Optimization of diesel engine performance and emissions with biodiesel-diesel blends and EGR using response surface methodology (RSM)

Abstract

The rising price of conventional liquid fuels and increasing pollution drive research into alternate bio-fuels. In the present study, waste cooking soybean oil (WSCO) was collected from local restaurants and food processing industries. The 92% biodiesel yield was obtained by using a homogeneous transesterification process. A detailed experimental and analytical study of the engine performance and emissions with binary fuel blends of WSCO biodiesel and ultra-low sulfur diesel (ULSD) has been performed using response surface methodology. Binary blends were prepared by adding 20–35 v.% of WSCO to ULSD; experiments were carried out at 0–15% EGR. To analyze the effects of input variables on BSFC, BTE, smoke, NOx, CO, and HC, regression models were developed and confirmed to be statistically significant. The binary blend of B35 with 15% EGR (B35EGR15) showed the maximum desirability (0.928). The model's adequacy was validated by a confirmation test with an error in prediction below 6%. For blend B35EGR15, BSFC was increased by 6.61% and BTE was reduced by 5.30% for B35EGR15 as compared to ULSDEGR0 (ULSD at 0% EGR). Smoke and NOx emissions were decreased by 19.09% and 59.04%, while CO and HC emissions were increased by 17.54% and 11.76%, as compared to ULSDEGR0. The economic analysis showed that the operation cost was reduced by 23.34% for B35EGR15 as compared to ULSDEGR0. The B35EGR15 blend can be used in existing diesel engines with no engine modifications.