Performance and emission assessment of optimally blended biodiesel-diesel-ethanol in diesel engine generator

The composition of the base fuels (blend ratio) are strongly linked with fuel blend properties and has significant influence in determining engine performance and emission. Therefore, identification of optimal blend ratio for biodiesel-diesel-ethanol (BDE) blends is inevitable to achieve similar specification and performance as diesel. Many mathematical programming methods are available for refinery streamlining and most of them provide unrealistic solutions since much preference is given for economic constraints avoiding actual engine performance condition. This study estimated optimal composition for BDE blends by formulating a nonlinear optimization model to deliver maximum net heating value (LHV) while meeting multiple fuel property constraints. Applicable fuel mixing rules viz., Modified Lederer equation (kinematic viscosity), Grunberg-Nissan equation (Cetane Number), Kay's mixing rule (density, net heating value, sulfur content) are used for predicting DBE blend properties. The blend ratio optimization model is tested at base case (without limiting fuel concentration) and by incrementing ethanol content (5 to 10%) to study the corresponding deviations in diesel & biodiesel proportions. BDE blends meeting premium diesel fuel quality standards are further selected for experimental evaluation of the fuel properties. Engine performance and emission tests are conducted in a four stroke, four-cylinder 15 kW diesel engine generator at all load conditions under the constant speed of 1600 rpm. The study identified a blend of 78% diesel, 17% biodiesel, and 5% ethanol as the optimal ratio (BDEopt), meeting all key fuel property criteria along with the least deviation in net heating value over diesel (4.3%). The study demonstrated BDE blends at optimized ratios to have fuel properties as well as engine performance and emission characteristic identical with diesel.