Optimization of diesel injection timing, producer gas flow rate, and engine load for a diesel engine operated on dual fuel mode at a high engine speed

Abstract

Jatropha seed cake is a byproduct of biodiesel production, and the seed cake can be used as a feedstock for a gasifier. The gasified seed cake can partially reduce fossil diesel consumption to run a diesel engine. However, an increase in gas flow rate is associated with a higher diesel substitution rate, but a higher specific CO₂ emission is observed. This study attempts to optimize diesel injection timing (DIT), gaseous fuel flow rate, and engine load to offset the specific diesel consumption and the specific CO₂ emissions at a high engine speed of 3,000 rpm. Response Surface Methodology (RSM) was applied to statistically develop mathematical models of the response variables as functions of the design variables. A desirability function was then applied to maximize overall desirability. It highlighted that an overall desirability of 0.829 was obtained at 11 before top dead center (BTDC) of the DIT, a 10 kg/h gas flow rate, and 70% of the full engine load. At the optimum operating settings, the specific diesel consumption (SDC) and the specific CO₂ emission were 0.0967 kg/kWh and 0.6123 kg/kWh, respectively. A value of electrical-thermal efficiency was found to be 14.10%. It is evident from these findings that a dual producer gas-diesel fuel engine should not be operated at the maximum diesel replacement rate.