Recently, using hydrogen or hydrogen-rich gas as a supplement
fuel for spark ignition and compression ignition engines is one of
the potential solutions for improving brake thermal efficiency,
reducing fuel consumption and pollution emissions from internal
combustion engines. This article investigates the effect of HHO gas
addition on engine performance and emission characteristics.
HHO gas was produced by the electrolysis process of distilled
water and stored in a high pressure tank before injected into the
intake manifold. The experimental study was carried out on a 97 cc
SI engine equipped with two injection systems (HHO gas and addition
air) on the intake manifold. The tests were divided into two cases:
hybrid HHO/gasoline and HHO/gasoline with addition air from second
injection. The experiments showed that, of both cases, compared to
original engine, the engine performance was improved and the
gasoline fuel consumption was declined after enrichment of HHO gas
and of HHO gas/addition air mixture,. The NOx emission
was increased; however,, HC emission was reduced. The CO and CO₂
emissions displayed different trends between the two cases. When
only HHO gas was injected, the CO emission surged due to rich
mixture, while it was decreased after supplying the addition air in
the second case. The CO₂ emission trend was in opposite direction
of CO. The study demonstrated that the effect of HHO gas addition
is most apparent at light loads and lean conditions.