Combustion, performance, regulated and unregulated emissions of a diesel engine with hydrogen addition

• Published in: Applied energy 2014-08, Vol.126, p.1-12
• Main Authors: Zhou, J.H., Cheung, C.S., Leung, C.W.
• Format: Article
• Language: English
• Subjects: Applied sciences; Combustion; Diesel engine; Energy; Energy. Thermal use of fuels; Engines and turbines; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Hydrogen; Particle emission; Unregulated emissions
• ISSN: 0306-2619; 1872-9118
• DOI: 10.1016/j.apenergy.2014.03.089

•Two distinct ULSD–H2 combustion modes are observed at high engine load.•H2 addition can improve the engine performance at medium to high engine loads.•H2 addition is effective in reducing CO2, CO and PM emissions (mass and number).•Influence of H2 addition on NOx emission and NO2/NOx ratio is engine load dependent.•H2 addition is effective in reducing examined unregulated emissions. An experimental investigation was conducted on the combustion, performance, regulated and unregulated emissions of a diesel engine with naturally aspirated hydrogen at the engine speed of 1800revmin−1 under five engine loads. Hydrogen was added to provide 10%, 20%, 30% and 40% of the total fuel energy. Improvement of engine performance can be achieved at medium to high loads. At 90% load, abnormal combustion occurs with more than 30% hydrogen addition as indicated by the drastic increase of peak heat release rate, shortened ignition delay and combustion duration. CO/CO2 and seven kinds of unregulated emissions (except for formaldehyde) can be efficiently reduced. More than 30% of hydrogen addition can reduce the HC emission at low to medium loads. The percentage reduction of NOx emission is engine load dependent, being positive at low loads and negative at high loads. Drastic increase of NO2 is observed at low to medium engine loads. Reductions on particulate mass concentration, particle number concentration and diesel thermal pyrolysis intermediates (olefins and benzene) are associated with the inhibition of polycyclic aromatic hydrocarbons (PAHs) formation. All the unregulated emissions increase at 90% load.