Conditional source-term estimation (CSE) is a combustion model based on the conditional moment hypothesis where the transport equations for the reactive species are conditionally averaged on a conserved scalar. The primary advantages of this strategy are the reduced spatial dependence of the conditional averages and negligible fluctuations around the conditional averages, which considerably simplify the reaction rate closure. Historically, simulations using CSE are limited to low carbon fuels (i.e. methane and hydrogen) where the reduced chemistry manifold can be constructed through techniques including intrinsic low dimensional manifolds and trajectory generated manifold. However, difficulties were found using such strategies to create manifolds for diesel surrogates. Therefore, in this study, the unsteady flamelet generated manifold is combined with conditional source-term estimation to predict the ignition and flame propagation on n-dodecane.  Simulations are performed on a single-hole injection of n-dodecane under a  range of Engine Combustion Network's "Spray A" conditions. The primary objective of this paper is to assess the ability to combine CSE-FGM model to predict and characterize the diesel spray at low temperature conditions. Simulations are performed under the Reynolds-averaged Navier-Stokes (RANS) and the Large Eddy Simulations (LES) frameworks in a grid-converged Lagrangian spray scenario. The simulation of diesel "Spray A" is qualitatively validated against experimental data from literature, and the efficacy of each model in predicting flame characteristics is evaluated. Overall, it was found that the CSE-FGM model was able to capture global flame properties--- showing particular strength in predicting distinct auto-ignition events in the near nozzle region.


Parametric Studies of a Novel Combustion Modelling Approach for Low Temperature Diesel Spray Simulation

Division / Sponsors: 
Internal Combustion Engine Division (ICED)

Paper Proceedings: https://asmedigitalcollection.asme.org/ICEF/ICEF2020/volume/84034

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