Optical sensor system for time-resolved quantification of methane densities in CH-fueled spark ignition engines.

We present the development and the first application of an optical sensor system that allows single-cycle determination of methane (CH) concentration inside internal combustion (IC) engines. We use non-dispersive infrared absorption spectroscopy to detect the CH density with a time resolution up to 33 μs at acquisition rates of 30 kHz. The measurement scheme takes advantage of the strong temperature dependence of the absorption band applying two detection channels for CH that detect different spectral regions of the ν anti-symmetric C-H-stretch absorption.