For more information please go to the conference website 
rs-les4ice.com
 
Further improving the environmental performances of 
internal combustion engines (ICE) increasingly requires 
moving beyond traditional design based on a cycle averaged 
approach (RANS), and to reliably predict and control 
individual engine cycles under realistic operating 
conditions. Large-Eddy Simulation (LES) offers this unique 
potential and opens up new avenues for extending the scope 
of application of CFD for ICEs,

Since its 1st edition in 2008, the biannual LES4ICE 
conference provides a forum for exchange concerning 
research and development of LES and related experimental 
techniques for their application to ICE flows.
It brings together researchers and engineers working in the 
field of piston engine combustion to debate the state of 
the art in LES applied to ICEs and examine advanced 
experimental techniques capable of supporting and 
validating its development.

Published research in recent years has demonstrated the 
ability of LES to yield an unprecedented detailed insight 
into non- cyclic characteristics of flow and combustion in 
ICE. In particular, its application to spark-ignition 
research engines was shown to reproduce experimental 
findings on cyclic variability of intake flow, its 
interaction with direct fuel injection, and on the 
resulting cyclic combustion variability (CCV). First 
attempts also concerned the exploitation of such advanced 
simulations in order to identify the sources of flow and 
combustion variability in an effort to limit them by design 
in the future. Recent work also showed the potential of LES 
to provide an unprecedented insight into the link between 
CCV and knock. LES not only allowed a quantitative 
prediction of knock intensity and limits, but also yielded 
a detailed insight into the phenomena at stake and in 
particular on destructive knocking modes related to a 
coupling between auto-ignition and acoustic waves inside 
the cylinder.
Despite less prominent, the development and application of 
LES to study Diesel spray combustion has also received 
increasing attention, in relation to the important 
collaborative research effort undertaken in the frame of 
the Engine Combustion Network (ECN).

Despite the present and foreseeable progress in terms of 
supercomputer performance, LES meshes compatible with a 
practical usage will still be far from resolving all the 
relevant space and time scales of ICE flows. Reliable LES 
predictions in a realistic time frame thus still require 
the availability of sub-grid scale models able to 
accurately reproduce the effects of unresolved scales. 
Although it can be considered that existing models already 
allow addressing many of the phenomena at stake, further 
research is required to increase the reliability and domain 
of application of LES methods.
Published research indicates that sub-grid scale models for 
turbulence alleviating the need for an a priori choice of 
model constants proved efficient to predict the complex 
internal aerodynamics during the full engine cycle. 
However, the accurate modelling of unresolved near-wall 
flow still requires dedicated research work aimed at 
ensuring an accurate prediction of wall friction, heat 
losses and turbulence generation, at a cost compatible with 
a practical usage.
Widely used Discrete Particle Methods are reported to yield 
satisfactory predictions of fuel sprays under engine 
condition, as even coarse meshes allow resolving a part of 
the generated flow entrainment and resulting convective 
mixing in LES. Eulerian/Eulerian approaches are essentially 
used in LES of the flow inside injectors or near the nozzle 
exit. Such detailed in-nozzle flow LES could in particular 
allow an accurate imposition of unsteady injector outflow 
conditions necessary to yield accurate LES of the fuel 
spray. On-going research concerns all aspects of high 
pressure fuel injection, the coupling between different 
approaches used in specific flow regions, the modelling of 
super-critical thermodynamic conditions, or the formation 
of liquid wall films and related pool fires.
In terms of engine combustion, published models for spark 
ignition, premixed turbulent flame propagation based on 
flamelet approaches, and inexpensive pre-tabulated 
chemistry approaches to fresh gases’ auto-ignition were 
shown to allow addressing key phenomena. On-going research 
topics concern further improvements in the modelling of the 
early phases of spark ignition of importance for predicting 
minimum ignition energy or misfires, turbulent combustion 
models valid outside the flamelet regime in order to 
address highly diluted and leaned-out combustion and 
increased turbulence levels, or the formulation of advanced 
turbulence-chemistry interaction models that combine 
accurate turbulent combustion models with detailed auto-
ignition or pollutant chemistry.

LES attracts increasing interest from the automotive 
industry in relation to its potential of increased 
predictivity and of extending the domain of application of 
CFD to non-cyclic flow and combustion phenomena not yet 
addressed in early design phases. /In this context research 
work must address methodological aspects aimed at ensuring 
reliable and accurate LES results without a priori 
experimental knowledge. Another key aspect is the 
development of  numerical methods allowing to reduce 
related pre-processing and return times in order to make 
them compatible with an industrial usage. 
There also is a need for methods allowing extracting 
meaningful information from the important amount of data 
generated in LES, but also in engine experiments. This is 
essential to be able to efficiently exploit such complex 
databases in order to gain a better understanding of 
phenomena at stake in non-cyclic engine combustion and to 
support the formulation of reduced order models to be used 
in industrial design processes.

Finally, a successful LES research is strongly dependent on 
the availability of dedicated high-resolution quantitative 
experimental techniques, and on their application to 
detailed studies of engine flow and combustion under 
realistic operating conditions. Such experimental research 
is not only necessary to yield validation data, published 
recent research also exemplified how a combined usage of 
LES and advanced diagnostics could truly yield an 
unprecedented detailed insight into presently poorly 
understood and mastered engine phenomena.

LES4ICE aims at proposing its participants the unique 
opportunity to keep up with the relevant worldwide research 
in these fields.


Topics

Applications to ICE
* LES for predicting & understanding non-cyclic 
engine phenomena: cyclic combustion variability, fast 
transients, extreme cycles, rare events, …
* Predicting and characterising abnormal combustion 
(knock, superknock) with LES
* Detailed LES studies of interactions between intake 
aerodynamics, fuel injection and combustion
* LES of in-nozzle injector flows and its link to 
fuel sprays
* High-fidelity LES of mixture preparation and 
combustion phenomena

Experiments for LES
* Combined usage of advanced diagnostics and LES for 
yielding a better understand and mastering of  ICE flows
* Methods allowing to extract meaningful information 
from large experimental and LES databases
* Experimental techniques with a potential for 
supporting the development of LES
* Experimental databases for validating LES 
(simplified geometries and engines)

LES methodology
* Numerical methods adapted for LES
* Quality criteria for LES of ICE flows
* Mesh convergence studies of LES for ICE
* Comparing & validating LES with experimental 
evidence
* UQ adapted for LES of ICE

LES models for ICE flows
* Sub-grid scale turbulence
* Accounting for turbulent wall boundary layers
* Fuel injection & fuel spray modelling
* Turbulence-chemistry interaction
* Accounting for detailed chemistry in LES