Effect of C₄ alcohol and ester as fuel additives on diesel engine operating characteristics

Due to their numerous advantages, diesel engines remain the primary energy source for heavy machinery. In the present experimental study, the effect of oxyfuel type, oxygen content and blend volume on diesel engine performance, combustion and emission characteristics has been investigated. Experiments were carried out on seven fuel blends using a 4-stroke, single cylinder, direct injection combustion ignition (CI) engine at a constant speed of 2000 rpm and varying loads. Four-carbon alcohol (n-butanol) and ester (ethyl ethanoate) were separately blended with pure diesel (D100) at three blending ratios. For each fuel type, two blends were prepared to contain an approximate oxygen mass content of 2.2 % and 4.1 %, then a third blend containing 15 % additive volume ratio was also formulated. All tested blends had minimal effect on in-cylinder pressure and heat release rate (HRR). At low loads, up to 20.9 % rise in brake specific fuel consumption (BSFC) was recorded but EE15 (15 % ethyl ethanoate, 85 % diesel) achieved 15.35 % lower BSFC at 60 % load. NOx emissions reduced for all blends, with n-butanol blends achieving 30.6 % less NOx emissions compared to D100. However, CO emissions increased by up to 37.6 % for n-butanol and 32.9 % for ethyl ethanoate. Considering engine stability, all blends were found to have a stable engine operation. Between the oxyfuel types, EE10.65 (10.65 ethyl ethanoate, 89.35 % diesel) has slightly superior emissions characteristics at equal fuel mass flow rate. Both fuel additives are suitable for CI engine at low blending ratios.