [6]. In a subse- is to be analyzed in great detail. FVV
provided sufficiently accurate results. quent project [7], the high-pressure research thus is supporting the hydrogen
Gasoline and ethanol sprays broke up direct injection system (500 bar) and strategies in Germany and Europe by pro-
most quickly, whereas MeFo, the emul- the use of a fuel-water emulsion are viding the technical basis for industrial-
sion and pure water took the longest being investigated. The work also en ization. Other fuels based on processed
time in descending order to break up. compasses other technological compo- green hydrogen, such as methanol, or the
nents for improving evaporation proper- gasoline derived from it are also part of
ties as well as multiple injection strategies. future research projects. The “ICE2025+”
5 WATER INJECTION
In addition, the impact of water injection project mentioned above will be contin-
Engines with high power density for on the oil distribution, exhaust gas after- ued and extended to include operation
particularly sporty vehicles also con treatment and other system components with multiple alternative fuels and lean
tribute to the diversity of future drive are to be examined and the required sim- combustion. At the same time, future
FIGURE 2 Comparison of temperature fields from combustion of RON95E10 (iso-Octane: 40.3 mass-%; n-Heptane: 12.6 mass-%; Toluene: 36.5 mass-%;
Ethanol: 10.6 mass-%) and EFR50 H2OE50 emulsion (iso-Octane: 26.9 mass-%; n-Heptane: 8.4 mass-%; Toluene: 24.3 mass-%; Ethanol: 18.2 mass-%;
Water: 22.2 mass-%) for different crank angles (© BTU)
66 www.springerprofessional.com/automotiveprojects aim to deploy Artificial Intel and Dr.-Ing. André Casal Kulzer (Dr. Ing. h.c. F. (ed.): Proceedings R596, pp. 145-178, Frankfurt am
ligence (AI) methods for engine develop- Porsche AG). RTD performers: Prof. Dr.-Ing. Main, 2020
Michael Bargende (Institute of Automotive Engineer- [6] Netzer et al.: Numerical Analysis of the Impact of
ment, which makes sense solely thanks ing, University of Stuttgart), Prof. Dr.-Ing. Christian Water Injection on Combustion and Thermodynamics
to the significant amounts of data from Beidl (Institute for Internal Combustion Engines and in a Gasoline Engine Using Detailed Chemistry. In:
experiments of previous FVV projects. Powertrain Systems, TU Darmstadt), Prof. Dr.-Ing. SAE International Journal of Engines, Vol. 11(6), pp.
Through the Industrial Collective Peter Eilts (Institute for Combustion Engines, TU 1151-1166, 2018
Braunschweig), Prof. Dr.-Ing. Stefan Pischinger [7] IGF research project “Water Injection in Spark-
Research, Small and Medium-sized (Institute for Combustion Engines, RWTH Aachen Ignition Engines II.” Funding: FVV (1367). Coordina-
Enterprises (SMEs) can also make use University. In: FVV (ed.): Proceedings R590, tor: Dr.-Ing. André Casal Kulzer (Dr. h.c. F. Porsche
of AI-based simulation methods. Sus pp. 333-370, Frankfurt am Main, 2019 AG). RTD performers: Prof. Dr.-Ing. Steffen Müller
[4] IGF research project “Fuel Composition for CO 2 (Specialist Area for Vehicle Powertrains, TU Berlin),
tainability in the sense of the United
Reduction.” Funding: FVV (1348). Coordinator: Dr. Prof. Dr.-Ing. Fabian Mauß (Chair of Thermodynam-
Nations goals also requires that low-CO2 Yoshihiro Okada (Toyota Motor Corporation). RTD ics/Thermal Process Engineering, Brandenburg Uni-
and CO2-neutral engines be designed so performers: Prof. Dr.-Ing. Michael Bargende (Insti- versity of Technology Cottbus-Senftenberg), Prof.
robustly that they can achieve high num- tute of Automotive Engineering, University of Stutt- Dr.-Ing. Michael Bargende (Institute of Automotive
gart), Prof. Dr.-Ing. Karl Alexander Heufer (Physi- Engineering, University of Stuttgart), (unpublished)
bers of operating hours. Research ques-
co-Chemical Fundamentals of Combustion, RWTH
tions regarding operational stability and Aachen University), Prof. Dr.-Ing. Fabian Mauß
new materials – for which FVV has estab- (Chair of Thermodynamics/Thermal Process Engi-
lished a dedicated planning group – neering, Brandenburg University of Technology
Cottbus-Senftenberg), Prof. Dr.-Ing. Heinz Pitsch
will therefore continue to be pursued. (Institute for Combustion Technology, RWTH
Aachen University), Prof. Dr.-Ing. Stefan Pischinger
THANKS
REFERENCES (Institute for Combustion Engines, RWTH Aachen
The Research Association for Combustion Engines
[1] United Nations, Department of Economic and University). (Unpublished)
[5] IGF research project “Spray Diagnostics of would like to express its gratitude to public funding
Social Affairs: The 17 Goals. Online: https://sdgs.
un.org/goals, access: October 14, 2020 Gasoline E-Fuels.” Funding: FVV (1317). Coordinator: bodies and all FVV members for their generous
[2] Umweltbundesamt: Weltweiter Autobestand. Dr.-Ing. Eberhard Kull (Vitesco Technologies GmbH). support of the research activities mentioned in this
Online: https://www.umweltbundesamt.de/bild/ RTD performers: Prof. Dr.-Ing. Michael Wensing report. Our special thanks go to the research institu-
weltweiter-autobestand, access: October 14, 2020 (Institute of Engineering Thermodynamics, Friedrich-
tions, project managers and members of working
[3] IGF research project “ICE2025+: Ultimate Sys- Alexander University Erlangen-Nuremberg), Prof. Dr.
tem Efficiency.” Funding: FVV (1307). Coordinators: Friedrich Dinkelacker (Institute for Combustion Tech- groups and project user committees for their trusting
Dipl.-Ing. Arndt Döhler (Opel Automobile GmbH) nology (ITV), Leibniz University Hanover). In: FVV and excellent cooperation.
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