SPRAY CHARACTERISTICS AND SPRAY-WALL IMPINGEMENT OF A DIESEL-CNG DUAL FUEL JET USING THE SCHLIEREN IMAGING TECHNIQUE

Natural gas for direct-injection (DI) compression ignition (CI) engines is considered
to be the final optimized method due to its high volumetric efficiency, high thermal
efficiency and low emissions. However, CNG has the penalty of high auto-ignition
temperature and lower cetane number. An effective way to use CNG in CI engines is
to inject the CNG with a pilot of diesel fuel for ignition purposes. In order to
understand and control the injection and the jet characteristics, it is essential to
understand how the gas jets assist the atomization of the pilot diesel spray and
influence its characteristics as well as wall impingement.