18 research outputs found
RANS modelling of a lifted H2/N2 flame using an unsteady flamelet progress variable approach with presumed PDF
An unsteady flamelet/progress variable (UFPV) approach is used to model a lifted H2/N2 flame in a RANS
framework together with presumed PDF. We solve the unsteady flamelets both in physical space and in
mixture fraction space. We show that in the former case, the scalar dissipation rate profile strongly varies
in time (while it is assumed to be fixed in time in the latter). However, this does not result in significant
qualitative differences in the corresponding flamelet libraries. The progress variable is carefully defined,
including both the main combustion product (H2O) and a key radical species in ignition process (HO2).
The presumed-PDF model is proposed in terms of the non-normalised progress variable, without assuming
its statistical independence with mixture fraction. We introduce a modelled transport equation for
the mean progress variable which is consistent with the basic underlying UFPV assumption, derived from
the Lagrangian flamelet model. The influence of different model parameters on the results for the mean
temperature and mean species mass fractions and their fluctuations is discussed. Good results are
obtained for the conditions of the considered lifted flame where detailed experimental data is available.
However, at low coflow temperature the modelled flame lift-off height is shorter than expected.This work is supported by the Comunidad de Madrid through Project HYSYCOMB P2009/ENE-1597 and by the Spanish Ministry of Economy and Competitiveness under Projects ENE2008-06515-004-02 and CSD2010-00011. This research was also partially supported by the Generalitat Valenciana inside the program Ajudes per a la realitzacio de projectes d'I+D per a grups de investigaclel emergent (Reference GV/2013/041), which is gratefully acknowledged.Naud, B.; Novella Rosa, R.; Pastor EnguÃdanos, JM.; Winklinger, JF. (2015). RANS modelling of a lifted H2/N2 flame using an unsteady flamelet progress variable approach with presumed PDF. Combustion and Flame. 162(4):893-906. https://doi.org/10.1016/j.combustflame.2014.09.014S893906162
Cell Arrangement of Lithium-ion Battery Pack for Improvement in Cooling Performance of Air-Cooled Battery Thermal Management System
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Application of spray combustion simulation in DI diesel engine
This work presents the development and implementation of combustion model for DI diesel engines by using the PDF-Chemical Equilibrium combustion model. The key concept of this approach is to predict the thermochemical variables (e.g., temperature, species mass fractions) and then the average scalars of these variables are evaluated by a probability density function (PDF) averaging approach. To realize flame propagation, the reaction time scale is employed to relax the infinitely fast chemistry of chemical equilibrium. The PDF-Eddy Break Up ignition model is adopted in the auto-ignition calculation. With regard to the comparison results, the simulation results are in good agreement with the experimental results in both ignition and combustion modes. In addition, the predicted lift-off length also corresponds to a power-law scaling of Siebers et al.Combustion Chemical equilibrium Diesel Modelling Spray Simulation