Influence Of Fuel Components On The Formation And Oxidation Reactivity Of Onjector Dposit In A Gasoline Direct Injection (GDI) Engine

Compared with port fuel injection engine,GDI engine possesses competitive advantages on fuel economy and power performance.With the development of manufacture technique and electronically controlled fuel injection system,GDI technology has made considerable progress.Meanwhile,GDI engine is faced with problem of emissions and deposits.It's essential to reduce emissions and remove deposits for GDI engine now.Against this background,researchers have done lots of job on the mechanism of particulate emissions and the factors that affect formation of particulates.It does contribute to the understanding of reducing particulate emissions.However,researches about injector deposit are still not enough.And there is still no consensus about the mechanism of injector deposit formation.The factors that affect the properties of injector deposit are still not very clear.Upon this,the influence of fuel components on injector deposits was investigated on a GDI engine.Oxidation activities of injector deposit from different fuels were analyzed.The main content of this thesis is as follows:(1)Injector deposits were collected under different fuel conditions and the oxidation properties were analyzed by using thermogravimetric analyzer(TGA).The activation energy were calculated using Arrhenius-type reaction model.Results show that ethanol,aromatic,Sulphur and Manganese will all reduce the activation energy of injector deposit,thus increase the oxidation activities.(2)Nanostructure of injector deposits from different fuels was observed.It shows that microstructure of injector deposits varies a lot upon different fuels.Ethanol,aromatic as well as Sulphur will contribute to increasing of the length of microcrystal,while Manganese makes inverse affect.When it comes to curvature,Ethanol and Manganese tend to be stimulatory while the other two don't.Conclusion is made that Manganese and Ethanol will help improve oxidation activities and suppress the formation of injector deposit.(3)Elements of injector deposit were analyzed by using a JSM 7800 SEM.Results show that aromatic will increase metallic elements in injector deposits and Manganese will increase the component of Manganese in injector deposits.(4)Spray of injector that with different deposits was measured.It shows that spray angle will increase because of the injector deposits.Meanwhile the spray penetration will be changed.(5)Particulate matter(PM)emissions were measured by using DSM500 fast analyzer.Ethanol and Sulphur can help slow down the formation of injector deposit and also reduce the final amount of injector deposit.Manganese also help slow down the formation of injector deposit but the final amount remains a high level.Aromatics do contribute to the generation of injector deposits.