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

# Computational Analysis of Combustion of High and Low Cetane Fuels in a Compression Ignition Engine

[+] Author and Article Information
Chaitanya Kavuri

Carnegie Mellon University,
Pittsburgh, PA 15213

Satbir Singh

Carnegie Mellon University,
Pittsburgh, PA 15213
e-mail: satbirs@andrew.cmu.edu

Sundar Rajan Krishnan, Kalyan Kumar Srinivasan

Mississippi State University,
Mississippi State, MS 39762

Stephen Ciatti

Argonne National Laboratory,
Argonne, IL 60439

1Corresponding author.

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received April 28, 2014; final manuscript received May 28, 2014; published online July 15, 2014. Editor: David Wisler. The United States Government retains, and by accepting the article for publication, the publisher acknowledges that the United States Government retains, a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for United States government purposes.

J. Eng. Gas Turbines Power 136(12), 121506 (Jul 15, 2014) (10 pages) Paper No: GTP-14-1214; doi: 10.1115/1.4027927 History: Received April 28, 2014; Revised May 28, 2014

## Abstract

Past research has shown that the combustion of low cetane fuels in compression ignition (CI) engines results in higher fuel conversion efficiencies. However, when high-cetane fuels such as diesel are substituted with low-cetane fuels such as gasoline, the engine operation tends to suffer from high carbon monoxide (CO) emissions at low loads and combustion noise at high loads. In this paper, we present a computational analysis of a light-duty CI engine operating on diesel, kerosene and gasoline. These three fuels cover a range of cetane numbers (CNs) from 46 for diesel to 25 for gasoline. Similar to experiments, the model predicted higher CO emissions at low load operation with gasoline. Predictions of in-cylinder details were utilized to understand differences in combustion characteristics of the three fuels. The in-cylinder mass contours and the evolution of model predicted in-cylinder mixture in Φ–T coordinates were then used to explain the emission trends. From the analysis, overmixing due to early single injection was identified as the reason for high CO emissions with low load gasoline low temperature combustion (LTC). Additional simulations were performed by introducing techniques like cetane enhancement, adding hot exhaust gas recirculation (EGR), and variation of the injection scheme. Their effects on low load gasoline LTC were studied. Finally, it is shown that use of a dual pulse injection scheme with hot EGR helped to reduce the CO emissions for low load gasoline LTC while maintaining low NOx emissions.

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## Figures

Fig. 5

HRR profiles of the three fuels at 12 bar BMEP

Fig. 4

HRR profiles of the three fuels at 5 bar BMEP

Fig. 3

HRR profiles of the three fuels at 2 bar BMEP

Fig. 9

Φ-T plot comparison at 2 bar BMEP

Fig. 2

Mesh on a cut plane through the spray

Fig. 1

Engine out NOx and CO emissions versus BMEP for gasoline [4]

Fig. 6

Model predicted NOx emissions comparison

Fig. 7

Model predicted CO emissions comparison

Fig. 8

Model predicted HC emissions comparison

Fig. 10

Φ-T plot comparison at 5 bar BMEP

Fig. 11

Φ-T plot comparison at 12 bar BMEP

Fig. 12

Temperature-residence time comparison at 2 bar BMEP

Fig. 13

T-residence time comparison at 5 bar BMEP

Fig. 14

T-residence time comparison at 12 bar BMEP

Fig. 15

In-cylinder CO mass, equivalence ratio and temperature contours

Fig. 17

NOx comparison with cetane enhancement

Fig. 18

CO comparison with cetane enhancement

Fig. 19

HC comparison with cetane enhancement

Fig. 20

Emissions comparison with EGR

Fig. 21

HRR comparison of single pulse and dual pulse injection schemes with varying EGR

Fig. 22

Emission comparison of single pulse and dual pulse injection schemes with varying EGR

Fig. 16

In-cylinder CO mass in Φ-T co-ordinates at SOC, peak HRR, late in expansion stroke, and EVO

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