Journal cover Journal topic
Journal of Sensors and Sensor Systems An open-access peer-reviewed journal
J. Sens. Sens. Syst., 6, 185-198, 2017
https://doi.org/10.5194/jsss-6-185-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Regular research article
08 May 2017
Quantitative, time-resolved detection of CH4 concentrations in flows for injection analysis in CNG engines using IR absorption
Stephan Bauke1, Kai Golibrzuch1, Frank Rotter1, Hainer Wackerbarth1, Olaf Thiele2, and Thomas Berg2 1Laser-Laboratorium Göttingen e.V., Hans-Adolf-Krebs-Weg 1, 37077 Göttingen, Germany
2LaVision GmbH, Anna-Vandenhoeck-Ring 19, 37081 Göttingen, Germany
Abstract. The reduction of CO2 and other greenhouse gas emissions 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, i.e. non-dispersive IR absorption spectroscopy (NDIR). We demonstrate the capability of the system to achieve high time resolution as well as high measurement accuracy and precision. The optical set-up of the system is designed for usage at the inlet manifold of CNG-fuelled spark ignition engines. It allows for detailed analysis of the mixture formation during single engine cycles. CH4 densities can be determined by monitoring the infrared light attenuation around 3.3 µm caused by the ν3 anti-symmetric C–H-stretch vibration. We calculate the nonlinear relation between transmittance and CH4 density from absorption cross sections calculated from the HITRAN database. The theoretical transmittance signals are corrected for spectral influences of the bandpass filter, the detector sensitivity, the fibre transmittance and the emission spectrum of the light source in order to calculate CH4 densities directly from the measured transmittance. A calibration function corrects remaining differences between experimental and simulated values and improves the accuracy. We show that the sensor system is capable for determination of air–fuel ratios (λ-values) and demonstrate the dynamic quantification of a CH4 injection into a flow channel under various flow conditions. Furthermore, we present the first measurements with a prototype probe capable of measurements inside the inlet manifold of a four-stroke spark ignition engine. We validate the detection strategy in experiments with premixed gases using a modified inlet geometry and demonstrate its application under standard engine operation with port fuel injection while varying the injection parameters.

Citation: Bauke, S., Golibrzuch, K., Rotter, F., Wackerbarth, H., Thiele, O., and Berg, T.: Quantitative, time-resolved detection of CH4 concentrations in flows for injection analysis in CNG engines using IR absorption, J. Sens. Sens. Syst., 6, 185-198, https://doi.org/10.5194/jsss-6-185-2017, 2017.

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This work describes the development of an optical measurement system for accurate quantification of methane (the main component of compressed natural gas) densities in gas flows based on broadband absorption of infrared light. Using various test environments we validate accuracy and precision of the quantification method. We show that our measurement system can serve as a tool for the development of modern, CO2 saving internal combustion engines reducing environmental impact of transportation.
This work describes the development of an optical measurement system for accurate quantification...
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