Sooting Behavior of Commercial and Bio-Derived Butyl-Acetate/N-Heptane Blends in High-Pressure Spray Combustion Experiments

Abstract

Abstract The desire to use diesel blended with biofuels has accelerated in an effort to reduce reliance on non-renewable resources as well as reduce emissions from the heavy-duty portion of the transportation sector. Of particular interest are oxygenated compounds, notably esters, which have the potential to reduce the sooting tendency of diesel fuel. Butyl-acetate (BA) is one such ester with favorable properties as a fuel additive though perhaps not an obvious choice for a mixing controlled compression ignition engine due to its low cetane number. Despite this, if demonstrated to be able to reduced soot emissions when blended with diesel this blend candidate may be worth more study as a new bio-derived, low-energy, microbial fermentation process for production of BA shows promise for cost effective, high volume production. In this study, a constant-pressure flow chamber is utilized to observe fuel injection, mixing, ignition and combustion characteristics of commercial- and bio-BA blended with diesel surrogate n-heptane as a first study of its kind in a diesel-like fuel spray. Rainbow schlieren deflectometry, OH* chemiluminescence, and two-color pyrometry are utilized to quantify global parameters including ignition delay time, liquid length, vapor penetration, lift-off length, and soot mass. The results presented show that blending BA into n-heptane is effective at reducing soot emissions; moreover, the commercial-BA blend and the bio-BA blend are equally effective at reducing soot emissions. Future work will explore more test conditions, different blend ratios, and engine operation.