An Insight on Kinetic Mechanisms of Diesel Fuel Surrogate n-dodecane for the Simulation of Combustion Recession 2019-01-0202
Combustion recession, an end of injection diesel spray phenomena, has been found to be a robust correlation parameter for UHC in diesel LTC strategies. Previous studies have shown that the likelihood of capturing combustion recession in numerical simulations is highly dependent on the details of the low-temperature chemistry reaction mechanisms employed. This current study aims to further the understanding of the effects of different chemical mechanisms in the prediction of combustion recession. Studies were performed under the Engine Combustion Network's (ECN) "Spray A" conditions using the Reynolds-Averaged Navier-Stokes simulation (RANS) and the Flamelet Generated Manifold (FGM) combustion model using five different chemical mechanisms for n-dodecane that are commonly used in the engine simulation communities---including two recently developed detailed chemistry mechanisms from Narayanaswamy et al. (255 species and 2289 reactions) and Ranzi et al. (130 species and 2395 reactions). The flamelet database for each of the chemical mechanisms was generated by simulating the 0D ignition flamelets and the 1D counterflow diffusion flamelets. The effect of the chemical mechanisms on the prediction of combustion recession is detailed. Further discussion includes an evaluation of the performances of chemical mechanisms to predict the most relevant reacting spray characteristics compared to ECN experimental database: ignition delay time (IGT), flame lift-off length (LOL) and flame reactive region. Results show that the choice of detailed/reduced chemical mechanism plays a significant role in both initial flame stabilisation and EOI transient phenomenon.
Xiaohang Fang, Riyaz Ismail, Martin Davy