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Brakora, Jessica L.
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Combustion Model for Biodiesel-Fueled Engine Simulations using Realistic Chemistry and Physical Properties

SAE International Journal of Engines

Univ. of Wisconsin-Youngchul Ra, Rolf D. Reitz
Univ. of Wisconsin Madison-Jessica L. Brakora
  • Journal Article
  • 2011-01-0831
Published 2011-04-12 by SAE International in United States
Biodiesel-fueled engine simulations were performed using the KIVA3v-Release 2 code coupled with Chemkin-II for detailed chemistry. The model incorporates a reduced mechanism that was created from a methyl decanoate/methyl-9-decenoate mechanism developed at the Lawrence Livermore National Laboratory. A combination of Directed Relation Graph, chemical lumping, and limited reaction rate tuning was used to reduce the detailed mechanism from 3299 species and 10806 reactions to 77 species and 209 reactions. The mechanism was validated against its detailed counterpart and predicted accurate ignition delay times over a range of relevant operating conditions. The mechanism was then combined with the ERC PRF mechanism to include n-heptane as an additional fuel component.The biodiesel mechanism was applied in KIVA using a discrete multi-component model with accurate physical properties for the five common components of real biodiesel fuel. A mixture of methyl decanoate and methyl-9-decenoate was used as the biodiesel surrogate to account for both the saturated and unsaturated components found in real biodiesel fuels. Non-reacting biodiesel spray experiments were reproduced using the KIVA model, and the KH-RT spray model constants…
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Investigation of NOx Predictions from Biodiesel-fueled HCCI Engine Simulations Using a Reduced Kinetic Mechanism

Univ. of Wisconsin - Madison-Jessica L. Brakora, Rolf D. Reitz
Published 2010-04-12 by SAE International in United States
A numerical study was performed to compare the formation of nitric oxide (NO) and nitrogen dioxide (NO₂), collectively termed NOx, resulting from biodiesel and diesel combustion in an internal combustion engine. It has been shown that biodiesel tends to increase NOx compared to diesel, and to-date, there is no widely accepted explanation. Many factors can lead to increased NOx formation and it was of interest to determine if fuel chemistry plays a significant role. Therefore, in order to isolate the fuel chemistry from mixing processes typical in a compression ignition engine, sprays were not considered in the present investigation.The current study compares the NOx formation of surrogates for biodiesel (as represented by methyl butanoate and n-heptane) and diesel (n-heptane) under completely homogeneous conditions. Combustion of each fuel was simulated using the Senkin code for both an adiabatic, constant volume reactor, and an adiabatic, single-zone HCCI engine model. The fuel chemistry is represented using an updated version of a mechanism that combines reduced mechanisms for methyl butanoate and n-heptane. NOx chemistry is predicted using a 19-step…
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Development and Validation of a Reduced Reaction Mechanism for Biodiesel-Fueled Engine Simulations

SAE International Journal of Fuels and Lubricants

Oak Ridge National Laboratory-Joanna McFarlane, C. Stuart Daw
University of Wisconsin, Madison-Jessica L. Brakora, Youngchul Ra, Rolf D. Reitz
  • Journal Article
  • 2008-01-1378
Published 2008-04-14 by SAE International in United States
In the present study a reduced chemical reaction mechanism for biodiesel surrogate fuel was developed and validated for multi-dimensional engine combustion simulations. An existing detailed methyl butanoate mechanism that contained 264 species and 1219 reactions was chosen to represent the oxygenated portion of the fuel. The reduction process included flux analysis, ignition sensitivity analysis, and optimization of reaction rate constants under constant volume conditions. The current reduced mechanism consists of 41 species and 150 reactions and gives predictions in excellent agreement with those of the comprehensive mechanism.In order to validate the mechanism under biodiesel-fueled engine conditions, it was combined with another skeletal mechanism for n-heptane oxidation. This combined reaction mechanism can be used to adjust the energy content of the fuel, and account for diesel/biodiesel blend engine simulations. The combined mechanism, ERC-bio, contains 53 species and 156 reactions. Biodiesel-fueled engine operation was successfully simulated using the ERC-bio mechanism.
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