Abstract
Nitric oxide and smoke emissions in diesel engine can be controlled by optimising the air/fuel mixture. Early injection produces premixed charge resulted in simultaneous NOx and smoke emissions reduction. However, there could be an increase in hydrocarbons and CO emissions due to fuel impinged to the cylinder wall. The focus of the present work is to investigate the effects of a variation of pilot injection timing with EGR to NOx and smoke level on a modern V6 common rail direct injection. This study is carried out at two different engine load conditions of 30 Nm and 55 Nm, at constant engine speed of 2000 rpm. The results show that the early pilot injection timing contributed to the lower smoke level and higher NOx emissions. The higher level of NOx is due to higher combustion temperatures resulting from the complete combustion. Meanwhile, the lower smoke level is due to complete fuel combustion and soot oxidation. The early pilot injection timing produces an intermediate main ignition delay which also contributed to complete combustion. The formation of smoke is higher at a high engine load compared with low engine load due to the higher amount of fuel being injected.
Highlights
In direct injection diesel and compression ignition engines, the start of fuel injection (SOI) influences the fuel-air reaction rates and combustion behaviour (Cenk Sayin and Canakci 2009; Cenk Sayin, Murat Ilhan et al 2009)
The early pilot injection timing tends to produce intermediate main ignition delay resulting in a complete combustion process due to long residence time for the reaction of fuel-air
The early pilot injection timing produces the higher in-cylinder pressures leading to the higher temperatures and NOx emissions (Cenk Sayin and Canakci 2009; Cenk Sayin, Murat Ilhan et al 2009)
Summary
In direct injection diesel and compression ignition engines, the start of fuel injection (SOI) influences the fuel-air reaction rates and combustion behaviour (Cenk Sayin and Canakci 2009; Cenk Sayin, Murat Ilhan et al 2009). A. Vanegas et al used a 4-cylinder common-rail diesel engine to study the effect of multiple injection on emissions. Siddappa et al utilised a single cylinder direct injection engine to study the performance and emissions at different injection pressures and injection timing fuelled with diesel and biodiesel.
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