The concurrent combustion of Diesel and hydrogen in a 1999 Cummins ISM 370 heavy-duty compression ignition engine was computationally investigated using a three-dimensional (3-D) computational fluid dynamics (CFD) solver and compared to literature reference data of the engine operated at 1200 rpm and 70% load. Multiple computational combustion models and chemical mechanisms spanning from global single-step kinetic reaction mechanisms, equilibrium reactions, to detailed reduced mechanisms of 118 to 128 reversible kinetic reactions were considered, along with several chemistry solvers of varying levels of sophistication. The results showed that all models based on single-step global kinetic Diesel mechanisms failed to accurately predict ignition timing, leading to significant overprediction of the maximum in-cylinder pressures. The detailed mechanisms were able to predict ignition delay, maximum in-cylinder pressure within 2%, and crank angle of maximum pressure within 0.5 ° CA. Finally, the detailed mechanisms were artificially decoupled from the Diesel and hydrogen reaction mechanisms by creating dummy species to prohibit any communication between the hydrogen and Diesel mechanism. Decoupling of the hydrogen and Diesel chemistry failed to fully ignite and combust the mixture. Therefore, the results strongly suggest that there is a significant direct chemical interaction between the Diesel and hydrogen radical pools and intermediate species. These interactions are crucial for accurate modeling of the combustion process. Simplified 1-D constant volume combustion simulations suggested that the exchange of hydrogen peroxide (H2O2) produced by the initial Diesel reactions provides a shortened reaction path for the hydrogen combustion, resulting in accelerated heat release, which, in turn, increases the Diesel reaction rate. Therefore, chemistry models for Diesel/hydrogen co-combustion simulations consisting of independent global reactions for hydrogen and Diesel combustion, respectively, without communication between these reactions should only be used with great caution.
Chemical Kinetic Modeling of Hydrogen-Diesel Co-combustion in Compression Ignition Engines
Sae Int. J. Fuels Lubr
Sae International Journal of Fuels and Lubricants
Sae International Journal of Fuels and Lubricants ; 15 , 3 ; 235-254
2022-03-03
20 pages
Conference paper
English
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