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Exhaust acoustics simulation is an important part of the exhaust system process. Especially important is the trend towards a coupled approach to performance and acoustics design. The present paper describes a new simulation tool developed for such coupled simulations. This tool is based on a one-dimensional fluid dynamics solution of the flow in the engine manifolds and exhaust and intake elements. To represent the often complex geometries of mufflers, an easy-to-use graphical pre-processor is provided, with which the user builds a model representation of mufflers using a library of basic elements. A comparison made to two engines equipped with exhaust silencers, shows that the predictions give good results.

An increasing emphasis is being placed in the vehicle development process on transient operation of engines and vehicles, and of engine/vehicle integration, because of their importance to fuel economy and emissions. Simulations play a large role in this process, complementing the more usual test-oriented hardware development process. This has fueled the development and continued evolution of advanced engine and powertrain simulation tools which can be utilized for this purpose. This paper describes a new tool developed for applications to transient engine and powertrain design and optimization. It contains a detailed engine simulation, specifically focused on transient engine processes, which includes detailed models of engine breathing (with turbocharging), combustion, emissions and thermal warm-up of components. Further, it contains a powertrain and vehicle dynamic simulation.

Engine and vehicle development is a multi-step process: from component design, to system integration, to system control. There is a multitude of tools that are currently being used in the industry for these purposes. They include detailed simulations for component design on one hand, and simplified models for system and control applications on the other hand. This introduces one basic problem: these tools are almost totally disconnected, with attendant loss of accuracy and productivity. An integrated simulation tool has been developed, which is applicable to all of the design issues enumerated above. A key feature introduced for the first time by this new tool is that it is truly a single code, with identical handling of engine and powertrain elements. Further, it contains multiple levels of engine and powertrain models, so that the user can select the appropriate level for the project at hand (e.g. depending on the time scale of the problem).

A multi-purpose valvetrain analysis tool has been developed, which is aimed at addressing all design issues arising in various stages of valvetrain development. Its capabilities include polynomial cam design, valvetrain mechanism kinematics, quasi-dynamic analysis, spring design/selection, multi-body elastic analysis of a single valvetrain with cam-follower and bearing tribology, and multi-valvetrain dynamics with camshaft torsional vibrations. The basic architecture of this tool is object-oriented. Its underlying basis is a library of cam design methods, kinematics operators, and dynamics/hydraulics/tribology primitives (masses, dampers, springs, etc.). On top of this basic system lies a higher-level library of valvetrain compound objects, which are pre-programmed sub-assemblies of valvetrain components built from the primitives. These high level objects minimize modeling effort and may be mixed with primitives, allowing construction of models for virtually any valvetrain.