Analysis of Diesel Spray Momentum Flux Spatial Distribution

In the present paper the results of an experimental and numerical analysis of a common-rail, high pressure Diesel spray evolving in high counter pressure conditions is reported. The experimental study was carried out mainly in terms of spray momentum flux indirect measurement by the spray impact method; the measurement of the impact force time-histories, along with the CFD analysis of the same phenomenon, gave interesting insight in the internal spray structure. As well known, the overall spray structure momentum flux along with the injection rate measurements can be used to derive significant details about the in-nozzle flow and cavitation phenomena intensity. The same global spray momentum and momentum flux measurement can be useful in determining the jet-to-jet un-uniformities also in transient, engine-typical injection conditions which can assist in the matching process between the injection system and the combustion chamber design. In the present paper, the potential in the internal spray structure analysis by means of local spray momentum flux distribution investigation is evaluated. To obtain such momentum flux distribution maps, a variant in the global spray momentum measurement technique is evaluated. The use of an adaptor to the momentum flux measurement rig is discussed, numerically analyzed and tested on a dedicated experimental bench. Some results pertaining to solenoidactuated common rail injectors are presented and discussed in terms of spray distribution irregularities, momentum profiles and differences in the spray structure obtained for the different jets emerging from the nozzle.