LAUSR

Abstract Increased menacing engine emissions and threat to human health from metallic combustion catalysts demand a shift towards the application of non-metallic fuel additives. Therefore, the current study is an effort, conducted to introduce a new, less toxic and non-metallic graphite (G) nano diesel-fuel additive, by investigating its effects on the performance and regulated gaseous emissions of a four-cylinder, water-cooled, compression ignition (CI) engine. The experiments were also repeated with Iron oxide (Fe2O3) nanoparticles and statistical analyses were implemented to have a comparison with graphite nanoparticles. The G and Fe2O3 nanoparticles, in concentrations of 50, 100 and 150 mg per litre (mg/l), were mixed with neat diesel by magnetic stirring to prepare homogeneous fuel blends. The physicochemical properties of the fuel blends were determined. A maximum decrease of 4.9% in viscosity and an increase of 3.26% in Cetane index was observed for graphite blends. The investigated parameters include torque (T), brake power (BP), brake specific fuel consumption (bsfc), brake thermal efficiency (BTE), carbon monoxide (CO) and nitrogen oxides (NOx) emissions at engine speed varying from 1500 to 3000 rpm with an interval of 300 rpm at full load. The results revealed that at a confidence level of 95% (significance level α = 0.05), G-blends indicated a higher increase in torque, power, BTE and a greater decrease in bsfc than Fe2O3 blends. Graphite blends produced significantly lower NOx emissions than Fe2O3 treated blends. The increase in T, BP and BTE was 2.4%, 8.9% and 3.9% respectively, with 150 mg/l Fe2O3 blends and 2.9%, 9.6% and 4.1% respectively, with 150 mg/l G-blends. Graphite blends resulted in a 2.6% reduction in bsfc. The increase in NOx emissions was 34.7% with Fe2O3 and 29.2% with G at concentrations of 150 mg/l. The CO increased by 14.2% with G blends. A negative statistical correlation was observed for CO emissions between G and Fe2O3 blends. We conclude that G nanoparticles are more environmentally friendly fuel additives than Fe2O3; however, their application is more recommended for large turbocharged CI engines with improved oxygen density in inlet compressed air.