Optical Measurments of Burning Velocities Under Engine-like Conditions for Methane and Hydrogen

Wittmann F, Clemente Mallada R, Rieß S, Wensing M (2025)

Publication Language: English

Publication Type: Conference contribution, Conference Contribution

Publication year: 2025

Book Volume: D8-4

Pages Range: 515 - 523

Conference Proceedings Title: PROCEEDINGS OF The 11th INTERNATIONAL CONFERENCE ON MODELING AND DIAGNOSTICS FOR ADVANCED ENGINE SYSTEMS

Event location: Chiba

Abstract

The laminar burning velocity (LBV) - dependent on fuel gas composition, temperature and pressure - is an important basis for the combustion velocity in internal combustion engines. In the current consideration of alternative fuels and combustion processes, process simulations are often based directly on LBV. The LBV value is usually measured with atmospheric laboratory burners or in combustion chambers with a constant volume - in any case an – at least approximately – stationary environment or clearly in the area of the laminar flow that gives the LBV its name. In engines, the turbulent charge motion has a considerable influence on the flame propagation speed, which typically reaches values of 10 times the LBV. The direct measurement of a representative combustion velocity in an engine is only possible with considerable effort. For this reason, a method is being developed for the optical measurement of the combustion velocity of homogeneously premixed fuel-air mixtures under engine conditions in a combustion chamber module. The flow of the fuel-air mixture introduces a flow into the combustion chamber module. The homogeneous mixture can be ignited by a spark plug or by an actively purged pre-chamber. This method allows burning velocity measurments under engine-like conditions and may be applied using existing combustion chamber, offering an adaptable approach for studying a variety
of fuels and increasingly complex combustion enviroments. The propagation of the flame front is recorded using a high-speed Schlieren-technique. The propagation speed of the flame front of premixed methane-air and hydrogen-air mixtures is investigated for a wide range of fuel-air mixtures. For the methane-air mixtures, the equivalence ratio λ is varied in a range from λ = 0.6 to 1.7. For hydrogen-air mixtures, the range from λ = 0.3 to 3.0 is investigated. The temperature of the fuel-air mixtures is changed from 423K to 523K and to 623K. The pressure and thus the density in the combustion chamber module are varied from 15 bar to 30 bar. As expected, the results show that the combustion rates are accelerated by higher temperatures. In addition to the faster reaction, the decreasing density with increasing temperature favors flame propagation. The dependence of the burning rate on density is analyzed using the measurements at the two pressure levels. Overall, the measured flame speeds are slower at higher pressure and therefore also higher density. The results on the influence of the equivalence ratio are compared with literature values on laminar burning velocity and conversion velocities in engines. The highest combustion rates for methane-air mixtures are achieved in the range around a stoichiometric mixture. For hydrogen-air mixtures, the highest measured combustion velocities are found for mixtures that are richer than the stoichiometric mixture. The engine-like burning rate (EL-BR) is a reference value that is easy to measure and can be correlated more easily to engine results.

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How to cite

APA:

Wittmann, F., Clemente Mallada, R., Rieß, S., & Wensing, M. (2025). Optical Measurments of Burning Velocities Under Engine-like Conditions for Methane and Hydrogen. In The Japan Society of Mechanical Engineers (JSME) (Eds.), PROCEEDINGS OF The 11th INTERNATIONAL CONFERENCE ON MODELING AND DIAGNOSTICS FOR ADVANCED ENGINE SYSTEMS (pp. 515 - 523). Chiba, JP.

MLA:

Wittmann, Frank, et al. "Optical Measurments of Burning Velocities Under Engine-like Conditions for Methane and Hydrogen." Proceedings of the The 11th International Conference on Modeling and Diagnostics for Advanced Engine Systems, Chiba Ed. The Japan Society of Mechanical Engineers (JSME), 2025. 515 - 523.

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