2. Task 2
2.1

Study of Safety Measures

Research and Development Goals

The following items are planned for WE-NET, Task-2 (safety measures) program during thesecond phase of 1999 – 2003.
(1) to gather and arrange data concerning possible hazard consequences, the causes and theprobabilities at hydrogen facilities(2) to carry out experiments on leakage, ignition, diffusion and deflagration of hydrogen(3) to simulate the phenomena and to evaluate the magnitudes of possible hazards(4) to assess the hazard risks on presumed hydrogen refueling stations on the basis of theabove data(5) to draft a standard of hydrogen refueling stations with necessary safety measures,
mitigating the regulations on hydrogen storage volume and separation distance
restricting the sites of the stations

mitigation plan

experiments
probability

on hydrogenvolume andsimulation

separationassessment

magnitudes ofof hazard

combustion andrisks

explosion

drafting a standard
safetymeasureson hydrogen
refueling station

2.2 Results in Fiscal Year 2001
Hydrogen deflagration experiments with tube or semi-open equipment have been carried out
in the fiscal year 2001. Experiments spouting high pressure hydrogen through a pinhole andexamining ignition and flame characteristics have also begun. The activities are as thefollowings.
2.2.1

Safety Check of Hydrogen Refueling Stations

The working group of Task-2 has confirmed the taken safety measures for the hydrogen
refueling stations which Task-7 designed and constructed in Osaka and Takamatsu. The checklist and the advices will be used to improve the safety of the stations and will be utilized in-20-

making a technical guide of the stations.
2.2.2

Spouting Test
Test of High Pressure Hydrogen

We have installed the experiment equipment for spouting test of high pressure hydrogen andhave carried out the experiments. While the ideal gas is said to come out at the weight flow rate
proportional to the source pressure, much more hydrogen has actually come out especially at ahigher pressure than the proportional rate. It has been also proved that hydrogen effluence ishard to ignite without any igniter and that both the length and width of hydrogen flame areproportional to the diameter of a nozzle and also proportional to about 0.5 power of the sourcepressure. Radiation heat flux and temperatures have been measured. Examples of hydrogen
flame are shown in Figure 2.2.2-1.

（１ ＭＰａ）（１０ ＭＰａ）（１４ ＭＰａ）

Figure 2.2.22.2.2-１Flames from pressurized Hydrogen (visualized with a mist of NaCl aq.)（diameter of nozzle ：1 mmφmmφ,-21-

length of flame ：〜1.7：〜1.7 m）m）

2.2.3

Hydrogen Deflagration Experiments with Tube Type Equipment

We could not obtain a high signal / noise (S/N) ratio in ion current measurement to estimate theflame propagation velocity in hydrogen deflagration experiments carried out with a tube typeequipment last year. We could improve the S/N ratio drastically by adding a tiny amount ofmethane to hydrogen and by adopting new ion current probes that were made for ourselves inFY 2001. A series of tube experiments has been completed with obtaining useful data concerninghydrogen deflagration.
2.2.4

Hydrogen Deflagration Experiments with SemiSemi-open Type Equipment

We observed the maximum overpressures of 1.5 kPa from 30% hydrogen and 3.1 kPa from 57%
hydrogen at the range of 11 m from the gas mixture, under the condition of no obstacle and anelectric spark ignition with a semi-open deflagration equipment of 5.2 m３ gas volume. They
were much higher than the maximum overpressure of 0.18 kPa from 9.5% town gas deflagration,
the experiment result by JAERI, while they did not exceed the safety limit of 9.8 kPa
recommended in WE-NET safe design guideline. However, greater overpressure and flame
propagation velocity and partial deflagration to detonation transition have appeared when adense obstacle exists inside of hydrogen air mixture. Figure 2.2.4-1 shows the pictures of thedeflagration and the overpressure results are in Table 2.2.4-1.

-22-125
Figure 2.2.42.2.4-1

6

Hydrogen Deflagration with semisemi-open Equipment (test(test 22-01)
01)

-23-

Table2.2.4Table2.2.4- 1

Overpressures and Impulses of Hydrogen Deflagration

with SemiSemi-open Space Facility
Maximum Overpressure

Impulse(kPa)(Pa-s)

range from gas mixture (m)Test No.

Top ofBottom

Obstacle

End ofRemarks(range)
10m

20m

40m

11m

Tent
１66.0

41.5

9.09

4.32

1.62

16

H2 Conc. 20％

1-01

60.9

53.2

9.82

4.07

1.63

29

H2 Conc. 60％

2-01

3,270764

237.32.742

H2 Conc.30％

3-01

−

2.14

0.44

0.20

0.11

10

H2 Conc. 20％
No Obstacle

4-01

−

8.21

1.54

0.85

0.38

26

H2 Conc. 30％
No Obstacle

5-01−11.4

3.13

1.62

0.79

32

H2 Conc. 57％
No Obstacle

6-01

−

1,290

22.7

7.87

2.74

45

H2 Conc. 30％
No Obstacle
C4 Ignition(ref. *)

−

0.40

0.18

0.09

Town Gas

0.03〜4T.G. Conc. 9.5％
No Obstacle

Gas Mixture Volume : 5.2m３(ref. *) from experiment result of JARI program
2.2.5

Improvement of Simulation Codes

We have a prospect of clear way to fix parameters for analyzing hydrogen deflagration andhave analyzed and modeled this year’s experiment result on a computer preliminarily. We havealso examined a simulation model to evaluate the influence of presumed accidents, considering
the condition for combining CHAMPAGNE code, a simulator for hydrogen diffusion, andAutoReaGas code, a simulator for hydrogen deflagration. We could grasp the subjects to besolved for the simulation. A simulation model for the spillage and evaporation of liquid hydrogenhas been improved in the precision using the spillage experiment data of liquid hydrogen
carried out in FY 2000.
2.3

Subjects in the Future

As the results in FY 2001, we could obtain the data about the effect of hydrogen concentration,-24-