LIF to quantify in-cylinder fuel wall-films

What is it about?

Quantification of fuel-films inside of the combustion chamber has proven difficult so far.This paper describes improvements in the quantification procedure and presents an example application in a motored, optically accessible spark-ignition engine with direct injection.

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Why is it important?

To quantify fuel-films, it is important to calibrate the measurement accurately. This means also to consider high temperatures or high pressures, which could have an impact on the fluorescence intensity. Additionally the fluorescence intensity depends on the local intensity of the exciting laser light which is not uniform across the camera’s FOV on the probe. Calibration over the entire surface is necessary, but producing a µm-thin liquid film that is uniform over a large area is difficult. Therefore, for quantification we separate absolute thickness calibration from “flat-fielding”, i.e., correction of variations in local system response.