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Internal combustion engine research on alternative fuels has gained momentum because of growing awareness about energy security and environmental issues worldwide. Biodiesel offers an ideal solution to these problems and is an excellent partial replacement to mineral diesel. In this study, Karanja biodiesel blended with mineral diesel has been investigated for macroscopic spray characterization vis-à-vis baseline mineral diesel by varying fuel injection pressures (50, 100 and 150 MPa). Spray developed with relatively narrower spray angle for KB20. Injector needle movement for energizing and real injection durations were also compared for diesel and KB20 at fuel injection pressures of 50, 100 and 150 MPa. Needle movement was slightly higher for KB20 because of its relatively higher viscosity. However, with increasing fuel injection pressure, the difference reduced and showed quite similar results. A 2.2 L common rail direct injection sport utility vehicle EURO-IV diesel engine was used for the experiments. Engine performance, emissions and combustion characteristics of KB20 were compared with baseline mineral diesel at (1) the rated engine speed (2500 r/min) with varying engine loads as well as (2) at the rated load at varying engine speeds (1500-3500 r/min). Brake thermal efficiency of KB20 was lower than mineral diesel. Brake-specific carbon monoxide and carbon dioxide emissions decreased with increasing brake mean effective pressure and showed increasing trend with increasing engine speeds. KB20 showed emission of higher number of particles compared to mineral diesel at all engine operating conditions. Higher oxygen content of biodiesel resulted in shorter ignition delay and slightly higher peak cylinder pressure. KB20 showed relatively longer combustion duration compared to mineral diesel at 2500 r/min engine speed.

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