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Research Papers: Internal Combustion Engines

A Numerical Investigation of Transient Flow and Cavitation Within Minisac and Valve-Covered Orifice Diesel Injector Nozzles

[+] Author and Article Information
Won Geun Lee, Rolf D. Reitz

Engine Research Center, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, WI 53706

J. Eng. Gas Turbines Power 132(5), 052802 (Mar 05, 2010) (8 pages) doi:10.1115/1.4000145 History: Received April 30, 2009; Revised May 14, 2009; Published March 05, 2010; Online March 05, 2010

Cavitating flow within diesel injector passages has been investigated numerically using the homogeneous equilibrium model (HEM), which uses the barotropic assumption and the variable speed of sound of the mixture. To apply the HEM, the KIVA-3V code was modified to implement a generalized equation of state, and injector needle movement is simulated by the arbitrary Lagrangian-Eulerian (ALE) approach and the snapper algorithm. It is demonstrated that the model can predict the effect of nozzle passage geometry on the flow structure and cavitation. The model is able to reproduce the transient fuel injection rate as a function of the needle lift profile. Special interest is focused on the transient behavior during the nozzle closing period, which shows that the fast decrease in flow rate can increase the cavitation in the nozzle passage. The effects of the pressure difference and environment pressure on cavitation augmentation at the end-of-injection were also investigated. Flow characteristics due to different shapes of the nozzle flow passage in axisymmetric single hole nozzles and multihole nozzle configurations (minisac and valve-covered orifice eight-hole nozzles) were compared with emphasis on the end-of-injection period.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

(a) Speed of sound of the HEM and (b) the pressure-density relation in the liquid-vapor mixture

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Figure 2

Typical shape and mesh for single hole nozzles

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Figure 3

Meshes for MS and VCO nozzles

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Figure 4

Needle lift profiles

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Figure 5

Flow and cavitation inside single hole nozzles under ΔP/P2=1100/60 bars reaches quasisteady state

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Figure 6

Coefficients representing the exit condition of the Sng-1 nozzle, ΔP/P2=1100/60 bars

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Figure 7

Cavitation collapsed due to the gradual decrease in exit velocity at the end-of-injection (closing speed=0.175 m/s)

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Figure 8

Cavitation enhanced due to the fast decrease in exit velocity at the end-of-injection (closing speed=0.7 m/s)

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Figure 9

Comparison of flow conditions at the nozzle exit, and pressure and density inside the nozzle, ΔP/P2=1100/60 bars (needle closing speed: left=0.175 m/s and right=0.70 m/s)

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Figure 10

Cavitation generation in a Sng-1 nozzle at the end-of-injection with a needle closing speed of 0.7 m/s

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Figure 11

Flow patterns in minisac (left) and VCO nozzles (right)

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Figure 12

Cavitation in the minisac nozzle at the end-of-injection (closing speed=0.175 m/s)

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Figure 13

Cavitation in the VCO nozzle at the end-of-injection (closing speed=0.175 m/s)

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Figure 15

Cavitation in the minisac nozzle at the end-of-injection (closing speed=0.70 m/s)

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Figure 16

Cavitation in the VCO nozzle at the end-of-injection (closing speed=0.70 m/s)

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Figure 14

Flow conditions at the nozzle exit and density inside the nozzle, ΔP/P2=1500/5 bars, needle closing speed of 0.175 m/s (left=minisac and right=VCO)

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Figure 17

Flow conditions at the nozzle exit and density inside the nozzle, ΔP/P2=1500/5 bars, needle closing speed of 0.70 m/s (left=minisac and right=VCO)

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Figure 18

X-ray image of the fuel spray evolution at the end-of-injection (courtesy of the Argonne National Laboratory)

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