The fuel injector is one of the key components of any diesel engine, directly influencing performance, pollutant formation, component heat-loads and reliability (Baumgarten 2006; Heywood 1988). The development and structure of
the fuel jet, which influences ignition and heat-release, is strongly influenced by the flow conditions inside the nozzle
holes, especially if the flow cavitates. Those in-nozzle flow conditions are in turn influenced by flow conditions
both inside the sac-volume and further upstream. A comprehensive understanding of the fuel injection system thus
requires all those aspects to be studied, ideally under transient operation and under realistic operating conditions.