Injection of Hydrogen Peroxide into the Combustion Chamber of Diesel Engine: Effects on the Exhaust Gas Behaviour

The improvement of the exhaust gas contents of diesel engines with respect to particles and gaseous emissions is still a very important engineering topic. In this work two different direct injection methods into the combustion chamber of a diesel engine have been investigated and compared. The first system involves the separate injection of H₂O₂/water solutions using a second nozzle, while the other is the injection of H₂O₂/water/diesel emulsions by a single injection system. It is known that H₂O₂ forms OH radicals at higher temperatures, whose probability for the oxidation of diesel soot is much higher than that of molecular oxygen [1]. The H₂O₂ injection into the combustion chamber [2] and the exhaust pipe of diesel engines [3] has proved to be an effective measure towards the reduction of diesel soot. A Differential Mobility Analyzer (DMA) is applied to detect the change in particle diameter as function of H₂O₂/water addition. The injected H₂O₂ concentration in relation to injected diesel fuel was varied from 1 to 10 %, and the injection pressure was also varied between 200 and 500 bars. By constant injection pressure and injection timing, it was found that H₂O₂/water/diesel emulsion leads to a higher reduction of unburned hydrocarbons and particulates. Correspondingly, an increase in the NO_x emission is observed in comparison to separate injection of H₂O₂/water solution. The highest reduction of diesel particles was observed at higher injection pressures, and during delay injection timing of H₂O₂/water.