• Energy Research

Abstract The practice of the green renewable fuels in diesel engines is increasing concerning the progressive deterioration of the green environment and the scarcity of the fossil fuels. In these aspects, several experiments in dual fuel mode (DFM) at different global fuel–air equivalence ratio (Φglobal), intake charge preheating and loads have been carried out considering biogas as the inducted renewable fuel. The Φglobal was varied from 0.30 to 0.89 from part to higher loads with biogas flow rate (BFR) of 0.67–3.99 kg/h. The maximum diesel replacements (DR) and biogas energy share (BES) are found to be 92.49% and 97.55%, respectively. However, at higher Φglobal, the brake thermal efficiency (BTE) reduces drastically. Although with preheating, there is an increment of BTE by 5.72% and 2.60% at loads of 4.36 N·m and 21.78 N·m, respectively. At lower Φglobal in DFM and with preheating, the diesel like trends of BTE is achieved. Overall combustion behaviour deteriorates at higher Φglobal. However, it significantly improved with the preheating and at controlled Φglobal. Higher cycle-to-cycle variation of cylinder peak pressure (CPP) is noticed at higher Φglobal. With preheating, at part and higher loads the reduction of CO of 29.41% and 65.49% are estimated. At higher load (21.78 N·m) and with preheating a reduction of 53.33% of HC is noticed. The drastic reduction of NOx is observed with the increment of Φglobal. The superior performance is achieved at each of the tested loads at the optimum Φglobal and with preheating.

Dual fuel diesel (DFD) engines have been gaining popularity due to the flexibility of using both bio and fossil liquid and gaseous fuels. Further, the efficient combustion in DFD mode with bio liquid and gaseous fuel can greatly reduce the greenhouse gas emissions as well as the dependency on fossil diesel. In recent times, a host of investigation has been done in normal dual fuel diesel (nDFD) mode with pure diesel and biogas. However, the engines with ethanol blended with diesel and intake charge (biogas–air mixture) with preheating have not been studied. In the present study, 5% ethanol blended with diesel (E5) and biogas with preheating are used in dual fuel engine (DFD-E5) to find their performance and emission characteristics. In order to have a direct comparison of performances, an engine with pure diesel (E0) and biogas with preheating is also tested in dual fuel mode (DFD-E0). In all the cases, the effect of total equivalence ratio on engine overall performance has also been investigated. In DFD-E5 mode, and at the maximum torque of 21.78 N·m, the brake thermal efficiency (BTE) increases by 2.98% as compared to nDFD mode. At the same torque, there is no trace of carbon monoxide (CO), whereas there is a reduction of hydrocarbon (HC) emission by 62.22% with respect to pure diesel (PD) mode. The nitrogen of oxides (NOx) is found to decrease in DFD modes in contrast to PD mode.