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This paper describes a research activity, carried out at the University of Perugia, focused on the modelling of an automatic reed valve in a coupled fluid-structure approach. The application here concerned is a reed device used to control a Secondary Air Injection (SAI) system which allows ambient air to enter the exhaust pipe upstream of the catalyst (useful for the reduction of emissions in rich mixture engine operating conditions). Since currently no commercial codes are still available for simulating in a comprehensive way the non-linear dynamics of a reed valve device with position constraints, the main objective of the work is the calculation of the air mass flow rate admitted to the exhaust system through the reed, by means of a slim and easy software tool. The task is accomplished by integrating two different codes, developed by the authors.

This work deals with the CAE simulation of the behaviour of a belt employed in a CVT transmission of a large displacement scooter engine. Both FEM and MBS simulations were performed, in order to estimate the dynamic loads acting on the component and the stress state the belt is subject to. The MBS simulations were backed up by simple FEM tests performed in order to estimate the elastic properties of elementary portions of the belt. The MBS system comprised the belt and the two pulleys. As a result, the force components the pulleys exert on the belt were calculated. FEM non-linear analyses were performed in order to estimate the stress state the belt experiences. The belt's both manufacturing and working conditions were simulated.

The advantages of air assisted direct fuel injection systems to achieve high atomization degree into the combustion chamber of SI engines are well-known. The solutions up to now proposed appear anyway poorly tailored to be suitable for small engine applications. In fact scaling down such existing systems for automotive applications, they present mainly two drawbacks: the costs and a difficult tuning of the very low quantity of fuel required per cycle. Moreover the amount of electric energy required makes the engines not self-sufficient. To overcome the above mentioned problems, Piaggio has developed a completely mechanical low cost fuel injection system, named FAST (Fully Atomized Stratified Turbulence), which does consent a very atomized and stratified mixture lean combustion process, i.e. a dramatic improvement of emissions and fuel consumption. After general considerations, the application of such system to a small capacity 2T engine is analyzed.

In the automotive industry, computer simulation techniques have been developed to improve the 4-stroke engine development process. The objectives are to reduce engine development time, optimise engine performance, improve refinement, and to achieve legislative noise and emissions requirements. The application of these methods to a 4 stroke scooter engine has been evaluated. This paper describes how computer simulation techniques have been used to assist with the development of a new 125cc 2 valve 4 stroke scooter engine built by Piaggio Veicoli Europei Spa, and to evaluate an advanced 4-stroke scooter engine concept. A single dimensional fluid dynamic analysis code WAVE has been used to simulate engine performance and inlet/exhaust noise during prototype development. To support this analysis, pseudo-static valve train analysis using a multi-polynomial camshaft design approach has been used to optimise valve train performance.