Investigation of the main exhaust emissions of HCCI engine using a newly proposed chemical reaction mechanism for biogas fuel

In this study, the main exhaust emissions from biogas fueled homogenous charge compression ignition (HCCI) engine model were investigated using a newly proposed reaction mechanism. The study was conducted by reducing a full detailed reaction mechanism using a combined algorithm built based on the graph-based approach. The exhaust emissions were estimated using a modified multi-zone combustion model. The chemical kinetics model was built using CANTERA reaction flow package and MATLAB (R) software. The new reduced mechanism (42 species and 228 reactions) showed higher agreement with the experimental data than the GRI-Mech 3.0 mechanism (53 species and 325 reactions). The effects of many parameters on emissions, including the equivalence ratio (0.25-0.4), CH4% (30%-80%), and the inlet intake temperature (420 K-500 K), were investigated. The results indicated that increasing the equivalence ratio above 0.25 increases the NOx emissions significantly as it increases the combustion peak bulk temperature. The same observation was obtained as the intake temperature and the CH4 content were increased above 420 K and 30% respectively and for the same reason. However, CO and unburned hydrocarbons (HC) emissions were decreased significantly as the equivalence ratio increased above 0.25, while they slightly changed with increasing the CH4% and the inlet intake temperature.

Automated summary

Increasing the equivalence ratio above 0.25 significantly increases NOx emissions due to higher combustion peak bulk temperature, while CO and unburned hydrocarbons (HC) emissions decrease significantly at equivalence ratios above 0.25.