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

Abstract

[EN] Investigation of the primary breakup region of gasoline sprays is important for future nozzle development. It improves the principal understanding of inner nozzle flow and spray breakup. It also allows validating and developing CFD models. Due to the high optical density common measurement techniques like Phase Doppler Anemometry reach their limit in optical dense sprays as in the primary breakup region. High Speed X-Ray Imaging is capable to measure 2D velocity distributions directly at the spray hole exit. For generating the intense X-Ray beam the synchrotron Advanced Photon Source at Argonne National Laboratory is used. Passing through the spray the X-Ray beam is changed by two different physical principles: absorption and phase contrast. Absorption can be applied to measure the density of the spray. Phase contrast is used to visualize the borders of droplets and ligaments with high 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-Ray pulses (17 ns) shows the traveled distance of the spray droplets and ligaments. The spray speed (150-250 m/s) is calculated by dividing these distances with the time gap between two X-Ray pulses. The X-Ray measured density distributions and velocity distributions are combined to calculate the spray force rate. The so gained force rate is validated with a spray force measurement performed at the Spray Momentum Test Bench (SMTB) at Continental Automotive GmbH. The study is focusing on the measurement setup of High Speed X-Ray Imaging at Argonne National Laboratory and the evaluation algorithms.