Abstract:

The effects of ultramultihole injection on spray, combustion, and emission characteristics were
investigated for late injection conditions to realize high-efficiency, low-emission combustion in a high-pressure
common-rail diesel-engine by ultramultihole injection. A 3-D simulation model was set up for a six-cylinder highpressure
common-rail diesel engine using a KIVA-3V code, and was then experimentally validated. The results
show that the interference between the upper-layer jets and the lower-layer jets of the ultramultihole nozzle makes the spray shape more fleecy compared with the traditional injector, in favor of the spray atomization and
vaporization. The in-cylinder mixture by ultramultihole nozzles distributes more evenly than the mixture using
traditional injectors, and the combustion process is mainly premixed combustion. The peak heat release rate
increases by 60%, the NOx emission increases by 36%, the soot emission formation region decreases clearly,
and the soot emission maximum decreases by 48%. The emission decreases 64% for NOx with 46% for soot,
without the power penalty by using the ultramultihole nozzle and exhaust gas recirculation (EGR) technique,
the postponing injection, and the increasing injection pressure. Therefore, high-efficiency clean premixed
combustion can be realized in a high-pressure common-rail diesel-engine with ultramultihole technology.

Key words: diesel engine, high-pressure common-rail, ultramultihole nozzle, late injection, NOx emission, soot emission