KIVA-3V, RELEASE 2, IMPROVEMENTS TO
KIVA-3V
Title:
Author(s):
Submitted to:
LA-13608-MS (May 1999)
Anthony A. Amsden
, T-3
LAMS Report
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distribution is unlimited.
KIVA-3V, RELEASE 2:
IMPROVEMENTS TO KIVA-3V
by
Anthony A. Amsden
ABSTRACT
This report describes the changes made in the KIVA-3V computer
program since its initial release version dated 24 March 1997. A variety of new
features enhance the robustness, efficiency, and usefulness of the overall
program for engine modeling. Among these are an automatic restart of the
cycle with a reduced timestep in case of iteration limit or temperature
overflow, which should greatly reduce the likelihood of having the code crash
in mid run. A new option is the automatic deactivation of a port region when it
is closed off from the engine cylinder and its reactivation when it again
communicates with the cylinder. A number of corrections throughout the code
improve accuracy, one of which also corrects the 2-D planar option to make it
properly independent of the third dimension. Extensions to the particle-based
liquid wall film model make the model somewhat more complete, although it
is still considered a work-in-progress. In response to current research in fuel-
injected engines, a split-injection option has been added. A new subroutine
monitors the whereabouts of the liquid and gaseous phases of the fuel, and for
combustion runs the energy balance data and emissions are monitored and
printed. New features in the grid generator K3PREP and the graphics post-
processor K3POST are also discussed.
CONTENTS
ABSTRACT ......................................................................................................................1
I. INTRODUCTION AND BACKGROUND........................................................2
II. AUTOMATIC RESTART OF CYCLE WITH REDUCED TIME STEP...........3
III. PORT DEACTIVATION AND REACTIVATION............................................4
IV. ACCURACY IMPROVEMENTS.........................................................................6
A. Elimination of Diffusion Through Zero-Thickness Walls...................6
B. Mass Conservation in Snapper Subroutines .........................................6
C. Timestep Control on Number of Advective Flux Subcycles ..............8
D. UDOTN and PARTE terms in Subroutine LAWALL..........................8
E 2-D Planar Grids........................................................................................8
F. Fuel Library Corrections ..........................................................................9
G. Droplet Distortion from Sphericity ........................................................9
H. Correction of Miscellaneous Typos......................................................10
V. EXTENSIONS TO THE WALL FILM MODEL...............................................11
A. Splash Velocities of Secondary Droplets .............................................11
B. Impingement Pressure Spreading ........................................................11
C. Particle Momentum and Energy...........................................................12
D. Gravitational Terms................................................................................13
E. Miscellaneous Corrections to the Wall Film Model...........................13
VI. OTHER NEW FEATURES .................................................................................14
A. Split Injection ...........................................................................................14
B. Expanded Monitoring for Engine Calculations..................................14
C. Particle Evaporation Cutoff in Subroutine EVAP..............................15
D. Particle Energy Coupling Above Valves in Subroutine PCOUPL...16
VII. DATA STORAGE................................................................................................17
VIII. ADDITIONS TO FILE ITAPE5..........................................................................22
IX. ADDITIONS TO K3PREP ..................................................................................23
A. Rounding of Runner Segments.............................................................23
B. Valve Guides............................................................................................24
C. Cell-Face Boundary Conditions for Valve Stems ...............................24
D. Miscellaneous Changes and Notes.......................................................25
E. Diesel Engine Grid with Vertical Valves and a Piston Bowl............26
X. CHANGES TO K3POST.....................................................................................32
A. Cutting Plane Rotation...........................................................................32
B. Plot Correction at Interface with Deactivated Region.......................32
ACKNOWLEDGMENTS ...............................................................................................33
REFERENCES..................................................................................................................34
2
I. INTRODUCTION AND BACKGROUND
Since the introduction of the original KIVA in 1985,
1Ð3
KIVA programs
have become by far the most widely used CFD (computational fluid dynamics)
programs for multidimensional combustion modeling. Worldwide interest grew
with the 1989 introduction of KIVA-II
4,5
and its improved numerical-solution
algorithms. Although these two earlier versions lent themselves well to confined
flows, they were quite inefficient for complex engine geometries or any
application involving complicated boundary conditions. In KIVA-3
6
(1993) a
block-structured mesh was adopted, and the program became a practical tool for
modeling geometries containing inlet and outlet ports in the cylinder wall. This
development was driven by an interest in crankcase-scavenged 2-stroke engines
in the early 1990s.
With the introduction of KIVA-3V
7
in March 1997, an effective approach to
modeling moving valves became available. No previous capability has been
sacrificed along the way, and KIVA has matured to where it can be applied to
full-engine-cycle calculations in virtually any 2- or 4-stroke design that has
valves, ports in the cylinder wall, or even a combination of the two. KIVA-3V is
now routinely applied to studies of both port fuel injection (PFI) and direct
injection, spark-ignition (DISI) or gasoline direct-injection (GDI) engines, as well
as large- and small-bore diesels, but the capabilities of the program also make it
attractive for a variety of other applications that involve complex geometries,
chemical reactions, liquid sprays, and wall films.
This second release of KIVA-3V makes available to the user community a
variety of features and corrections that have been added to the program over the
past two years. These changes were briefly outlined in the abstract above and are
described in more detail in the following sections.
For those readers new to KIVA, the Los Alamos reports for KIVA-II,
5
KIVA-3,
6
and KIVA-3V
7
are available electronically. The KIVA Website at
http://t3.lanl.gov/Kiva/Kiva.html contains further information. In addition to
providing links to these reports, the Website tells how to obtain KIVA-3V and
how to subscribe to kiva-news and kiva-talk on the Internet; and gives links to
several other installations that use KIVA programs.
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