Liquid breakup in fuel spray and atomization significantly affects the consequent mixture formation, combustion behavior, and emission formation processes in a direct injection diesel engine. In this paper, different models for liquid breakup processes in high-pressure dense diesel sprays and its impact on multi-dimensional diesel engine simulation have been evaluated against experimental observations, along with the influence of the liquid breakup models and the sensitivity of model parameters on diesel sprays and diesel engine simulations. It is found that the modified Kelvin-Helmholtz (KH)–Rayleigh-Taylor (RT) breakup model gives the most reasonable predicted results in both engine simulation and high-pressure diesel spray simulation. For the standard KH-RT model, the model constant Cbl for the breakup length has a significant effect on the predictability of the model, and a fixed value of the constant Cbl cannot provide a satisfactory result for different operation conditions. The Taylor-analogy-breakup (TAB) based models and the RT model do not provide reasonable predictions for the characteristics of high-pressure sprays and simulated engine performance and emissions.
Caterpillar 3401E single cylinder oil test engine (SCOTE)
Bore×stroke/mm
137.2 ×165.1
Compression ratio
16.1:1
Displacement/L
2.44
Connecting rod length/mm
261.6
Squish height/mm
1.57
Intake valve closing/(°) ATDC
–143
Exhaust valve opening/(°) ATDC
130
Tab.1
Injector type
Electronic unit injector (EUI)
Maximum injection pressure/MPa
190
Number of nozzle holes
6
Nozzle hole diameter/mm
0.214
Included spray angle
130˚
Injection rate shape
Rising
Tab.2
Fig.1
Physical process
Model
Drop collision
NTC model [11]
Drop turbulent dispersion
O’Rourke turbulent dispersion model
Drop vaporization
Amsden-Chiang model [23]
Ignition and combustion (Only used in the engine simulation)
Shell+characteristic time combustion (CTC) model [24]
Pollutant formation (Only used in the engine simulation)
Extended Zel’dovich model &Hiroyasu-NS coxidation soot model [25,26]
Tab.3
Fig.2
Injection pressure/MPa
Injection duration/ms
Ambient temperature/K
Ambient density/(kg·m–3)
Injector diameter Dn/mm
180
1.0
950
60
0.1
Tab.4
Case
Breakup Model
1
KH-RT modified model
2
KH-RT model with the breakup length constant Cbl=10 in Eq. (20)
3
KH-RT model with Cbl=20 in Eq. (20)
4
KH-RT model with Cbl=40 in Eq. (20)
5
TAB model (without the drop size distribution)
6
TAB-CHI model (with the chi-squared drop size distribution)
7
TAB-RR model (with the Rosin-Rammler drop size distribution)
Tab.5
Fig.3
Fig.4
Fig.5
Fig.6
Fig.7
Engine speed
Start of injection/(˚) ATDC
Injection duration
EGR/%
Intake pressure/kPa
Intake temperature/K
821
–9
5.5˚
48.34
103
393
Tab.6
Fig.8
Fig.9
Fig.10
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