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During the recent years, extensive research conducted worldwide in the field of Heavy Duty Diesel engines has resulted to a significant improvement of engine performance and emissions. These efforts have been assisted from simulation models providing good results. Towards this direction a multi-zone model developed by the authors has been used in the past to examine the effect of injection pressure on DI diesel engine performance and emissions. The attempt was challenging since no experimental data existed when the calculations were conducted, to support the findings. Eventually, experimental data concerning engine performance and emissions became available using slightly different operating conditions and injection pressure data. In the present study an attempt is made to evaluate the prediction ability of the multi zone model by comparing the theoretical results with experimental data and explain any discrepancies between them.

A major challenge in the development of future heavy-duty diesel engines is the reduction of NOx and particulate emissions with minimum penalties in fuel consumption. The further decrease of emission limits (i.e., EPA 2007-2010, Euro 5 and Japan 05) requires new, advanced approaches. The injection system of DI diesel engines has an important role regarding the fulfillment of demands for low pollutant emissions and high engine efficiency. One of the injection system parameters affecting fuel spray characteristics, fuel-air mixing and consequently, combustion and pollutant formation is the geometry of the nozzle hole. A detailed experimental investigation was conducted at UPV-CMT using three different nozzle hole types: a standard, a convergent and a divergent one to discern the effect of nozzle hole conical shape on engine performance and emissions.

The diesel engine is currently the most efficient powertrain for vehicle propulsion. Unfortunately it suffers from rather high particulate and NOx emissions that are directly related to its combustion mechanism. Future emission legislation requires drastic reduction of NOx and particulate matter compared to present values. Engine manufacturers in their effort to meet these limits propose two solutions: reduction of pollutants inside the combustion chamber using internal measures and reduction at the tailpipe using aftertreatment technology. Currently there are various opinions considering the final solution. Taking into account information related to aftertreatment technology, an effort should be made to reduce pollutants inside the combustion chamber as much as possible. The last is obvious if we account for the even more strict emission limits to be applied after 2010 that will require a combination of aftertreatment and internal measures.