During the last few years, the integration of CFD tools in the internal combustion (IC) engine design process has continually increased, allowing time and cost savings as the need for experimental prototypes has diminished. Numerical analyses of IC engine flows are rather complex from both the conceptual and operational sides. In fact, these flows involve a variety of unsteady phenomena and the right balance between numerical solution accuracy and computational cost should always be reached. The present paper is focused on computational modeling of natural gas (NG) direct injection (DI) processes from a poppet-valve injector into a bowl-shaped combustion chamber. At high injection pressures, the gas efflux from the injector and the mixture formation processes include turbulent and compressible flow features, such as rarefaction waves and shock formation, which are difficult to accurately capture with numerical simulations, particularly when the combustion chamber geometry is complex and the piston and intake/exhaust valve grids are moving. In this paper, a three-dimensional moving grid model of the combustion engine chamber, originally developed by the authors to include simulation of the actual needle lift, has been enhanced by increasing the accuracy in the proximity of the sonic section of the critical valve-seat nozzle, in order to precisely capture the expansion dynamics the methane undergoes inside the injector and immediately downstream from it. The enhanced numerical model was then validated by comparing the numerical results to Schlieren experimental images for gas injection into a constant-volume bomb. Numerical studies were carried out in order to characterize the fuel-jet properties and the evolution of mixture formation for a centrally mounted injector configuration in the case of a pancake-shaped test chamber and the real engine chamber. Finally, the fluid properties calculated by the model in the throat section of the critical nozzle were taken as reference data for developing a new effective virtual injector model, which allows the designer to remove the whole computational domain upstream from the sonic section of the nozzle, keeping the flow properties virtually unchanged there. The virtual injector model outcomes were shown to be in very good agreement with the results of the enhanced complete injector model, substantiating the reliability of the proposed novel approach.

1.
Zhang
,
F. R.
,
Okamoto
,
K.
,
Morimoto
,
S.
, and
Shoji
,
F.
, 1998, “
Methods of Increasing the BMEP (Power Output) for Natural Gas Spark Ignition Engines
,” SAE SP-1371
Combustion Processes in Engines Utilizing Gaseous Fuels
, pp.
11
19
.
2.
Kato
,
K.
,
Igarashi
,
K.
,
Masuda
,
M.
,
Otsubo
,
K.
,
Yasuda
,
A.
,
Takeda
,
K.
, and
Sato
,
T.
, 1999, “
Development of Engine for Natural Gas Vehicle
,” SAE SP-1436
Combustion in SI Engines
, pp.
52
60
.
3.
Catania
,
A. E.
,
d’Ambrosio
,
S.
,
Mittica
,
A.
, and
Spessa
,
E.
, 2002, “
Experimental Investigation of Fuel Consumption and Exhaust Emissions of a 16V Pent-Roof Engine Fueled by Gasoline and CNG
,”
SAE Trans. J. Engines
,
110
, pp.
1213
1233
.
4.
d’Ambrosio
,
S.
Spessa
,
E.
Vassallo
,
A.
Ferrera
,
M.
, and
Peletto
,
C.
, 2006, “
Experimental Investigation of Fuel Consumption, Exhaust Emissions and Heat Release of a Small-Displacement Turbocharged CNG Engine
,” SAE Paper No. 2006-01-0049.
5.
Pischinger
,
S.
,
Umierski
,
M.
, and
Hüchtebrock
,
B.
, 2003, “
New CNG Concepts for Passenger Cars: High Torque Engines with Superior Fuel Consumption
,” SAE Paper No. 2003-01-2264.
6.
Papageorgakis
,
G.
and
Assanis
,
D. N.
, 1999, “
Optimizing Gaseous Fuel-Air Mixing in Direct Injection Engines Using an RNG Based κ-ε Model
,”
SAE Trans. J. Engines
,
107
, pp.
82
107
.
7.
Abraham
,
J.
, 1997, “
What is Adequate Resolution in the Numerical Computations of Transient Jets?
,” SAE Paper No. 970051.
8.
Abraham
,
J.
, and
Magi
,
V.
, 1997, “
Computation of Transient Jets: RNG κ-ε Model Versus Standard κ-ɛ Model
,” SAE Paper No. 970885.
9.
Li
,
Y.
,
Kirkpatrick
,
A.
,
Mitchell
,
C.
, and
Willson
,
B.
, 2004, “
Characteristic and Computational Fluid Dynamics Modeling of High-Pressure Gas Jet Injection
,”
ASME J. Eng. Gas Turbines Power
,
126
, pp.
192
197
.
10.
Mather
,
D. K.
, and
Reitz
,
R. D.
, 2002, “
Modeling the Effects of Auxiliary Gas Injection on Diesel Engine Combustion and Emissions
,”
SAE Trans. J. Engines
,
109
, pp.
443
458
.
11.
Ouellette
,
P.
, and
Hill
,
P. G.
, 2000, “
Turbulent Transient Gas Injections,”
ASME J. Fluids Eng.
,
122
, pp.
743
753
.
12.
Li
,
G.
,
Ouellette
,
P.
,
Dumitrescu
,
S.
, and
Hill
,
P. G.
, 1999, “
Optimization Study of Pilot-Ignited Natural Gas Direct-Injection in Diesel Engines
,” SAE Paper No. 1999-01-3556.
13.
Kim
,
G. H.
,
Kirkpatrick
,
A.
, and
Mitchell
,
C.
, 2007, “
Supersonic Virtual Valve Design for Numerical Simulation of a Large-Bore Natural Gas Engine
,”
ASME J. Eng. Gas Turbines Power
129
, pp.
1065
1071
.
14.
Kim
,
G. H.
,
Kirkpatrick
,
A.
, and
Mitchell
,
C.
, 2004, “
Computational Modeling of Natural Gas Injection in a Large Bore Engine
,”
ASME J. Eng. Gas Turbines Power
,
126
, pp.
656
664
.
15.
Chiodi
,
M.
,
Berner
,
H. J.
, and
Bargende
,
M.
, 2006, “
Investigation on different Injection Strategies in a Direct-Injected Turbocharged CNG-Engine
,” SAE Paper No. 2006-01-3000.
16.
Hessel
,
R. P.
,
Abani
,
N.
,
Aceves
,
S. M.
, and
Flowers
,
D.L
, 2006, “
Gaseous Fuel Injection Modeling Using a Gaseous Sphere Injection Methodology
,” SAE Paper No. 2006-01-3265.
17.
Baratta
,
M.
,
Catania
,
A. E.
,
Spessa
,
E.
,
Roessler
,
K.
, and
Herrmann
,
L.
, 2009, “
Multi-Dimensional Modeling of Direct Natural Gas Injection and Mixture Formation in a Stratified-Charge SI Engine with Centrally Mounted Injector
,”
SAE Int. J. Engines
,
1
(
1
), pp.
607
626
.
18.
Hamouda
,
H. B. H.
,
Mairone
,
P.
,
Roessler
,
K.
,
Magnusson
,
I.
, and
Balthasar
,
M.
, 2007,
“NICE Periodic Activity Report Period 3
.”
19.
Fürhapter
,
A.
, 2006, “
Single Cylinder CNG-DI Engine Results
,”
NICE Deliverable A3.5 Report
.
20.
Johnson
,
N. L.
,
Amsden
,
A. A.
,
Naber
,
J. D.
, and
Siebers
,
D. L
, 1994, “
Three Dimensional Modeling of Hydrogen Injection and Combustion
,”
Los Alamos National Laboratory, Technical Report LA-UR-95-210
.
21.
Adamson
,
T. C.
, and
Nicholls
,
J. A.
, 1959, “
On The Structure of Jets From Highly Under-Expanded Nozzles Into Still Air
,”
J. Aerosp. Sci.
,
26
, pp.
16
24
.
22.
Young
,
W. S.
, 1975, “
Derivation of the Free-Jet Mach-Disk Location Using the Entropy-Balance Principle
,”
Phys. Fluids
,
18
(
11
), pp.
1421
1425
.
23.
Reynolds
,
W. C.
, 1980, “
Modeling of Fluid Motions in Engines-An Introductory Overview
,”
Combustion Modeling in Reciprocating Engines
, pp.
41
65
,
J. N.
Mattavi
and
C. A.
Amann
, eds.
Plenum Press
, New York.
24.
Catania
,
A. E.
Magori
,
E.
and
Mitianiek
,
W.
, 2008, “
Computations and Validations, Subsystems
NICE IP Deliverable A3.6.3 Report
.
25.
Goldstein
,
R. J.
, 1996,
Fluid Mechanics Measurement
,
2nd ed.
,
Taylor and Francis
,
London
.
26.
Shapiro
,
A. H.
, 1954,
The Dynamics and Thermodynamics of Compressible Fluid Flow
,
Ronald
,
New York
.
27.
Tritton
,
D. J
, 1977,
Physical Fluid Dynamics
Van Nostrand Reinhold
,
New York
.
28.
Baratta
,
M.
,
Catania
,
A. E.
, and
Pesce
,
F.C.
, 2010, “
Computational and Experimental Analysis of Direct CNG Injection and Mixture Formation in a SI Research Engine
,” ASME Paper No. ICEF2010-35103,
2010 Fall Technical Conference of the ASME ICED
, September 12–15,
San Antonio
,
TX, USA
.
29.
Computational Dynamics, 2006, “
Star-CD v3.26 Methodology Manual
.”
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