Investigation of engine performance for alcohol/kerosene blends as in spark-ignition aviation piston engine

Abstract

Spark-ignition (SI) aviation piston engines are widely used on light helicopters and unmanned aerial vehicles (UAVs) because of the high-power density and ultra-high cost performance. Kerosene with high flash point is expected to improve safety of aforementioned aircrafts by replacing gasoline. However, in spark-ignition mode, kerosene is difficult to mix and is easy to knock. Short-chain alcohols have high volatility and octane number which can just make up for some defects of kerosene. In this paper, three kinds of alcohols including ethanol, n-propanol and n-butanol were blended with aviation kerosene (RP-3) by volume fraction of 30%, 50%, 70%, respectively. The combustion and emission characteristics of the blended fuels were deeply studied on a typical spark-ignition aviation piston engine. Meanwhile, engine performance fueled with commercial gasoline was also tested for comparison. Results indicated that alcohol/kerosene blends could reach higher brake thermal efficiency (BTE) (alcohol ratio ≥50%) compared to gasoline. Carbon monoxide (CO) and nitrogen oxides (NOx) emissions of blended fuels expressed dramatically descending. With the increase in alcohol ratio, the CO, hydrocarbons (HC) and soot emissions gradually decreased. The brake thermal efficiency showed an upward trend with the increase of alcohol ratios. The brake thermal efficiency of E70, P70 and B70 were increased by 2.15%, 3.52% and 6.51%, and the CO emissions of E70, P70 and B70 were reduced by 39.8%, 38.5% and 49.0%, respectively, compared to those of gasoline. Notably, n-butanol/kerosene blends exhibited the better combustion and emission characteristics, which had the higher efficiency and lower CO, HC and soot emissions.