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Transient two-dimensional temperature distributions in the compression stroke and in the unburned end-gas of an SI engine were measured employing laser-induced fluorescence (LIF) of a fuel marker that possesses strongly temperature-dependent spectroscopic properties. The use of two different excitation wavelengths simplifies the otherwise complicated relation between LIF signal intensity and system parameters. The temperature fields obtained in this manner can be used to correct measured tracer-LIF maps and thus help to determine fuel distributions. Averaged temperature fields are compared to model calculations based on a homogeneous reactor assumption.

Various fluorescence tracers were assessed for their applicability for simultaneously measuring fuel distributions of different volatility classes. Tracers were chosen to show significantly different boiling behaviour representing three volatility classes of non-fluorescing multi-component fuels. Fluorescence properties of the markers were investigated using a heated static high-pressure cell with respect to emission behaviour, temperature and pressure dependence and quenching influences. A combination of ketonic and aromatic tracers appeared to be ideal for simultaneous imaging purposes since fluorescence is emitted in separate spectral regions with little overlap. Simultaneous measurements of the fuel distribution of two volatility classes were performed in a port fuel injected engine showing significant differences in the fuel distributions of low and mid boiling fractions in early stages of compression.