6.2.5 - Quantitative, time resolved detection of CH4 in flows using IR absorption

18. GMA/ITG-Fachtagung Sensoren und Messsysteme 2016
2016-05-10 - 2016-05-11
Nürnberg, Germany
6.2 Optische Gassensoren
S. Bauke, K. Golibrzuch, H. Wackerbarth - Laser-Laboratorium Göttingen e.V, Göttingen (Germany), O. Thiele, T. Berg - LaVision GmbH, Göttingen (Germany)
455 - 460


The reduction of emissions from CO2 and other greenhouse gases is an important driving force for the development of modern engines. Especially in the transport sector the use of alternative fuels like methane, the main component of compressed natural gas (CNG), is an applied measure to achieve this goal. This work describes the development of an optical measurement system for accurate quantification of CH4 densities in gas flows based on broadband absorption of infrared light. We demonstrate the capability for a 3 μs time resolution and a high measurement precision. The optical setup of the system is designed for usage at an inlet manifold of a spark ignition engine fueled with CNG. It allows for detailed analysis of the mixture formation during an engine cycle. CH4 density can be determined by monitoring the infrared light attenuation around 3.3 μm caused by the fundamental C-H-stretch vibration. We calculate the nonlinear relation between transmission and CH4 density from absorption cross sections taken from HITRAN database. The theoretical transmission signals are corrected for spectral influences of the bandpass filter and the detector sensitivity. A linear calibration function corrects remaining differences between experimental and simulated values. We show that the sensor system is capable for determination of the air-fuel-ratio (lambda value) and demonstrate the dynamic quantification of a CH4 injection into a flow channel under various flow conditions.