fundamentals of hydrogen safety engineering 2

Vladimir Molkov Fundamentals of Hydrogen Safety Engineering II Download free eBooks at bookboon.com Fundamentals of Hydrogen Safety Engineering II © 2012 Vladimir Molkov & bookboon.com (Ventus Publishing ApS) ISBN 978-87-403-0279-0 Download free eBooks at bookboon.com Fundamentals of Hydrogen Safety Engineering II Contents Contents Introduction Part I 1.1 Why hydrogen? Part I 1.2 Public perception of hydrogen technologies Part I 1.3 he importance of hydrogen safety Part I 1.4 Hazards, risk, safety Part I 1.5 Hydrogen safety communication Part I 1.6 he subject and scope of hydrogen safety engineering Part I 1.7 he emerging profession of hydrogen safety engineering Part I 1.8 Knowledge gaps and future progress Part I Hydrogen properties and hazards Part I 2.1 Physical and chemical properties Part I 2.2 Combustion properties Part I 2.3 Comparison with other fuels Part I 2.4 Health hazards Part I 2.5 Concluding remark Part I e Graduate Programme for Engineers and Geoscientists I joined MITAS because I wanted real responsibili Maersk.com/Mitas Real work International Internationa al opportunities work ree wo or placements Month 16 I was a construction supervisor in the North Sea advising and helping foremen he ssolve problems Download free eBooks at bookboon.com Click on the ad to read more Fundamentals of Hydrogen Safety Engineering II Contents Regulations, codes and standards and hydrogen safety engineering Part I Hydrogen safety engineering: framework and technical subsystems Part I 4.1 Framework Part I 4.2 Technical sub-systems Part I Unignited releases Part I 5.1 Expanded and under-expanded jets Part I 5.2 Under-expanded jet theories Part I 5.3 he similarity law for concentration decay in momentum-dominated jets Part I 5.4 Concentration decay in transitional and buoyancy-controlled jets Part I Dispersion of hydrogen in conined space Part I 6.1 Dispersion of permeated hydrogen in a garage Part I 6.2 he pressure peaking phenomenon Part I Ignition of hydrogen mixtures Part I 7.1 Overview of hydrogen ignition mechanisms Part I 7.2 Spontaneous ignition of sudden releases Part I Microlames Part I 8.1 Quenching and blow-of limits Part I www.job.oticon.dk Download free eBooks at bookboon.com Click on the ad to read more Fundamentals of Hydrogen Safety Engineering II Contents Jet ires Part I 9.1 Introduction to hydrogen jet ires and safety issues Part I 9.2 Chronological overview of hydrogen jet lame studies Part I 9.3 he drawback of Froude-based correlations Part I 9.4 he similitude analysis and a dimensional correlation Part I 9.5 he jet lame blow-of phenomenon Part I 9.6 he novel dimensionless lame length correlation Part I 9.7 Flame tip location and equivalent unignited jet concentration Part I 9.8 Separation distances from a hydrogen leak Part I 9.9 Efect of nozzle shape on lame length Part I 9.10 Efect of jet attachment of lame length Part I 9.11 Pressure efects of hydrogen jet ires Part I 9.12 Summary Part I 10 Delagrations 10 10.1 General features of delagrations and detonations 10 10.2 Some observations of DDT in hydrogen-air mixtures 13 10.3 Vented delagrations 15 10.4 Large eddy simulation (LES) of large-scale delagrations 54 Download free eBooks at bookboon.com Click on the ad to read more Fundamentals of Hydrogen Safety Engineering II Contents 11 Detonations 141 11.1 Direct initiation of detonation 141 11.2 LES of hydrogen-air detonations 141 12 Safety strategies and mitigation techniques 178 12.1 Inherently safer design of fuel cell systems 179 12.2 Mitigation of release consequences 180 12.3 Reduction of separation distances for high debit pipes 180 12.4 Mitigation by barriers 181 12.5 Mitigation of delagration-to-detonation transition (DDT) 181 12.6 Prevention of DDT within a fuel cell 182 12.7 Detection and hydrogen sensors 182 Concluding remarks 184 Acknowledgements 189 Appendix Glossary 190 References 193 Join the Vestas Graduate Programme Experience the Forces of Wind and kick-start your career As one of the world leaders in wind power solutions with wind turbine installations in over 65 countries and more than 20,000 employees globally, Vestas looks to accelerate innovation through the development of our employees’ skills and talents Our goal is to reduce CO2 emissions dramatically and ensure a sustainable world for future generations Read more about the Vestas Graduate Programme on vestas.com/jobs Application period will open March 2012 Download free eBooks at bookboon.com Click on the ad to read more Fundamentals of Hydrogen Safety Engineering II Disclaimer Author does not make any warranty or assumes any legal liability or responsibility for the accuracy, completeness, or any third party’s use of any information, product, procedure, or process disclosed, or represents that its use would not infringe privately owned rights Any electronic website link in this book is provided for user convenience and its publication does not constitute or imply its endorsement, recommendation, or favouring by the author Download free eBooks at bookboon.com he irst part of this book is available in "Fundamentals of Hydrogen Safety Engineering I" Download free eBooks at bookboon.com Fundamentals of Hydrogen Safety Engineering II Delagrations 10 Delagrations 10.1 General features of delagrations and detonations here are two types of “combustion explosions”, i.e delagrations and detonations here are other types of “explosions”, e.g “physical explosions” of vessels by overpressure above the established limit due to overill, as a result of runaway reaction, etc he word “explosion” is rather a jargon and we will avoid applying it in this book where possible Sometimes the use of term “explosion” could generate misunderstanding For example, some standards introduce wrongly from author’s point of view so-called “explosion limit” his is done in spite of the fact that there can be a signiicant diferent between the “lammability limit”, which is relevant for delagrations, and “detonability limit” (see further in this section) Let us overview the most general features of gaseous delagrations and detonations Delagration propagates with velocity below the speed of sound in the unburned mixture while detonation with velocity above the speed of sound Delagration front propagates by difusion of active radicals and heat from combustion products to unburned lammable mixture A detonation front is in principle diferent from a delagration front It is a complex of coupled leading shock and following the shock reaction zone as was for the irst time suggested by Chapman (1899) and Jouguet (1905–1906) he stoichiometric hydrogen-air mixture lame propagation velocity in the open quiescent atmosphere in a 20 m diameter hemispherical cloud is growing up to 84 m/s, and an explosion overpressure is of the order of 10 kPa in the near ield hen, pressure in a blast wave decays inversely proportional to radius, while for high explosives the pressure decays inversely proportional to radius squared he maximum delagration pressure to initial pressure ratio in a closed vessel is essentially higher and equals to 8.15 (BRHS, 2009) Detonation propagates faster than the speed of sound with the Chapman-Jouguet (CJ) velocity and the CJ pressure, which for stoichiometric hydrogen-air mixture are 1968 m/s and 1.56 MPa respectively (BRHS, 2009) Download free eBooks at bookboon.com 10 [...]... by Lee on dependence of detonation cell size on concentration of hydrogen in air (Lee, 19 82) Figure 1 02 Detonation cell size as a function of hydrogen concentration in air (Lee, 19 82) Download free eBooks at bookboon.com 12 Fundamentals of Hydrogen Safety Engineering II Delagrations 10 .2 Some observations of DDT in hydrogen- air mixtures Hydrogen is prone to the delagration-to-detonation transition... 01. 42. 77 .20 .66 www.HorizonsUniversity.org Download free eBooks at bookboon.com 11 Click on the ad to read more Fundamentals of Hydrogen Safety Engineering II Delagrations Figure 101 Schlieren photograph of the hydrodynamic structure of detonation (Radulescu et al., 20 05) he detonation cell size is a function of a mixture composition Figure 1 02 shows results of the classical work by Lee on dependence of. .. walls 3 m apart with height 3 m and length 12 m) and an enclosure (driver section) of sizes LxWxH=3.0x1.5x1.5 m (6.75 m3 volume) with an initially open to the lane vent of 0.82x0. 82 m he lane and the enclosure were illed with the same 22 .5% hydrogen- air mixture kept under a plastic ilm Venting of 22 .5% hydrogen- air delagration initiated at the rear wall of the enclosure by ive ignitors into the partially... limits of hydrogenair mixture of the same concentration expand with the scale of a lammable cloud his explains the diference between the lower detonability limit of hydrogen 11% by volume reported by Alcock et al (20 01) and the underestimated value of 18% published in standard ISO/TR 15916 :20 04 Experimental values of the detonation cell size for a stoichiometric hydrogen- air mixture are in the range 1. 12. 1.. .Fundamentals of Hydrogen Safety Engineering II Delagrations Detonation is the worst case scenario for hydrogen accident he detonability range of hydrogen in air 1159% by volume (Alcock et al., 20 01) is narrower and within the lammability range of 4-75% by volume It is worth noting that the detonability limits are not fundamental characteristics of the mixture as they strongly depend on the size of. .. Experiment 0 .2 0.1 0 2. 5 3-C Experiment Computed Experiment Computed Vent 100% Opened Vent Starts To Open 2 1.5 3-A 1 0 5 0 100 150 20 0 Time (ms) 25 0 300 350 0 100 20 0 300 400 Time (ms) Figure 106 Comparison with the experiment by Hửchst and Leuckel (1998) for translation panels: displacements (left); pressures (right) Download free eBooks at bookboon.com 31 500 600 Fundamentals of Hydrogen Safety Engineering. .. bookboon.com 29 Fundamentals of Hydrogen Safety Engineering II Delagrations he applicability of formula (10-31) is limited in the angle j of the door opening he formula will work only for the angles at which the current venting area F(j) is less than the nominal area FN At a certain angle jN such that F(jN )=FN the area of the low through the gap between the enclosure and the vent cover is equal to the area of. .. bookboon.com 19 Fundamentals of Hydrogen Safety Engineering II Delagrations A premixed lame propagates from the point of ignition throughout the mixture at conditions of changing in time temperature of unburnt mixture Tu(t) and pressure p(t) with burning velocity Su(Tu, p) he Mach number, S/cu, relating the lame velocity S and the speed of sound cu in the unburnt mixture, doesnt exceed the value of about... details of experiment 17A (Wilson, 1954) in the apparatus with free volume of 1. 72 m3 and a single spring-loaded valve, opening outwards horizontally, of the 0.46 m diameter are: 2% by 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0. 02 0.01 0 Experiment 17A Simulation Pressure, bar Displacement, m volume pentane-air mixture, 40.1 kg vent cover (24 4.5 kg/m2 surface density) 0 20 0 400 600 Time, ms 800 1,000 2 1.9... doors have reached 70o of opening Download free eBooks at bookboon.com 32 Fundamentals of Hydrogen Safety Engineering II Delagrations Figure 108 Comparison with hinged doors experiments 3-B, 3-D (à = 1 .2, o vent starts to open, vent 100% open): left - opening angles; right pressures For hinged vent covers, Ajet and Cjet were determined through matching of CINDY code predictions of experiments 3-B and ... stoichiometric hydrogen- air mixtures (Babkin, 20 03); and Su0 is the laminar burning velocity at 29 8 K 4.0 3.8 3.6 3.4 3 .2 3.0 2. 8 2. 6 2. 4 2. 2 2. 0 1.8 1.6 1.4 1 .2 1.0 0.8 0.6 0.4 0 .2 0.0 8.0 7.6 7 .2 6.8... of hydrogen safety Part I 1.4 Hazards, risk, safety Part I 1.5 Hydrogen safety communication Part I 1.6 he subject and scope of hydrogen safety engineering Part I 1.7 he emerging profession of. ..Vladimir Molkov Fundamentals of Hydrogen Safety Engineering II Download free eBooks at bookboon.com Fundamentals of Hydrogen Safety Engineering II â 20 12 Vladimir Molkov & bookboon.com