Work on turbulent combustion modelling has resulted in several models based on different approaches, such as the "flamelet" model or the "probability density function" model. Predictions from both models will need to be compared to experimental data.
This project proposes to compare these two models with detailed experimental data from a turbulent Bunsen flame, a well suited and easily observed experimental set up. The comparison will permit the recommendation of an appropriate method for premixed turbulent combustion in a range of practical applications.
The project will provide a better understanding of the complex turbulence/chemistry interactions during combustion and much of the empiricism on which current chemical-source-term closure models for premixed turbulent combustion are based should be removed.
The role of the coordinator (Prof. Peters, RWTH Aachen) consists in providing the experimental set-up and in performing the Rayleigh measurements of the temperature fields and in defining the experimental conditions at which the turbulent Bunsen flame shall be operated.
In the same flame, LWK (Prof. Renz, RWTH Aachen) will perform the velocity measurements to contribute experimentally to the turbulence models describing reacting flows. The experimental LDA work includes measurements of the mean air flow and the structure of the turbulent motion. Velocity measurements with two-dimensional two-channel systems will be carried out before the optical set-up is modified to measure length scales of the turbulent motions. The results obtained near nozzle exit of the burner will be used as input data for the numerical calculations, whereas the measurements obtained in the flame will be compared with the predicted values.
Prof. Borghi's group (Rouen) will contribute to the closure of a pdf transport equation solved either using the "PEUL-Diffusion" approximation or the Monte Carlo method.
In a second modelling approach, a scalar dissipation equation will be considered. The Cambridge group (Dr. Rogg) will derive flamelet models for premixed turbulent combustion. A first model is based on a field equation for a mean scalar whose iso-surfaces will represent the instantaneous position of the flame front in the turbulent flow field and whose variance will account for the flame brush thickness.
A second model will determine the flame propagation by a convective-diffusive reactive equation which balances the turbulent flame surface area to volume ratio. Calculations done with the theoretical models will be compared to the experimental data.
At the University of Aix-Marseille (Prof. Clavin) fundamental work concerning turbulent flame propagation will be developed in order to critically assess the approximations of the different combustion models.
Warsaw University (Prof. Wolanski) will provide accurate experimental measureme of the flame propagation in premixed gaseous charge under different intensity and scale
Turbulence will be measured by hot-wire anemometry and flame propagation by high speed photography.
These data will allow the verification of the laminar flamelet model for premixed turbulent combustion.
Funding SchemeCSC - Cost-sharing contracts
CB2 1PZ Cambridge