This paper investigates the effects of variable valve actuation on combustion in a Diesel engine. Early inlet valve closing (EIVC) lowered the pressure and temperature during the compression stroke, resulting in a longer ignition delay as the fuel mixed more homogenously with the charge air ahead of combustion. Combustion was characterized by prominent cool flame chemistry and a faster, more energetic, premixed combustion. Tests were performed on a 6.4L V8 engine at loads up to 5 bar BMEP. The use of EIVC showed significant reductions of soot (above 90%) and fuel efficiency improvements (of 5%) with NOx levels below the US 2010 standard of 0.2g/bhp-hr. The improvements in emissions and fuel economy came from controlling in-cylinder temperatures and optimizing combustion phasing. For a constant engine-out NOx emission, EIVC improved fuel economy as the amount of EGR and the engine back pressure requirement were reduced.
Effect of Variable Valve Timing on Diesel Combustion Characteristics
Sae Technical Papers
SAE 2010 World Congress & Exhibition ; 2010
2010-04-12
Conference paper
English
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