Effects on NOx Emissions of Different Injection Timings in a Micro Cogeneration Unit Fuelled with Biodiesel

This study aims at investigating the effect of biodiesel on the performances and emissions of a diesel micro-CHP system, with a specific focus on NOx emissions, which are usually addressed as a critical feature for biodiesel-fuelled internal combustion engines (ICEs). Several fuels (pure substances and binary blends of diesel-biodiesel) have been tested in an ICE under different load conditions (from 1.0 kW to 3.8 kW) and injection timings (12.2, 17.2 and 20.8 degrees before-top-dead-centre). The CHP performances have been monitored in terms of electrical and thermal efficiencies; NOx emissions have been also measured. Results show: (i) a strong reduction in terms of NOx emissions when a late injection timing setting is used; (ii) a positive effect of biodiesel on electrical efficiency; (iii) a relevant potential recover of waste heat, with thermal efficiency values close to 40% for both petro-diesel and biodiesel.