Construction and Study of Ammonia/Hydrogen/Diesel Tri-Fuel Combustion Mechanism
The ammonia/hydrogen/diesel(AHD)tri-fuel combustion mechanism,consisting of 70 species and 392 steps of elementary reactions,was constructed using the Reaction Workbench module in Chemkin software.Chemkin software was utilized to verify the chemical kinetics of the AHD mechanism,and the combustion process and emission under different fuel combustion modes of the engine were also compared and verified by coupling the AHD mechanism with a computational fluid dynamics(CFD)model.The results show that the predicted values of the AHD mechanism for the ignition delay time,laminar flame propagation speed,and the change of the concentration of the oxidized key components of ammonia,hydrogen,and diesel fuel in the jet stirred reactor(JSR)match well with the experimental results.And the average errors are within one order of magnitude.Through the coupling of the CFD model and AHD mechanism,the engine combustion process and emission under the three combustion modes of diesel fuel only,ammonia/diesel fuel,and ammonia/hydrogen/diesel fuel,can be compared and validated under different fuel combustion modes.The simulated values of the engine in-cylinder pressure and the heat release rate under the three combustion modes are in good agreement with the trend of the experimental results,and the maximum errors are all within 10%.Under the rated operating conditions(1 800 r/min),with the increase of hydrogen energy ratio,the ignition delay period is shortened,the combustion rate is accelerated,the CO and hydrogencarbon(HC)emissions gradually decrease,and the NOx emissions tend to increase.
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