Evaluation of Diesel Spray Momentum Flux in Transient Flow Conditions

In the present paper, a detailed numerical and experimental analysis of a spray momentum flux measurement device capability is presented. Particular attention is devoted to transient, engine-like injection events in terms of spray momentum flux measurement. The measurement of spray momentum flux in steady flow conditions, coupled with knowledge of the injection rate, is steadily used to estimate the flow mean velocity at the nozzle exit and the extent of flow cavitation inside the nozzle in terms of a velocity reduction coefficient and a flow section reduction coefficient. In the present study, the problem of analyzing spray evolution in short injection events by means of jet momentum flux measurement was approached. The present research was based on CFD-3D analysis of the spray-target interaction in a momentum measurement device. After a proper validation with experimental data (impact force time-history, spray penetration and cone angle obtained by spray imaging), the detailed analysis of the 3D flow field in different rig configurations and operating conditions led to significant awareness of the spray momentum measurement device operation. The obtained results suggest that a properly designed momentum rig can be used for quantitative characterizations of the instantaneous momentum flux for each single jet in engine-like injection conditions, which are mostly important for the combustion process evolution in low-load conditions.