Study finds E20 offers higher peak load capacity and thermal efficiency than gasoline in RCCI combustion
Professor Rolf Reitz and Reed Hanson at the University of Wisconsin-Madison report on their investigations into reactivity-controlled compression ignition (RCCI) combustion in a light-duty, multi-cylinder, compression ignition engine over steady-state and transient operating conditions with both petroleum and bio-derived fuels in a paper in the International Journal of Engine Research. Among their findings was that E20 offers higher peak load capability and thermal efficiency than gasoline.
RCCI, a dual-fuel combustion technology developed by Dr. Rolf Reitz and colleagues, is a variant of Homogeneous Charge Compression Ignition (HCCI). RCCI provides more control over the combustion process and has been shown to have the potential to lower fuel use and emissions significantly. The RCCI process uses in-cylinder fuel blending with at least two fuels of different reactivity and multiple injections to control in-cylinder fuel reactivity to optimize combustion phasing, duration and magnitude.
The process involves introduction of a low reactivity fuel into the cylinder to create a well-mixed charge of low reactivity fuel, air and recirculated exhaust gases.
In the newly reported study, they examined in-cylinder fuel blending with port fuel injection of gasoline or E20 and early-cycle, direct injection of ultra-low sulfur diesel or B20.
The results under steady-state operation showed that E20 offered reduced hydrocarbon emissions from the lower port fuel injection mass fraction. B20 was found to require a higher port fuel injection mass fraction with resulting higher hydrocarbon emissions. Peak load and efficiency were not affected by the use of B20.
Steady-state NO and particulate matter emissions were unaffected by either of the biofuels. During the transient tests, E20 reduced hydrocarbon emissions while B20 increased hydrocarbon emissions. Both biofuels offered faster transient response to recover the CA50 to the steady-state CA50 value than gasoline or ultra-low sulfur diesel.
Reed M Hanson and Rolf D Reitz (2015) “Effects of biofuel blends on transient reactivity-controlled compression ignition engine combustion” International Journal of Engine Research doi: 10.1177/1468087415622340