Effects of Ethanol, n-Butanol — n-Heptane Blended on Low Temperature Heat Release and HRR Phasing in Diesel-HCCI 2009-24-0094

The study of Diesel-HCCI combustion for blended alcohols in Diesel-like fuel was performed in this experimental work to quantify their impact on the net heat release rate. Ethanol and n-butanol were two representative alcohols and were blended with n-heptane; by varying mole percentage from 0, 18, 37 and 57 and varying dilutions with simulated Exhaust Gas Recirculation (EGR) from 0, 20 and 40 percent. The engine speed, intake temperature and equivalence ratio were set at 1500 rpm, 80 °C and 0.3 respectively. The impacts of alcohols were compared with the Primary Reference Fuels by blending n-heptane with iso-octane at the same molar percentage and were tested at same conditions. The results show that blended fuels and dilution with EGR can delay the combustion in different ways. Increasing the EGR rate retards combustion by increasing contained inert species. The energy output is also decreased with reducing of energy content but does not effect on the percentage of Low Temperature Heat Release (LTHR) combustion. Increasing of ethanol, n-butanol or iso-octane fractions reduce the percentage of LTHR combustion and increase the IMEP moderately. Moreover, the addition of both alcohols in n-heptane has more impact on delaying the heat release rate than that of iso-octane when the blended RON, MON and CN are considered. The time delay between the LTHR and the main combustion are dependant on EGR fraction and mean fuel ignitability as shown in relation to blended RON, MON and CN. Moreover, a possibility to increase engine output by changing fuel ignitability is realized in this study.