Quasi-instantaneous Two-dimensional Temperature Measurements in a Spark Ignition Engine Using 2-line Atomic Fluorescence

Two-dimensional thermometry by the two-line atomic fluorescence method (TLAF) from atomic indium performed in an internal combustion engine is reported for the first time. The engine was a modified production engine running on iso-octane fuel. Small quantities of atomized indium were admitted to the engine chamber by injecting solutions containing InCl3 mixed with iso-octane. Temperatures could be measured over the entire combustion cycle covering a range from 800 to 2800 K at pressures up to 14 bar. A precision of 14% on single-shot temperature distributions was obtained, a figure that is expected to be much improved if laser intensity profile normalization is performed on a shot-by-shot basis and not, as in the present case, on averaged intensity profiles. Advantages of the technique are its sensitivity over a large temperature range, its insensitivity to collisional quenching processes, the small laser powers required, and the possibility to use wavelengths at which interferences from native flame species, such as small hydrocarbons, are low. Limitations are discussed, and comparisons with other techniques are made.