Analysis of the Fuel Liquid Film Thickness of a Port Fuel Injection Engine 2006-01-1051

In this paper, the authors have developed a new measuring method of the liquid fuel film thickness on walls, such as intake ports, the combustion chamber and cylinder liner of a Port Fuel Injection (PFI) engine, and clarified the fuel film behavior under various running conditions when Fiber-based Laser-Induced Fluorescence (Fiber-based LIF) was applied to the newly developed method. The thickness of the fuel film is measured by detecting the intensity of fluorescence from the film that is irradiated by a He-Cd laser. A single optical fiber is used to simultaneously transmit the laser beam and the fluorescence from the film. In addition, the S/N ratio of the fluorescence is improved by using a He-Cd laser of which the wavelength (λ=442nm) is able to efficiently irradiate test fuel doped 2-3-butandione.

Using this method, the fuel film thickness on the wall of the PFI engine was analyzed in two case studies. First, the formation process of the fuel film on the walls of the intake port, combustion chamber and cylinder liner were observed during cold starting. In this case study, the fuel film thickness of the intake port increased over 6 cycles after starting. And the fuel that adhered to the intake port flowed into the cylinder on the 3rd cycle of after starting. Secondly, the influence of running conditions such as engine speed, load, coolant temperature and valve overlap on the fuel film behavior were clarified under idling conditions at each crank angle.