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HYDROGEN SUBSONIC UPWARD RELEASE and DISPERSION EXPERIMENTS

in CLOSED CYLINDRICAL VESSEL

HYDROGEN SUBSONIC UPWARD RELEASE and DISPERSION EXPERIMENTS

in CLOSED CYLINDRICAL VESSEL

Denisenko V.P.1, Kirillov I.A.1, Korobtsev S.V.1, Nikolaev I.I.1, Kuznetsov A.V.2, Feldstein V.A.3, Ustinov V.V.3

1 RRC”Kurchatov Institute” Kurchatov Sq., Moscow, 123182, Russia 2 NASTHOL 4, Shenogin str., Moscow, 123007, Russia3 TsNIIMash 4, Pionerskaya, Korolev, 141070, Russia

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ABSTRACTABSTRACT

Report presents the preliminary experimental results on hydrogen subsonic leakage in a

closed vessel under the well-controlled boundary/initial conditions.

Formation of hydrogen-air gas mixture cloud was studied for a transient (10 min),

upward hydrogen leakage, which was followed by subsequent evolution (15 min) of

explosive cloud. Low-intensity (0,46*10-3 m3/sec) hydrogen release was performed via

circular (diameter 0.014 m) orifice located in the bottom part of a horizontal cylindrical

vessel (about 4 m3). A spatially distributed net of the 24 hydrogen sensors and 24

temperature sensors was used to permanently track the time dependence of the

hydrogen concentration and temperature fields in vessel.

Analysis of the simultaneous experimental records for the different spatial points permits

to delineate the basic flow patterns and stages of hydrogen subsonic release in closed

vessel in contrast to hydrogen jet release in open environment. The quantitative data

were obtained for the averaged speeds of explosive cloud envelop (50% fraction of the

Lower Flammability Limit) propagation in the vertical and horizontal directions. The

obtained data will be used as an experimental basis for development of the guidelines

for an indoors allocation of the hydrogen sensors. Data can be also used as a new

benchmark case for the reactive Computational Fluid Dynamics codes validation.

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The general goal of our study is to create

an experimental database to be used in

ongoing development of the rational (non-

empiric) guidelines for a minimal number

and spatial allocation of the indoors

hydrogen sensors

PROJECT GOALPROJECT GOAL

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EXPERIMENTAL SYSTEM (VESSEL and SENSORS NET)

EXPERIMENTAL SYSTEM (VESSEL and SENSORS NET)

External (left) and internal (right) views of the experimental chamber

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Schematic draw of protective concrete dome (R = 6 m, h = 6 m, H = 12 m)

LOCATION of the EXPERIMENTAL VESSEL in the PROTECTIVE DOME

LOCATION of the EXPERIMENTAL VESSEL in the PROTECTIVE DOME

Air temperature inside the dome 23ºCRelative humidity 64 %

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SPATIAL ALLOCATION of the GAUGES (HYDROGEN SENSORS + THERMOCOUPLE) in the EXPERIMENTAL

VESSEL

SPATIAL ALLOCATION of the GAUGES (HYDROGEN SENSORS + THERMOCOUPLE) in the EXPERIMENTAL

VESSEL

The adjusting device for gauges allocation (to measure hydrogen concentration and temperature) consists of seven vertical metal rods with 0,006 m diameter, which allows to fix gauge position in rectangular coordinates: Y – along the horizontal chamber axis, X in the meridional cross-section of vessel

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SENSORS USED in the EXPERIMENTSSENSORS USED in the EXPERIMENTS

Thermal Conductivity Gauge TCG-3880for gas measurement (with open cap)by Xensor Integration (Netherlands)

Acoustic sensors with electronic scheme of data process and transmission by RRC ”Kurchatov Institute”

The accuracy of absolute concentration measurement is varying from 2 to 5%.

The relative measurement accuracy (resolution) of concentration measurements by calibrated sensors at stationary regimes (the absence of convective gas flows) was 0,03% vol.

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The main part of gas mixture

conditioning and transport system is

the gas mixture preparation device

(GMPD), which allows to mix

complex gas mixtures (up to 8

components) at the concentration

range for every component from 0 to

100% with the step of 1/256 and

relative accuracy 0,5%, and to

establish and control steady gas flow

rate from 5*10-6 to 7*10-4 m3/s

(from 20 to 2560 l/h).

The gas mixture from the gas mixture preparing device is supplied into experimental

chamber through pipe and is released into its internal space trough a letting device.

The letting device determines the regime of gas release (diffusion or jet-mixing) and

gas velocity at fixed gas flow rate.

EXPERIMENTAL SYSTEM (GAS CONTROL SYSTEM)

EXPERIMENTAL SYSTEM (GAS CONTROL SYSTEM)

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Formation of hydrogen-air gas mixture cloud was studied for a

transient (10 min), upward hydrogen leakage, which was

followed by subsequent evolution (15 min) of explosive cloud.

Low-intensity ( m3/sec) hydrogen release was performed via

circular (diameter 0.014 m) orifice located in the bottom part of

a horizontal cylindrical vessel (4 m3).

EXPERIMENTSEXPERIMENTS

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RESULTS of the EXPERIMENTSRESULTS of the EXPERIMENTS

Time histories for the hydrogen concentrations (% vol.) for the 24 gauges (time duration 0 - 25 min)

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RESULTS of the EXPERIMENTSRESULTS of the EXPERIMENTS

HYDROGEN CLOUD EXPANSION and PROPAGATION

1 min

5 min

10 min

10,05 min

15 min

25 min

hydrogen concentration in % vol.

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RESULTS of the EXPERIMENTSRESULTS of the EXPERIMENTS

Analysis of the time histories of hydrogen concentration at different spatial

points permits to delineate the following basic stages in formation and

evolution of hydrogen-air mixture cloud:

Step 1 – upward propagation of emerging jet,

Step 2 – impinging of jet with ceiling and outward expansion of cloud,

Step 3 – downward expansion of cloud from ceiling to floor.

The numerical data, received in the current and future test runs, can be

used as a basis for empirical correlation, which defines a time dependence

of volume of flammable cloud.

The basic flow patterns and stages of hydrogen subsonic release in closed vessel

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RESULTS of the EXPERIMENTSRESULTS of the EXPERIMENTS

Definition of the averaged speed of critical concentration front movement (between sensor 4 and sensor 21; time duration 0 - 0,5 min)

Averaged speed of critical concentration (2 % vol.) front propagation

For UNVENT 1 run, the numerical values of reactive cloud propagation in upward vertical direction is 0,33 m/sec, in horizontal direction (outward) -

0,055 m/sec.

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RESULTS of the EXPERIMENTS ( REPRODUCIBILITY )RESULTS of the EXPERIMENTS ( REPRODUCIBILITY )

Reproducibility of the time histories for the three different test runs (sensor 10).

For the points, where strong jet-sensors interaction was absent, the experimental data were coincident with the accuracy 0,2 % vol.

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RESULTS of the EXPERIMENTSRESULTS of the EXPERIMENTS

Coincident changes of hydrogen concentrations at points of sensors 18 and 24

The proof of symmetrical character of hydrogen flow in the experimental vessel

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The experimental set-up for investigating the processes of hydrogen release and mixing at atmospheric pressure in a medium-scale (4 m3), closed horizontal cylindrical vessel was prepared and adjusted.

The first accurate measurements (3 test runs) of the time evolution of explosive hydrogen cloud after hydrogen injection under the well-controlled boundary/initial conditions have been carried out with the help of 24 hydrogen sensors and 24 temperature sensors.

Analysis of the simultaneous experimental records for the different spatial points permits to delineate the basic flow patterns and stages of hydrogen subsonic release in closed vessel in contrast to hydrogen jet release in open environment. The quantitative data were obtained for the averaged speeds of explosive cloud envelop (50% fraction of the Lower Flammability Limit (LFL) – 2 vol.%) propagation in the vertical and horizontal directions.

CONCLUSIONSCONCLUSIONS

ACKNOWLEDGMENTS This work was supported by the grant (“Codes and Systems for Hydrogen Safety”) from the Russian Ministry of Science and Education and by the EU HYPER project (contract no. 039028).

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THANK YOU for YOUR ATTENTION ! THANK YOU for YOUR ATTENTION !