The efficiency of the small engines for the two-wheel vehicles can be further improved especially at low speeds and high loads. In these conditions fuel consumption and pollutant emission should be reduced maintaining the performance levels. This optimization can be realized only by the improvement in 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. These flames persist well after the normal combustion event and induce the formation and then the exhaust emission of soot and unburned hydrocarbons. In this paper, experimental activities were carried out in the combustion chamber of a single-cylinder optical engine in order to investigate the in-cylinder formation and exhaust emission of particulate from a 4-stroke engine for 2-wheel vehicle. The engine was equipped with the four-valve head of a commercial scooter engine and it was fuelled with European commercial gasoline. Cycle-resolved digital imaging and high spatial resolution visualization with two-color pyrometry tool were used to follow in detail the flame front propagation and related phenomena. In particular the inception of diffusion-controlled flames near the valves and on the cylinder walls was studied. These flames induced the in-cylinder formation of unburned hydrocarbons and soot particles and the following exhaust emissions The optical data were correlated with conventional combustion pressure measurements and particulate exhaust emission ones. The effect of three way catalyst was investigated too.
In-cylinder formation and exhaust emission of particulates from a 4-stroke engine of a 2-wheel vehicle
Merola SS;Sementa P;Tornatore C
2009
Abstract
The efficiency of the small engines for the two-wheel vehicles can be further improved especially at low speeds and high loads. In these conditions fuel consumption and pollutant emission should be reduced maintaining the performance levels. This optimization can be realized only by the improvement in 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. These flames persist well after the normal combustion event and induce the formation and then the exhaust emission of soot and unburned hydrocarbons. In this paper, experimental activities were carried out in the combustion chamber of a single-cylinder optical engine in order to investigate the in-cylinder formation and exhaust emission of particulate from a 4-stroke engine for 2-wheel vehicle. The engine was equipped with the four-valve head of a commercial scooter engine and it was fuelled with European commercial gasoline. Cycle-resolved digital imaging and high spatial resolution visualization with two-color pyrometry tool were used to follow in detail the flame front propagation and related phenomena. In particular the inception of diffusion-controlled flames near the valves and on the cylinder walls was studied. These flames induced the in-cylinder formation of unburned hydrocarbons and soot particles and the following exhaust emissions The optical data were correlated with conventional combustion pressure measurements and particulate exhaust emission ones. The effect of three way catalyst was investigated too.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
