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Importance of Turbulence-chemistry Interactions in Predicting Spray A End of Injection Phenomenon
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on April 14, 2020 by SAE International in United States
In this study, the role of turbulence-chemistry interaction in diesel spray auto-ignition, flame stabilisation and end of injection phenomenon is investigated under engine relevant Spray A conditions. A recently developed diesel spray combustion modelling approach, conditional source-term estimation (CSE-FGM), is coupled with Reynolds-averaged Navier-Stokes simulation (RANS) framework to study the details of spray combustion. The detailed chemistry mechanism is included in this approach through the flamelet generated manifold (FGM) method. Both unsteady and steady flamelet solutions are included in the manifold to account for the auto-ignition process and subsequent flame propagation in a diesel spray. Conditionally averaged chemical source terms are closed by the conditional scalars obtained in the CSE routine. Both non-reacting and reacting spray jets are computed over a wide range of Engine Combustion Network (ECN) diesel Spray A conditions. The reacting results are compared with simulations using homogeneous reactor combustion model and flamelet combustion model with the same chemical mechanism. The present study represents the first application of CSE for a diesel spray. The non-reacting liquid/vapour penetration, the mean and rms mixture fraction, the reactive region, the flame lift-off and the ignition delay show a good agreement with the measurements from the optical engine over a wide range of tested conditions. The CSE-FGM model also shows a better capability in predicting the end-of-injection events in diesel spray combustion. Overall, the CSE-FGM is able to capture the experimental trends well, both quantitatively and qualitatively.