Effects of pilot fuel injection timing on the performance and emission characteristics of a diesel engine fuelled with biogas

Early investigation by the authors on the use of raw biogas (BG) in a diesel engine revealed that, biogas at a flow rate of 0.9 kg/h gave better performance and lower emissions than other flow rates. In this investigation, an optimum injection timing of the pilot fuel was determined in the dual fuel mode (DFM). In the DFM, the injection timing of the engine was advanced to maximum of 4.5 degrees CA in steps of 1.5 degrees CA from the original injection timing of 23 degrees CA bTDC. The results indicated that by advancing the injection timing to 26 degrees CA in the DFM26.0, the engine exhibited better performance and lower emissions than those of diesel operation. The brake specific fuel consumption (BSFC), brake specific carbon monoxide (BSCO) and brake specific hydrocarbon (BSHC) emissions of DFM26.0 were found to be higher by about 25%, 2% and 10% respectively, than those of diesel at full load, while the smoke emission was lower by about 39% than that of diesel. The trend of energy share indicated that a maximum replacement of 42.9% of energy from biogas was possible in the DFM, at full load.