An enhanced flamelet generated manifold (FGM) model for large eddy simulation (LES) of turbulent spray combustion is presented. In the enhanced FGM model, a transported probability density function (TPDF) description of the FGM variables is employed. The TPDF is represented using the Eulerian stochastic fields (ESF) approach, and the method is applied to LES of spray combustion under conditions relevant to internal combustion engines. The new ESF/FGM method achieves an improved accuracy of predictions due to the ESF modeling of the subgrid scale turbulence-chemistry interaction. It also achieves high computational efficiency due to the FGM tabulation of the chemical kinetic mechanism. The performance of the new ESF/FGM model is assessed by simulation of the Spray-A flames from Engine Combustion Network (ECN) and comparison of the results, firstly, with experimental measurements, and secondly, with conventional FGM model simulation results. It is shown that the ESF/FGM method is capable of predicting both global and local combustion characteristics, i.e., pressure rise, ignition delay time, flame lift-off length and the thermo-chemical structure of the spray flames with improved accuracy compared to the conventional FGM model that is based on the presumed PDF description of FGM variables. The sensitivity of the predictions using ESF/FGM to the number of stochastic fields is examined by varying the number of these fields in the range of 4–128. Furthermore, the influence of different FGM reaction progress variables on the simulations is investigated, and a new reaction progress variable based on the local consumption of oxygen is proposed. The results show that the new progress variable improves predictions of spray combustion, including the prediction of the start of injection, the quasi-steady state liftoff length, the post-injection oxidation, and the pressure evolution.
Bibliographical noteFunding Information:
This work was sponsored by the Swedish Research Council (VR). AH was partially sponsored by Scania CV AB. SX and YZ were partially sponsored by the China Scholarship Council (CSC). The simulations were performed on NSC, HPC2N and PDC provided by the Swedish National Infrastructure for Computing (SNIC).
- Spray combustion
- Flamelet generated manifold (FGM)
- Eulerian stochastic fields (ESF)
- Reaction progress variable
- Engine combustion network (ECN)
ASJC Scopus subject areas
- Chemical Engineering(all)
- Mechanical Engineering
- Physical and Theoretical Chemistry