Flame chemiluminescence and OH LIF imaging in a hydrogen-fuelled spark-ignition engine

• Published in: International journal of hydrogen energy Vol. 37; no. 2; pp. 1797 - 1812
• Main Authors: Aleiferis, P.G., Rosati, M.F.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.01.2012; Elsevier
• Subjects: Alternative fuels. Production and utilization; Applied sciences; Energy; Energy. Thermal use of fuels; Engines and turbines; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Flame chemiluminescence; Fuels; Hydrogen; Hydrogen combustion; OH Laser Induced Fluorescence; Spark ignition engines; Hydrogen combustion; OH Laser Induced Fluorescence; Spark ignition engines; Flame chemiluminescence
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2011.10.010

Research into novel internal combustion engines requires consideration of the diversity in future fuels in an attempt to reduce drastically CO2 emissions from vehicles and promote energy sustainability. Hydrogen has been proposed as a possible fuel for future internal combustion engines. Hydrogen’s wide flammability range allows higher engine efficiency with much leaner operation than conventional fuels, for both reduced toxic emissions and no CO2 gases. This paper presents results from an optical study of combustion in a spark-ignition research engine running with direct injection and port injection of hydrogen. Crank-angle resolved flame chemiluminescence images were acquired and post-processed for a series of consecutive cycles in order to calculate in-cylinder rates of flame growth. Laser induced fluorescence of OH was also applied on an in-cylinder plane below the spark plug to record detailed features of the flame front for a series of engine cycles. The tests were performed at various air-to-fuel ratios, typically in a range of φ = 0.50–0.83 at 1000 RPM with 0.5 bar intake pressure. The engine was also run with gasoline in direct-injection and port-injection modes to compare with the operation on hydrogen. The observed combustion characteristics were analysed with respect to laminar and turbulent burning velocities, as well as flame stretch. An attempt was also made to review relevant hydrogen work from the limited literature on the subject and make comparisons were appropriate. ► Flame chemiluminescence and OH LIF images were acquired in a hydrogen engine. ► Flame expansion speeds with direct injection were 25–40 m/s for ϕ = 0.5–0.83. ► Combustion was slower with port injection showing peak expansion speeds 10–20 m/s ► Flame stretch was in the range 5000–10,000 s−1 for flames up to 5 mm in radius. ► Flames showed distortion on a planar macro scale depending on injection/spark timings.