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2 2013

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LES-CMC and LES-Flamelet simulation of non-premixed methane flame (Sandia F)

Tyliszczak A.

Journal of Theoretical and Applied Mechanics

2013

Vol. 51 nr 4

859--871

In this paper, the Large Eddy Simulation (LES) together with the Conditional Moment Closure (CMC) and flamelet combustion models have been applied for modelling of methane flame Sandia F. In the case of the CMC model, both instantaneous and time averaged values predicted numerically agree well with measurements. Attention was devoted to modelling aspects of the conditional scalar dissipation rate (SDR), which is a key quantity of the CMC approach. The two methods of computing SDR are compared with emphasis on a correct prediction of localised extinctions and on their influence on the mean values. It was found that the method of modelling of SDR has rather minor impact on the instantaneous values, whereas larger differences were observed in statistics. In the case of the flamelet model, although it is not able to predict extinctions and re-ignition, the mean values were in good agreement with the experiment.

Assessment of implementation variants of conditional scalar dissipation rate in LES-CMC simulation of auto-ignition of hydrogen jet

Tyliszczak A.

Archives of Mechanics

2013

Vol. 65, nr 2

97-129

In this paper the large eddy simulation (LES) and conditional moment closure (CMC) combustion model have been applied for modelling of auto-ignition of hydrogen jet issuing into a hot ambient co-flow. Most of the attention was devoted to modelling aspects of the conditional scalar dissipation rate which is a key quantity of the CMC model. Two models are compared with emphasis on differences in distributions in mixture fraction space. Analysis of mutual relations between the terms of CMC equations confirms importance of the conditional scalar dissipation rate. It is also shown that model constants are crucial from the point of view of an auto-ignition location and a flame lift off height. The numerical results are compared with experimental data and both the mean and the root mean square fluctuating values of the temperature and species mass fraction agree well with measurements.