TY - JOUR
TI - Chemiluminescence analysis of the effect of butanol-diesel fuel blends on the spray-combustion process in an experimental common rail diesel engine
AU - Merola Simona Silvia S
AU - Marchitto Luca
AU - Tornatore Cinzia
AU - Valentino Gerardo
JN - Thermal Science
PY - 2015
VL - 19
IS - 6
SP - 1943
EP - 1957
PT - Article
AB - Combustion process was studied from the injection until the late combustion  phase in an high swirl optically accessible combustion bowl connected to a  single cylinder 2-stroke high pressure common rail compression ignition  engine. Commercial diesel and blends of diesel and n-butanol (20%: BU20 and  40%: BU40) were used for the experiments. A pilot plus main injection  strategy was investigated fixing the injection pressure and fuel mass  injected per stroke. Two main injection timings and different pilot-main  dwell times were explored achieving for any strategy a mixing controlled  combustion. Advancing the main injection start, an increase in net engine  working cycle (>40%) together with a strong smoke number decrease (>80%) and  NOx concentration increase (@50%) were measured for all pilot injection  timings. Compared to diesel fuel, butanol induced a decrease in soot emission  and an increase in net engine working area when butanol ratio increased in  the blend. A noticeable increase in NOx was detected at the exhaust for BU40  with a slight effect of the dwell-time. Spectroscopic investigations  confirmed the delayed auto-ignition (~60 ms) of the pilot injection for BU40  compared to diesel. The spectral features for the different fuels were  comparable at the start of combustion process, but they evolved in different  ways. Broadband signal caused by soot emission, was lower for BU40 than  diesel. Different balance of the bands at 309 and 282 nm, due to different OH  transitions, were detected between the two fuels. The ratio of these  intensities was used to follow flame temperature evolution.