Exergy, exergoeconomic, environmental damage cost, and performance-emissions trade-off analysis of two-stroke UAV engine operating with phytol and benzene fuel additives

Two-stroke Unmanned Aerial Vehicle (UAV) engines offer high power-to-weight ratios but present challenges in fuel efficiency and environmental impact. This study comparatively investigates the effects of phytol, a bio-based oxygenated diterpene alcohol, and benzene, an aromatic hydrocarbon, on the performance, exergy, exer goeconomic characteristics, and exhaust emissions of a two-stroke UAV engine. Experiments were conducted at five engine speeds (3250–6250 rpm) using gasoline blended with 10% and 20% phytol (P10, P20) or benzene (B10, B20) by volume. The experimental results were evaluated through an integrated assessment combining exergy analysis, Specific Exergy Costing (SPECO), and calculations of environmental impact and damage costs based on measured gaseous pollutants. Compared with reference gasoline, P20 increased exergy destruction by an average of 8.4% and decreased exergy efficiency by 6.8%, whereas B20 increased exergy destruction by 3.6% and reduced exergy efficiency by 3.0%. Despite these thermodynamic results, P10 reduced the calculated total environmental impact by an average of 1.2%, while B20 increased it by 3.3%. The calculated environmental damage costs decreased for all investigated additive blends within the adopted pollutant valuation framework. However, the high commercial purchase price of phytol adversely affected its exergoeconomic performance. These findings highlight important trade-offs between thermodynamic efficiency, fuel-related economic costs, and exhaust emission-related environmental indicators. The results provide a comparative experimental basis for further investigation of alternative fuel additives in lightweight UAV engines.