Dual-injection strategies in spark-ignition (SI) engines allow the in-cylinder blending of two different fuels at any blend ratio, when simultaneously combining port fuel injection (PFI) and direct-injection (DI). This offers increased flexibility and the potential to optimize the combustion process depending on the engine requirement and fuel availability. Until now, little or no research evidence exists on the experimental comparison of dual-injection to DI in the combustion of gasoline-biofuel blends. Therefore, in this work the authors evaluate this comparison using a new biofuel candidate: 2,5-dimethylfuran (DMF). The differences in performance are examined using D25 (25% DMF in gasoline, by volume) in a single cylinder SI research engine operating at 1500. rpm and varying load (3.5-8.5. bar IMEP). All tests were carried out at stoichiometry (λ= 1) using the cross-over theory of the carbon monoxide and oxygen emissions concentrations. The current results are promising for dual-injection. The improved mixture preparation compared to DI results in lower combustion durations and higher in-cylinder pressures. This gives rise to higher indicated thermal efficiencies and lower fuel consumption rates compared to the same blend (D25) in DI (up to 4% and 3.2%, respectively). More significantly, the lower fuel consumption rate with dual-injection (on a volumetric basis), is up to 1.2% lower than with gasoline in homogenous DI (GDI) up to 8. bar IMEP, despite the use of a lower energy density biofuel. © 2012 Elsevier Ltd.
- Cross-over theory