Fuel/Air-Ratio Measurements in Direct Injection Gasoline Sprays Using 1D Raman Scattering 2000-01-0244

One dimensional Spontaneous Raman Scattering measurements (RS) have been performed in a spray (standard gasoline, one-component and multi-component model fuels) which was operated in a high-temperature, high-pressure chamber, so that realistic engine conditions have been simulated. The present work investigates under what conditions 1D-RS can be employed for fuel/air-ratio measurements in realistic DI gasoline sprays. The distance from the spray axis has been determined, til that, coming from the outside, quantitative Raman measurement are possible. The equivalence ratio has been quantified for the one component fuel close to the spray. It turns out that the measurement error depends strongly on the type of fuel. These problems are caused by the PAH (polycyclic aromatic hydrocarbon) content of the fuel, which leads to interfering laser-induced fluorescence signals. The interferences are weak enough in both model fuels so that the fuel/air-ratio (Φ) can be measured at the edge of the spray for all studied conditions. In particular the width of the range around Φ=1 can be determined. In contrast, this range can not be accessed in the case of standard gasoline (Euro Super) due to strong LIF interferences. The fuel/air-ratio can only be determined in the lean regime of the Euro Super spray, i.e., far away from the spray cone or later in the spray pulse. A comparison between Raman and LIF radial intensities shows, that the fuel/air-ratio can not be determined from the LIF signal as well.