The variability of diesel jet structure, both as a function of time and between individual injection events, has important implications on the breakup and mixing of the jet. It is accepted that diesel jets become unstable due to interactions with the ambient gas, leading to breakup of the jet. This concept is the principle behind the Kelvin–Helmholtz and Rayleigh–Taylor models of diesel atomization. Very little information regarding diesel jet variability is available, however, in the near-nozzle region of the diesel jet, where primary breakup of the jet occurs. This is due to the presence of many small droplets, which strongly scatter visible light and render the spray opaque. X-ray radiography has been successfully used in recent years to probe the structure of diesel sprays with high spatial and temporal resolutions. All of these previous measurements, however, were ensemble averaged, measuring only persistent features of the spray. In the current study, measurements are performed at individual measurement points of single diesel injection events. These measurements are taken at several points near the injector exit for a nonhydroground nozzle with a single axial hole at two injection pressures ($500bars$ and $1000bars$). The variability of the start of injection, end of injection, and the time history of the spray density during the injection event are examined, as well as how these quantities change for different transverse positions across the jet.

1.
Desantes
,
J. M.
,
Payri
,
R.
,
,
F. J.
, and
Gil
,
A.
, 2006, “
Development and Validatioan of a Theoretical Model for Diesel Spray Penetration
,”
Fuel
0016-2361,
85
(
7–8
), pp.
910
917
.
2.
Naber
,
J.
, and
Siebers
,
D.
, 1996, “
Effects of Gas Density and Vaporization on Penetration and Dispersion of Diesel Sprays
,” SAE Paper No. 960034.
3.
Lai
,
M.-C.
,
Wang
,
T.-C.
,
Xie
,
X.
,
Han
,
J.-S.
,
Henein
,
N.
,
Schwarz
,
E.
, and
Bryzik
,
W.
, 1998, “
Microscopic Characterization of Diesel Sprays at VCO Nozzle Exit
,” SAE Paper No. 982542.
4.
Blessing
,
M.
,
König
,
G.
,
Krüger
,
C.
,
Michels
,
U.
, and
Schwarz
,
V.
, 2003, “
Analysis of Flow and Cavitation Phenomena in Diesel Injection Nozzles and Its Effects on Spray and Mixture Formation
,” SAE Paper No. 2003-01-1358.
5.
Cai
,
W.
,
Powell
,
C. F.
,
Yue
,
Y.
,
Narayanan
,
S.
,
Wang
,
J.
,
Tate
,
M.
,
Renzi
,
M.
,
Ercan
,
A.
,
Fontes
,
E.
, and
Gruner
,
S.
, 2003, “
Quantitative Analysis of Highly Transient Fuel Sprays by Time-Resolved X-Radiography
,”
Appl. Phys. Lett.
0003-6951,
83
(
8
), pp.
1671
1673
.
6.
Cheong
,
S.-K.
,
Liu
,
J.
,
Shu
,
D.
,
Wang
,
J.
, and
Powell
,
C. F.
, 2004, “
Effects of Ambient Pressure on Dynamics of Near-Nozzle Diesel Sprays Studied by Ultrafast X-Radiography
,” SAE Paper No. 2004–01-2026.
7.
Powell
,
C. F.
,
Ciatti
,
S.
,
Cheong
,
S.-K.
,
Liu
,
J.
, and
Wang
,
J.
, 2004, “
X-Ray Absorption Measurement of Diesel Sprays and the Effect of Nozzle Geometry
,” SAE Paper No. 2004-01-2011.
8.
Kastengren
,
A.
,
Powell
,
C. F.
,
Riedel
,
T.
,
Cheong
,
S.-K.
,
Wang
,
Y.-J.
,
Im
,
K.-S.
,
Liu
,
X.
, and
Wang
,
J.
, 2007, “
Determination of Diesel Spray Axial Velocity Using X-Ray Radiography
,” SAE Paper No. 2007-01-0666.
9.
Kastengren
,
A.
, and
Powell
,
C. F.
, 2007, “
Spray Density Measurements Using X-Ray Radiography
,”
Proc. Inst. Mech. Eng., Part D (J. Automob. Eng.)
0954-4070,
221
(
16
), pp.
653
662
.
10.
Bendat
,
J.
, and
Piersol
,
A.
, 2000,
Random Data Analysis and Measurement Procedures
,
Wiley
,
New York
.