Investigating the combustion, NO emissions and cyclic variability (CCV) in SI engine fueled with ammonia-hydrogen blends by two-zone quasi-dimensional model with two CCV governing mechanisms
Dimitrios Rakopoulos, C.D. Rakopoulos, George Kosmadakis, Wojciech Tutak, Michał Gruca
Abstract
The cyclic variability (CCV) of performance, combustion, and nitric oxide (NO) emissions in spark-ignition (SI) engine fueled with various ammonia-hydrogen blends is investigated, employing previously validated, in-house, quasi-dimensional turbulent-combustion model tracking the flame-front propagation in engine-cylinder, expanded herein to treat ammonia-hydrogen blends. The model is validated successfully at steady-state against experimental data and then enhanced to study behavior of same attributes under CCV conditions comparing against experimental data, considering influence of two governing mechanisms, flame-kernel turbulence and fuel-air ratio variations. The steady-state numerical results included cylinder-pressure (CP), indicated mean effective pressure (IMEP), combustion-stages duration and NO emissions, using for CCV investigation mean-values, coefficients of variation, frequency-distributions and scatter-plot diagrams. The model allows computation of e.g. turbulent-intensity, integral-length and flame-speed, which afford elucidating the effects of ammonia enrichment with hydrogen. The COV of CP and IMEP decrease with hydrogen addition, peak temperatures COV are ∼1 % and for NO up to 40 %.