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Research Papers: Internal Combustion Engines

Reduction of Numerical Parameter Dependencies in Diesel Spray Models

[+] Author and Article Information
Neerav Abani, Achuth Munnannur, Rolf D. Reitz

Engine Research Center, University of Wisconsin-Madison, Madison, WI 53706

J. Eng. Gas Turbines Power 130(3), 032809 (Apr 02, 2008) (9 pages) doi:10.1115/1.2830867 History: Received October 30, 2007; Revised October 31, 2007; Published April 02, 2008

Numerical grid and time-step dependencies of discrete droplet Lagrangian spray models are identified. The two main sources of grid dependency are due to errors in predicting the droplet-gas relative velocity and errors in describing droplet-droplet collision and coalescence processes. For reducing grid dependency due to the relative velocity effects, a gas-jet theory is proposed and applied to model diesel sprays. For the time-step dependency, it is identified that the collision submodel results in drop size variation in the standard spray model. A proposed spray model based on the gas-jet theory is found to improve the time-step independency also along with the mesh independency. The use of both Eulerian (collision mesh) and Lagrangian (radius of influence) collision models along with the gas-jet theory is found to provide mesh-independent results.

Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 4

Standard KIVA: overall SMD. ρamb=60.6kg∕m3.

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Figure 5

Standard KIVA: total number of parcels. ρamb=60.6kg∕m3.

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Figure 6

Coarse mesh illustration

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Figure 7

Collision mesh sensitivity with improved spray model. CFD mesh size of 4×4mm2 and ρamb=60.6kg∕m3.

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Figure 8

Total number of coalescences in the domain with increase in collision mesh size

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Figure 9

Standard KIVA with collision mesh: spray-tip penetration. Experimental data from Ref. 18, ρamb=60.6kg∕m3.

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Figure 10

Standard KIVA with collision mesh: overall SMD. ρamb=60.6kg∕m3.

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Figure 11

Standard KIVA+collision mesh: total number of parcels. ρamb=60.6kg∕m3.

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Figure 12

Improved model: spray structure at t=3.0ms

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Figure 13

Improved model with different meshes: spray-tip penetration. Experimental data from Ref. 18, ρamb=60.6kg∕m3.

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Improved model with different meshes: overall SMD. ρamb=60.6kg∕m3.

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Figure 15

Improved model with different meshes: total number of parcels. ρamb=60.6kg∕m3.

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Improved model (ROI collision model) with different meshes: spray-tip penetration. ρamb=60.6kg∕m3.

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Figure 17

Improved model with ROI collision model with different meshes: overall SMD. ρamb=60.6kg∕m3.

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Figure 18

Standard KIVA: spray-tip penetration with different time steps (4×4mm2 mesh)

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Standard KIVA: overall SMD with different time steps (4×4mm2 mesh)

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Standard KIVA: total number of parcels with different time steps (4×42mm mesh)

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Improved spray model: spray-tip penetration with different time steps (4×42mm mesh)

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Figure 22

Improved spray model: overall SMD with different time steps (4×42mm mesh)

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Figure 23

Improved spray model: total number of parcels with different time steps (4×4mm2 mesh)

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Figure 1

Schematic of the new diesel spray model

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Figure 2

Standard KIVA: spray structure at t=3.0ms. ρamb=60.6kg∕m3.

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Figure 3

Standard KIVA: spray-tip penetration. Experimental data from Ref. 18, ρamb=60.6kg∕m3.

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