In an earlier study, a novel type of diesel fuel injector was proposed. This prototype injects fuel via porous (sintered) micro pores instead of via the conventional 6-8 holes. The micro pores are typically 10-50 micrometer in diameter, versus 120-200 micrometer in the conventional case. The expected advantages of the so-called Porous Fuel Air Mixing Enhancing Nozzle (PFAMEN) injector are lower soot- and CO2 emissions.
However, from previous in-house measurements, it has been concluded that the emissions of the porous injector are still not satisfactory. Roughly, this may have multiple reasons. The first one is that the spray distribution is not good enough, the second one is that the droplet sizing is too big due to the lack of droplet breakup. Furthermore air entrainment into the fuel jets might be insufficient. All reasons lead to fuel rich zones and associated soot formation.
To acquire more insight into the spray of the porous injector, several PFAMEN nozzles have been produced and investigated. The momentum of the spray was found to be an order of magnitude lower compared to conventional injectors. Afterwards, the porous injector was placed in an optically accessible engine, allowing the analysis of the spray development and combustion process. The main conclusion is that the spray penetration depth is relatively low. Finally, droplet size and velocities are presented using Phase Doppler Anemometry (PDA) and from these measurements it became clear that the droplets of the PFAMEN nozzle are larger compared to conventional injectors. This is believed to be caused by the low exit velocities.