High Speed X-Ray Imaging for Nozzle Exit Velocity and Density Distribution Measurements of GDI Nozzles

Abstract

Investigation of the primary breakup region of gasoline sprays is important for future nozzle development. It improvesthe principal understanding of inner nozzle flow and spray breakup. It also allows validating and developingCFD models. Due to the high optical density common measurement techniques like Phase Doppler Anemometryreach their limit in optical dense sprays as in the primary breakup region. High Speed X-Ray Imaging is capable tomeasure 2D velocity distributions directly at the spray hole exit. For generating the intense X-Ray beam the synchrotronAdvanced Photon Source at Argonne National Laboratory is used. Passing through the spray the X-Raybeam is changed by two different physical principles: absorption and phase contrast. Absorption can be applied tomeasure the density of the spray. Phase contrast is used to visualize the borders of droplets and ligaments withhigh contrast. The accelerated electron bunches inside the synchrotron have a constant period length to each other.This leads to an accurate pulsed X-Ray beam (periodicity: 68 ns). The use of multi exposure with very short X-Raypulses (17 ns) shows the traveled distance of the spray droplets and ligaments. The spray speed (150-250 m/s) iscalculated by dividing these distances with the time gap between two X-Ray pulses. The X-Ray measured densitydistributions and velocity distributions are combined to calculate the spray force rate. The so gained force rate isvalidated with a spray force measurement performed at the Spray Momentum Test Bench (SMTB) at ContinentalAutomotive GmbH. The study is focusing on the measurement setup of High Speed X-Ray Imaging at ArgonneNational Laboratory and the evaluation algorithms.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4598