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In this paper the feasibility of the application of a system conceived by Järvi to a 125 cm3, four strokes motorcycle engine built by Piaggio Company is investigated. This study was carried out using a one-dimensional model built with the well known CFD 1D code Wave and validated in a previous work. An analytical study was performed on the kinematic scheme of the mechanism in order to establish the relationship between control ramp and valve lift. The control ramp shape was then optimized accordingly with the results of the fluid dynamic analysis performed through the above mentioned Wave model.

The efficiency of engine operations, i.e. cold start, transient response and operating at idle, depends on the capability of the injection fuel system to promote a homogeneous mixture formation through an efficient interaction with engine fluid dynamics and geometry. The paper presents the development and the application of a methodology for running a CFD PFI engine simulation. A preliminary assessment of the wall-film and droplet-wall interaction sub models has been carried out in order to validate the methodology. Then a three-step numerical procedure has been adopted. The first two steps are aimed to properly initialize the secondary breakup model depending on the type of injector installed on board in order to achieve accurate predictions of spray characteristics.

The purpose of the study is to develop a flexible simulation tool that allows coupling the 1-D simulation of the engine with the dynamic simulation of the whole vehicle on which the engine is installed, in order to predict vehicle operating conditions and exhaust emissions during an imposed mission profile. In fact 1-D engine simulation can supply information on engine performance but not on vehicle performance, that strongly depends on the vehicle itself. Therefore vehicle performance simulation needs an integrated engine-vehicle approach. The dynamic model of the vehicle (a scooter with CVT transmission) is built up in Matlab-Simulink while the engine model is realized by means of a 1-D commercial code (WAVE, Ricardo Software). In particular, the Urban Driving Cycle (UDC) of the European Community ECE-40 homologation test (established by the EL) directive 2002/51/CE) for a scooter with CVT transmission and centrifugal clutch is the aim of the simulation activity.

The match between the increasing performance demands and stringent requirements of emissions and fuel consumption reduction needs a strong evolution in the 2-wheel vehicle technology. In particular many steps forward should be taken for the optimization of modern small motorcycle and scooter at low engine speeds and low temperature start. To this aim, the detailed understandings of thermal and fluid-dynamic phenomena that occur in the combustion chamber are fundamental. In this work, experimental activities were realized in the combustion chamber of a single-cylinder 4-stroke optical engine. The engine was equipped with a four-valve head of a commercial scooter engine. High spatial resolution imaging was used to follow the flame kernel growth and flame front propagation. Moreover, the effects of an abnormal combustion due to firing of fuel deposition near the intake valves and on the piston surface were investigated.

The paper presents an innovative drive-train for a small scooter, taking advantage of an hybrid (mechanical-electrical) structure. The single parts of this drive train have been dimensioned and the resulting system has been introduced in a simulation program. According to the simulation results the hybridisation is able to enhance the maximum power of the scooter by 1 kW (over 30%), without changing the fuel consumption, and to allow a pure-electric operation with a range over 11 km. Moreover, when the propulsion power comes only from the onboard batteries, and they are recharged from the electric mains, the operation cost per km is less than one half the cost of corresponding fuel consumption of a vehicle without hybridisation.

A very stringent problem in most of European cities is the individual mobility. This problem is mainly caused by traffic jam and arising from this are two particularly interesting environmental issues: pollution and noise [1]. Use of two wheeler vehicles does not represent the final solution to these problems, nevertheless they can supply a useful aid to ease them. Recently, two stroke engines are being replaced with four stroke engines. For small capacity engines this means a true reduction in exhaust emissions, especially unburned hydrocarbons (HC), but, on the other hand it involves a performance reduction, particularly for sudden accelerations, which constitute an essential requirement for these vehicles [2, 3, 4, 5]. Hybridisation can help to fill the gap between two stroke engines and cleaner, but less performing four stroke engines [6]. At the same time, it can help to lower fuel consumption, by means of a reduction in the revolution speed [2, 5].