Energy, exergy and sustainability analysis of split injection of diesel/n-butanol blends in a diesel engine

Exergy analysis envelopes the limitations of thermodynamic energy analysis by assessing the irreversibility of the system with sustainability and economic prospects, providing comprehensive cognizance. This study presents the energy-exergy analysis of split injected diesel/n-butanol blends under varying injection timings (IT) with 20% (B20), 25% (B25) and 30% (B30) (v/v) n-butanol share in diesel blends. This study attempts an unique endeavour to harness the potential of stratified injection of oxygenated fuel as it influences the engine emission-performance, deeming the energetic-exergetic analysis essential. The IT for the split operation varied at 35°−05°; 45°−15° and 50°−15° crank angle (CA) before the top dead centre (bTDC). B25 at an advanced IT of 50°−15° CA bTDC illustrated the optimal performance. Early IT attributes to advanced combustion phasing, contributing towards greater work derived in the expansion stroke and lower negative compression work, resulting in higher efficiency. This fuelling strategy also exhibited minimum brake-specific fuel consumption, energy-exergy loss, entropy generation and highest energy-exergy efficiency and sustainability. Incorporation of split injection enhances the energy-exergy efficiency by ∼16–18%; sustainability by ∼5% and reduces fuel use and entropy by ∼15% and 40%, respectively. Compared to diesel, operation n-butanol enrichment enhances brake thermal efficiency and lowers entropy.