Experimental investigation of the excited radicals’ role in inhibiting the ignition of the hydrogen-oxygen mixtures

Authors: Korshunova M.R., Mikheeva E.Yu.
Published in issue: #9(26)/2018
DOI: 10.18698/2541-8009-2018-9-374
Category: Physics | Chapter: Chemical physics, combustion and explosion
Keywords: shock tube, inhibiting, hydrogen-oxygen mixtures, ignition, nonequilibrium radiation, electron-excited radicals, reflected shock wave, ignition delay
Published: 18.09.2018

The authors have carried out experimental investigation of the flame retarders’ influence on the nonequilibrium radiation of various radicals and molecules during the hydrogen ignition. We have conducted experiments with stoichiometrical hydrogen-oxygen mixture diluted with argon in the shock tube. The diagnostics of the ignition was performed within the temperature range 950…1400 K and the pressure range 2…6 mPa behind a reflected shock wave on registering the radical radiation OH* at wavelength 310 Nm and on pressure jump. Besides, we have conducted the registration of nonequilibrium radiation at wavelengths 220 and 411 Nm, which can supposedly correspond to electron-excited radicals and molecules OH*, H2O* and The experiments with the flame retarders additives (CO2, C2F4Br2, CCl4) show that the additives contribute to considerable radiation amplification, except for the case of adding CO2, when we did not find the difference in signals at wavelength 220 Nm compared to the pure mixture. The observed temperature dependences of the ignition delay time are compliant with the numerical kinetic modeling results. However, the result of the numerical modeling of the H2O2 HO2 and H2O concentrations’ temperature dependences conducted by means of modern kinetic mechanisms are not compliant with the experimental results, which requires further improvement of the kinetic schemes.

References

[1] Kathrotia T., Firki M., Bozkur M., Hartmann M., Riedel U., Schulz C. Study of the H+O+M reaction forming OH*: kinetics of OH* chemiliminescence in hydrogen combustion systems. Combustion and Flame, 2010, vol. 157, no. 7, pp. 1261–1273.

[2] Schefer R.W., Kulatilaka W.D., Patterson B.D., Settersten T.B. Visible emission of hydrogen flames. Combustion and Flame, 2009, vol. 156, no. 6, pp. 1234–1241.

[3] Fiala T. Radiotion from high-pressure hydrogen-oxygen flames and its use in assessing rocket combustion instability. Doktor – Ingenieurs genehmigten Dissertation. Technische Universität München, 2016, 152 p.

[4] Vanpee M., Mainiero R.J. The spectral distribution of the blue hydrogen flame continuum and its origin in hydrogen-nitric oxide flames. Combustion and Flame, 1979, vol. 34, pp. 219–230.

[5] Padley P.J. The origin of the blue continuum in the hydrogen flame. Transactions of the Faraday Society, 1960, vol. 56, pp. 449–454.

[6] Skrebkov O.V., Karkach S.P., Ivanova A.N., Kostenko S.S. Vibrational nonequilibrium of HO2 radical in the reaction of hydrogen with oxygen behind a weak shock wave. Fiziko-khimicheskaya kinetika v gazovoy dinamike [Physical-Chemical Kinetics in Gas Dynamics], 2008, vol. 6, pp. 1–21.

[7] Drakon A., Eremin A., Matveeva N., Mikheyeva E. The opposite influences of flame suppressants on the ignition of combustible mixtures behind shock waves. Combustion and Flame, 2017, vol. 176, pp. 592–598.

[8] Hong Z., Davidson D., Hanson R. An improved H2/O2 mechanism based on recent shock tube/laser absorption measurements. Combustion and Flame, 2011, vol. 158, no. 4, pp. 633–644.

[9] Bass M., Garvin D. Analysis of the hydroxil radical vibration rotation spectrum between 3900 A and 11500 A. Journal of Molecular Spectroscopy, 1962, vol. 9, pp. 114–123.

[10] Carloe C., Dalby F. Spectrum of the hydroxyl radical. Canadian Journal of Physics, 1969, vol. 47, no. 18, pp. 1945–1957.