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Research Papers: Internal Combustion Engines

Effects of the Re-Entrant Bowl Geometry on a DI Turbocharged Diesel Engine Performance and Emissions—A CFD Approach

[+] Author and Article Information
S. Pasupathy Venkateswaran

Department of Mechanical Engineering, Anna University Chennai, Chennai, Tamilnadu 600 025, Indiavenkateswaran.ps@gmail.com

G. Nagarajan

Department of Mechanical Engineering, Anna University Chennai, Chennai, Tamilnadu 600 025, Indianagarajan1963@annauniv.edu

J. Eng. Gas Turbines Power 132(12), 122803 (Aug 30, 2010) (10 pages) doi:10.1115/1.4001294 History: Received June 11, 2009; Revised February 10, 2010; Published August 30, 2010; Online August 30, 2010

The purpose of this study is to investigate the influence of re-entrant bowl geometry on both engine performance and combustion efficiency in a direct injection (DI), turbocharged diesel engine for heavy-duty applications. The piston bowl design is one of the most important factors that affect the air–fuel mixing and the subsequent combustion and pollutant formation processes in a DI diesel engine. The bowl geometry and dimensions, such as the pip region, bowl lip area, and toroidal radius, are all known to have an effect on the in-cylinder mixing and combustion processes. Based on the idea of enhancing diffusion combustion at the later stage of the combustion period, three different bowl geometries, namely, bowl 1 (baseline), bowl 2, and bowl 3 were selected and investigated. All the other relevant parameters, namely, compression ratio, maximum diameter of the bowl, squish clearance and injection rate were kept constant. A commercial CFD code STAR-CD was used to model the in-cylinder flows and combustion process, and experimental results of the baseline bowl were used to validate the numerical model. The simulation results show that, bowl 3 enhance the turbulence and hence results in better air-fuel mixing among all three bowls in a DI diesel engine. As a result, the indicated specific fuel consumption and soot emission reduced although the NOx emission is increased owing to better mixing and a faster combustion process. Globally, since the reduction in soot is larger (46% as regards baseline) than the increase in NOx (+15% as regards baseline), it can be concluded that bowl 3 is the best trade-off between performance and emissions.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Injection velocity profile

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Figure 2

Computational grid for baseline bowl

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Figure 3

Geometry of re-entrant bowls

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Figure 4

Main geometrical parameters

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Figure 5

In-cylinder pressure at 2400 rpm, full load

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Figure 6

No emission at 2400 rpm, full load

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Figure 7

Pressure traces for the three bowls at 2400 rpm, full load

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Figure 8

Temperature, NOx, and soot traces for the three bowls at 2400 rpm, full load

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Figure 9

Comparison of equivalence ratio and in-cylinder temperature distribution in the three bowls at 2400 rpm and CA=20 deg aTDC

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Figure 10

Comparison of soot and NOx distribution in the three bowls at 2400 rpm and CA=20 deg aTDC

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Figure 11

Comparison of equivalence ratio and in-cylinder temperature distribution in the three bowls at 2400 rpm and CA=25 deg aTDC

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Figure 12

Comparison of soot and NOx distribution in the three bowls at 2400 rpm and CA=25 deg aTDC

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Figure 13

TKE distribution in the three bowls at TDC and 10 deg CA aTDC

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Figure 14

TKE distribution in the three bowls at 20 deg CA aTDC and 30 deg CA aTDC

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Figure 15

Intensity of swirl versus crank angle

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Figure 16

TKE versus crank angle

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Figure 17

Bowl shape influence on ISFC and gross-IMEP

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Figure 18

Bowl shape influence on NOx and soot at EVO

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