Search Results

Currently, high-pressure fuel systems and swirl injectors dominate direct injection spark ignition (DISI) engine applications worldwide. Besides its advantage of good atomization due to the high pressure, this technology also has many inherent drawbacks, such as, high system cost, complicated system configuration, excessive wall wetting, lack of spray tailoring flexibility, etc., which limit the benefits available from the DISI concept. To overcome these drawbacks, a low-pressure direct injection (LPDI) fuel injector was developed which utilizes a novel high-turbulence nozzle to produce a soft spray, with droplet size comparable to the high-pressure swirl injector sprays, but much reduced penetration. This unique nozzle design provides a degree of independent control of injector flow, spray droplet size, spray angle, penetration, and spray distribution pattern.

Nozzle length has been proven influencing fuel spray characteristics, and subsequently fuel-air mixing and combustion processes. However, almost all existing related studies are conducted when fuel is subcooled, of which fuel evaporation is extremely weak, especially at the near nozzle region. In addition, injector tip can be heated to very high temperature in SIDI engines, which would trigger flash boiling fuel spray. Therefore, in this study, effect of nozzle length on spray characteristics is investigated under superheated conditions. Three single-hole injectors with different nozzle length were studied. High speed backlit imaging technique was applied to acquire magnified near nozzle spray images based on an optical accessible constant volume chamber. Fuel pressure was maintained at 15 MPa, and n-hexane was chosen as test fuel.