NIST GCR 09-927 Fire Safety Risks Associated With Leaks in Hydrogen Systems NIST GCR 09-927 Fire Safety Risks Associated With Leaks in Hydrogen Systems Prepared for National Institute of Standards and Technology Building and Fire Research Laboratory Gaithersburg, MD 20899-8202 By Peter B. Sunderland Department of Fire Protection Engineering University of Maryland College Park, MD 20742 Grant 60NANB5D1209 December 2009 U.S. DEPARTMENT OF COMMERCE Gary Locke, Secretary NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY Patrick D. Gallagher, Director Notice This report was prepared for the Building and Fire Research Laboratory of the National Institute of Standards and Technology under grant number 60NANB5D1209. The statements and conclusions contained in this report are those of the authors and do not necessarily reflect the views of the National Institute of Standards and Technology or the Building and Fire Research Laboratory. Final Report Fire Safety Risks Associated with Leaks in Hydrogen Systems Grant number: 60NANB5D1209 Grant PI: P.B. Sunderland Awarded by: National Institute of Standards and Technology Building and Fire Research Laboratory Gaithersburg, Maryland Submitted by: P.B. Sunderland Assistant Professor Department of Fire Protection Engineering University of Maryland [email protected] Submission date: November 18, 2009 Grant period: September 1, 2005 – August 31, 2009 Investigators: Peter B. Sunderland, University of Maryland (PI) Richard L. Axelbaum, Washington University (Co-I) Beei-Huan Chao, University of Hawaii (Co-I) NIST Contact: Jiann Yang 1 1. Motivation Hydrogen presents several unusual fire hazards, including high leak propensity, ease of ignition, and invisible flames. This research concerns experiments, analysis, and computations to identify the hazards of leaks in hydrogen systems that could result in combustion. The work seeks to identify the types of hydrogen leaks that can support flames. A small leak in a hydrogen system could ignite easily, support a flame that is difficult to detect, and lead to a catastrophic failure. 2. Objectives This research seeks an improved understanding of hydrogen fire safety that will lead to hazard reduction in hydrogen systems. Specific objectives include: 1. Measure limits of flaming (at ignition, quenching and blowoff) for hydrogen issuing from circular and slot burners of various sizes. 2. Measure flame quenching limits of hydrogen leaks in plumbing components. 3. Examine material degradation arising from an impinging hydrogen diffusion flame. 4. Prepare analytical and models of spontaneous ignition. 5. Perform CFD analyses of the flames to complement the experiments, yield additional physical insight, and allow the consideration of untested conditions. 3. Summary of Progress • The investigator team has published in Combustion Theory and Modeling a manuscript entitled A Theoretical Study of Spontaneous Ignition of Fuel Jets in an Oxidizing Ambient with Emphasis on Hydrogen Jets. This paper is attached here in Appendix A. • The investigator team has published in the International Journal of Hydrogen Energy a manuscript entitled Limits for Hydrogen Leaks that Can Support Stable Flames. This paper is attached here in Appendix A. • To date 15 papers and posters on this work have been published at conferences. • To date 17 oral presentations on this work have been presented. These have been in the U.S., Canada, U.K., and Germany. Six of these presentations have been by graduate students. • To date one Ph.D. Dissertation and four M.S. Theses have been published on this work. • An analysis was performed for the spontaneous ignition of a hydrogen (or other gaseous fuel) jet emanating from a slot into an oxidizing ambient (e.g., air). A similarity solution of the flow field was obtained. This was combined with the species and energy conservation equations, which were solved using activation energy asymptotics. Limits of spontaneous ignition were identified as functions of slot width, flowrate, and temperatures of the hydrogen jet and ambient gas. Two scenarios are examined: a cool jet flowing into a hot ambient and a hot jet flowing into a cool ambient. For both scenarios, ignition is favored with an increase of either the ambient temperature or the hydrogen supply temperature. Moreover, for the hot ambient scenario, a decrease in fuel Lewis number also promotes ignition. The Lewis number of the oxidizer only has a weak effect on ignition. Because spontaneous ignition is very sensitive to temperature, ignition is expected to occur near the edge of the jet if the hydrogen is cooler than the ambient gas and near the centerline if the hydrogen is hotter than the ambient gas. • Quenching and blowoff limits of hydrogen diffusion flames on small burners were observed. Four burner types, with diameters as small as 8 μm, were considered: pinhole burners, curved-wall burners, tube burners, and leaky fittings. In terms of mass flow rate, hydrogen 2 had a lower quenching limit and a higher blowoff limit than either methane or propane. Hydrogen flames at their quenching limits were the weakest flames recorded to date, with mass flow rates and heat release rates as low as 3.9 mg/s and 0.46 W. The quenching limit for a hydrogen flame at a 6 mm leaky compression fitting was found to be 28 mg/s. This limit was independent of supply pressure (up to 131 bar) and about an order of magnitude lower than the corresponding limits for methane and propane. • The quenching limit measurements from this project were incorporated into the new SAE J2579 standard for hydrogen vehicles. Hydrogen vehicles for U.S. use will now be required to demonstrate that localized leaks are smaller than our measured quenching limits. We have requested that a similar provision be added to the new NFPA 2, Hydrogen Technologies Code. • Flames with heat release rates as low as 0.25 W have been observed and photographed. These are believed to be the weakest flames ever observed. The work has applications to fire safety and microcombustors. • Materials degradation upon exposure to hydrogen diffusion flames has been observed. Hydrogen flames were observed to be more corrosive to metals and silicon carbide fibers than methane flames were. 4. Peer-Reviewed Journal Papers (see full text in Appendix A) 1. K.B. Lim, B.H. Chao, P.B. Sunderland, R.L. Axelbaum, A Theoretical Study of Spontaneous Ignition of Fuel Jets in an Oxidizing Ambient with Emphasis on Hydrogen Jets, Combustion Theory and Modeling, 12 (2008) 1179-1196. 2. M.S. Butler, C.W. Moran, P.B. Sunderland, R.L. Axelbaum, Limits for Hydrogen Leaks that Can Support Stable Flames, International Journal of Hydrogen Energy 34 (2009) 5174- 5182. 3. V.R. Lecoustre, C.W. Moran, P.B. Sunderland, B.H. Chao, R.L. Axelbaum, Experimental and Numerical Investigation of Extremely Weak Hydrogen Diffusion Flames, Combustion Symposium, in preparation. 5. Conference Proceedings and Posters 1. N.R. Morton, P.B. Sunderland, B.H. Chao, R.L. Axelbaum, Fire Hazards of Small Hydrogen Leaks, poster, Bridging the Transition…Hydrogen Internal Combustion Engines Symposium, weststart.org, San Diego (2006). 2. N.R. Morton, P.B. Sunderland, B.H. Chao, R.L. Axelbaum, Fire Safety Risks Associated with Leaks in Hydrogen Systems, poster, Annual Fire Conference, NIST, Gaithersburg (2006). 3. M.S. Butler, C.W. Moran, P.B. Sunderland, R.L. Axelbaum, Quenching Limits of Hydrogen Diffusion Flames, Eastern States Section of the Combustion Institute, Charlottesville (2007) 8 pp. 4. K.B. Lim, B.H. Chao, P.B. Sunderland, R.L. Axelbaum An Asymptotic Analysis of Spontaneous Ignition of Hydrogen Jets, 5th U.S. Combustion Meeting, San Diego, 11 pp. (2007). 5. N.R. Morton, P.B. Sunderland, B.H. Chao, R.L. Axelbaum, Fire Hazards of Small Hydrogen Leaks, SAE World Congress, Detroit, SAE Paper 2007-01-0429, 4 pp. (2007). 6. N.R. Morton, P.B. Sunderland, B.H. Chao, R.L. Axelbaum, Fire Hazards of Small Hydrogen Leaks, The National Hydrogen Association Annual Conference, San Antonio (2007) 8 pp. 3 7. N.R. Morton, P.B. Sunderland, B.H. Chao, R.L. Axelbaum, Quenching Limits and Materials Degradation of Hydrogen Diffusion Flames, 5th U.S. Combustion Meeting, San Diego, 8 pp. (2007). 8. M.S. Butler, R.L. Axelbaum, C.W. Moran, P.B. Sunderland, Flame Quenching Limits of Hydrogen Leaks, SAE World Congress, Detroit, SAE Paper 2008-01-0726 (2008) 8 pp. 9. M.S. Butler, C.W. Moran, P.B. Sunderland, R.L. Axelbaum, Fire Safety of Hydrogen Leaks, Second International Energy 2030 Conference, Abu Dhabi (2008) 10 pp. 10. M.S. Butler, C.W. Moran, P.B. Sunderland, R.L. Axelbaum, Fire Hazards of Small Leaks in Hydrogen Systems, Poster, International Association of Fire Safety Science, Karlsruhe (2008). 11. C.W. Moran, M.S. Butler, P.B. Sunderland, B.H. Chao, R.L. Axelbaum, Observations of Normal Gravity Flames that are Weaker than Microgravity Flame Balls, Poster, 32nd International Symposium on Combustion, Montreal (2008). 12. P.B. Sunderland, Fire Hazards of Small Hydrogen Leaks, 3rd European Summer School on Hydrogen Safety, Ulster (2008) 34 pp. 13. P.B. Sunderland, Pressure Relief Devices for Hydrogen Vehicles, 3rd European Summer School on Hydrogen Safety, Ulster (2008) 20 pp. 14. V.R. Lecoustre, C.W. Moran, P.B. Sunderland, B.H. Chao, R.L. Axelbaum, Experimental and Numerical Investigation of Extremely Weak Hydrogen Diffusion Flames, 6th U.S. National Combustion Meeting, Ann Arbor (2009) 12 pp. 15. P.B. Sunderland, American Perspectives and Regulations for Hydrogen Vehicles, Progress in Hydrogen Safety Short Course, Ulster (2009) 20 pp. 16. P.B. Sunderland, Hydrogen Flame Quenching Limits, Extinction, and Materials Degradation, Progress in Hydrogen Safety Short Course, Ulster (2009) 33 pp. 6. Oral Presentations 1. N.R. Morton, Quenching Limits and Materials Degradation of Hydrogen Diffusion Flames, 5th U.S. Combustion Meeting, San Diego, March 27, 2007. 2. K.B. Lim, An Asymptotic Analysis of Spontaneous Ignition of Hydrogen Jets, 5th U.S.