Experimental study of the spontaneous ignition of

partly confined hydrogen jets

Brian Maxwell, Patrick Tawagi, and Matei RadulescuDepartment of Mechanical Engineering

University of Ottawa

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

ID: 216

Diffusion-Ignition

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

Previous experiments[2-7] have shown that when pressurized H2 is suddenly released into air, spontaneous ignition of the jet can occur through shock induced diffusion-ignition.

2. Wolanski & Wojcicki (1973)3. Dryer et al. (2007)4. Golovastov et al. (2009)5. Mogi et al. (2009)6. Oleszczak & Wolanksi (2010)7. Lee et al. (2011)

Diffusion-IgnitionSeveral numerical investigations[8-16] have

identified this mechanism as responsible for generating localized combustion 'hot spots'.

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

Temperature (K) OHSource: Wen et al. (2009)

Confined ReleasesThe experiments [3-7] have only been able to

identify ignition limits for releases providing the H2 is first released through some partly confining tube.

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

Source: Mogi et al. (2009)

Confined ReleasesConfined releases are believed to be more likely to ignite

due to:Release in a tube prevents global expansion

(cooling) of the the gasLocal heating in the boundary layer of the tubeRichtmyer-Meshkov instability in the tube

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

Source: Dryer et al. (2007)

Objective

To examine the role of turbulent mixing on the jet and how it influences ignition

Experimental approach (which scales up the release to examine what happens inside a tube for example)

Results may also be useful for benchmarking future numerical studies

Preliminary Numerical investigation

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

Experimental Setup

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

Schlieren photography setup to capture flow-field evolution

Direct time resolved self-luminosity photographs to capture combustion

d=20mm or 67mm

Experimental Results

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

a) Schlieren photographof igniting jet.

b) Direct photograph capturing ignition.

c) Combustion at a later time...

Experimental Results

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

Ignition limit (shock in O2):

d=67mm, M=4.6+/-0.4d=20mm, M=5.1+/-0.3

Numerical Simulation

Numerical reconstruction of the flow-field (Video)

Perfect gasEuler Equations (Inviscid, non-reactive)

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

Numerical Simulation

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

Numerical Simulation

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

Ignition Limits

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

More details can be found in Maxwell B. M., and Radulescu M.I. (2011). Combustion and Flamedoi:10.1016/j.combustflame.2011.03.001(In press)

Ignition limits are estimated for unconfined release using a one dimensional model that follows the diffusion layer at the head of the jet as it is convected away from the release point.

Ignition Limits

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

Ignition Limits

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

Conclusions

Ignition limits of partially confined releases depend strongly on:

Strength of shock waveSize of release hole

Confinement does not have a major impact on whether or not local ignition spots will form on the jet surface.

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

Conclusions

RM and KH instabilities lead to increased turbulent mixing causing much more gas to be ignited than previously predicted by CFD.

Reflected shock waves play a major role influencing turbulent mixing (i.e. how ignition 'hot spots' interact leading to full jet ignition)

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

Acknowledgment

The present work was sponsored by– NSERC Discovery grant– NSERC Hydrogen Canada (H2CAN) Strategic

Research Network– Ontario Graduate Scholarship

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

References

International Conference on Hydrogen Safety September 12-14, 2011San Francisco, USA

1. Groethe M., Merilo E., Colton J., Chiba S., Sato Y., and Iwabuchi H. (2007) Int. J. Hydrogen Energy 32: 2125-2133.2. Wolanski P. and Wojcicki S. (1973). 14th Symp. (Int.) on Combustion, Pittsburg, PA 1217-1223.3. Dryer F. L., Chaos M., Zhao Z., Stein J. N., Alpert J. Y., and Homer C. J. (2007). Combust. Sci. Tech. 179: 663-694.4. Golovastov S. V., Baklanov D. I., Volodin V. V., Golub V. V., and Ivanov K. V. (2009). Russ. J. Phys. Chem. B 3 No. 3: 348-355.5. Mogi T., Wada Y., Ogata Y., and Hayashi A. K. (2009). Int. J. Hydrogen Energy 34: 5810-5816.6. Oleszczak P. and Wolanski P. (2010). Shock Waves 20:539-550.7. Lee H.J., Kim Y.R., Kim S.H., and Jeung I.S. (2011). Proceedings of the Combustion Institute 33: 2351-2358.8. Maxwell B. M., and Radulescu M.I. (2011). Combust. Flame doi: 10.1016/j.combustflame.2011.03.001 (In press)9. Liu Y. F., Tsuboi F. N., Sato H., Higashino F, and Hayashi A. K. (2005). 20th Intl Colloquium on the Dynamics of Explosions and Reactive Systems, Montreal, Canada.10. Liu Y. L., Zheng J. Y., Xu P., Zhao Y. Z., Bei H. Y., Chen H. G., and Dryver H. (2009). Journal of Loss Prevention in the Process Industries 22: 265-270.11. Xu B. P., Hima L. E. L., Wen J. X., and Tam V. H. Y. (2009). Int. J. Hydrogen Energy 34 No. 14: 5954-5960.12. Wen J. X., Xu B. P., and Tam V. H. Y. (2009). Combust. Flame 156: 2173-2189.13. Xu B. P., Hima L. E., Wen J. X., Dembele S., Tam V. H. Y., and Donchev T. (2008). Journal of Loss Prevention in the Process Industries 21: 205-213.14. Yamada E., Kitabayashi N., Hayashi A. K., and Tsuboi N. (2011). Int. J. Hydrogen Energy 36: 2560-2566.15. Lee B.J., and Jeung I. (2009). Int. J. Hydrogen Energy 34: 8763-8769.16. Bragin M.V., and Molkov V.V. (2011). Int. J. Hydrogen Energy 36: 2589-2596.