Fluorescence characteristics of the fuel tracer 1-methylnaphthalene for the investigation of equivalence ratio and temperature in an oxygen-containing environment

In this work, the fluorescence properties of the fuel tracer 1-methylnaphthalene (1-MN) are investigated in a calibration flow cell at elevated temperatures and pressures. This fuel tracer is well suited to investigate mixture formation in diesel engine applications, as 1-MN is a natural diesel fuel component. A tracer-LIF (laser-induced fluorescence) concept is developed that enables temperature measurements using a two-color approach in oxygen-containing gas mixtures. Furthermore, the potential for simultaneous measurement of equivalence ratio (fuel–air ratio, FAR) is evaluated. First, a picosecond Nd:YLF-laser at 263 nm in combination with a spectrograph and a streak unit was used to investigate the spectral fluorescence emission and fluorescence lifetimes. In addition, a nanosecond Nd:YAG-laser at 266 nm was used for fluorescence calibration with regard to equivalence ratio and temperature. All measurements were performed in an oxygen-containing environment at different equivalence ratios, temperatures up to 800 K and pressures up to 2.5 MPa. The dependency of the fluorescence emission on equivalence ratio was studied for varied fuel amount and air concentrations. The calibration data form the basis for investigations of fuel distribution and temperature under realistic engine conditions in an oxygen-containing environment.