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There exists a strong interaction between the engine cylinder, intake and exhaust gas flow dynamics and the dynamics of mechanical and hydraulic components constituting the valvetrain system, which controls the engine gas flow. Technologies such as turbo-charging and Diesel particulate filtration (DPF) can significantly increase port gas pressure forces acting on the exhaust valve. When such systems are introduced or undergo design modifications, the operation of valvetrain system can be greatly affected and even compromised, which in turn may lead to degradation of performance of the internal combustion engine. Often, the valvetrain system needs to be retuned. Further, predictive analysis of design issues or evaluation of design changes requires highly coupled simulations, combining models of gas pressure forces and the dynamics of all mechanical and hydro-mechanical parts constituting the valvetrain.

Changing and more stringent emissions norms and fuel economy requirements often call for modifications in the fuel injection system of a Diesel engine. There exists a strong interaction between the injection system hydraulics and the dynamics of mechanical components within the unit injector and the camshaft-driven mechanical system used to pressurize it. Hence, accurate predictive analysis of design issues or evaluation of design changes requires highly coupled and integrated hydro-mechanical simulations, combining analysis of fuel injection hydraulics and the dynamics of all mechanical parts, including the cam-drive system. This paper presents an application of such an integrated model to the study and alleviation of an observed increase in mechanical vibration and related noise levels associated with a proposed design change in unit injectors and valve-train of a 6-cylinder truck diesel engine.

A new model of spur gear contact and gear dynamics was developed for use in studies of dynamic response of mechanical systems involving geartrains. The model is general; in this paper it is applied to geartrain dynamics in valvetrain gear drives. The model dynamically uses a gear contact formulation based on exact involute geometries of gear teeth and can therefore account for varying, non-linear mesh stiffness. It can also account for gear torsional stiffness as well as shaft stiffness at gear centers. The paper further proposes an alternative to dynamic calculation of instantaneous gear tooth contact conditions. The proposed method uses a varying effective mesh stiffness pre-computed through static calculation of contact conditions between teeth of a gear pair, for one mesh, or tooth engagement-disengagement, period. The technique is shown to significantly reduce computational time, while closely matching the predictions of the full model.