Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Investigating Fuel Condensation Processes in Low Temperature Combustion Engines

[+] Author and Article Information
Lu Qiu

Engine Research Center,
University of Wisconsin-Madison,
1500 Engineering Drive,
Madison, WI 53706
e-mail: lqiu4@wisc.edu

Rolf D. Reitz

Wisconsin Distinguished Professor
Engine Research Center,
University of Wisconsin-Madison,
1500 Engineering Drive,
Madison, WI 53706
e-mail: reitz@engr.wisc.edu

1Corresponding author. Current address: Cummins Technical Center, 1900 McKinley Ave., Columbus, IN 47201, email: lu.qiu@cummins.com.

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received February 27, 2015; final manuscript received February 27, 2015; published online April 8, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(10), 101506 (Oct 01, 2015) (11 pages) Paper No: GTP-15-1059; doi: 10.1115/1.4030100 History: Received February 27, 2015; Revised February 27, 2015; Online April 08, 2015

Condensation of gaseous fuel is investigated in a low temperature combustion (LTC) engine fueled with double direct-injected diesel and premixed gasoline at two load conditions. Possible condensation is examined by considering real gas effects with the Peng–Robinson (PR) equation of state (EOS) and assuming thermodynamic equilibrium of the two fuels. The simulations show that three representative condensation events are observed. The first two condensations are found in the spray some time after the two direct injections (DI), when the evaporative cooling reduces the local temperature until phase separation occurs. The third condensation event occurs during the late stages of the expansion stroke, during which the continuous expansion sends the local fluid into the two-phase region again. Condensation was not found to greatly affect global parameters, such as the average cylinder pressure and temperature mainly because, before the main combustion event, the condensed phase was converted back to the vapor phase due to compression and/or first stage heat release. However, condensed fuel is shown to affect the emission predictions, including engine-out particulate matter (PM) and unburned hydrocarbons (UHCs). Specifically, it was shown that the condensed fuel comprised more than 95% of the PM in the low load condition, while its contribution was significantly reduced at the high load condition due to higher temperature and pressure conditions.

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Fig. 1

Phase diagram of binary nC16H34 and iC8H18 mixtures. Stars represent the critical points of the pure species. Phase regions are marked for a mixture with 30:70 (mole) composition. “V” stands for the vapor phase, “L” stands for the liquid phase, and “L + V” stands for the vapor–liquid two-phase region.

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Fig. 2

Comparison between experimental and CFD simulations of pressure and apparent heat release rate (AHRR)

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Fig. 3

Instantaneous total condensed mass and temperature fields for 9 bar IMEP load. Black spheres show the fuel droplets.

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Fig. 4

Instantaneous total condensed mass contours at the late expansion stroke for 9 bar IMEP load

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Fig. 5

Predicted condensed fuel in engine simulations

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Fig. 6

Effects of condensation on the evolution of the premixed gasoline ((a) and (b)) and direct-injected diesel ((c) and (d)) at two loads. (a) and (c) 5.2 bar IMEP. (b) and (d) 9.0 bar IMEP.

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Fig. 7

Effects of condensation on the cylinder average temperature and pressure. (a) 5.2 bar IMEP and (b) 9 bar IMEP.

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Fig. 8

Contour plots of condensed gasoline ((a) and (c)) and condensed diesel ((b) and (d)) during the compression stroke at 5.2 bar IMEP

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Fig. 9

Contour plots of condensed gasoline ((a) and (c)) and condensed diesel ((b) and (d)) during the compression stroke at 9.0 bar IMEP

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Fig. 10

Contour plots of condensed gasoline ((a) and (d)), condensed diesel ((b) and (e)), and elemental soot ((c) and (f)) during the expansion stroke at 5.2 bar IMEP

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Fig. 11

Comparison on predicted condensed fuel and soot with experimental soot




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