Optical Analysis of Ignition Sparks and Inflammation Using Background-Oriented Schlieren Technique

Moritz Grüninger (), Olaf Toedter and Thomas Koch
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Moritz Grüninger: Institute of Internal Combustion Engines (IFKM), Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
Olaf Toedter: Institute of Internal Combustion Engines (IFKM), Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
Thomas Koch: Institute of Internal Combustion Engines (IFKM), Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany

Energies, 2024, vol. 17, issue 6, 1-18

Abstract: To determine the timing of inflammation in gas and gasoline combustion engines, the point of 10% mass fraction conversion of fuel (MFB10) is commonly used. The MFB10 can be determined from the heating curve, which in turn is calculated from the in-cylinder pressure curve. However, the cylinder pressure is an indirect parameter with regard to inflammation, as it is the result of the combustion that follows the inflammation. An attempt is made to derive a new, direct parameter of inflammation based on optical measurements in order to detect inflammation more rapidly and accurately. The background-oriented Schlieren technique (BOS) in combination with high-magnification optics and a high-speed camera is used to detect local density changes coming from the particle wave around the ignition kernel of a hydrogen combustion inside a combustion chamber. Via BOS and regular high-magnification high-speed imaging, the influence of ignition coil dwell time and in-cylinder pressure on the spark phases and the inflammation itself are evaluated. As a potential direct parameter for inflammation, the size of the particle wave resulting from the expanding ignition kernel is evaluated. It was found that a higher coil energy supports a faster propagation of the particle wave at ambient pressure. At higher pressures, general combustion effects override the effect of the influence of the coil energy on the propagation speed of the particle wave. In addition, the presence of successful inflammation was found to influence the spark phases. A directly measurable parameter for ignition could be found at a basic level, which will serve as a starting point for further detailed investigations.

Keywords: ignition; inflammation; optical analysis; BOS; background-oriented Schlieren; hydrogen; high speed; spark ignition (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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