Stability Analysis of the Fluorescent Tracer 1-Methylnaphthalene for IC Engine Applications by Supercontinuum Laser Absorption Spectroscopy

1-methylnaphthalene (1-MN) is a widely used laser-induced fluorescence (LIF) tracer for planar imaging of mixture formation and temperature distributions in internal combustion (IC) engines. As the LIF measurement results can be biased by partial tracer oxidation, the conversion of 1-MN and the base fuel isooctane is analyzed in a calibration cell. First, measurements using supercontinuum laser absorption spectroscopy (SCLAS) are presented in order to quantify the conversion by detection of the produced H2O mole fraction. A single mode fiber (SMF) coupled setup is presented, with the fiber core acting as entrance slit of a Czerny-Turner spectrometer. Dependencies on residence time and global air-fuel ratio are presented at pressures up to 1.5 MPa and temperatures up to 900 K, at which distinct tracer and fuel consumption is observed. Signal loss due to intense beam steering was partially compensated using a self-stabilizing double-pass setup with a retroreflector

1-methylnaphthalene-LIF for the investigation of the mixture formation at diesel engine conditions and kHz repetition rates

This work presents the first high-speed tracer-LIF mixing study using 1-methylnaphthalene in a rapid compression machine (RCM). A burst-mode Nd:YAG-laser at 266 nm was used to excite the tracer at a frequency of 7.5 kHz. A high-speed intensified CMOS camera equipped with an image doubler was utilized for two-color-detection. Both homogenous conditions during compression and fuel injection at TDC (top dead center) were investigated. Measurements were conducted in nitrogen atmosphere at maximal pressures of 4.4 MPa