Abstract
In this paper, the authors have developed a new measuring method of the liquid fuel film thickness on walls, such as intake ports, combustion chamber and cylinder liner of a Port Fuel Injection (PFI) engine, and clarified the fuel film behaviour during cold starting when Fiber-based Laser-Induced Fluorescence (Fiber-based LIF) was applied to the newly developed method. The thickness of the fuel film was measured by detecting the intensity of fluorescence from the film that was irradiated by a He-Cd laser. A single optical fiber was used to simultaneously transmit the laser beam and the fluorescence from the film. In addition, the S/N ratio of the fluorescence was improved by using a He-Cd laser of which the wavelength (=442nm) is able to efficiently irradiate test fuel doped 2-3-butandione. Using this method, we analysed the formation process of the fuel film thickness on the walls of PFI engine during cold starting (coolant temperature of 25 0C), and we clarified the influence of intake cam configuration at cold start upon the liquid fuel behaviours using two different intake cams. In this study, As for the cam where back flow occurs during the intake valve opening, a large amount of fuel film was adhered on the wall of intake port. For the cam where high velocity flow occurs in the cylinder direction, large amount of fuel film was adhered on the cylinder walls of exhaust side.
Keywords: Gasoline Engine, Laser Induced Fluorescence, Film Thickness, Cold Starting, Hydrocarbon