A Study Of Controlled Charging And Quasi-Homogeneous Lean Burn On A Small Si Engine

More and more attention are attached to the issue of environment pollution and energy source lacking which make automobile industries be in face of great challenge, and developing efficient, economical and ultra-low emissions gasoline engines are put in the first place of what the I.C engine researchers should do. The study of lean burn technology was today's one mainstream of the development of automotive gasoline engines on account of the excellent fuel economy and lower emissions. Small spark ignition engines are the chief power of cars and motorcycles, the study of which are meaningful.In this thesis we worked in a creative way to apply three dimensional virtual design method on the base of advanced laser measuring system to develop a kind of simple and useful continuous controlled charge device which can realize continuous controlling of intake swirl and synchronization controlling easily, and the new continuous controlled charge system is different from the traditional variable intake system with controlling valve in the status of the full open of the revolving valve not to hold up the inlet manifold of air flow and not to affect the effectiveness of the air-charging.We appraised the swirl and tumble capability of the new system on the steady flow rig and the result of test show that there exists an inclined swirl in the fact of more tumble and few swirl. In the different way from the traditional way which to improve the intake airflow characteristic by changing the shape of inlet manifold, the engine with the continuous controlled charge system not only can increase the intensity of inlet airflow dramatically but also not decrease air flowing capability in the needed high power and high torque conditions. In this way, the flowing of airflow is helpful for combustion, which was verified from the result of test in the electronic control fuel injection engine.In this thesis we have a try to realize the quasi-homogeneous lean burn of twice injection which show a conclusion that the quasi-homogeneous lean burn can be realized only by the method of twice injection without any structure changing of small high speed engine such as the engine of motorcycle, and can enhance capability of engine. The manufacturers need not change equipment and workshop in the application of this new technology. Low cost and high effectiveness make it applicable and useful which decide a bright marketing future of it.The test of twice injection shows that we should pay attention to the exact timing and the proportion of fuel twice injection in accordance with the airflow intensity. It is true that the airflow intensity make a great influence on the timing of the fuel twice injection, which is shown clearly by the increase of the airflow intensity. The most appropriate timing of the twice injection is shown with the direction of the pre-decreasing angle of gas injection, namely, the later period of intake process with the shift of direction.The controlled charge engine combined with the technology of twice injection, in comparison with the original engine, improve lean misfire limit 4 air-fuel ratio, decrease the fuel consumption by 18 %, the characteristic of engine emissions has been improve apparently as well, and the improvement of CO emission get to 50~60%, the improvement of NOx emission get to 65~75% in comparison with the emissions of single injection without swirl controlling valve.