Exploring Nonlinear Flame Speed Inhibition Effects in Mixtures of R1234yf and R32

Published

June 6, 2024

Author(s)

Raik Hesse, Roman Glaznev, Raymond Langer, Christian Felix Schwenzer, Valeri Babushok, Gregory Linteris, Heinz Pitsch, Joachim Beeckmann

Abstract

This study investigates the flame speed inhibition effects in R1234yf and R32 mixtures, two hydrofluorocarbon (HFC) refrigerants with low global warming potential but mild flammability. The laminar flame speed (S0L,u) is a crucial parameter for assessing fire potential, and this research aims to provide high-fidelity flame speed data for refining chemical kinetic models. The slow flame propagation behavior of these refrigerants poses a formidable challenge to measurements due to buoyancy and radiation effects. This study simultaneously obtains S0L,u data using optical (Schlieren) and pressure-rise methods under microgravity conditions, allowing for comprehensive and accurate data acquisition. Initial conditions of 3 bar and 333K were used to mitigate contamination by stretch effects. Additionally, data for R1234yf were provided for extrapolation to standard conditions, enabling comparisons with literature data. Our results reveal substantial nonlinear blending effects on the laminar flame speed by introducing small fractions of R1234yf into R32 mixtures. While the selected kinetic model showed promising predictions, it could not fully predict the observed strong nonlinear flame speed decrease in experiments due to R1234yf addition. Chemical kinetic model analyses, including flux and sensitivity analyses, were employed to understand the blending interactions. The study highlights that the addition of R1234yf leads to the formation of HF, trapping radicals and inhibiting chain-branching reactions. Sensitivity analysis indicates that reactions involving fuel-specific intermediates (CHF2 for R32 and CF3 for R1234yf) play a key role. Specifically, CHF2 supplies H-atoms, while CF3 drains H-atoms. Hence, the introduction of R1234yf leads to a reduction in flame temperature, the creation of an extended post-flame zone, and a substantial decrease in S0L,u.

Citation

Proceedings of the Combustion Institute

Volume

40

Pub Type

Journals

Download Paper

https://doi.org/10.1016/j.proci.2024.105418

Local Download

Keywords

Laminar flame speed, Refrigerant flammability, R32, R1234yf, Microgravity

Citation

Hesse, R. , Glaznev, R. , Langer, R. , Schwenzer, C. , Babushok, V. , Linteris, G. , Pitsch, H. and Beeckmann, J. (2024), Exploring Nonlinear Flame Speed Inhibition Effects in Mixtures of R1234yf and R32, Proceedings of the Combustion Institute, [online], https://doi.org/10.1016/j.proci.2024.105418, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=957557 (Accessed September 25, 2025)