Engines and Burners
The legislation for reduced emissions and particulates,
the exploration of new fuels and engine designs and the competitive need
for increased efficiency and performance are challenging the entire engine
design community. At this time of great need and increased competition,
the use of computational modeling is coming of age and providing many
design groups with a competitive edge. As a way of an introduction, the
following is a list of broad areas in which modeling has proven useful.
As a design tool with minimal experimental support. In a few areas,
modeling accuracy and capability have sufficiently evolved such that validation
by experiments it is no longer necessary. The premiere example is the
three-dimensional simulation of air induction, and the consequent prediction
of the flow at time of combustion. Current capabilities have evolved to
treat the complexities of engine geometries, most notably for valves and
intake manifolds. Simulations can be quickly executed, and many configurations
can be examined.
As an interpolative design tool with experimental validation. Often
there is sufficient uncertainty in the accuracy of the models, such that
experiments are required for validation. But once validated, the models
can be used to examine the effects of variations in operating conditions,
geometry, and fuels on engine performance or emissions, to within the
regime of validation. The thermodynamic or zero-dimensional models have
long proven their utility in this area. Similarly, multi-dimensional simulation
codes are beginning to contribute equally to issues such as combustion
timing, fuel composition or injection history.
As an analysis tool in the interpretation of complex experiments.
One of the most rewarding applications of modeling is the integration
of experiments and computational analysis. Once a simulation is validated
with measurable experimental results, a greater understanding of engine
phenomena can be inferred from the detailed information obtainable from
As an explorative tool for alternative engine designs. Many alternative,
but promising, engine designs can be initially investigated by using computational
modeling, without the cost of expensive prototypes. Experimental validation
can then be applied once the possibilities for a design or modification
As a developmental tool for improved physical or numerical submodels.
A continual challenge for developers of the engine modeling capability
is the goal of an accurate solution in a short time, requiring minimal
computer resources. For a previously validated simulation capability,
the results of more accurate, faster or more memory-efficient physical
or numerical submodels can be compared to prior computational results.
The above is from the Preface of Modeling
in Diesel and SI Engines,
SAE Publication SP-1123, N. L Johnson and Y. Takagi, editors.
Perspective on the history of engine modeling in T-3
Reactive flow and combustion modeling of fully miscible
species is the area of broadest use of simulation codes from T-3 and possibly
from Los Alamos. Currently these are represented by the KIVA family of
codes [Amsden, 1993] [Amsden et al, 1989].
The KIVA codes are in worldwide useby industry, academia, and government
laboratories. Their popularity as research tools [Amsden et
al, 1993], primarily because of the availability of the source code
and of thier unique treatment of sprays- now generally considered a worldwide
the intended applications are to flow and combustion modeling in spark-ignition
and diesel engines and gas turbines (as in Fig. 3.1-1), the extreme versatility
and range of features have made KIVA programs attractive to a variety
of non-engine applications as well. These range in scale from proposed
500-foot-high convection towers with water sprays that clean and cool
the air in polluted urban areas, down to modeling silicon dioxide condensation
in high pressure oxidation chambers used in the production of microchip
wafers. Other applications have included the analysis of flows in automotive
catalytic converters, power plant smokestack cleaning, pyrolytic treatment
of biomass, design of fire suppression systems, pulsed detonation propulsion
systems, stationary burners, aerosol dispersion, and design of heating,
ventilation, and air conditioning systems. A complete history of KIVA
as a paradigm of technology transfer from the government laboratories
to industry can be found in [Amsden et al, 1993].
current version of KIVA-3 uses an unstructured mesh of hexahedrons that
are groups of logical blocks of mesh and an all-speed ALE formulation
from the SALE heritage. Because of the ability to model opening and closing
of ports and valves, connectivity of the mesh can change during the simulation.
This is a unique feature of the currently active codes in T-3 (also see
CAVEAT-GT below). KIVA is also unique in that it contains a Lagrangian
particle treatment of liquid spays as originally proposed by Dukowicz
[Dukowicz, 1980]. The current spray model includes breakup, collisions
and evaporation, coupled with the turbulent gas field. This model is inherently
stochastic, in contrast to the deterministic nature of all other T-3 CFD
codes, and only produces an average solution for a large number of particles.
The transport and chemistry equations can treat an arbitrary number of
species and reactions, both kinetic and equilibrium. Mixing-controlled
combustion that works in conjunction with the k-e turbulence model and
a soot model are provided.
Parallel with the effort to continue the maturation of KIVA-3, future
versions of KIVA are being developed. These codes use largely the same
numerics as KIVA-3 but address the requirements of parallel computer architectures
and requirements of modern mesh generation codes. KIVA-F90 is a complete
rewrite of KIVA-II using Fortran 90 and executes on workstations, massively
parallel architectures, and supercomputers without modification. KIVA-AC,
just now under development, is an unstructured mesh version of KIVA-F90
that will support combinations of tetrahedrons and hexahedrons.
Los Alamos Engines and Burners Projects
All of the filled circles are linkable projects.
All of the empty circles are navigational guides.
- Valves and ports
- Diesel Engine Port Flow
- High Power Density
Questions? Contact us!
This is from "The Legacy and Future of CFD at Los Alamos"
(LAUR#LA-UR-1426)(365Kb pdf file)
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