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Effect of H2+ O2 Gas Mixture Addition on Emissions and Performance of an SI Engine

Effect of H2+ O2 Gas Mixture Addition on Emissions and Performance of an SI Engine

M.Sc. Karagoz Y., M.Sc. Orak, Assist. Prof. Dr. Sandalci, B.Sc. Uluturk

Department of Mechanical Engineering, Automative Subdivision, Internal Combustion Engines Laboratory– Yildiz Technical University, Turkey


Use of hydrogen in SI engines as additional fuel to gasoline rises as a preferable fuel through both enhanced combustion characteristics, relative lower costs and good applicability hence, storage and production handicaps limit use of hydrogen in road vehicles. In the framework of the study hydrogen was introduced into the inlet manifold, used in ICE as supplementary fuel to gasoline. A set of tests using various amount of hydrogen-oxygen addition has been carried out in order to observe the effects of hydrogen addition on performance and emissions. Three different supplementary fuel which contains 0% H2, 3% H2 + 1.5% O2 and 6% H2 + 3% O2 volume fractions of intake air, were used during the tests where 0% represents pure gasoline. H2/O2 mixture fed into the intake manifold. Results show that higher brake thermal efficiencies, maximum brake torque and power, lower HC and CO emissions are achieved using H2/O2 mixture as additional fuel to gasoline. Also, regarding higher in-cylinder temperature field and higher combustion efficiency,,increased NOx and CO2 emissions were observed.


In the frame work of this experimental study, effects of hydrogen usage as supplementary fuel in SI engines on performance and emissions were investigated. A series of tests with introducing 0%, 3% and 6% H2 and 0%, 1.5% and 3% O2 by volume fractions of intake air into the intake manifold as additional fuel, where 0% H2/O2 addition refers pure gasoline, at half open throttle were conducted. Using hydrogen as supplementary fuel provided improved engine performance and emissions characteristics.

Detailed assessment of test results and conclusions are given as following:

  • Through usage of 6% H2 and 3% O2 mixture as additional fuel, an increase in maximum brake power from 19.09 kW to 20.52 kW at 3500 rpm was achieved. Maximum brake torque was improved from 51.28 Nm to 63.24 Nm with 6% H2/O2 mixture at 2000 rpm engine speed.
  • Through usage of 6% H2 and 3% O2 as additional fuel bsfc is reduced from 372.4 g/kWh to 330.9 g/kWh while thermal efficiency was increased from 21.77% to 24.50% at 2000 rpm engine speed.
  • Maximum HC emission rates at 2000 rpm engine speed reduced from 274 ppm to 84 ppm using 6% H2 and 3% O2 supplementary fuel.
  • Maximum NOx production was increased from 848 ppm to 1297 ppm at 2000 rpm due to higher in-cylinder temperature levels. Lower CO emissions and higher CO2 emissions are observed, consequence of improved combustion.


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