The present study uses numerical simulations to explore the use ofhydrated (wet) ethanol for reactivity controlled compression ignition (RCCI) operation in a heavy duty diesel engine. RCCI uses in-cylinder blending of a low reactivity fuel with a high reactivity fuel and has demonstrated significant fuel efficiency and emissions benefits using a variety of fuels, including gasoline and diesel. Combustion timing is controlled by the local blended fuel reactivity (i.e., octane number), and the combustion duration can be controlled by establishing optimized gradients in fuel reactivity in the combustion chamber. In the present study, the low reactivity fuel was hydrated ethanol while the higher reactivity fuel was diesel. First, the effect of water on ethanollwaterldiesel mixtures in completely premixed HCCI combustion was investigated using GT-Power and single-zone CHEMKIN simulations. The results showed that the main impact of the water in the ethanol is to reduce the initial in-cylinder temperature due to vaporization cooling. Next, multidimensional engine modeling was performed using the KIVA code at engine loads from 5 to 17 bars IMEP at 1300 rev/min with various grades ofhydrated ethanol and a fixed diesel fraction of the total fuel. The results show that hydrated ethanol can be used in RCCI combustion with gross indicated thermal efficiencies up to 55% and very low emissions. A 70/30 ethanol/water mixture (by mass) was found to yield the best results across the entire load range without the need for EGR.

Previous research has shown that a Homogeneous Charge Compression Ignition (HCCI) engine with efficient heat recovery can operate on a 35 to 65% volumetric mixture of ethanol-in-water while achieving high brake thermal efficiency (∼39%) and very low NOx emissions [4]. The major advantage of utilizing hydrated ethanol as a fuel is that the net energy gain improves from 21 to 55% of the heating value of ethanol and its co-products, since significant energy must be expended to remove water during production. This is required because wet ethanol is not suitable for conventional combustion engines. For example, spark ignition engines demand the use of pure ethanol because the dilution caused by water reduces the flame speed, resulting in misfire and problems due to condensation. The present study uses numerical simulations to explore the use of wet ethanol for Reactivity Controlled Compression Ignition (RCCI) operation in a heavy duty diesel engine. RCCI uses in-cylinder blending of a low reactivity fuel with a high reactivity fuel and has demonstrated significant fuel efficiency and emissions benefits using a variety of fuels, including gasoline and diesel. Combustion timing is controlled by the local blended fuel reactivity (i.e. octane number), and the combustion duration can be controlled by establishing optimized gradients in fuel reactivity in the combustion chamber. In the present study, the low reactivity fuel was hydrated ethanol while the higher reactivity fuel was diesel. First, the effect of water on ethanol/water/diesel HCCI was investigated using GT-Power and single-zone CHEMKIN simulations. The results showed that the main impact of the water in the ethanol is to reduce the IVC temperature due to vaporization cooling. Next, multidimensional engine modeling was performed using the KIVA code at engine loads from 5 to 17 bar IMEP at 1300 rev/min with various grades of hydrated ethanol and a fixed diesel fraction of the total fuel. The results show that hydrated ethanol can be used in a RCCI engine with gross indicated thermal efficiencies up to 55% and very low emissions. A 70/30 ethanol/water mixture (by mass) was found to yield the best results across the entire load range without the need for EGR.

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The exhaust filtration analysis system (EFA) developed at the University of Wisconsin – Madison was used to perform micro-scale filtration experiments on cordierite filter samples using particulate matter (PM) generated by a spark-ignition direct injection (SIDI) engine fueled with gasoline. A scanning mobility particle sizer (SMPS) was used to characterize running conditions with four distinct particle size distributions (PSDs). The distributions selected differed in the relative number of accumulation versus nucleation mode particles. The SMPS and an engine exhaust particle sizer (EEPS) were used to simultaneously measure the PSD downstream of the EFA and the real-time particulate emissions from the SIDI engine to determine the evolution of filtration efficiency during filter loading. Cordierite filter samples with properties representative of diesel particulate filters (DPFs) were loaded with PM from the different engine operating conditions. The results were compared to understand the impact of particle size distribution on filtration performance as well as the role of accumulation mode particles on the diffusion capture of PM. The most penetrating particle size (MPPS) was observed to decrease as a result of particle deposition within the filter substrate. In the absence of a soot cake, the penetration of particles smaller than 70 nm was seen to gradually increase with time, potentially due to increased velocities in the filter as flow area reduces during filter loading, or due to decreasing wall area for capture of particles by diffusion. Particle re-entrainment was not observed for any of the operating conditions.