Performance Evaluation of a Naturally Aspirated Diesel Engine With High n‐Pentanol–Diesel Blends Under Full‐Load Conditions

This study investigates the effects of n‐pentanol/diesel blends on the performance of a naturally aspirated, air‐cooled, single‐cylinder diesel engine under full load across 1400–2500 rpm. The engine was equipped with a mechanical direct injection system. Performance parameters were evaluated and compared for pure diesel (D100) and diesel blended with n‐pentanol at volume ratios of 10%, 30%, and 50% (designated as D90P10, D70P30, and D50P50, respectively). The results showed that brake torque and power increased with engine speed but plateaued above 2000 rpm due to intake and friction constraints. At low speeds (e.g., 1400 rpm), D50P50 showed a ~3.7% reduction in brake torque (11.58 vs. 12.02 Nm), ~14.9% lower brake thermal efficiency (BTE, 14.16% vs. 16.64%), and a ~17.5% increase in brake specific energy consumption (BSEC, 25.40 vs. 21.62 MJ/kWh) due to its lower energy density. In contrast, at high speeds (e.g., 2500 rpm), D50P50 exhibited improved BTE by ~1.3% (18.25% vs. 18.02%), with brake specific fuel consumption (BSFC) and BSEC gaps narrowed by oxygen‐assisted combustion. Exhaust gas temperature (EGT) was lower with higher n‐pentanol content at low speeds; however, it increased at high speeds due to n‐pentanol’s combustion characteristics and the cooling limitations of the air‐cooled engine. These findings fill a critical research gap by systematically evaluating high n‐pentanol/diesel blends under full‐load and variable‐speed conditions. The results provide novel insights for optimized engine control strategies, such as injection timing adjustments and intake enhancements.