A Review of Engine Fuel Injection Studies Using Synchrotron Radiation X-ray Imaging

Abstract

Fuel spray characteristics directly determine the formation pattern and quality of the fuel/air mixture in an engine, and thus affect the combustion process. For this reason, the improvement and optimization of fuel injection systems is crucial to the development of engine technologies. The fuel jet breakup and atomization process is a complex liquid-gas two-phase turbulent flow system that has not yet been fully elucidated. Owing to the limitations of standard optical measurement techniques, the spray breakup mechanism and its interaction with the nozzle internal flow are still unclear. However, in recent years synchrotron radiation (SR) X-ray imaging technologies have been widely applied in engine fuel injection studies because of the higher energy and brilliance of third-generation SR light sources. This review provides a brief introduction to the development of SR technology and compares the critical parameters of the primary third-generation SR light sources available worldwide. The basic principles and applications of various X-ray imaging technologies with regard to nozzle internal structure measurements, visualization of in-nozzle flow characteristics and quantitative analyses of near-field spray transient dynamics are examined in detail.

An analytical model of diesel injector’s needle valve eccentric motion

“…Another effective approach is to measure the transient needle motion using a high-speed X-ray phaseenhanced imaging (XPCI) technique. 30,31 In Kastengren et al, 32 it was found that the maximum lift within the injectors was linearly related to the rail pressure, which is presumed to be related to the elastic deformation of the needle valve. They also measured the maximum and minimum eccentric radial displacement from four different injectors to be 0.065 and 0.016 mm, respectively.…”

Heat and mass transfer effects in the nozzle of a fuel injector from the start of needle lift to after the end of injection in the presence of fuel dribble and air entrainment

“…Although such elaborate optical studies on realsize nozzles have been very informative, they mostly allowed interpretation of events on the basis of mere observation, not by truly quantitative information of the flow field, amount of in-nozzle vapour, pressure, temperature, etc., neither by providing conclusive evidence on the exact mechanism of nozzle emptying and air backfilling [19,20]. In recent years, X-ray techniques of real all metal injectors have provided further insights into these complex multiphase flow problems [21,22], including some interpretation of needle motion effects on the in-nozzle flow during injection and at the end of injection with quantification of fuel dripping (e.g. [23,24]).…”