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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.
 

Science@ifpen
Comparison of measured and calculated soot
quantities for a running engine(b).

 

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.

 


(1)  L. Pickett, D. Siebers, Combustion and Flame, 138: p. 114–135, 2004

(2)  A. Dulbecco, G. Font, SAE Technical Paper 2017-24-0022.
   DOI : 10.4271/2017-24-0022, 2017

 


Scientific contact: alessio.dulbecco@ifpen.fr

>> ISSUE 32 OF SCIENCE@IFPEN