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When switching from regular diesel fuel (sulfur free) to paraffinic hydrotreated vegetable oil (HVO), the changes in fuel chemistry and physical properties will affect emission characteristics in a very positive way. The effects also depend on the technology, after-treatment and sophistication of the engine. To determine the real effects in the case of city buses, 17 typical buses, representing emission classes from Euro II to EEV, were measured with HVO, regular diesel and several blended fuels. The average reduction was 10% for nitrogen oxides (NOx) and 30% for particulate matter (PM). Also some engine tests were performed to demonstrate the potential for additional performance benefits when fuel injection timing was optimized for HVO.

This paper aims to study numerically the influence of the number of fuel sprays in a single-cylinder diesel engine on mixing and combustion. The CFD simulations are carried out for a heavy-duty diesel engine with an 8 hole injector in the standard configuration. The fuel spray mass-flow rate was obtained from 1D-simulations and has been adjusted according to the number of nozzle holes to keep the total injected fuel mass constant. Two cases concerning the modified mass-flow rate are studied. In the first case the injection time was decreased whereas in the second case the nozzle hole diameter was decreased. In both cases the amount of nozzle holes (i.e. fuel sprays) was increased in several steps to 18 holes. Quantitative analyses were performed for the local air-fuel ratio, homogeneity of mixture distribution, heat release rate and the resulting in-cylinder pressure.