Measurements of Diesel Fuel Wall Films
Examensarbete för masterexamen
Hervás, Francisco de Borja
Nowadays, environmental issues become one of the priorities for automotive's world industry. Thus, combustion problems related to wall films in direct injection engines, e.g. in HCCI engines, turn into important matters. Several studies about wall films have been conducted, nevertheless, there is not yet a real basis of knowledge on the field. This work presents a study about Diesel fuel wall films performed at Chalmers in the HP/HT spray rig using optical methods with the motivation of start to create a data base concerning Diesel fuel films. In order to perform this innovative experiment in the HT/HP spray chamber a new device called "wall" has been designed. The wall allows the use of two optical methods: Laser Induced Fluorescence (LIF) and Refractive Index Matching (RIM). The LIF technique relies on the idea that, upon excitation by laser light, the intensity of the fluorescent signal from a tracer in the fuel is proportional to the film thickness. The RIM technique is based on the dependance between scattered light intensity and film thickness when illuminated by a light source. Tests were done applying the LIF method using two different setups, Ar-Ion continuous laser with high speed camera and Nd:Yag pulsed laser with an CCD camera. The fuel used was commercial Diesel, Swedish Environmental Class 1, with addition of a chemical tracer to increase the fluorescence. Several parameters, such as air temperature and air pressure, were chosen to achieve both evaporating and non-evaporating conditions. A standard common rail system together with a single-hole nozzle was used for different fuel injection pressures. Further, an electronic injection system was used to carry out single and multiple injection by varying the injection timing. Impinged area, intensity, thickness and spray evolution were analyzed giving valuable information about the behavior of the liquid film. Considerable trends resulted from the variation of the parameters. In addition, limitations of both setups were discovered and a comparison between the two different laser sources was done. The current investigation is considered as a first step on a large investigation process. Future works could use the same setup described to address new targets: obtaining measurements of wall temperature, tests at conditions within higher air temperature and air pressure or comparisons between different fuels.
Teknisk mekanik , Energiteknik , Applied Mechanics , Energy Engineering