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Engine knock reduction: the fundamental contribution of LES: Anthony Robert, winner of the 2015 Yves Chauvin thesis prize

December 2015

On Thursday 25 November 2015, Anthony Robert was handed the 2015 Yves Chauvin thesis prize by Sébastien Candel, Chairman of IFP Energies nouvelles' (IFPEN) Scientific Board, for his thesis entitled: "Large-Eddy Simulation of abnormal combustion in downsized spark ignition engines".

From left to right: Eric Heintzé (IFPEN), Sébastien Candel (IFPEN), Pierre-Henri Bigeard (IFPEN), Anthony Robert (award winner), Stéphane Richard (Turbomeca), Clément Dumand (PSA), Olivier Colin (IFPEN), Benoît Enaux (PSA).

Anthony Robert's thesis falls within the scope of IFPEN's research aimed at developing downsizing, a promising powertrain concept. In particular, this work gave rise to the ANR (French National Research Agency) collaborative research project, ICAMDAC, bringing together academic (Toulouse Institute of Fluid Mechanics, PRISME University of Orléans) and industrial (Peugeot Citroën Automobiles, Renault SAS) players. The objective? To address the dual environmental and energy concerns relating to air pollution and the reduction of road vehicle fuel consumption[1].

The technology combines downsizing with high-pressure turbocharging, with a view to increasing the efficiency of gasoline engines and reducing their CO2 emissions. The expected benefits are numerous: compliance with future pollutant emission standards, reduced fuel consumption and improved performance. But ineffectively managed combustion phenomena are undermining the reliability of this innovation.

The more severe thermodynamic conditions encountered in downsized engines promote the development of abnormal combustion (knock and super-knock), due to areas of self-ignition of fresh gas upstream of the flame front. This results in serious risks of mechanical failure, which, as well as being unacceptable, complicate the resolution of the problem since they make experimental studies extremely difficult.

Numerical simulation is an essential tool since it facilitates the understanding of knock phenomena. Anthony Robert's thesis focused, in particular, on an innovative form of LES[2].

The research was carried out using the 3D AVBP[3] code, developed jointly by IFPEN and CERFACS[4]. The studies demonstrated the representativity of this LES compared to experimental results obtained at IFPEN, both in terms of "cycle to cycle" variability and in terms of knock frequency, its intensity and the moment at which it occurs during the cycle.

A broad variety of scenarios were highlighted depending on the cycles and local conditions in the combustion chamber, a result that would have been impossible to obtain through experimentation.

Moreover, LES has proved itself to be an invaluable tool in terms of facilitating an in-depth understanding of the physical phenomena at play. It is thus possible to locate the main zones triggering self-ignition.

Location of the flame (red) and of self-ignition (black) during an engine cycle.

It can also be used to monitor – for each engine cycle and at any time – the position of the flame and of uncontrolled self-ignition. The occurrence of a transition towards detonation has thus been confirmed during certain cycles and appears to be the cause of very high-intensity, often destructive knock, recorded while the engine is running.

LES is thus a powerful tool to help powertrain engineers gain a better understanding of phenomena inside combustion chambers, with a view to improving their products. This work is a perfect illustration of IFPEN's positioning across the entire chain from fundamental research to industry, serving the energy transition.

Anthony Robert carried out his thesis at IFPEN within the context of an industrial agreement for training through research (CIFRE) with PSA Peugeot Citroën. It was jointly supervised by Thierry Poinsot of INP Toulouse and Olivier Colin from IFPEN's Powertrain and Vehicle division


  • A. Robert, S. Richard, O. Colin, T. Poinsot, “LES study of deflagration to detonation mechanisms in a downsized spark ignition engine”. Combustion and Flame, Elsevier, 2015, 162 (7), p.2788-2807.
    >> DOI: 10.1016/j.combustflame.2015.04.010
  • A. Robert, S. Richard, O. Colin, L. Martinez, L. De Francqueville, “LES prediction and analysis of knocking combustion in a spark ignition engine”, Proc. Combust. Inst. 35 (3) (2014) 2941-2948.
    >> DOI:10.1016/j.proci.2014.05.154
  • A. Misdariis, A. Robert, O. Vermorel, S. Richard, T. Poinsot. Numerical Methods and Turbulence Modeling for LES of Piston Engines : Impact on Flow Motion and Combustion”, Oil & Gas Sci. Technol. - Rev. IFP Energies nouvelles, Vol. 69 (2014), No. 1, pp. 83-105.
    >> DOI: 10.2516/ogst/2013121
  •  A. Robert, L. Martinez, J. Tillou, S. Richard, “Eulerian - Eulerian Large Eddy Simulations Applied to Non-Reactive Transient Diesel Sprays”, Oil & Gas Sci. Technol. - Rev. IFP Energies nouvelles, Vol. 69 (2014), No. 1, pp. 141-154.
    >> DOI: 10.2516/ogst/2013140

As a reminder, this prize, named after Yves Chauvin, winner of the Nobel Prize in Chemistry in 2005, is awarded by IFPEN's Scientific Board to a young doctoral student in recognition of:

  • the scientific excellence of their research work;
  • their contribution to overcoming scientific challenges and developing new concepts.

Each year, on average, some 135 doctoral students are presented and 45 theses are defended at IFPEN.

  1. This research is presented in issue 21 of the scientific newsletter Science@ifpen, dedicated to low-carbon technologies
  2. Large-Eddy Simulation
  3. LES calculation code
  4. European Center for Research and Advanced Training in Scientific Computation

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