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Internal Combustion Engines

Characterizing Diesel Fuel Spray Cone Angle From Back-Scattered Imaging by Fitting Gaussian Profiles to Radial Spray Intensity Distributions

[+] Author and Article Information
Jaclyn E. Johnson

Department of Mechanical Engineering,  Michigan Technological University, 1400 Townsend Drive, Houghton, MI, 49931jenesbit@mtu.edu

Jeffrey D. Naber

Department of Mechanical Engineering,  Michigan Technological University, 1400 Townsend Drive, Houghton, MI, 49931jnaber@mtu.edu

Seong-Young Lee

Department of Mechanical Engineering,  Michigan Technological University, 1400 Townsend Drive, Houghton, MI, 49931sylee@mtu.edu

J. Eng. Gas Turbines Power 134(6), 062802 (Apr 13, 2012) (8 pages) doi:10.1115/1.4005994 History: Received October 21, 2011; Revised November 08, 2011; Published April 13, 2012; Online April 13, 2012

Quantifying fuel spray properties including penetration, cone angle, and vaporization processes sheds light on fuel-air mixing phenomenon, which governs subsequent combustion and emissions formation in diesel engines. Accurate experimental determination of these spray properties is a challenge but imperative to validate computational fluid dynamic (CFD) models for combustion prediction. This study proposes a new threshold independent method for determination of spray cone angle when using Mie back-scattering optical diagnostics to visualize diesel sprays in an optically accessible constant volume vessel. Test conditions include the influence of charge density (17.6 and 34.9 kg/m3 ) at 1990 bar injection pressure, and the influence of injection pressure (990, 1370, and 1980 bar) at a charge density of 34.8 kg/m3 on diesel fuel spray formation from a multi-hole injector into nitrogen at a temperature of 100 °C. Conventional thresholding to convert an image to black and white for processing and determination of cone angle is threshold subjective. As an alternative, an image processing method was developed, which fits a Gaussian curve to the intensity distribution of the spray at radial spray cross-sections and uses the resulting parameters to define the spray edge and hence cone angle. This Gaussian curve fitting methodology is shown to provide a robust method for cone angle determination, accounting for reductions in intensity at the radial spray edge. Results are presented for non-vaporizing sprays using this Gaussian curve fitting method and compared to the conventional thresholding based method.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Michigan Tech optically accessible combustion vessel (left). Internal view of combustion chamber (right).

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Figure 2

Back scattering imaging setup

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Figure 3

Spray cone angle definition

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Figure 4

Sample Gaussian curve fit to spray intensity distribution at 45Do from the spray tip, including intersection points for the curve fit with the intensity equal to zero axis. Curve fit R2 is 0.99 and NRMSE is 2.6, equation is: I95.4·exp(-(Y-41.0)22·(3.2)2)-13.9.

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Figure 5

Cone angle definition and curve fit methodology used in the thresholding method

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Figure 6

Non-vaporizing spray images as a function of time ASOI for the three injection pressures investigated. Charge density of 34.8 ± 0.1 kg/m3 , gas temperature of 100 °C, 1.4 ms fuel injection duration.

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Figure 7

Mean cone angle over eight plumes as a function of time ASOI for the injection pressure sweep. Error bar correspond to ±10% sensitivity study. Mean cone angle results from the ±10% sensitivity study are included for the 1980 bar case to visualize spread.

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Figure 8

Gaussian and threshold method comparison (1980 bar injection, density 34.8 kg/m3 , temperature 100 °C at 0.45 ms ASOI). Horizontal line defines 45Do , circles and linear lines show spray edge and cone angle, respectively.

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Figure 9

Change in mean cone angle over entire injection event for the ±10% sensitivity study comparing Gaussian and threshold methods

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Figure 10

Mean cone angle over eight plumes as function of time ASOI for charge density sweep. Error bar correspond to the ±10% sensitivity study.

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Figure 11

Change in mean cone angle over entire injection event for the ±10% sensitivity study comparing Gaussian and threshold methods

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