https://orcid.org/0000-0002-1767-8040
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ABSTRACT
In addition to other renewable energy sources being used to minimize the environmental pollution and climate change as well as to satisfy the ever-increasing demands of the society on the energy, biogas is considered abundant resources for energy production. The strategies of using biogas source for internal combustion engines may be a good and potential solution for saving fossil fuel and reducing pollution emission. In this current study, hydroxy (HHO) -enriched biogas under two pathways such as dual injection and blend injection was used to fuel an SI engine aiming to assess the performance (via in-cylinder pressure and indicated cycle work) and emission characteristics (CO and NOx emissions) when the input parameters including HHO/biogas ratios, the position of butterfly valve in the intake manifold, angle of HHO injection were varied. As a result, the dual injection strategy of HHO-enriched biogas produced an advantageous distribution of H2 and CH4 in combustion chamber, which improved combustion efficiency and reduced pollutant emissions. With a fixed HHO injection duration of 2.7 ms, the dual injection led to an increase in HHO concentration at all engine loads, which improved complete combustion in critical operating conditions. Increase of HHO content led to a decrease of optimal advance ignition angle and reduced the range of its variation with engine speed. In closing, HHO addition into biogas was found to improve the engine performance, to reduce CO emission, although it also increases NOx concentration. Biogas enriched by 20% HHO was considered as the best compromise between engine performance and pollution emissions with indicated engine cycle work of 204 J/cyc, CO emission of 0.74%, and NOx emission of 1192 ppm. Moreover, the ignition maps for biogas and HHO were built to point out the optimal range of advance ignition timing for the application purpose to real experiments in the future.
Nomenclature
| °CA | = | Degree crankshaft angle |
| BV | = | Position of butterfly valve (°) |
| HHO | = | Hydroxy, mixture of 2/3 H |
| HRR | = | Heat release rate (J/°CA) |
| MxCy | = | Biogas constituted by 10x% CH |
| n | = | Engine speed (rpm) |
| p | = | Pressure (bar) |
| SI | = | Spark ignition |
| T | = | Temperature (K) |
| tbio | = | Biogas injection time (ms) |
| tHHO | = | HHO injection time (ms) |
| TDC | = | Top dead center |
| V | = | In-cylinder volume (liter) |
| Wi | = | Indicated work cycle (J/cycle) |
| φ | = | Equivalence ratio |
| φ | = | Crankshaft angle (°CA) |
| φHHO | = | Angle of HHO injection (°CA) |
| φs | = | Advanced ignition timing (°CA) |
| φso | = | Optimal advance ignition timing (°CA) |
Acknowledgments
The authors wish to express their appreciation to the Ministry of Education and Training for supporting this research via the Ministerial project of Science and Technology “Waste-to-Power modular through RDF produced from solid waste in rural area.”