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Mobility and Systems

Life and death of soot: a model to control the phenomenon

Vehicle approval standards require increasingly high levels of engine performance (low fuel consumption and low emissions) over a broad working range. It is for this reason that new engine architectures incorporate technologies such as direct injection and burned gas recycling systems, two levers for combustion optimization.
    
In this context, engine control strategies are becoming extremely sophisticated, hence increasing recourse to system simulation.
      
However, the complexity of the mechanisms involved in the formation of pollutants in the combustion chamber, particularly soot, makes their detailed incorporation in traditional system simulation approaches difficult.
    
To overcome this difficulty, IFPEN has developed phenomenological models, i.e. based on the physics of phenomena but using more global descriptors.
        
Significant correlations exist between soot emissions and the thermochemical conditions of the fuel-air mixture at known and specific locations within the diesel fuel jet(1): particularly at the lift-off length (region where soot forms) and within the diffusion flame (location of soot oxidation). These factors are themselves directly related to the engine control parameters.
   
This knowledge:

  •  has formed the basis for the development of a model capable of describing such conditions throughout the engine cycle(2),
       
  • and, from this, deducing a quantitative prediction of soot formation (figure).

The model obtained, which also makes it possible to predict the impact of adjustment variations with respect to a given operating point (injection strategy, dilution ratio, turbocharging rate), was incorporated in the IFP-Engine library for the Simcenter AmesimTM a software marketed by Siemens.

The challenge now is to cover a broader range of engine operating conditions, and, in order to do so, to establish the applicability of the correlations employed.

 

a - Multi-physical simulation tool.
   
b - IMEP: Indicated Mean Effective Pressure.   

 

Scientific contactalessio.dulbecco@ifpen.fr

Published in Science@ifpen n° 32 - March 2018

Publications

  1. L. Pickett, D. Siebers, Soot in diesel fuel jets: effects of ambient temperature, ambient density, and injection pressure, Combustion and Flame, Vol. 138: Issues 1–2, July 2004, Pages 114-135.
    >> Doi: 10.1016/j.combustflame.2004.04.006
      
  2. A. Dulbecco, G. Font, Development of a Spray-Based Phenomenological Soot Model for Diesel Engine Applications, SAE Technical Paper 2017-24-0022.
    >> Doi: 10.4271/2017-24-0022, 2017.

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