Momentum Flux Spatial Distribution and PDA Analysis of a GDI Spray

In the present paper, the results of a detailed experimental analysis of a GDI spray based on Imaging, Phase Doppler Anemometry data and Momentum Flux distribution measurement are presented and discussed. The GDI system used is a three-hole research injector, operated in an injection pressure range of 50 bar to 150 bar. Spray Imaging is performed according to an ensemble average approach, acquiring images at different timings during the injection process; the resulting penetration and cone angle time-histories allow a quantitative description of the spray structure shape. Momentum flux distribution data are obtained by means of a dedicated test bench which detects the impact force of small spray portions. The sensing device is moved in different positions inside the spray structure, with the acquired force transients averaged on several injection events. By this approach, the mean momentum flux distribution and time-evolution can be derived giving significant insight in the spray structure development. Imaging and momentum flux distribution data are also compared with Phase Doppler Anemometry measurement data in terms of drop velocity, sizing and droplet count distribution inside the spray structure obtained in the same operating conditions. The obtained results suggest that a combined use of the different available experimental techniques allows an adequate quantitative characterization of the spray evolution, if the final goal is to appropriately support a detailed coupling of the spray both with the combustion chamber design and with the in-cylinder charge motions. Further, the obtained experimental data can be used as boundary conditions for CFD analysis of the spray-air charge interaction.