Formation-Destruction of Pollutants in Turbulent Flames
Soot particle volume fraction field in a turbulent flame,
obtained by laser incandescence
Mechanisms resulting in the formation of pollutants in turbulent flames were studied in three activities:
Experimental study of a confined turbulent diffusion flame (confinement necessary for varying the pressure)
Modeling of turbulent flames including the calculation of polluting
species
Experimental study of a flame generated by a series of droplets of fuel with perfectly calibrated size and speed.
The study produced the following results:
The effects of turbulence, pressure and radiation losses on the production of nitrous oxides and soot particles in an ethylene-air flame have been understood and quantified.
Turbulent diffusion flames and flames generated by a series of
droplets have been the subject of fine optical measurement campaigns
(DRASC, LIF on OH or NO, laser induced incandescence).
Numerical tools have been created and validated for calculating the
radiative transfer and pollutant concentrations in turbulent flames,
based on realistic physical models.
Flame calculations including all the "turbulence-kinetics chemical-transfers by radiation" couplings have been performed and compared to measurements. These calculations copy reality with reasonable accuracy.
This research was conducted as part of an Onera federating research project (PRF) involving the following Onera departments and external laboratories:
DEFA (Fundamental and
Applied
Energetics
Department, the project's main contractor),
DMAE (Aerodynamics and Energetics Modeling Department),
DMPH (Instrumentation and Sensing Department),
the DLR (Deutsches Zentrum für Luft- und Raumfahrt, Germany),
the CORIA (CNRS Rouen).
Research techniques
The turbulent diffusion flame was studied on the combustion test bench of the Reactive flows and their research techniques laboratory (LAERTE).
Advanced optical diagnostic tools were used:
2D visualization by LIF on the OH radical and NO molecule,
Temperature measurements by CARS,
Soot concentration measurements by laser induced incandescence.
The combustion model is based on solving the probability density function (PDF) transport equation characterizing the flow by a Lagrangian technique.
The radiative transfers in a turbulent environment are described by a Monte Carlo type approach that considers the reciprocity principle for the optical paths.
Numerical simulation of a diffusion flame
(temperature and reaction rate)
