Ballistic Imaging in the Primary Breakup Region of Diesel Injector Sprays

摘要

The Colorado School of Mines (CSM) has developed a technique (called ballistic imaging) for single-shot imaging of the near-field primary breakup region of a diesel spray. Ballistic imaging is a non-intrusive optical measurement technique that produces line-of-sight integrated images. These images represent the underlying spray structure in spite of the droplet cloud which surrounds the interior of the spray. Single shot ballistic imaging relies on an ultra-fast optical switch; the optical switch is used to discriminate between ballistic and non-ballistic photons. Note that the ballistic photons contain the image information which appears as a range of extinction levels across the imaging beam. This technique has been applied to the breakup region of a high pressure turbulent water jet and to a high pressure diesel spray directed into the ambient environment. Results from the diesel injection indicate harmonic structure at the spray periphery and downstream voids that possibly are formed due to entrainment. Current work is focused on using this technique with a non-regeneratively amplified laser system (i.e. with a significantly cheaper and more reliable laser system) and on applying the measurement to a diesel spray at diesel relevant conditions using the high temperature and pressure diesel spray facility at CSM.