Modeling Diesel Spray, Combustion and Emission with GTEA Numerical Code 2019-01-0004
A detailed chemistry-based CFD model (GTEA, General Transport Equation Analysis) was developed to simulate the diesel spray, combustion and emission process. The model incorporates an improved droplet tracking model, the Hybrid breakup model that consider the influence of turbulence inside the nozzle, the reaction mechanism of n-decane that coupled with a reduced NOx mechanism, the phenomenological soot model, a modified dynamic mesh model, a spray/wall impingement model, and other improved submodels in the GTEA codes. The model was first applied to predict the diesel spray process. The computational results demonstrate that the model is capable of predicting the fuel spray process with satisfactory, and the improved agreement is attributed to the ability of the new Hybrid breakup model to account for the effects of turbulence inside the nozzle, which enhance the spray process. Then the model was applied to investigate the ignition delay and flame lift-off length under different ambient conditions. The overall trend of ignition delay and lift-off length with the variation in different conditions was well reproduced by the model. It was found that the ignition delay and lift-off length are a function of ambient density, ambient temperature and oxygen concentration, respectively. This part study also shows that the longest ignition delay time has the longest lift-off length. Finally, the model was employed to simulate the combustion and emission characteristics of a low-temperature combustion (LTC) engine. Good levels of agreement in cylinder pressures under different EGR conditions were obtained. Predictions of soot and NOx emission were also performed and a good quantitative agreement between measured and simulation.
Wenliang Qi, Pingjian Ming, Aisha Jilani, Ye Peng
Harbin Engineering University
International Powertrains, Fuels & Lubricants Meeting