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Internal Combustion Engines

Reactivity Controlled Compression Ignition Using Premixed Hydrated Ethanol and Direct Injection Diesel

[+] Author and Article Information
Adam B. Dempsey1

1011 Engineering Research Building, 1500 Engineering Drive, Madison, WI 53711dempsab@gmail.com

Bishwadipa Das Adhikary, Sandeep Viswanathan, Rolf D. Reitz

 University of Wisconsin-Madison, Department of Mechanical Engineering, Engine Research Center, Madison, WI 53711

All the cycle work specific results shown in this section use the closed cycle calculated from IVC to EVO. However, gross cycle (−180 deg ATDC to 180 deg ATDC) results will be presented at the end for all loads investigated. Indicated means the cycle work was calculated from the cylinder pressure, neglecting engine friction. Mean Effective Pressure is equal to the cycle work divided by the engine displacement volume.

1

Corresponding author.

J. Eng. Gas Turbines Power 134(8), 082806 (Jun 21, 2012) (11 pages) doi:10.1115/1.4006703 History: Received November 03, 2011; Revised November 04, 2011; Published June 21, 2012; Online June 21, 2012

The present study uses numerical simulations to explore the use of hydrated (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 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, multi-dimensional engine modeling was performed using the KIVA code at engine loads from 5 to 17 bars 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 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.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Energy budget for the production of pure ethanol fuel from domestically grown corn [4]

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Figure 2

Energy requirements for ethanol distillation as a function of the percent by volume of ethanol-in-water [4]. Distillation energy is shown as a function of the lower heating value of ethanol, which is 26.9 MJ/kg.

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Figure 3

Experiments and simulation of RCCI combustion using conventional and alternative fuels

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Figure 4

GT-Power predictions of in-cylinder temperature at intake valve closure for port fuel injection of hydrated ethanol and gasoline

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Figure 5

In-cylinder gas temperature at intake valve closure as a function of the mass fraction of ethanol-in-water

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Figure 6

Gas phase conditions at intake valve closure as a function of the mass fraction of ethanol-in-water

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Figure 7

Single-zone HCCI simulation results for mixtures of hydrated ethanol and diesel fuel from 5 to 17 bars IMEP

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Figure 8

Single-zone HCCI simulation results for an ethanol-in-water sweep, 100% to 70%, at 9 bars IMEP with a constant IVC temperature

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Figure 9

Cylinder pressure and apparent heat release rate for percent ethanol-in-water sweep at 5 bars IMEP using KIVA

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Figure 10

Thermal efficiency, peak pressure rise rate (PPRR), combustion efficiency, and specific NOx emissions results at 5 bars IMEP over the closed cycle (IVC to EVO)

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Figure 11

Cylinder pressure and apparent heat release rate for percent ethanol-in-water sweep at 9 bars IMEP using KIVA

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Figure 12

Thermal efficiency, peak pressure rise rate (PPRR), combustion efficiency, and specific NOx emissions results at 9 bars IMEP over the closed cycle (IVC to EVO)

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Figure 13

Results for 60% ethanol-in-water at 9 bars IMEP using different injection strategies

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Figure 14

Cylinder pressure and apparent heat release rate for percent ethanol-in-water sweep at 13.5 bars IMEP using KIVA

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Figure 15

Thermal efficiency, peak pressure rise rate (PPRR), combustion efficiency, and specific NOx emissions results at 13.5 bars IMEP over the closed cycle (IVC to EVO)

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Figure 16

Cylinder pressure and apparent heat release rate for percent ethanol-in-water sweep at 17 bars IMEP using KIVA

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Figure 17

Thermal efficiency, peak pressure rise rate (PPRR), combustion efficiency, and specific NOx emissions results at 17 bars IMEP over the closed cycle (IVC to EVO)

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Figure 18

Fuel reactivity stratification and ignition sites for 9 bars IMEP that are established with premixed hydrated ethanol and direct injection of diesel fuel according to the injection parameters in Table 4 using 60% ethanol-in-water. The cut planes from which these contours are shown are coincident with the spray axis.

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Figure 19

Experimental shock tube studies of homogeneous autoignition of n-heptane [30] and ethanol [31] being utilized to illustrate the reactivity gradient that is established with these two fuels

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Figure 20

KIVA simulated load sweep using 70% by mass ethanol-in-water according to the operating conditions laid out in Table 5

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Figure 21

Gross indicated efficiency, peak pressure rise rate (PPRR), combustion efficiency, and specific NOx emissions over a load sweep using 70% by mass ethanol-in-water and operating conditions from Table 5

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Figure 22

Contours of fuel reactivity (i.e. octane #) on the spray axis for (a) 50% diesel and (b) 60% diesel in 1st injection at 5 bars IMEP. All other design parameters are those in Table 5.

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Figure 23

Contours of temperature on the spray axis for (a) 50% diesel and (b) 60% diesel in 1st injection. All other design parameters are those in Table 5.

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