Combustion Analysis of an Aviation Compression Ignition Engine Burning Pentanol-Kerosene Blends under Different Injection Timings

The resurgence of aviation heavy fuel engines (HFEs) and the single fuel concept policy make it important to investigate the application of kerosene in aviation compression ignition engines. From the experience of automotive engines, biofuels, in particular higher alcohols, may offer better combustion and emission characteristics for HFEs. In this study, the combustion performance was analyzed in a commercial aircraft compression ignition engine burning diesel as a baseline fuel and Chinese aviation kerosene fuel (RP-3) blended with pentanol (so-called second generation biofuel) with different blending ratios. The injection timing as the most critical operational parameter was swept from 17 to 23°CA BTDC (crank angle before top dead center) under constant engine speed (1600 rpm) and fixed injection pressure (60 MPa). The indicated thermal efficiency of kerosene-pentanol blend (K60P40) was higher than those of all other test fuels, and the advancement in injection timing caused an increase in combustion temperature which improved both the indicated thermal efficiency and combustion efficiency. The combustion duration was shorter for kerosene-pentanol blends (K60P40 and K80P20) than diesel; however, the combustion duration considerably increased with advancing injection timings for all the test fuels. Kerosene and its pentanol blends showed longer ignition delay compared to baseline diesel due to their lower cetane numbers. The indicated specific fuel consumption (ISFC) values of K80P20 and K60P40 were demonstrated to be lower than that of baseline diesel. This work demonstrated the great potential of kerosene-pentanol fuel blends in aircraft diesel engines without significant modifications.