Search Results

The small engine for two-wheel vehicles has generally high possibility to be optimized at low speeds and high loads. In these conditions fuel consumption and pollutants emission should be reduced maintaining the performance levels. This optimization can be realized only improving the basic knowledge of the thermo-fluid dynamic phenomena occurring during the combustion process. It is known that, during the fuel injection phase in PFI SI engines, thin films of liquid fuel can form on the valves surface and on the cylinder walls. Successively the fuel films interact with the intake manifold and the combustion chamber gas flow. During the normal combustion process, it is possible to achieve gas temperature and mixture strength conditions that lead to fuel film ignition. This phenomenon can create diffusion-controlled flames that can persist well after the normal combustion event. These flames induce the emission of soot and unburned hydrocarbons.

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 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.

This paper describes the development of a control-oriented model that allows the simulation of the Internal Combustion Engine (ICE) thermodynamics, including pressure wave effects. One of the objectives of this work is to study the effects of a Variable Valve Timing (VVT) system on the behavior of a single-cylinder, four-stroke engine installed on a motor scooter. For a single cylinder engine running at relatively high engine speeds, the amount of air trapped into the cylinder strongly depends on intake pressure wave effects: it is essential, therefore, the development of a model that has the ability to resolve the wave-action phenomena, if successful simulation of the VVT system effects is to be performed.

The match among the increasing performance demands and the stringent requirements of emissions and the fuel consumption reduction needs a strong evolution in the two-wheel vehicle technology. In particular, many steps forward should be taken for the optimization of modern small motorcycles and scooters at low engine speeds and high loads. To this aim, detailed understanding of thermo-fluid dynamic phenomena that occur in the combustion chamber is fundamental. In this work, low-cost solutions are proposed to optimize ported fuel injection spark ignition (PFI SI) engines for two-wheel vehicles. The solutions are based on the change of phasing and on the splitting of the fuel injection in the intake manifold. The experimental activities were carried out in the combustion chamber of a single-cylinder 4-stroke optical engine fuelled with European commercial gasoline. The engine was equipped with a four-valve head of a commercial scooter engine.

The purpose of this study is to create and develop a flexible simulating tool that allows to couple the simulation of the engine, performed by means of a 1-D computer-aided engineering code (WAVE, Ricardo Software), along with the dynamic simulation of the whole vehicle on which the engine is installed. The dynamic model of the vehicle (a scooter with CVT transmission) is realized with Simulink, and is schematized as a rigid body subjected to the engine force, aerodynamics forces, tyres friction forces with an equivalent mass which is the sum of the vehicle mass and the rotating equivalent mass. A complete Simulink model of the CVT transmission is realized too. In the present work the authors want to provide a general methodology that permits to numerically evaluate the performance, the operating conditions and exhaust emissions of an engine once it is installed on a given vehicle.