Abstract
Diesel engines are inevitable parts of our daily life and will be in the future. Expensive after-treatment technologies to fulfil normative legislations about the harmful tail-pipe emissions and fuel price increase in recent years created expectations from researchers for alternative fuel applications on diesel engines. This study investigates hydrogen as additive fuel in diesel engines. Hydrogen was introduced into intake manifold using gas injectors as additive fuel in gaseous form and also diesel fuel was injected into cylinder by diesel injector and used as igniter. Energy content of introduced hydrogen was set to 0%, 25% and 50% of total fuel energy, where the 0% references neat diesel operation without hydrogen injection. Test conditions were set to full load at 750, 900, 1100, 1400, 1750 and finally 2100 r/min engine speed. Variation in engine performance, emissions and combustion characteristics with hydrogen addition was investigated. Hydrogen introduction into the engine by 25% and 50% of total charge energy reveals significant decrease in smoke emissions while dramatic increase in nitrogen oxides. With increasing hydrogen content, a slight rise is observed in total unburned hydrocarbons although CO2 and CO gaseous emissions reduced considerably. Maximum in-cylinder gas pressure and rate of heat release peak values raised with hydrogen fraction.
Highlights
Depletion of fossil fuels due to increase in energy demand causes fuel prices to rise; stringent emission regulations as a result of environmental concern create pressure on researchers in alternative fuel science
Fuel injection advance of the test engine was 22° crank angle before top dead centre (TDC), and hydrogen injection advance was set to the start of intake stroke
brake-specific fuel consumption (BSFC) and equivalent diesel fuel quantity obtained from hydrogen’s lower specific value are added to consumed diesel fuel quantity and results are found in terms of diesel fuel
Summary
Depletion of fossil fuels due to increase in energy demand causes fuel prices to rise; stringent emission regulations as a result of environmental concern create pressure on researchers in alternative fuel science. Advances in Mechanical Engineering technology, particulate matter (PM) fraction in tailpipe emissions increased.[2,3,4] According to air quality report in Europe,[1] PM ( 10 mm) emissions increased by (beyond the predetermined levels legislated by World Health Organization) 43% in concentrated traffic zones, 38% in urban regions, 25% in industrial regions and even 15% in rural regions. Main reason of this situation is increase in diesel engine equipped vehicles.[1]
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