Anthony A. Amsden

KIVA-3V: A block-structured KIVA program for engines with vertical or canted valves

This report describes an extended version of KIVA-3, known as KIVA-3V, that can model any number of vertical or canted valves in the cylinder head of an internal combustion (IC) engine. The valves are treated as solid objects that move through the mesh using the familiar snapper technique used for piston motion in KIVA-3. Because the valve motion is modeled exactly, and the valve shapes are as exact as the grid resolution will allow, the accuracy of the valve model is commensurate with that of the rest of the program. Other new features in KIVA-3V include a particle-based liquid wall film model, a new sorting subroutine that is linear in the number of nodes and preserves the original storage sequence, a mixing-controlled turbulent combustion model, and an optional RNG {kappa}-{epsilon} turbulence model. All features and capabilities of the original KIVA-3 have been retained. The grid generator, K3PREP, has been expanded to support the generation of grids with valves, along with the shaping of valve ports and runners. Graphics output options have also been expanded. The report discusses the new features, and includes four examples of grids with vertical and canted valves that are representative of IC engines in use today.

The tab method for numerical calculation of spray droplet breakup

A short history is given of the major milestones in the development of the stochastic particle method for calculating liquid fuel sprays. The most recent advance has been the discovery of the importance of drop breakup in engine sprays. We present a new method, called the TAB method, for calculating drop breakup. Some theoretical properties of the method are derived; its numerical implementation in the computer program KIVA is described; and comparisons are presented between TAB-method calculations and experiments and calculations using another breakup model.

A numerical fluid dynamics calculation method for all flow speeds

Abstract The ICE technique for numerical fluid dynamics has been revised considerably, and generalized in such a way as to extend the applicability to fluid flows with arbitrary equation of state and the full viscous stress tensor. The method is useful for the numerical solution of time-dependent fluid flow problems in several space dimensions, for all Mach numbers from zero (incompressible limit) to infinity (hypersonic limit). This new version is considerably less complicated than the original form. The present description does not assume a familiarity with the previous one.

Numerical calculation of multiphase fluid flow

Abstract A new computing technique is described for the solution of fluid flow problems in which several fields interpenetrate and interact with each other. An implicit coupling for each field between mass transport and equation of state allows for calculations in all flow-speed regimes, from far subsonic (incompressible) to far supersonic. In addition, the momentum transport between fields is implicit, allowing for all degrees of coupling, from very loose to completely tied together. Phase transitions permit interchange of mass, momentum and energy between fields, each of which is composed of several components. Considerable generality is present, to permit application to a wide scope of complicated problems, for example, the fluidized dust bed, the flow of a liquid with entrained bubbles, and atmospheric condensation with the fall of precipitation.

KIVA-3V, Release 2: Improvements to KIVA-3V

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.

Numerical calculation of almost incompressible flow

A new method is presented for the numerical solution of time-dependent problems in several space dimensions. The technique is applicable to low-speed (incompressible) flows, to high-speed (supersonic) flows, and to all flow speeds in between, thereby bridging the gap through the almost-incompressible regime in which previously-described techniques break down.

A particle numerical model for wall film dynamics in port-injected engines

To help predict hydrocarbon emissions during cold-start conditions the authors are developing a numerical model for the dynamics and vaporization of the liquid wall films formed in port-injected spark-ignition engines and incorporating this model in the KIVA-3 code for complex geometries. This paper summarizes the current status of the project and presents illustrative example calculations. The dynamics of the wall film is influenced by interactions with the impinging spray, the wall, and the gas flow near the wall. The spray influences the film through mass, tangential momentum, and energy addition. The wall affects the film through the no-slip boundary condition and heat transfer. The gas alters film dynamics through tangential stresses and heat and mass transfer in the gas boundary layers above the films. New wall functions are given to predict transport in the boundary layers above the vaporizing films. It is assumed the films are sufficiently thin that film flow is laminar and that liquid inertial forces are negligible. Because liquid Prandtl numbers are typically about then, unsteady heating of the film should be important and is accounted for by the model. The thin film approximation breaks down near sharp corners, where an inertial separation criterion is used. A particle numerical method is used for the wall film. This has the advantages of compatibility with the KIVA-3 spray model and of very accurate calculation of convective transport of the film. The authors have incorporated the wall film model into KIVA-3, and the resulting combined model can be used to simulate the coupled port and cylinder flows in modern spark-ignition engines. They give examples by comparing computed fuel distributions with closed- and open-valve injection during the intake and compression strokes of a generic two-valve engine.

KIVA-A Comprehensive Model for 2-D and 3-D Engine Simulations

This paper summarizes a comprehensive numerical model that represents the spray dynamics, fluid flow, species transport, mixing, chemical reactions, and accompanying heat release that occur inside the cylinder of an internal combustion engine. The model is embodied in the KIVA computer code. The code calculates both two-dimensional (2D) and three-dimensional (3D) situations. It is an outgrowth of the earlier 2D CONCHAS-SPRAY computer program. Sample numerical calculations are presented to indicate the level of detail that is available from these simulations. These calculations are for a direct injection stratified charge engine with swirl. Both a 2D and a 3D example are shown.

A simple scheme for generating general curvilinear grids

Abstract An intuitively simple approach is presented for the computer generation of two-dimensional curvilinear grids suitable for finite difference solutions of problems in the field of continuum dynamics. An iterative process is employed to transform uniform networks of rectangular zones into more complex configurations. Ease of use and optimal adjustment are stressed, and numerous examples are given.

Flow of interpenetrating material phases

Abstract A previously described numerical technique for the solution of multiphase flow dynamics problems is here both simplified and extended. The simplification cuts down slightly on the momentum coupling among fields, allowing for considerable reduction in complexity of the formulation. The extensions include the capability for compressibility in each material phase, the addition of more interpenetrating fields, and the allowance for motion of a liquid or vapor through a close-packed field of particles. The technique is illustrated by computer-generated plots from a time-varying three-field calculation in a cylindrically symmetric configuration.